Design of an artificial skin. II. Control of chemical composition

Evaluation of a Collagen-Glycosaminoglycan Dermal Substitute in the Dog Palate

Tissue shortage complicates surgery of cleft lip and palate. The healing of defects on the palate impairs growth of the dentoalveolar complex because of scar tissue formation. Implantation of a matrix into the wound might overcome this adverse effect. Integra with and without a silicone top layer was implanted into standardized full-thickness wounds (Ø 6 mm) in the palatal mucoperiosteum in beagle dogs. In some wounds, the silicone layer was removed after 14 days. Control wounds did not have an implant. At 2 and 4 weeks post-surgery, the wounds were assessed for epithelialization, inflammation (hematoxylin and eosin, leucocyte protein L1), number of myofibroblasts (alpha smooth muscle actin), and general histological characteristics. Wounds filled with Integra without the silicone layer showed fewer myofibroblasts and inflammatory cells than the sham wounds. Collagen fibers were more randomly orientated in these wounds than in the sham group. Wound closure was found to be retarded, and many inflammatory cells were present when Integra with silicone was implanted. The silicone layer was lost within 4 weeks in these wounds. We conclude that, in the moist oral environment, the silicone of Integra is not required. Re-epithelialization and tissue integration proceed more favorably without it. Further research in the dentoalveolar development with Integra will be conducted in a simulated cleft palate repair in the dog model.

In vitro and in vivo biological performance of collagen-chitosan/silicone membrane bilayer dermal equivalent

Skin loss or damage affects severely the life quality of human being and can even cause death in many cases. We report here a bilayer dermal equivalent (BDE) composed of collagen-chitosan porous scaffold and silicone membrane, which can effectively induce the regeneration of dermis in an animal model of full thickness skin loss. The in vitro biosecurity test showed that the BDE had no cytotoxicity, and no remarkable sensitization and irritability. In vitro cell culture proved that the BDE had good biocompatibility to support the proliferation of fibroblasts. Animal test was performed on Bama miniature pig skin. Gross view and histological sections found plenty of fibroblasts and extracellular matrix in the regenerative scaffold after transplantation of the BDE for 4 weeks. Immunohistochemistry results proved that the BDE has the ability to support the angiogenesis of the regenerated dermis. All these results indicate that the BDE might be a promising equivalent in treating dermal loss.

A new technique for calculating individual dermal fibroblast contractile forces generated within collagen-GAG scaffolds

Cell-mediated contraction plays a critical role in many physiological and pathological processes, notably organized contraction during wound healing. Implantation of an appropriately formulated (i.e., mean pore size, chemical composition, degradation rate) three-dimensional scaffold into an in vivo wound site effectively blocks the majority of organized wound contraction and results in induced regeneration rather than scar formation. Improved understanding of cell contraction within three-dimensional constructs therefore represents an important area of study in tissue engineering. Studies of cell contraction within three-dimensional constructs typically calculate an average contractile force from the gross deformation of a macroscopic substrate by a large cell population. In this study, cellular solids theory has been applied to conventional column buckling relationships to quantify the magnitude of individual cell contraction events within a three-dimensional, collagen-glycosaminoglycan scaffold. This new technique can be used for studying cell mechanics with a wide variety of porous scaffolds that resemble low-density, open-cell foams. It extends previous methods for analyzing cell buckling of two-dimensional substrates to three-dimensional constructs. From data available in the literature, the mean contractile force (Fc) generated by individual dermal fibroblasts within the collagen-glycosaminoglycan scaffold was calculated to range between 11 and 41 nN (Fc=26+/-13 nN, mean+/-SD), with an upper bound of cell contractility estimated at 450 nN.

Optimization of UV cross-linking density for durable and nontoxic collagen GAG dermal substitute

Artificial dermal constructs, based upon collagen-glycosaminoglycan matrices (CGMs), provide new options in treating skin defects. However, their clinical effectiveness may be limited by cytotoxicity related to residual aldehydes left over from the manufacturing process. Although both chemical and dehydrothermal (DHT) cross-linking are used to produce CGMs, we hypothesize that optimized nonchemical cross-linking, using ultra-violet (UV) and DHT treatment combinations, may limit cytotoxicity without sacrificing mechanical strength. Porous CGMs were physically cross-linked using a combination of DHT and varying intensities of UV light. These were compared to glutaraldehyde cross-linked controls. Human keratinocytes were seeded in each matrix, and cellular proliferation measured using a microculture tetrazolium dye assay. A scoring system (based on the in vitro contraction rate, stiffness, and cellular growth of a small cylindrical specimen) was developed to assess the best overall physical cross-linking method. More cellular growth was observed in the 90-120 min UV cross-linked group than in the glutaraldehyde-treated group (p < 0.05). Stiffness was maximized after 0-30 min of UV cross-linking. On the basis of our scoring system, DHT combined with 45 min of UV cross-linking produced the best overall matrix in terms of cellular growth and physical durability. UV cross-linked collagen-based biomaterials could be a viable alternative for use in biological applications to eliminate glutaraldehyde-associated cytotoxicity.

Fabrication and characterization of porous hyaluronic acid-collagen composite scaffolds

Hyaluronic acid (HA) plays a vital role in many tissues, influencing water content and mechanical function, and has been shown to have positive biological effects on cell behavior in vitro. To begin to determine whether these benefits can be accessed if HA is incorporated into collagen-based scaffolds for tissue engineering, HA-collagen composite matrices were prepared and selected properties evaluated. HA-collagen scaffolds were cross-linked with carbodiimide and loss rates of HA in culture medium assessed. Scaffold pore structures were evaluated by light and electron microscopy. Adult canine chondrocytes were grown in selected HA-collagen scaffolds to assess the effects of HA on cell behavior. Homogenous HA-collagen slurries were achieved when polyionic complexes were suppressed. HA was uniformly distributed through the scaffolds, which demonstrated honeycomb-like pores with interconnectivity among pores increasing as HA content increased. Virtually all of the HA added to the collagen slurry was incorporated into the composite scaffolds that underwent a 7-day cross-linking protocol. After 5 days in culture medium, the HA content in the scaffolds was 5-7% regardless of initial HA loading. After only 2 weeks in culture cartilaginous tissue was found in the chondrocyte-seeded HA-collagen scaffolds. This study contributes to the understanding of the effects of HA content, pH, and cross-link treatment on pore characteristics and degradation behavior essential for the design of HA-collagen scaffolds. The demonstration that these scaffolds can be populated by chondrocytes and support in vitro formation of cartilaginous tissue warrants further investigation of this material system for tissue engineering.

