Differential collagen-glycosaminoglycan matrix remodeling by superficial and deep dermal fibroblasts: potential therapeutic targets for hypertrophic scar

Skin substitutes are the preferred treatment option in the case of extensive skin loss following burns or other injuries. Among skin substitutes, cultured skin substitutes containing autologous fibroblasts and keratinocytes on collagen-glycosaminoglycan (C-GAG) matrix are most preferred for wound repair. A significant negative outcome of wound healing is hypertrophic scarring (HTS), a dermal fibroproliferative disorder, that leads to considerable morbidity. To examine the role of superficial and deep dermal fibroblasts in HTS, and determine if they differentially remodel C-GAG matrices, fibroblasts were isolated from superficial and deep dermis of lower abdominal tissue of abdominoplasty patients and cultured on C-GAG matrices for four weeks. Over time, deep fibroblasts contracted and stiffened the matrices significantly more and decreased their ultimate tensile strength compared to superficial fibroblasts. Differential remodeling of C-GAG matrices by fibroblasts obtained from different locations of the same organ has not been reported before. Deep fibroblasts were found to express significantly more osteopontin, angiotensin-II, peroxisome proliferator-activated receptor (PPAR)-α, and significantly less tumor necrosis factor-α, PPAR-β/δ, PPAR-γ, and the proteoglycan, fibromodulin compared to superficial fibroblasts. These molecular targets could potentially be used in therapeutic strategies for treatment of HTS.     

The effect of self-designed bifunctional RGD-containing fusion protein on the behavior of human keratinocytes and dermal fibroblasts

In this study, self-designed bifunctional RGD-containing fusion protein (BFP) was grafted on the petri dish to evaluate its cytotoxicity and attachment efficiency on primary cultured keratinocytes and dermal fibroblasts. Two lengths of the GRGDS sequences were separately fused to the N-terminus and C-terminus of the Trichoderma koningii cellobiohydrolase I gene cellulose-binding domain, to serve as linking molecule between the cell and the substrate. The grafting procedure was no more labor-intensive and could be done just in aqueous condition itself. The epidermal keratinocytes and dermal fibroblasts, harvested and separated from human foreskin, were cultured in serum-free keratinocyte culture medium and DMEM, respectively. The BFP was dissolved in double-deionized water, and was prepared at different concentrations. The BFP solution was subsequently added into the petri dish for grafting. MTT assay, total DNA measurement, and lactate dehydrogenase analysis were used to evaluate the cell viability, cell proliferation, and cytotoxicity. The immunochemical stain and SEM examination were chosen to make sure that the cultured cells still kept in phenotype. The results showed that the self-designed BFP was successfully coated on the petri dish to improve the cells' adhesion. The whole coating procedure was just done in aqueous solution without any organic solvent being involved. This method was much simpler than the traditional one, and there was no possibility to damage the immobilized biomolecules. From the results of the study, BFP could enhance attachment of keratinocytes and dermal fibroblasts without losing normal cell morphology and keep keratinocytes on the desired differentiation pathway. We believe that coating BFP on petri dish not only enhanced the keratinocyte attachment but also promoted keratinocytes proliferation. We suggest that the self-designed BFP has a great potential to apply on surface modification for the tissue-engineering scaffolds in the future.     

An in vitro examination of an extracellular matrix scaffold for use in wound healing

This paper describes evidence that an extracellular matrix (ECM) secreted by human umbilical vein endothelial cells (HUVECs) assembled on gelatin coated plates overlaid by a mixed matrix secreted by human dermal microvascular endothelial cells (HDMECs) and human dermal fibroblasts provides a viable acellular scaffold for use in wound healing. Trypsinized epidermal keratinocytes or colonies from Dispase-digested fresh and cadaver skin tissue adhered and proliferated on either HUVECs ECM/gelatin or mixed matrix overlaid on HUVECs ECM/gelatin. An epithelial-mesenchymal interaction, previously thought to be tissue-specific, was exposed as well as concomitant integrin versatility. Furthermore, heterologous HDMECs and dermal fibroblasts attached and proliferated on the mixed matrix as well as HUVECs ECM. The conditioned medium from HUVECs (HUVECs CM) was found to neutralize the lingering after effects of Dispase, and could be used for the tissue culture of epidermal keratinocytes, HDMECs and dermal fibroblasts, which share related extracellular secretions. Taken together, these results indicate that cultured epithelial autografts can be redesigned to include both epithelial and dermal elements, and advances the acellular 'sandwich' ECM scaffold as a possible structural replacement for the lamina densa and lamina lucida, damaged or completely missing in some wounds and burns.     

