Dermal fibroblasts activate keratinocyte outgrowth on collagen gels

Reflecting the human lip in vitro: Cleft lip skin and mucosa keratinocytes keep their identities

OBJECTIVES

Cell models have shown great promise as tools for research, potentially providing intriguing alternatives to animal models. However, the original tissue characteristics must be maintained in culture, a fact that is often assumed, but seldom assessed. We aimed to follow the retention of the original tissue identities of cleft lip-derived skin and mucosa keratinocytes in vitro.

METHODS

Cleft lip-derived keratinocytes were isolated from discarded tissue along the cleft margins during cheiloplasty. Cell identities were assessed by immunohistochemistry and quantitative real-time PCR for tissue-specific markers and compared with native lip tissue. Moreover, keratinocytes were regularly analyzed for the retention of the original tissue characteristics by the aforementioned methods as well as by differentiation assays.

RESULTS

The various anatomical zones of the human lip could be distinguished using a panel of differentiation and functional-based markers. Using these markers, retention of the original tissue identities could be followed and confirmed in the corresponding primary keratinocytes in culture.

CONCLUSIONS

Our findings promote patient-derived cells retaining their original identities as astonishing and clinically relevant in vitro tools. Such cells allow a better molecular understanding of various lip-associated pathologies as well as their modeling in vitro, including but not restricted to orofacial clefts.

Proteomic Identification and Quantification of Secretory Proteins in Human Dermal Fibroblast-Conditioned Medium for Wound Repair and Hair Regeneration

Background

Human dermal fibroblasts secrete numerous growth factors and proteins that have been suggested to promote wound repair and hair regeneration.

Methods

Human dermal fibroblast-conditioned medium (DFCM) was prepared, and proteomic analysis was performed. Secretory proteins in DFCM were identified using 1-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis, in-gel trypsin protein digestion, and quantitative liquid chromatography tandem mass spectrometry (LC-MS/MS). Identified proteins were analyzed using bioinformatic methods for the classification and evaluation of protein-protein interactions.

Results

Using LC-MS/MS, 337 proteins were identified in DFCM. Among them, 160 proteins were associated with wound repair, and 57 proteins were associated with hair regeneration. Protein-protein interaction network analysis of 160 DFCM proteins for wound repair at the highest confidence score (0.9) revealed that 110 proteins were grouped into seven distinctive interaction networks. Additionally, protein-protein interaction network analysis of 57 proteins for hair regeneration at the highest confidence score revealed that 29 proteins were grouped into five distinctive interaction networks. The identified DFCM proteins were associated with several pathways for wound repair and hair regeneration, including epidermal growth factor receptor, fibroblast growth factor, integrin, Wnt, cadherin, and transforming growth factor-β signaling pathways.

Conclusion

DFCM contains numerous secretory proteins that comprise groups of protein-protein interaction networks that regulate wound repair and hair regeneration.

Effects of Human Fibroblast-Derived Multi-Peptide Factors on the Proliferation and Migration of Nitrogen Plasma-Treated Human Dermal Fibroblasts

Background

Human fibroblast-derived multi-peptide factors (MPFs) promote wound repair by playing crucial roles in cell recruitment, adhesion, attachment, migration, and proliferation.

Methods

Cultured human dermal fibroblasts (HDFs) were directly treated with non-contact low- and high-energy nitrogen plasma and further cultured in various conditioned media. Cell proliferation and wound-healing properties were evaluated.

Results

In Opti-modified Eagle’s medium + GlutaMAX culture, reduced HDF viability was observed 24 h after 2-J/pulse plasma treatment and 12 and 24 h after 3-J/pulse treatment. Meanwhile, in dermal fibroblast-conditioned medium (DFCM) containing MPF culture, reduced HDF viability was observed only 24 h after 3-J/pulse treatment. Under DFCM-MPF culture, the wound area percentage was significantly decreased after 12 and 24 h in untreated HDFs; at 9, 12, and 24 h after 1-J/pulse plasma treatment; at 3, 6, 9, 12, and 24 h after 2-J/pulse plasma treatment; and at 9, 12, and 24 h after 3-J/pulse plasma treatment. Greater migration of HDFs with or without plasma treatment was found in DFCM-MPFs than in other conditioned media.

Conclusion

Low-energy nitrogen plasma treatment promotes HDF proliferation and wound repair. DFCM-MPFs enhanced cell proliferation and improved the wound healing properties of HDFs treated with low- and high-energy plasma.

The potential role of fibroblast-derived multi-peptide factors in activation of growth factors and β-Catenin in hair follicle cells

BACKGROUND

Dermal fibroblasts play a pivotal role in hair follicle regeneration during wound repair. Recently, dermal fibroblast-conditioned medium (DFCM), which contains multi-peptide factors (MPFs), has been used to promote wound repair.

AIM

This study aimed to investigate the stimulatory effects of MPF-containing DFCM on hair growth.

METHODS

MPF-containing DFCM was prepared using human neonatal dermal fibroblasts. Outer root sheath (ORS) and dermal papilla (DP) cells were cultured in MPF-containing DFCM. We examined the expression and secretion of growth factors and cytokines using quantitative polymerase chain reaction and a growth factor array. In addition, the effect of MPFs on β-catenin activity was determined using the TOPflash assay. All experiments were repeated at least three times with separate batches of cells.

RESULTS

MPF-containing DFCM increased keratinocyte growth factor (KGF), vascular endothelial growth factor (VEGF), and epidermal growth factor (EGF) mRNA expression in ORS cells and KGF and VEGF mRNA expression in DP cells. When ORS cells were treated with MPF-containing DFCM, the secretion of several growth factors, including EGF, VEGF, insulin-like growth factor-binding protein (IGFBP)-4, IGFBP-6, and fibroblast growth factor-7, was increased in the cell-cultured medium compared with that in control. Additionally, MPF-containing DFCM increased the transcriptional activation of β-catenin in DP cells.

CONCLUSIONS

These results suggest that MPF-containing DFCM might stimulate hair growth by inducing growth factors in ORS and DP cells and regulating β-catenin in DP cells.

Hormesis: Wound healing and keratinocytes

Hormetic dose responses (i.e., a biphasic dose/concentration response characterized by a low dose stimulation and a high dose inhibition) are shown herein to be commonly reported in the dermal wound healing process, with the particular focus on cell viability, proliferation, and migration of human keratinocytes in in vitro studies. Hormetic responses are induced by a wide range of substances, including endogenous agents, numerous drug and nanoparticle preparations and especially plant derived extracts, including many well-known dietary supplements as well as physical stressor agents, such as low-level laser treatments. Detailed mechanistic studies have identified common signaling pathways and their cross-pathway communications that mediate the hormetic dose responses. These findings suggest that the concept of hormesis plays a fundamental role in wound healing, with important potential implications for agent screening and evaluation, as well as clinical strategies.