Incorporation of hyaluronic acid into collagen scaffolds for the control of chondrocyte-mediated contraction and chondrogenesis

Hyaluronic acid (HA), a principal matrix molecule in many tissues, is present in high amounts in articular cartilage. HA contributes in unique ways to the physical behavior of the tissue, and has been shown to have beneficial effects on chondrocyte activity. The goal of this study was to incorporate graduated amounts of HA into type I collagen scaffolds for the control of chondrocyte-mediated contraction and chondrogenesis in vitro. The results demonstrated that the amount of contraction of HA/collagen scaffolds by adult canine articular chondrocytes increased with the HA content of the scaffolds. The greatest amount of chondrogenesis after two weeks was found in the scaffolds which had undergone the most contraction. HA can play a useful role in adjusting the mechanical behavior of tissue engineering scaffolds and chondrogenesis in chondrocyte-seeded scaffolds.

Lithography Technique for Topographical Micropatterning of Collagen-Glycosaminoglycan Membranes for Tissue Engineering Applications

BACKGROUND: An adaptable technique for micropatterning biomaterial scaffolds has enormous implications in controlling cell function and in the development of tissue-engineered (TE) microvasculature. In this paper, we report a technique to embed microscale patterns onto a collagen-glycosaminoglycan (CG) membrane as a first step towards the creation of TE constructs with built-in microvasculature. METHOD OF APPROACH: The CG membranes were fabricated by homogenizing a solution of Type I bovine collagen and chondroitin 6-sulfate in acetic acid and vacuum filtering the solution subsequently. The micropatterning technique consisted of three steps: surface dissolution of base matrix using acetic acid solution, feature resolution by application of uniform pressure and feature stability by glutaraldehyde crosslinking. RESULTS: Application of the new technique yielded patterns in CG membranes with a spatial resolution in the order of 2-3 microns. We show that such a patterned matrix is conducive to the attachment of bovine aortic endothelial cells (BAEC's). CONCLUSIONS: The patterned membranes can be used for the development of complex three-dimensional TE products with built-in flow channels, as templates for topographically directed cell growth, or as a model system to study various microvascular disorders where feature scales are important. The new technique is versatile; topographical patterns can be custom-made for any predetermined design with high spatial resolution and the technique itself can be adapted for use with other scaffold materials.

Bioartificial dermal substitute: a preliminary report on its use for the management of complex combat-related soft tissue wounds

OBJECTIVE

To report our institutional experience with the use of a bioartificial dermal substitute (Integra) combined with subatmospheric pressure [vacuum-assisted closure (VAC)] dressings followed by delayed split-thickness skin grafting for management of complex combat-related soft tissue wounds secondary to blast injuries.

DESIGN

Retrospective review of patients treated December 2004 through November 2005.

SETTING

Military treatment facility.

PATIENTS/PARTICIPANTS

Integra grafting was performed 18 times in 16 wounds at our institution. Indications for Integra placement were wounds not amenable to simple split-thickness skin grafting, specifically those with substantial exposed bone and/or tendon.

INTERVENTION

Patients underwent an average of 8.5 irrigation and debridement procedures and concurrent VAC dressings prior to placement of the Integra. Following Integra grafting, all patients were managed with VAC dressings, changed every 3 to 4 days at the bedside or in clinic, with subsequent split-thickness skin grafting an average of 19 days later.

MAIN OUTCOME MEASUREMENTS

The mechanism and date of injury, size of residual soft tissue deficit, indication for Integra placement, number of irrigation and debridement procedures prior to Integra placement, days from injury to Integra placement, days from Integra placement to split-thickness skin grafting, and clinical outcome were recorded.

RESULTS

Integra placement and subsequent skin grafting was successful in achieving durable and cosmetic definitive coverage in 15 of 16 wounds with two of these patients requiring repeat Integra application. Two patients with difficult VAC dressing placement had early Integra graft failure but successfully healed following repeated Integra application and skin grafting.

CONCLUSIONS

Bioartificial dermal substitute grafting, when coupled with subatmospheric dressing management and delayed split-thickness skin grafting, is an effective technique for managing complex combat-related soft tissue wounds with exposed tendon. This can potentially lessen the need for local rotational or free flap coverage.

Interactions of Collagen Types I and II with Chondroitin Sulfates A−C and Their Effect on Osteoblast Adhesion

Collagen has found use as a scaffold material for tissue engineering as well as a coating material for implants. The main aim of this study was to compare the ability of the collagen types I and II to bind preparations of the chondroitin sulfate types A-C (CS A, CS B, CS C). In addition, the effect of the three CS preparations on the extent of collagen incorporated into fibrils and the morphology of collagen fibrils was investigated, as was the influence of collagen fibril coatings containing CS A-C on titanium surfaces on the adhesion of primary rat osteoblasts. Fibrils of both collagen types bound a higher mass of CS C than CS B and a greater mass of CS B than CS A per milligram of fibrils formed. Fibrils of collagen type II bound a higher mass of CS B and C than collagen I fibrils. The proportion of collagen incorporated into fibrils decreased with increasing CS A and CS C concentration but not with increasing CS B concentration. All three CS preparations caused collagen I and II fibrils to become thinner. CS A and CS B but not CS C appeared to stimulate the formation of focal adhesions by osteoblasts after incubation for 2 hours. These results could be of importance when selecting collagen type or CS type as materials for implant coatings or tissue engineering scaffolds.

Determination of the ligand-binding specificities of the alpha2beta1 and alpha1beta1 integrins in a novel 3-dimensional in vitro model of pancreatic cancer

OBJECTIVES

Pancreatic cancer cells express 2 known collagen-binding integrins, alpha2beta1 and alpha1beta1. The ligand-binding specificity of alpha1beta1 and the integrin/s responsible for mediating the malignant phenotype on type I collagen in the 3-dimensional (3D) tumor microenvironment have not been determined in pancreatic cancer. The aim of the present study was to determine the ligand-binding specificities of the alpha2beta1 and alpha1beta1 integrins using a novel 3D in vitro model of pancreatic cancer.

METHODS

We used 3D type I collagen-glycosaminoglycan scaffolds in adhesion and proliferation assays with pancreatic cancer cell lines, as well as affinity chromatography and inhibition of adhesion assays.

