Treatment of skin ulcers with cultured epidermal allografts

Cultured skin loaded with tetracycline HCl and chloramphenicol as dermal delivery system: Mathematical evaluation of the cultured skin containing antibiotics

Dermal patches consisting of cultured human skin with antibiotics, which have a protective effect on wound skin as well as a preventative effect on second infection of the skin, were prepared and mathematically analyzed as a new drug delivery system (DDS) that can be applied to serious skin defects such as severe burns. In the present study, a three-dimensional cultured human skin model (living skin equivalent-high, LSE-high) was used as a cultured skin membrane and tetracycline HCl (TC-HCl) and chloramphenicol (CP) were used as antibiotics. At first, antibiotics were entrapped in the LSE-high from the dermal side through culture medium in order to obtain a drug-loaded LSE-high. The antibiotic release from the drug-loaded LSE-high was then examined and the resulting release data were used to calculate the effective diffusion coefficient of the antibiotics (D(LSE)) and initial loading concentration of the antibiotics (C0) in the LSE-high. The release profile of TC-HCl was represented by general diffusion-limited kinetics, whereas an initial burst effect was found in the release profile of CP. Therefore, the burst effect was taken into account for analyzing the release profile of CP. Stripped skin excised from hairless rats was used as a wound model, and the antibiotic permeation through the skin from aqueous solution was examined and evaluated using differential equations for Fick's second law of diffusion to obtain the effective diffusion coefficient of the antibiotics in the wound skin (D(skin)). Furthermore, the antibiotic permeation profile through the excised stripped skin from the drug-loaded LSE-high was measured and theoretically evaluated by Fick's second law of diffusion with previously obtained parameters (C0, D(LSE), D(skin)) using a newly constructed two- or three-layered diffusion model. The calculated concentrations of TC-HCl and CP in the upper epidermis of the model wound skin were over their minimum inhibitory concentration (MIC) for several hours against various bacteria, suggesting that this dosage system is useful for the treatment of severe burns. In addition, the present analytical method and diffusion model, with the drug-loaded LSE-high and stripped rat skin, are useful tools for evaluating this new DDS.

Skin grafting for venous leg ulcers

BACKGROUND

Venous leg ulceration is a common and disabling condition which often recurs. It affects up to one in 100 adults at some time. The usual treatments are simple dressings and compression bandages or stockings. Unfortunately, in some cases this treatment is unsuccessful, with ulcers remaining open for months or years. Sometimes skin grafts are used to stimulate healing. These skin grafts may be taken from the patient's own uninjured skin, may be grown from the patient's skin cells into a dressing (autografts), or applied as a sheet of bioengineered skin grown from donor cells (allograft). Preserved skin from other animals, such as pigs, has also been used; these grafts are known as xerografts.

OBJECTIVES

To assess the effect of skin grafts for treating venous leg ulcers.

SEARCH STRATEGY

We searched the Cochrane Wounds Group Specialised Register (June 2004) and the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2004).

SELECTION CRITERIA

Randomised controlled trials (RCTs) of skin grafts in the treatment of venous leg ulcers.

DATA COLLECTION AND ANALYSIS

Two reviewers independently undertook data extraction and assessment of study quality.

MAIN RESULTS

Nine trials of skin grafts for venous leg ulcers were identified, involving 579 participants. The trials were generally of poor methodological quality. In eight trials participants also received compression bandaging. Two trials (98 participants) evaluated split thickness autografts (one against a dressing and one against a xerograft), four trials (119 participants) evaluated cultured keratinocyte grafts (3 allografts and 1 autograft) , two compared tissue engineered skin (bilayer artificial skin) with a dressing (345 participants), and one compared it with a split thickness skin graft (7 participants, 13 ulcers). The trials comparing bilayer artificial skin with a dressing reported a significantly higher proportion of ulcers healing with artificial skin. There was not enough evidence from the other trials to determine whether other types of skin grafting increased the healing of venous ulcers.

AUTHORS' CONCLUSIONS

There is evidence that a bilayer artificial skin, used in conjunction with compression bandaging, increases the chance of healing a venous ulcer compared with compression and a simple dressing. Further research is needed to assess whether other forms of skin grafts increase ulcer healing.

Cryopreserved and lyophilized cultured epidermal allografts in the treatment of leg ulcers: a pilot study

BACKGROUND

In the conservative therapy of venous leg ulcers modern types of dressings are used most frequently. In the past 20 years 'active wound dressings' - cultured epidermal keratinocytes as autografts and allografts - were also introduced in the management of leg ulcers.

