Ocular distribution of keratan sulfates during pre- and postnatal development in rabbits

Twenty-six monoclonal antibodies (MAbs) developed against rabbit corneal proteokeratan sulfate (PKS), were used to evaluate immunohistochemically the ocular distribution of PKS during prenatal and early postnatal development in rabbits. These MAbs were directed against epitopes located in the keratan sulfate (KS) chains of the proteoglycan (SundarRaj et al., 1985). Staining of cryostat sections of the eyes was carried out using an indirect peroxidase-conjugated technique. Only one of the MAbs reacted with the presumptive corneal region at day 13 or 16 of fetal development. By day 20, more MAbs reacted with the corneal stroma. There were distinct differences, however, in the distribution of the epitopes recognized by the various MAbs. A few of them stained only the posterior region of the cornea, whereas others showed a decreasing staining gradient from the posterior to the anterior region. By day 24, all of the MAbs reacted with the corneal stroma, but some reacted also with the limbal region and with the conjunctival stromal matrix. One MAb also reacted with the conjunctival epithelial layer, but only at this stage of development. Conjunctival staining was more intense at day 28 of fetal development and at day 2 postnatally. KS was not detectable in the conjunctiva of adult rabbits with any of the MABs. These results suggest that although KS synthesis starts at very early stages of fetal development, there are progressive changes in its antigenic structure in specific regions of the cornea and conjunctiva during corneal development.