Abstract
Abstract: :
Purpose:It has been suggested that family of MMPs play a casual role in the process of corneal development in vivo; however their roles in corneal development have not been elucidated. The goal of this study was to investigate whether expression of MMPs/TIMP and cell–matrix associated proteins was involved in the corneal swelling, stromal cell invasion, and maturation of cornea. Methods:Corneas were isolated from developing day 5, 7, 10, 14, 18 embryos, and 2 days old chick. Developmental expressions of gelatinase A, stromelysin, collagenase–3, TIMP–1, CD44v, and ADAMs were analyzed by western blot. Immunohistochemistry was also performed to detect localization of their expression. Results:Collagenase–3 is strongly expressed at day 5 developing cornea, and its expression is decreased gradually up to day 10. Interestingly, the highest level of stromelysin is also expressed at day 5 developing cornea. It is well known that type IX collagen can be degraded only by collagenase–3 and stromelysin–1. Therefore, our results indicated that both highly expressed levels of collagenase–3 and stromelysin–1 at day 5 and 7 developing cornea may play an important role for swelling of corneal stroma, invasion and migration of mesenchymal cells into the primary stroma. CD44v, a hyaluronate receptor, is implicated in cell–cell and cell–matrix interactions. We show that CD44v isoforms are strongly expressed primarily up to 10 days of developing cornea. We also show that two forms of ADAMs (82–KDa and 40–KDa) are temporally and differentially expressed during development. Interestingly, 82–KDa is detected only in day 5, 7, and 10 developing cornea, and its expression level is highest at day 5. Although 40–KDa is detectable from day 5 to day 18 developing cornea, highest level is detected between day 10 and 14. However, both forms are not detectable in hatched cornea. As expected, TIMP–1 expression is not detected up to 14 days of developing cornea. These data indicate that all the expressed MMPs in the early time points of corneal development between day 5 and 10 may exert their full enzymatic activity for removal of the type IX collagen as well as formation of mature stroma. Conclusions:Our results suggest that differentially expressed MMPs/TIMP as well as CD44 and ADAM act in concert to effect the invasion and migration of neural crest–derived mesenchymal cell into the primary and secondary stroma as well as remodeling of cornea.
Keywords: cornea: basic science • cornea: epithelium • cornea: stroma and keratocytes