 Spatial distribution of mineralized bone matrix produced by marrow mesenchymal stem cells in self-assembling peptide hydrogel scaffold.
J Biomed Mater Res A. 2008 Jan;84(1):128-36.
Hamada K, Hirose M, Yamashita T, Ohgushi H.
Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology, 3-11-46 Nakoji, Amagasaki, Hyogo 661-0974, Japan.
We evaluated the osteogenic differentiation of mesenchymal stem cells (MSCs) using a new class of synthetic self-assembling peptide hydrogels, RADA 16, as a scaffold for three-dimensional culture. MSCs derived from rat bone marrow were culture-expanded and seeded into the hydrogel and further cultured in osteogenic medium containing beta-glycerophosphate, ascorbic acid, and dexamethasone for 2-4 weeks. High alkaline phosphatase activity and osteocalcin (OC) contents were detected at both the protein and gene expression levels during the culture periods. Both calcium and the OC contents increased over time, indicating the growth of a mineralized extracellular matrix within the hydrogel. Moreover, the process of the growth of the mineralized matrix determined by three-dimensional microarchitecture images was obtained by confocal laser scanning microscopy. The findings show that MSCs can differentiate into mature osteoblasts to form mineralized matrices within the hydrogel scaffold. Importantly, the differentiation can occur three dimensionally within the hydrogel, indicating that RADA 16 can be considered attractive synthetic biomaterial for use in bone tissue engineering.
Temperature and pH effects on biophysical and morphological properties of self-assembling peptide RADA16-I.
J Pept Sci. 2008 Jan 14;14(2):152-162 [Epub ahead of print]
Ye Z, Zhang H, Luo H, Wang S, Zhou Q, DU X, Tang C, Chen L, Liu J, Shi YK, Zhang EY, Ellis-Behnke R, Zhao X.
Institute for NanoBiomedical Technology and Membrane Biology, West China Hospital, Sichuan University, Science Park No 1, Ke Yuan 4th St., Gao Peng
Road, Hi-tech Industrial Development Zone, Chengdu, 610041, Sichuan, China.
It has been found that the self-assembling peptide RADA 16-I forms a
beta-sheet structure and self-assembles into nanofibers and scaffolds in
favor of cell growth, hemostasis and tissue-injury repair. But its
biophysical and morphological properties, especially for its beta-sheet and
self-assembling properties in heat- and pH-denatured conditions, remain
largely unclear. In order to better understand and design nanobiomaterials,
we studied the self-assembly behaviors of RADA16-I using CD and atomic force
microscopy (AFM) measurements in various pH and heat-denatured conditions.
Here, we report that the peptide, when exposed to pH 1.0 and 4.0, was still
able to assume a typical beta-sheet structure and self-assemble into long
nanofiber, although its beta-sheet content was dramatically decreased by 10%
in a pH 1.0 solution. However, the peptide, when exposed to pH 13.0,
drastically lost its beta-sheet structure and assembled into different
small-sized globular aggregates. Similarly, the peptide, when heat-denatured
from 25 to 70 degrees C, was still able to assume a typical beta-sheet
structure with 46% content, but self-assembled into small-sized globular
aggregates at much higher temperature. Titration experiments showed that the
peptide RADA16-I exists in three types of ionic species: acidic (fully
protonated peptide), zwitterionic (electrically neutral peptide carrying
partial positive and negative charges) and basic (fully deprotonated
peptide) species, called 'super ions'. The unordered structure and beta-turn
of these 'super ions' via hydrogen or ionic bonds, and heat Brownian motion
under the above denatured conditions would directly affect the stability of
the beta-sheet and nanofibers. These results help us in the design of future
nanobiomaterials, such as biosensors, based on beta-sheets and environmental
changes. These results also help understand the pathogenesis of the
beta-sheet-mediated neuronal diseases such as Alzheimer's disease and the
mechanism of hemostasis. Copyright (c) 2008 European Peptide Society and
John Wiley & Sons, Ltd.
Incorporation of a matrix metalloproteinase-sensitive substrate into self-assembling peptides - A model for biofunctional scaffolds.
Biomaterials. 2008 Jan 11 [Epub ahead of print]
Chau Y, Luo Y, Cheung AC, Nagai Y, Zhang S, Kobler JB, Zeitels SM, Langer R.
Department of Chemical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
Controlling and guiding cell behavior requires scaffolding materials
capable of programming the three-dimensional (3-D) extracellular
environment. In this study, we devised a new self-assembling peptide
template for synthesizing nanofibrous hydrogels containing cell-responsive
ligands. In particular, the insertion of a matrix metalloproteinase-2
(MMP-2) labile hexapeptide into the self-assembling building blocks of
arginine-alanine-aspartate-alanine (RADA) was investigated. A series of
peptides, varied by the position of the MMP-2 hexapeptide substrate and the
length of RADA blocks, were prepared by parallel synthesis. Their
self-assembling capabilities were characterized and compared by circular
dichroism spectroscopy and dynamical mechanical analysis. Among all the
different insertion patterns, the sequence comprising a centrically
positioned MMP-2 substrate was flanked with three RADA units on each side
self-assembled into a hydrogel matrix, with mechanical properties and
nanofiber morphology comparable to the native material built with (RADA)(4)
alone. Exposure of the new gel to MMP-2 resulted in peptide cleavage, as
confirmed by mass spectroscopy, and a decrease in surface hardness, as
detected by nanoindentor, indicating that the enzyme mediated degradation
was localized to the gel surface. The new design can be used for introducing
biological functions into self-assembling peptides to create scaffolding
materials with potential applications in areas such as tissue engineering
and regenerative medicine.
Self-assembling Peptide nanofiber scaffolds accelerate wound healing.
PLoS ONE. 2008 Jan 9;3(1):e1410.
Schneider A, Garlick JA, Egles C.
Division of Cancer Biology and Tissue Engineering, Department of Oral and Maxillofacial Pathology, Tufts University, School of Dental Medicine,
Boston, Massachusetts, United States of America.
