A guide to biological skin substitutes

[The role of Integra dermal regeneration matrix in skin replacement on the upper extremity]

Authors report the application of Integra dermal regeneration matrix in 10 patients in 12 indications (ages 25-74 years, 6 female and 4 male patients). The smallest reconstructed area was 6 cm2, the largest was 500 cm2. Skin coverage was needed on the lower arm in two patients, on the lower arm and the hand in two patients and on the hand in six patients. Skin grafting onto the neodermis was made on days 19-25. The take rate of Integra was equal or higher than 97%, and the take rate of the skin graft was equal or higher than 90%. Integra dermal regeneration template proved to be suitable for the management of complex wounds on the hands and upper extremities.

Shelf-life evaluation of bilayered human skin equivalent, MyDerm™

Skin plays an important role in defense against infection and other harmful biological agents. Due to its fragile structure, skin can be easily damaged by heat, chemicals, traumatic injuries and diseases. An autologous bilayered human skin equivalent, MyDerm™, was engineered to provide a living skin substitute to treat critical skin loss. However, one of the disadvantages of living skin substitute is its short shelf-life, hence limiting its distribution worldwide. The aim of this study was to evaluate the shelf-life of MyDerm™ through assessment of cell morphology, cell viability, population doubling time and functional gene expression levels before transplantation. Skin samples were digested with 0.6% Collagenase Type I followed by epithelial cells dissociation with TrypLE Select. Dermal fibroblasts and keratinocytes were culture-expanded to obtain sufficient cells for MyDerm™ construction. MyDerm™ was constructed with plasma-fibrin as temporary biomaterial and evaluated at 0, 24, 48 and 72 hours after storage at 4°C for its shelf-life determination. The morphology of skin cells derived from MyDerm™ remained unchanged across storage times. Cells harvested from MyDerm™ after storage appeared in good viability (90.5%±2.7% to 94.9%±1.6%) and had short population doubling time (58.4±8.7 to 76.9±19 hours). The modest drop in cell viability and increased in population doubling time at longer storage duration did not demonstrate a significant difference. Gene expression for CK10, CK14 and COL III were also comparable between different storage times. In conclusion, MyDerm™ can be stored in basal medium at 4°C for at least 72 hours before transplantation without compromising its functionality.

Human keratinocyte growth and differentiation on acellular porcine dermal matrix in relation to wound healing potential

A number of implantable biomaterials derived from animal tissues are now used in modern surgery. Xe-Derma is a dry, sterile, acellular porcine dermis. It has a remarkable healing effect on burns and other wounds. Our hypothesis was that the natural biological structure of Xe-Derma plays an important role in keratinocyte proliferation and formation of epidermal architecture in vitro as well as in vivo. The bioactivity of Xe-Derma was studied by a cell culture assay. We analyzed growth and differentiation of human keratinocytes cultured in vitro on Xe-Derma, and we compared the results with formation of neoepidermis in the deep dermal wounds treated with Xe-Derma. Keratinocytes cultured on Xe-Derma submerged in the culture medium achieved confluence in 7-10 days. After lifting the cultures to the air-liquid interface, the keratinocytes were stratified and differentiated within one week, forming an epidermis with basal, spinous, granular, and stratum corneum layers. Immunohistochemical detection of high-molecular weight cytokeratins (HMW CKs), CD29, p63, and involucrin confirmed the similarity of organization and differentiation of the cultured epidermal cells to the normal epidermis. The results suggest that the firm natural structure of Xe-Derma stimulates proliferation and differentiation of human primary keratinocytes and by this way improves wound healing.