RESULTS

We demonstrate for the first time that CFPAC, BxPC-3, Colo-357, FG, and Panc-1 cells attach to 3D type I collagen scaffolds in an alpha2beta1-specific manner and that this integrin-specific adhesion is required for subsequent cell proliferation. MiaPaCa-2 cells, which do not express the alpha2beta1 or alpha1beta1 integrins, do not attach or proliferate on 3D type I collagen scaffolds. We also demonstrate the novel finding that the alpha1beta1 integrin is a type IV collagen receptor in pancreatic cancer cells.

CONCLUSIONS

These data indicate that targeting alpha2beta1 integrin-specific type I collagen adhesion may have therapeutic value in the treatment of pancreatic cancer.

Thermal and electrical injuries

Through progress in wound management, resuscitation, intensive care treatment, and a coordinated rehabilitation process, modern burn care has been able to deliver substantial increases in survival and improvement in functional outcomes for burn victims. The development of regionalized burn centers has contributed greatly to this progress. As the field of burns matures, burn centers are preparing to meet future challenges through collaborative efforts in disaster management and outcomes research.

Wound closure with EDC cross-linked cultured skin substitutes grafted to athymic mice

Collagen-glycosaminoglycan (C-GAG) sponges are commonly utilized as a substitute for the extracellular matrix of dermal tissue. Cultured skin substitutes (CSS) were assessed, after fabrication using sponges cross-linked with 1-ethyl-3-3-dimethylaminopropylcarbodiimide hydrochloride (EDC) at 0, 1, 5, or 50 mm, for development of viable, stratified skin tissue anatomy in vitro, and for wound contraction and cell viability in vivo. Cross-linking the C-GAG sponges with EDC reduced in vitro contraction of the CSS from a 39% reduction in area in the 0 mm CSS to 0% in the 50 mm group. Conversely, the wounds closed with 0, 1 and 5 mm EDC groups exhibited significantly less wound contraction than the 50 mm group. Engraftment of human cells occurred in 86%, 83%, and 83% of the wounds treated with CSS fabricated using 0, 1, and 5 mm EDC cross-linked sponges, respectively, which were significantly higher engraftment rates than the 50 mm group (17%). These data suggest that low concentrations of EDC can be used to improve the biochemical stability of the C-GAG component of CSS in vitro, and promote stable wound closure.

First experiences with the collagen-elastin matrix Matriderm as a dermal substitute in severe burn injuries of the hand

Restoring function after hand burns plays a major role in the restitution of a quality of life. Thereby the reconstructed pliability of the grafted areas is of utmost importance for good hand function. The collagen elastin matrix Matriderm was evaluated as a dermal substitute for the treatment of severe hand burns. In a series of 10 patients, mean age 43 years, TBSA 22.8%, an early debridement and immediate grafting with the matrix and unmeshed skin graft was carried out in a one-stage procedure. In the early postoperative follow up an overall take rate of 97% was observed. In contrast to conventional skin grafts, the color of the skin grafts over the matrix appeared pale in the first few days, but after 2 weeks no difference was observed. After three months, pliability of the grafted area was excellent, (mean VSS 3.2+/-1.2). Full range of motion was achieved in all hands, no blisters and no unstable or hypertrophic scars occurred. Matriderm has proved to be a dermal substitute suitable for the treatment of hand burns. We therefore consider Matriderm as a promising dermal substitute for the treatment of severe hand burns.

Evaluation and biological characterization of bilayer gelatin/chondroitin-6-sulphate/hyaluronic acid membrane

A biodegradable polymer scaffold was developed using gelatin, chondroitin-6-sulphate, and hyaluronic acid in the form of bilayer network. The bilayer porous structure of gelatin-chondroitin-6-sulphate-hyaluronic acid (G-C6S-HA) membrane was fabricated using different freezing temperatures followed by lyophilization. 1-Ethyl-3(3-dimethylaminopropyl) carbodiimide was used as crosslinking agent to improve the biological stability of the scaffold. The morphology, physical-chemical properties, and biocompatibility of bilayer G-C6S-HA membrane were evaluated in this study. The functional groups change in crosslinked G-C6S-HA scaffold was characterized by fourier transform infrared spectroscopy. The retention of glycosaminoglycan contents and matrix degradation rate were also examined by p-dimethylamino benzaldehyde and 2,4,6-trinitrobenzene sulphonic acid, respectively. Water absorption capacity was carried out to study G-C6S-HA membrane water containing characteristics. The morphology of the bilayer G-C6S-HA membrane was investigated under scanning electron microscope and light microscopy. In vitro biocompatibility was conducted with MTT test, LDH assay, as well as histological analysis. The results showed that the morphology of bilayer G-C6S-HA membrane was well reserved. The physical-chemical properties were also adequate. With good biocompatibility, this bilayer G-C6S-HA membrane would be suitable as a matrix in the application of tissue engineering.

Cell responses to biomimetic protein scaffolds used in tissue repair and engineering

Basic science research in tissue engineering and regenerative medicine aims to investigate and understand the deposition, growth, and remodeling of tissues by drawing together approaches from a range of disciplines. This review discusses approaches that use biomimetic proteins and cellular therapies, both in the development of clinical products and of model platforms for scientific investigation. Current clinical approaches to repairing skin, bone, nerve, heart valves, blood vessels, ligaments, and tendons are described and their limitations identified. Opportunities and key questions for achieving clinical goals are discussed through commonly used examples of biomimetic scaffolds: collagen, fibrin, fibronectin, and silk. The key questions addressed by three-dimensional culture models, biomimetic materials, surface chemistry, topography, and their interaction with cells in terms of durotaxis, mechano-regulation, and complex spatial cueing are reviewed to give context to future strategies for biomimetic technology.

Fibrillogenesis of collagen types I, II, and III with small leucine-rich proteoglycans decorin and biglycan

Collagen has found use as a scaffold material for tissue engineering as well as a coating material for implants with a view to enhancing osseointegration through mimicry of the bone extracellular matrix in vivo. The aim of this study was to compare the collagen types I, II, and III with regard to their ability to bind the small leucine-rich proteoglycans (SLRPs) decorin and biglycan during fibrillogenesis in vitro in phosphate buffer. In addition, the influence of SLRPs on the proportion of collagen molecules incorporated into fibrils during fibrillogenesis in vitro at high and low ionic strength was investigated, as were their effects on the morphology of collagen fibrils and the speed of fibrillogenesis. Considerably more biglycan than decorin was bound by all three collagen types. Collagen II bound significantly more SLRPs in fibrils than collagen I and III. Decorin and biglycan decreased the proportion of collagen molecules of all three collagen types incorporated into fibrils in similar fashion. Biglycan affected neither fibril diameter nor the speed of fibrillogenesis. Decorin reduced the fibril diameter of all three collagen types. The differences in SLRP-binding ability between collagen types could be of significance when selecting collagen type and/or SLRPs as scaffold materials for tissue engineering or implant coatings.