Skin substitutes with noncultured autologous skin cell suspension heal porcine full-thickness wounds in a one-stage procedure

Clinical application of skin substitute is typically a two-stage procedure with application of skin substitute matrix to the wound followed by engraftment of a split-thickness skin graft (STSG). This two-stage procedure requires multiple interventions, increasing the time until the wound is epithelialised. In this study, the feasibility of a one-stage procedure by combining bioengineered collagen-chondroitin-6-sulfate (DS1) or decellularised fetal bovine skin substitute (DS2) with autologous skin cell suspension (ASCS) in a porcine full-thickness wound healing model was evaluated. Twelve full-thickness excisional wounds on the backs of pigs received one of six different treatments: empty; ASCS; DS1 with or without ASCS; DS2 with or without ASCS. The ASCS was prepared using a point-of-care device and was seeded onto the bottom side of DS1, DS2, and empty wounds at 80 000 cells/cm² . Wound measurements and photographs were taken on days 0, 9, 14, 21, 28, 35, and 42 post-wounding. Histological analysis was performed on samples obtained on days 9, 14, 28, and 42. Wounds in the empty group or with ASCS alone showed increased wound contraction, fibrosis, and myofibroblast density compared with other treatment groups. The addition of ASCS to DS1 or DS2 resulted in a marked increase in re-epithelialisation of wounds at 14 days, from 15 ± 11% to 71 ± 20% (DS1 vs DS1 + ASCS) or 28 ± 14% to 77 ± 26 (DS2 vs DS2 + ASCS) despite different mechanisms of tissue regeneration employed by the DS used. These results suggest that this approach may be a viable one-stage treatment in clinical practice.

Hybrid Polyester-Hydrogel Electrospun Scaffolds for Tissue Engineering Applications

Electrospinning is an attractive fabrication process providing a cost-effective and straightforward technic to make extra-cellular matrix (ECM) mimicking scaffolds that can be used to replace or repair injured tissues and organs. Synthetic polymers as poly (ε-caprolactone) (PCL) and poly (ethylene oxide terephthalate)-poly(butylene terephthalate) (PEOT/PBT) have been often used to produce scaffolds due to their good processability, mechanical properties, and suitable biocompatibility. While synthetic polymers can mimic the physical features of native ECM, natural polymers like alginate are better suited to recapitulate its hydrated state or introduce functional groups that are recognized by cells (e.g., -NH2). Thus, this study aims at creating electrospun meshes made of blended synthetic and natural polymers for tissue engineering applications. Polyethylene oxide (PEO), PCL, and PEOT/PBT were used as a carrier of Alginate. Scaffolds were electrospun at different flow rates and distances between spinneret and collector (air gap), and the resulting meshes were characterized in terms of fiber morphology, diameter, and mesh inter-fiber pore size. The fiber diameter increased with increasing flow rate, while there was no substantial influence of the air gap. On the other hand, the mesh pore size increased with increasing air gap, while the effect of flow rate was not significant. Cross-linking and washing of alginate electrospun scaffolds resulted in smaller fiber diameter. These newly developed scaffolds may find useful applications for tissue engineering strategies as they resemble physical and chemical properties of tissue ECM. Human Dermal Fibroblasts were cultured on PCL and PCL/Alginate scaffolds in order to create a dermal substitute.

Skin wound repair: Results of a pre-clinical study to evaluate electropsun collagen-elastin-PCL scaffolds as dermal substitutes

The gold standard treatment for severe burn injuries is autologous skin grafting and the use of commercial dermal substitutes. However, resulting skin tissue following treatment usually displays abnormal morphology and functionality including scarring, skin contracture due to the poor elasticity and strength of existing dermal substitutes. In this study, we have developed a triple-polymer scaffold made of collagen-elastin-polycaprolactone (CEP) composite, aiming to enhance the mechanical properties of the scaffold while retaining its biological properties in promoting cell attachment, proliferation and tissue regeneration. The inclusion of elastin was revealed to decrease the stiffness of the scaffold, while also decreasing hysteresis and increasing elasticity. In mice, electrospun collagen-elastin-PCL scaffolds promoted keratinocyte and fibroblast proliferation, tissue integration and accelerated early-stage angiogenesis. Only a mild inflammatory response was observed in the first 2 weeks post-subcutaneous implantation. Our data indicates that the electrospun collagen-elastin-PCL scaffolds could potentially serve as a skin substitute to promote skin cell growth and tissue regeneration after severe burn injury.

Extracellular Matrix as a Regulator of Epidermal Stem Cell Fate

Epidermal stem cells reside within the specific anatomic location, called niche, which is a microenvironment that interacts with stem cells to regulate their fate. Regulation of many important processes, including maintenance of stem cell quiescence, self-renewal, and homeostasis, as well as the regulation of division and differentiation, are common functions of the stem cell niche. As it was shown in multiple studies, extracellular matrix (ECM) contributes a lot to stem cell niches in various tissues, including that of skin. In epidermis, ECM is represented, primarily, by a highly specialized ECM structure, basement membrane (BM), which separates the epidermal and dermal compartments. Epidermal stem cells contact with BM, but when they lose the contact and migrate to the overlying layers, they undergo terminal differentiation. When considering all of these factors, ECM is of fundamental importance in regulating epidermal stem cells maintenance, proper mobilization, and differentiation. Here, we summarize the remarkable progress that has recently been made in the research of ECM role in regulating epidermal stem cell fate, paying special attention to the hair follicle stem cell niche. We show that the destruction of ECM components impairs epidermal stem cell morphogenesis and homeostasis. A deep understanding of ECM molecular structure as well as the development of in vitro system for stem cell maintaining by ECM proteins may bring us to developing new approaches for regenerative medicine.

Bryostatin and its synthetic analog, picolog rescue dermal fibroblasts from prolonged stress and contribute to survival and rejuvenation of human skin equivalents

Skin health is associated with the day-to-day activity of fibroblasts. The primary function of fibroblasts is to synthesize structural proteins, such as collagen, extracellular matrix proteins, and other proteins that support the structural integrity of the skin and are associated with younger, firmer, and more elastic skin that is better able to resist and recover from injury. At sub-nanomolar concentrations (0.03-0.3 nM), bryostatin-1 and its synthetic analog, picolog (0.1-10 nM) sustained the survival and activation of human dermal fibroblasts cultured under the stressful condition of prolonged serum deprivation. Bryostatin-1 treatment stabilized human skin equivalents (HSEs), a bioengineered combination of primary human skin cells (keratinocytes and dermal fibroblasts) on an extracellular matrix composed of mainly collagen. Fibroblasts activated by bryostatin-1 protected the structural integrity of HSEs. Bryostatin-1 and picolog prolonged activation of Erk in fibroblasts to promote cell survival. Chronic stress promotes the progression of apoptosis. Dermal fibroblasts constitutively express all components of Fas associated apoptosis, including caspase-8, an initiator enzyme of apoptosis. Prolong bryostatin-1 treatment reduced apoptosis by decreasing caspase-8 and protected dermal fibroblasts. Our data suggest that bryostatin-1 and picolog could be useful in anti-aging skincare, and could have applications in tissue engineering and regenerative medicine.

To Control Site-Specific Skin Gene Expression, Autocrine Mimics Paracrine Canonical Wnt Signaling and Is Activated Ectopically in Skin Disease

Despite similar components, the heterogeneity of skin characteristics across the human body is enormous. It is classically believed that site-specific fibroblasts in the dermis control postnatal skin identity by modulating the behavior of the surface-overlying keratinocytes in the epidermis. To begin testing this hypothesis, we characterized the gene expression differences between volar (ventral; palmoplantar) and nonvolar (dorsal) human skin. We show that KERATIN 9 (KRT9) is the most uniquely enriched transcript in volar skin, consistent with its etiology in genetic diseases of the palms and soles. In addition, ectopic KRT9 expression is selectively activated by volar fibroblasts. However, KRT9 expression occurs in the absence of all fibroblasts, although not to the maximal levels induced by fibroblasts. Through gain-of-function and loss-of-function experiments, we demonstrate that the mechanism is through overlapping paracrine or autocrine canonical WNT-β-catenin signaling in each respective context. Finally, as an in vivo example of ectopic expression of KRT9 independent of volar fibroblasts, we demonstrate that in the human skin disease lichen simplex chronicus, WNT5a and KRT9 are robustly activated outside of volar sites. These results highlight the complexities of site-specific gene expression and its disruption in skin disease.

