[Experimental studies of skin wound healing process by first intention in streptozotocin-induced diabetes mellitus rats].

Various parameters were used in observing the process of wound healing in rats with streptozotocin-induced diabetes (STZ diabetes). Sections stained according to the Hematoxylin-Eosin, Van-Gieson, and Azan methods were used in observing histological changes. At the same time, wound strength during the healing was measured as a parameter for evaluating the healing process. In addition, changes in leukocytes, plasma fibrinogen, activated factor XIII (aXIII), collagen content of the incised wound, and metabolic changes were determined. Results 1. Histological studies showed that, in STZ diabetes, the inflammatory response was minimal and occurred later than in normal cases. In the incised wound, cellular infiltration of polymorpho-nuclear leukocytes and fibrin nets accumulated poorly. The fibrin net was coarse and fragile. Furthermore, epithelialization of the wound was late: it did not occur until 5 days after the operation. In cases of STZ diabetes, patterns of hyperplasia and fibroblast arrangements were abnormal. Collagen regeneration and proliferation processes were remarkably retarded. 2. In normal, wound strength increased from the 5 postoperative day. After 10 days had passed, it increased remarkably until, after 30 days, it had returned to the preoperative level. In STZ diabetes, however, no increase in wound strength occurred for the first 14 days after the operation. There after strength increased slowly; but, 40 days after the operation, 80% of the preoperative level still had not been reached. 3. Changes in leukocytes were much later occurring in STZ diabetes than in normal. Recovery took longer than in normal. 4. In STZ diabetes, increases in plasma fibrinogen and decreases of the aXIII factor were slower than in normal. The a XIII factor decreased remarkably, and recovery was slow. 5. In terms of collagen content in the wound incision, in STZ diabetes, tropocollagen increase occurred later than in normal. But, from the 5 to the 14 postoperative days, its level was higher than that in normal. Maturation-process collagen and mature collagen increased still more slowly. In normal, mature collagen had reached preoperative level 20 days after the operation, in STZ diabetes, 80% of preoperative level still had not been reached 30 days after the operation. 6. These studies showed that the following factors hinder wound healing in cases of diabetes mellitus: minimal inflammatory response, incomplete formation of the fibrin nets, retardation of epithelialization, retarded action of plasma fibrinogen and the a XIII factor, reduced fibroblast activity, and slow increase in collagen content.