Gene-modified tissue-engineered skin: the next generation of skin substitutes

Tissue engineering combines the principles of cell biology, engineering and materials science to develop three-dimensional tissues to replace or restore tissue function. Tissue engineered skin is one of most advanced tissue constructs, yet it lacks several important functions including those provided by hair follicles, sebaceous glands, sweat glands and dendritic cells. Although the complexity of skin may be difficult to recapitulate entirely, new or improved functions can be provided by genetic modification of the cells that make up the tissues. Gene therapy can also be used in wound healing to promote tissue regeneration or prevent healing abnormalities such as formation of scars and keloids. Finally, gene-enhanced skin substitutes have great potential as cell-based devices to deliver therapeutics locally or systemically. Although significant progress has been made in the development of gene transfer technologies, several challenges have to be met before clinical application of genetically modified skin tissue. Engineering challenges include methods for improved efficiency and targeted gene delivery; efficient gene transfer to the stem cells that constantly regenerate the dynamic epidermal tissue; and development of novel biomaterials for controlled gene delivery. In addition, advances in regulatable vectors to achieve spatially and temporally controlled gene expression by physiological or exogenous signals may facilitate pharmacological administration of therapeutics through genetically engineered skin. Gene modified skin substitutes are also employed as biological models to understand tissue development or disease progression in a realistic three-dimensional context. In summary, gene therapy has the potential to generate the next generation of skin substitutes with enhanced capacity for treatment of burns, chronic wounds and even systemic diseases.

Future of Regenerative Medicine: Challenges and Hurdles

Tissue regeneration strategies such as tissue engineering, growth factor administration, and stem cell-based therapies have undergone significant development over the past two decades. Most notably, we are much closer to realizing the engineering of whole organs and tissue with complex architecture than we were 5 years ago. A major driving force has been the demand placed by the scientific community at large and the public to go beyond simple engineering of tissues and demonstrate functionality in engineered tissues and functional recovery upon transplantation. Some recent advances include de novo engineering of bone, engineering of fully functional bladder, and vascularization of skeletal muscle constructs. Notwithstanding, several challenges lie ahead in making regenerative medicine a viable science of the future, the key being the evolution of programs and policies that promote a close relationship among government agencies, private sector, and academia, more specifically between materials scientists, biologists, and clinicians.

Similarities and differences between induced organ regeneration in adults and early foetal regeneration

At least three organs (skin, peripheral nerves and the conjunctiva) have been induced to regenerate partially in adults following application of porous, degradable scaffolds with highly specific structure (templates). Templates blocked contraction and scar formation by inducing a reduction in the density of contractile fibroblasts (probably myofibroblasts) and by preventing these cells to organize themselves appropriately in the wound. In contrast, during early foetal healing, myofibroblasts were absent and wounds did not close by contraction but rather by spontaneous regeneration. The adult regenerative process has so far led to imperfect recovery of the physiological anatomy of skin (skin appendages were missing), while early foetal healing has led to apparently complete restoration. Furthermore, the mechanism of the adult regenerative process involves thwarting of myofibroblast function while, during early foetal healing, differentiation of myofibroblasts has not yet occurred. The data suggest that induced organ regeneration in the adult is the result of partial reversion to early foetal healing. If so, the adult may conceal a foetal response that may be subject to activation following application of highly active scaffolds or of other substances or cells.

Effects of cross-linking type II collagen-GAG scaffolds on chondrogenesis in vitro: dynamic pore reduction promotes cartilage formation

Articular cartilage tissue-engineering investigations often implement bioassays for chondrogenesis in vitro using articular chondrocytes or mesenchymal stem cells in cell pellets that contract with time in culture, suggesting an association between the processes of contraction of the cell pellet and cartilage formation. The objective of the present study was to investigate this relationship further using adult canine articular chondrocyte-seeded type II collagen-GAG scaffolds. The collagen-GAG scaffolds were chemically cross-linked to achieve a range of cross-link densities. Chondrocyte-seeded scaffolds of varying cross-link densities were then cultured for 2 weeks to evaluate the effect of crosslink density on scaffold contraction and chondrogenesis. Scaffolds with low cross-link densities experienced cell-mediated contraction, increased cell number densities, a greater degree of chondrogenesis (viz., chondrocytic morphology of cells, synthesis of type II collagen), and an apparent increase in the rate of degradation of the scaffold compared to more highly cross-linked scaffolds that resisted cellular contraction. The results of this study suggest the promise of "dynamic pore reduction" for scaffolds for articular cartilage tissue engineering. In this approach, scaffolds would have an initial pore diameter large enough to facilitate cell seeding and a mechanical stiffness low enough to allow for cell-mediated contraction to yield a reduced pore volume to favor chondrogenesis. This approach may provide a useful alternative to traditional means of increasing cell number density and retention of synthesized molecules that promote cartilage formation in tissue-engineered constructs.

Fibroblast remodeling activity at two- and three-dimensional collagen–glycosaminoglycan interfaces

Previously we demonstrated that high throughput gene expression experiments can yield novel information about how cells respond to a collagen-glycosaminoglycan (GAG) three-dimensional culture environment. The goal of the current study was to determine which of these differences result from culture in a three-dimensional construct versus those caused simply by the presence of the collagen-GAG biomaterial. To make this distinction, cells were cultured both in collagen-GAG scaffolds fabricated using a phase separation method and on thin two-dimensional coatings of the same material. Control cells were grown on standard tissue culture polystyrene (TCPS). Cell response was measured using histology and microarray analysis and select results were verified with real time polymerase chain reaction (RT-PCR) assays. Genes involved in matrix remodeling (matrix components, matrix metalloproteinases and growth factors) and angiogenesis (VEGF, HGF and HMOX) were shown to be differentially expressed between the treatment conditions. Several matrix metalloproteinases (MMPs) were up regulated in mesh grown cell while some of their inhibitors (TIMPs) were down regulated. These results suggest that the three-dimensional presentation of the collagen-GAG material to the cells is required to stimulate the observed increase in fibroblast remodeling behavior.

