Abnormalities of granulation tissue and collagen formation in experimental diabetes, uraemia and malnutrition.

The formation of granulation tissue and collagen was studied in rats made diabetic with streptozotocin. Granulation tissue was harvested from the inside of steelmesh cylinders implanted in the back of diabetic and control animals. Four weeks after implantation there was a reduction in the quantity of granulation tissue and its collagen content in diabetic animals compared to controls. Rats with renal failure or malnutrition but no diabetes also formed less granulation tissue but in these animals the content of collagen in the granulation tissue was normal. These results suggest that the decrease of collagen, but not granulation tissue, in diabetes is a relatively specific phenomenon which was not due to the toxic effects of streptozotocin as the changes were prevented by insulin treatment. The hydroxyproline/proline ratio of diabetic collagen was found to be normal, excluding defective hydroxylation of proline as an important factor in the reduction of collagen in diabetes. Treatment with an aldose reductase inhibitor did not prevent the abnormalities of granulation tissue and collagen in diabetes, making it unlikely that increased activity of this enzyme played an important pathogenetic role. The observed reduction of granulation tissue mass and collagen content in diabetes may be important factors in the impairment of wound healing in diabetes.