Bioengineered Skin Constructs Research Articles

Investigation into the significant role of dermal-epidermal interactions in skin ageing utilising a bioengineered skin construct.

Increased prevalence of skin ageing is a growing concern due to an ageing global population and has both sociological and psychological implications. The use of more clinically predictive in vitro methods for dermatological research is becoming commonplace due to initiatives and the cost of clinical testing. In this study, we utilise a well-defined and characterised bioengineered skin construct as a tool to investigate the cellular and molecular dynamics involved in skin ageing from a dermal perspective. Through incorporation of ageing fibroblasts into the dermal compartment we demonstrate the significant impact of dermal-epidermal crosstalk on the overlying epidermal epithelium. We characterise the paracrine nature of dermal-epidermal communication and the impact this has during skin ageing. Soluble factors, such as inflammatory cytokines released as a consequence of senescence associated secretory phenotype (SASP) from ageing fibroblasts, are known to play a pivotal role in skin ageing. Here, we demonstrate their effect on epidermal morphology and thickness, but not keratinocyte differentiation or tissue structure. Through a novel in vitro strategy utilising bioengineered tissue constructs, this study offers a unique reductionist approach to study epidermal and dermal compartments in isolation and tandem.

Bioengineered skin constructs based on mesenchymal stromal cells and acellular dermal matrix exposed to inflammatory microenvironment releasing growth factors involved in skin repair

BackgroundSkin tissue engineering is a rapidly evolving field of research that effectively combines stem cells and biological scaffolds to replace damaged tissues. Human Wharton’s jelly mesenchymal stromal cells (hWJ-MSCs) are essential to generate tissue constructs, due to their potent immunomodulatory effects and release of paracrine factors for tissue repair. Here, we investigated whether hWJ-MSC grown on human acellular dermal matrix (hADM) scaffolds and exposed to a proinflammatory environment maintain their ability to produce in vitro growth factors involved in skin injury repair and promote in vivo wound healing.MethodsWe developed a novel method involving physicochemical and enzymatic treatment of cadaveric human skin to obtain hADM scaffold. Subsequently, skin bioengineered constructs were generated by seeding hWJ-MSCs on the hADM scaffold (construct 1) and coating it with human platelet lysate clot (hPL) (construct 2). Either construct 1 or 2 were then incubated with proinflammatory cytokines (IL-1α, IL-1β, IL-6, TNF-α) for 12, 24, 48, 72 and 96 h. Supernatants from treated and untreated constructs and hWJ-MSCs on tissue culture plate (TCP) were collected, and concentration of the following growth factors, bFGF, EGF, HGF, PDGF, VEGF and Angiopoietin-I, was determined by immunoassay. We also asked whether hWJ-MSCs in the construct 1 have potential toward epithelial differentiation after being cultured in an epithelial induction stimulus using an air–liquid system. Immunostaining was used to analyze the synthesis of epithelial markers such as filaggrin, involucrin, plakoglobin and the mesenchymal marker vimentin. Finally, we evaluated the in vivo potential of hADM and construct 1 in a porcine full-thickness excisional wound model.ResultsWe obtained and characterized the hADM and confirmed the viability of hWJ-MSCs on the scaffold. In both constructs without proinflammatory treatment, we reported high bFGF production. In contrast, the levels of other growth factors were similar to the control (hWJ-MSC/TCP) with or without proinflammatory treatment. Except for PDGF in the stimulated group. These results indicated that the hADM scaffold maintained or enhanced the production of these bioactive molecules by hWJ-MSCs. On the other hand, increased expression of filaggrin, involucrin, and plakoglobin and decreased expression of vimentin were observed in constructs cultured in an air–liquid system. In vivo experiments demonstrated the potential of both hADM and hADM/hWJ-MSCs constructs to repair skin wounds with the formation of stratified epithelium, basement membrane and dermal papillae, improving the appearance of the repaired tissue.ConclusionshADM is viable to fabricate a tissue construct with hWJ-MSCs able to promote the in vitro synthesis of growth factors and differentiation of these cells toward epithelial lineage, as well as, promote in a full-thickness skin injury the new tissue formation. These results indicate that hADM 3D architecture and its natural composition improved or maintained the cell function supporting the potential therapeutic use of this matrix or the construct for wound repair and providing an effective tissue engineering strategy for skin repair.

