The Viennese culture method: cultured human epithelium obtained on a dermal matrix based on fibroblast containing fibrin glue gels

Skin regeneration, repair, and reconstruction: present and future

Background

Large skin defects caused by trauma (e.g., burns) or due to other reasons (e.g., tumor-related skin resections) require sufficient skin replacement. The constant improvement of innovative methods of skin replacement and skin expansion mean that even burn victims with more than 80% body surface burned have a realistic chance of survival. Due to these new developments, not only has survival rate increased, but also quality of life has increased tremendously over the past decades.

Methods

The aim of this review is to present an overview of current standards and future trends concerning the treatment of skin defects. The main focus is placed on the most important technologies and future trends.

Results

Autologous skin grafting was developed more than 3500 years ago. Several approaches and techniques have been discovered and established in burn care and plastic surgery since then. Great achievements were made during the 19th and 20th centuries. Many of these old and new techniques are still part of modern burn and plastic surgery. Today, autologous skin grafting is still considered to be the gold standard for many wounds, but new technologies have been developed, ranging from biological to synthetic skin replacement materials.

Conclusion

Today, old and new technologies are available which allow us new treatment concepts. All this has led to the reconstructive clockwork for reconstructive surgery of the 21st century.

Advances in keratinocyte delivery in burn wound care

This review gives an updated overview on keratinocyte transplantation in burn wounds concentrating on application methods and future therapeutic cell delivery options with a special interest in hydrogels and spray devices for cell delivery. To achieve faster re-epithelialisation of burn wounds, the original autologous keratinocyte culture and transplantation technique was introduced over 3 decades ago. Application types of keratinocytes transplantation have improved from cell sheets to single-cell solutions delivered with a spray system. However, further enhancement of cell culture, cell viability and function in vivo, cell carrier and cell delivery systems remain themes of interest. Hydrogels such as chitosan, alginate, fibrin and collagen are frequently used in burn wound care and have advantageous characteristics as cell carriers. Future approaches of keratinocyte transplantation involve spray devices, but optimisation of application technique and carrier type is necessary.

[Skin engineering for severe burns]

Severe burned patients need definitive and efficient wound coverage. Outcome of massive burns has been improved by using cultured epithelial autografts (CEA). Despite fragility, percentages of success take, cost of treatment and long-term tendency to contracture, this surgical technique has been developed in few burn centres. First improvements were to combine CEA and dermis-like substitute. Cultured skin substitutes provide earlier skin closure and satisfying functional result. These methods have been used successfully in massive burns. Second improvement was to allow skin regeneration by using epidermal stem cells. Stem cells have capacity to differentiate into keratinocytes, to promote wound repair and to regenerate skin appendages. Human mesenchymal stem cells contribute to wound healing and were evaluated in cutaneous radiation syndrome. Skin regeneration and tissue engineering methods remain a complex challenge and offer the possibility of new treatment for injured and burned patients.

Development and Characterization of an Engraftable Tissue-Cultured Skin Autograft: Alternative Treatment for Severe Electrical Injuries

BACKGROUND/AIMS

Optimizing the treatment regimens of extensive or nonhealing defects is a constant challenge. Tissue-cultured skin autografts may be an alternative to mesh grafts and keratinocyte suspensions that are applied during surgical defect coverage.

METHODS

Autologous epidermal and dermal cells were isolated, in vitro expanded and seeded on collagen-elastin scaffolds. The developed autograft was immunohistochemically and electron microscopically characterized. Subsequently, it was transplanted onto lesions of a severely burned patient.

RESULTS

Comparability of the skin equivalent to healthy human skin could be shown due to the epidermal strata, differentiation, proliferation markers and development of characteristics of a functional basal lamina. Approximately 2 weeks after skin equivalent transplantation the emerging new skin correlated closely to the adjacent normal skin.

CONCLUSION

The present study demonstrates the comparability of the developed organotypic skin equivalent to healthy human skin and its versatility for clinical applications.

