Pilot Studies On The Localization Of Conjunctival Epithelial Stem Cells In Fetuses Older Than 28 Weeks

ObjectiveThe ocular surface epithelium is made up of corneal and conjunctival epi-thelia. The integrality of their structure and function is vital to the maintenance of a stable state of the ocular surface environment. Normally, the corneal and conjunctival epithelia are continuously self - renewed and self - repaired. Such process of self - renewal depends on the ocular surface stem cells. Recently we have learnt a lot about the corneal epithelial stem cells both in the basic research and the clinical application, yet the conjunctival epithelial stem cells biology has been much less investigated. The Localization of the conjunctival epithelial stem cells is still not clear. Different from previous studies in animals, here we reported firstly our research of the fetal conjunctival epithelial stem cells. The expression of PCNA, P63 , AE5 , MUC5A/C and the keratin K7, K19 at the conjunctival of fetuses elder than 28 weeks was studied using immunohistochemistry, through which we can judge the general localization of conjunctival epithelial stem cells and the result of which would be helpful to further locate them accurately.Methods16 fetal eyes were obtained from 8 fetuses ( older than 28 weeks) at abortion with the permission of hospital and pregnant women. Of the 8 fetuses, 5 were males and 3 were females. After the eyeballs including the eyelids wereseparated from the bodies, the posterior sclera, the skin and subcutaneous tissue were removed but the lid rim left. Then the eyeball was sagittally scissored into strips. In each strip, the entire conjunctiva extending from limbus up to the palpebral muco - cutaneous junction (referred here as palpebral margin) was evaluated. The strips were fixed in 4% polyformaldehyde , made into paraffin sections, and stained with haematoxylin and eosin. We observed the location, morphology and structure of the palpebral muco - cutaneous junction, the palpebral, the fornical and the bulbar conjunctiva, as well as the limbus . We also observed the expression of PCNA , P63 , MUC5A/C, K7, K19 and AE5 , through light microscopy after SP immunohistochemistry staining.ResultsThe expression of PCNA and P63 were relatively evident at the palpebral muco — cutaneous junction and the limbal region, none of which expressed evidently at the bulbar and fornical conjunctiva. Besides, P63 was also expressed at the palpebral conjunctiva while PCNA did not. MUC5A/C was only expressed evidently at the fornical conjunctiva, while the keratin K7 and K19 both expressed evidently at palpebral conjunctiva, the bulbar conjunctiva and the fornical area, although they did not show evident expression at the muco - cutaneous junction and the limbus. AE5 was not expressed at the whole conjunctiva.ConclusionCells with high capability of proliferation were found in the area of muco -cutaneous junction and limbus of fetuses elder than 28 weeks, which suggest that conjunctival epithelial stem cells may exist there.