Generation and integration of hair follicle-primed spheroids in bioengineered skin constructs

Skin is a complex organ made up of different cell layers, appendages, connective tissues, and immune repertoires. These different components interact extensively to maintain the overall functions of the integumentary system. In particular, appendages such as hair follicles critically contribute to the skin’s function in thermoregulation, sensory perception, and homeostatic regeneration. Despite a strong need for better skin regenerative therapeutics, efforts to bio-engineer highly functional appendage-containing human reconstituted skin in vitro have not yielded much success. Here, we report methods in generating and incorporating hair follicle-primed heterotypic spheroids into epidermal-dermal skin constructs that induced invaginating outgrowths with follicle-like organization and lineage gene expression. By co-culturing epithelial keratinocytes (KCs) with dermal papilla (DP) cells in low attachment plates, we established the media and culture conditions that best supported the viability, signalling and remodelling of the cell aggregates to form 3D KC-DP spheroids with the expression of both DP inductiveness and hair follicle lineage genes. We show that long-term growth and maturation of KC cells in these spheroids was supported by incorporation into epidermal-dermal constructs but not in scaffold-less media. When cultured, the bio-fabricated constructs developed invaginations from the integrated spheroids with follicle-forming potential. The generation of these constructs is a step towards the development of functional hair-bearing skin mimetics.

Donor Age and Time in Culture Affect Dermal Fibroblast Contraction in an In Vitro Hydrogel Model.

Current cellular hydrogel-based skin grafts composed of human dermal fibroblasts and a hydrogel scaffold tend to minimize contraction of full-thickness skin wounds and support skin regeneration. However, there has been no comparison between the sources of the dermal fibroblast used. Products using human adult or neonatal foreskin dermal fibroblasts are often expanded in vitro and used after multiple passages without a clear understanding of the effects of this initial production step on the quality and reproducibility of the cellular behavior. Based on the known effects of 2D tissue culture expansion on cellular proliferation and gene expression, we hypothesized that differences in donor age and time in culture may influence cellular properties and contractile behavior in a fibroblast-populated collagen matrix. Using porcine skin as a model based on its similarity to human skin in structure and wound healing properties, we isolated porcine dermal fibroblasts of three different donor ages for use in a 2D proliferation assay and in a 3D cell-populated collagen matrix contractility assay. In 2D cell culture, doubling time remained relatively consistent between all age groups from passage 1 to 6. In the contractility assays, fetal and neonatal groups contracted faster and generated more contractile force than the adult group at passage 1 in vitro. However, after five passages in culture, there was no difference in contractility between ages. These results show how cellular responses in a hydrogel scaffold differ based on donor age and time in culture in vitro, and suggest that consistency in the cellular component of bioengineered skin products could be beneficial in the biomanufacturing of consistent, reliable skin grafts and graft in vivo models. Future research and therapies using bioengineered skin grafts should consider how results may vary based on donor age and time in culture before seeding. Impact statement Little is known about the impact of donor cell age and time in culture on the contraction of cellular, hydrogel-based skin grafts. These results show how cellular phenotypes of porcine fibroblasts differ based on donor age and time in culture. This information is beneficial when addressing important inconsistencies in biomanufacturing of bioengineered skin grafts and in vitro models. These findings are relevant to research and therapies using bioengineered skin graft models and the results can be used to increase reproducibility and consistency during the production of bioengineered skin constructs. The information from this study can be extrapolated to future in vivo studies using human dermal fibroblasts in an in vivo model to help determine the best donor age and time in culture for optimal wound healing outcomes or more reproducible in vitro testing constructs.

