The Experts below are selected from a list of 6273 Experts worldwide ranked by ideXlab platform
Shigeru Kinoshita - One of the best experts on this subject based on the ideXlab platform.
-
Activation of the Rho/Rho Kinase Signaling Pathway Is Involved in Cell Death of Corneal Endothelium
2020Co-Authors: Naoki Okumura, Noriko Koizumi, Shigeru Kinoshita, Keita Fujii, Takato Kagami, Nakahara Makiko, Miu KitaharaAbstract:PURPOSE. Rho kinase (ROCK) pathways control fundamental cell functions, making ROCK an important therapeutic target in several pathophysiologic conditions. The purpose of this study was to investigate whether inhibition of ROCK can suppress apoptosis of the Corneal Endothelium and to determine the role of ROCK signaling in regulating apoptosis. METHODS. The effects of inhibitors of ROCK or myosin light chain (MLC) were evaluated in cultured monkey Corneal endothelial cells (MCECs) irradiated with ultraviolet (UV) (100 J/m 2 ) to induce apoptosis. Annexin V and TUNEL staining and Western blot for apoptosis-related proteins and focal adhesion complexes were then performed. RhoA activation was further evaluated by pull-down assays. ROCK inhibitor and caspase inhibitor effects on apoptosis were also evaluated in MCECs treated with ethylene glycol tetraacetic acid (EGTA) to induce MLC phosphorylation. RESULTS. ROCK or MLC inhibition suppressed the caspase-3 cleavage and Annexin V and TUNEL expression typically seen during UV-mediated apoptosis of MCECs. The apoptotic stimulus activated RhoA and then induced phosphorylation of MLC via ROCK activation. EGTA-mediated phosphorylation of MLC was sufficient to induce the loss of cell contact with the substrate and subsequent apoptosis. Western blot showed that ROCK inhibition upregulated the expression of the focal adhesion complex in adhered cells, following UV stress. CONCLUSIONS. Apoptotic stimuli activated Rho/ROCK/MLC phosphorylation in the Corneal Endothelium, and subsequent actomyosin contraction induced apoptosis by loss of cell adhesion. ROCK inhibition suppressed MLC phosphorylation and subsequent cell death, and it counteracted the loss of cell adhesion by activating the focal adhesion complex
-
the rock inhibitor eye drop accelerates Corneal Endothelium wound healing
Investigative Ophthalmology & Visual Science, 2013Co-Authors: Naoki Okumura, Noriko Koizumi, Morio Ueno, Yuji Sakamoto, Junji Hamuro, Eunduck P Kay, Shinichiro Nakamura, Shigeru KinoshitaAbstract:Purpose To evaluate the effect of Rho kinase (ROCK)-inhibitor eye drops on a Corneal endothelial dysfunction primate model and human clinical case series of Corneal endothelial dysfunction. Methods As a Corneal-endothelial partially injured model, the Corneal Endothelium of seven cynomolgus monkeys was damaged by transCorneal freezing; 10 mm of rock inhibitor Y-27632 was then applied topically 6 times daily. The phenotype of the reconstructed Corneal Endothelium was evaluated by immunohistochemical analysis and noncontact specular microscopy. For clinical study, the effect of Y-27632 eye drops after transCorneal freezing was evaluated in eight Corneal endothelial dysfunction patients: four central Corneal edema patients and four diffuse Corneal edema patients. Results Slit-lamp microscopy revealed that both Y-27632-treated and -nontreated corneas became hazy after transCorneal freezing, and then recovered their transparency within 4 weeks. ROCK inhibitor Y-27632 promoted recovery of Corneal endothelial cell density and wound healing in terms of both morphology and function. The percentage of ZO-1 and Na(+)/K(+)-ATPase positive cells in the regenerated area in the Y-27632 group was significantly higher than in the controls. Noncontact specular microscopy revealed that Corneal endothelial cell density was significantly higher in the Y-27632 group compared with the controls at 4 weeks; cell density reached approximately 3000 cells/mm(2), as opposed to 1500 cells/mm(2) in the control group. In addition to the animal study findings, the clinical study findings showed that Y-27632 eye drops effectively improved Corneal edema of Corneal endothelial dysfunction patients with central edema. Conclusions These findings show that rock inhibitor Y-27632 eye drops promote Corneal endothelial wound healing in a primate animal model and suggest the possibility of Y-27632 as a novel therapeutic modality for certain forms of Corneal endothelial dysfunction. (http://www.umin.ac.jp/ctr/ number, UMIN000003625.).