Tissue assembly guided via substrate biophysics: applications to hepatocellular engineering

The biophysical nature of the cellular microenvironment, in combination with its biochemical properties, can critically modulate the outcome of three-dimensional (3-D) multicellular morphogenesis. This phenomenon is particularly relevant for the design of materials suitable for supporting hepatocellular cultures, where cellular morphology is known to be intimately linked to the functional output of the cells. This review summarizes recent work describing biophysical regulation of hepatocellular morphogenesis and function and focuses on the manner by which biochemical cues can concomitantly augment this responsiveness. In particular, two distinct design parameters of the substrate biophysics are examined--microtopography and mechanical compliance. Substrate microtopography, introduced in the form of increasing pore size on collagen sponges and poly(glycolic acid) (PGLA) foams, was demonstrated to restrict the evolution of cellular morphogenesis to two dimensions (subcellular and cellular void sizes) or induce 3-D cellular assembly (supercellular void size). These patterns of morphogenesis were additionally governed by the biochemical nature of the substrate and were highly correlated to resultant levels of cell function. Substrate mechanical compliance, introduced via increased chemical crosslinking of the basement membrane, Matrigel, and polyacrylamide gel substrates, also was shown to be able to induce active two-dimensional (2-D, rigid substrates) or 3-D (malleable substrates) cellular reorganization. The extent of morphogenesis and the ensuing levels of cell function were highly dependent on the biochemical nature of the cellular microenvironment, including the presence of increasing extracellular matrix (ECM) ligand and growth-factor concentrations. Collectively, these studies highlight not only the ability of substrate biophysics to control hepatocellular morphogenesis but also the ability of biochemical cues to further enhance these effects. In particular, results of these studies reveal novel means by which hepatocellular morphogenesis and assembly can be rationally manipulated leading to the strategic control of the expression of liver-specific functions for hepatic tissue-engineering applications.

Reconstructive Surgery with Integra Dermal Regeneration Template: Histologic Study, Clinical Evaluation, and Current Practice

BACKGROUND

Yannas and Burke developed the concept of the dermal regeneration template in the 1970s. It is now a widely accepted tool in the treatment of burns as well as in reconstructive surgery.

METHODS

The authors present a previously published study of Integra used in 20 consecutive patients to reconstruct 30 anatomical sites and then analyze the histologic and clinical outcomes. Wound healing was evaluated by examination of weekly punch biopsy specimens with standard and immunohistochemical stains. Patient satisfaction was assessed using a visual analogue scale, and scar appearance was assessed using a modified Vancouver Scar Scale.

RESULTS

Four distinct phases of dermal regeneration could be demonstrated histologically: imbibition, fibroblast migration, neovascularization, and remodeling and maturation. Full vascularization of the neodermis occurred at 4 weeks. Patients reported increased range of movement and improvement in appearance compared with their preoperative states.

CONCLUSIONS

The color of the matrix reflected the stage of neodermal vascularization. No adnexa, nerve endings, or elastic fibers were seen in any of the specimens. The new collagen was histologically indistinguishable from normal dermal collagen. The authors also present their current protocol and experience with using Integra for a range of reconstructive procedures.

Clinical Approach to Wounds: D??bridement and Wound Bed Preparation Including the Use of Dressings and Wound-Healing Adjuvants

This is a clinical review of current techniques in wound bed preparation found to be effective in assisting the wound-healing process. The process begins with the identification of a correct diagnosis of the wound's etiology and continues with optimizing the patient's medical condition, including blood flow to the wound site. Débridement as the basis of most wound-healing strategies is then emphasized. Various débridement techniques, including surgery, topical agents, and biosurgery, are thoroughly discussed and illustrated. Wound dressings, including the use of negative pressure wound therapy, are then reviewed. To properly determine the timing of advance therapeutic intervention, the wound-healing progress needs to be monitored carefully with weekly measurements. A reduction in wound area of 10 to 15 percent per week represents normal healing and does not mandate a change in the current wound-healing strategy. However, if this level of wound area reduction is not met consistently on a weekly basis, then alternative healing interventions should be considered. There is a growing body of evidence that can provide guidance on the appropriate use of such adjuvants in the problem wound. Several adjuvants are discussed, including growth factor, bioengineered tissues, and hyperbaric medicine.

An investigation to optimize angiogenesis within potential dermal replacements

BACKGROUND

Acute and chronic wounds are costly and invariably expose significant structures. Surgical reconstruction causes donor-site morbidity, scarring, and the need for intensive care. Reconstruction using an artificial dermis avoids donor sites, but available collagen-based solutions are susceptible to poor take. Using an in vitro angiogenic assay, the authors investigated dermal matrices for potential inclusion in a second-generation proangiogenic synthetic dermal replacement.

METHODS

Human placental endothelial cells were cocultured on Cytodex beads (Pharmacia Biotech) and plated in eight different extracellular matrix gels (collagen, fibrin, four glycosaminoglycans, vitronectin, and fibronectin), with or without stimulation from two soluble angiogenic factors. Three different cell lines were used, with 30 beads per condition. Cellular invasion into gels was calculated using Sigma Scan computer software, and statistical comparisons were made.

RESULTS

The authors found that fibrin provided greatest stimulus for endothelial invasion, with invasion in fibrin inhibited by collagen in a concentration-dependent fashion. Invasion by alternative extracellular matrix components and soluble angiogenic factors was far less than that in fibrin.

CONCLUSIONS

The authors identified that extracellular matrices can provide greater angiogenic potential than soluble angiogenic factors. Fibrin provided a better proangiogenic scaffold than collagen. This could well be used to encourage blood vessel ingress and eventual take of a second-generation proangiogenic synthetic dermal replacement.

Conjugation of extracellular matrix proteins to basal lamina analogs enhances keratinocyte attachment

The dermal-epidermal junction of skin contains extracellular matrix proteins that are involved in initiating and controlling keratinocyte signaling events such as attachment, proliferation, and terminal differentiation. To characterize the relationship between extracellular matrix proteins and keratinocyte attachment, a biomimetic design approach was used to precisely tailor the surface of basal lamina analogs with biochemistries that emulate the native biochemical composition found at the dermal-epidermal junction. A high-throughput screening device was developed by our laboratory that allows for the simultaneous investigation of the conjugation of individual extracellular matrix proteins (e.g. collagen type I, collagen type IV, laminin, or fibronectin) as well as their effect on keratinocyte attachment, on the surface of an implantable collagen membrane. Fluorescence microscopy coupled with quantitative digital image analyses indicated that the extracellular matrix proteins adsorbed to the collagen-GAG membranes in a dose-dependent manner. To determine the relationship between extracellular matrix protein signaling cues and keratinocyte attachment, cells were seeded on protein-conjugated collagen-GAG membranes and a tetrazolium-based colorimetric assay was used to quantify viable keratinocyte attachment. Our results indicate that keratinocyte attachment was significantly enhanced on the surfaces of collagen membranes that were conjugated with fibronectin and type IV collagen. These findings define a set of design parameters that will enhance keratinocyte binding efficiency on the surface of collagen membranes and ultimately improve the rate of epithelialization for dermal equivalents.