On the tissue compatibility of poly(ether imide) membranes: an in vitro study on their interaction with human dermal fibroblasts and keratinocytes

Recently we have developed a novel type of membrane based on poly(ether imide) (PEI) which is considered for biomedical application. To improve its physical and biological performance it was modified by blending with poly(benzimidazole) (PBI). In the present study both membranes were characterized in terms of their physicochemical properties and in vitro tissue compatibility using human dermal fibroblasts and keratinocytes. The modified membrane (PEI*) was more hydrophilic, less porous and had an increased surface (zeta) potential. We further found that blending with PBI tends to promote cell contact, at least initially, as indicated by the improved overall cell morphology, adhesion and spreading of fibroblasts, and the development of focal adhesion complexes. The effects of fibronectin (FN) and serum coating were also beneficial when compared to pure PEI and tissue culture polystyrene (TCP), which correlates to a higher adsorption of both FN and vitronectin detected by ELISA. However, a clear tendency for homotypic cellular interaction particularly of keratinocytes was obtained in contact with membranes, which was much stronger pronounced on PEI*. Although the initial adhesion was greater on PEI*, a surprising decrease in cell growth was observed at later stages of incubation, which may be explained with the membrane-promoted cellular aggregation leading to an easier detachment from the substratum. Thus, membranes based on blends of PEI with PBI could provide a tissue compatible scaffold with lowered adhesive properties, which might be a useful tool for the transfer of cells, for example, to in vitro engineered tissue constructs.

Tissue engineering of lips and muco-cutaneous junctions: in vitro development of tissue engineered constructs of oral mucosa and skin for lip reconstruction

We report for the first time the fabrication of a three-dimensional tissue structure containing, in a continuous layer, the morphological features of a lip: epidermal skin, vermillion, and oral mucosa. This tissue engineered muco-cutaneous (M/C) equivalent was manufactured using human oral and skin keratinocytes grown on an acellular, nonimmunogenic dermal equivalent (AlloDerm(®)) to produce a tissue equivalent with similar anatomic and handling properties as native human lips. Confirmation of the structural composition of the construct was performed using routine histology and immunohistochemistry by identification of epithelial markers that are differentially expressed in separate anatomic areas of the lips. These full-thickness human lip skin equivalents can be used in surgical lip reconstruction in individuals suffering from lip loss from cancer, congenital deformations, and injuries after accidents. We propose this technique can be used as a general basis for tissue engineering of M/C junctions in other parts of the body, such as anus and vagina.

Evaluation of two commonly used temporary skin dressings for the treatment of acute partial-thickness wounds in rats

OBJECTIVES

There is a broad range of expensive temporary wound dressings that promise better results in wound management. The aim of this study was to compare two commonly used temporary dressings for the treatment of partial-thickness wounds in a rat model.

METHODS

Forty-two partial thickness wounds were created on the back of Lewis rats and treated with the dressings; control wounds remained without treatment. Wound size was determined daily by measuring the scabbed area. Three months after the wounds were created, skin elasticity was measured and a histologic evaluation was performed.

RESULTS

Wound appearance in the animals in the treated groups did not differ significantly. Wound closure was slower in the control group than in the dressing groups. There was no histologic evidence of inflammation and no suggestion of epidermal changes in any group.

CONCLUSION

Using both skin dressings, we observed satisfying results without any significant differences. Because of rising health care expenses, cost should play an essential role in the clinical application of these dressings.

Advances in wound healing: a review of current wound healing products

Successful wound care involves optimizing patient local and systemic conditions in conjunction with an ideal wound healing environment. Many different products have been developed to influence this wound environment to provide a pathogen-free, protected, and moist area for healing to occur. Newer products are currently being used to replace or augment various substrates in the wound healing cascade. This review of the current state of the art in wound-healing products looks at the latest applications of silver in microbial prophylaxis and treatment, including issues involving resistance and side effects, the latest uses of negative pressure wound devices, advanced dressings and skin substitutes, biologic wound products including growth factor applications, and hyperbaric oxygen as an adjunct in wound healing. With the abundance of available products, the goal is to find the most appropriate modality or combination of modalities to optimize healing.

Stem Cell Therapy: A New Treatment for Burns?