Dermal Contributions to Human Interfollicular Epidermal Architecture and Self-Renewal

The human interfollicular epidermis is renewed throughout life by populations of proliferating basal keratinocytes. Though interfollicular keratinocyte stem cells have been identified, it is not known how self-renewal in this compartment is spatially organized. At the epidermal-dermal junction, keratinocytes sit atop a heterogeneous mix of dermal cells that may regulate keratinocyte self-renewal by influencing local tissue architecture and signalling microenvironments. Focusing on the rete ridges and complementary dermal papillae in human skin, we review the identity and organisation of abundant dermal cells types and present evidence for interactions between the dermal microenvironment and the interfollicular keratinocytes.

Potential Skin Regeneration Activity and Chemical Composition of Absolute from Pueraria thunbergiana Flower

The flower of Pueraria thunbergiana BENTH (PTBF) contains isoflavonoids and essential oil components. It has many biological and pharmacological activities, including anti-diabetes, anti-oxidant, and weight loss. However, its effect on skin regeneration remains unknown. In the present study, we isolated the absolute from PTBF through solvent extraction and determined the role of the absolute on skin regeneration-associated responses in human epidermal-keratinocytes (HaCats). The PTBF absolute, which contained 10 compounds, stimulated migration and proliferation and increased the phosphorylation of serine/threonine-specific protein kinase and extracellular signal-regulated kinase1/2 in HaCats. It induced type I and IV collagen synthesis in HaCats. In addition, treatment with PTBF absolute resulted in increased sprout outgrowth in HaCats. These findings suggest that PTBF absolute may participate in skin regeneration, probably through promotion of migration, proliferation, and collagen synthesis.

Dermal fibroblast expression of stromal cell-derived factor-1 (SDF-1) promotes epidermal keratinocyte proliferation in normal and diseased skin

Stromal cells provide a crucial microenvironment for overlying epithelium. Here we investigated the expression and function of a stromal cell-specific protein, stromal cell-derived factor-1 (SDF-1), in normal human skin and in the tissues of diseased skin. Immunohistology and laser capture microdissection (LCM)-coupled quantitative real-time RT-PCR revealed that SDF-1 is constitutively and predominantly expressed in dermal stromal cells in normal human skin in vivo. To our surprise, an extremely high level of SDF-1 transcription was observed in the dermis of normal human skin in vivo, evidenced by much higher mRNA expression level than type I collagen, the most abundant and highly expressed protein in human skin. SDF-1 was also upregulated in the tissues of many human skin disorders including psoriasis, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC). Double immunostaining for SDF-1 and HSP47 (heat shock protein 47), a marker of fibroblasts, revealed that fibroblasts were the major source of stroma-cell-derived SDF-1 in both normal and diseased skin. Functionally, SDF-1 activates the ERK (extracellular-signal-regulated kinases) pathway and functions as a mitogen to stimulate epidermal keratinocyte proliferation. Both overexpression of SDF-1 in dermal fibroblasts and treatment with rhSDF-1 to the skin equivalent cultures significantly increased the number of keratinocyte layers and epidermal thickness. Conversely, the stimulative function of SDF-1 on keratinocyte proliferation was nearly completely eliminated by interfering with CXCR4, a specific receptor of SDF-1, or by knock-down of SDF-1 in fibroblasts. Our data reveal that extremely high levels of SDF-1 provide a crucial microenvironment for epidermal keratinocyte proliferation in both physiologic and pathologic skin conditions.

Stimulatory effect of fibroblast-derived prostaglandin E₂ on keratinocyte stratification in the skin equivalent

Epidermal-dermal interaction plays important roles in physiological events such as wound healing. In this study, we examined a double paracrine mechanism between keratinocytes and fibroblasts through interleukin-1 (IL-1) and an IL-1-induced inflammatory mediator prostaglandin E₂ (PGE₂) using the skin equivalent. The epidermal layer of the skin equivalent expressed high levels of IL-1α mRNA (IL1A mRNA) and relatively low levels of IL-1β mRNA (IL1B mRNA). IL1A mRNA was not detected in fibroblasts. Fibroblasts also expressed low but not negligible levels of IL1B mRNA only in the presence of keratinocytes. Expression of prostaglandin-endoperoxide synthase 2 mRNA (PTGS2 mRNA) and production of PGE₂ in three-dimensionally cultured fibroblasts were noticeably stimulated by co-culture with keratinocytes, whereas PTGS2 mRNA expression in the epidermal layer was very low. In addition, hydroxyprostaglandin dehydrogenase 15-(NAD) mRNA was highly expressed in keratinocytes but not in fibroblasts, and exogenous IL-1β stimulated PTGS2 mRNA expression in the dermal equivalent. The thickness of the epidermal layer and the number of MKI67-positive keratinocytes in the skin equivalent were decreased by treatment with indomethacin, and the decrease recovered when exogenous PGE₂ was added. These results indicate that keratinocytes stimulate their own proliferation through a double paracrine mechanism mediated by IL-1 and PGE₂.

Altered immunohistochemical expression of mast cell tryptase and chymase in the pathogenesis of oral submucous fibrosis and malignant transformation of the overlying epithelium

Mast cells (MCs) expressing serine proteases; tryptase and chymase, are associated with fibrosis in various diseases. However, little is known about their involvement in oral submucous fibrosis (OSF). Our goal was to evaluate the role of MC tryptase and chymase in the pathogenesis of OSF and its malignant transformation. Immunohistochemical expression of MC tryptase and chymase was evaluated in 20 cases of OSF, 10 cases of oral squamous cell carcinoma (OSCC) and 10 cases of healthy controls. Subepithelial zone of Stage 1 and 2 while deep zone of Stage 3 and 4 OSF demonstrated increased tryptase positive MCs. OSCC revealed a proportionate increase in tryptase and chymase positive MCs irrespective of areas of distribution. An altered balance in the subepithelial and deep distribution of tryptase and chymase positive MCs play an important role in the pathogenesis of OSF and its malignant transformation.

Three-dimensional pore structure analysis of polycaprolactone nano-microfibrous scaffolds using theoretical and experimental approaches

In this article the pore structure and porosity parameters of polycaprolactone (PCL) nano-microfibrous scaffolds are investigated using a predicting theoretical model and a nondestructive evaluation approach based on confocal laser scanning microscopy (CLSM) and three-dimensional image analysis. Different fibrous scaffolds with different fiber diameters produced by electrospinning process and their 3D-pore structure were evaluated theoretically and also compared to results of CLSM and capillary flow porometery methods. The effect of polymer concentration on the pore structure of scaffolds was also investigated. The results showed that, the introduced approach not only can measure the pore size distribution of nanofibrous scaffolds, but also can measure pore interconnectivity of fibrous scaffolds. Furthermore, the results showed that increasing the fiber diameter resulted from increasing the polymer concentration in solvent can effectively increase the pore dimensions within the scaffold structure.

