Salt and Water Transport in the Corneal Endothelium

I have a long-standing interest in salt and water balance and its regulation from the molecular level to that of the whole animal. Currently, I have a project in my lab funded by a "Fight for Sight" Grant to investigate salt and water transport as well as agonist/cytokine control of transport function, and growth and differentiation in the corneal endothelium.

The cornea is a nonvascularized, normally transparent tissue, that covers the aqueous humor filled anterior chamber of the eye. The cornea is composed of an outer epithelial layer, a middle layer of mostly non-cellular connective tissue (stroma), and an inner layer (endothelium), that faces the aqueous humor. The corneal endothelium is a specialized epithelial monolayer of neural crest-derived cells, that through its ion transport activity, regulates the degree of corneal stromal hydration and consequently, corneal clarity. Transparency depends on an intact endothelium and an endothelial membrane ion pump. The ion pump compensates for passive stromal water uptake by coupling water outflow to transendothelial ion efflux from the stroma to the aqueous humor, thereby maintaining stromal hydration state. Under pathological conditions, water balance may be disrupted resulting in corneal swelling, opacity, and if not reversed, blindness. Corneal transplantation is the only available method for restoring sight when the endothelium is sufficiently compromised. Elucidating the basic cell biology of corneal endothelial cells and the mechanisms that stimulate growth, differentiation and salt and water transport is the first step in designing therapies to reduce the necessity for transplantation (45,000 in the U.S. in 1998).

Although the details remain to be defined, it is clear that the underlying driving force for transendothelial ion-linked water transport ultimately resides in the ouabain-sensitive sodium (Na) pump (Na+/K+-ATPase) situated in the basolateral cell membrane of corneal endothelial cells. The critical role of the Na pump in stromal dehydration is demonstrated by ouabain induced corneal swelling, a phenomenon that occurs without compromise of endothelial barrier function as judged by unaltered permeability to nonelectrolytes and fluorescent dyes and by the maintenance of normal junctional architecture. Thus, the corneal endothelium is a tissue critical to vision, and the Na pump is, in turn, crucial to carrying out the primary function of corneal endothelial cells, i.e.,salt and water transport.

Recent experiments focus on the study of the Na pump and factors that alter pump number and function.

The actin cytoskeleton in a confluent culture of bovine
corneal endothelium is demonstrated by rhodamine-conjugated phalloidin.




Recent Publications

 

 

Crawford, K.M., D.K. MacCallum, and S.A. Ernst. 1992. Histamine-H1-receptor mediated Ca2+ signaling in cultured bovine corneal endothelial cells. Invest. Ophthalmol. Vis. Sci. 33: 3041-3049.
Crawford, K.M., D.K. MacCallum, and S.A. Ernst. 1993. Agonist -induced Ca2+ mobilization in cultured bovine and human corneal endothelial cells. Curr. Eye Res. 12: 303-311.
Crawford, K.M., S.A. Ernst, R.F. Meyer, and D.K. MacCallum. 1995. Na+/K+ -ATPase pump sites in cultured bovine corneal endothelium of varying cell density at confluence. Invest. Ophthalmol. Vis. Sci. 36: 1317-1326.
Crawford, K.M., D.K. MacCallum, and S.A. Ernst. 2001. Autocrine regulation of bovine corneal endothelial cell proliferation by endothelin-1. Current Eye Research. (in press).
MacCallum, D.K., K.M. Crawford, S.A. Ernst, and R.F. Meyer. 2001. Reversible cytochalasin- induced shape and junctional architectural change in confluent bovine corneal endothelial cell cultures. (in preparation).
Crawford, K.M. 2001.  Up-regulation of sodium (Na) pump surface expression in bovine corneal endothelial cells. Cornea. (in preparation).
 
 

Abstracts


Crawford, K.M., V.J. Nath, D.K. MacCallum, and S.A. Ernst. 1994. Receptor binding, signal transduction and immunofluorescent localization of endothelin-1 in cultured bovine corneal endothelial cells. Invest. Ophthalmol. Vis. Res. 35: 1602.
MacCallum, D.K., K.M. Crawford, S.A. Ernst, and R.F. Meyer. 1994. Reversible cytochalasin- induced shape and junctional architectural change in confluent bovine corneal endothelial cell cultures. Mol. Biol. Cell. 5:83a.
Crawford, K.M., D.K. MacCallum, and S.A. Ernst. 1995. Cell volume changes elicit Na+/K+- ATPase recruitment and/or activation in cultured bovine corneal endothelial cells. Invest. Ophthalmol. Vis. Sci. 36:S300.
Crawford, K.M. and L.A. Dossett. 1999.  The effect of cryopreservation and subculture on the expression of the sodium pump in cultured bovine corneal endothelial cells.  Invest. Ophthalmol. Vis. Sci. 40:S629.
Crawford, K.M. 2001.  Up-regulation of sodium (Na) pump surface expression in bovine corneal endothelial cells. Invest. Ophthalmol. Vis. Sci. 42:S275.
 
 

Cell culture facility in my lab






Author: Kenneth M. Crawford

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Last Update : Friday, August 10, 2001 - 11:48:32 AM