METHODS

The aim of our study was to compare the effect of cryopreserved and lyophilized cultured epidermal allografts in the treatment of venous leg ulcers. Evaluation of the therapy was documented as photodocumentation, planimetry, healing time and evaluation of pain relief over a 3-month period after application. Fifty patients with venous leg ulcers were selected. Twenty-five patients (group I) were treated with cryopreserved keratinocytes and 25 (group II) with lyophilized keratinocytes.

RESULTS

The final evaluation 3 months after the application of allografts showed 84% of healed ulcers in group I and 80% in group II. The number of healed ulcers and the healing rate both showed no statistically significant differences. The size of the ulcer was reduced by half during the first week in both groups. The size differences during the first week are statistically significant in both groups and they are comparable (P < 0.001). The intensity of the pain was statistically significantly reduced during the first week after application in both groups (P < 0.001).

CONCLUSIONS

The cryopreserved and lyophilized cultured allografts are comparable in healing rate, course of healing and relief of pain, and also in planimetric changes during the healing of venous leg ulcers. Lyophilized allografts are more convenient for routine use than cryopreserved allografts as they can be stored at room temperature. These results could give rise to the more frequent use of lyophilized allografts in slow-healing venous leg ulcers.

Abdominal aplasia cutis congenita: case report and review of the literature

A case of bilateral abdominal aplasia cutis congenita without skull defect is reported and was treated successfully by a combination of allografts and growth factors delivered by allogenic cultured keratinocytes.

Long-term remodeling of a bilayered living human skin equivalent (Apligraf) grafted onto nude mice: immunolocalization of human cells and characterization of extracellular matrix

Type I collagen is a clinically approved biomaterial largely used in tissue engineering. It acts as a regenerative template in which the implanted collagen is progressively degraded and replaced by new cell-synthesized tissue. Apligraf, a bioengineered living skin, is composed of a bovine collagen lattice containing living human fibroblasts overlaid with a fully differentiated epithelium made of human keratinocytes. To investigate its progressive remodeling, athymic mice were grafted and the cellular and the extracellular matrix components were studied from 0 to 365 days after grafting. Biopsies were analyzed using immunohistochemistry with species-specific antibodies and electron microscopy techniques. We observed that this bioengineered tissue provided living and bioactive cells to the wound site up to 1 year after grafting. The graft was rapidly incorporated within the host tissue and the bovine collagen present in the graft was progressively replaced by human and mouse collagens. A normal healing process was observed, i.e., type III collagen appeared transiently with type I collagen, the major collagen isoform present at later stages. New molecules, such as elastin, were produced by the living human cells contained within the graft. This animal model combined with species-specific immunohistochemistry tools is thus very useful for studying long-term tissue remodeling of bioengineered living tissues.

Evaluation of tissue-engineered skin (human skin substitute) and secondary intention healing in the treatment of full thickness wounds after Mohs micrographic or excisional surgery

BACKGROUND

Human Skin Substitute (Apligraf, Organogenesis, Inc., Canton, MA) is a bi-layered tissue-engineered living biological dressing developed from neonatal foreskin. It consists of a bovine collagen matrix containing human fibroblasts with an overlying sheet of stratified human epithelium containing living human keratinocytes. Human Skin Substitute (HSS) appears to be immunologically inert, and has shown usefulness in the treatment of chronic and acute wounds.

OBJECTIVE

Primary objectives were to evaluate the safety and efficacy of HSS in the treatment of full-thickness wounds in a prospective case series. Secondary objectives were to determine the rate of complete wound reepithelialization, incidence of complete wound healing, pain at wound site, overall cosmetic outcome, and patient satisfaction.

METHODS

Fourteen patients were enrolled in the study, of which 12 were evaluable. HSS was applied in a blinded fashion to 6 of the patients immediately following Mohs or excisional surgery for skin cancer. The remaining 6 patients were allowed to heal by secondary intention. Both groups were evaluated at weekly appointments until complete reepithelialization occurred. During each evaluation, wound quality was assessed through the Vancouver Burn Scar Assessment Scale by the investigator and an independent blinded dermatologist. The investigator, blinded observer, and patient further evaluated the cosmetic outcome of the wound through the use of a Visual Analog Scale over a 6-month period.

RESULTS

HSS patients and secondary intention patients were equivalent in comorbid factors such as pain, erythema, edema, exudate, infection, or hematoma between the groups. The incidence of complete wound healing at 6 months was 100% for both groups. Both groups also appeared to heal at similar rates, as defined by the complete reepithelialization of the wound. HSS patients ultimately resulted in more pliable and less vascular wounds as defined by the Vancouver Burn Scar Assessment Scale. Patient satisfaction with cosmetic outcome in both groups was positive at 6 months.