Cutaneous wound repair regenerates skin integrity, but a chronic failure
to heal results in compromised tissue function and increased morbidity. To
address this, we have used an integrated approach, using nanobiotechnology
to augment the rate of wound reepithelialization by combining
self-assembling peptide (SAP) nanofiber scaffold and Epidermal Growth Factor
(EGF). This SAP bioscaffold was tested in a bioengineered Human Skin
Equivalent (HSE) tissue model that enabled wound reepithelialization to be
monitored in a tissue that recapitulates molecular and cellular mechanisms
of repair known to occur in human skin. We found that SAP underwent
molecular self-assembly to form unique 3D structures that stably covered the
surface of the wound, suggesting that this scaffold may serve as a viable
wound dressing. We measured the rates of release of EGF from the SAP
scaffold and determined that EGF was only released when the scaffold was in
direct contact with the HSE. By measuring the length of the epithelial
tongue during wound reepithelialization, we found that SAP scaffolds
containing EGF accelerated the rate of wound coverage by 5 fold when
compared to controls without scaffolds and by 3.5 fold when compared to the
scaffold without EGF. In conclusion, our experiments demonstrated that
biomaterials composed of a biofunctionalized peptidic scaffold have many
properties that are well-suited for the treatment of cutaneous wounds
including wound coverage, functionalization with bioactive molecules,
localized growth factor release and activation of wound repair.
Primary sequence of ionic self-assembling peptide gels affects endothelial cell adhesion and capillary morphogenesis.
J Biomed Mater Res A. 2008 Jan 9 [Epub ahead of print]
Sieminski AL, Semino CE, Gong H, Kamm RD.
Biological Engineering Division, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139.
Appropriate choice of biomaterial supports is critical for the study of
capillary morphogenesis in vitro as well as to support vascularization of
engineered tissues invivo. Self-assembling peptides are a class of
synthetic, ionic, oligopeptides that spontaneously assemble into gels with
an ECM-like microarchitecture when exposed to salt. In this paper, the
ability of four different self-assembling peptide gels to promote
endothelial cell adhesion and capillary morphogenesis is explored. Human
umbilical vein endothelial cells (HUVECs) were cultured within ionic
self-assembling peptide family members, RAD16-I ((RADA)(4)), RAD16-II
((RARADADA)(2)), KFE-8 ((FKFE)(2)), or KLD-12 ((KLDL)(3)). HUVECs suspended
in RAD16-I or RAD16-II gels elongated and formed interconnected
capillary-like networks resembling in vivo capillaries, while they remained
round and formed clusters within KFE-8 or KLD-12 gels. As HUVECs attach to
RAD16-I and RAD16-II significantly better than the other peptides, these
differences appear to be explained by differences in cell adhesion. Although
adhesion likely occurs via bound adhesion proteins, there appears to be no
difference in protein binding to the peptides investigated. Results indicate
that, although these oligopeptides have similar mechanisms of self-
assembly, their primary sequence can greatly affect cell adhesion.
Additionally, a subset of these biomimetic ECM-like materials support
capillary morphogenesis and thus may be useful for supporting
vascularization. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008.
Three-Dimensional Primary Hepatocyte Culture in Synthetic Self-Assembling Peptide Hydrogel.
Tissue Eng. 2008 Jan 3 [Epub ahead of print]
Wang S, Nagrath D, Chen PC, Berthiaume F, Yarmush ML.
Center for Engineering in Medicine, Massachusetts General Hospital,
Shriners Burn Hospital, and Harvard Medical School, Boston, Massachusetts.,
Present address: Biomedical Engineering Department, The City College of New
York, CUNY, New York, New York.
Drug metabolism studies and liver tissue engineering necessitate stable
hepatocyte cultures that express liver functions for a minimum of 4 days to
3 weeks. Current techniques, using different biomaterials and geometries,
that maintain hepatocellular function in vitro exhibit a low cell density
and functional capacity per unit volume. Herein we investigated a
well-defined synthetic peptide that can self-assemble into three-dimensional
interweaving nanofiber scaffolds to form a hydrogel, PuraMatrix, as a
substrate for hepatocyte culture. Freshly isolated primary rat hepatocytes
attached, migrated, and formed spheroids within 3 days after seeding on
PuraMatrix. Hepatocytes expressed the apical membrane marker dipeptidyl
peptidase IV at cell-cell contacts. Compared to the collagen sandwich,
albumin and urea secretion on PuraMatrix were higher for the first week, and
cytochrome P450IA1 activity was higher throughout the culture period.
Mitochondrial membrane potential 1 day after seeding was higher on
PuraMatrix than in the collagen sandwich, suggesting better preservation of
the metabolic machinery. PuraMatrix and Matrigel showed similar albumin and
urea production. PuraMatrix is an attractive system for generating
hepatocyte spheroids that quickly restore liver functions after seeding.
This system is also amenable to scale-up, which makes it suitable for in
vitro toxicity, hepatocyte transplantation, and bioartificial liver
development studies.
Compatibility of human fetal neural stem cells with hydrogel biomaterials in vitro.
Brain Res. 2008 Jan 2;1187:42-51. Epub 2007 Oct 26.
Thonhoff JR, Lou DI, Jordan PM, Zhao X, Wu P.
Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555-0620, USA.
Stroke and spinal cord or brain injury often result in cavity formation.
Stem cell transplantation in combination with tissue engineering has the
potential to fill such a cavity and replace lost neurons. Several hydrogels
containing unique features particularly suitable for the delicate nervous
system were tested by determining whether these materials were compatible
with fetal human neural stem cells (hNSCs) in terms of toxicity and ability
to support stem cell differentiation in vitro. The hydrogels examined were
pluronic F127 (PF127), Matrigel and PuraMatrix. We found that PF127, in a
gelated (30%) form, was toxic to hNSCs, and Matrigel, in a gelated (1-50%)
form, prevented hNSCs' normal capacity for neuronal differentiation. In
contrast, PuraMatrix was the most optimal hydrogel for hNSCs, since it
showed low toxicity when gelated (0.25%) and retained several crucial
properties of hNSCs, including migration and neuronal differentiation.
Further optimization and characterization of PuraMatrix is warranted to
explore its full potential in assisting neural regeneration in vivo.
Cartilage tissue engineering using human auricular chondrocytes embedded in different hydrogel materials.
J Biomed Mater Res A. 2006 Jul;78(1):1-11.
Yamaoka H, Asato H, Ogasawara T, Nishizawa S, Takahashi T, Nakatsuka T, Koshima I, Nakamura K, Kawaguchi H, Chung UI, Takato T, Hoshi K.
Department of Fujisoft ABC Cartilage and Bone Regeneration, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-Ku, Tokyo 113-0033, Japan.