095 Bioengineering a complex skin equivalent for skin care applications

Bioengineered skin constructs provide a physiologically relevant platform for fundamental and translational research. We have developed a complex, robust and reproducible full thickness skin equivalent, which has been validated against in vivo skin using in-depth analyses. To mimic the dermis in vitro, primary fibroblasts were cultured within the Alvetex® Scaffold to produce endogenous extracellular matrix proteins. The robust dermal compartment supports the generation of an organised, stratified and keratinised epidermis. Additional cell types have also been incorporated, such as melanocytes and immune cells, to increase the skin equivalent complexity. The human skin equivalent recapitulates the organised structure of human skin in vitro. Skin constructs that represent different ages have been developed using neonatal, young or ageing cells. The use of ageing and senescent cells recreates the ageing skin phenotype in vitro, with regards to epidermal thinning, decreased keratinocyte proliferation and reduced extracellular matrix synthesis. Pigmented skin equivalents include melanocytes, which localise to the basal layer and transfer melanin to neighbouring keratinocytes to form a protective supranuclear cap. The pigmented skin equivalents are functional, and exposure to ultraviolet radiation induces a tanning effect. Langerhans cells have also been incorporated into the epidermis to produce an immune-competent skin equivalent, which is responsive to topical allergens and irritants. We have developed advanced, robust and reproducible skin constructs that resemble the structure of human skin. These skin equivalents have multifaceted research applications such as investigating the underpinning mechanisms of skin ageing, assessing the effect of exogenous stressors and evaluating cosmetic formulations.

3D printing of a thermosensitive hydrogel for skin tissue engineering: A proof of concept study

Because of important functions of skin, an effective therapy is demanded for serious full-thickness skin injuries. In this study, a thermosensitive poly (N-isopropylacrylamide-co-acrylic acid) (p(NIPAAm-AA) hydrogel was prepared and successfully used for different 3D printing methods, including 3D printing with a single needle nozzle and a single syringe (3D single nozzle extrusion printing), 3D printing with coaxial needles and double syringes (3D coaxial printing), and 3D printing with a single needle nozzle and double syringes (3D hybrid printing). It was found that a relatively high cell viability of keratinocytes, fibroblasts and endothelial cells was achieved when 3D hybrid printing of the hybrid bioink (p(NIPAAm-AA) and fibrin) with cells and the cell viability was independent of cell type, seeding density, printed position and cultivation time. These skin-related cells in the hybrid bioink were printed into a biocompatible porous supporting polyvinyl alcohol (PVA) scaffold with customized patterns and thicknesses and terminal differentiation of these cells were induced by air-liquid-interface (ALI) culture in vitro. Superficial cornification of the epidermis layer as well as sprouting and splitting of the subcutaneous endothelial cells were evidenced by histology and immunofluorescence imaging. The bioengineered skin constructs might be used as potential implants for effective wound healing.

Tissue Engineered Skin and Wound Healing: Current Strategies and Future Directions

The global volume of skin damage or injuries has major healthcare implications and, accounts for about half of the world's annual expenditure in the healthcare sector. In the last two decades, tissue-engineered skin constructs have shown great promise in the treatment of various skin-related disorders such as deep burns and wounds. The treatment methods for skin replacement and repair have evolved from utilization of autologous epidermal sheets to more complex bilayered cutaneous tissue engineered skin substitutes. However, inadequate vascularization, lack of flexibility in drug/growth factors loading and inability to reconstitute skin appendages such as hair follicles limits their utilization for restoration of normal skin anatomy on a routine basis. Recent advancements in cutting-edge technology from stem cell biology, nanotechnology, and various vascularization strategies have provided a tremendous springboard for researchers in developing and manipulating tissue engineered skin substitutes for improved skin regeneration and wound healing. This review summarizes the overview of skin tissue engineering and wound healing. Herein, developments and challenges of various available biomaterials, cell sources and in vitro skin models (full thickness and wound healing models) in tissue-engineered skin research are discussed. Furthermore, central to the discussion is the inclusion of various innovative strategies starting from stem cells, nanotechnology, vascularization strategies, microfluidics to three dimensional (3D) bioprinting based strategies for generation of complex skin mimics. The review then moves on to highlight the future prospects of advanced construction strategies of these bioengineered skin constructs and their contribution to wound healing and skin regeneration on current practice.