-
enhancement of Corneal Endothelium wound healing by rho associated kinase rock inhibitor eye drops
British Journal of Ophthalmology, 2011Co-Authors: Naoki Okumura, Noriko Koizumi, Morio Ueno, Yuji Sakamoto, Hiroaki Takahashi, K Hirata, Ryuzo Torii, Junji Hamuro, Shigeru KinoshitaAbstract:AIM: To demonstrate the efficacy of Rho-associated kinase (ROCK) inhibitor Y-27632 for Corneal endothelial wound healing both in in vitro and in vivo models. METHODS: As an in vitro model, cultivated cynomolgus monkey Corneal endothelial cells were scraped to create a linear defect. The wound distance was then determined during a 24-h culture in the presence or absence of 10 μM of Y-27632. As an in vivo model, central Corneal Endothelium of Japanese white rabbits was damaged by transCorneal freezing, then 10 mM of Y-27632 was applied topically six times daily for 48 h. The wound area of the Corneal Endothelium was evaluated after 48 h. RESULTS: The mean wound distance in the cultured Corneal endothelial cells was significantly shorter in the Y-27632 group than in the control group. In the rabbit model, the mean wound area of the Y-27632 group was significantly smaller than that of the control group. CONCLUSION: This study demonstrated that ROCK inhibitor Y-27632 promotes Corneal endothelial wound healing both in in vitro and in vivo.
Jorge Fischbarg - One of the best experts on this subject based on the ideXlab platform.
-
Corneal Endothelium transports fluid in the absence of net solute transport
Biochimica et Biophysica Acta, 2007Co-Authors: Friedrich P J Diecke, P Iserovich, Jorge FischbargAbstract:The Corneal Endothelium transports fluid from the Corneal stroma to the aqueous humor, thus maintaining stromal transparency by keeping it relatively dehydrated. This fluid transport mechanism is thought to be driven by the transcellular transports of HCO(3)(-) and Cl(-) in the same direction, from stroma to aqueous. In parallel to these anion movements, for electroneutrality, there are paracellular Na(+) and transcellular K(+) transports in the same direction. The resulting net flow of solute might generate local osmotic gradients that drive fluid transport. However, there are reports that some 50% residual fluid transport remains in nominally HCO(3)(-) free solutions. We have examined the driving force for this residual fluid transport. We confirm that in nominally HCO(3)(-) free solutions, 48% of control fluid transport remains. When in addition Cl(-) channels are inhibited, 30% of control fluid movement still remains. Addition of a carbonic anhydrase inhibitor has no further effect. These manipulations combined inhibit the transcellular transport of all anions, without which there cannot be any net transport of solute and consequently no local osmotic gradients, yet there is residual fluid movement. Only the further addition of benzamil, an inhibitor of epithelial Na(+) channels, abolishes fluid transport completely. Our data are inconsistent with transcellular local osmosis and instead support the paradigm of paracellular fluid transport driven by electro-osmotic coupling.
-
the role of the tight junction in paracellular fluid transport across Corneal Endothelium electro osmosis as a driving force
The Journal of Membrane Biology, 2006Co-Authors: Jorge Fischbarg, P Iserovich, Friedrich P J Diecke, A A RubashkinAbstract:The mechanism of epithelial fluid transport is controversial and remains unsolved. Experimental difficulties pose obstacles for work on a complex phenomenon in delicate tissues. However, the Corneal Endothelium is a relatively simple system to which powerful experimental tools can be applied. In recent years our laboratory has developed experimental evidence and theoretical insights that illuminate the mechanism of fluid transport across this leaky epithelium. Our evidence points to fluid being transported via the paracellular route by a mechanism requiring junctional integrity, which we attribute to electro-osmotic coupling at the junctions. Fluid movements can be produced by electrical currents. The direction of the movement can be reversed by current reversal or by changing junctional electrical charges by polylysine. Aquaporin 1 (AQP1) is the only AQP present in these cells, and its deletion in AQP1 null mice significantly affects cell osmotic permeability but not fluid transport, which militates against the presence of sizable water movements across the cell. By contrast, AQP1 null mice cells have reduced regulatory volume decrease (only 60% of control), which suggests a possible involvement of AQP1 in either the function or the expression of volume-sensitive membrane channels/transporters. A mathematical model of Corneal Endothelium predicts experimental results only when based on paracellular electro-osmosis, and not when transcellular local osmosis is assumed instead.