CONCLUSIONS

HSS appears to be a safe, well-tolerated biological dressing with equivalent comorbid factors to secondary intention healing. HSS, however, seems to produce a more pliable and less vascular scar than those developed through healing by secondary intention. HSS also appears to produce more satisfactory cosmetic results when compared to secondary intention healing.

Frozen cultured sheets of epidermal keratinocytes in reepithelialization and repair of the cornea after photorefractive keratectomy

PURPOSE

To determine whether frozen cultured sheets of human allogeneic epidermal keratinocytes (CEAK) improved wound repair after experimental corneal ablation by photorefractive keratectomy (PRK).

SETTING

Hospital "Luis Sanchez Bulnes" de la Asociación para Evitar la Ceguera en Mexico, I.A.P, and Department of Cell Biology, CINVESTAV-IPN, Mexico City, Mexico.

METHODS

Transepithelial PRK was performed in the right eye of male albino rabbits to obtain a 112 microm deep and 6.0 mm diameter ablation zone. In 17 eyes, the ablations were covered with frozen CEAK; in 11 eyes, the ablations were covered with a disposable contact lens without the cultured sheets; and in the control group (13 eyes), the ablations were not covered. Subepithelial fibrosis and reepithelialization of the ablated zone were evaluated in serial paraffin-embedded tissue sections from all wounds.

RESULTS

Treatment with CEAK reduced fibroblast proliferation and the inflammatory response beneath the ablated zone and produced better organization of the newly formed epithelium by eliminating significant hyperplasia or discontinuities in the periodic acid Shiff-stained basement membrane. It also led to accelerated reepithelialization.

CONCLUSIONS

The use of frozen CEAK as a biologically active wound dressing improved tissue repair at 1 month in corneas ablated by transepithelial PRK in the male albino rabbit model. Treatment with CEAK could improve the outcome of PRK in humans.

Human chronic wounds treated with bioengineered skin: histologic evidence of host-graft interactions

Bioengineered skin is being used to successfully treat a variety of wounds. Randomized controlled clinical trials have shown that a living bilayered skin construct (BSC), consisting of human neonatal keratinocytes and fibroblasts in a collagen matrix, was able to accelerate complete closure of both venous and diabetic ulcers. BSC was particularly effective in difficult-to-heal wounds of long duration. In patients treated with BSC, no obvious signs of gross clinical rejection were observed. Testing of these treated patients showed no BSC-specific immune response and no immune response to bovine collagen or alloantigens expressed on keratinocytes and fibroblasts. However, very little is known about the histologic changes that occur after BSC has been placed on human wounds. We report our preliminary histologic observations in this uncontrolled study of a cohort of 11 patients with 14 wounds treated with BSC in whom biopsy specimens of the grafted sites were obtained at least 2 weeks after application of the construct. The etiology of these ulcers varied from arterial or venous disease to an extensively and poorly healing burn wound. Histologically, thickening of the grafted bioengineered skin was seen in all samples where residual BSC could be identified. Mucin deposition was noted in the dermal layer of the wounds and BSC in 13 of the 14 specimens examined. Unexpectedly, and in spite of good clinical outcome, 4 of the 14 specimens exhibited a foreign body-like granulomatous response. There was no history of prior exposure to BSC in the 4 patients who had a granulomatous response. These early histologic observations suggest that stimulatory interactions develop between BSC and the wound. The consistently found deposition of mucin may point to a fetal pattern of wound repair associated with the neonatal cells in BSC.

Factors that influence healing in chronic venous ulcers treated with cryopreserved human epidermal cultures

BACKGROUND

Cryopreserved epidermal cultures (CEC) offer an "off the shelf" treatment for chronic wounds. These cultures are derived from neonatal foreskin and grow rapidly in vitro to form epidermal sheets. They do not require a biopsy from the patient, an advantage compared to autografts. They seem to act as a biological dressing, stimulating epithelialization from the wound edges and adnexae, probably through growth factor release.

OBJECTIVE

To summarize our recent experience with the use of CEC in chronic venous leg ulcers and to determine the factors that influence healing in chronic venous ulcers treated with CEC.

PATIENTS AND METHODS

A single arm, open label study including a total of 11 patients with documented venous ulcers was performed. The study involved the application of cryopreserved epidermal cultures every other week to nonhealing leg ulcers for a total of 12 weeks or until complete healing of the ulcer.

RESULTS

A total of 11 patients with one or more leg ulcers were treated. The average age was similar in healed and unhealed groups. Seven patients completely healed after an average of 4.14 CEC applications. Four patients did not heal after a total of 12 CEC applications.

