Edward C. Robb

Storage media and temperature maintain normal anatomy of cadaveric human skin for transplantation to full-thickness skin wounds

Cadaveric human skin provides an optimal temporary cover after early excision of full-thickness burns; however, engraftment is reduced greatly by cryopreservation. Refrigerated skin is generally preferred because of its rapid revascularization, presumably caused by its greater viability. In this study, the effects of storage solutions, temperature, and the changing of the storage media on skin graft anatomy were evaluated as an indicator of graft viability. Split-thickness human skin grafts (0.012-0.015 mm) were retrieved from cadaveric donors and grafted to circumferential, full-thickness skin wounds on athymic mice. After clinical determination of engraftment 3 months after grafting, 6-mm punch biopsy samples of the human skin were harvested and separated into two groups. Biopsy samples were stored in either saline or Eagles minimal essential medium. Media were not changed or were changed every 3 days. All groups were stored at either 4 degrees C or room temperature (RT). After 5, 10, and 21 days of storage, biopsy samples were grafted onto athymic mice for 20 days. The biopsy grafts were then collected and prepared for histologic scoring on a scale of +4 (normal anatomy) to 0 (no epithelial cells). Significant differences in histologic scores were found by the nonparametric Kruskal-Wallis test followed by Wilcoxon pairwise comparison. Skin stored in media maintained better histologic anatomy than skin in saline, suggesting better maintenance of viability. There was also better preservation of anatomy after storage at RT for 21 days with media changes every 3 days when compared to unchanged media and all conditions at 4 degrees C. These results support the hypothesis that increased availability of nutrients and increased storage temperature maintain higher viability of cadaveric human skin for transplantation to full-thickness cutaneous wounds.

A New Model for Studying the Development of Human Hypertrophic Burn Scar Formation

Hypertrophic scar formation remains the major problem for severely burned patients who survive their injuries. This scarring can result in both cosmetic and functional deformities. One of the major problems in dealing with this complication is the lack of an adequate animal model with which to test various possible therapeutic modalities. We describe an animal model that uses human skin applied to the backs of nude mice to investigate the problem. Immunosuppression is not necessary in this model since the nude mouse lacks a thymus gland and is therefore not able to reject the skin. With this model we have been able to achieve contracture of meshed normal human skin grafts and hypertrophic scar formation in normal human skin that was burned a month after grafting to the mouse. We have also had success in grafting human hypertrophic scars, obtained from burn patients, to the mice. This model offers unique opportunities for investigation of the cause and treatment of burn scars in humans.

Observations on stability and contraction of composite skin grafts: xenodermis or allodermis with an isograft overlay.

Composite skin grafts of xenodermis or allodermis with a thin split-thickness isograft overlay were evaluated for stability and contraction. Male inbred Lewis rats were used as recipients, with Buffalo rats serving as allogeneic dermis donors. Cryopreserved human skin was used for xenodermis grafts. The two components of the composite graft, the xenodermis or allodermis and the isograft overlay, were grafted in one operation to a surgically created wound. Wounds were observed for 1 year. The composite skin grafts took fairly well, although spotty loss of the overlaid isograft was noted. The xenodermis and allodermis remained grossly intact even at 1 year after grafting. However, composite skin grafts in this animal model contracted more than did sheet isografts alone.

Prospective clinical study of Hydron, a synthetic dressing, in delivery of an antimicrobial drug to second-degree burns.

This clinical trial prospectively evaluates the potential beneficial effects of antimicrobial drug delivery from a synthetic dressing (Hydron-AgSD) formed on second-degree burn wounds. A paste composed of polyethylene glycol-400, poly 2-OH ethylmethacrylate, and silver sulfadiazine (AgSD 1%-3%) matured within one hour to form a solid dressing. In 27 patients, comparable areas of second-degree wounds on the same patient were selected at random for test and control (silver sulfadiazine 1% only) sites. The mean total time of the synthetic dressing application per patient was about nine days, and each dressing remained in place for nearly four days. During this interval the control sites required four dressings changes. In 17 tests for infections, the control areas were contaminated but no bacteria were detected under the synthetic dressing; in three tests, the controls had no bacteria, whereas the synthetic dressing did. Healing of burns was similar under both types of dressing. Benefits of Hydron treatment included increased patient comfort because of the reduced number of dressing changes and, in some cases, greater freedom from contaminating bacteria.

The expression of cytokines, growth factors and ICAM‐1 in the healing of human cutaneous xenografts on nude mice

Abstract We postulate that wound healing is an orderly process mediated by a programmed expression of cytokines and growth factors. We suggest that these factors are produced in a consistent sequence, in regulated quantities and eliminated when their function is complete. We report here the results of studies on several cytokines, growth factors and the intercellular adhesion molecule expressed during the healing of human skin grafted onto athymic nude mice. Signs of healing of grafts were visible clinically around 3–5 days post‐graft and were completed by 4 weeks post‐graft. During the Ist 2 weeks, we observed the following, (i) K‐14 keratin was prominent throughout the entire epidermis. Thereafter it was limited to basal cell layers, (ii) Langerhans cells were not detectable wilh anti‐human CDIa antibodies during the first week of healing but were clearly detectable 2 weeks post‐graft, (iii) DOPA (dihydroxy phenyl‐alanine) positive melanocytes gradually increased with time. The epidermis 21 to 28 days post‐graft clinically and histologically seemed to be morphologically intact. Interleukin‐l (IL‐I) was clearly detected in some basal cells of the epidermis, especially in melanoeytes and some keratinocytes during the early stage of healing. Transforming growth factor‐α: (TGF‐(α) was detected in epidermis first in melanocytes and some kera‐tinocytes shortly after grafting and again in the late stage of healing. It was also found in some dermal cells. Its expression coincided wilh kera‐tinocyte proliferation and melanocyte migration. TGF‐β was strongly ex‐pressed in the epidermis and dermis after the first week post graft, (iv) ICAM‐1 was transiently expressed only at the onset of healing. We previously reported that pro‐opiomelanocortin and its derivatives MSH/ACTH are expressed strongly during the healing of human xenografts. The 4 additional molecules which are the subject of this report all are ex‐pressed in healing human skin in a predictable sequence and quantity (intensity of stain). Together these data support our hypothesis that healing is a highly regulated process mediated by numerous cytokines.

Comparison of Scar Contracture with the Use of Microskin and Chinese-Type Intermingled Skin Grafts on Rats

Wounds that were measured precisely 4 x 5 cm in size were created over the dorsal surfaces of rats. The defects were grafted with the use of either the microskin or Chinese technique of intermingled auto/allograft with an expansion ratio of 10:1. The size of the grafted wound of each rat was recorded on the fifth graft day after grafting and then weekly for 11 weeks. The extent of scar contracture on each rat was calculated weekly as a percentage of the original size. The results showed that the scar contracture associated with the Chinese type of intermingled auto/allograft transplantation was less than that associated with the microskin technique. The healing process in both forms of grafting was uneventful.

Evaluation of the effect of topical steroids on human scar contracture using a nude mouse model.

Adult nude mice had 1.5 to 1.0 meshed split-thickness human skin applied to an excised area of their back. The animals were then randomized into two groups, one of which had a steroid cream applied to their graft on alternate days. The other group had no ointment applied and served as a control. The wounds were measured on a weekly basis and the rate of wound contracture was found to be identical. Topical steroids would thus appear to offer no benefit in the prevention of scar contracture.