Laminin peptide-conjugated chitosan membrane: Application for keratinocyte delivery in wounded skin

Polysaccharide peptide conjugates: Chemistry, properties and applications

The intention of this publication is to give an overview on research related to conjugates of polysaccharides and peptides. Dextran, chitosan, and alginate were selected, to cover four of the most often encountered functional groups known to be present in polysaccharides. These groups are the hydroxyl, the amine, the carboxyl, and the acetal functionality. A collection of the commonly used chemical reactions for conjugation is provided. Conjugation results into distinct properties compared to the parent polysaccharide, and a number of these characteristics are highlighted. This review aims at demonstrating the applicability of said conjugates with a strong emphasis on biomedical applications, drug delivery, biosensing, and tissue engineering. Some suggestions are made for more rigorous chemistries and analytics that could be investigated. Finally, an outlook is given into which direction the field could be developed further. We hope that this survey provides the reader with a comprehensive summary and contributes to the progress of works that aim at synthetically combining two of the main building blocks of life into supramolecular structures with unprecedented biological response.

Micropatterned gellan gum-based hydrogels tailored with laminin-derived peptides for skeletal muscle tissue engineering

The efficacy of current therapies for skeletal muscle disorders/injuries are limited urging the need for new treatments. Skeletal muscle tissue engineered platforms represent a promising tool to shed light on the pathophysiology of skeletal muscle disorders/injuries and to investigate the efficacy of new therapies. Herein, we developed a skeletal muscle platform composed of aligned and differentiated myoblasts on micropatterned gellan gum (GG)-based hydrogels tailored with a laminin-derived peptide. To this aim, the binding of murine skeletal muscle cells (C2C12) to different laminin-derived peptides (CIKVAVS (V), KNRLTIELEVRTC (T), and RKRLQVQLSIRTC (Q)) and the binding of laminin-derived peptides to chemically functionalized GG was studied. C2C12-binding to peptide V, T and Q was 10%, 48% and 25%, whereas the peptide tethering to GG was 60%, 40% and 31%, respectively. Peptide-biofunctionalized hydrogels prepared with different polymer content showed different mechanics and peptide exposure at hydrogel surface. Cellular adhesion was detected in all hydrogel formulations, but spreading and differentiation was only promoted in peptide Q-biofunctionalized hydrogels and preferably in stiffer hydrogels. Myoblast alignment was promoted in micropatterned hydrogel surfaces. Overall, the engineered skeletal muscle herein proposed can be further explored as a platform to better understand skeletal muscle disorders/injuries and to screen new therapies.

Hydrogel-Supported, Engineered Model of Vocal Fold Epithelium

There is a critical need for the establishment of an engineered model of the vocal fold epithelium that can be used to gain understanding of its role in vocal fold health, disease, and facilitate the development of new treatment options. Toward this goal, we isolated primary vocal fold epithelial cells (VFECs) from healthy porcine larynxes and used them within passage 3. Culture-expanded VFECs expressed the suprabasal epithelial marker cytokeratin 13 and intercellular junctional proteins occludin, E-cadherin, and zonula occludens-1. To establish the engineered model, we cultured VFECs on a hyaluronic acid-derived synthetic basement membrane displaying fibronectin-derived integrin-binding peptide (RGDSP) and/or laminin 111-derived syndecan-binding peptide AG73 (RKRLQVQLSIRT). Our results show that matrix stiffness and composition cooperatively regulate the adhesion, proliferation, and stratification of VFECs. Cells cultured on hydrogels with physiological stiffness (elastic shear modulus, G' = 1828 Pa) adopted a cobblestone morphology with close cell-cell contacts, whereas those on softer matrices (G' = 41 Pa) were spindle shaped with extensive intracellular stress fibers. The development of stratified epithelium with proliferating basal cells and additional (1-2) suprabasal layers requires the presence of both RGDSP and AG73 peptide signals. Supplementation of cytokines produced by vimentin positive primary porcine vocal fold fibroblasts in the VFEC culture led to the establishment of 4-5 distinct cell layers. The engineered vocal fold epithelium resembled native tissue morphologically; expressed cytokeratin 13, mucin 1, and tight/adherens junction markers; and secreted basement membrane proteins collagen IV and laminin 5. Collectively, our results demonstrate that stiffness matching, cell-matrix engagement, and paracrine signaling cooperatively contribute to the stratification of VFECs. The engineered epithelium can be used as a versatile tool for investigations of genetic and molecular mechanisms in vocal fold health and disease.