To seek a suitable scaffold for cartilage tissue engineering, we compared various hydrogel materials originating from animals, plants, or synthetic peptides. Human auricular chondrocytes were embedded in atelopeptide collagen, alginate, or PuraMatrix, all of which are or will soon be clinically available. The chondrocytes in the atelopeptide collagen proliferated well, while the others showed no proliferation. A high-cell density culture within each hydrogel enhanced the expression of collagen type II mRNA, when compared with that without hydrogel. By stimulation with insulin and BMP-2, collagen type II and glycosaminoglycan were significantly accumulated within all hydrogels. Chondrocytes in the atelopeptide collagen showed high expression of beta1 integrin, seemingly promoting cell-matrix signaling. The N-cadherin expression was inhibited in the alginate, implying that decrease in cell-to-cell contacts may maintain chondrocyte activity. The matrix synthesis in PuraMatrix was less than that in others, while its Young's modulus was the lowest, suggesting a weakness in gelling ability and storage of cells and matrices. Considering biological effects and clinical availability, atelopeptide collagen may be accessible for clinical use. However, because synthetic peptides can control the risk of disease transmission and immunoreactivities, some improvement in gelling ability would provide a more useful hydrogel for ideal cartilage regeneration.
Self-assembling peptide nanofiber as a novel culture system for isolated porcine hepatocytes.
Cell Transplant. 2006;15(10):921-7.
Navarro-Alvarez N, Soto-Gutierrez A, Rivas-Carrillo JD, Chen Y, Yamamoto T, Yuasa T, Misawa H, Takei J, Tanaka N, Kobayashi N.
Department of Surgery, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan.
Freshly isolated porcine hepatocytes are a very attractive cell source in the cell-based therapies to treat liver failure because of unlimited availability. However, due to the loss of hepatocyte functions in vitro, there is a need to develop a functional culture system to keep the cells metabolically active. Here we compared the effect of a self-assembling peptide nanofiber (SAPNF) as an extracellular matrix (ECM) with collagen type I on hepatocyte metabolic and secretion activities following hepatocyte isolation. Isolated porcine hepatocytes were cultured in SAPNF and collagen type I. Morphological assessment at different time points was performed by using SEM and phase contrast microscope. Metabolic and secretion activities were comparatively performed in the groups, by means of ammonia, lidocaine, and diazepam as well as albumin. Hepatocytes cultured on SAPNF revealed a three-dimensional spheroidal formation, thus maintaining cell differentiation status during 2 weeks of culture. On the other hand, hepatocytes in collagen revealed a spread shape, and by day 14 no hepatocyte-like cells were observed, but cells with long shape were present, thus revealing a degree of dedifferentiation in collagen culture. Hepatocytes in SAPNF were capable of drug-metabolizing activities and albumin secretion in higher ratio than those cultured on collagen. The present work clearly demonstrates the usefulness of SAPNF for maintaining differentiated functions of porcine hepatocytes in culture.
PuraMatrix facilitates bone regeneration in bone defects of calvaria in mice.
Cell Transplant. 2006;15(10):903-10.
Misawa H, Kobayashi N, Soto-Gutierrez A, Chen Y, Yoshida A, Rivas-Carrillo JD, Navarro-Alvarez N, Tanaka K, Miki A, Takei J, Ueda T, Tanaka M, Endo H, Tanaka N, Ozaki T.
Department of Orthopeadic Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan.
Artificial bones have often used for bone regeneration due to their strength, but they cannot provide an adequate environment for cell penetration and settlement. We therefore attempted to explore various materials that may allow the cells to penetrate and engraft in bone defects. PuraMatrix is a self-assembling peptide scaffold that produces a nanoscale environment allowing both cellular penetration and engraftment. The objective of this study was to investigate the effect of PuraMatrix on bone regeneration in a mouse bone defect model of the calvaria. Matrigel was used as a control. The expression of bone-related genes (alkaline phosphatase, Runx2, and Osterix) in the PuraMatrix-injected bone defects was stronger than that in the Matrigel-injected defects. Soft X-ray radiographs revealed that bony bridges were clearly observed in the defects treated with PuraMatrix, but not in the Matrigel-treated defects. Notably, PuraMatrix treatment induced mature bone tissue while showing cortical bone medullary cavities. The area of newly formed bones at the site of the bone defects was 1.38-fold larger for PuraMatrix than Matrigel. The strength of the regenerated bone was 1.72-fold higher for PuraMatrix (146.0 g) than for Matrigel (84.7 g). The present study demonstrated that PuraMatrix injection favorably induced functional bone regeneration.
The Use of 3-D Culture in Peptide Hydrogel for Analysis of Discoidin Domain Receptor 1-Collagen Interaction.
Cell Adhesion & Migration 2006; Col. 1 (2) 92-98.
Daizo Yoshida and Akira Teramoto.
Department of Neurosurgery, Nippon Medical School; Nippon Medical School, Tokyo, Japan.
The aim of this study is to examine a novel drop culture model using a biologically inspired self-assembling peptide: hydrogel (RAD16-I, also called PuraMatrix), which produces a nanoscale environment similar to native extracellular matrix (ECM) for a cell line weakly adherent to a plastic surface during cell culture. Our work investigates quantitatively analyzing discoidin domain receptor (DDR) 1-mediated protein interactions between collagen type I and matrix metalloproteinase (MMP)-2 or -9, as well as cell invasion, using, as a scaffold, PuraMatrix, a novel peptide hydrogel. Results demonstrate that the dynamic cell culture technique produced a highly stable reharvesting of cells throughout the constructs with HP-75, human pituitary adenoma cell line when compared to the traditional seeding methods. Secretion of MMP via collagen type I was observed quantitatively in the supernatant (EC50; MMP-2, 50.4 ng/ml: MMP-9, 57.6 ng/ml). In PuraMatrix gel impregnated with 50 ng/ml of collagen type I, transfection of the vector encoding full-length DDR1 or siRNA targeting DDR1 up- or down-regulated respectively secretion of MMP-2 and -9, and cell invasion. Our results show that incorporation of this peptide with each ECM component provides a more permissive environment to elucidate ECM to cell signal interaction.
Controlled delivery of PDGF-BB for myocardial protection using injectable self-assembling peptide nanofibers.
J Clin Invest. 2006 Jan;116(1):237-48. Epub 2005 Dec 15.