Engineered skin substitutes: practices and potentials

Wound healing can be problematic in several clinical settings because of massive tissue injury (burns), wound healing deficiencies (chronic wounds), or congenital conditions and diseases. Engineered skin substitutes have been developed to address the medical need for wound coverage and tissue repair. Currently, no engineered skin substitute can replace all of the functions of intact human skin. A variety of biologic dressings and skin substitutes have however contributed to improved outcomes for patients suffering from acute and chronic wounds. These include acellular biomaterials and composite cultured skin analogs containing allogeneic or autologous cultured skin cells.

Evaluation of modifying collagen matrix with RGD peptide through periodate oxidation

The aim of the study is to evaluate the effect of modifying collagen matrices with Arg-Gly-Asp (RGD) peptide through periodate oxidation. The collagen matrices were modified with RGD peptide, by periodate activation. The modified collagen matrices and unmodified matrices were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and electron spectroscopy for chemical analysis (ESCA). Mesenchymal stem cells (MSCs) were used to evaluate the cell compatibility of collagen matrices. In terms of cell growth, the MSCs attached much better on the modified matrix than on the unmodified one. But there was no significant difference between two groups regarding the MSC proliferation. Compared to the unmodified matrices, the mechanical strength of the modified matrix decreased sharply, and its 3D structure was destroyed. Introducing specific RGD receptor-mediated adhesion sites on matrices obviously enhanced the MSC adhesion on collagen matrices, but the coupled method of periodate oxidation would likely result in the declination of the mechanical strength of the matrix, as well as the destruction of the matrix structure. This would affect the cell growth on the matrix, and decrease the histocompatibility of the matrices.

Fibrillar collagen assembled in the presence of glycosaminoglycans to constitute bioartificial stem cell niches in vitro

Fibrillar collagen was reconstituted from mixtures of monomeric tropocollagen and heparin or hyaluronic acid, respectively. Turbidity measurements were utilized to follow the fibrillar assembly and demonstrated the influence of the concentration of the glycosaminoglycan on the maximum optical densities. Thin film coatings of maleic anhydride copolymers were utilized for the covalent immobilization of the fibrillar assemblies to solid supports. Quantification of surface-bound collagen was accomplished by ellipsometry and HPLC-based amino acid analysis indicating that less collagen was immobilized in the presence of the glycosaminoglycans. SEM and AFM revealed various sizes and shapes of the immobilized fibrillar assemblies if collagen fibrils were prepared in the presence of heparin or hyaluronic acid. Human hematopoietic stem cells (HSCs) were cultivated on the surface-bound collagen fibrils and the migration of adherent cells was studied by time-lapse microscopy. Migration rates on fibrillar structures were significantly lower then on tropocollagen indicating a more intimate contact of HSCs to the fibrillar substrates.

Viability and Function of Autologous and Allogeneic Fibroblasts Seeded in Dermal Substitutes after Implantation

BACKGROUND

Fibroblast-seeded collagen sponges have been used for the treatment of skin defects and skin ulcers. However, the viability of the fibroblasts after implantation is still unknown. The objective of this study was to investigate the viability and distribution of autologous and allogeneic fibroblasts after implantation and to clarify which type is more effective for wound healing.

MATERIALS AND METHODS

Skin samples of Hartley guinea pigs were retrieved and autologous fibroblasts were isolated and cultured. Fibroblasts isolated from the skin of a Strain2 guinea pig were used as allogeneic fibroblasts. Three full-thickness wounds were created on the backs of guinea pigs and an acellular collagen sponge, a collagen sponge seeded with autologous fibroblasts, and a collagen sponge seeded with allogeneic fibroblasts were transplanted. Before implantation, fibroblasts were labeled with PKH26. The guinea pigs were sacrificed 1, 2, and 3 weeks after implantation. The epithelization and contraction of the wounds were assessed, and the viability and distribution of the seeded fibroblasts were observed in cross sections.

RESULTS

Three weeks after implantation, the PKH26-labeled autologous and allogeneic fibroblasts remained viable. In the wounds covered with the autologous fibroblast-seeded collagen sponge, the epithelization was fastest, and the percent wound contraction was smallest. In contrast, in the wounds covered with allogeneic fibroblasts, the epithelization was slowest and the percent contraction was largest.

CONCLUSION

The allogeneic fibroblasts seeded in the collagen sponge survived and remained viable on the grafted area, but did not accelerate wound healing.

Antigenicity and immunogenicity of collagen

Pertinent issues of collagen antigenicity and immunogenicity are concisely reviewed as they relate to the design and application of biomedical devices. A brief discussion of the fundamental concepts of collagen immunochemistry is presented, with a subsequent review of documented clinical responses to devices containing reconstituted soluble or solubilized collagen. The significance of atelocollagen, concerns regarding collagen-induced autoimmunity, and other relevant topics are also addressed in the context of current understanding of the human immune response to collagen.

A co-cultured skin model based on cell support membranes

Tissue engineering of skin based on collagen:PCL biocomposites using a designed co-culture system is reported. The collagen:PCL biocomposites having collagen:PCL (w/w) ratios of 1:4, 1:8, and 1:20 have been proven to be biocompatible materials to support both adult normal human epidermal Keratinocyte (NHEK) and mouse 3T3 fibroblast growth in cell culture, respectively, by Dai, Coombes, et al. in 2004. Films of collagen:PCL biocomposites were prepared using non-crosslinking method by impregnation of lyophilized collagen mats with PCL/dichloromethane solutions followed by solvent evaporation. To mimic the dermal/epidermal structure of skin, the 1:20 collagen:PCL biocomposites were selected for a feasibility study of a designed co-culture technique that would subsequently be used for preparing fibroblast/biocomposite/keratinocyte skin models. A 55.3% increase in cell number was measured in the designed co-culture system when fibroblasts were seeded on both sides of a biocomposite film compared with cell culture on one surface of the biocomposite in the feasibility study. The co-culture of human keratinocytes and 3T3 fibroblasts on each side of the membrane was therefore studied using the same co-culture system by growing keratinocytes on the top surface of membrane for 3 days and 3T3 fibroblasts underneath the membrane for 6 days. Scanning electron microscopy (SEM) and immunohistochemistry assay revealed good cell attachment and proliferation of both human keratinocytes and 3T3 fibroblasts with these two types of cells isolated well on each side of the membrane. Using a modified co-culture technique, a co-cultured skin model presenting a confluent epidermal sheet on one side of the biocomposite film and fibroblasts populated on the other side of the film was developed successfully in co-culture system for 28 days under investigations by SEM and immunohistochemistry assay. Thus, the design of a co-culture system based on 1:20 (w/w) collagen:PCL biocomposite membranes for preparation of a bi-layered skin model with differentiated epidermal sheet was proven in principle. The approach to skin modeling reported here may find application in tissue engineering and screening of new pharmaceuticals.