Validation of normal human bronchial epithelial cells as a model for influenza A infections in human distal trachea

Primary normal human bronchial/tracheal epithelial (NHBE) cells, derived from the distal-most aspect of the trachea at the bifurcation, have been used for a number of studies in respiratory disease research. Differences between the source tissue and the differentiated primary cells may impact infection studies based on this model. Therefore, we examined how well-differentiated NHBE cells compared with their source tissue, the human distal trachea, as well as the ramifications of these differences on influenza A viral pathogenesis research using this model. We employed a histological analysis including morphological measurements, electron microscopy, multi-label immunofluorescence confocal microscopy, lectin histochemistry, and microarray expression analysis to compare differentiated NHBEs to human distal tracheal epithelium. Pseudostratified epithelial height, cell type variety and distribution varied significantly. Electron microscopy confirmed differences in cellular attachment and paracellular junctions. Influenza receptor lectin histochemistry revealed that α2,3 sialic acids were rarely present on the apical aspect of the differentiated NHBE cells, but were present in low numbers in the distal trachea. We bound fluorochrome bioconjugated virus to respiratory tissue and NHBE cells and infected NHBE cells with human influenza A viruses. Both indicated that the pattern of infection progression in these cells correlated with autopsy studies of fatal cases from the 2009 pandemic.

Treatment of Hypertrophic Scar in Human with Autologous Transplantation of Cultured Keratinocytes and Fibroblasts along with Fibrin Glue

Objective

Hypertrophic scar involves excessive amounts of collagen in dermal layer and may be painful. Nowadays, we can’t be sure about effectiveness of procedure for hypertrophic scar management. The application of stem cells with natural scaffold has been the best option for treatment of burn wounds and skin defect, in recent decades. Fibrin glue (FG) was among the first of the natural biomaterials applied to enhance skin deformity in burn patients. This study aimed to identify an efficient, minimally invasive and economical transplantation procedure using novel FG from human cord blood for treatment of hypertrophic scar and regulation collagen synthesis.

Materials and Methods

In this case series study, eight patients were selected with hypertrophic scar due to full-thickness burns. Human keratinocytes and fibroblasts derived from adult skin donors were isolated and cultured. They were tested for the expression of cytokeratin 14 and vimentin using immunocytochemistry. FG was prepared from pooled cord blood. Hypertrophic scars were extensively excised then grafted by simply placing the sheet of FG containing autologous fibroblast and keratinocytes. Histological analyses were performed using Hematoxylin and eosin (H&E) and Masson’s Trichrome (MT) staining of the biopsies after 8 weeks.

Results

Cultured keratinocytes showed a high level of cytokeratin 14 expression and also fibroblasts showed a high level of vimentin. Histological analyses of skin biopsies after 8 weeks of transplantation revealed re-epithelialization with reduction of hypertrophic scars in 2 patients.

Conclusion

These results suggest may be the use of FG from cord blood, which is not more efficient than previous biological transporters and increasing hypertrophic scar relapse, but could lead to decrease pain rate.

Characterization of biomaterial-free cell sheets cultured from human oral mucosal epithelial cells

The purpose of this study was to report the characteristics of biomaterial-free sheets cultured from human oral mucosal epithelial cells without fibrin support, in vitro and after transplantation to limbal-deficient models. Human oral mucosal epithelial cells and limbal epithelial cells were cultured for 2 weeks, and the colony-forming efficiency (CFE) rates were compared. Markers of stem cells (p63), cell proliferation (Ki-67) and epithelial differentiation (cytokeratin; K1, K3, K4, K13) were observed in colonies and in biomaterial-free sheets. Biomaterial-free sheets which had been detached with 1% dispase or biomaterial-free sheets generated by fibrin support were transplanted to 12 limbal-deficient rabbit models. In vitro cell viability, in vivo stability and cytokeratin characteristics of biomaterial-free sheets were compared with those of sheets formed by fibrin-coated culture 1 week after transplantation. Mean CFE rate was significantly higher in human oral mucosal epithelial cells (44.8%) than in human limbal epithelial cells(17.7%). K3 and K4 were well expressed in both colonies and sheets. Biomaterial-free sheets had two to six layers of stratified cells and showed an average of 79.8% viable cells in the sheets after detachment. Cytokeratin expressions of biomaterial-free sheets were comparable to those of sheets cultured by fibrin support, in limbal-deficient models. Both p63 and Ki-67 were well expressed in colonies, isolated sheets and sheets transplanted to limbal-deficient models. Our results suggest that biomaterial-free sheets cultured from human oral mucosal epithelial cells without fibrin support can be an alternative option for cell therapy in use for the treatment of limbal-deficient diseases. Copyright © 2014 John Wiley & Sons, Ltd.