Peptide-Chitosan Engineered Scaffolds for Biomedical Applications

Peptides are signaling epitopes that control many vital biological events. Increased specificity, synthetic feasibility with concomitant lack of toxicity, and immunogenicity make this emerging class of biomolecules suitable for different applications including therapeutics, diagnostics, and biomedical engineering. Further, chitosan, a naturally occurring linear polymer composed of d-glucosamine and N-acetyl-d-glucosamine units, possesses anti-microbial, muco-adhesive, and hemostatic properties along with excellent biocompatibility. As a result, chitosan finds application in drug/gene delivery, tissue engineering, and bioimaging. Despite these applications, chitosan demonstrates limited cell adhesion and lacks biosignaling. Therefore, peptide-chitosan hybrids have emerged as a new class of biomaterial with improved biosignaling properties and cell adhesion properties. As a result, recent studies encompass increased application of peptide-chitosan hybrids as composites or conjugates in drug delivery, cell therapy, and tissue engineering and as anti-microbial material. This review discusses the recent investigations involving chitosan-peptide materials and uncovers various aspects of these interesting hybrid materials for biomedical applications.

Dual Functionalized Injectable Hybrid Extracellular Matrix Hydrogel for Burn Wounds

Low strength and rapid biodegradability of acellular dermal matrix (ADM) restrict its wider clinical application as a rapid cell delivery platform in situ for management of burn wounds. Herein, the extracted ADM was modified by a dual cross-linking approach with ionic crosslinking using chitosan and covalent cross-linking using an iodine-modified 2,5-dihydro-2,5-dimethoxy-furan cross-linker, termed as CsADM-Cl. In addition, inherent growth factors and cytokines were found to be preserved in CsADM-Cl, irrespective of ionic/covalent crosslinking. CsADM-Cl demonstrated improvement in post crosslinking stiffness with a decreased biodegradation rate. This hybrid crosslinked hydrogel supported adhesion, proliferation, and migration of human foreskin-derived fibroblasts and keratinocytes. Also, the angiogenic potential of CsADM-Cl was manifested by chick chorioallantoic membrane assay. CsADM-Cl showed excellent antibacterial activity against Escherichia coli and Staphylococcus aureus. Moreover, CsADM-Cl treated full thickness burn wounds and demonstrated rapid healing marked with superior angiogenesis, well-defined dermal-epidermal junctions, mature basket weave collagen deposition, and development of more pronounced secondary appendages. Altogether, the bioactive CsADM-Cl hydrogel established significant clinical potential to support wound healing as an apt injectable antibacterial matrix to encounter unmet challenges concerning critical burn wounds.

Hydrogel Delivery System Containing Calendulae flos Lyophilized Extract with Chitosan as a Supporting Strategy for Wound Healing Applications

Calendulae flos is a valued plant material with known anti-inflammatory and antimicrobiological properties. The limitation for its use in the treatment of chronic wounds is the lack of adhesion to the required site of action. Obtaining the Calendulae flos lyophilized extract from water-ethanolic extract allowed to prepare valuable material whose biological activity in the wound healing process was confirmed by a positive result of the scratch test. The Calendulae flos lyophilized extract was standardized for the contents of the chlorogenic acid and the narcissin. The significant potency of the Calendulae flos pharmacological activity has become the reason for studies on its novel applications in combination with the multifunctional chitosan carrier, to create a new, valuable solution in the treatment of chronic wounds. The use of chitosan as a carrier allowed for the controlled release of the chlorogenic acid and the narcissin. These substances, characterized by prolonged release from the chitosan delivery system, were identified as well permeable, based on the results of the studies of the parallel artificial membrane permeability assay (PAMPA Skin) a model simulating permeability through membrane skin. The combination of the Calendulae flos lyophilized extract and the chitosan allowed for synergy of action towards hyaluronidase inhibition and effective microbiological activity. Optimization of the hypromellose hydrogel preparation ensuring the required rheological properties necessary for the release of the chlorogenic acid and the narcissin from the chitosan delivery system, as well as demonstrated antimicrobial activity allows indicating formulations of 3% Calendulae flos lyophilized extract with chitosan 80/500 in weight ratio 1:1 and 2% or 3% hypromellose as an important support with high compliance of response and effectiveness for patients suffering from chronic wounds.

Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies

Cutaneous wound healing in adult mammals is a complex multi-step process involving overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodelling. Re-epithelialization describes the resurfacing of a wound with new epithelium. The cellular and molecular processes involved in the initiation, maintenance, and completion of epithelialization are essential for successful wound closure. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here, we focus on cellular mechanisms underlying keratinocyte migration and proliferation during epidermal closure. Inability to re-epithelialize is a clear indicator of chronic non-healing wounds, which fail to proceed through the normal phases of wound healing in an orderly and timely manner. This review summarizes the current knowledge regarding the management and treatment of acute and chronic wounds, with a focus on re-epithelialization, offering some insights into novel future therapies.

Mixed Peptide-Conjugated Chitosan Matrices as Multi-Receptor Targeted Cell-Adhesive Scaffolds

Biomaterials are important for cell and tissue engineering. Chitosan is widely used as a scaffold because it is easily modified using its amino groups, can easily form a matrix, is stable under physiological conditions, and is inactive for cell adhesion. Chitosan is an excellent platform for peptide ligands, especially cell adhesive peptides derived from extracellular matrix (ECM) proteins. ECM proteins, such as collagen, fibronectin, and laminin, are multifunctional and have diverse cell attachment sites. Various cell adhesive peptides have been identified from the ECM proteins, and these are useful to design functional biomaterials. The cell attachment activity of peptides is influenced by the solubility, conformation, and coating efficiency to solid materials, whereas immobilization of peptides to a polysaccharide such as chitosan avoids these problems. Peptide⁻chitosan matrices promote various biological activities depending on the peptide. When the peptides are immobilized to chitosan, the activity of the peptides is significantly enhanced. Further, mixed peptide⁻chitosan matrices, conjugated with more than one peptide on a chitosan matrix, interact with multiple cellular receptors and promote specific biological responses via receptor cross-talk. Receptor cross-talk is important for mimicking the biological activity of ECM and the proteins. The mixed peptide⁻chitosan matrix approach is useful to develop biomaterials as a synthetic ECM for cell and tissue engineering.

Interaction of chitin/chitosan with salivary and other epithelial cells-An overview

Chitin and its deacetylated form, chitosan, have been widely used for tissue engineering of both epithelial and mesenchymal tissues. Epithelial cells characterised by their sheet-like tight cellular arrangement and polarised nature, constitute a major component in various organs and play a variety of roles including protection, secretion and maintenance of tissue homeostasis. Regeneration of damaged epithelial tissues has been studied using biomaterials such as chitin, chitosan, hyaluronan, gelatin and alginate. Chitin and chitosan are known to promote proliferation of various embryonic and adult epithelial cells. However it is not clearly understood how this activity is achieved or what are the mechanisms involved in the chitin/chitosan driven proliferation of epithelial cells. Mechanistic understanding of influence of chitin/chitosan on epithelial cells will guide us to develop more targeted regenerative scaffold/hydrogel systems. Therefore, current review attempts to elicit a mechanistic insight into how chitin and chitosan interact with salivary, mammary, skin, nasal, lung, intestinal and bladder epithelial cells.

Polymeric membranes modulate human keratinocyte differentiation in specific epidermal layers

In vitro models of human bioengineered skin substitutes are an alternative to animal experimentation for testing the effects and toxicity of drugs, cosmetics and pollutants. For the first time specific and distinct human epidermal strata were engineered by using membranes and keratinocytes. To this purpose, biodegradable membranes of chitosan (CHT), polycaprolactone (PCL) and a polymeric blend of CHT-PCL were prepared by phase-inversion technique and characterized in order to evaluate their morphological, physico-chemical and mechanical properties. The capability of membranes to modulate keratinocyte differentiation inducing specific interactions in epidermal membrane systems was investigated. The overall results demonstrated that the membrane properties strongly influence the cell morpho-functional behaviour of human keratinocytes, modulating their terminal differentiation, with the creation of specific epidermal strata or a fully proliferative epidermal multilayer system. In particular, human keratinocytes adhered on CHT and CHT-PCL membranes, forming the structure of the epidermal top layers, such as the corneum and granulosum strata, characterized by withdrawal or reduction from the cell cycle and cell proliferation. On the PCL membrane, keratinocytes developed an epidermal basal lamina, with high proliferating cells that stratified and migrated over time to form a complete differentiating epidermal multilayer system.