Multifaceted role of hair follicle dermal cells in bioengineered skins.

The method of generating bioengineered skin constructs was pioneered several decades ago; nowadays these constructs are used regularly for the treatment of severe burns and nonhealing wounds. Commonly, these constructs are comprised of skin fibroblasts within a collagen scaffold, forming the skin dermis, and stratified keratinocytes overlying this, forming the skin epidermis. In the past decade there has been a surge of interest in bioengineered skins, with researchers seeking alternative cell sources, or scaffolds, from which constructs can be established, and for more biomimetic equivalents with skin appendages. To evaluate whether human hair follicle dermal cells can act as an alternative cell source for engineering the dermal component of engineered skin constructs. We established in vitro skin constructs by incorporating into the collagenous dermal compartment: (i) primary interfollicular dermal fibroblasts, (ii) hair follicle dermal papilla cells or (iii) hair follicle dermal sheath cells. In vivo skins were established by mixing dermal cells and keratinocytes in chambers on top of immunologically compromised mice. All fibroblast subtypes were capable of supporting growth of overlying epithelial cells, both in vitro and in vivo. However, we found hair follicle dermal sheath cells to be superior to fibroblasts in their capacity to influence the establishment of a basal lamina. Human hair follicle dermal cells can be readily interchanged with interfollicular fibroblasts and used as an alternative cell source for establishing the dermal component of engineered skin both in vitro and in vivo.

Reduction of diabetic foot ulcer healing times through use of advanced treatment modalities.

Diabetic wounds are a major health care problem associated with delayed healing and high amputation rates. This review systematically evaluated newer wound care therapies for the treatment of diabetic wounds. More recent means of approaching diabetic foot ulcers include various dressings, off-loading shoes, and bioengineered skin constructs and growth factors. Electrical stimulation, phototherapy, electromagnetic fields, and shockwave therapy have been further proposed as potential treatments. A brief overview of these treatments is presented using peer-reviewed evidenced-based literature. A review of the literature demonstrated that treatment of diabetic wounds has focused on either prevention of the wounds in the form of off-loading shoes or adequate protective dressings or on direct treatment of wounds with bioengineered skin constructs, growth factors, or medical devices that accelerate wound healing. The authors' conclusion, following extensive literature review, is that although excellent national and international guidelines exist regarding suggested approaches to the treatment of the diabetic foot ulcer, there is no definitive or universal consensus on the choice of specific treatment modalities. The importance of optimizing comorbidities and the disease state, hemodynamics, local and peripheral skin and wound care, and metabolic challenges while reducing biological and bacterial burden and minimizing trauma remain the primary approach, followed by choice of the most appropriate treatment material or product.

Stem Cells in Tissue Repair and Regeneration

The field of tissue repair and wound healing has blossomed in the past 30 years. We have gone from recombinant growth factors, to living tissue engineering constructs, to stem cells. The task now is to pursue true regeneration, thus achieving complete restoration of structure and function.

Bioengineered Skin Constructs and Their Use in Wound Healing

Over the past two decades, the field of wound healing and tissue repair has witnessed tremendous advances resulting from the biological sciences, biomedical and tissue engineering, and greater clinical understanding of wounds and their pathophysiology. In large part because of these advances, clinicians are now able to offer and deliver more sophisticated and effective treatments to patients with acute wounds, chronic wounds, burns, and other types of injuries. This report relies on published information focused on bioengineered skin and the authors' perspectives on the application of this technology in wound healing. In some cases, off-label applications of certain bioengineered skin constructs have been used to illustrate the spectrum of usefulness of these constructs. Bioengineered skin (including acellular and cellular products; living and nonliving constructs; and epidermal, dermal, and bilayered therapeutic adjuncts) has resulted in very substantial and demonstrable improvements in wound care. Some of the constructs are U.S. Food and Drug Administration approved for treatment of burns and for impaired healing situations, including venous and diabetic foot ulcers. The advances that have occurred in testing and proving the efficacy of bioengineered skin hold great promise for further improvements in the way this technology is used in the surgical field and in wound care. Advances in therapeutic agents have also led to greater understanding of pathophysiology. Thus, wound bed preparation as a concept and as an approach is in fact the result of the need to maximize the benefits of advanced therapies.

