Role of apoptosis in separation of eyelid in newborn rat with method of hemathoxylin and eosin

Abstract

Background: Apoptosis or programmed cell death is a process in which the unwanted cells die after a coordinated and planned activities of an accurate collection of genes. Apoptosis are considered in embryo development, cancer pathogenesis and humoral immune responses. Considering the role of apoptosis in fetal development, this study was done to investigate its role in separating eyelids in neonatal rats. Methods: For this purpose the unopened eyelids of 6-16 days old Wister newborn rats were removed after anesthesia and fixed in 10% formolin. After preparation and paraffin embedding, 5 micron thick sections stained with hemathoxylin and eosin, and studied with light microscope. Finding: Microscopic assessment of opening place of eyelids showed that the eyelid groove formation starts with external and internal surface troughs. After reaching the troughs together, the eyelids are separated.The main changes that occurred during eyelid formation are appearance of vesicular cells with morphologic characteristics of apoptotic cells includes: nuclear pyknosis, cell shrinkage, deeply eosinophilic cytoplasm surrounded by, and clear halo. These cells were abundant form 6th to 16th day. After 12th day these cells were seen among the cells of spinosum layer. The other change that we could see during eyelid formation was development of keratinized epidermis of external surface and nonke-ratinized stratified squamous epithelium of the internal surface of eyelid. Conclusion: Role of apoptosis in developing embryo, before and after implantation, is well known. Presence of cells with characteristics of apoptotic cells in the site of eyelid development in rat Showed the role of apoptosis in eyelid formation. Easy to access of apoptotic cells in eyelid formation in newborn rats can serve rat as a very suitable model for evaluating the inhibitors and inductors of apoptosis.