-
The Role of the Tight Junction in Paracellular Fluid Transport across Corneal Endothelium. Electro-osmosis as a Driving Force
The Journal of Membrane Biology, 2006Co-Authors: Jorge Fischbarg, P Iserovich, Friedrich P J Diecke, A A RubashkinAbstract:The mechanism of epithelial fluid transport is controversial and remains unsolved. Experimental difficulties pose obstacles for work on a complex phenomenon in delicate tissues. However, the Corneal Endothelium is a relatively simple system to which powerful experimental tools can be applied. In recent years our laboratory has developed experimental evidence and theoretical insights that illuminate the mechanism of fluid transport across this leaky epithelium. Our evidence points to fluid being transported via the paracellular route by a mechanism requiring junctional integrity, which we attribute to electro-osmotic coupling at the junctions. Fluid movements can be produced by electrical currents. The direction of the movement can be reversed by current reversal or by changing junctional electrical charges by polylysine. Aquaporin 1 (AQP1) is the only AQP present in these cells, and its deletion in AQP1 null mice significantly affects cell osmotic permeability but not fluid transport, which militates against the presence of sizable water movements across the cell. By contrast, AQP1 null mice cells have reduced regulatory volume decrease (only 60% of control), which suggests a possible involvement of AQP1 in either the function or the expression of volume-sensitive membrane channels/transporters. A mathematical model of Corneal Endothelium predicts experimental results only when based on paracellular electro-osmosis, and not when transcellular local osmosis is assumed instead. Our experimental findings in Corneal Endothelium have allowed us to develop a novel paradigm for this preparation that includes: (1) paracellular fluid flow; (2) a crucial role for the junctions; (3) hypotonicity of the primary secretion; (4) an AQP role in regulation and not as a significant water pathway. These elements are remarkably similar to those proposed by the Hill laboratory for leaky epithelia.
Naoki Okumura - One of the best experts on this subject based on the ideXlab platform.
-
analysis of immune cells on donor Corneal Endothelium after Corneal transplantation using the hrt rostock cornea module
Cornea, 2021Co-Authors: Naoki Okumura, Noriko Koizumi, Thenmozhi Velumani, Farhath Hadiya, Vasanthi Padmanaban, Yuya Komori, Naoya Hanada, Taisuke Hirono, Sangly P Srinivas, Prema PadmanabhanAbstract:Purpose The aim of this study was to investigate the immune cells on Corneal Endothelium of the graft in patients who underwent penetrating keratoplasty (PK), Descemet-stripping endothelial keratoplasty (DSEK), and Descemet membrane endothelial keratoplasty (DMEK). Methods A total of 43 eyes of 43 patients who underwent PK (17 eyes), DSEK (13 eyes), and DMEK (13 eyes) and who did not show any sign of graft rejection were recruited for the study. Patients who underwent cataract surgery (26 eyes) served as controls. Immune cells on the Corneal Endothelium were examined with laser in vivo confocal microscopy. The associations between the Corneal endothelial cell density, type of keratoplasty, aqueous flare, repeated keratoplasty, and time after surgery versus the density of immune cells were investigated. Results In vivo confocal microscopy visualized similar numbers of immune cells on the Corneal Endothelium in the PK, DSEK, and DMEK groups, whereas no immune cells were observed in any of the control patients. The numbers of immune cells tended to be higher in regraft eyes in the PK group (P = 0.00221) and in the DSEK group (P = 0.168) than those in the primary graft eyes. No significant association was found between the density of immune cells and Corneal endothelial cell density in the PK, DSEK, and DMEK groups. Conclusions Immune cells were observed to a similar extent in the eyes of PK, DSEK, and DMEK subjects even in the absence of any clinical sign of immune rejection. A further prospective longitudinal study will evaluate the effect of immune cells on long-term graft survival and the risk for graft rejection.