Stem cell therapy has emerged as a promising new approach in almost every medicine specialty. This vast, heterogeneous family of cells are now both naturally (embryonic and adult stem cells) or artificially obtained (induced pluripotent stem cells or iPSCs) and their fates have become increasingly controllable, thanks to ongoing research in this passionate new field. We are at the beginning of a new era in medicine, with multiple applications for stem cell therapy, not only as a monotherapy, but also as an adjunct to other strategies, such as organ transplantation or standard drug treatment. Regrettably, serious preclinical concerns remain and differentiation, cell fusion, senescence and signalling crosstalk with growth factors and biomaterials are still challenges for this promising multidisciplinary therapeutic modality. Severe burns have several indications for stem cell therapy, including enhancement of wound healing, replacement of damaged skin and perfect skin regeneration - incorporating skin appendages and reduced fibrosis -, as well as systemic effects, such as inflammation, hypermetabolism and immunosuppression. The aim of this review is to describe well established characteristics of stem cells and to delineate new advances in the stem cell field, in the context of burn injury and wound healing.

[Use of Integra in a case of extensive upper extremity avulsion]

Authors performed successful skin replacement with Integra, a dermal regeneration template, on a patient with circumferential avulsion injury including the elbow region and the dorsum of the hand. The take rate of Integra was 97%, followed by a 98% take rate of the split thickness mesh graft used for final wound coverage. Treatment modality provided excellent aesthetic and functional results, underlining the role of Integra in cases of extensive traumatic skin and soft tissue deficit, such as the treatment of avulsion injury.

Evaluation of the Biocompatibility of a Bilayer Chitosan Skin Regenerating Template, Human Skin Allograft, and Integra Implants in Rats

Introduction. Chitosan is a nontoxic, biocompatible, and biodegradable polymer obtained from chitin by N-deacetylation using strong alkali. Chitosan in a form of a bilayer skin regenerating template can act as a scaffold for regeneration. Integra is a two-layer skin regeneration system, constructed of a matrix of crosslinked fibers that acts as a scaffold for regenerating dermal skin cells. Human skin allografts (HSAs) are the “gold standard” for temporary coverage of clean burn wounds. Objectives. The objective of this study was to conduct in-vivo, preclinical biocompatibility evaluations of Integra, HSA, and Chitosan skin regenerating template (SRT). Methods. Paravertebral subcutaneous pockets were created for the implantation of test materials. Implants were retrieved after 4, 7, 14, 21, and 28 days. Slides of sections through the implants were examined to determine biocompatibility. Results. Chitosan SRT and Integra showed similar inflammatory patterns. HSA showed a higher inflammatory reaction initially which then reduced to levels similar to Integra and Chitosan SRT. Chitosan SRT and Integra also shared similar angiogenesis levels. Towards the end, all implants were degraded with decreased tissue response. Conclusion. Integra, Chitosan SRT, and HSA have been shown to be biocompatible. Integra and Chitosan SRT seem to illicit similar tissue responses.

A clinical evaluation of Biobrane(®) and Suprathel(®) in acute burns and reconstructive surgery

BACKGROUND

In the treatment of superficial partial-thickness burns, various skin substitutes and temporary dressings offer potential advantages over traditional treatments. Nonetheless, the search for an ideal temporary skin substitute or biosynthetic wound dressing is still a continuous quest. This research aimed to provide objective data on the long-term outcome of Biobrane(®) and Suprathel(®).

METHODS

Eight months after the initial burn treatment of Biobrane(®) and Suprathel(®), skin elasticity was measured objectively using a Cutometer(®) and the scarring process was quantified using the Vancouver Scar Scale (VSS).

RESULTS

The median healing time for patients treated with Biobrane(®) was up to 1.8 days shorter then the Suprathel(®) group. Regarding the Vancouver Scar Scale (VSS), neither the single parameter, nor the total score were significantly different in both groups. In comparison, the Biobrane(®) group demonstrated superior Cutometer(®) parameters in regards to maximal extension, elasticity, retraction and pliability. Despite higher levels of Biobrane(®) group, the differences in the viscoelastic analysis of both substitutes did not vary significantly.