Optimization and characterization of an engineered human skin equivalent

Skin equivalents (SEs) have been designed to meet both basic and applied research needs. The successful application of tissue-engineered SEs requires that the reconstituted tissues be endowed with the correct organization and function. A large body of experimental evidence now supports the notion that the inducing effects of mesenchymal tissue on epithelial cell morphogenesis are mediated, at least in part, by extracellular matrix components in addition to cell-cell interactions. A coculture model including both fibroblasts and keratinocytes was used to study the effects of progressive serum reduction on epidermal differentiation, quality of dermal and dermal-epidermal junctions, and expression of extracellular matrix proteins. The cells were successively added to a dermal substrate composed of collagen, glycosaminoglycans, and chitosan. The main aim of this study was to optimize this model for pharmacotoxicological trials. Control skin equivalents were cultured with medium containing 10% serum throughout the production process. Serum content was reduced to 1 and 0% at the air-liquid interface and compared with control skin equivalents. First, we demonstrated that serum deprivation at the air-liquid interface improves keratinocyte terminal differentiation. Second, we showed that, in the absence of serum, the specific characteristics of the SE are maintained, including epidermal and dermal ultrastructure, the expression of major dermal extracellular matrix components (human collagen types I, III, and V, fibronectin, elastin, and fibrillin 1), and the dermal-epidermal junction (laminin, human type IV collagen, alpha6 integrin). Furthermore, our results indicate that coculture models using keratinocytes and fibroblasts have both morphological and functional properties required for biologically useful tissues.     

Cell proliferation and differentiation in a model of human skin equivalent

Recent advances in culturing technology has permitted the production of organotypic models that may be referred to as human skin equivalents (HSE). We have studied histochemical, ultrastructural, and kinetic aspects of an HSE composed by an epidermal equivalent and a dermal equivalent separated by a basement membrane. Only keratinocytes and fibroblasts were present in the epidermal and dermal equivalents, respectively; cells of other lineages were lacking. Keratinocyte stratification and differentiation seemed similar to natural skin. Evidence is shown that such an HSE may also release growth factors such as vascular endothelial growth factor that are believed to play a role in skin grafting. The distribution of cycling cells as well as the values of the growth fraction are comparable to those observed in natural skin. Although the absence of several cells populations that reside in natural skin is a remarkable feature of this HSE, the high levels of tissue organization and cell differentiation lead us to believe that such an HSE may be considered a candidate substitute of human skin in biological, pharmacologic, and clinical applications.     

Regulatory mechanisms of galectin-9 and eotaxin-3 synthesis in epidermal keratinocytes: possible involvement of galectin-9 in dermal eosinophilia of Th1-polarized skin inflammation

BACKGROUND: Skin eosinophilia is a common feature of allergic skin diseases, but it is unclear how epidermal and dermal eosinophil infiltration is controlled. To investigate regulation of localization of eosinophils in skin, we examined the regulatory mechanisms of expression of eosinophil-specific chemoattractants in dermal fibroblasts and epidermal keratinocytes. METHODS: We analyzed production of eotaxin, eotaxin-2, eotaxin-3 and galectin-9 by dermal fibroblasts and epidermal keratinocytes in response to several stimuli in vitro. RESULTS: Dermal fibroblasts produced eotaxin and eotaxin-3 in response to stimulation by interleukin (IL)-4 and/or tumor necrosis factor-alpha. Similarly, IL-4 stimulated epidermal keratinocytes to secrete eotaxin-3. However, we did not detect eotaxin mRNA expression or protein secretion by keratinocytes stimulated in vitro. Interferon (IFN)-gamma induced galectin-9 expression on dermal fibroblasts. Conversely, expression of galectin-9 on epidermal keratinocytes was dose-dependently inhibited by IFN-gamma. The immunohistochemical assays revealed that dermal fibroblasts (but not epidermal keratinocytes) in the lesional skin of psoriasis vulgaris (a Th1-polarized disease) express significant levels of galectin-9. CONCLUSION: Eotaxin-3 contributes to dermal and epidermal eosinophil infiltration in Th2-polarized skin inflammation in which IL-4 is produced. In contrast, IFN-gamma-dominated inflammation appears to mediate eosinophil extravasation into the dermis and eosinophil adhesion to dermal fibroblasts via galectin-9 in association with decreased chemoattractant activity of epidermal galectin-9. The present results reveal a novel mechanism of dermal eosinophilia in IFN-gamma-mediated skin inflammation, and reflect concerted chemoattractant production involving dermal and/or epidermal eosinophilia during changes in the local cytokine profile.     

