title: Stem cells of the corneal epithelium lack connexins and metabolite transfer capacity.
abstract: The stem cells of the corneal epithelial lineage are confined to the basal cell layer of the limbus, a vascularized outer corneal rim. These slow cycling cells of great proliferative potential maintain the corneal epithelial mass. Since cell-cell communication plays an important role in development and differentiation, we conducted a comparative examination of the expression of two corneal connexins, C x 43 and C x 50, and the tracer transfer capacity of the limbal and corneal epithelia using the scrape loading technique. C x 43 is abundantly expressed in the basal cell layer of the epithelium covering the cornea, but is essentially absent from the mouse, human, neonatal rabbit, and chicken limbal epithelium. In the adult rabbit the limbal epithelium displays an overall weak C x 43 immunoreactivity, but C x 43-free isolated basal cells can be distinguished. C x 50 is expressed throughout the corneal epithelium of the three mammalian corneas, but is not detectable in the limbus. Scrape loading experiments in the rabbit yielded results which were consistent with the immunohistological findings; limbal epithelium lacked tracer (lucifer yellow) transfer capacity, strongly suggesting the absence of functional gap junctions. Altogether, our results demonstrate the incompetence of stem cells for gap junction-mediated cell-to-cell communication. This property may reflect the need of these unique cells to maintain a distinct intracellular environment.
authors.affiliation: Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY 10029-6574, USA.
authors.forename: M
authors.initials: M
authors.lastname: Matic
authors.forename: I N
authors.initials: IN
authors.lastname: Petrov
authors.forename: S
authors.initials: S
authors.lastname: Chen
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: S D
authors.initials: SD
authors.lastname: Dimitrijevich
authors.forename: J M
authors.initials: JM
authors.lastname: Wolosin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001692:Biological Transport; D002450:Cell Communication / Q000502:physiology; D002645:Chickens; D018031:Connexin 43 / Q000276:immunology / Q000378:metabolism; D017630:Connexins / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism* / Q000648:ultrastructure; D004848:Epithelium / Q000378:metabolism; D005136:Eye Proteins / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism; D006801:Humans; D007477:Ions; D016850:Limbus Corneae / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D011817:Rabbits; D013234:Stem Cells / Q000378:metabolism*; D014714:Vertebrates / Q000378:metabolism; D000099264:Connexin 50
chemical_list: D018031:Connexin 43; D017630:Connexins; D005136:Eye Proteins; D007477:Ions; D000099264:Connexin 50