CONCLUSION

Predictors for failure to heal after CEC application in our patients were long wound duration, wound size, presence of lipodermatosclerosis, and history of failed prior split-thickness skin grafts.

Cryopreserved cultured epidermal allografts achieved early closure of wounds and reduced scar formation in deep partial-thickness burn wounds (DDB) and split-thickness skin donor sites of pediatric patients

Burn treatment in children is associated with several difficulties, e.g. available skin replacement is small, donor area could expand, and subsequent hypertrophic scar and contracture could become larger along with their physical growth. In order to have better clinical results, the authors prepared cryopreserved cultured epidermal allografts from excess epidermal cells of other patients, and applied the epidermal allografts to 55 children, i.e. 43 cases of deep partial-thickness burn wounds (DDB) due to scald burn and 12 cases with split-thickness skin donor sites. In the 43 DDB patients, epithelialization was confirmed 9.1+/-3.6 days (mean+/-S.D.) after treatment. In 10 of the 43 patients, epithelialization was comparable between the area which received the epidermal allografts (grafted area) and the area which did not receive the epidermal allografts but was covered with usual wound dressing (non-grafted area). As a result, epithelialization day was 7.9+/-1.7 in grafted areas and 20.5+/-2.3 in non-grafted areas. In the 12 patients with split-thickness skin donor sites, epithelialization was confirmed 6.3+/-0.9 days after treatment. Epithelialization of the grafted and non-grafted areas was comparable in 8 of the 12 patients, and it was 6.5+/-1.1 days and 14.1+/-1.6 days, respectively. In these 10 DDB patients and 8 split-thickness skin donor site patients, redness and scar formation were also milder in the grafted area. The 55 patients have been followed up for 1-8 years (mean, 4.75 years), and scar formation was suppressed in both DDB and split-thickness skin donor sites. These findings showed that cryopreserved cultured epidermal allografts achieve early closure of the wounds and good functional outcomes.

Use of skin substitutes in dermatology

The use of skin substitutes to treat acute and chronic wounds should continue to increase as newer products are developed. The goals for the future are to eliminate the need for autografting, eliminate the risk for transmission of disease, improve the shelf life and simplify storage requirements, improve cosmetic outcomes, and reduce cost. A number of researchers are also looking to incorporate gene therapy into skin substitutes.

Use of a cell-based interactive wound dressing to enhance healing of excisional wounds in nude mice

The need to have viable, metabolically active cells to heal wounds is well recognized, because there is clear evidence that cellular dysfunction delays healing. This suggests that addition of metabolically active cells to a delayed healing tissue could enhance the healing of the tissue. Therefore, we examined the ability of an interactive wound dressing composed of human keratinocytes or fibroblasts grown on microporous bio-reactor beads and placed into a polyethylene bag to facilitate the delayed healing of wounds in nude mice. A 1 x 1 cm wound was made on the backs of nude mice, and the dressing with or without viable cells was placed on the wound for 8 to 24 days, with dressing changes every other day. Wound area and time to heal measurements were compared after various interventions including freeze-thawing. The data shows that the interactive wound dressing was more effective than the control dressings (p<0.05) and that keratinocytes were more effective than fibroblasts in wound healing (p<0.05). Freezing-thawing of the interactive wound dressings destroyed the activity of the dressing. Studies examining cells using a live/dead viability assay showed that both keratinocytes and fibroblasts were alive after 2 days on the mice. Surprisingly, human fibroblasts appeared to exhibit bridging behavior that is indicative of fibroblast proliferation. We conclude that a simple interactive wound dressing using either keratinocytes or fibroblasts can enhance the healing of wounds in nude mice.

Tissue-engineered product: allogeneic cultured dermal substitute composed of spongy collagen with fibroblasts

Recently, various types of allogeneic skin substitutes including cultured epidermal substitute (CES), cultured dermal substitute (CDS), and cultured skin substitute (CSS), which are composed of keratinocytes and/or fibroblasts as the cellular component(s), have been used as biological wound dressings. In our study, the allogeneic CDS was prepared by plating fibroblasts on a spongy collagen. The clinical evaluation was conducted using fresh or cryopreserved allogeneic CDS. In 145 of our clinical cases, 95% (138/145) of various wounds were evaluated as achieving good or excellent results, including 96% (22/23) of deep dermal burns (DDB) and dermal burns (DB), 100% (53/53) of partial-thickness donor wounds, 91% (21/23) of traumatic skin defects, 100% (5/5) of pressure ulcers, 82% (9/11) of chronic skin ulcers, 100% (6/6) of coverage for debrided DB, and 92% (22/24) of coverage for autologous meshed graft. The results obtained in our study suggest that the allogeneic CDS is able to provide an effective therapy for patients with partial and/or full-thickness skin defects.