A new model for studying differentiation and growth of epidermal cultures on hyaluronan-based carrier.

Here, a three-dimensional model based on fragments of human de-epidermized dermis (DED) is prepared in order to study the performance of a microperforated, hyaluronan-based membrane as a carrier of cultured epidermal cells. Hyaluronic acid is, in fact, considered to be an optimal biomaterial allowing proliferation of both keratinocytes and melanocytes, and it is already used for clinical aims. The carrier with subconfluent human epidermal cultures is positioned onto the DED and kept in culture until a new epidermis is formed. This model system allowed to study the migration and growth of human epidermal cells from the carrier, resembling 'in vivo' re-epithelization.     

Chromosome abnormalities of porokeratosis-cultured epidermal keratinocytes. Comparison with those of cultured dermal fibroblasts.

Cultured epidermal keratinocytes and dermal fibroblasts derived from porokeratosis (PK) patients' skin lesions or normal-appearing skin had numerical and sometimes structural chromosomal abnormalities. Such abnormal cells were seen in 4.08% and 0.375% of all the studied epidermal keratinocytes derived from affected skin and normal-appearing skin, respectively. Similar abnormalities were present in 1.70% and 3.67% of the dermal fibroblasts from the patients' affected skin and normal-appearing skin, respectively. Chromosomal abnormalities were more frequent in keratinocytes and fibroblasts from the patients' skin than in keratinocytes (0.429%) or in fibroblasts (1.22%) derived from normal control donors. Clonal proliferation of such abnormal cells was frequently seen in keratinocytes from the patients' affected skin. The frequent appearance of chromosomal abnormalities and clonal proliferation in epidermal keratinocytes may explain skin lesion formation and skin cancer development in PK patients.     

Proliferation of normal human keratinocytes on silicone substrates.

Several polydimethylsiloxane elastomers and gels were tested as culture substrates for proliferating normal human epidermal keratinocytes. Growth kinetics of normal human keratinocytes (NHK) and dermal fibroblasts were compared on 'very soft', 'soft' and 'hard' silicone gels, as well as on standard cell culture polystyrene dishes. Water contact angles and chemical compositions (IRFT-HATR) of the different silicone surfaces were found to be equivalent, although very different from standard cell culture polystyrene. The topography of the surfaces as well as the shape of the keratinocytes and fibroblasts grown on the different substrates were visualized by scanning electron microscopy, and compared. Although the surface softness and topography of the substrates differed markedly, dermal fibroblasts proliferated in serum-containing medium in equivalent manner on all substrates. Again no correlation could be found between the characteristics and the attachment of the substrates and rapid proliferation of the epidermal keratinocytes in defined medium. The epidermal keratinocytes spread, secreted a structured extracellular matrix network and grew up to confluence on all silicone substrates (elastomers and gels), except the relatively 'hard' silicone gel; this could be due to a direct interference by the waves observed on the silicone gel surfaces.     

Dermo-epidermal interactions and skin pharmacology]

Reconstruction of a living skin equivalent provides an in vitro model for the study of skin biology and pharmacology in a tissue organization whose cells differentiate similarly to skin cells in the body. This simplified skin equivalent, composed of normal or abnormal cells, is obtained in two steps: formation of a dermal equivalent is achieved first and this dermis is then covered with an epidermal equivalent. Each of these tissues, as well as the interactions between them, can then be studied. Using this model, we have demonstrated that normal fibroblasts promote epidermal growth, that psoriatic fibroblasts induce increased proliferation of normal keratinocytes, and that the effects of pharmacological agents (such as retinoids) on keratinocyte growth are modulated by fibroblasts.     

