[Experiment research on the mechanism of skin contracture after expansion]

The aim of this study is to observe the repairing process of skin chronic injury due to expansion and explore the mechanism of skin contracture after expansion.

20 dogs used in this study were divided randomly into four groups. Skin samples were collected from the back of dogs when expansion finished and 3 months, 6 months, 1 year after expansion. Normal skim from the other side on the back of dogs was used as control group. The dermal ultrastructure was observed by electriscope. The expression of alpha-SMA in dermis at different stage has been analyzed by immunohistochemistry, and the concentration of intracellular free Ca2+ in the fibroblast has been measured by Fura-2 fluorescen indicator. Meanwhile we constructed a 3-dimension system in vitro to analyze the afgfect of different cell density and collagen concentration to fibroblast contracture.

(1) The microfilment in fibroblast was fragile, and the features of myofibroblast was absent, the collagen fibers were returned to reticular arrangement along with time. One after expansion few of the collagen remained irregular in arrangement and aparse. (2) After expansion the concentration of Ca2+ increased significantly. (3) In 3-D culture system the density of fibroblasts positively corresponded to fibroblast contracture and the collagen concentration negatively corresponded to it.

After expansion the dog skin has a structure between scar tissue and thoroughly regeneration skin. Dermal fibroblast is the dynamic source of the skin contracture, meanwhile the density of fibroblast and collagen concentration are two essential factors during skin contracture.