Management of leg ulcers

Leg ulcer is a leading cause of morbidity among older subjects, especially women in the Western world. About 400 years BC, Hippocrates wrote, "In case of an ulcer, it is not expedient to stand, especially if the ulcer be situated on the leg". Hippocrates himself had a leg ulcer. The best treatment of any leg ulcer depends upon the accurate diagnosis and the underlying aetiology. The majority of leg ulcers are due to venous disease and/or arterial disease, but the treatment of the underlying cause is far more important than the choice of dressing. The aetiology, pathogenesis, treatment, and the future trends in the management of the leg ulcers are discussed in this review.

Can we produce a human corneal equivalent by tissue engineering?

Tissue engineering is progressing rapidly. Bioengineered substitutes are already available for experimental applications and some clinical purposes such as skin replacement. This review focuses on the development of reconstructed human cornea in vitro by tissue engineering. Key elements to consider in the corneal reconstruction, such as the source for epithelial cells and keratocytes, are discussed and the various steps of production are presented. Since one application of this human model is to obtain a better understanding of corneal wound healing, the mechanisms of this phenomenon as well as the function played both by membrane-bound integrins and components from the extracellular matrix have also been addressed. The analysis of integrins by immunohistofluorescence labelling of our reconstructed human cornea revealed that beta(1), alpha(3), alpha(5), and alpha(6) integrin subunits were expressed but alpha(4) was not. Laminin, type VII collagen and fibronectin were also detected. Finally, the future challenges of corneal reconstruction by tissue engineering are discussed and the tremendous applications of such tissue produced in vitro for experimental as well as clinical purposes are considered.

Advances in wound care and healing technology

Wounds are unique in so far as no disease process other than wounds would have existed from the beginning of mankind. Over the years, the management of wounds, especially that of chronic wounds, has had enormous social and economic implications worldwide. With an aging population, this impact is likely to increase. In recent years, this has been reflected by the birth and rapid growth of the new speciality of 'wound healing'. Continuous advances made in the study of the wound microenvironment, an ever-broadening understanding of the pathophysiology of wounds, and improved techniques in monitoring the response of healing have led to continuing developments in the treatment of chronic wounds. Current research focuses on growth factors and human skin substitutes that provide promising results. This article reviews advances made in wound care management over the years. Despite all these advances, it must be borne in mind that basic principles of wound care in a multidisciplinary team setting still remain the backbone of wound management.

Skin grafting

No longer an option of last resort, skin grafting has become a technique that is routinely and sometimes preferentially considered as skin replacement for burns, chronic ulcers, and skin defects after cutaneous surgical procedures. When selected as the best alternative for wound closure, autologous skin grafts are commonly considered the gold standard. Availability of autologous grafts is a major obstacle, however, and the search for a manufactured skin replacement has continued. In cases in which autologous grafts cannot be performed, skin substitutes have become an attractive alternative.

Clinical application of cultured oral epithelium for palatal wounds after palatoplasty: a preliminary report

OBJECTIVE

Mucoperiosteal defects of the hard palate after palatoplasty scar causing scar contraction, leading to poor growth of the maxilla. The promotion of wound healing in these cases through cultured epithelial allografting has been reported. Cultured epithelial allografting was done using allogeneic cultured cells, in the hope of improving growth of maxilla.

SUBJECTS AND METHODS

Clefts of the soft and hard palate (seven patients), and a cleft of the soft palate (two patients) were present. Average patient age was 1 year 4 months. Palatoplasty was done by a conventional push-back operation. Oral epithelial cells from healthy adults were cultured using 3T3 cells as the feeder layer. After 3 weeks, cultured oral mucosal epithelium was grafted on a raw surface following palatoplasty.

RESULTS

The result was compared in two patients who had undergone push-back operation only. In all patients, the grafted areas underwent re-epithelialization after about 1 week and did not exhibit any clinical signs of graft rejection. Grafted areas healed completely after 2-3 weeks in all cases.

CONCLUSION

Cultured epithelial allografts serve as a temporary biological dressing, and accelerate epithelialization and wound healing. Allografting by cultured oral epithelium has proved to be a very useful therapeutic modality in palatoplasty, as well as effective augmentation materials in cases of oral mucosal defects.

Frozen human epidermal allogeneic cultures promote rapid healing of facial dermabrasion wounds

BACKGROUND

Clinical studies have shown that cultured human epidermal allogenic sheets promote faster reepithelization of skin donor sites and deep partial-thickness wounds.