In vitro construction of scaffold-free bilayered tissue-engineered skin containing capillary networks

Many types of skin substitutes have been constructed using exogenous materials. Angiogenesis is an important factor for tissue-engineered skin constructs. In this study, we constructed a scaffold-free bilayered tissue-engineered skin containing a capillary network. First, we cocultured dermal fibroblasts with dermal microvascular endothelial cells at a ratio of 2 : 1. A fibrous sheet was formed by the interactions between the fibroblasts and the endothelial cells, and capillary-like structures were observed after 20 days of coculture. Epithelial cells were then seeded on the fibrous sheet to assemble the bilayered tissue. HE staining showed that tissue-engineered skin exhibited a stratified epidermis after 7 days. Immunostaining showed that the epithelium promoted the formation of capillary-like structures. Transmission electron microscopy (TEM) analysis showed that the capillary-like structures were typical microblood vessels. ELISA demonstrated that vascularization was promoted by significant upregulation of vascularization associated growth factors due to interactions among the 3 types of cells in the bilayer, as compared to cocultures of fibroblast and endothelial cells and monocultures.

Fibrin concentration affects ACL fibroblast proliferation and collagen synthesis

Fibrin is a frequently used biomaterial in surgery and tissue engineering. While it has been shown that fibrin supports cellular proliferation and biosynthesis, there is a scarcity of studies focusing on the effects of fibrin concentration. The objective of this study is to assess the effect of fibrin concentrations around the physiological concentration of 3mg/ml on the behavior of ligament fibroblasts. Fibroblasts were obtained from the anterior cruciate ligaments of four pigs and seeded throughout fibrin gels of either 1, 3, or 6 mg/ml fibrin. The gels were collected at 2, 6, and 10 days for measurement of DNA and collagen content. We found that both DNA and collagen content increased significantly over time in gels made with all concentrations of fibrin. However, the increases were significantly lower in gels made with the higher concentrations of fibrin (3 and 6 mg/ml). Microscopic assessment of FITC-labeled gels showed a decrease in pore size at high fibrin concentrations, which might be a reason for the observed effect on bioactivity. To enhance cell behavior and thus clinical results fibrin applications should build on physiologic or sub-physiologic concentrations, and those with higher concentrations, such as currently available sealants, should be used cautiously.

Composite tissue engineering on polycaprolactone nanofiber scaffolds

Tissue engineering has largely focused on single tissue-type reconstruction (such as bone); however, the basic unit of healing in any clinically relevant scenario is a compound tissue type (such as bone, periosteum, and skin). Nanofibers are submicron fibrils that mimic the extracellular matrix, promoting cellular adhesion, proliferation, and migration. Stem cell manipulation on nanofiber scaffolds holds significant promise for future tissue engineering. This work represents our initial efforts to create the building blocks for composite tissue reflecting the basic unit of healing. Polycaprolactone (PCL) nanofibers were electrospun using standard techniques. Human foreskin fibroblasts, murine keratinocytes, and periosteal cells (4-mm punch biopsy) harvested from children undergoing palate repair were grown in appropriate media on PCL nanofibers. Human fat-derived mesenchymal stem cells were osteoinduced on PCL nanofibers. Cell growth was assessed with fluorescent viability staining; cocultured cells were differentiated using antibodies to fibroblast- and keratinocyte-specific surface markers. Osteoinduction was assessed with Alizarin red S. PCL nanofiber scaffolds supported robust growth of fibroblasts, keratinocytes, and periosteal cells. Cocultured periosteal cells (with fibroblasts) and keratinocytes showed improved longevity of the keratinocytes, though growth of these cell types was randomly distributed throughout the scaffold. Robust osteoinduction was noted on PCL nanofibers. Composite tissue engineering using PCL nanofiber scaffolds is possible, though the major obstacles to the trilaminar construct are maintaining an appropriate interface between the tissue types and neovascularization of the composite structure.