Hsieh PC, Davis ME, Gannon J, MacGillivray C, Lee RT.
Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Endothelial cells can protect cardiomyocytes from injury, but the mechanism of this protection is incompletely described. Here we demonstrate that protection of cardiomyocytes by endothelial cells occurs through PDGF-BB signaling. PDGF-BB induced cardiomyocyte Akt phosphorylation in a time- and dose-dependent manner and prevented apoptosis via PI3K/Akt signaling. Using injectable self-assembling peptide nanofibers, which bound PDGF-BB in vitro, sustained delivery of PDGF-BB to the myocardium at the injected sites for 14 days was achieved. A blinded and randomized study in 96 rats showed that injecting nanofibers with PDGF-BB, but not nanofibers or PDGF-BB alone, decreased cardiomyocyte death and preserved systolic function after myocardial infarction. A separate blinded and randomized study in 52 rats showed that PDGF-BB delivered with nanofibers decreased infarct size after ischemia/reperfusion. PDGF-BB with nanofibers induced PDGFR-beta and Akt phosphorylation in cardiomyocytes in vivo. These data demonstrate that endothelial cells protect cardiomyocytes via PDGF-BB signaling and that this in vitro finding can be translated into an effective in vivo method of protecting myocardium after infarction. Furthermore, this study shows that injectable nanofibers allow precise and sustained delivery of proteins to the myocardium with potential therapeutic benefits.
Nano neuro knitting: peptide nanofiber scaffold for brain repair and axon regeneration with functional return of vision.
Proc Natl Acad Sci U S A. 2006 Mar 28;103(13):5054-9. Epub 2006 Mar 20.
Ellis-Behnke RG, Liang YX, You SW, Tay DK, Zhang S, So KF, Schneider GE.
Department of Brain and Cognitive Science, Massachusetts Institute of Technology, 77 Massachusett Avenue, Cambridge, MA 02139-4307, USA.
Nanotechnology is often associated with materials fabrication, microelectronics, and microfluidics. Until now, the use of nanotechnology and molecular self assembly in biomedicine to repair injured brain structures has not been explored. To achieve axonal regeneration after injury in the CNS, several formidable barriers must be overcome, such as scar tissue formation after tissue injury, gaps in nervous tissue formed during phagocytosis of dying cells after injury, and the failure of many adult neurons to initiate axonal extension. Using the mammalian visual system as a model, we report that a designed self-assembling peptide nanofiber scaffold creates a permissive environment for axons not only to regenerate through the site of an acute injury but also to knit the brain tissue together. In experiments using a severed optic tract in the hamster, we show that regenerated axons reconnect to target tissues with sufficient density to promote functional return of vision, as evidenced by visually elicited orienting behavior. The peptide nanofiber scaffold not only represents a previously undiscovered nanobiomedical technology for tissue repair and restoration but also raises the possibility of effective treatment of CNS and other tissue or organ trauma.
Controlled delivery of PDGF-BB for myocardial protection using injectable self-assembling peptide nanofibers.
J Clin Invest. 2006 Jan;116(1):237-48. Epub 2005 Dec 15.
Hsieh PC, Davis ME, Gannon J, MacGillivray C, Lee RT.
Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Endothelial cells can protect cardiomyocytes from injury, but the mechanism of this protection is incompletely described. Here we demonstrate that protection of cardiomyocytes by endothelial cells occurs through PDGF-BB signaling. PDGF-BB induced cardiomyocyte Akt phosphorylation in a time- and dose-dependent manner and prevented apoptosis via PI3K/Akt signaling. Using injectable self-assembling peptide nanofibers, which bound PDGF-BB in vitro, sustained delivery of PDGF-BB to the myocardium at the injected sites for 14 days was achieved. A blinded and randomized study in 96 rats showed that injecting nanofibers with PDGF-BB, but not nanofibers or PDGF-BB alone, decreased cardiomyocyte death and preserved systolic function after myocardial infarction. A separate blinded and randomized study in 52 rats showed that PDGF-BB delivered with nanofibers decreased infarct size after ischemia/reperfusion. PDGF-BB with nanofibers induced PDGFR-beta and Akt phosphorylation in cardiomyocytes in vivo. These data demonstrate that endothelial cells protect cardiomyocytes via PDGF-BB signaling and that this in vitro finding can be translated into an effective in vivo method of protecting myocardium after infarction. Furthermore, this study shows that injectable nanofibers allow precise and sustained delivery of proteins to the myocardium with potential therapeutic benefits.
Overexpression of the Epidermal Growth Factor Receptor
Confers Migratory Properties to Nonmigratory Postnatal
Neural Progenitors
The Journal of Neuroscience, November 30, 2005 ・25(48):11092・1106
Adan Aguirre (1), Tilat A. Rizvi (2), Nancy Ratner (2), and Vittorio Gallo (1)
(1) Center for Neuroscience Research, Children痴 Research Institute, Children痴 National Medical Center, Washington, DC 20010, and
(2) Division of
Experimental Hematology, Department of Pediatrics, Cincinnati Children痴 Hospital Research Foundation, University of Cincinnati College of Medicine,
Cincinnati, Ohio 45229
Approaches to successful cell transplantation therapies for the injured brain involve selecting the appropriate neural progenitor type and
optimizing the efficiency of the cell engraftment. Here we show that epidermal growth factor receptor (EGFR) expression enhances
postnatal neural progenitor migration in vitro and in vivo. Migratory NG2-expressing (NG2) progenitor cells of the postnatal subventricular
zone (SVZ) express higher EGFR levels than nonmigratory, cortical NG2cells. The higher endogenous EGFR expression in SVZ
NG2 cells is causally related with their migratory potential in vitro as well as in vivo after cell engraftment. EGFR overexpression in
cortical NG2 cells by transient transfection converted these cells to a migratory phenotype in vitro and in vivo. Finally, cortical NG2
cells purified from a transgenic mouse in which the EGFR is overexpressed under the CNP promoter exhibited enhanced migratory
capability. These findings reveal a new role for EGFR in the postnatal brain and open new avenues to optimize cell engraftment for brain
repair.
Key words: CNP-EGFP mouse; cell transplantation; cell migration; rostral migratory stream; white matter; hippocampus; olfactory bulb
The enhancement of osteoblast growth and differentiation in vitro on a peptide hydrogel-polyHIPE polymer hybrid material
Biomaterials 2005 Sep; 26(25):5198-208
Bokhari MA, Akay G, Zhang S, Birch MA.
