Tissue engineering and increased understanding of

corneal endothelial functions have enabled the transplant of cultivated corneal endothelial cell (CEC) sheets and the use of medications to treat corneal endothelial dysfunction [1-3]. Recently, a novel therapeutic concept involving the use of p120 siRNA or Y-27632 (applied topically, injected intracamerally, or expanded ex vivo) has prompted numerous studies on treating corneal endothelial dysfunction in clinical scenarios [1,4-6]. For example, cell injection of rabbit CECs in combination with Y-27632 in the anterior chamber of an animal model helped reconstruct CECs in a monolayer and recover corneal transparency [7]. In a primate model that exhibited endothelial dysfunction after mechanical scraping, transplanting Y-27632-treated CEC sheets resolved corneal edema [8]. Although these studies have reported prom-ising outcomes for the use of p120 siRNA or Y-27632, the individual effects on corneal endothelial proliferation and TJ restoration merit further investigation. The TJ, a multifunctional complex, and its regulation by Rho GTPases, are often overlooked in mediating endothelial renewal. Rho-associated kinase (ROCK), a putative serine/ threonine kinase target for Rho, modulates the actin–myosin cytoskeleton dynamics [9,10]. Disrupting ROCK activity markedly reduces polymerized actin and cytoskeletal rear-rangement [10]. In the corneal endothelium, a thick band of actin cytoskeleton, called the perijunctional actomyosin ring, is located proximal to the apical junctional complexes [11,12]. Activating Rho A and its effector ROCK leads to perijunctional actomyosin ring contraction, reduces cell–cell tethering, and subsequently interrupts the TJ barrier [12-14]. Calcium depletion and readdition have been reported to cause disassembly and reformation of TJ in corneal endothe-lial cells, respectively; however, pretreatment with Y-27632 prevents the normal redistribution of zonula occludens-1 (ZO-1) on the calcium add-back in these cells [15]