Stiffness-modulated water retention and neovascularization of dermal fibroblast-encapsulating collagen gel

There is increasing evidence that matrix stiffness modulates various phenotypic activities of cells surrounded by a three-dimensional (3D) matrix. These findings suggest that matrix stiffness can also regulate dermal fibroblasts activities to remodel, repair, and recreate skin dermis, but this has not yet been systematically demonstrated to date. This study examines the effects of matrix rigidity on the morphology, growth rates, and glycosaminoglycan (GAG) production of dermal fibroblasts cultured in collagen-based hydrogels with controlled elastic moduli. The elastic moduli (E) of collagen hydrogels were increased from 0.7 to 1.6 and 2.2  kPa by chemically cross-linking collagen fibrils with poly(ethylene glycol) disuccinimidylester. Increasing E of the hydrogel led to decreases in cellular spreading, nuclear aspect ratio, and growth rate. In contrast, the cellular GAG production level was elevated by increasing E from 0.7 to 1.6  kPa. The larger accumulation of GAG in the stiffer hydrogel led to increased water retention during exposure to air, as confirmed with magnetic resonance imaging. Additionally, in a chicken chorioallantoic membrane, a cell-encapsulating hydrogel with E of 1.6  kPa created dermis-like tissue with larger amount of GAG and density of blood vessels, while a cell-hydrogel construct with E of 0.7  kPa generated scar-like tissue. Overall, the results of this study will be highly useful for designing advanced tissue engineering scaffolds that can enhance the quality of a wide array of regenerated tissues including skin.

A theoretical analysis and prediction of pore size and pore size distribution in electrospun multilayer nanofibrous materials

Electrospinning process can fabricate nanomaterials with unique nanostructures for potential biomedical and environmental applications. However, the prediction and, consequently, the control of the porous structure of these materials has been impractical due to the complexity of the electrospinning process. In this research, a theoretical model for characterizing the porous structure of the electrospun nanofibrous network has been developed by combining the stochastic and stereological probability approaches. From consideration of number of fiber-to-fiber contacts in an electrospun nanofibrous assembly, geometrical and statistical theory relating morphological and structural parameters of the network to the characteristic dimensions of interfibers pores is provided. It has been shown that these properties are strongly influenced by the fiber diameter, porosity, and thickness of assembly. It is also demonstrated that at a given network porosity, increasing fiber diameter and thickness of the network reduces the characteristic dimensions of pores. It is also discussed that the role of fiber diameter and number of the layer in the assembly is dominant in controlling the pore size distribution of the networks. The theory has been validated experimentally and results compared with the existing theory to predict the pore size distribution of nanofiber mats. It is believed that the presented theory for estimation of pore size distribution is more realistic and useful for further studies of multilayer random nanofibrous assemblies.

Assessment of Spirulina-PCL nanofiber for the regeneration of dermal fibroblast layers

Skin is a barrier which protects injured tissues, and thus, skin regeneration is one of many important medical issues. Tissue engineering is an attractive approach to make artificial tissue or regenerate lost tissues. While constituting artificial tissues, cells must infiltrate through scaffolds, maintaining viability and proliferation. However, a three-dimensional tissue culture involves stressful environments due to several reasons such as mass or gas transport and high cell density. Once stressed, cells produce reactive oxygen species, resulting in alleviating cellular viability and activity. Spirulina is well known to have antioxidant molecules, which have been known to modulate oxidative stress to cells. Electrospun nanofiber has widely been used as a scaffold to mimic natural extracellular matrix. In this research, we assessed Spirulina extract-imbedded nanofiber as a scaffold for an artificial skin tissue. Spirulina extract was proven to positively affect viability and proliferation of mouse fibroblasts. In addition, fibroblasts infiltrated through Spirulina extract-imbedded electrospun nanofiber without cytotoxicity.

Enhanced keratinocyte proliferation and migration in co-culture with fibroblasts

Wound healing is primarily controlled by the proliferation and migration of keratinocytes and fibroblasts as well as the complex interactions between these two cell types. To investigate the interactions between keratinocytes and fibroblasts and the effects of direct cell-to-cell contact on the proliferation and migration of keratinocytes, keratinocytes and fibroblasts were stained with different fluorescence dyes and co-cultured with or without transwells. During the early stage (first 5 days) of the culture, the keratinocytes in contact with fibroblasts proliferated significantly faster than those not in contact with fibroblasts, but in the late stage (11(th) to 15(th) day), keratinocyte growth slowed down in all cultures unless EGF was added. In addition, keratinocyte migration was enhanced in co-cultures with fibroblasts in direct contact, but not in the transwells. Furthermore, the effects of the fibroblasts on keratinocyte migration and growth at early culture stage correlated with heparin-binding EGF-like growth factor (HB-EGF), IL-1α and TGF-β1 levels in the cultures where the cells were grown in direct contact. These effects were inhibited by anti-HB-EGF, anti-IL-1α and anti-TGF-β1 antibodies and anti-HB-EGF showed the greatest inhibition. Co-culture of keratinocytes and IL-1α and TGF-β1 siRNA-transfected fibroblasts exhibited a significant reduction in HB-EGF production and keratinocyte proliferation. These results suggest that contact with fibroblasts stimulates the migration and proliferation of keratinocytes during wound healing, and that HB-EGF plays a central role in this process and can be up-regulated by IL-1α and TGF-β1, which also regulate keratinocyte proliferation differently during the early and late stage.

Primary human dermal fibroblast interactions with open weave three-dimensional scaffolds prepared from synthetic human elastin

We present an elastic, fibrous human protein-based and cell-interactive dermal substitute scaffold based on synthetic human elastin. Recombinant human tropoelastin promoted primary human dermal fibroblast attachment, spreading and proliferation. Tropoelastin was cross-linked to form a synthetic elastin (SE) hydrogel matrix and electrospun into fibrous SE scaffolds. Fibroblasts attached to and proliferated across SE hydrogel scaffold surfaces for at least 14 days and deposited the extracellular matrix proteins fibronectin and collagen type I. To allow for the benefit of greater cell infiltration, SE was electrospun into open weave, fibrous scaffolds that closely mimic the fibrous nature of the skin dermis. 3D SE scaffolds were robust and consisted of flat, ribbon-like fibers with widths that are similar to native dermal elastic fibers. The scaffolds displayed elasticity close to that of natural elastin. 3D SE retained the ability to interact with primary human dermal fibroblasts, which consistently attached and proliferated to form monolayers spanning the entire scaffold surface. The open weave design, with larger spaces between individual fibers and greater fiber diameters beneficially allowed for substantial cell infiltration throughout the scaffolds.