School of Chemical Engineering and Advanced Materials, University of Newcastle, Newcastle upon Tyne, NE1 7RU, UK.
The objective of this study was to investigate the effect of combining two biomaterials on osteoblast proliferation, differentiation and mineralised matrix formation in vitro. The first biomaterial has a well-defined architecture and is known as PolyHIPE polymer (PHP). The second biomaterial is a biologically inspired self-assembling peptide hydrogel (RAD16-I, also called PuraMatrix) that produces a nanoscale environment similar to native extracellular matrix (ECM). Our work investigates the effect of combining RAD16-I with two types of PHP (HA (Hydroxyapatite)-PHP and H (Hydrophobic)-PHP) and evaluates effects on osteoblast growth and differentiation. Results demonstrated successful incorporation of RAD16-I into both types of PHP. Osteoblasts were observed to form multicellular layers on the combined biomaterial surface and also within the scaffold. Dynamic cell seeding and culturing techniques were compared to static seeding methods and produced a more even distribution of cells throughout the constructs. Cells were found to penetrate the scaffold to a maximum depth of 3 mm after 35 days in culture. There was a significant increase in cell number in H-PHP constructs coated with RAD16-I compared to H-PHP alone. Our results show that RAD16-I enhances osteoblast differentiation and indicates that the incorporation of this peptide provides a more permissive environment for osteoblast growth. We have developed a microcellular polymer containing a nanoscale environment to enhance cell: biomaterial interactions and promote osteoblast growth in vitro.
The
effect of functionalized self-assembling peptide scaffolds on human aortic
endothelial cell function
Biomaterials 26
(2005) 3341–3351
Elsa Genové (a),
Colette Shen (b), Shuguang Zhang (a,c), Carlos E. Semino (a,c)
(a) Center
for Biomedical Engineering, Massachusetts Institute of Technology,
77 Massachusetts Avenue, Cambridge, MA 02139, USA
(b) Harvard
University, Cambridge, MA, 02138, USA
(c) Biotechnology Process Engineering
Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Abstract
A class of designed self-assembling peptide
nano.ber scaffolds with more than 99% water content has been shown to
be a goodbiological material for cell
culture. Here, we report the functionalization of one of these peptide
scaffolds, by direct solid phase synthesis extension at the amino terminal
with three shortsequencemotifs. These motifs
are present in two major protein components of the basement membrane,
laminin 1 (YIGSR, RYVVLPR) and collagen IV (TAGSCLRKFSTM). These motifs
have been previously shown to promote speci.c biological activities including
endothelial cell adhesion, spreading, and tubular formation. Therefore,
the generic functionalized peptide developed was AcN–X–GG-RAD16–CONH2 with each motif represented
by ‘‘X’’. We show in this work that these tailor-made
peptide scaffolds enhance the formation of con.uent cell monolayers of
human aortic endothelial cells (HAEC) in culture. Moreover, additional
assays designed to evaluate endothelial cell function showed that HAEC
monolayers obtained on these scaffolds not only maintained LDL uptake
activity but also enhanced nitric oxide release and elevated laminin
1 and collagen IV deposition. These results suggest that this new scaffold
provide a better physiological substrate for endothelial cell culture
and suggest its further application for biomedical research, cancer biology
and regenerative biology.
Keywords: Self-assembly; Biomimetic
material; Cell proliferation; Extracellular matrix; Endotheliar monolayer
Self-assembling
short oligopeptides and the promotion of angiogenesis
Biomaterials 26 (2005) 4837–4846
Daria A. Narmoneva (a, b), Olumuyiwa Oni (b), Alisha L. Sieminski
(b), Shugang Zhang (b), Jonathan P. Gertler (c), Roger D. Kamm (b), Richard
T. Lee (a,b)
(a) Cardiovascular Division, Brigham and Women’s Hospital & Harvard
Medical School, Boston, MA 02139, USA
(b) Division of Biological Engineering, Massachusetts Institute of Technology,
Cambridge, MA 02139, USA
(c) Vascular Surgery Research Laboratory, Division of Vascular Surgery, Massachusetts
General Hospital and Harvard Medical School, Boston, MA 02114, USA
Abstract
Because an adequate blood supply to and within tissues is an essential factor
for successful tissue regeneration, promoting a functional microvasculature
is a crucial factor for biomaterials. In this study, we demonstrate that
short self-assembling peptides form scaffolds that provide an angiogenic
environment promoting long-term cell survival and capillary-like network
formation in three-dimensional cultures of human microvascular endothelial
cells. Our data show that, in contrast to collagen type I, the peptide scaffold
inhibits endothelial cell apoptosis in the absence of added angiogenic factors,
accompanied by enhanced gene expression of the angiogenic factor VEGF. In
addition, our results suggest that the process of capillary-like network
formation and the size and spatial organization of cell networks may be controlled
through manipulation of the scaffold properties, with a more rigid scaffold
promoting extended structures with a larger inter-structure distance, as
compared with more dense structures of smaller size observed in a more compliant
scaffold. These .ndings indicate that self-assembling peptide scaffolds have
potential for engineering vascularized tissues with control over angiogenic
processes. Since these peptides can be modi.ed in many ways, they may be
uniquely valuable in regeneration of vascularized tissues.
Keywords: Angiogenesis; Endothelial cell; Peptide; Scaffold;
Myocardial regeneration
ENHANCED
CHONDROGENESIS AND DEVELOPMENT OF MECHANICAL PROPERTIES OF HUMAN MESENCHYMAL
STEM CELLS SEEDED IN A SELF-ASSEMBLING PEPTIDE HYDROGEL
Mauck RL, Helm JM, Tuan RS
Cartilage
Biology and Orthopaedics Branch, National Institute of Arthritis and Musculoskeletal
and Skin Disorders, National Institutes of Health, Bethesda, MD 20892
The goals of the present study were to first determine if
chondrogenic differentiation of human MSCs was possible in a self-assembling
peptide hydrogel (Puramatrix, (REDA)4, 3DM, Inc.), secondly to compare
the level of chondrogenic differentiation that occurs in this hydrogel
to that which occurs under standard pellet culture, and thirdly to determine
if chondrogenesis within this matrix will lead to the production of functional
mechanical properties with long term culture.
