Abstract
Abstract: :
Purpose: To study the contribution of limbal stem cells to the renewal of the ocular surface epitheliums. Introduction: The limbus contains epithelial stem cells that supposedly contribute to the renewal of the corneal epithelium. Similarly, the fornix is though to contain stem cells that contribute to the renewal of the conjunctiva . To further explore the role of these regions to the renewal of the ocular surface, we have developed a mircosurgery approach using labeled limbal and fornical regions. Methods: Parts of the limbus and of the fornix were amputated from athymic mice and replaced by equivalent limbal and fornical regions obtained from Rosa 26 mice that constitutively expressed a lacZ gene. The eyes were harvested at different periods of time and stained for b-galactosidase to evaluate the contribution of the labeled cells to the renewal of the ocular surface. Results: Surprisingly, we have never observed cells migrating from the limbus to the central cornea when the corneal epithelium was intact (n=34), even when the grafts were left in place up to six months. However, cells migrated very efficiently towards the central cornea when the corneal epithelium was wounded. Similarly, cells migrated onto the bulbar conjunctiva to a limited extend in absence of fornical wound. However limbal cells migrated efficiently onto the bulbar conjunctiva in direction of the fornix after a fornical wound. They even reached the fornix in some cases. Epithelial cells originating from the limbal grafts expressed either a conjunctival or corneal phenotype depending on the direction of migration. Furthermore, we have not observed cells migrating from the transplanted labeled fornix. Conclusions: We conclude from these experiments that the limbus contribute little if any to the renewal of the cornea under normal circumstances. However its contribution is crucial to repair an ocular surface wound whatever the wound is corneal or conjunctival.
Keywords: 372 cornea: epithelium • 365 conjunctiva • 631 wound healing