OBJECTIVE

We describe the results of a controlled, clinical study of facial dermabrasion sites treated with a single application of frozen cultured human allogenic epidermal sheets that were thawed for 5-10 minutes at room temperature before application.

METHODS

Ten patients with scars from acne or of other etiology underwent facial dermabrasion. One side of the face was treated with the frozen and thawed cultures, the other side was treated with standard dry dressing.

RESULTS

The epidermal cultures promoted faster reepithelization of the wounds, with complete reepithelization in an average time of 4.6 days, whereas controls healed in an average of 7. 9 days. The reduction in healing time was 42% (P = 4.82 x 10(-7)). Pain was reduced in sites treated with the thawed cultures.

CONCLUSION

Epidermal allogenic cultures, preserved by freezing, promoted significantly faster reepithelization and reduced pain intensity of dermabraded facial wounds, suggesting that they could be used routinely to improve the recovery from dermabrasion.

Frozen allogeneic human epidermal cultured sheets for the cure of complicated leg ulcers

BACKGROUND

Skin ulcers due to venous stasis or diabetes are common among the elderly and are difficult to treat. Repeated applications of cell-based products have been reported to result in cure or improvement of leg ulcers of small size in a fraction of patients.

OBJECTIVE

To examine the effects of frozen human allogeneic epidermal cultures for the treatment of acute and chronic ulcers.

METHODS

We treated a series of 10 consecutive patients with leg ulcers of different etiology and duration with frozen human allogeneic epidermal cultures stored frozen and thawed for 5-10 minutes at room temperature before application. Three patients had ulcers with exposed Achilles or extensor tendon. The ulcers treated were as large as 160 cm2 in area and of up to 20-years' duration. After preliminary preparation of the wounds by debridement to remove necrotic tissue and application of silver sulfadiazine to control infection, thawed cultures were applied biweekly from 2 to 15 times depending on the size and complexity of the ulcer.

RESULTS

All ulcers healed, including those with tendon exposure. After the first few applications, granulation tissue formed in the ulcer bed and on exposed tendons, and epidermal healing took place through proliferation and migration of cells from the margins of the wound. The time required for complete healing ranged from 1 to 31 weeks after the first application.

CONCLUSION

The use of frozen human allogeneic epidermal cultures is a safe and effective treatment for venous or diabetic ulcers, even those with tendon exposure. It seems possible that any leg ulcer will be amenable to successful treatment by this method.

Allogeneic cultured dermal substitute composed of spongy collagen containing fibroblasts: evaluation in animal test

The authors developed a cultured dermal substitute (CDS) composed of a spongy collagen containing cultured fibroblasts. The cultured fibroblasts derived from Sprague Dawley rat skin were seeded on a spongy collagen at a density of 5 x 10(5) cells cm(-2) and cultured for 7 days. This CDS was applied to the debrided wound of full-thickness burn which was inflicted experimentally on the dorsum of Wister rat, and then the wound conditions were observed over a period of 2 weeks. The comparative study was conducted using an acellular spongy collagen as well as a commercially available temporary wound dressing, Biobrane, since a different type of cultured dermal substitute, Dermagraft-TC, is composed of Biobrane, whose inner site is combined with cultured fibroblasts. Each covering material was applied on the debrided wound area and exchanged by new one 1 week later. When the debrided wound was covered with Biobrane, a small portion of necrotic tissue was observed 1 week after application, and the granulation tissue formation was greatly delayed. This wound area showed a poor granulation tissue even 2 weeks later. On the contrary, when covered with an acellular spongy collagen, no necrotic tissue was observed. This wound area showed a more or less irregular granulation tissue at 1 week and then a healthy granulation tissue 2 weeks later. This preliminary comparative study suggests that an acellular spongy collagen is able to function as a more suitable matrix for CDS, compared with Biobrane. The wound area covered with a CDS assumed a moist, shiny, and hyperaemic appearance 1 week after application showing a healthy granulation tissue. The macroscopic evaluations indicate that the CDS is able to prepare a healthy granulation tissue at an earlier stage, compared with the acellular spongy collagen. In addition, the histologic views demonstrate that the CDS is able to prepare a thicker and denser granulation tissue, compared with the acellular spongy collagen. Although the fate of cultured fibroblasts in the CDS on the wound surface within 1 week is not clear, these findings suggest that fibroblasts in CDS are able to provide excellent conditions for wound healing.

Neovagina with cultured allogenic epidermal sheets

Several materials have been used in neovagina construction, but most of them show some kind of drawback. This is the report of a case in which cultured allogenic epidermal sheets were used instead of skin grafting for a McIndoe procedure.