Preliminary studies using three separate human donor MSCs
embedded in Puramatrix demonstrated a pronounced chondrogenic differentiation
after 21 days in the presence of TGF-â3 (Figure 1). Beads became
increasingly opaque and palpably stiffer over the duration of the experiment
with pronounced induction of chondrogenic mRNA transcripts (Figure 1).
Histology showed an even distribution of cells throughout the bead and
abundant proteoglycan and collagen deposition (Figure 2). In subsequent
studies with four additional human donor MSCs, comparison of mRNA transcript
levels using real time PCR demonstrated a marked upregulation of aggrecan
and type II collagen transcript levels with the addition of TGF-â3
in both traditional cell pellet culture and in Puramatrix beads (Figure
3). Interestingly, aggrecan transcript levels in Puramatrix beads were
similar to that of cell pellets for different donors (0.5-4 fold ratio
between (+) conditions) while for type II collagen there was a marked increase
in transcript levels in Puramatrix beads compared to cell pellets for every
donor (5-38 fold). Puramatrix disks seeded with human MSCs (from donor
3) cultured in chondrogenic medium with TGF-â3 showed a marked increase
in mechanical properties between days 21 and 42 with accompanying increases
in GAG content (Figure 4, p<0.01, day 21 vs. day 42 for all properties).
Injectable
Self-Assembling Peptide Nanofibers Create Intramyocardial Microenvironments
for Endothelial Cells
Michael E. Davis, PhD; J.P. Michael Motion, BS; Daria A.
Narmoneva, PhD; Tomosaburo Takahashi, MD, PhD; Daihiko Hakuno, MD, PhD;
Roger D. Kamm, PhD; Shuguang Zhang, PhD; Richard T. Lee, MD
Background—Promoting survival of
transplanted cells or endogenous precursors is an important goal. We hypothesized
that a novel approach to promote vascularization would be to create injectable
microenvironments within the myocardium that recruit endothelial cells
and promote their survival and organization.
Methods and Results—In this study
we demonstrate that self-assembling peptides can be injected and that the
resulting nanofiber microenvironments are readily detectable within the
myocardium. Furthermore, the self-assembling peptide nanofiber microenvironments
recruit progenitor cells that express endothelial markers, as determined
by staining with isolectin and for the endothelial-specific protein platelet– endothelial
cell adhesion molecule-1. Vascular smooth muscle cells are recruited to
the microenvironment and appear to form functional vascular structures.
After the endothelial cell population, cells that express -sarcomeric
actin and the transcription factor Nkx2.5 infiltrate the peptide microenvironment.
When exogenous donor green fluorescent protein–positive neonatal
cardiomyocytes were injected with the self-assembling peptides, transplanted
cardiomyocytes in the peptide microenvironment survived and also augmented
endogenous cell recruitment.
Conclusions—These experiments demonstrate
that self-assembling peptides can create nanofiber microenvironments in
the myocardium and that these microenvironments promote vascular cell recruitment.
Because these peptide nanofibers may be modified in a variety of ways,
this approach may enable injectable tissue regeneration strategies. (Circulation.
2005; 111:442-450.)
Key Words: tissue engineering, microenvironment, regeneration
Endothelial
cells promote cardiac myocyte survival and spatial reorganization: implications
for cardiac regeneration.
Circulation. 2004 Aug 24;110(8):962-8.
Narmoneva DA, Vukmirovic R, Davis ME, Kamm RD, Lee RT. Cardiovascular
Division, Department of Medicine, Brigham and Women's Hospital, Harvard
Medical School, Boston, USA.
Endothelial-cardiac myocyte (CM) interactions play a key
role in regulating cardiac function, but the role of these interactions
in CM survival is unknown. This study tested the hypothesis that endothelial
cells (ECs) promote CM survival and enhance spatial organization in a 3-dimensional
configuration. METHODS AND RESULTS: Microvascular ECs and neonatal CMs were
seeded on PEPTIDE HYDROGELS in 1 of 3 experimental configurations: CMs alone,
CMs mixed with ECs (coculture), or CMs seeded on preformed EC networks (prevascularized).
Capillary-like networks formed by ECs promoted marked CM reorganization
along the EC structures, in contrast to limited organization of CMs cultured
alone. The presence of ECs markedly inhibited CM apoptosis and necrosis
at all time points. In addition, CMs on preformed EC networks resulted in
significantly less CM apoptosis and necrosis compared with simultaneous
EC-CM seeding (P<0.01, ANOVA). Furthermore, ECs promoted synchronized
contraction of CMs as well as connexin 43 expression. CONCLUSIONS: These
results provide direct evidence for a novel role of endothelium in survival
and organization of nearby CMs. Successful strategies for cardiac regeneration
may therefore depend on establishing functional CM-endothelium interactions.
Entrapment
of migrating hippocampal neural cells in three-dimensional peptide nanofiber
scaffold.
Tissue Engineering. 2004 Mar-Apr;10(3-4):643-55.
Semino CE, Kasahara J, Hayashi Y, Zhang S. Center for Biomedical
Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts,
USA.
Isolation and expansion of self-renewing neural cells ex
vivo are required for neural tissue repair in regenerative medicine. Neurogenesis
occurs in restricted areas of postnatal mammalian brain including dentate
gyrus and subventricular zone. We developed a simple method to entrap migrating
neural cells (potential neuroprogenitors) from postnatal hippocampal organotypic
cultures in three-dimensional (3-D) peptide nanofiber scaffolds. A few hours
after placing the hippocampal slices in culture, cell proliferation activity
at the "interface zone" between the tissue slice and the membrane
culture surface was observed. Pulse-chase experiments using 5-bromodeoxyuridine
(BrdU), which measures mitotic activity, showed that a number of cells incorporated
BrdU at the interface zone. The number of BrdU(+) cells increased exponentially
during the first 3 days of exposure to the label. The BrdU(+) cells also
stained positive for glial fibrillary acidic protein (2.2 +/- 0.5%), a marker
for astroglia; and for betaIII tubulin (7.3 +/- 2.8%) and nestin (2.7 +/-
0.9%), markers for neural progenitors. When hippocampal slices were cultured
on a peptide nanofiber scaffold layer (~500 microm thick), a more extended
interface zone between each tissue slice and the scaffold was formed. Moreover,
the migrating BrdU(+) cell population entrapped in the 3-D peptide scaffold
was readily isolated by mechanically disrupting the scaffold and then used
for conventional 2-D culture systems for further studies. This simple method
may be useful not only in developing technology for neural progenitor cell
isolation and enrichment in vitro, but also for expanding cells for cell-based
therapies of regenerative medicine.