Hepatoma-derived growth factor and its role in keloid pathogenesis

Hepatoma-derived growth factor (HDGF) is a novel mitogenic growth factor that has been implicated in many different carcinomas. Its role in keloid biology has not yet been investigated. The present study is aimed at examining the role of HDGF in keloid pathogenesis. Immunohistochemical staining and Western blot analyses were used to examine in vivo localization and expression of HDGF in keloid and normal skin tissue. This was followed by the detection of HDGF expression in fibroblasts cultured in vitro and fibroblasts exposed to serum. To investigate the effect of epithelial–mesenchymal interactions, a two-chamber system was employed in which keratinocytes on membrane inserts were co-cultured with the fibroblasts. HDGF expression levels in all cell extracts and conditioned media were assayed through Western blot analysis. In another set of experiments, the effect of exogenous recombinant HDGF on keloid fibroblasts (KF) and normal fibroblasts (NF) was examined. Cell proliferation was assessed by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and by quantifying proliferating cell nuclear antigen (PCNA) expression. Downstream targets of HDGF were identified by detecting their expression through Western blot analysis. Our results indicate that there was an increase in HDGF expression in the dermis of keloid compared with normal skin tissue. The application of serum and epithelial–mesenchymal interactions did not seem to have any effect on intracellular HDGF expression levels. However, co-culturing keloid keratinocytes with KFs resulted in increased HDGF secretion when compared with monoculture or normal controls. Furthermore, treatment with exogenous recombinant HDGF was found to increase the proliferation of KFs, activate the extracellular signal-regulated kinase (ERK) pathway and up-regulate the secretion of vascular endothelial growth factor (VEGF).

Expression of heat shock protein receptors on fibroblast-like synovial cells derived from rheumatoid arthritis-affected joints

We examined the membrane expression of inducible Hsp70 and HSP receptors like TLR2, TLR4, CD14, CD36, CD40 and CD91 on fibroblast-like synovial cells (SC) derived from synovial tissue in 23 patients with rheumatoid arthritis (RA), who underwent synovectomy by using flow cytometric analysis. For comparison, autologous skin fibroblasts (SF) derived from the operation wound were tested. Significantly higher Hsp70 expression was found on synovial cells than on skin fibroblasts (median SC 21.4% x SF 5.0%, P < 0.001). Both synovial cells and skin fibroblasts expressed high levels of cell surface CD91 (median SC 80.2% x SF 79.2%), however, no or low levels of CD14, CD40, TLR2, TLR4 and CD36. Further, we observed high co-expression of CD91 and Hsp70 on RA synovial cells (median 18.6%), while skin fibroblasts showed only background Hsp70 expression (median 3.9%, P < 0.001). Since we demonstrated the high prevalence of inducible Hsp70 in RA synovial fluids, we speculate that Hsp70 might be captured onto the membrane of synovial cells from the extracellular space via the CD91 receptor. The significance of the Hsp70 interaction with synovial cells via CD91 remains undefined, but may mediate other non-immune purposes.

Transforming growth factor-beta3 affects plasminogen activator inhibitor-1 expression in fetal mice and modulates fibroblast-mediated collagen gel contraction

For over two decades, the precise role of transforming growth factor-beta (TGF-beta) isoforms in scarless healing of mammalian fetal skin wounds has generated much interest. Although their exact role remains to be established, it has been suggested that high TGF-beta3 activity may correlate with a scarless phenotype. Previously, we showed that plasminogen activator inhibitor-1 (PAI-1), a known TGF-beta downstream molecule and marker of fibrosis, is also developmentally regulated during fetal skin development. In this study, the relationship between TGF-beta3 and PAI-1 was investigated using embryonic day 14.5 TGF-beta3 knockout (ko) mice. The results showed increased PAI-1 expression in the epidermis and dermis of ko mice, using an ex vivo limb-wounding study. Furthermore, increased PAI-1 expression and activity was seen in embryo extracts and conditioned media of ko dermal fibroblasts. When TGF-beta3 knockout fibroblasts were placed into three-dimensional collagen matrices, they were found to have decreased collagen gel contraction, suggesting altered cell-matrix interaction. These findings provide a further avenue for the interactive role of TGF-beta3 and PAI-1 during fetal scarless repair.

Human Skin and Gingival Keratinocytes Show Differential Regulation of Matrix Metalloproteinases When Combined With Fibroblasts in 3-Dimensional Cultures

BACKGROUND

Matrix metalloproteinases (MMP) and their inhibitors are expressed in tissues during interactions between keratinocytes and fibroblasts. Maintaining the balance between MMPs and their inhibitors is critical; failure to do so can lead to severe tissue damage or complete destruction, as seen in periodontal disease. Previously we showed that 3-dimensional (3-D) cultures of homotypically-combined skin and gingival cells mimicked the tissues in protein and lipid production, but heterotypic cultures did not.

METHODS

We examined the production and activation of MMPs in these homotypic and heterotypic combinations of skin and gingival keratinocytes and fibroblasts during the critical time that they reformed the tissues. Primary fibroblasts and keratinocytes were isolated from normal human gingiva and skin and grown in 3-D cultures for up to 42 days. MMP-1, MMP-2, and MMP-9 in the media and inhibition of MMPs from these cultures were analyzed.

RESULTS

These experiments determined that skin fibroblasts grown with skin or gingival keratinocytes secrete increased amounts of MMP-1 compared to gingival fibroblasts; that the interaction of keratinocytes with fibroblasts decreases the amount of MMP-2 produced by the fibroblasts in 3-D cultures; that skin keratinocytes, but not gingival keratinocytes, interact with fibroblasts to upregulate expression of the active form of MMP-9; and that medium conditioned by gingival 3-D cultures does not contain an inhibitor of MMP-9.

CONCLUSION

Varying the type of fibroblast beneath the keratinocytes allowed us to determine that skin and gingival keratinocytes differentially regulate the production and activation of MMP-9, but not MMP-2, a finding that could influence the success of tissue grafting after periodontal surgery.

Increased keratinocyte proliferation by JUN-dependent expression of PTN and SDF-1 in fibroblasts

In skin, fibroblasts of the connective tissue play a decisive role in epidermal homeostasis and repair by contributing to the regulation of keratinocyte proliferation and differentiation. The AP-1 transcription factor subunit JUN plays a crucial role in this mesenchymal-epithelial interplay by regulating the expression of two critical paracrine-acting cytokines, keratinocyte growth factor (KGF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). We have performed gene expression profiling of wild-type and Jun–/– mouse embryonic fibroblasts to identify additional players involved in this complex network, and have found pleiotrophin (PTN) and the stromal cell-derived factor 1 (SDF-1) as novel JUN-regulated factors. Both cytokines are expressed by dermal fibroblasts in vivo, as shown by semi-quantitative RT-PCR and in situ hybridization on murine skin sections. Using a heterologous feeder layer co-culture system, we demonstrated that PTN and SDF-1 exert a mitogenic effect on primary human keratinocytes. Moreover, SDF-1-induced keratinocyte proliferation could be specifically inhibited by neutralizing antibodies against SDF-1 or its receptor, CXCR4. Consistent with its role in promoting keratinocyte growth, PTN was upregulated during cutaneous wound healing in vivo. Interestingly, co-cultivation with keratinocytes stimulated PTN expression but repressed SDF-1 production in fibroblasts, demonstrating the complexity of the paracrine regulatory cytokine networks that control skin homeostasis and regeneration.

Fibroblasts improve performance of cultured composite skin substitutes on athymic mice

BACKGROUND

This study investigated the impact of adding human fibroblasts to a cultured composite skin substitute model of cultured human keratinocytes and acellular human dermis.

METHODS

Skin substitutes were prepared by seeding human keratinocytes on the papillary side of acellular dermis with or without seeding fibroblasts on the reticular side. Performance of the grafts was compared both in vitro by histology and in vivo on surgically created full-thickness wounds on athymic mice. Graft size and contraction were measured and immunohistochemical stains were done to reveal vascularization.