Adult burn patients with more than 60% TBSA involved-Meek and other techniques to overcome restricted skin harvest availability--the Viennese Concept

Despite the fact that early excision and grafting has significantly improved outcome over the last decades, the management of severely burned adult patients with >/=60% total body surface area (% TBSA) burned still represents a challenging task for burn care specialists all over the world. In this article, we present our current treatment concept for this entity of severely burned patients and analyze its effect in a comparative cohort study. Surgical strategy comprised the use of split-thickness skin grafts (Meek, mesh) for permanent coverage, fluidized microsphere bead-beds for wound conditioning, temporary coverage (polyurethane sheets, Epigard; nanocrystalline silver dressings, Acticoat; synthetic copolymer sheets based on lactic acid, Suprathel; acellular bovine derived collagen matrices, Matriderm; allogeneic cultured keratinocyte sheets; and allogeneic split-thickness skin grafts), and negative-pressure wound therapy (vacuum-assisted closure). The autologous split-thickness skin graft expansion using the Meek technique for full-thickness burns and the delayed approach for treating dorsal burn wounds is discussed in detail. To demonstrate differences before and after the introduction of the Meek technique, we have compared patients of 2007 with >/=60% TBSA (n = 10) to those in a matched observation period (n = 7). In the first part of the comparative analysis, all patients of the two samples were analyzed with regard to age, abbreviated burn severity index, Baux, different entities of % TBSA, and survival. In the second step, only the survivors of both years were separated in two groups as follows: patients receiving skin grafts, using the Meek technique (n = 6), were compared with those without Meek grafting (n = 4). When comparing the severely burned patients of 2007 with a cohort of 2006, there were no differences for age (2007: 46.4 +/- 13.4 vs. 2006: 39.1 +/- 14.8 years), abbreviated burn severity index score (2007: 12.2 +/- 1.0 vs. 2006: 12.1 +/- 1.2) or % TBSA (2007: 72.1 +/- 11.7 vs. 2006: 69.3 +/- 8.7% TBSA). In these two rather small groups of severely burned patients with >/=60% TBSA, the overall survival rate of patients was 70.0% (7/10) in 2007 and 42.9% (3/7) in 2006, respectively. Almost all nonsurvivors in both years died within the first 5 days after admission. If assessing the different treatment modalities of the survivors, we found that although the Meek group patients were older (Meek 48.8 +/- 13.3 vs. non-Meek 26.8 +/- 11.5 years, P = .0381) and had consequently higher Baux scores (Meek 124.0 +/- 2.9 vs. non-Meek 93.8 +/- 8.5, P = .0095) than the non-Meek patients, this seemed to have no effect on length-of-stay (80.5 +/- 9.7 vs. non-Meek 79.8 +/- 33.0 days), hospital length-of-stay (85.7 +/- 14.8 vs. non-meek 84.3 +/- 26.1 days) or number of operations (6.5 +/- 1.0 vs. non-Meek 7.0 +/- 4.1 operations). The achieved results represent a combination of various treatment changes and, therefore, cannot be attributed to a single modality. The Meek technique is one of the technical options to choose from, to achieve permanent skin replacement; we think that it has its place if integrated in a whole treatment concept for management of severely burned patients.

Culture of subconfluent human fibroblasts and keratinocytes using biodegradable transfer membranes

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

Stem cells in cutaneous wound healing

Treatment of chronic wounds remains difficult, in spite of better understanding of pathophysiologic principles and greater adherence to recognized standards of care. Even with recent advances stemming from breakthroughs in recombinant growth factors and bioengineered skin, up to almost 50% of chronic wounds that have been present for more than a year remain resistant to treatment. Because of these realities, there is excitement in the use of stem cells to offset impaired healing. Early data appear encouraging, but much work remains to be done. Although pilot studies suggest that multipotent adult stem cells can accelerate wound repair or even reconstitute the wound bed, the answers will need to come from randomized clinical trials. Thus far, considerable focus has been placed on bone marrow-derived mesenchymal stem cells, and there are now promising approaches for introducing them into the wound. It might turn out, however, that other types of stem cells will be more effective, including those derived from hair follicles or, perhaps, subsets of bone marrow-derived cultured cells. Still, proper wound care and adherence to basic principles cannot be bypassed, even by the most sophisticated approaches.

Cultured epithelial autograft (CEA) in burn treatment: three decades later

Methods for handling burn wounds have changed in recent decades and increasingly aggressive surgical approach with early tangential excision and wound closure is being applied. Split-thickness skin (STSG) autografts are the "gold standard" for burn wound closure and remain the mainstay of treatment to provide permanent wound coverage and achieve healing. In some massively burned patients, however, the burns are so extensive that donor site availability is limited. Fortunately, considerable progress has been made in the culture of human keratinocytes and it is now possible to obtain large amounts of cultured epithelium from a small skin biopsy within 3-4 weeks. Questions related to optimal cell type for culture, culture techniques, transplantation of confluent sheets or non-confluent cells, immediate and late final take, carrier and transfer modality, as well as final outcome, ability to generate an epithelium after transplantation, and scar quality are still not fully answered. Progress accomplished since Reinwald and Green first described their keratinocyte culture technique is reviewed.