Reconstructed human epidermis: absence of Langerhans cells and failure to stimulate allogeneic lymphocytes in vitro

Whole human skin can be reconstructed in vitro, using dermal equivalents made of fibroblasts in a collagen matrix. We recently described a new method of epidermalization of dermal equivalents, based on the insertion of punch biopsies and the migration of epidermal cells (EC) on the reconstructed dermis. In the present study, we show that no MHC class II or T6 positive Langerhans cells (LC) can be detected in this new epidermis. Functional studies with EC of this reconstructed epidermis show that these EC completely fail to induce proliferation of allogeneic lymphocytes in mixed epidermal cell lymphocyte reactions and to raise an allogeneic T cell response. In contrast, fresh EC from the same donors induce a strong proliferative and cytotoxic response of the same effector cells. Moreover, the addition of fresh LC-containing EC autologous to effector lymphocytes does not restore an allogeneic proliferative and cytotoxic response directed against class I different EC of the new epidermis. Such a non-immunogenic whole skin model composed of two compartments, dermis and epidermis, completely devoid of class II-bearing antigen presenting cells, is thus a very promising technique for allogeneic skin grafting in the treatment of burns.     

Influence of an epidermal cell extract on skin healing and scar formation

We have examined the possible regulatory role of epidermal cell extract(s) (ECE) on skin cells, namely fibroblasts and keratinocytes, both in vivo and in vitro with particular reference to modification of scar formation. In an experimental wound model in pigs, it was found that extracts of cultured human and pig keratinocytes stimulated replication of epidermal cells and their migration from wound edges and remnants of hair follicles and sebaceous glands, together with hair growth, but at the same time suppressed fibroblast proliferation in the dermis. Sections of healing skin wounds that had been treated with ECE showed the presence of a thick layer of epidermal cells lying on relatively sparse dermis. There was little or no contraction in treated wounds and scarring was minimal. Clinical studies of granulomatous lesions of horses and ulcerated wounds in dogs that had been treated with ECE supported these findings. In contrast to its apparently general stimulation of keratinocytes in vivo, ECE had a highly selective effect in vitro on epidermal cells plated at low density in the absence of a feeder layer, which suggests that its action in vivo may be confined to a specific sub-population of rapidly proliferating keratinocytes or alternatively mediated through a second messenger from another type of cell. The inhibitory effect of epidermal cell extract on fibroblasts in vitro was shown by its ability to prevent the contraction of collagen sponges by fibroblasts. These results suggest an important role for epidermal factors in the growth regulation of both epidermal and dermal cells during wound healing.     

Cytotoxicity tests for antimicrobial agents using cultured skin substitutes fixed at interface of air and culture medium

The present study is focussed on a new cytotoxicity test using cultured dermal and epidermal sheets, which are fixed at the air and medium interface as a wound surface model. The cultured dermal sheet is composed of human fibroblasts and a collagen matrix, and the cultured epidermal sheet is composed of human keratinocytes and a collagen matrix. Each cultured sheet was fixed at the air and medium interface, over which a piece of test specimen was placed. The in vitro system created, provides a mimetic wound surface since during wound repair, fibroblasts are embedded in an extracellular matrix, while keratinocytes migrate and proliferate on provisional granulation tissue. The results thus obtained in this cytotoxicity test are useful for determining the efficacious amount of antimicrobial agent used in clinical cases.     

Physical plasma therapy accelerates wound re-epithelialisation and enhances extracellular matrix formation in cutaneous skin grafts

Skin grafting is a surgical method of cutaneous reconstruction, which provides volumetric replacement in wounds unable to heal by primary intention. Clinically, full-thickness skin grafts (FTSGs) are placed in aesthetically sensitive and mechanically demanding areas such as the hands, face, and neck. Complete or partial graft failure is the primary complication associated with this surgical procedure. Strategies aimed at improving the rate of skin graft integration will reduce the incidence of graft failure. Cold atmospheric plasma (CAP) is an emerging technology offering innovative clinical applications. The aim of this study was to test the therapeutic potential of CAP to improve wound healing and skin graft integration into the recipient site. In vitro models that mimic wound healing were used to investigate the ability of CAP to enhance cellular migration, a key factor in cutaneous tissue repair. We demonstrated that CAP enhanced the migration of epidermal keratinocytes and dermal fibroblasts. This increased cellular migration was possibly induced by the low dose of reactive oxygen and nitrogen species produced by CAP. Using a mouse model of burn wound reconstructed with a full-thickness skin graft, we showed that wounds treated with CAP healed faster than did control wounds. Immunohistochemical wound analysis showed that CAP treatment enhanced the expression of the dermal–epidermal junction components, which are vital for successful skin graft integration. CAP treatment was characterised by increased levels of Tgfbr1 mRNA and collagen I protein in vivo, suggesting enhanced wound maturity and extracellular matrix deposition. Mechanistically, we show that CAP induced the activation of the canonical SMAD-dependent TGF- β 1 pathway in primary human dermal fibroblasts, which may explain the increased collagen I synthesis in vitro. These studies revealed that CAP improved wound repair and skin graft integration via mechanisms involving extracellular matrix formation. CAP offers a novel approach for treating cutaneous wounds and skin grafts. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Fibroblasts facilitate re-epithelialization in wounded human skin equivalents