Extracellular matrix structure

Extracellular matrix (ECM) is a non-cellular three-dimensional macromolecular network composed of collagens, proteoglycans/glycosaminoglycans, elastin, fibronectin, laminins, and several other glycoproteins. Matrix components bind each other as well as cell adhesion receptors forming a complex network into which cells reside in all tissues and organs. Cell surface receptors transduce signals into cells from ECM, which regulate diverse cellular functions, such as survival, growth, migration, and differentiation, and are vital for maintaining normal homeostasis. ECM is a highly dynamic structural network that continuously undergoes remodeling mediated by several matrix-degrading enzymes during normal and pathological conditions. Deregulation of ECM composition and structure is associated with the development and progression of several pathologic conditions. This article emphasizes in the complex ECM structure as to provide a better understanding of its dynamic structural and functional multipotency. Where relevant, the implication of the various families of ECM macromolecules in health and disease is also presented.

Laminins: Roles and Utility in Wound Repair

Significance: Laminins are complex extracellular macromolecules that are major players in the control of a variety of core cell processes, including regulating rates of cell proliferation, differentiation, adhesion, and migration. Laminins, and related extracellular matrix components, have essential roles in tissue homeostasis; however, during wound healing, the same proteins are critical players in re-epithelialization and angiogenesis. Understanding how these proteins influence cell behavior in these different conditions holds great potential in identifying new strategies to enhance normal wound closure or to treat chronic/nonhealing wounds. Recent Advances: Laminin-derived bioactive peptides and, more recently, laminin-peptide conjugated scaffolds, have been designed to improve tissue regeneration after injuries. These peptides have been shown to be effective in decreasing inflammation and granulation tissue, and in promoting re-epithelialization, angiogenesis, and cell migration. Critical Issues: Although there is now a wealth of knowledge concerning laminin form and function, there are still areas of some controversy. These include the relative contribution of two laminin-based adhesive devices (focal contacts and hemidesmosomes) to the re-epithelialization process, the impact and implications of laminin proteolytic processing, and the importance of laminin polymer formation on cell behavior. In addition, the roles in wound healing of the laminin-related proteins, netrins, and LaNts are still to be fully defined. Future Directions: The future of laminin-based therapeutics potentially lies in the bioengineering of specific substrates to support laminin deposition for ex vivo expansion of autologous cells for graft formation and transplantation. Significant recent advances suggest that this goal is within sight.

Local delivery of alendronate eluting chitosan scaffold can effectively increase osteoblast functions and inhibit osteoclast differentiation

The aim of this study was to investigate the effect of alendronate released from chitosan scaffolds on enhancement of osteoblast functions and inhibition of osteoclast differentiation in vitro. The surface and cell morphologies of chitosan scaffolds and alendronate-loaded chitosan scaffolds were characterized by variable pressure field emission scanning electron microscope (VP-FE-SEM). Alendronate was released in a sustained manner. For evaluating osteoblast functions in MG-63 cells, we investigated cell proliferation, alkaline phosphatase (ALP) activity, and calcium deposition. Furthermore, for evaluating inhibition of osteoclast differentiation in RAW 264.7 cells, we investigated tartrate-resistant acid phosphatase (TRAP) activity, TRAP staining, and gene expressions. The in vitro studies revealed that osteoblasts grown on alendronate-loaded chitosan scaffold showed a significant increment in cell proliferation, ALP activity, and calcium deposition as compared to those grown on chitosan scaffolds. In addition, the in vitro study showed that osteoclast differentiation in RAW 264.7 cells cultured on alendronate-loaded chitosan scaffolds was greatly inhibited as compared to those cultured on chitosan scaffolds by the results of TRAP activity, TRAP staining, and gene expressions. Taken together, alendronate-loaded chitosan scaffolds could achieve the dual functions of improvement in osteoblast functions and inhibition of osteoclast differentiation. Thus, alendronate-eluting chitosan substrates are promising materials for enhancing osteoblast functions and inhibiting osteoclast differentiation in orthopedic and dental fields.