Discussion: Bioengineered Skin Constructs and Their Use in Wound Healing

Discussion: Bioengineered Skin Constructs and Their Use in Wound Healing

123 The Treatment of Venous Leg Ulcerations with a Novel Fetal Bovine Dermal Collagen Matrix with a Comparison to PreClinical Animal Studies

Background: Preclinical animal studies with a fetal bovine dermal collagen matrix suggest that fibroblasts quickly populate the material. At the same time there is a rapid ingrowth of new blood vessels. In short, the matrix quickly becomes living tissue. Experience with bioengineered skin constructs and porcine small intestinal submucosal products suggest that the application of a scaffold or matrix may play a role in the healing of venous leg ulcerations in humans. Methods: A fetal bovine dermal collagen matrix (Primatrix) was applied to patients with long-standing venous leg ulcerations. Histologic examination pre and post application with trichrome staining was employed to differentiate matrix from native collagen. Comparisons between animal and human ulcers were made grossly and histologically. Results: In all patients there was rapid formation of granulation tissue with a decrease in the depth of the wound. This was followed by epithelialization and wound closure. The stimulatory effect persisted for approximately 1 month after which time a second matrix was applied. In contrast to the animal study the grafts exhibited “take” in only one of our patients. Histologic examination in both animals and humans suggests a stimulation of native collagen production as well as an initial incorporation of the Primatrix into the wound bed. Conclusion: Primatrix has demonstrated efficacy in preclinical studies and in a series of patients with venous leg ulcerations. The product may function as a scaffold for the ingrowth of cells essential to wound healing. Further investigation in a randomized controlled study setting is recommended. Acknowledgment: TEI Biosciences

014 Epiboly in Bioengineered Skin as a Novel Method for Studying Epidermal Migration and Determining Construct Viability

There are only a few models for studying epidermal migration in vitro, and their interpretation is made difficult by reliance on cell monolayers and the choice of a specific substrate. In this study, the process of keratinocyte migration and epiboly were investigated by using a bilayered bioengineered skin construct, consisting of human neonatal foreskin keratinocytes and dermal fibroblasts (Apligraf, Organogenesis, Canton, MA). At baseline, 6-mm punch biopsies of the construct were placed in serum-free media (AIM-V) or DMEM with or without 10% FBS. At varying time points the bioengineered skin samples were processed and analyzed by histology and immunostaining. By 72 hours, in a time-dependent manner, the epidermis had migrated over and enveloped the entire dermis (full epiboly). Full epiboly was partially inhibited by serum and was maximal in serum-free medium. Epiboly was preserved 5 days after stated expiration date and was equivalent to that seen in unexpired construct when stored at room temperature. The process of epiboly was downregulated in a dose-dependent manner by neutralizing antibodies to EGF and TGF-beta 1. The migrating epithelium was characterized by decreased keratinocyte proliferation (as per Ki67 immunostaining) and increased expression of vitronectin (epibolin). Increasing concentrations of antibodies of vitronectin blocked the process of epiboly, as did antibodies to the alpha5-betaV integrin receptor, which mediates vitronectin-driven keratinocyte locomotion. Interesting, epiboly was also blocked by preseeding human dermal fibroblasts on the dermal side of the construct. We propose that the process of epiboly in this model can be used to better understand and assess the mechanisms involved in keratinocyte migration and may be used as an assay for establishing construct functional viability.