-
Activation of the Rho/Rho Kinase Signaling Pathway Is Involved in Cell Death of Corneal Endothelium
2020Co-Authors: Naoki Okumura, Noriko Koizumi, Shigeru Kinoshita, Keita Fujii, Takato Kagami, Nakahara Makiko, Miu KitaharaAbstract:PURPOSE. Rho kinase (ROCK) pathways control fundamental cell functions, making ROCK an important therapeutic target in several pathophysiologic conditions. The purpose of this study was to investigate whether inhibition of ROCK can suppress apoptosis of the Corneal Endothelium and to determine the role of ROCK signaling in regulating apoptosis. METHODS. The effects of inhibitors of ROCK or myosin light chain (MLC) were evaluated in cultured monkey Corneal endothelial cells (MCECs) irradiated with ultraviolet (UV) (100 J/m 2 ) to induce apoptosis. Annexin V and TUNEL staining and Western blot for apoptosis-related proteins and focal adhesion complexes were then performed. RhoA activation was further evaluated by pull-down assays. ROCK inhibitor and caspase inhibitor effects on apoptosis were also evaluated in MCECs treated with ethylene glycol tetraacetic acid (EGTA) to induce MLC phosphorylation. RESULTS. ROCK or MLC inhibition suppressed the caspase-3 cleavage and Annexin V and TUNEL expression typically seen during UV-mediated apoptosis of MCECs. The apoptotic stimulus activated RhoA and then induced phosphorylation of MLC via ROCK activation. EGTA-mediated phosphorylation of MLC was sufficient to induce the loss of cell contact with the substrate and subsequent apoptosis. Western blot showed that ROCK inhibition upregulated the expression of the focal adhesion complex in adhered cells, following UV stress. CONCLUSIONS. Apoptotic stimuli activated Rho/ROCK/MLC phosphorylation in the Corneal Endothelium, and subsequent actomyosin contraction induced apoptosis by loss of cell adhesion. ROCK inhibition suppressed MLC phosphorylation and subsequent cell death, and it counteracted the loss of cell adhesion by activating the focal adhesion complex
-
the rock inhibitor eye drop accelerates Corneal Endothelium wound healing
Investigative Ophthalmology & Visual Science, 2013Co-Authors: Naoki Okumura, Noriko Koizumi, Morio Ueno, Yuji Sakamoto, Junji Hamuro, Eunduck P Kay, Shinichiro Nakamura, Shigeru KinoshitaAbstract:Purpose To evaluate the effect of Rho kinase (ROCK)-inhibitor eye drops on a Corneal endothelial dysfunction primate model and human clinical case series of Corneal endothelial dysfunction. Methods As a Corneal-endothelial partially injured model, the Corneal Endothelium of seven cynomolgus monkeys was damaged by transCorneal freezing; 10 mm of rock inhibitor Y-27632 was then applied topically 6 times daily. The phenotype of the reconstructed Corneal Endothelium was evaluated by immunohistochemical analysis and noncontact specular microscopy. For clinical study, the effect of Y-27632 eye drops after transCorneal freezing was evaluated in eight Corneal endothelial dysfunction patients: four central Corneal edema patients and four diffuse Corneal edema patients. Results Slit-lamp microscopy revealed that both Y-27632-treated and -nontreated corneas became hazy after transCorneal freezing, and then recovered their transparency within 4 weeks. ROCK inhibitor Y-27632 promoted recovery of Corneal endothelial cell density and wound healing in terms of both morphology and function. The percentage of ZO-1 and Na(+)/K(+)-ATPase positive cells in the regenerated area in the Y-27632 group was significantly higher than in the controls. Noncontact specular microscopy revealed that Corneal endothelial cell density was significantly higher in the Y-27632 group compared with the controls at 4 weeks; cell density reached approximately 3000 cells/mm(2), as opposed to 1500 cells/mm(2) in the control group. In addition to the animal study findings, the clinical study findings showed that Y-27632 eye drops effectively improved Corneal edema of Corneal endothelial dysfunction patients with central edema. Conclusions These findings show that rock inhibitor Y-27632 eye drops promote Corneal endothelial wound healing in a primate animal model and suggest the possibility of Y-27632 as a novel therapeutic modality for certain forms of Corneal endothelial dysfunction. (http://www.umin.ac.jp/ctr/ number, UMIN000003625.).