The re-epithelialization of the wound involves the migration of keratinocytes from the edges of the wound. During this process, keratinocyte migration and proliferation will depend on the interaction of keratinocytes with dermal fibroblasts and the extracellular matrix. The present study aimed to investigate (1) the role of fibroblasts in the re-epithelialization process and on the reconstitution of the dermal-epidermal junction (DEJ) and (2) differential protein expression during re-epithelialization. For both purposes, three-dimensional human skin equivalents (HSE) were used. A full-thickness wound in HSE was introduced by freezing with liquid nitrogen and a superficial wound by linear incision with a scalpel. The closure of the wound in the absence or presence of exogenous growth factors was followed by monitoring the rate of re-epithelialization and regeneration of the DEJ. The results obtained in this study demonstrate that fibroblasts facilitate wound closure, but they differentially affected the deposition of various basement membrane components. The deposition of laminin 5 at the DEJ was delayed in superficial wounds as compared to the full-thickness wounds. During freeze injury, some basement membrane (BM) components remain associated with the dermal compartment and probably facilitate the BM reconstitution. The re-epithelialization process in full-thickness but not in superficial wounds was accelerated by the presence of keratinocyte growth factor and especially by epidermal growth factor. In addition, we have examined the deposition of various basement membrane components and the differences in protein expression in a laterally expanding epidermis in uninjured HSE. Laminin 5, type IV and VII collagen deposition was decreased in the laterally expanding epidermis, indicating that the presence of these proteins is not required for keratinocyte migration to occur in vitro. Using two-dimensional polyacrylamide gel electrophoresis, we have identified DJ-1, a protein not earlier reported to be differently expressed during the epithelialization process of the skin.     

Sucralfate induces proliferation of dermal fibroblasts and keratinocytes in culture and granulation tissue formation in full-thickness skin wounds

Sucralfate is used to induce healing of gastrointestinal tract ulcers. We evaluated its potential utility in the healing of skin wounds. Initial experiments examined the effects of the sucralfate on proliferation of cultured dermal fibroblasts and keratinocytes. Sucralfate induced proliferation in quiescent cultures of both cell types. Additionally, sucralfate enhanced prostaglandin E₂ synthesis in basal keratinocytes and in interleukin-1-stimulated keratinocytes and dermal fibroblasts. Basal interleukin-1 and 6 release were not affected by sucralfate, but the agent enhanced interleukin-1-stimulated interleukin-6 release from fibroblasts. When applied daily to full-thickness wounds in rats, sucralfate increased the thickness of granulation tissue when assessed at day 12.     

Safety evaluation of human living skin equivalents.

Human living skin equivalents (LSEs) offer an alternative to the use of split-thickness autografts for the treatment of hard-to-heal wounds. LSEs consist of 4 active components: a well-differentiated stratum corneum derived from epidermal keratinocytes, dermal fibroblasts, and an extracellular collagen matrix. Neonatal foreskins are used as the source of keratinocytes and dermal fibroblasts for the manufacture of LSEs. Following isolation and expansion in vitro, the cells are cultured on a 3-dimensional scaffold to give an upper epidermal layer and supporting dermal layer. The resulting product has the appearance and handling characteristics of human skin. Safety evaluation of LSEs begins with insuring that foreskins are obtained only from healthy infants whose mothers are negative for a panel of adventitious agents. Keratinocyte and fibroblast cell banks are characterized using morphologic, biochemical, and histologic criteria; checked for the absence of contaminating cell types such as melanocytes, macrophages, lymphocytes, and Langerhans cells; subjected to rigorous microbiological testing (with any production materials of biological origin); and evaluated for in vivo tumorigenicity. The consistency of certain key morphologic and functional characteristics are regularly assessed. Because an LSE represents an allogeneic graft, preclinical safety studies include in vitro and in vivo determinations of its potential immunogenicity. Immunocompromised (SCID) mice reconstituted with human leukocytes or engrafted with human fetal hematolymphoid organs have been useful animal models for assessing possible immunologic responses to LSEs. Additional preclinical studies are being conducted to show that LSEs are noncytotoxic and lack allergenic, sensitizing, or irritation potential.     

