Accelerated healing with a mesh autograft/allodermal composite skin graft treated with silver nylon dressings with and without direct current in rats.

PURPOSE: Evaluation of the healing and persistence of a meshed composite skin graft applied without immunosuppression. METHODS: The contraction of wounds grafted with 9:1 split-thickness autograft/1.5:1 allodermal mesh composite skin grafts (auto/allo MCSGs) was investigated. No immunosuppressive agent was applied. Male ACI rats and female Lewis rats reciprocally served as allodermis graft donors and recipients. Autograft/dermal autograft and allograft/dermal allograft MCSGs were the controls. RESULTS: AT 3 months after grafting, when epithelized auto/allo MCSG wounds were measured by computerized morphometric analysis, the silver nylon (SN) dressing group displayed less contraction than the Vaseline (petroleum jelly) dressing group (p < 0.003), and direct current treatment (SNDC) was more effective than SN (p < 0.005). The histologic structures of the hair follicles appear to confine the rejection process to the allogeneic follicles of the graft. The focal nature of the rejection process and the relatively low antigenicity of the dermal matrix allowed the survival of the allodermis layer. Although direct current significantly enhanced MCSG healing, SN and SNDC were not the immunosuppressive agents that were confirmed. CONCLUSION: This type of MCSG can heal without immunosuppressive treatment.

Apoptosis and accidental cell death in cultured human keratinocytes after thermal injury.

The respective roles of apoptosis and accidental cell death after thermal injury were evaluated in normal human epidermal keratinocytes. By coupling the LIVE/DEAD fluorescence viability assay with the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method and ultrastructural morphology, these two processes could be distinguished. Cells were grown on glass coverslips with a microgrid pattern so that the results of several staining procedures performed sequentially could be visualized in the same cells after heating at temperatures of up to 72 degrees C for 1 second. After exposure to temperatures of 58 to 59 degrees C, cells died predominantly by apoptosis; viable cells became TUNEL positive, indicating degradation of DNA. After exposure to temperatures of 60 to 66 degrees C, both TUNEL-positive viable cells and TUNEL-positive nonviable cells were observed, indicating that apoptosis and accidental cell death were occurring simultaneously. Cells died almost immediately after exposure to temperatures above 72 degrees C, presumably from heat fixation. The fluorescent mitochondrial probe MitoTracker Orange indicated that cells undergoing apoptosis became TUNEL positive before loss of mitochondrial function. Nucleosomal fragmentation of DNA analyzed by enzyme-linked immunosorbent assay and gel electrophoresis occurred after exposure to temperatures of 58 to 59 degrees C. The characteristic morphological findings of cells undergoing apoptosis, by transmission electron microscopy, included cellular shrinkage, cytoplasmic budding, and relatively intact mitochondria. Depending on temperature and time of exposure, normal human epidermal keratinocytes may die by apoptosis, accidental cell death, or heat fixation.