Three-dimensional culture models of mammary gland

The mammary gland is a complex tissue comprised of a branching network of ducts embedded within an adipocyte-rich stroma. The ductal epithelium is a bi-layer of luminal and myoepithelial cells, the latter being in contact with a basement membrane. During pregnancy, tertiary branching occurs and lobuloalveolar structures, which produce milk during lactation, form in response to hormonal and cytokine signals. Postlactational regression is characterized by extensive cell death and tissue remodeling. These complex developmental events have been difficult to mimic in cell culture although many useful culture models exist. Recently, considerable advances in three-dimensional modelling of the mammary gland have been made with the use of collagen and other biomaterials for the study of branching morphogenesis and tumorigenesis, techniques which may enable rapid advances in our understanding of both basic biology and the study of cancer therapeutics.

Laminin active peptide/agarose matrices as multifunctional biomaterials for tissue engineering

Cell adhesive peptides derived from extracellular matrix components are potential candidates to afford bio-adhesiveness to cell culture scaffolds for tissue engineering. Previously, we covalently conjugated bioactive laminin peptides to polysaccharides, such as chitosan and alginate, and demonstrated their advantages as biomaterials. Here, we prepared functional polysaccharide matrices by mixing laminin active peptides and agarose gel. Several laminin peptide/agarose matrices showed cell attachment activity. In particular, peptide AG73 (RKRLQVQLSIRT)/agarose matrices promoted strong cell attachment and the cell behavior depended on the stiffness of agarose matrices. Fibroblasts formed spheroid structures on the soft AG73/agarose matrices while the cells formed a monolayer with elongated morphologies on the stiff matrices. On the stiff AG73/agarose matrices, neuronal cells extended neuritic processes and endothelial cells formed capillary-like networks. In addition, salivary gland cells formed acini-like structures on the soft matrices. These results suggest that the peptide/agarose matrices are useful for both two- and three-dimensional cell culture systems as a multifunctional biomaterial for tissue engineering.

Screening of integrin-binding peptides from the laminin α4 and α5 chain G domain peptide library

Laminins, a multifunctional protein family of extracellular matrix, interact with various types of integrin. Here, integrin-mediated cell adhesive peptides have been systematically screened in the laminin α4 and α5 chain G domain peptide library consisting of 211 peptides by both the peptide-coated plastic plates and peptide-conjugated Sepharose bead assays using human dermal fibroblasts. Thirteen peptides promoted cell spreading and the activity was specifically inhibited by EDTA. Cell attachment to 11 peptides was inhibited by anti-integrin β1 antibody. Additionally, cell attachment to the A5G81 (AGQWHRVSVRWG) and A5G84 (TWSQKALHHRVP) peptides was specifically inhibited by anti-integrin α3 and α6 antibodies. These results suggest that the A5G81 and A5G84 peptides promote integrin α3β1- and α6β1-mediated cell attachment. Further, most of the integrin-mediated cell adhesive peptides are located in the loop regions in the G domains, suggesting that structure is important for the integrin specific recognition. Integrin binding peptides are useful for understanding laminin functions and have a potential to use for biomaterials and drug development.

Biological activity of laminin peptide-conjugated alginate and chitosan matrices

Laminin active peptide-conjugated chitosan mambranes have been previously demonstrated as a useful biomaterial for tissue engineering. Here, three laminin active peptides, A99 (AGTFALRGDNPQG), AG73 (RKRLQVQLSIRT), and EF1zz (ATLQLQEGRLHFXFDLGKGR, X: Nle), which interact with integrin αvβ3, syndecans, and integrin α2β1, respectively, were conjugated to alginate and evaluated the biological activities. A99-alginate (3-3000 ng/mm(2)) promoted cell attachment depending on the amount of alginate. More than 300 ng/mm(2) of the A99-alginate matrices effectively promoted cell attachment, cell spreading with well-organized actin stress fibers, and neurite outgrowth. AG73- and EF1zz-alginates promoted strong cell attachment at the all amounts (3-3000 ng/mm(2)). A99-alginate (30-3000 ng/mm(2)) promoted strong neurite outgrowth but lower amounts of A99-alginate (3 ng/mm(2)) showed weak activity. In contrast, AG73-alginates (3-30 ng/mm(2)) showed strong neurite outgrowth activity but higher amounts of AG73-alginate (300-3000 ng/mm(2)) decreased the activity. These data indicate that neurite outgrowth activity of peptide-alginate matrices is peptide specific and the activity is dependent on the amount of alginate. Further, biological activities of the peptides on alginate and chitosan matrices were different, suggesting that the integrin- and syndecan-mediated cellular functions on the peptide-matrices are highly influenced by the scaffold structure including polysaccharide types and amounts. The laminin active peptide-conjugated alginate and chitosan matrices can control receptor type specific functions and are useful for tissue engineering.