173 Autologous Bone Marrow-Derived Cells for Accelerating the Healing of Human Chronic Wounds

We have previously shown that resident fibroblasts from human chronic wounds are phenotypically abnormal, displaying an impaired response to TGF-beta 1, decreased TGF-beta Type II receptor expression, and decreased phosphorylation of Smad2, Smad3, and p42/44 MAPK. We now report that these human cells delay healing by approximately 30% when implanted in mouse incisional wounds and in a dorsal flap model. These new findings point to the need for the transplantation of new healthy cells in human chronic wounds. Bioengineered living skin constructs can deliver new cells to chronic wounds, at least for a limited period of time. However, most available bioengineered skin constructs consist of already differentiated allogeneic cells, which do not allow for the possibility of engraftment and reconstitution of wound structures. Recently, in a preliminary report, we have shown that autologous bone marrow-derived cells can dramatically enhance the healing of recalcitrant chronic wounds when all other treatments have failed. Our present efforts are now focused on characterizing the bone marrow cells involved in this stimulation of wound healing and in developing better ways for their topical delivery to the wound. Here we present evidence that a fibrin construct may be an ideal way of applying bone marrow-derived cells to human chronic wounds. Autologous bone marrow cells are allowed to grow in culture under conditions favoring the survival and proliferation of mesenchymal stem cells (MSC), as shown by surface markers and functional studies. This usually requires two weeks after bone marrow harvesting. The cellular component is then placed in a fibrinogen solution which, when simultaneously combined with thrombin through a CO2 driven flow, delivers a fine cell-containing fibrin polymer film to the wound. In vitro and in vivo experiments, both in mouse models and in human wounds, show the feasibility of this approach.

Migration of the Epidermal over the Dermal Component (Epiboly) in a Bilayered Bioengineered Skin Construct

A bilayered bioengineered living skin construct (LSC) consisting of viable human neonatal keratinocytes over a collagenous dermis seeded with dermal fibroblasts has been used extensively in difficult—to heal human wounds. Its biological properties include production of several mediators, cytokines, and growth factors and the ability to heal itself upon injury. In this study, we investigated the process of keratinocyte migration in LSC. At baseline, 6-mm punch biopsies of the construct were placed in serum-free medium (AIM-V) or Dulbecco's modified Eagle medium. At varying time points, the LSC samples were processed and analyzed using histology and immunohistochemistry. By 72 h, in a time-dependent manner, the overlying epidermis had migrated over and enveloped the entire underlying dermis, a process known as epiboly. Increasing concentrations of neutralizing antibodies to epidermal growth factor or interleukin-1 alpha down-regulated the extent of epiboly, as measured using computerized planimetry, but antibodies to transforming growth factor-beta 1 did not affect it. The consistent expression of laminin V, α3β1 integrin, and vitronectin (epibolin) and its integrin receptor (αvβ5) characterized the tongue of migrating epidermis. Increasing concentrations of antibodies to vitronectin blocked the process of epiboly, as did antibodies to the αvβ5 integrin receptor, which mediates vitronectin-driven keratinocyte locomotion. This process of epiboly provides novel mechanisms of action for bioengineered skin constructs.

Migration of the Epidermal over the Dermal Component (Epiboly) in a Bilayered Bioengineered Skin Construct

A bilayered bioengineered living skin construct (LSC) consisting of viable human neonatal keratinocytes over a collagenous dermis seeded with dermal fibroblasts has been used extensively in difficult-to heal human wounds. Its biological properties include production of several mediators, cytokines, and growth factors and the ability to heal itself upon injury. In this study, we investigated the process of keratinocyte migration in LSC. At baseline, 6-mm punch biopsies of the construct were placed in serum-free medium (AIM-V) or Dulbecco's modified Eagle medium. At varying time points, the LSC samples were processed and analyzed using histology and immunohistochemistry. By 72 h, in a time-dependent manner, the overlying epidermis had migrated over and enveloped the entire underlying dermis, a process known as epiboly. Increasing concentrations of neutralizing antibodies to epidermal growth factor or interleukin-1 alpha down-regulated the extent of epiboly, as measured using computerized planimetry, but antibodies to transforming growth factor-beta 1 did not affect it. The consistent expression of laminin V, alpha3beta1 integrin, and vitronectin (epibolin) and its integrin receptor (alphavbeta5) characterized the tongue of migrating epidermis. Increasing concentrations of antibodies to vitronectin blocked the process of epiboly, as did antibodies to the alphavbeta5 integrin receptor, which mediates vitronectin-driven keratinocyte locomotion. This process of epiboly provides novel mechanisms of action for bioengineered skin constructs.