Biodegradability and cell-mediated contraction of porous collagen scaffolds: the effect of lysine as a novel crosslinking bridge

A novel crosslinking method was adopted to modify the porous collagen scaffolds by using a water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDAC) and N-hydroxysuccinimide (NHS) in the presence of lysine, which functions as a crosslinking bridge. In vitro biodegradation tests proved that in the presence of lysine the biostability of the EDAC crosslinked scaffolds was greatly enhanced. The biostability of the resultant scaffolds was also elucidated as a function of the concentrations of lysine and EDAC/NHS. Compared to the Col-DHT, the ability of the Col-EDAC and the Col/Lys to resist cell-mediated contraction (CMC) was greatly enhanced. Yet no obvious difference between the Col-EDAC and the Col/Lys was found with respect to CMC. SEM observations showed that the microstructure of the crosslinked scaffolds could be largely preserved after fibroblast seeding. As a result, MTT assays proved that the fibroblasts in the Col/Lys scaffolds proliferated faster compared to the DHT-treated one on the assumption that the cell viability was preserved to a similar level. Histological section results indicated that the Col/Lys scaffolds had the ability to accelerate the cell infiltration and proliferation. All these results demonstrated that this novel crosslinking method is an effective way to achieve a collagen scaffold with improved biostability and a more stable structure, which can resist cell-mediated contraction. (c) 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 334-342, 2004.

Synthetic scaffold morphology controls human dermal connective tissue formation

Engineering tissues in bioreactors is often hampered by disproportionate tissue formation at the surface of scaffolds. This hinders nutrient flow and retards cell proliferation and tissue formation inside the scaffold. The objective of this study was to optimize scaffold morphology to prevent this from happening and to determine the optimal scaffold geometric values for connective tissue engineering. After comparing lyophilized crosslinked collagen, compression molded/salt leached PEGT/PBT copolymer and collagen-PEGT/PBT hybrid scaffolds, the PEGT/PBT scaffold was selected for optimization. Geometric parameters were determined using SEM, microcomputed tomography, and flow permeability measurements. Fibroblast were seeded and cultured under dynamic flow conditions for 2 weeks. Cell numbers were determined using CyQuant DNA assay, and tissue distribution was visualized in H&E- and Sirius Red-stained sections. Scaffolds 0.5 and 1.5 mm thick showed bridged connected tissue from top-to-bottom, whereas 4-mm-thick scaffolds only revealed tissue ingrowth until a maximum depth of 0.6-0.8 mm. Rapid prototyped scaffold were used to assess the maximal void space (pore size) that still could be filled with tissue. Tissue bridging between fibers was only found at fiber distances < or =401 +/- 60 microm, whereas filling of void spaces in 3D-deposited scaffolds only occurred at distances < or =273 +/- 55 microm. PEGT/PBT scaffolds having similar optimal porosities, but different average interconnected pore sizes of 142 +/- 50, 160 +/- 56 to 191 +/- 69 microm showed comparable seeding efficiencies at day 1, but after 2 weeks the total cell numbers were significantly higher in the scaffolds with intermediate and high interconnectivity. However, only scaffolds with an intermediate interconnectivity revealed homogenous tissue formation throughout the scaffold with complete filling of all pores. In conclusion, significant amount of connective tissue was formed within 14 days using a dynamic culture process that filled all void spaces of a PEGT/PBT scaffolds with the following geometric parameters: thickness 1.5-1.6 mm, pore size range 90-360 microm, and average interconnecting pore size of 160 +/- 56 microm.

The effect of galectin 1 on 3T3 cell proliferation on chitosan membranes

Galectin-1 (GAL1), a beta-galactoside-binding protein, functions in cell adhesion, development, and growth regulation. A number of studies suggest that GAL1 play an important role in enhancing cell adhesion to extracellular matrix and inducing cell proliferation. Chitosan is a derivative of chitin extracted from lobsters, crabs and shrimps' exoskeletons. In clinical medicine, chitosan membrane had been used as a semi-permeable biological dressing. Although chitosan membranes show no cytotoxicity, some cell types (e.g. 3T3 cells) fail to attach and proliferate on their surface. In these studies, we show that over-expression of GAL1 does not enhance 3T3 cell proliferation on chitosan membranes. However, coating the chitosan membrane with recombinant GAL1 proteins significantly expedites 3T3 cells proliferation. The enhanced cell growth was inhibited by thiodigalactoside (TDG, a potent inhibitor of beta-galactoside binding) and GAL1 monoclonal antibodies, suggesting GAL1's specific effect on the proliferation of 3T3 cells upon chitosan membranes. Moreover, immunoblotting detected a markedly suppressed tyrosine phosphorylation in several proteins on 3T3 cell growths upon GAL1-coated chitosan membrane. Pretreating the cells with sodium fluoride (NaF, a phosphatase inhibitor) inhibits the attachment and proliferation of 3T3 cells. These findings support a proposed role for altered levels of protein phosphorylation in GAL1-mediated cell attachment and proliferation on chitosan membranes.

A method for correcting an inverted nipple with an artificial dermis

Various methods have been reported to correct an inverted nipple. Although a satisfactory outcome has been reported with most techniques, each method carries a drawback inherent in the technique itself, including complicated operative technique, sensory disturbance of the nipple, marked scarring of the nipple areola and other donor regions, destruction of breast function, and incomplete correction. This report describes a simple method for correcting an inverted nipple. It incorporates a new concept of using artificial dermis for tissue augmentation and is performed without sacrificing any donor site and complex design. It was applied to four nipples in two nulliparous cases. For all four corrected inverted nipples, good results were obtained, and there have been no complications. There were no deformities of the nipples or the areolas after this procedure, and the surgical scars were inconspicuous.

