Extracellular matrices in the developing avian eye: type V collagen in corneal and noncorneal tissues

We have used immunofluorescence histochemistry to examine the temporal and spatial deposition of type V collagen in the extracellular matrices of the developing chick cornea and other selected ocular structures. Tissue sections from animals ranging in age from 4-day-old embryos to 1-day post-hatching were examined by indirect immunofluorescence employing monoclonal antibodies specific for conformational dependent sites in this molecule. In eyes from embryos younger than 6 days of development, no type V staining could be detected. Thus, the epithelially derived primary corneal stroma, which is already well formed at this time, contains little if any of this molecule. Its appearance was concomitant with the physical swelling of the primary stroma and invasion of pericorneal mesenchymal cells. Staining was initially localized in the anterior cornea; subsequently, all corneal matrices showed intense reactions, including the stroma proper and Bowman's and Descemet's membranes. In adjacent noncorneal tissues, the appearance of type V collagen occurred later in development. In some of these, such as in the ciliary body, the pattern of acquisition involved initial deposition at an epithelial-mesenchymal interface with subsequent progression of fibrous strands out into the surrounding mesenchymal tissue. Eventually, all ocular structures with a dense connective tissue component showed staining, but the intensity was appreciably less than that within the cornea. We have previously reported that in all mature tissues except Bowman's membrane, type V collagen is present in an "antigenically masked" form, and that unmasking can be achieved by pretreatment of the tissue sections with dilute acetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)