PROTEIN GENE-PRODUCT 9.5 IS EXPRESSED BY FIBROBLASTS IN HUMAN CUTANEOUS WOUNDS

In a study initially designed to evaluate reinnervation of human cutan eous wounds using an antibody to the neuroneal marker protein gene pro duct (PGP) 9.5, we observed marked immunostaining of cells with morpho logic features of fibroblasts in the wounds. PGP 9.5 has recently been shown to be an important enzyme in the highly conserved ubiquitin sys tem of proteolysis, Because the ubiquitin system is known to play an i mportant role in regulating the cell cycle, the presence of PGP 9.5 in cells at a wound site was of considerable interest. Our objectives we re to clarify the time frame for the appearance of PGP 9.5 and ubiquit in in wounds, to verify that PGP 9.5 is produced by wound fibroblasts, and to evaluate a potential role for these proteins in the tissue rep air process. Standard incisional human wounds were stained with antibo dies specific for PGP 9.5 and ubiquitin, At 7 d, stellate cells with m orphologic features of fibroblasts stained for PGP 9.5, whereas earlie r wounds were generally negative. In 14 and 21 d incised wounds and in chronic granulation tissue from nonhealing ulcers there was strong ce llular staining for PGP 9.5 and for ubiquitin. These stellate cells al so showed expression of mRNA for PGP 9.5 by reverse transcriptase-poly merase chain reaction irt situ hybridization. PGP 9.5 was detected in cultured fibroblasts both by reverse transcriptase-polymerase chain re action and by northern blot analysis. Confocal microscopy showed coloc alization of antibodies to PGP 9.5 and prolyl-4-hydroxylase (a fibrobl ast marker) as well as colocalization of PGP 9.5 and the platelet deri ved growth factor beta receptor. We conclude that ubiquitin and PGP 9. 5 were expressed by fibroblasts during the granulation tissue and remo deling phases wound healing. The mRNA for PGP 9.5 was demonstrated in stellate cells in chronic wounds and in fibroblasts in culture, The ap pearance of these degradative proteins in later wounds suggests a down regulation function in the wound healing response,