Effects
of dynamic compressive loading on chondrocyte biosynthesis in self-assembling
peptide scaffolds.
Journal of Biomechanics (May 2004)
Kisiday JD, Jin M, DiMicco MA, Kurz B, Grodzinsky AJ.; Biological
Engineering Division, Massachusetts Institute of Technology, Cambridge,
MA, USA.
Dynamic mechanical loading has been reported to affect chondrocyte
biosynthesis in both cartilage explant and chondrocyte-seeded constructs.
In this study, the effects of dynamic compression on chondrocyte-seeded
peptide hydrogels were analyzed for extracellular matrix synthesis and retention
over long-term culture. Initial studies were conducted with chondrocyte-seeded
agarose hydrogels to explore the effects of various non-continuous loading
protocols on chondrocyte biosynthesis. An optimized alternate day loading
protocol was identified that increased proteoglycan (PG) synthesis over
control cultures maintained in free-swelling conditions. When applied to
chondrocyte-seeded peptide hydrogels, alternate day loading stimulated PG
synthesis up to two-fold higher than that in free-swelling cultures. While
dynamic compression also increased PG loss to the medium throughout the
39-day time course, total PG accumulation in the scaffold was significantly
higher than in controls after 16 and 39 days of loading, resulting in an
increase in the equilibrium and dynamic compressive stiffness of the constructs.
Viable cell densities of dynamically compressed cultures differed from free-swelling
controls by less than 20%, demonstrating that changes in PG synthesis were
due to an increase in the average biosynthesis per viable cell. Protein
synthesis was not greatly affected by loading, demonstrating that dynamic
compression differentially regulated the synthesis of PGs. Taken together,
these results demonstrate the potential of dynamic compression for stimulating
PG synthesis and accumulation for applications to in vitro culture of tissue
engineered constructs prior to implantation.
Functional
differentiation of hepatocyte-like spheroid structures from putative liver
progenitor cells in three dimensional peptide scaffolds.
Differentiation (Dec 2003)
Semino CE, Kasahara J, Hayashi Y, Zhang S.; Center for Biomedical Engineering,
Massachusetts Institute of Technology, Cambridge, MA, USA.
Isolation and expansion of self-renewing neural cells ex vivo are required
for neural tissue repair in regenerative medicine. Neurogenesis occurs in
restricted areas of postnatal mammalian brain including dentate gyrus and
subventricular zone. We developed a simple method to entrap migrating neural
cells (potential neuroprogenitors) from postnatal hippocampal organotypic
cultures in three-dimensional (3-D) peptide nanofiber scaffolds. A few hours
after placing the hippocampal slices in culture, cell proliferation activity
at the "interface zone" between the tissue slice and the membrane
culture surface was observed. Pulse-chase experiments using 5-bromodeoxyuridine
(BrdU), which measures mitotic activity, showed that a number of cells incorporated
BrdU at the interface zone. The number of BrdU(+) cells increased exponentially
during the first 3 days of exposure to the label. The BrdU(+) cells also stained
positive for glial fibrillary acidic protein (2.2 +/- 0.5%), a marker for
astroglia; and for betaIII tubulin (7.3 +/- 2.8%) and nestin (2.7 +/- 0.9%),
markers for neural progenitors. When hippocampal slices were cultured on a
peptide nanofiber scaffold layer (~500 microm thick), a more extended interface
zone between each tissue slice and the scaffold was formed. Moreover, the
migrating BrdU(+) cell population entrapped in the 3-D peptide scaffold was
readily isolated by mechanically disrupting the scaffold and then used for
conventional 2-D culture systems for further studies. This simple method may
be useful not only in developing technology for neural progenitor cell isolation
and enrichment in vitro, but also for expanding cells for cell-based therapies
of regenerative medicine.
Self-assembling peptide hydrogel
fosters chondrocyte extracellular matrix production and cell division: Implications
for cartilage tissue repair.
Proceedings of the National Academy of Science (July 2002)
Kisiday J, Jin M, Kurz B, Hung H, Semino C, Zhang S, Grodzinsky AJ.; Biological
Engineering Division, Massachusetts Institute of Technology, Cambridge, MA,
USA.
Emerging medical technologies for effective and lasting repair of articular
cartilage include delivery of cells or cell-seeded scaffolds to a defect site
to initiate de novo tissue regeneration. Biocompatible scaffolds assist in
providing a template for cell distribution and extracellular matrix (ECM)
accumulation in a three-dimensional geometry. A major challenge in choosing
an appropriate scaffold for cartilage repair is the identification of a material
that can simultaneously stimulate high rates of cell division and high rates
of cell synthesis of phenotypically specific ECM macromolecules until repair
evolves into steady-state tissue maintenance. We have devised a self-assembling
peptide hydrogel scaffold for cartilage repair and developed a method to encapsulate
chondrocytes within the peptide hydrogel. During 4 weeks of culture in vitro,
chondrocytes seeded within the peptide hydrogel retained their morphology
and developed a cartilage-like ECM rich in proteoglycans and type II collagen,
indicative of a stable chondrocyte phenotype. Time-dependent accumulation
of this ECM was paralleled by increases in material stiffness, indicative
of deposition of mechanically functional neo-tissue. Taken together, these
results demonstrate the potential of a self-assembling peptide hydrogel as
a scaffold for the synthesis and accumulation of a true cartilage-like ECM
within a three-dimensional cell culture for cartilage tissue repair.
Control of self-assembling oligopeptide matrix formation
through systematic variation of amino acid sequence.
Biomaterials (Jan 2002)
Caplan MR, Schwartzfarb EM, Zhang S, Kamm RD, Lauffenburger DA. Department
of Chemical Engineering, Massachusetts Institute of Technology, Cambridge,
MA, USA.
In order to elucidate design principles for biocompatible materials that
can be created by in situ transformation from self-assembling oligopeptides,
we investigate a class of oligopeptides that can self-assemble in salt solutions
to form three-dimensional matrices. This class of peptides possesses a repeated
sequence of amino acid residues with the type: hydrophobic/negatively-charged/hydrophobic/positively-charged.