-
enhancement of Corneal Endothelium wound healing by rho associated kinase rock inhibitor eye drops
British Journal of Ophthalmology, 2011Co-Authors: Naoki Okumura, Noriko Koizumi, Morio Ueno, Yuji Sakamoto, Hiroaki Takahashi, K Hirata, Ryuzo Torii, Junji Hamuro, Shigeru KinoshitaAbstract:AIM: To demonstrate the efficacy of Rho-associated kinase (ROCK) inhibitor Y-27632 for Corneal endothelial wound healing both in in vitro and in vivo models. METHODS: As an in vitro model, cultivated cynomolgus monkey Corneal endothelial cells were scraped to create a linear defect. The wound distance was then determined during a 24-h culture in the presence or absence of 10 μM of Y-27632. As an in vivo model, central Corneal Endothelium of Japanese white rabbits was damaged by transCorneal freezing, then 10 mM of Y-27632 was applied topically six times daily for 48 h. The wound area of the Corneal Endothelium was evaluated after 48 h. RESULTS: The mean wound distance in the cultured Corneal endothelial cells was significantly shorter in the Y-27632 group than in the control group. In the rabbit model, the mean wound area of the Y-27632 group was significantly smaller than that of the control group. CONCLUSION: This study demonstrated that ROCK inhibitor Y-27632 promotes Corneal endothelial wound healing both in in vitro and in vivo.
A A Rubashkin - One of the best experts on this subject based on the ideXlab platform.
-
the role of the tight junction in paracellular fluid transport across Corneal Endothelium electro osmosis as a driving force
The Journal of Membrane Biology, 2006Co-Authors: Jorge Fischbarg, P Iserovich, Friedrich P J Diecke, A A RubashkinAbstract:The mechanism of epithelial fluid transport is controversial and remains unsolved. Experimental difficulties pose obstacles for work on a complex phenomenon in delicate tissues. However, the Corneal Endothelium is a relatively simple system to which powerful experimental tools can be applied. In recent years our laboratory has developed experimental evidence and theoretical insights that illuminate the mechanism of fluid transport across this leaky epithelium. Our evidence points to fluid being transported via the paracellular route by a mechanism requiring junctional integrity, which we attribute to electro-osmotic coupling at the junctions. Fluid movements can be produced by electrical currents. The direction of the movement can be reversed by current reversal or by changing junctional electrical charges by polylysine. Aquaporin 1 (AQP1) is the only AQP present in these cells, and its deletion in AQP1 null mice significantly affects cell osmotic permeability but not fluid transport, which militates against the presence of sizable water movements across the cell. By contrast, AQP1 null mice cells have reduced regulatory volume decrease (only 60% of control), which suggests a possible involvement of AQP1 in either the function or the expression of volume-sensitive membrane channels/transporters. A mathematical model of Corneal Endothelium predicts experimental results only when based on paracellular electro-osmosis, and not when transcellular local osmosis is assumed instead.
-
The Role of the Tight Junction in Paracellular Fluid Transport across Corneal Endothelium. Electro-osmosis as a Driving Force
The Journal of Membrane Biology, 2006Co-Authors: Jorge Fischbarg, P Iserovich, Friedrich P J Diecke, A A RubashkinAbstract:The mechanism of epithelial fluid transport is controversial and remains unsolved. Experimental difficulties pose obstacles for work on a complex phenomenon in delicate tissues. However, the Corneal Endothelium is a relatively simple system to which powerful experimental tools can be applied. In recent years our laboratory has developed experimental evidence and theoretical insights that illuminate the mechanism of fluid transport across this leaky epithelium. Our evidence points to fluid being transported via the paracellular route by a mechanism requiring junctional integrity, which we attribute to electro-osmotic coupling at the junctions. Fluid movements can be produced by electrical currents. The direction of the movement can be reversed by current reversal or by changing junctional electrical charges by polylysine. Aquaporin 1 (AQP1) is the only AQP present in these cells, and its deletion in AQP1 null mice significantly affects cell osmotic permeability but not fluid transport, which militates against the presence of sizable water movements across the cell. By contrast, AQP1 null mice cells have reduced regulatory volume decrease (only 60% of control), which suggests a possible involvement of AQP1 in either the function or the expression of volume-sensitive membrane channels/transporters. A mathematical model of Corneal Endothelium predicts experimental results only when based on paracellular electro-osmosis, and not when transcellular local osmosis is assumed instead. Our experimental findings in Corneal Endothelium have allowed us to develop a novel paradigm for this preparation that includes: (1) paracellular fluid flow; (2) a crucial role for the junctions; (3) hypotonicity of the primary secretion; (4) an AQP role in regulation and not as a significant water pathway. These elements are remarkably similar to those proposed by the Hill laboratory for leaky epithelia.
