Biological Changes After Transplantation Of Expanded Skin: Experimental Study And Clinic Observation

Skin soft-tissue expansion has become a widely used technique in plastic and reconstructive surgery. A lot of studies have revealed the histological, ultrastructural, biochemical, biomechanical, cell-kinetic and hemodynamic alterations of expanded skin, but few documents involved the changes after transplantation of it. The aim of this work was to study the biological changes after transplantation of expanded skin.Part Ⅰ. Experimental studyMethods 8 adult dogs (average weight 14.5kg at beginning of the experiment) were used. On each animal's back, four 150ml rectangular expanders were implanted beneath the skin and panniculus carnosus bilaterally under general anesthesia. Two of them were selected as controls. Expanders were filled to capacity by weekly injections over a 8-week period.One week after the final injection, expanded flaps were raised and replaced its bed without tension after the skin samples were taken from the distance. In the control groups, the specimens were taken as above at one side of dogs, another side, flaps were elevated and sutured in place. Then, dots 1cm apart were tattooed around the flaps.8 dogs were then divided into four groups. Each group included 2 dogs. 3 weeks, 6 weeks, 3 months and 6 months after inset of the flaps respectively, the skin-flap area were measured with computer and the specimens were taken to perform the following procedures: (1) histological examination stained with HE, (2) ultrastructural observation under transmission electron microscope, (3) the quantity and functional express of myofibroblast by immunohistochemical staining with a monoclonal α -SM actin antibody, (4) testing biomechanical properties of the skin in three parameters ( stress-strain, stress relaxation, tensile strength), (5) determining collagen content of the skin biopsies.Results (1) The expanded flap had a mean 10% area contraction comparing the controls at 6 months after flap inset. The contraction of expanded skin has maintained 3 months. (2) The epidermis became significantly thicker than that of controls after expansion (p<0.05) and returned to normal 6 months post the flap inset. The dermis was significantly thinner after expansion (p<0.05), 6 months later, the dermis had almost identical thickness to that of before expansion. No residual capsule was found 6 months after removal of expanders. (3) The ultrastructural study revealed the following changes. In the epidermis, the basal cells contained group of tonofilaments, mitochondria with increased number. Intracellular spaces in all layers of expanded epidermis were much more reduced. The expanded dermis contained large bundles of compacted collagen fibers which lined in disorder, active fibroblasts. A few...