We systematically vary three chief aspects of this sequence type: (1) the
hydrophobic side chains: (2) the charged side-chains: and (3) the number of
repeats. Employing a rheometric assay to judge matrix formation, we determine
the critical concentration of NaCl salt solution required to drive transformation
from viscous state to gel state. We find that increasing side-chain hydrophobicity
decreases the critical salt concentration in accord with our previous validation
of DLVO theory for explaining this self-assembly phenomenon Caplan et al.
(Biomacromolecules 1 (2000) 627). Further, we find that increasing the number
of repeats yields a biphasic dependence-first decreasing, then increasing,
the critical salt concentration. We believe that this result is likely due
to an unequal competition between a greater hydrophobic (favorable) effect
and a greater entropic (unfavorable) effect as the peptide length is increased.
Finally, we find that we can use this understanding to rationally alter the
charged side-chains to create a self-assembling oligopeptide sequence that
at pH 7 remains viscous in the absence of salt but gels in the presence of
physiological salt concentrations, a highly useful property for technological
applications.
Extensive neurite outgrowth and active
synapse formation on self-assembling peptide scaffold.
Proceedings of
the National Academy of Science (June 2000)
Holmes TC, de Lacalle S, Su X, Liu G, Rich A, Zhang S.; Center for Biomedical
Engineering, Department of Biology, Center for Learning and Memory, Massachusetts
Institute of Technology, Cambridge, MA, USA.
A new type of self-assembling peptide (sapeptide) scaffolds that serve as
substrates for neurite outgrowth and synapse formation is described. These
peptide-based scaffolds are amenable to molecular design by using chemical
or biotechnological syntheses. They can be tailored to a variety of applications.
The sapeptide scaffolds are formed through the spontaneous assembly of ionic
self-complementary beta-sheet oligopeptides under physiological conditions,
producing a hydrogel material. The scaffolds can support neuronal cell attachment
and differentiation as well as extensive neurite outgrowth. Furthermore, they
are permissive substrates for functional synapse formation between the attached
neurons. That primary rat neurons form active synapses on such scaffold surfaces
in situ suggests these scaffolds could be useful for tissue engineering applications.
The buoyant sapeptide scaffolds with attached cells in culture can be transported
readily from one environment to another. Furthermore, these peptides did not
elicit a measurable immune response or tissue inflammation when introduced
into animals. These biological materials created through molecular design
and self assembly may be developed as a biologically compatible scaffold for
tissue repair and tissue engineering.
Biological surface engineering: a simple system for cell pattern formation.
Biomaterials.
(Jul 1999)
Zhang S, Yan L, Altman M, Lassle M, Nugent H, Frankel F, Lauffenburger DA,
Whitesides GM, Rich A.; Center for Biomedical Engineering, Massachusetts Institute
of Technology, Cambridge, MA, USA.
Biological surface engineering using synthetic biological materials has a
great potential for advances in our understanding of complex biological phenomena.
We developed a simple system to engineer biologically relevant surfaces using
a combination of self-assembling oligopeptide monolayers and microcontact
printing (muCP). We designed and synthesized two oligopeptides containing
a cell adhesion motif (RADS)n (n = 2 and 3) at the N-terminus, followed by
an oligo(alanine) linker and a cysteine residue at the C-terminus. The thiol
group of cysteine allows the oligopeptides to attach covalently onto a gold-coated
surface to form monolayers. We then microfabricated a variety of surface patterns
using the cell adhesion peptides in combination with hexa-ethylene glycol
thiolate which resist non-specific adsorption of proteins and cells. The resulting
patterns consist of areas either supporting or inhibiting cell adhesion, thus
they are capable of aligning cells in a well-defined manner, leading to specific
cell array and pattern formations.
Mechancial properties of
a self-assembling ogliopeptide matrix.
Journal of Biomaterials Science,
Polymer Edition (1998)
Leon EJ, Verma N, Zhang S, Lauffenburger DA, Kamm RD. Center for Biomedical
Engineering, Massachusetts Institute of Technology, Cambridge MA, USA.
We have begun studies of a novel type of biomaterial derived from a recently-discovered
class of ionic self-complementary oligopeptides. These short peptides (typically
8, 16, 24, or 32 amino acid residues with internally-repeating sequences)
self-assemble in aqueous salt solution into three-dimensional matrices capable
of favorable interactions with cells, and offer promise for useful bioengineering
design based on rational changes in sequence. In this paper we present preliminary
results on mechanical properties, combining experimental and theoretical approaches,
of one particular example of these peptide materials, EFK8. The static elastic
modulus was measured using an apparatus designed to allow sample fabrication
and mechanical testing in the same system with the sample in aqueous solution.
The material microstructure was examined by SEM and the measurements interpreted
with the aid of a model for cellular solids. Values for the elastic modulus
increased from 1.59 +/- 0.06 to 14.7 +/- 1.0 kPa for peptide concentrations
increasing from 2.7 to 10 mg ml-1. SEM photographs showed the microstructure
to consist of a relatively homogeneous lattice with fiber thickness of 10-30
nm independent of peptide concentration, but with fiber density increasing
with peptide concentration. This behavior is consistent with scaling predictions
from the cellular solids model and yields an estimate for the individual fiber
elastic modulus in the range of 1-20 MPa. We therefore have provided some
initial physical principles for guiding improvement of the mechanical properties
of these new materials.
Self-complementary oligopeptide matrices
support mammalian cell attachment.
Biomaterials (Dec 1995)
Zhang S, Holmes TC, DiPersio CM, Hynes RO, Su X, Rich A; Department of Biology,
Massachusetts Institute of Technology, Cambridge, MA, USA.
A new class of ionic self-complementary oligopeptides is described. These
oligopeptides consist of regular repeats of alternating ionic hydrophilic
and hydrophobic amino acids and associate to form stable beta-sheet structures
in water. The addition of buffers containing millimolar amounts of monovalent
salts or the transfer of a peptide solution into physiological solutions results
in the spontaneous assembly of the oligopeptides into a stable, macroscopic
membranous matrix. The matrix is composed of ordered filaments which form
porous enclosures. A variety of mammalian cell types are able to attach to
both membranous matrices. These matrices provide a novel experimental system
for analysing mechanisms of in vitro cell attachment and may have applications
in in vivo studies of tissue regeneration, tissue transplantation and would
healing. |
