QUANTITATIVE STUDY ON THE EXPRESSION OF MMP1 AND TIMP1 IN NORMAL AND RADIATION- COMBINED WOUND HEALING AND ITS EFFECTS ON THE HEALING PROCESS

QUANTITATIVE STUDY ON THE EXPRESSION OF MMP1 AND TIMP1 IN NORMAL AND RADIATION- COMBINED WOUND HEALING AND ITS EFFECTS ON THE HEALING PROCESS

Aim: To study the expression of MMP1 and TIMP1 in normal and radiation- combined wound healing and their effects on the healing process. Materials and Methods: A rat model of radiation - combined wound healing was used, and routine light microscopy, electron microscopy, immunohistochemistry, and in situ hybridization were used to detect the expression of MMP1 and TIMP1 during the healing process. Results:The wound healing process was impaired and delayed. In rats receiving 25Gy Gamma ray locally, the irradiated wounds healed 6 days later than non - irradiated controls. The following changes were found in the expression of MMP1 and TIMP1: ( 1 ) In the early inflammatory phase and in the period of granulation tissue formation, MMP1 expression was only slightly if at all affected in the newly - formed epidermis of irradiated wounds when compared with that in controls. Later, the epidermal expression of MMP1 in irradiated wounds was comparatively increased following the delayed healing process. 3 to 14 days after wounding, TIMP1 was weakly positive in proliferating keratinocytes of control group and became negative after epidermal covering, whereas no or only slight epidermal expression was detected in the irradiated group before epidermal covering. (2) The expression of MMP1 and TIMP1 in irradiated group was markedly decreased in fibroblasts, endotheliocytes and macrophages when compared to that in controls. The expression phase was prolonged due to the delayed healing process. Conclusions: It is concluded that the reduced expression of MMP1 and TIMP1 in granulation tissue retards such impertant processes as cell migration and angiogenesis, thus slowing the healing process. The expression of MMP1 in the newly - formed epidermis may help the process of reepithelialization, but in the late healing period, overexpression of MMP1 and decreased expression of TIMP1 in the epidermis may hinder the establishment of basal membrane and scar formation.