Cell adhesive peptide screening of the mouse laminin α1 chain G domain

Cell adhesive peptides have been widely applied for therapeutic drugs, drug delivery systems, and biomaterials. Previously, we identified various cell adhesive sequences in the G domains of four laminin α chains (α2-α5) by the systematic soluble peptide screening. We also identified five cell-binding sequences in the laminin α1 chain G domain using synthetic peptide-polystyrene beads. Here, we re-screened cell adhesive peptides in the laminin α1 chain G domain by the systematic soluble peptides screening. The 110 soluble peptides were evaluated for their cell adhesive activities using human fibrosarcoma HT1080 cells and human dermal fibroblasts. Fourteen peptides were newly identified as a cell adhesive. Additionally, four peptides (AG22: SSFHFDGSGYAM, AG42: TFDLLRNSYGVRK, AG76: HQNQMDYATLQLQ, AG86: LGGLPSHYRARNI) promoted integrin-mediated cell adhesion. Further, neurite outgrowth activity with rat pheochromocytoma PC12 cells was evaluated and two peptides (AG20: SIGLWNYIEREGK, AG26: SPNGLLFYLASNG) were newly identified for neurite outgrowth activity. These results suggested that the systematic soluble peptides screening approach is an accurate and powerful strategy for finding biologically active sequences. The active sequences newly identified here could be involved in the biological functions of this domain. The active peptides are useful for evaluating molecular mechanisms of laminin-receptor interactions and for developing cell adhesive biomaterials.

Identification of biologically active sequences in the laminin alpha2 chain G domain

Laminin alpha2 chain is specifically expressed in the basement membrane surrounding muscle and nerve. We screened biologically active sequences in the mouse laminin alpha2 chain G domain using 110 soluble peptides by the peptide-coated plate and the peptide-conjugated Sepharose bead assays. Fourteen peptides showed cell attachment activity in either or both assays. Cell attachment to A2G94 (YFDGTGFAKAVG) was inhibited by anti-integrin beta1 antibody, suggesting that the peptide promotes an integrin beta1-mediated cell attachment. Five peptides promoted PC12 cell neurite outgrowth. Since A2G10 (SYWYRIEASRTG) promoted strong cell attachment in the bead assay but showed slight activity in the plate assay, we conjugated A2G10 to chitosan membranes which increase cell attachment activity of the peptides via conformational stability. A2G10-chitosan membrane promoted an integrin alpha6beta1-mediated cell attachment and spreading with well-organized actin stress fibers and neurite outgrowth. These active peptides are useful for evaluating the molecular mechanisms of laminin-receptor interactions.

Adhesion and protease activity in cell lines from human salivary gland tumors are regulated by the laminin-derived peptide AG73, syndecan-1 and beta1 integrin

We studied the induction of protease activity by the laminin alpha1-derived peptide AG73 in cells from adenoid cystic carcinoma (CAC2) and myoepithelioma (M1), respectively a malignant and a benign salivary gland tumors. Laminin alpha1 chain and MMP9 were immunolocalized in adenoid cystic carcinoma and myoepithelioma in vivo and in vitro. Cells grown inside AG73-enriched laminin-111 exhibited large spaces in the extracellular matrix, suggestive of remodeling. The broad spectrum MMP inhibitor GM6001 decreased spaces induced by AG73 in CAC2 and M1 cells. This result strongly suggests that AG73-mediated matrix remodeling involves matrix metalloproteinases. CAC2 and M1 cells cultured on AG73 showed a dose-dependent increase of MMP9 secretion, as detected by zymography. Furthermore, siRNA silencing of MMP9 decreased remodeling in 3D cultures. We searched for AG73 receptors regulating MMP9 activity in our cell lines. CAC2 and M1 cells grown on AG73 exhibited colocalization of syndecan-1 and beta1 integrin. siRNA knockdown of syndecan-1 expression in these cells resulted in decreased adhesion to AG73 and reduced protease and remodeling activity. We investigated syndecan-1 co-receptors in both cell lines. Silencing beta1 integrin inhibited adhesion to AG73, matrix remodeling and protease activity. Double-knockdown experiments were carried out to further explore syndecan-1 and beta1 integrin cooperation. CAC2 cells transfected with both syndecan-1 and beta1 integrin siRNA oligos showed significant decrease in adhesion to AG73. Simultaneous silencing of receptors also induced a decrease in protease activity. Our results suggest that syndecan-1 and beta1 integrin signaling downstream of AG73 regulate adhesion and MMP production by CAC2 and M1 cells.