CONCLUSION

Using both substitutes, we observed satisfying results in superficial partial-thickness burn treatment, without any significant differences. Since the treatment of burned patients is associated with high socioeconomic load, the cost factor should be one of the most important criteria in dermal substitute selection.

Biologicals and fetal cell therapy for wound and scar management

Few biopharmaceutical preparations developed from biologicals are available for tissue regeneration and scar management. When developing biological treatments with cellular therapy, selection of cell types and establishment of consistent cell banks are crucial steps in whole-cell bioprocessing. Various cell types have been used in treatment of wounds to reduce scar to date including autolog and allogenic skin cells, platelets, placenta, and amniotic extracts. Experience with fetal cells show that they may provide an interesting cell choice due to facility of outscaling and known properties for wound healing without scar. Differential gene profiling has helped to point to potential indicators of repair which include cell adhesion, extracellular matrix, cytokines, growth factors, and development. Safety has been evidenced in Phase I and II clinical fetal cell use for burn and wound treatments with different cell delivery systems. We present herein that fetal cells present technical and therapeutic advantages compared to other cell types for effective cell-based therapy for wound and scar management.

Use of an autologous bioengineered composite skin in extensive burns: Clinical and functional outcomes. A multicentric study

OBJECTIVE

We report clinical and functional outcomes obtained after application of an autologous bioengineered composite skin (ABCS) produced in a single Spanish tissue-engineering unit.

MATERIALS/METHODS

Twenty-five burned patients treated with ABCS from 1999 to 2007 in five burn centres were included in the study. Mean age was 29 years (SD 11), with mean total body surface area (TBSA) burned being 74% (SD 17) and mean full-thickness injury of 61% (SD 19) of TBSA.

RESULTS

The mean area initially engrafted with ABCS was 24% (SD 13) of TBSA, with a final take of 49% (SD 30, range 0-100%). ABCS achieved permanent coverage of a mean of 11% (SD 8) of TBSA. In subset analyses, lack of pre- and post-application wound bed infection and lack of serious acute systemic complications at the time of engraftment were significantly associated with better ABCS take.

CONCLUSIONS

Final take obtained with ABCS could be improved with the use of non-cytotoxic topical antibiotics following engraftment. The use of plasma to prepare ABCS reduces production costs: cost-effectiveness ratio is not a limitation for its use. In terms of patient satisfaction, cosmetic/functional outcomes (general appearance, texture, flexibility, sensitivity and colour) of ABCS and split-thickness autografts are not different statistically.

New biological temporary skin cover Xe-Derma(®) in the treatment of superficial scald burns in children

BACKGROUND

Xe-Derma® is a new dry sterile biological cover derived from acellular pig dermis. Hydrated Xe-Derma® displays bio-mechanical features similar to the normal skin. The aim of the present study was to compare the efficacy of Xe-Derma® with hydrocolloid dressing Askina THINSite® for treatment of superficial burns in children in a prospective study.

MATERIALS AND METHODS

In a prospective study, 86 patients (5 months to 7 years of age) with superficial scald burns on a surface area of 1-35% BSA were enrolled. In the course of the study, 43 patients were treated with Xe-Derma® and 43 patients with Askina THINSite®. We collected data including the percentage of BSA covered with biological or synthetic material, epithelization time, the number of complete conversions (deepening of 100% of covered area into deep dermal wound) under each cover, the number and extent of partial conversions (deepening of less then 100% of covered area into deep dermal wound), infectious complications, the number of reapplications of the temporary cover and the extent in square centimetres of dressing material needed for successful healing of 1% BSA.

