Accelerated wound healing in mice with a disruption of the thrombospondin 2 gene

Mice that lack the extracellular matrix protein thrombospondin 2 have, among several abnormalities, an increase in vascular density, abnormal collagen fibrils, and dermal fibroblasts that are defective in adhesion. These findings suggested that responses involving these processes, such as wound healing, might be altered, To investigate the healing process, excisional wounds were made with the aid of a biopsy punch. Such wounds, observed over a 14 d period, appeared to heal at an accelerated rate and with less scarring in thrombospondin 2-null mice. Histologic analysis of thrombospondin 2-null wound sites revealed the presence of an irregularly organized and highly vascularized granulation tissue. In addition, thrombospondin 2-null wounds retained a higher total cellular content, than control wounds. No differences in wound re-epithelization rates were observed, but thrombospondin 2-null epithelia formed rete pegs and were thicker than control epithelia. By immunohistochemistry, we detected elevated levels and an irregular deposition pattern for fibronectin in thrombospondin 2-null wounds, observations that correlated with the abnormal collagen organization in the granulation tissue. Immunostaining for thrombospondin 2 in control wounds showed that the protein is present in both early and late wounds, in a scattered cell-associated pattern or widely distributed cell- and matrix-associated pattern, respectively. Our results suggest that thrombospondin 2 plays a crucial part in the organization and vascularization of the granulation tissue during healing, possibly by modulating fibroblast-matrix interactions in early wounds and regulating the extent of angiogenesis in late wounds.