ENTACTIN NIDOGEN - SYNTHESIS BY BOVINE CORNEAL ENDOTHELIAL-CELLS AND DISTRIBUTION IN THE HUMAN CORNEA/

Purpose. The purposes of this study were to determine whether entactin /nidogen (E/N) is synthesized and secreted by corneal endothelial cell s and to characterize the distribution of E/N in the human cornea. Met hods. Cultured bovine corneal endothelial cells were metabolically lab eled with [S-35]methionine. Newly synthesized E/N was detected in cell lysates and culture medium by immunoprecipitation, using monoclonal a nti-E/N antibodies, polyacrylamide gel electrophoresis, and autoradiog raphy. The presence of E/N in the subendothelial extracellular matrix was demonstrated by Western blot analysis of solubilized extracellular matrix proteins. The distribution of E/N in normal human corneas was studied by indirect immunofluorescent staining of frozen sections, usi ng monospecific anti-E/N antibodies. Results. E/N was detected in the basement membrane (BM)-like extracellular matrix deposited by corneal endothelial cells, as well as in cell lysates and culture medium. Immu nofluorescence studies revealed the presence of E/N in both the epithe lial and endothelial BM and to a much lower extent in the stroma. E/N was detected throughout the thickness of the epithelial BM, but its st aining decreased in intensity toward the central part of the cornea. I n the endothelial BM (Descemet's membrane), E/N fluorescence was limit ed to its most posterior portion, produced postnatally. Conclusions. C orneal endothelial cells synthesize and secrete E/N. E/N was found in both the epithelial and endothelial basement membranes but was primari ly localized to the posterior portion of Descemet's membrane and the p eriphery of the epithelial BM. The authors suggest that E/N may be imp ortant in healing processes of corneal injuries and in the pathogenesi s of diseases involving the postnatal region of Descemet's membrane.