CO-expression of BCL-2 and CD-44s in basal layers of normal limbus and conjunctiva

Purpose. The bcl-2 oncogene is one of the regulatory oncogenes known to inhibit programmed cell death (apoptosis). Expression of bcl-2 is limited to self-renewing tissues such as bone marrow and skin. CD44s is the receptor for hyaluronic acid and crucial for modulating epithelial adhesion and migration. Engagement of CD44 receptors of T-lymphocytes can inhibit apoptosis. To study the regulation of apoptosis of ocular surface epithelia, we investigated herein the expressions of bcl-2 and CD44s in normal human and rabbit ocular surface epithelia. Mfttfrods. Human ocular surface epithelia were obtained from normal cadaver eyes. RT-PCR and Southern and Northern hybridizations were performed to study bcl-2 gene expression using primers (MBR 1 & 3) and an oligoprobe (MBR 2) specific for the normal allele of bcl-2 gene. Confocal microscopy and dual-labeling immunohistochemistry were performed on normal tissue sections with monoclonal anti-bcl-2 and anti-CD44s antibodies. Results. By RT-PCR and Northern hybridization, m-RNA of bcl-2 was detected in all three epithelia with a preferential expression in the conjunctival epithelium. The specificity of RT-PCR products of bcl-2 was confirmed by Southern blots. By confocal microscopy, bcl-2 and CD44s were co-expressed in the basal layers of conjunctival and limbal epithelia. Sporadic staining of bcl-2 was also noted in the conjunctival goblet cells. In contrast, no evident bcl-2 or CD44s was detected in corneal basal epithelium. In the primary rabbit epithelial cultures, bcl-2 was sporadically expressed in corneal epithelia but diffusely expressed in conjunctival epithelia and presumed goblet cell aggregates. Conclusions. Preferential coexpression of bcl-2 and CD44s in the basal layers of conjunctival and limbal epithelia implicates their potential roles as ocular surface epithelial stem cells. Paucity of bcl-2 expression in normal corneas suggests that comeal epithelium may be more susceptible to apoptosis than limbal and conjunctival epithelia. . .