Characterization of epidermal wound healing in a human skin organ culture model: acceleration by transplanted keratinocytes

Few data are available on early regeneration of human epidermis in vivo. We have established a supravital skin organ culture model for epidermal wound healing by setting a central defect (3 mm diameter) in freshly excised skin specimens and culturing under air exposure. Re-epithelialization was followed for up to 7 d by histology and immunohistologic analysis of various markers for differentiation and proliferation. In 12 of 19 cases (63%; 5% fetal calf serum) or six of 21 cases (29%; 2% fetal calf serum), the wounds were re-epithelialized spontaneously after 7 d. After transplantation to the wounds of 1-2 x 10(6) dissociated allogenic cultured epidermal or about 1 x 10(6) autologous outer root sheath keratinocytes, 18 of 21 cases (86%; 5% fetal calf serum) or 17 of 21 cases (81%; 2% fetal calf serum) were healed within the same period. Histologically, early neoepithelium (3 d) was disordered after keratinocyte transplantation, whereas later (7 d) it had gained a more ordered stratification, exhibiting a thin discontinuous granular and a compact horny layer. At this stage, not only hyperproliferative (CK 6) but also, abundantly, maturation-associated cytokeratins (CK 1, CK 10) were detected immunohistochemically. Analyses of regenerated epidermis after transplantation of (i) keratinocytes labeled in vitro with BrdU and (ii) heterosexual keratinocytes by immunohistochemistry and fluorescence in situ hybridization for the Y chromosome, respectively, clearly showed that external keratinocytes are physically integrated into the regenerated epidermis and extendedly contribute to its formation. The data presented here demonstrate improvement and acceleration of epidermal re-epithelialization by transplantation of keratinocytes.

A novel culturing and grafting system for the treatment of leg ulcers

The purpose of this study was to develop and test an efficient culturing and grafting system for the treatment of leg ulcers. The culturing system consisted of a Petriperm culture vessel (20 cm2) aseptically placed in a larger standard Petri dish (60 cm2). Skin cultures were established and cultivated in the Petriperm dish. The cells grew on the bottom of the Petriperm dish, which was made of a gas-permeable 25-micron thick transparent Teflon film. Grafts were produced simply by cutting the film from the bottom of the Petriperm dish with a scalpel. The system was used to produce subconfluent epidermal autografts which were used to heal a 32 cm2 chronic rheumatoid arthritis leg ulcer. The cultured autografts were transferred cell side down on to the cleaned wound bed without an enzymatic digestion. The grafts consisted of autologous keratinocytes, melanocytes and fibroblasts. Caution was taken not to disturb the wound bed for 7-9 days at which time the Teflon film was removed. The wound closed 2 weeks after the last grafting and has remained closed for more than a year post-treatment. The culturing and grafting system presented here will make it possible to develop cellular-based therapies that were previously not possible.

Genetically modified human keratinocytes overexpressing PDGF-A enhance the performance of a composite skin graft

Skin loss due to burns and ulcers is a major medical problem. Bioengineered skin substitutes that use cultured keratinocytes as an epidermal layer with or without analogues of the dermis are one strategy for skin repair. However, none can achieve definitive wound closure, function, or cosmesis comparable to split-thickness autografts. Moreover, autograft donor sites, which require time to heal, may be limited or have attendant problems such as infection or functional/cosmetic deficiencies. To determine if the performance of composite skin grafts of keratinocytes on a dermal analogue could be enhanced, human keratinocytes were genetically modified to overexpress platelet-derived growth factor A chain (PDGF-A). Composite grafts of modified keratinocytes seeded onto acellular dermis, prepared from cryopreserved cadaver skin, secreted PDGF-AA protein in vitro [90 ng/graft (1.5 x 1.5 cm)/24 hr]. To test their performance in a wound healing model, composite grafts were transplanted to full-thickness excisional wounds on the back of athymic mice. PDGF-A grafts formed a stratified differentiated epidermis similar to control grafts. The acellular dermis was repopulated with host fibrovascular cells and by day 7, the PDGF-A grafts had significantly more cells in the dermis and increased staining for murine collagen types I and IV. At this early time point, wound contraction was also significantly inhibited in PDGF-A grafts versus control grafts. Thus, PDGF-A overexpression improves graft performance during the first critical week after transplantation.