RESULTS

No significant difference in the epithelization time, percentage of conversion from superficial to deep dermal burns and percentage of infectious complication was detected between the two groups. However, patients in the Xe-Derma® group were burned on a more extensive burn surface area (p ≤ 0.028). Xe-Derma® showed adherence to the wound and therefore there has been no need to be changed The number of reapplications and therefore also the number of square centimetres needed for successful healing of 1% BSA were statistically higher in the Askina THINSite® group (p < 0.01) due to increased secretion and accumulation of fluid underneath this hydrocoloid cover. The minimal frequency of changes of this biological cover material brings a significant benefit to pediatric patients.

CONCLUSION

Acellular pig dermis Xe-Derma® represents a reliable biological cover material. It is an advantageous alternative to synthetic temporary skin covers in the treatment of superficial scald burns in children.

Silica-collagen bionanocomposites as three-dimensional scaffolds for fibroblast immobilization

Silica-collagen bionanocomposite hydrogels were obtained by addition of silica nanoparticles to a protein suspension followed by neutralization. Electron microscopy studies indicated that larger silica nanoparticles (80 nm) do not interact strongly with collagen, whereas smaller ones (12 nm) form rosaries along the protein fibers. However, the composite network structurally evolved with time due to the contraction of the cells and the dissolution of the silica nanoparticles. When compared to classical collagen hydrogels, these bionanocomposite materials showed lower surface contraction in the short term (1 week) and higher viability of entrapped cells in the long term (3 weeks). A low level of gelatinase MMP2 enzyme expression was also found after this period. Several proteins involved in the catabolic and anabolic activity of the cells could also be observed by immunodetection techniques. All these data suggest that the bionanocomposite matrices constitute a suitable environment for fibroblast adhesion, proliferation and biological activity and therefore constitute an original three-dimensional environment for in vitro cell culture and in vivo applications, in particular as biological dressings.

Dried gamma-irradiated amniotic membrane as dressing in burn wound care

RATIONALE

Dried amniotic membrane contains collagen matrix and key bioactive molecules like fibronectin, laminin, glycosaminoglycans and elastin. Fresh and cryopreserved human amniotic membrane has been widely explored as a biological dressing. However, fresh and cryopreserved amniotic membranes are not readily available or require special storage conditions. This investigation was aimed to study the functional and clinical efficacy of air-dried radiation sterilized amniotic membranes as dressing in burn wound care.

METHODS

Amniotic membranes collected from placentae of screened donors were processed and sterilized by gamma radiation at 25 kGy. The fluid handling capacity, shelf life and clinical efficacy of air-dried gamma-irradiated amniotic membranes was evaluated.

RESULTS

Fluid handling capacity of the air-dried irradiated amniotic membrane dressing was 3.79-4.2 g/10 cm(2) in 24 h. Infrared (IR) spectral scanning showed no degradation or change in the dried gamma-irradiated amniotic tissue after 2 and 5 years of storage. No effect of storage on the impermeability of the processed amniotic membranes to bacteria was observed. The dried gamma-irradiated amniotic membranes even after 5 years of storage provided an effective barrier to microbial penetration. The dried amniotic membranes were applied to 22 cases of scald, flame and electrical burns. Of the 22 patients studied, 19 patients had excellent results in the form of complete epithelialization of wound with an average healing time of 15-25 days.

CONCLUSION

IR studies and microbial permeability test indicate no qualitative changes in the material property of dried gamma-irradiated amniotic membranes after 2 and 5 years of storage. Air-dried amniotic membrane with the advantage of storage at room temperature as well as functional efficiency is an ideal dressing for burn wound care.

Elastin-based materials

Elastin is a versatile elastic protein that dominates flexible tissues capable of recoil, and facilitates commensurate cell interactions in these tissues in all higher vertebrates. Elastin's persistence and insolubility hampered early efforts to construct versatile biomaterials. Subsequently the field has progressed substantially through the adapted use of solubilized elastin, elastin-based peptides and the increasing availability of recombinant forms of the natural soluble elastin precursor, tropoelastin. These interactions allow for the formation of a sophisticated range of biomaterial constructs and composites that benefit from elastin's physical properties of innate assembly and elasticity, and cell interactive properties as discussed in this tutorial review.