RESULTS

Skin substitutes with fibroblasts formed thicker epidermis than skin substitutes without fibroblasts. When transplanted onto athymic mice, skin substitutes with fibroblasts maintained their original size with only 2% contraction. In contrast, skin substitutes without fibroblasts showed 29% contraction. Vascular basement membrane specific mouse CD31staining and endothelial cell specific mouse collagen type IV staining revealed vascularization as early as 1 week posttransplant in grafts with fibroblasts, and was significantly higher than grafts without fibroblasts at 2 weeks.

CONCLUSIONS

Addition of fibroblasts to keratinocyte based composite skin substitutes improves epidermis formation, enhances vascularization and reduces contraction.

An in vitro outgrowth culture system for normal human keratinocytes

BACKGROUND

Normal human epidermal keratinocytes usually proliferate in low-calcium and differentiate in high-calcium without a feeder layer, but they stop proliferating and differentiate at confluency even in low-calcium, serum-free medium.

OBJECTIVE

We speculated that this contact inhibition would be mediated in part by mechanical tension. To prove this, we created a new assay system.

METHODS

A 10 mm diameter cloning ring was put on the center of a 60 mm dish coated with type I collagen. Keratinocytes were plated in the ring and incubated for 4h, then we had a circular epidermal monolayer sheet. We changed the mechanical tension by removing the ring and measured the diameter of the sheet under various conditions.

RESULTS

When we used keratinocyte-serum free medium (SFM) whose calcium concentration is below 0.1 mM as a medium, the keratinocytes in the perimeter migrated individually, and the keratinocytes in the center portion started differentiation. However, when we added calcium chloride to SFM (final concentration more than 0.5 mM), keratinocytes at the periphery showed marked lamellipodia without losing contact with the surrounding cells. These keratinocytes showed coordinate sheet-like outgrowth as a whole even in high concentrations of calcium.

CONCLUSION

These results suggest that other than calcium concentration, change of the mechanical tension would be one of the factors that mediate proliferation or differentiation of keratinocytes and that this new assay can be useful in analyzing proliferation, differentiation, and migration of keratinocytes.

Keratinocytes Promote Proliferation and Inhibit Apoptosis of the Underlying Fibroblasts: An Important Role in the Pathogenesis of Keloid

Interactions between epidermal keratinocytes and dermal fibroblasts play an important role in regulating tissue homeostasis and repair. Nevertheless, little is known about the role of keratinocytes in the pathogenesis of keloid. In this study, we investigated the influence of normal skin- and keloid-derived keratinocytes on normal skin- and keloid-derived fibroblasts utilizing a serum-free indirect coculture system. The keloid-derived fibroblasts showed a greater proliferation and minimal apoptosis when cocultured with normal skin- or keloid-derived keratinocytes, and the results were most significant in the latter. This difference was not observed when the fibroblasts were treated with conditioned medium obtained from normal skin- and keloid-derived keratinocytes. Nevertheless, conditioned medium-treated groups showed more proliferation and less apoptosis compared to the nonconditioned medium-treated control groups. We also analyzed the profile of factors involved in cell growth and apoptosis in fibroblasts cocultured with keratinocytes. Extracellular signal-regulated kinase and c-Jun N-terminal kinase phosphorylations and expression of Bcl-2 and transforming growth factor-beta1 were all significantly upregulated in the fibroblasts cocultured with keloid-derived keratinocytes. Together, these results strongly suggest that the overlying keratinocytes of the keloid lesion play an important role in keloidogenesis by promoting more proliferation and less apoptosis in the underlying fibroblasts through paracrine and double paracrine effects.

Increased plasminogen activator inhibitor-1 in keloid fibroblasts may account for their elevated collagen accumulation in fibrin gel cultures

Proteolytic degradation of the provisional fibrin matrix and subsequent substitution by fibroblast-produced collagen are essential features of injury repair. Immunohistochemical studies revealed that although dermal fibroblasts of normal scars and keloids expressed both urokinase type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1), keloid fibroblasts had a much higher PAI-1 expression. In long-term three-dimensional fibrin gel cultures (the in vitro fibroplasia model), normal fibroblasts expressed moderate and modulated activity levels of uPA and PAI-1. In contrast, keloid fibroblasts expressed a persistently high level of PAI-1 and a low level of uPA. The high PAI-1 activity of keloid fibroblasts correlated with their elevated collagen accumulation in fibrin gel cultures. Substituting collagen for fibrin in the gel matrix resulted in increased uPA activity and reduced collagen accumulation of keloid fibroblasts. Furthermore, decreasing PAI-1 activity of keloid fibroblasts in fibrin gel cultures with anti-PAI-1-neutralizing antibodies also resulted in a reduction in collagen accumulation by keloid fibroblasts. Cumulatively, these results suggest that PAI-1 overexpression is a consistent feature of keloid fibroblasts both in vitro and in vivo, and PAI-1 may play a causative role in elevated collagen accumulation of keloid fibroblasts.

Recapitulation of oral mucosal tissues in long-term organotypic culture

To test the influence of fibroblasts on epithelial morphology and expression of keratinocyte proteins and barrier lipids, we bioengineered homotypic and heterotypic oral mucosae and skin using cultured adult human cells. Fibroblasts were allowed to modify collagen type I gels for 2 weeks before keratinocytes were added. The organotypic cultures were then grown at the air-liquid interface for 4 weeks. In homotypic combinations, epithelial morphology and protein expression closely mimicked those in vivo. In heterotypic combinations, the morphology resembled that in vivo and keratinocytes expressed their typical markers, except when skin keratinocytes were recombined with alveolar fibroblasts; they expressed K19, K4, and K13, which is similar to oral mucosal epithelia rather than to the epidermis. Morphologically, the stratum corneum layers were typical for the epithelial tissues. Grafting the bioengineered cultures to the backs of Nude mice did not change the results, suggesting that our findings are not merely a culture phenomenon. Lipid profiles of the homotypic combinations mimicked the profiles found in the normal epithelial tissues, except that the engineered alveolar epithelium expressed more ceramide 2 than that in vivo. In the heterotypic combinations, keratinocytes appeared to control the lipid profile, except in the combination of skin keratinocytes with alveolar fibroblasts, wherein the ceramide profile appeared to be partly that of alveolar epithelium and partly that of epidermis. These results suggest that cultured adult fibroblasts and keratinocytes are sufficient to recapitulate graftable oral tissues, and, except for alveolar fibroblasts, the type of fibroblast had little influence on keratinocyte differentiation.

