Taka Nagasaki, Ph.D.
Department of Ophthalmology, Columbia Univeristy
Our research interests are in the physiology and cell biology of the anterior segment of the eye. Currently we are pursuing two projects that concern wound healing of the cornea and the conjunctiva: 1. characterization of cell movement with in vivo time-lapse microscopy (e.g., Nagasaki and Zhao, 2003, IOVS 44:558), 2. physiological and biochemical analysis of tear factors that are cytotoxic to the corneal stromal cells (cf., Zhao et al., 2001, IOVS 42:1743).
Following is a brief account of our recent progress.
A novel technique of in vivo microscopy to study corneal wound healing.
We have established a novel technique for observing corneal cells in a living mouse under a fluorescence microscope. The technique is constantly improved for better imaging and less photo damage to the cells. With this technique we have observed movements of corneal epithelial cells, conjunctival epithelial cells, corneal stromal cells, leukocytes that invade the stroma after an injury, and also growth of capillary blood vessels in the corneal stroma after cauterization and their subsequent degeneration.
Cell movement in the corneal and conjunctival epithelium of a living mouse.
Corneal epithelium of adult GFP mice exhibits a pattern of GFP expression that is suitable for tracking cell movement. Epithelial GFP could be imaged and followed by in vivo time-lapse microscopy with a living mouse, which demonstrated constant centripetal movement of epithelial cells at the basal or supra-basal layers at an average rate of 26 Ám/day.
Using essentially the same technique we began to study movement of conjunctival epithelial cells with a living mouse.
Tear components that are cytotoxic to the corneal stromal cells.
We have previously demonstrated that the mouse tears contain factors that are cytotoxic to the corneal stromal cells but not to the corneal epithelial cells. Recently, we identified the major source of the cytotoxic factors to be the lacrimal glands, instead of the surface epithelium of the cornea and the conjunctiva. Biochemical characterization of the cytotoxic factors is under way.
A physical impact of mechanical epithelial scraping on underlying stromal cells
We have found that the mechanical scraping of corneal epithelium, a routine clinical procedure, triggers gross deformation of nuclei in the underlying keratocytes. The nuclear deformation is accompanied by destruction of cellular structural components, and these cells degenerate within several hours after the injury.
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