Abstract
Abstract: :
Purpose: The mucocutaneous junction (MCJ) is a transitional zone located between the epidermis of the eyelid skin and the palpebral conjunctival epithelium, and has unique characteristics that distinguish it from the surrounding epithelium. The purpose of the study is to determine the MCJ epithelial cell migration course on various planes. This knowledge will provide us with an anatomical basis for locating the stem cells of the palpebral conjunctival epithelium tissue, and will be another step in understanding and characterizing the MCJ epithelium. Methods: The study was performed using the autoradiographic method. Twenty–seven rats were injected intraperitoneally with a single dose of [3H]–thymidine. Three rats were killed one hour after injection, and three rats after 3, 6, 9, 12, 15, 18, 21, and 28 days. Eyelid were removed, fixed in formalin, embedded in paraffin, cut into 5µ–thick sections, and prepared for autoradiography. The MCJ epithelium, extending from the end of the palpebral conjunctiva to the orifice of the eyelashes at the epidermis, was scanned. The end of the palpebral conjunctiva served as point of origin. The x and y coordinates of each nucleus possessing a single grain or more, and the number of grains in each nucleus, were recorded. The statistical analysis included linear regression and analysis of variance. Results: The migration course of cells in the MCJ epithelium is from the end of the palpebral conjunctiva to the epidermis in a direction opposite to that of the migration course of the palpebral conjunctival epithelial cells. Cells migrate along the x axis at an average rate of 2.4 ± 0.7 microns/day (p < 0.0007), and along the y axis at an average rate of 3.5 ± 0.7 microns/day (p < 0.0001). Cell cycle time was found to be 6.93 days. Conclusions: This study demonstrates for the first time cells in the MCJ epithelium migrate along an independent tissue axis. The MCJ epithelial cells migrate from the point where histologically the palpebral conjunctival epithelium ends, toward the epidermis. The border between the MCJ epithelium and the palpebral conjunctival epithelium was found to be the point of origin of two opposite tissue axes: the MCJ axis and the palpebral conjunctival axis. Thus, this border contains stem cells of both these tissues.
Keywords: anatomy • conjunctiva • eyelid