Tumor necrosis factor-alpha-induced proteolytic activation of pro-matrix metalloproteinase-9 by human skin is controlled by down-regulating tissue inhibitor of metalloproteinase-1 and mediated by tissue-associated chymotrypsin-like proteinase

The proteolytic activation of pro-matrix metalloproteinase (MMP)-9 by conversion of the 92-kDa precursor into an 82-kDa active form has been observed in chronic wounds, tumor metastasis, and many inflammation-associated diseases, yet the mechanistic pathway to control this process has not been identified. In this report, we show that the massive expression and activation of MMP-9 in skin tissue from patients with chronically unhealed wounds could be reconstituted in vitro with cultured normal human skin by stimulation with transforming growth factor-beta and tumor necrosis factor (TNF)-alpha. We dissected the mechanistic pathway for TNF-alpha induced activation of pro-MMP-9 in human skin. We found that proteolytic activation of pro-MMP-9 was mediated by a tissue-associated chymotrypsin-like proteinase, designated here as pro-MMP-9 activator (pM9A). This unidentified activator specifically converted pro-MMP-9 but not pro-MMP-2, another member of the gelatinase family. The tissue-bound pM9A was steadily expressed and not regulated by TNF-alpha, which indicated that the cytokine-mediated activation of pro-MMP-9 might be regulated at the inhibitor level. Indeed, the skin constantly secreted tissue inhibitor of metalloproteinase-1 at the basal state. TNF-alpha, but not transforming growth factor-beta, down-regulated this inhibitor. The TNF-alpha-mediated activation of pro-MMP-9 was tightly associated with down-regulation of tissue inhibitor of metalloproteinase-1 in a dose-dependent manner. To establish this linkage, we demonstrate that the recombinant tissue inhibitor of metalloproteinase-1 could block the activation of pro-MMP-9 by either the intact skin or skin fractions. Thus, these studies suggest a novel regulation for the proteolytic activation of MMP-9 in human tissue, which is mediated by tissue-bound activator and controlled by down-regulation of a specific inhibitor.

Characterization of collagen gel solutions and collagen matrices for cell culture

The influence of glutaraldehyde as a crosslinking agent to increase the strength of collagen matrices for cell culture was examined in this study. Collagen solutions of 1% were treated with different concentrations (0-0.2%) of glutaraldehyde for 24 h. The viscoelasticity of the resulting collagen gel solution was measured using dynamic mechanical analysis (DMA), which demonstrated that all collagen gel solutions examined followed the same model pattern. The creep compliance model of Voigt-Kelvin satisfactorily described the change of viscoelasticity expressed by these collagen gel solutions. These crosslinked collagen gel solutions were freeze-dried to form a matrix with a thickness of about 0.2-0.3 mm. The break modulus of these collagen matrices measured by DMA revealed that the higher the degree of crosslinking. the higher the break modulus. The compatibility of fibroblasts isolated from nude mouse skin with these collagen matrices was found to be acceptable at a cell density of 3 x 10(5) cells/cm2 with no contraction, even when using a concentration of glutaraldehyde of up to 0.2%.

TNF-alpha stimulates activation of pro-MMP2 in human skin through NF-(kappa)B mediated induction of MT1-MMP

Tumor necrosis factor-alpha (TNF-(alpha)) is an important mediator during the inflammatory phase of wound healing. Excessive amounts of pro-inflammatory cytokines such as TNF-(alpha) are associated with inflammatory diseases including chronic wounds. Matrix metalloproteinases (MMPs) are involved in matrix re-modeling during wound healing, angiogenesis and tumor metastasis. As with pro-inflammatory cytokines, high levels of MMPs have been found in inflammatory states such as chronic wounds. In this report we relate these two phenomena. TNF-(alpha) stimulates secretion of active MMP-2, a type IV collagenase, in organ-cultured full-thickness human skin. This suggests a mechanism whereby excess inflammation affects normal wound healing. To investigate this observation at the cellular and molecular levels, we examined TNF-(alpha) mediated activation of pro-MMP-2, induction of MT1-MMP, and the intracellular signaling pathways that regulate the proteinase in isolated human dermal fibroblasts. We found that TNF-(alpha) substantially promoted activation of pro-MMP-2 in dermal fibroblasts embedded in type-I collagen. In marked contrast, collagen or TNF-(alpha) individually had little influence on the fibroblast-mediated pro-MMP-2 activation. One well-characterized mechanism for pro-MMP-2 activation is through a membrane type matrix metalloproteinase, such as MT1-MMP. We report that TNF-(alpha) significantly induced MT1-MMP at the mRNA and protein levels when the dermal fibroblasts were grown in collagen. Although the intracellular signaling pathway regulating mt1-mmp gene expression is still obscure, both TNF-(alpha) and collagen activate the NF-(kappa)B pathway. In this report we provide three sets of evidence to support a hypothesis that activation of NF-(kappa)B is essential to induce MT1-MMP expression in fibroblasts after TNF-(alpha) exposure. First, SN50, a peptide inhibitor for NF-(kappa)B nuclear translocation, simultaneously blocked the TNF-(alpha) and collagen mediated MT1-MMP induction and pro-MMP-2 activation. Secondly, TNF-(alpha) induced I(kappa)B to breakdown in fibroblasts within the collagen lattice, a critical step leading to NF-(kappa)B activation. Lastly, a consensus binding site for p65 NF-(kappa)B (TGGAGCTTCC) was found in the 5′-flanking region of human mt1-mmp gene. Based on these results and previous reports, we propose a model to explain TNF-(alpha) activation of MMP-2 in human skin. Activation of NF(kappa)B signaling in fibroblasts embedded in collagen induces mt1-mmp gene expression, which subsequently activates the pro-MMP-2. The findings provide a specific mechanism whereby TNF-(alpha) may affect matrix remodeling during wound healing and other physiological and pathological processes.

Higher numbers of autologous fibroblasts in an artificial dermal substitute improve tissue regeneration and modulate scar tissue formation

Cultured skin substitutes are increasingly important for the treatment of burns and chronic wounds. The role of fibroblast numbers present in a living-skin equivalent is at present unknown. The quality of dermal tissue regeneration was therefore investigated in relation to the number of autologous fibroblasts seeded in dermal substitutes, transplanted instantaneously or precultured for 10 days in the substitute. A full-thickness porcine wound model was used to compare acellular dermal substitutes (ADS) with dermal substitutes seeded with fibroblasts at two densities, 1x10(5) (0-DS10) and 5x10(5) cells/cm(2) (0-DS50), and with dermal substitutes seeded 10 days before operation at the same densities (10-DS10 and 10-DS50) (n=7 for each group, five pigs). After transplantation of the dermal substitutes, split-skin mesh grafts were applied on top. Wound healing was evaluated blind for 6 weeks. Cosmetic appearance was evaluated and wound contraction was measured by planimetry. The wound biopsies taken after 3 weeks were stained for myofibroblasts (alpha-smooth muscle actin), and after 6 weeks for scar tissue formation (collagen bundles organized in parallel and the absence of elastin staining). Collagen maturation was investigated with polarized light. For wound cosmetic parameters, the 10-DS50 and 0-DS50 treatments scored significantly better than the ADS treatment, as did the 10-DS50 treatment for wound contraction (p<0.05, paired t-test). Three weeks after wounding, the area with myofibroblasts in the granulation tissue, determined by image analysis, was significantly smaller for 0-DS50, 10-DS10, and 10-DS50 than for the ADS treatment (p<0.04, paired t-test). After 6 weeks, the wounds treated with 0-DS50, 0-DS10, and 10-DS50 had significantly less scar tissue and significantly more mature collagen bundles in the regenerated dermis. This improvement of wound healing was correlated with the higher numbers of fibroblasts present in the dermal substitute at the moment of transplantation. In conclusion, dermal regeneration of experimental full-skin defects was significantly improved by treatment with dermal substitutes containing high numbers of (precultured) autologous fibroblasts.