Bioengineered skin in diabetic foot ulcers

OBJECTIVE

Bioengineered skin (BS) has been shown to play an important role in the treatment of diabetic foot ulcers (DFUs). Whether BS in the therapy of DFU can improve the outcomes still remains uncertain. We performed a quantitative meta-analysis of available randomized controlled trials to determine the effectiveness and safety of BS in the treatment of patients with DFUs.

DESIGN AND METHODS

Comprehensive search strategies of various electronic databases were used for this study to evaluate the effectiveness and safety between BS and conventional treatment (CT) in patients with DFU, and only randomized controlled trials were adopted in our review. Search terms included 'bioengineered skin', 'tissue-engineering skin', 'human-tissue graft', 'human-skin device', 'living-skin equivalent' and 'diabetic foot', 'diabetic ulcer', 'diabetic wound'. Analysis outcomes included complete wound closure, complications, ulcer recurrence and adverse severe events (ASEs).

RESULTS

Seven randomized controlled trials on BS vs. CT were included, and 880 participants met inclusion criteria. Pooled analysis showed a significant effectiveness and safety advantages for BS treatment compared to CT for patients with DFUs. In analysis of complications, only statistically significant difference of infection was noted. And no included trials reported ASEs related to these treatments.

CONCLUSIONS

Based on the meta-analysis, patients with DFUs may benefit from the BS because of its high effectiveness and safety and reduced risk for infections in comparison to CT.

The use of human deceased donor skin allograft in burn care

Burns are tissue wounds caused by thermal, electrical, chemical cold or radiation injuries. Deep injuries lead to dermal damage that impairs the ability of the skin to heal and regenerate on its own. Skin autografting following burn excision is considered the current gold standard of care, but lack of patient's own donor skin or unsuitability of the wound for autografting may require the temporary use of dressings or skin substitutes to promote wound healing, reduce pain, and prevent infection and abnormal scarring. These alternatives include deceased donor skin allograft, xenograft, cultured epithelial cells and biosynthetic skin substitutes. Allotransplantation is the transplantation of cells, tissues, or organs, sourced from a genetically non-identical member of the same species as the recipient. Human deceased donor skin allografts represent a suitable and much used temporizing option for skin cover following burn injury. The main advantages for its use include dermoprotection and promotion of reepithelialisation of the wound and their ability to act as skin cover until autografting is possible or re-harvesting of donor sites becomes available. Disadvantages of its use include the limited abundance and availability of donors, possible transmission of disease, the eventual rejection by the host and its handling storing, transporting and associated costs of provision. This paper will explore the role of allograft skin in burn care, defining the indications for its use in burn management and the future potential for allograft tissue banking.

Long-term results after reconstruction of full thickness scalp defects with a dermal regeneration template

OBJECTIVE

Large scalp defects in which the pericranium has to be resected can be reliably reconstructed using Integra. In the present study, we retrospectively analysed the long-term outcome of our patients.

METHODS

Nineteen patients were included who had received Integra dermal regeneration template for treatment of full thickness scalp defects after resection of various malignant tumours. All patients were followed up with a mean follow-up time of 31 months (14-72).

RESULTS

All transplants were on almost equal levels with the surrounding skin. Cosmetic results were acceptable and scars were stable. Nodal ultrasound status was negative in all patients. During the follow-up period of up to 72 months, no local recurrences were observed. One patient with a leiomyosarcoma received radiotherapy after transplantation. In the irradiated area, multiple small regular-shaped round ulcerations and later on partial necrosis of the transplant occurred when the patient developed renal failure 29 months after the initial operation. Five patients died of disease not related to the primary skin tumour. All other patients are alive and free of disease without any complications.

CONCLUSION

After reconstruction of full thickness scalp defects with Integra, the cosmetic results are appealing and we observed no local recurrences during the follow-up period.