Epithelial regeneration from bioengineered skin explants in culture

Artificial skin substitutes are beneficial in the treatment of chronic wounds although their performance relative to authentic human skin is unclear. We compared the rate of outgrowth and morphology of neoepidermis from a bioengineered skin construct (Apligraf) with normal adult human skin explants on de-epidermized human dermal growth substrate with or without intact epidermal basement membrane zone. Epithelial outgrowth of air-exposed cultures in serum-supplemented keratinocyte medium was quantified by fluorescence imaging, morphology by light microscopy, biomarkers of keratinocyte activation, proliferation and migration by immunohistochemical analysis, and gelatinases by zymography. Resurfacing from bioengineereed skin explants started earlier than from normal skin but subsequently, from day 3 to day 9, the rate of epidermalization from bioengineered skin was only 40% (206 +/- 23 microm day(-1), mean +/- SEM) of that of authentic skin (521 +/- 17 microm day(-1), P < 0.001). At culture termination at day 11, normal human skin had formed a multilayered and well-structured neoepidermis covering 41.0 +/- 1.2 mm2 of the dermal substrate while bioengineered skin produced a thinner, less organized epithelium covering 20.4 +/- 3.0 mm2. At this later stage, a higher expression of beta-defensin-2, keratin 16, Ki67 and matrix metalloproteinase (MMP)-9 was found in neoepidermis formed from authentic skin than from bioengineered skin. Activated MMP-2 was elevated in bioengineered skin-derived neoepidermis. Minor epithelial outgrowth was noted with either skin type on the dermal substrate devoid of basement membrane zone. Cultured normal skin explants produced a more uniform and expansive in vivo-like neoepidermis than bioengineered skin explants.

Clinical classification of bioengineered skin use and its correlation with healing of diabetic and venous ulcers.

Chronic wounds are being treated with bioengineering skin constructs. Yet, there is no standard way of assessing these wounds. We developed a classification system to evaluate wounds after construct application. The classification system evaluates the early clinical effect of bioengineered skin and early construct appearance giving a total score named the skin substitute score. Apply classification system to both venous and diabetic foot ulcers and determine whether classification system has validity and predictability for healing. Evaluated serial photographs in 83 and 78 patients with diabetic foot ulcers and in 84 and 83 patients with venous ulcer on Days 7 and 14, respectively, treated with a bilayered bioengineered skin construct. Applied the classification system and determined the percentages of healed patients. There was a significant correlation between better skin substitute score and complete wound closure for both venous ulcers p=0.002 on Day 7 and p=0.01 on Day 14) and diabetic foot ulcers p=0.0005 on Day 7 and p<0.0001 on Day 14). Optimal clinical effect was associated with complete wound closure. As the clinical effect becomes less than optimal continued clinical persistence of the construct becomes important. This classification system seems to have validity in predicting complete wound closure in wounds treated with a bilayered bioengineered skin construct.

Skin Grafting of Venous Ulcers: A Review of its Current Role

As a therapeutic option, grafting of venous ulcers has not been very successfully received despite the different types of grafting methods. Currently, there are only a few controlled randomized trials offering clear guidance to clinicians. The development of artificially bioengineered skin constructs has led to a renewed interest in wound bed preparation, and preliminary successes suggest that the role of skin grafting could be studied in the current context.