DIFFERENTIAL EXPRESSION OF SPARC AND THROMBOSPONDIN-1 IN WOUND REPAIR- IMMUNOLOCALIZATION AND IN-SITU HYBRIDIZATION

SPARC and thrombospondin 1 (TSP-1) are secreted glycoproteins expresse d by similar types of cells in culture and in tissues. To compare thes e two proteins in vivo, we analyzed the differential expression of SPA RC and TSP-1 during wound repair. Full-thickness incision wounds were made in rats and biopsied at 12 hr-14 days. Antibodies against SPARC r evealed an increased proportion of immunoreactive fibroblastic cells a t the wound edge at 3 days with maximal numbers at 7 days. In situ hyb ridization for SPARC produced results consistent with those of immunoh istochemistry. With combined immunohistochemistry and in situ hybridiz ation, some of the macrophages at the wound edge expressed SPARC mRNA. In contrast, immunoreactivity for TSP-1 was extracellular; expression at the wound edge was noted at 12 hr and was maximal at 1-2 days. TSP -1 mRNA was found in the thrombus, but not at the wound edge. In concl usion, SPARC and TSP-1 have contrasting roles during wound healing. SP ARC expression from the middle through late stages of repair was consi stent with its previously proposed functions in remodeling; in contras t, the transient expression of TSP-1 early in repair might facilitate the action of other proteins in recruitment and/or proliferation of ce lls in the healing wound.