Use of peracetic acid to sterilize human donor skin for production of acellular dermal matrices for clinical use

We previously reported methods for sterilizing human skin for clinical use. In a comparison of gamma-irradiation, glycerol, and ethylene oxide, sterilization with ethylene oxide after treatment with glycerol provided the most satisfactory dermis in terms of structure and its ability to produce reconstructed skin with many of the characteristics of normal skin. However, the use of ethylene oxide is becoming less common in the United Kingdom due to concerns about its possible genotoxicity. The aim of this study was to evaluate peracetic acid as an alternative sterilizing agent. Skin sterilized with peracetic acid was compared with skin sterilized using glycerol alone or glycerol with ethylene oxide. The effect of subsequently storing peracetic acid sterilized skin in glycerol or propylene glycol was also examined. Acellular dermal matrices were produced after removal of the epidermis and cells in the dermis, processed for histological and ultrastructural analysis, and the biological function was evaluated by reconstitution with keratinocytes and fibroblasts. Results showed that sterilized acellular matrices retained the integrity of dermal structure and major components of the basement membrane. There were no overall significant differences in the ability of these matrices to form reconstructed skin, but peracetic acid alone gave a lower histologic score than when combined with glycerol or propylene glycol. We conclude that peracetic acid sterilization followed by preservation in glycerol or propylene glycol offers a convenient alternative protocol for processing of human skin. It is suggested that this sterile acellular dermis may be suitable for clinical use.

Evaluation of speech intelligibility after a secondary dehiscence operation using an artificial graft in patients with speech disorders after partial glossectomy

The purpose of this study was to evaluate speech intelligibility after a dehiscence operation using artificial grafts for patients with speech disorders after partial glossectomy that were caused by scars resulting from the primary operation. The subjects were six men and three women, who had had a partial glossectomy for tongue cancer followed by direct closure without reconstruction. They were operated on a second time operation to mobilise the residual tongue by dividing the cicatrix. An artificial graft was applied to the wound to maintain the dehiscence. Speech intelligibility was evaluated by a standardised Japanese speech intelligibility test before, and 6 and 12 months after the second operation. The intelligibility scores significantly improved during the first 6 months after the second operation, and continued to improve slightly during the following 6 months. This study suggests that the dehiscence operation using an artificial graft could improve speech in patients after partial glossectomy.

Acceleration of Integra incorporation in complex tissue defects with subatmospheric pressure

In an effort to accelerate vascularization and simplify the care of Integra (Ethicon, Inc., Somerville, N.J.), topical subatmospheric pressure was used for eight patients (age range, 2 to 60 years) with complex wounds. Bone was exposed in 62.5 percent of cases, joint in 50 percent, tendon in 37.5 percent, and bowel in 25 percent. The estimated Integra take rate was 96 percent. Split-thickness skin grafting was performed at 4 to 11 days (mean, 7.25 days), with a 93 percent take rate. No adverse side effects were observed with this technique. Application of subatmospheric pressure improved the take rate and time to vascularization of Integra, compared with previous published results, even with complicated wounds. This technique may be a practical alternative to flap closure.

Degradation of a collagen–chondroitin-6-sulfate matrix by collagenase and by chondroitinase

Highly porous, type I collagen-chondroitin-6-sulfate (collagen-GAG) scaffolds, produced by freeze-drying techniques, have proven to be of value as implants to facilitate the regeneration of certain tissues. The objective of this project was to evaluate changes in the microstructure and mechanical properties of selected collagen-GAG scaffolds as they degrade in an in vitro model system. Environmental scanning electron microscopy and video imaging demonstrated that collagenase degradation caused strut erosion through the creation of 1-3 microm diameter micropits within a 2-h period, leading to eventual removal of strut material and strut breakage. Loss of microstructural topography may have been due to gelatinization when collagen was cleaved by collagenase. Chondroitinase degradation of GAG resulted in swelling of the struts, causing the pores to become smaller and rounder. The compressive modulus of the collagen-GAG matrix decreased when degraded by collagenase, but remained unchanged when degraded by chondroitinase. Carbodiimide-cross-linked matrices were found to have a higher cross-link density, a higher compressive stiffness and a greater resistance to collagenase and chondroitinase, compared to non-cross-linked controls and matrices that were cross-linked by the dehydrothermal process. This investigation provides information that can be used to design collagen-GAG scaffolds with desired compressive stiffness and degradation rate to collagenase and chondroitinase.

A Novel Tubular Scaffold for Cardiovascular Tissue Engineering

We have developed a counter rotating cone extrusion device to produce the next generation of three-dimensional collagen scaffold for tissue engineering. The device can produce a continuously varying fibril angle from the lumen to the outside of a 5-mm-diameter collagen tube, similar to the pattern of heart muscle cells in the intact heart. Our scaffold is a novel, oriented, type I collagen, tubular scaffold. We selected collagen because we believe there are important signals from the collagen both geometrically and biochemically that elicit the in vivo -like phenotypic response from the cardiomyocytes. We have shown that cardiomyocytes can be cultured in these tubes and resemble an in vivo phenotype. This new model system will provide important information leading to the design and construction of a functional, biologically based assist device.

The influence of microtextured basal lamina analog topography on keratinocyte function and epidermal organization

The rational design of future bioengineered skin substitutes requires an understanding of the mechanisms by which the three-dimensional microarchitecture of tissue scaffolds modulates keratinocyte function. Microtextured basal lamina analogs were developed to investigate the relationship between the characteristic topography at the dermal-epidermal interface of native skin and keratinocyte function. Microfabrication techniques were used to create master patterns, negative replicates, and collagen membranes with ridges and channels of length scales (e.g., grooves of 50-200 microm in depth and width) similar to the invaginations found in basal lamina at the dermal-epidermal junction of native skin. Keratinocytes were seeded on the surfaces of basal lamina analogs, and histological analyses were performed after 7 days of tissue culture at the air-liquid interface. The keratinocytes formed a differentiated and stratified epidermis that conformed to the features of the microtextured membranes. Morphometric analyses of immunostained skin equivalents suggest that keratinocyte stratification and differentiation increases as channel depth increases and channel width decreases. This trend was most pronounced in channels with the highest depth-to-width ratios (i.e., 200 microm deep, 50 microm wide). It is anticipated that the findings from these studies will elucidate design parameters to enhance the performance of future bioengineered skin substitutes.