Acute wound repair in an aged animal: a model for accelerated aging of the microvasculature?

This study of wound repair in the aged rat is based on increased carbohydrate content of various proteins which occurs with aging and is readily seen in the microvasculature (MV). We have used the periodic acid-Schiff (PAS) reaction to identify histochemically the carbohydrate moiety of the glycoproteins found in these blood vessels. In the young rat, as in other young vertebrates, elements of the MV are PAS negative and become increasingly PAS+ beyond the half life span. During acute wound repair in an old animal, the new capillaries and venules are PAS- 2 weeks after injury, moderately PAS+ at 4 weeks, and intensely PAS+ at 8 weeks. Arterioles are present and PAS+ at 6 weeks, and intensively positive at 8 weeks, comparable to vessels remote from the wound site. The MV in wound repair in a young animal remains PAS- throughout healing. Rapid aging of the microvasculature in wound repair in an old animal reproduces histochemically the aging which occurs progressively during the prior 24 months. These histochemical changes may result from successive enzymatic and nonenzymatic glycosylation of the various basement membrane proteins in the microvasculature in both normal aging and wound repair in the aged animal. The latter may serve as a model for study of accelerated aging.