Expression and localization of angiogenic inhibitory factor, chondromodulin-I, in adult rat eye

PURPOSE. TO determine the role in the eye of chondromodulin (ChM)-I, which has been identified in cartilage as an angiogenic inhibitor, the expression and localization and a possible function of ChM-I were investigated. METHODS. Expression and localization of ChM-I in rat eyes were examined by RNase protection assay and in situ hybridization and by immunostaining, usi ng an antibody against a synthetic peptide. The effect of recombinant ChM-I on tube morphogenesis of retinal endothelial cells was examined in culture . RESULTS. The rat ChM-I gene was determined to encode the open reading frame of 334 amino acid residues, and ChM-I mRNA was exclusively expressed in ca rtilage, eye, and cerebellum in rats. ChM-I mRNA expression was evident in the iris- ciliary body, retina, and scleral compartments, but not in other compartments of tile eye. In situ hybridization revealed mRNA expression in the ganglion cells, inner nuclear layer cells, and pigment epithelium in t he retina and in the nonpigment epithelium of the ciliary body. Immunoreact ive ChM-I was present in these cells and also in the vitreous body. Western blot analysis detected an similar to 25-kDa band of ChM-I presumed as a se cretory form in the aqueous humor and vitreous body and an similar to 37-kD a band as a precursor form in the retina. Recombinant human ChM-I inhibited tube morphogenesis of human retinal endothelial cells in vitro. CONCLUSIONS. These observations indicate a potential role fbr ChM-I in inhi bition of angiogenesis in the rat eye.