Burns (Part 2). Tops and flops using cultured epithelial autografts in children

The goal of this article is to review the status of cultured epithelial autografts in clinical practice with particular focus on the pediatric subset of patients. The current indications include massive deep burns (>60 - 70% total body surface area), resurfacing-type postburn scar revisions, and skin defect coverage following excision of large skin lesions like giant nevi. Although this method can be lifesaving for massively burned patients, and although excellent functional and cosmetic results may be obtained under ideal circumstances, formidable problems continue to exist. Take is inconsistent, cultured grafts are extremely susceptible to infection, and skin breakdown during the first months post grafting may occur due to mechanical instability of the regenerating skin. It may take one more decade of concerted research, jointly performed by clinicians and tissue culture technology experts in order to fabricate more skin-like grafts which are robust, reliable, and less expensive. Then, "cultured skin" will conquer the world and benefit countless patients.

Tissue engineering and the development of Apligraf, a human skin equivalent

In recent years, skin grafting has evolved from the initial autograft and allograft preparations to biosynthetic and tissue-engineered living skin replacements. This review details the pioneering work of numerous investigators that led to the following precursors of tissue-engineered skin replacement: cultured autologous keratinocyte grafts, cultured allogeneic keratinocyte grafts, autologous/allogeneic composites, acellular collagen matrices, and cellular matrices. It also discusses the rationale for the development of the newer products and describes the technical advances leading to the development of Apligraf, a tissue-engineered human skin product.

The enhancement of wound healing with human skin allograft

Although clean incisional wounds can be closed easily, contaminated wounds, wounds with tissue loss that cannot be closed primarily, and chronic wounds are generally not closed and suffer the effects of being open. It follows that wound healing would be enhanced if these wounds could be closed. This article describes how skin allograft biologic dressings are used to close such wounds temporarily to bestow the benefits of wound closure. It also describes the benefits of human skin allografts and the history and basic science related to their use. Reference is made to newer wound covers that have the potential to provide similar benefits to open wounds.

What is new in clinical research in wound healing

Treating the underlying pathophysiology of the wound remains of utmost importance. Several new treatment modalities may soon be available as adjunctive treatments. The efficacy of some remains to be established in well-controlled clinical studies.

Controlled clinical study of skin donor sites and deep partial-thickness burns treated with cultured epidermal allografts

Two clinical studies in donor sites and deep partial-thickness burns treated with banked cultured human epidermal allografts are described. Ten burn patients were subjected to donor split-thickness skin harvesting. The study was controlled, side-by-side comparative, blind, and randomized. Banked cultured epidermal allografts promoted a faster reepithelialization of the wounds; they epithelialized in an average of 6.9 days, whereas controls healed in an average of 11.1 days, giving a reduction of 37.8 percent in time to heal (p < 0.005). Allografted sites were less erythematous as compared with controls (p < 0.01), with more tendency to normopigmentation. In the deep partial-thickness burns study, 10 patients with 18 burned wounds were treated. Wounds treated with cultured allografts showed complete reepithelialization in about 3 to 6 days. The two clinical studies showed that banked cultured epidermal allograft promotes a significantly faster epithelialization of donor sites and deep partial-thickness wounds. These results support the idea that cultured allografts should be used routinely to improve treatment of burn patients and reduce their therapy time.

Surface electrical capacitance as a noninvasive index of epidermal barrier in cultured skin substitutes in athymic mice

Restoration of an epidermal barrier is a definitive requirement for wound closure. To determine formation of an epidermal barrier as a function of hydration of the stratum corneum, we measured surface electrical capacitance (SEC) of the epidermis in cultured skin substitutes (CSS) in vitro and after grafting to athymic mice. CSS were prepared from human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan substrates. On culture days 3, 7, 14, 17, and 21, SEC was measured in situ. CSS (n = 18; mean +/- SEM) showed a time-dependent decrease of SEC (picoFarads, "pF") from 4721 +/- 28 pF on day 3 to 394 +/- 117 pF on day 14, and subsequent increase to 1677 +/- 325 pF on day 21. After 14-d incubation, parallel CSS samples (n = 5) or murine autografts (n = 5) were grafted orthotopically to athymic mice. After grafting, CSS showed decreases in SEC from 910 +/- 315 pF at 2 wk to 40 +/- 10 pF at 4 wk with no significant decreases thereafter. Control values for murine autograft were 870 +/- 245 pF at 2 wk, and 87 +/- 30 pF at 4 wk. SEC values for native murine skin (n = 10) were 91 +/- 18 pF, and for native human skin (n = 10) were 32 +/- 5 pF. The data demonstrate that SEC decreases with time in culture and that healed or intact skin has approximately 10- to 100-fold lower SEC than CSS in vitro. This noninvasive technique provides a quantitative index of epidermal barrier in CSS in vitro and demonstrates the development of functional epidermal barrier during healing of wounds treated with cultured skin substitutes.