Development and characterization of a tissue-engineered human oral mucosa equivalent produced in a serum-free culture system

A problem maxillofacial surgeons face is a lack of sufficient autogenous oral mucosa for reconstruction of the oral cavity. Split-thickness or oral mucosa grafts require more than one surgical procedure and can result in donor site morbidity. Skin has disadvantages of adnexal structures and a different keratinization pattern than oral mucosa. In this study, we successfully assembled, ex vivo, a human oral mucosa equivalent, consisting of epidermal and dermal components, in a defined, essential-fatty-acid-deficient, serum-free culture medium without a feeder layer, that could be used for intra-oral grafting in humans. Autogenous oral keratinocytes were seeded onto a cadaveric dermis, AlloDerm. The oral mucosa equivalent was cultured at an air-liquid interface for 2 wks. The resulting equivalent had a well-stratified parakeratinized epithelial layer similar to native oral keratinized mucosa. Expression of differentiation markers, filaggrin and cytokeratin 10/13, suggested a premature keratinized state. The presence of proliferation markers, proliferating cell nuclear antigen (PCNA) and Ki-67, suggested a state of hyperproliferation. Fatty acid composition of the equivalent was similar to that of in vitro cultured oral keratinocytes but differed from the that of in vivo native tissue, showing a lower content of 18:2 and 20:4, and a higher content of 16:1 and 18:1 fatty acids, respectively. The keratinocytes of the equivalent appeared to be in a more active and proliferative state than native keratinized mucosa. The dynamic nature of the cell population on the oral mucosa equivalent may be beneficial for intra-oral grafting procedures and for transfection of the keratinocytes.

Living skin substitutes: survival and function of fibroblasts seeded in a dermal substitute in experimental wounds

The healing of full-thickness skin defects requires extensive synthesis and remodeling of dermal and epidermal components. Fibroblasts play an important role in this process and are being incorporated in the latest generation of artificial dermal substitutes. We studied the fate of fibroblasts seeded in our artificial elastin/collagen dermal substitute and the influence of the seeded fibroblasts on cell migration and dermal substitute degradation after transplantation to experimental full-thickness wounds in pigs. Wounds were treated with either dermal substitutes seeded with autologous fibroblasts or acellular substitutes. Seeded fibroblasts, labeled with a PKH-26 fluorescent cell marker, were detected in the wounds with fluorescence microscopy and quantitated with flow cytofluorometric analysis of single-cell suspensions of wound tissue. The cellular infiltrate was characterized for the presence of mesenchymal cells (vimentin), monocytes/macrophages, and vascular cells. Dermal substitute degradation was quantitated by image analysis of wound sections stained with Herovici's staining. In the wounds treated with the seeded dermal substitute, fluorescent PKH-26-labeled cells were detectable up to 6 d and were positive for vimentin but not for the macrophage antibody. After 5 d, flow cytofluorometry showed the presence of 3.1 (+/-0.9) x 10(6) (mean +/- SD, n = 7) PKH-26-positive cells in these wounds, whereas initially only 1 x 10(6) fluorescent fibroblasts had been seeded. In total, the percentage of mesenchymal cells minus the macrophages was similar after 5 d between wounds treated with the seeded and the acellular substitutes. In the wounds treated with the seeded substitute, however, 19.5% of the mesenchymal cells were of seeded origin. Furthermore, the rate of substitute degradation in the seeded wounds was significantly lower at 2-4 wk after wounding than in wounds treated with the acellular substitute. Vascular in-growth and the number of infiltrated macrophages were not different. In conclusion, cultured dermal fibroblasts seeded in an artificial dermal substitute and transplanted onto full-thickness wounds in pigs survived and proliferated. The observed effects of seeded fibroblasts on dermal regeneration appeared to be mediated by reducing subcutaneous fibroblastic cell migration and/or proliferation into the wounds without impairing migration of monocytes/macrophages and endothelial cells. Moreover, the degradation of the implanted dermal substitute was retarded, indicating a protective activity of the seeded fibroblasts.

Scleroderma fibroblasts promote migration of mononuclear leucocytes across endothelial cell monolayers

Perivascular infiltrates of inflammatory cells are a hallmark of lesional skin in scleroderma. We have explored the potential for scleroderma fibroblasts to modulate mononuclear leucocyte migration across endothelial cell monolayers in tissue culture, and to regulate expression of endothelial cell adhesion molecules. Fibroblasts were grown from skin biopsies of eight patients with active diffuse cutaneous scleroderma and from four healthy controls. Co-culture and conditioned medium transfer experiments examined the effect of soluble fibroblast products on mononuclear leucocyte (U937) cell migration across endothelial cell (1E-7) monolayers grown on tissue culture inserts. Co-culture of scleroderma, but not control fibroblasts, promoted transendothelial migration of U937 cells. Scleroderma fibroblast-conditioned medium had qualitatively similar effects and equivalent results were obtained using Jurkat-6 (T lymphocyte) cells, and with peripheral blood mononuclear cells from a patient with diffuse cutaneous scleroderma. Promotion of leucocyte migration does not appear to result from increased endothelial adhesion molecule expression, since fibroblast-conditioned medium did not up-regulate endothelial cell expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) or E-selectin. Moreover, leucocyte migration across cytokine-activated endothelial cell layers in co-culture with fibroblasts was less than across resting cells, although the selective effect of scleroderma fibroblast co-culture persisted. Recombinant monocyte chemoattractant protein-1 (MCP-1) or IL-8 increased passage of mononuclear leucocytes across endothelial cell monolayers, whilst anti-MCP-1, but not anti-IL-8 antibodies, significantly reduced the effect of fibroblast conditioned medium. These data suggest that systemic sclerosis (SSc) fibroblasts promote leucocyte migration across endothelial cell monolayers in tissue culture via an MCP-1-dependent mechanism. These findings may be relevant to the perivascular mononuclear leucocyte infiltrates characteristic of early SSc lesions.

Epidermal regulation of dermal fibroblast activity

Although the association between delayed burn wound healing and subsequent hypertrophic scar formation is well-established, the mechanism for this relationship is unknown. Unhealed burn wounds lack an epidermis, suggesting a possible regulatory role for the epidermis in controlling dermal fibroblast matrix synthesis. Therefore, we examined the effect of epidermal cells and media conditioned by epidermal cells on fibroblast collagen synthesis and replication. Purified fibroblast and keratinocyte cell strains were developed from discarded normal adult human skin. Conditioned media were created by incubation of cytokine-free and serum-free medium with either confluent fibroblast or keratinocyte cultures for 18 hours (n = 3). Nearly confluent fibroblast cultures were exposed for 48 hours to graded concentrations of either unconditioned medium (control), conditioned medium, or varying numbers of keratinocytes. Replication was quantified by the incorporation of 3H-thymidine. Collagen synthesis was measured by the incorporation of 3H-proline into collagenase-sensitive protein. Data were compared using analysis of variance (ANOVA) and linear regression. Keratinocyte conditioned medium induced a significant increase in replication (n = 3) (p = 0.004) and a decrease in collagen synthesis (n = 6) (p < 0.001). In contrast, neither fibroblast conditioned medium nor control medium had an effect on fibroblast replication or collagen synthesis. Co-culture of fibroblast with a graded number of keratinocytes similarly decreased collagen synthesis (n = 6) (p < 0.001). Dermal fibroblast collagen synthesis appears to be regulated by a soluble keratinocyte product. This result suggests a mechanism for the clinical observation that unhealed burn wounds, which lack the epidermis, demonstrate excess collagen production and scar. Clinical strategies to decrease hypertrophic scar should include an attempt at early wound closure with skin grafting or the application of cultured epithelial autografts.