Reconstruction of living bilayer human skin equivalent utilizing human fibrin as a scaffold

Our aim of this study was to develop a new methodology for constructing a bilayer human skin equivalent to create a more clinical compliance skin graft composite for the treatment of various skin defects. We utilized human plasma derived fibrin as the scaffold for the development of a living bilayer human skin equivalent: fibrin-fibroblast and fibrin-keratinocyte (B-FF/FK SE). Skin cells from six consented patients were culture-expanded to passage 1. For B-FF/FK SE formation, human fibroblasts were embedded in human fibrin matrix and subsequently another layer of human keratinocytes in human fibrin matrix was stacked on top. The B-FF/FK SE was then transplanted to athymic mice model for 4 weeks to evaluate its regeneration and clinical performance. The in vivo B-FF/FK SE has similar properties as native human skin by histological analysis and expression of basal Keratin 14 gene in the epidermal layer and Collagen type I gene in the dermal layer. Electron microscopy analysis of in vivo B-FF/FK SE showed well-formed and continuous epidermal-dermal junction. We have successfully developed a technique to engineer living bilayer human skin equivalent using human fibrin matrix. The utilization of culture-expanded human skin cells and fibrin matrix from human blood will allow a fully autologous human skin equivalent construction.

Application for regenerative medicine of epithelial cell culture-vistas of cultured epithelium

This review describes culture techniques for the epithelial system as well as trends in the clinical application of cultured keratinocytes in our department and the possibility of applying the techniques to other organs. Cultured epithelium and cultured dermis in particular have considerably preceded regeneration of other organs in the field of regenerative medicine. Since 1988 we have grafted cultured keratinocytes by the Rheinwald-Green modified method in at least 500 patients with large skin defects. As a result of the establishment of a culture technique for individual patients, it is now possible to prepare enough regenerated epithelium to cover the body surface area of as many as 10 adult patients in approximately three weeks after collecting 1 cm(2) of skin, and then remaining cultured keratinocytes can be cryo-preserved for two-stage dermatoplasty at another site. This procedure makes it possible to avoid frequent skin collection from the same patient and thereby improves patients' quality of life and activities of daily living. On the other hand, to solve the problem of regenerated epithelium shrinking and problems with graft efficiency on dermis defect lesion, we have developed a proteinase-resistant regenerated dermis by mixing a certain protein with a fibrin scaffold. Recently we also took the initiative in grafting hybrid-type regenerated trachea in an animal experiment by using the epithelial and dermal cell culture technique, and some results of the graft were obtained.

Cultured human epithelium: human umbilical cord blood stem cells differentiate into keratinocytes under in vitro conditions

BACKGROUND

Stem cells have the capacity to renew or to give rise to a specialized cell types. Human umbilical cord blood (HUCB) has been explored as an alternative source of stem cells. However, its potential to differentiate into cells of other tissues is still under discussion. The aim of our study was to evaluate if HUCB stem cells could differentiate into epithelial cells under in vitro conditions.

METHODS

Human keratinocytes derived from adult female skin donors, were isolated and cultured on fibrin glue/fibroblast gels-control group. In the umbilical cord blood cell group, male umbilical cord blood cells were added at a 1:10 ratio to keratinocytes and co-cultured on the fibrin glue/fibroblasts gel. After 15 days of culture, the sheets were analyzed by use of histochemistry and FISH. DNA was extracted and evaluated by use of polymerase chain reaction (PCR) for detection of Y-chromosome-specific sequences.

RESULTS

In both groups a regular epithelial sheet consisting of three to four layers of cells was formed. Using PCR and FISH, in the umbilical cord blood cell group the presence of Y-chromosome-specific sequences in the cultured keratinocytes could be detected. In the control group, no Y-chromosome-specific sequences could be detected.

CONCLUSION

Our findings indicate that umbilical cord blood stem cells differentiate into epithelial cells under in vitro conditions and thereby, might serve as a starting material for isolation and expansion of cells for transplantation in patients with large skin defects.