A review of tissue-engineered skin bioconstructs available for skin reconstruction

Situations where normal autografts cannot be used to replace damaged skin often lead to a greater risk of mortality, prolonged hospital stay and increased expenditure for the National Health Service. There is a substantial need for tissue-engineered skin bioconstructs and research is active in this field. Significant progress has been made over the years in the development and clinical use of bioengineered components of the various skin layers. Off-the-shelf availability of such constructs, or production of sufficient quantities of biological materials to aid rapid wound closure, are often the only means to help patients with major skin loss. The aim of this review is to describe those materials already commercially available for clinical use as well as to give a short insight to those under development. It seeks to provide skin scientists/tissue engineers with the information required to not only develop in vitro models of skin, but to move closer to achieving the ultimate goal of an off-the-shelf, complete full-thickness skin replacement.

The noninvasive, quantitative, in vivo assessment of adenoviral-mediated gene delivery in skin wound biomaterials

Because there are few reports using gene delivery in clinically-approved synthetic matrices, we examined the feasibility of using a noninvasive imaging system to study the kinetics of luciferase gene expression when delivered in an adenoviral vector. Using a mouse model of full thickness injury, we quantified the kinetics of gene expression, determined the optimal dose of particle delivery, and established the temporal importance of drug delivery in obtaining optimal gene expression. Specifically, we found that the ideal time to deliver adenovirus to a graft is during the early phase of graft wound closure (days 0-3 post-operatively) for a peak of gene expression to occur 7 days after delivery. Under these conditions, there is a saturating dose of 6 x 10(8) adenoviral particles per graft. In light of these findings, we examined whether the efficacy of delivery could be increased by modulating the composition of the grafts. When a collagen gene-activated matrix (GAM) containing basic fibroblast growth factor (FGF2) was compared to matrix alone, a significant increase in gene expression is observed when identical amounts of vector are delivered (p<0.05). Taken together, these results show how a noninvasive and quantitative assessment of gene expression can be used to optimize gene delivery and that the composition of matrices can dramatically influence gene expression in the wound bed.

Innovative strategies for tissue engineered skin based on multiple growth factors gene transfection

Tissue engineering combines the principles of cell biology, engineering and materials science to develop three-dimensional tissues to replace or restore tissue function. Tissue engineered skin (TE-skin) is one of most advanced tissue constructs. However, much clinical providence demonstrates the TE-skin may not be viewed as the equal of skin grafts, the contributions to accelerate the closure of wound were come mainly from various growth factor. These growth factors respond to its environment to bring about the desired effect. In our hypothesis, this three-dimensional skin substitute could be genetically modified with various growth factor and transplanted in order to deliver therapeutic proteins locally and systemically for the treatment of trauma. The likelihood of transgened TE-skin plays function as a pharmacological agent suggests a wide range of therapeutic applications. In future, the TE-skin could be design as gene delivery to enhance potential capacity for treatment of burns, chronic wounds and even systemic diseases.

Proliferation of fibroblasts cultured on a hemi-cellulose dressing

In recent times, hemi-cellulose dressing (HD) has been used clinically with satisfactory rates of success [Melandri D, De Angelis A, Orioli R, et-al. Use of a new hemicellulose dressing (Veloderm) for the treatment of split-thickness skin graft donor sites A within-patient controlled study. Burns 2006 Dec;32:964-72.]; however, the effect of cellulose dressings on the wound-healing process is unclear due to paucity of experimental data. This study aimed to determine the adhesion and proliferation of human skin fibroblasts, which were cultured in vitro using the explant technique, on HD. Cells were seeded onto HD discs and evaluated for cell adhesion and cell proliferation after 7, 14 and 21 days. Fibroblasts displayed 70% adhesion to HD after 24h. The HD discs seeded with a density of 5x10(4) cells per well showed a proliferation rate of 12% on day 7, 30% on day 14 and 75% on day 21. The results demonstrated that HD can sustain fibroblast proliferation--a highly desirable characteristic for an ideal skin substitute.