Mixture of fibroblasts and adipose tissue-derived stem cells can improve epidermal morphogenesis of tissue-engineered skin

Many studies demonstrate that the type of adjacent mesenchymal cells can affect epidermal morphogenesis of bilayered tissue-engineered skin. However, whether a mixture of different mesenchymal cell types can improve epidermal morphogenesis of bioengineered skin remains unknown. In this study, keratinocytes, dermal fibroblasts and adipose tissue-derived stem cells (ADSCs) were isolated and purified from human skin and subcutaneous fat. Conditioned medium generated from a mixture of dermal fibroblasts and ADSCs at the ratio of 1:1 was superior to that from fibroblasts or ADSCs alone in promoting keratinocyte proliferation, as indicated by MTT assay. Furthermore, ELISA results showed that the cytokine levels of human hepatocyte growth factor and keratinocyte growth factor (also known as FGF7) in the mixed fibroblasts/ADSC group were higher than those in the ADSC or dermal fibroblasts group. To examine the potential roles of mixed fibroblasts and ADSCs on epidermal morphogenesis, a three-dimensional tissue engineered skin system was applied. Histological analyses demonstrated that keratinocytes proliferated extensively over the mixture of fibroblasts and ADSCs, and formed a thick epidermal layer with well-differentiated structures. Keratin 10 (epidermal differentiation marker) was expressed in the suprabasal layer of bilayered tissue-engineered skin in the mixed fibroblasts and ADSCs group. Desmosomes and hemidesmosomes were detected in the newly formed epidermis by transmission electron microscopy analysis. Together, these findings revealed for the first time that a mixture of fibroblasts and ADSCs in bilayered tissue-engineered skin can improve epidermal morphogenesis.     

UV radiation and prostaglandin E2 up-regulate vascular endothelial growth factor (VEGF) in cultured human fibroblasts

OBJECTIVE AND DESIGN: Exposure to UV radiation is responsible for skin erythema and inflammation. PGE2 is an important inflammatory mediator involved in this process and vascular endothelial growth factor (VEGF) is a potent vascular permeability factor mainly produced by epidermal keratinocytes. This study was aimed at determining whether UVB/A1 radiation and prostaglandin E2 (PGE2) could modulate the production of VEGF by cultured dermal human fibroblasts (HF) in comparison to keratinocytes (HK). MATERIALS AND METHODS: The skin cells derived from foreskin, were cultured in defined medium before treatment by either UVB/A1 radiation, or stimulation by addition of PGE2 (10(-8) to 10(-5) M). The expression of VEGF in cultured fibroblasts and keratinocytes was evaluated at the mRNA (RT-PCR) and protein levels (ELISA). RESULTS: The basal level of VEGF was lower in HF than in HK. Both UVB and UVA1 radiation strongly up-regulated VEGF mRNA and protein in HF whereas UVB but not UVA1 radiation induced a VEGF increase in HK only at the protein level. UVA1, when associated with UVB radiation, showed an additive effect on VEGF secretion in HF but not in HK. PGE2 increased in a dose-dependent manner the expression of VEGF in HF but not in HK. Indomethacin as well as the antioxidant alpha-tocopherol did not reduce UV-induced enhanced secretion of VEGF by both fibroblasts and keratinocytes whereas pyrolidine dithiocarbamate exerted an inhibition of this overexpression. CONCLUSIONS: These results indicate different signaling pathways in the PGE2 and UV-induced regulation of VEGF in dermal fibroblasts and epidermal keratinocytes. They also suggest a role for VEGF from both fibroblasts and keratinocytes in the UV-induced erythema, independent of PGE2. A dermal overexpression of VEGF by fibroblasts from UV-irradiated skin may contribute to dilated microvasculature, a feature of skin photoaging and more generally, to a more permissive stroma to tumor formation than unexposed skin.     

Epithelial tissue reconstruction using cell technologies

The issue of the cellular basis of epithelial tissue engineering, concerning the skin first of all, is discussed. Principles of cultivating human epidermal keratinocytes and formation of living tissue equivalents for grafting to damaged tissues and organs are described. The article presents data on the restoration of damaged tissues after tissue equivalent grafting. Examples of using cellular technologies in combustiology, ophthalmology, oncology, and dentistry are given.