Purpose: To elucidate the role of perlecan (Hspg2), a large multidomain heparan sulfate proteoglycan expressed in the basement membrane, in the structure of the corneal epithelium.
Methods: A previously developed perlecan-deficient (Hspg2⁻/⁻-Tg) mouse model was used. Histologic analysis of their corneas was performed by light and transmission electron microscopy. The localization of perlecan in the corneas of wild-type (WT) mice and Hspg2⁻/⁻-Tg mice was examined by immunohistochemistry. The effects of perlecan deficiency on corneal epithelial structure was analyzed with respect to the expression of corneal epithelial proliferation and differentiation markers, such as Ki67, cytokeratin12 (K12), connexin43 (Cx43), Notch1, and Pax6 by immunohistochemistry and real-time polymerase chain reaction (PCR).
Results: The Hspg2⁻/⁻-Tg mice had microphthalmos and a thinner corneal epithelium compared with that of the WT mice. Perlecan was localized in the corneal epithelial basement membrane in the WT mice, but not in the Hspg2⁻/⁻-Tg mice. The Hspg2⁻/⁻-Tg corneal epithelium exhibited thinner wing cell layers and a decreased number of Ki67-positive cells, but no dead cells, compared with the WT corneal epithelium. Immunohistochemistry and real-time PCR analysis revealed a significantly decreased expression of corneal epithelial differentiation markers such as K12, Cx43, Notch1, and Pax6 in Hspg2⁻/⁻-Tg mice, compared with those of the WT mice.
Conclusions: The findings of this study highlight a strong correlation between the presence of perlecan in the basement membrane and the structure of corneal epithelium and that the perlecan-deficient mutation impairs corneal epithelial structure.