Culture of subconfluent human fibroblasts and keratinocytes using biodegradable transfer membranes

This study aims to assess the suitability of biodegradable membranes as transfer matrix materials for the culture of subconfluent fibroblasts and keratinocytes. The materials investigated were based on collagen, chitosan and enzyme-digestible cellulose. The proliferation and growth behaviour of human keratinocytes and dermal fibroblasts were analysed and morphology and distribution determined. Cultured fibroblasts exhibited no significant differences in proliferation for the different membrane types, whereas keratinocytes revealed significantly higher proliferation on collagen membranes compared with membranes based on cellulose and chitosan. Co-cultured fibroblasts and keratinocytes from the same donor on collagen membranes showed more homogenous cell distribution, but they segregated in heterologous co-cultures; this effect must be further investigated. Thus, collagen and collagen-coated chitosan membranes are suitable for the subconfluent transfer of human fibroblasts and keratinocytes.

Angiogenic activitiy of syndecan-binding laminin peptide AG73 (RKRLQVQLSIRT)

The AG73 peptide (RKRLQVQLSIRT, mouse laminin alpha 1 chain 2719-2730) promotes cell adhesion and tumor metastasis, and interacts with transmembrane syndecan proteoglycans. Here, we demonstrate AG73 peptide angiogenic activity using in vitro, ex vivo, and in vivo models. AG73 induced murine endothelial cell (SVEC4-10) tube formation on Cultrex Basement Membrane Extract (Cultrex BME) and stimulated sprouting of aortic rings. None of the homologous sequences from the laminin alpha2, alpha3, alpha4, or alpha5 chains was as active as AG73 in promoting sprouting formation. AG73 also mediated angiogenesis in the chick chorioallantonic membrane (CAM) assay. Using subcutaneously injected Cultrex BME supplemented with AG73, we observed a large angiogenic response. Furthermore, AG73-conjugated to a chitosan membrane promoted a strong angiogenic response in the CAM assay. These results indicate that the AG73 peptide is a potent syndecan-binding angiogenesis stimulator and may be useful for therapeutic application to treat ischemic injuries.

Integrin-dependent cell behavior on ECM peptide-conjugated chitosan membranes

Extracellular matrix (ECM) plays an important role in tissue regeneration by promoting cell adhesion, migration, proliferation, and differentiation. ECM mimetics are of importance for tissue engineering because of their functions as scaffolds for cells. Previously, we developed bioactive laminin-derived peptide-conjugated chitosan membranes and demonstrated their cell- and peptide-type specific functions. Here, we conjugated twelve integrin-binding peptides derived from ECM proteins onto chitosan membranes and examined biological activity. Seven peptide-chitosan membranes promoted human foreskin fibroblast attachment. Additionally, FIB1 (YAVTGRGDSPAS; from fibronectin), A99 (AGTFALRGDNPQG; from laminin alpha1 chain), EF1zz (ATLQLQEGRLHFXFDLGKGR, X = Nle; from laminin alpha1 chain), and 531 (GEFYFDLRLKGDKY; from collagen alpha1 (IV) chain) conjugated chitosan membranes promoted integrin-dependent cell adhesion. Various integrins, including alphav, beta1, and beta3, were involved in the cell adhesion to the peptide-chitosan membranes. Further, only the FIB1- and A99-chitosan membranes promoted neurite outgrowth with PC12 rat pheochromocytoma cells. These data demonstrate that peptide-chitosan membranes can regulate specific integrin-mediated cell responses and are useful constructs as ECM mimetics.