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J. D. Zieske, E. Friedenberg, A. E. K. Hutcheon, M. P. Hatton; Restoration of the Eyelid Mucocutaneous Junction. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4785.
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The eyelid mucocutaneous junction (MCJ) is a prime example of an intersection between two types of epithelium, in this case conjunctival and epidermal. A basic question of biology is how these junctions or "lines in the sand" are maintained. In this study, we surgically removed the MCJ in rat eyelids to examine the restoration of this junction.
The MCJ was surgically removed from the upper eyelid of the right eye from 6 Sprague-Dawley rats per time point. This surgery removed the epithelium, the basement membrane and a portion of the underlying matrix. The eyelid was allowed to heal for 4, 8, 16, 24, 48, 72 hours, 4, 5, 6 and 7 days. At the allotted time, the rats were euthanized, and the eyes plus eyelids were enucleated and processed for immunofluorescence. Six-micron thick sections were cut, and the primary antibodies against keratin 4 (K4) and keratin 10 (K10) were observed. Negative controls where the primary antibody was omitted were run with each experiment.
In unwounded controls, K4 was found in the conjunctival epithelium with the staining stopping at the MCJ. K10, on the other hand, was found in the cutaneous epithelium and stopped at the MCJ. Interestingly, K4 and K10 did not co-localize, leaving a very definite partition between the two types of epithelium. Also of interest, the basal cells at the MCJ were not positive for either K4 or K10. After wounding, the K4 and K10 staining in the MCJ disappeared and then reappeared by 4 days; however, the partition that separated the two epithelial types was blurred. By 7 days, the partition appeared to reform, but the epithelium in the wound area was thicker than in unwounded.
The MCJ appears to be on the conjunctival side of the meibomian gland orifice and represents an abrupt partition between epidermal (K10) and conjunctival (K4) epithelium. The MCJ appears to reform by 7 days after surgery, with the conjunctiva appearing to mount the more vigorous healing response.
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