Patterns of reinnervation and blood flow in split-skin grafts

One of the most important functions of skin is thermoregulation. The alterations in the patterns of blood flow in skin is one of the main physiological processes responsible for thermoregulatory control. The mechanisms governing the thermoregulatory control of cutaneous blood flow are mainly neural and chemical in nature. At present, there is a lack of studies in the literature looking at the relationship between reinnervation and the blood flow pattern of skin grafts. The present study uses Laser Doppler flowmetry and the immunohistochemical stains protein gene product 9.5, calcitonin gene-related peptide and substance P to identify nerve fibres, and antibodies to CD31 and von Willebrand factor to identify endothelial tissues. The aim of the present study was to investigate the patterns of blood flow and nerve tissue regeneration in split-skin grafts up to 15 years following the original procedure. Thirty-two split-skin grafts were studied and these were placed into two groups based on the nature of the bed of excision: group I consisted of patients who underwent tangential excision and split-skin grafting (n=17), and group II consisted of patients with split-skin grafts placed onto fascial beds (n=15). Each subpopulation of patients was further divided into three groups based on the length of time following grafting: one to three years, four to six years and seven to 15 years. These divisions were arbitrarily chosen and called A1, A2 and A3, respectively. In the Laser Doppler flowmetry arm of the study, the grafts were assessed at various stages after heating, cooling and further reheating. The Laser Doppler flowmetry studies showed that, on subjecting the skin grafts in both groups I and II to heating and cooling followed by reheating, the overall response of the blood flow to changes in the temperature was slower. The immunohistochemical analysis showed that in all graft types and graft ages, protein gene product 9.5, calcitonin gene-related peptide and substance P stains demonstrated a relative lack of the presence of nerve fibres in the split-skin grafts compared with the control ('normal' skin). However, von Willebrand factor and CD31 immunological staining demonstrated that vessels were present in the split-skin grafts, with no significant difference in size or quantity from the control samples. It was found that the blood flow in the split-skin graft in response to thermal challenge, although present, was slower than that of normal skin, a finding which was independent of the age of the skin graft. It is thought that this was related to a lack of regeneration of nerve fibres and, hence, a deficiency in the neurally mediated reflexes of the blood vessels within the split-skin grafts.