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Corneal endothelial dystrophy is a progressive disease with gradual loss of vision and characterized by degeneration and dysfunction of corneal endothelial cells. Mutations in SLC4A11, a Na+ dependent OH− transporter, cause congenital hereditary endothelial dystrophy (CHED) and Fuchs’ endothelial corneal dystrophy (FECD), the two most common forms of endothelial degeneration. Along with genetic factors, oxidative stress plays a role in pathogenesis of several corneal diseases. In this study we looked into the role of SLC4A11 in antioxidant stress response in human corneal endothelial cells (HCEnC). We found increased expression of SLC4A11 in presence of oxidative stress. Depletion of SLC4A11 using targeted siRNA, caused an increase in reactive oxygen species, cytochrome c, lowered mitochondrial membrane potential, and reduced cell viability during oxidative stress. Moreover, SLC4A11 was found to be necessary for NRF2 mediated antioxidant gene expression in HCEnC. On the other hand, over expression of SLC4A11 reduces reactive oxygen species levels and increases cell viability. Lastly, CHED tissue specimens show evidence of oxidative stress and reduced expression of NRF2. In conclusion, our data suggests a possible role of SLC4A11 in regulating oxidative stress, and might be responsible for both the etiology and treatment of corneal endothelial dystrophy.

The cornea is a vital component of the eye because it provides approximately 70% of the refraction and focusing of incoming light. Being the outermost surface of the eye, it faces continuous stress from dryness, photodamage, infection, and injury; however, like the skin, the cornea regularly refreshes itself by shedding its epithelial cells, which are readily replaced, keeping the ocular surface stable and functional. This regular turnover of the corneal epithelial cells occurs through the stem cells in the limbus, an annular ring of a tissue surrounding the cornea, separating it from the sclera and the conjunctival membrane. The loss of this reserve of stem cells leads to a condition called limbal stem cell deficiency. Treatment for this disorder has evolved from transplanting whole limbal tissues to the affected eye to transplanting laboratory cultured limbal cells. This procedure is called cultivated limbal epithelial transplantation (CLET). Since its start in 1997, more than 1,000 CLET procedures have been reported from around the world, with varying degrees of success. In this paper, we compare the methods of cultivation and the outcomes and discuss some problem areas, use of other cells as substitutes for limbal epithelium, and various carrier materials used in transplantation. Our analysis suggests that CLET as a treatment for corneal surface damage has come of age. We also highlight a simpler procedure (simple limbal epithelial transplantation) that involves cultivation of limbal tissue in situ on the surface of the cornea in vivo and that has outcomes comparable to CLET.

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Purpose. To determine the role of actin cytoskeleton in the disassembly and reformation of adherens junctions (AJs) and tight junctions (TJs) in bovine corneal endothelial monolayers. Methods. Disassembly and reformation of AJs and TJs were induced by extracellular Ca(2+) depletion and subsequent add-back of Ca(2+), respectively. Resultant changes in the transendothelial electrical resistance (TER), an indicator of integrity of TJs, were measured based on electrical cell-substrate impedance. Phosphorylated myosin light chain (ppMLC), a biochemical measure of actomyosin contraction, and activation of its upstream regulatory molecule RhoA-GTP were assessed by Western blot analysis. Results. Extracellular Ca(2+) depletion led to activation of RhoA, increase in ppMLC, decrease in TER, contraction of the perijunctional actomyosin ring (PAMR), and redistribution of zonula occludens-1 (ZO-1) and cadherins. These effects were reversed on Ca(2+) add-back. Pretreatment with Y-27632 and blebbistatin (as inhibitors of actomyosin contraction) reduced the rate of decline in TER, opposed the contraction of the PAMR, and blocked the redistribution of ZO-1 and cadherins. Both drugs reduced the recovery in TER and opposed the normal redistribution of ZO-1 and cadherins on Ca(2+) add-back. Cytochalasin D, which led to dissolution of the PAMR, also reduced the recovery of TER on Ca(2+) add-back. Conclusions. The (Ca(2+) depletion)-induced disassembly of AJs accelerates the breakdown of TJs through a concomitant increase in the actomyosin contraction of the PAMR. However, these data on reassembly show that a contractile tone of the PAMR is essential for assembly of the apical junctional complex.