Friedrich P J Diecke - One of the best experts on this subject based on the ideXlab platform.
-
Corneal Endothelium transports fluid in the absence of net solute transport
Biochimica et Biophysica Acta, 2007Co-Authors: Friedrich P J Diecke, P Iserovich, Jorge FischbargAbstract:The Corneal Endothelium transports fluid from the Corneal stroma to the aqueous humor, thus maintaining stromal transparency by keeping it relatively dehydrated. This fluid transport mechanism is thought to be driven by the transcellular transports of HCO(3)(-) and Cl(-) in the same direction, from stroma to aqueous. In parallel to these anion movements, for electroneutrality, there are paracellular Na(+) and transcellular K(+) transports in the same direction. The resulting net flow of solute might generate local osmotic gradients that drive fluid transport. However, there are reports that some 50% residual fluid transport remains in nominally HCO(3)(-) free solutions. We have examined the driving force for this residual fluid transport. We confirm that in nominally HCO(3)(-) free solutions, 48% of control fluid transport remains. When in addition Cl(-) channels are inhibited, 30% of control fluid movement still remains. Addition of a carbonic anhydrase inhibitor has no further effect. These manipulations combined inhibit the transcellular transport of all anions, without which there cannot be any net transport of solute and consequently no local osmotic gradients, yet there is residual fluid movement. Only the further addition of benzamil, an inhibitor of epithelial Na(+) channels, abolishes fluid transport completely. Our data are inconsistent with transcellular local osmosis and instead support the paradigm of paracellular fluid transport driven by electro-osmotic coupling.
-
the role of the tight junction in paracellular fluid transport across Corneal Endothelium electro osmosis as a driving force
The Journal of Membrane Biology, 2006Co-Authors: Jorge Fischbarg, P Iserovich, Friedrich P J Diecke, A A RubashkinAbstract:The mechanism of epithelial fluid transport is controversial and remains unsolved. Experimental difficulties pose obstacles for work on a complex phenomenon in delicate tissues. However, the Corneal Endothelium is a relatively simple system to which powerful experimental tools can be applied. In recent years our laboratory has developed experimental evidence and theoretical insights that illuminate the mechanism of fluid transport across this leaky epithelium. Our evidence points to fluid being transported via the paracellular route by a mechanism requiring junctional integrity, which we attribute to electro-osmotic coupling at the junctions. Fluid movements can be produced by electrical currents. The direction of the movement can be reversed by current reversal or by changing junctional electrical charges by polylysine. Aquaporin 1 (AQP1) is the only AQP present in these cells, and its deletion in AQP1 null mice significantly affects cell osmotic permeability but not fluid transport, which militates against the presence of sizable water movements across the cell. By contrast, AQP1 null mice cells have reduced regulatory volume decrease (only 60% of control), which suggests a possible involvement of AQP1 in either the function or the expression of volume-sensitive membrane channels/transporters. A mathematical model of Corneal Endothelium predicts experimental results only when based on paracellular electro-osmosis, and not when transcellular local osmosis is assumed instead.
-
The Role of the Tight Junction in Paracellular Fluid Transport across Corneal Endothelium. Electro-osmosis as a Driving Force
The Journal of Membrane Biology, 2006Co-Authors: Jorge Fischbarg, P Iserovich, Friedrich P J Diecke, A A RubashkinAbstract:The mechanism of epithelial fluid transport is controversial and remains unsolved. Experimental difficulties pose obstacles for work on a complex phenomenon in delicate tissues. However, the Corneal Endothelium is a relatively simple system to which powerful experimental tools can be applied. In recent years our laboratory has developed experimental evidence and theoretical insights that illuminate the mechanism of fluid transport across this leaky epithelium. Our evidence points to fluid being transported via the paracellular route by a mechanism requiring junctional integrity, which we attribute to electro-osmotic coupling at the junctions. Fluid movements can be produced by electrical currents. The direction of the movement can be reversed by current reversal or by changing junctional electrical charges by polylysine. Aquaporin 1 (AQP1) is the only AQP present in these cells, and its deletion in AQP1 null mice significantly affects cell osmotic permeability but not fluid transport, which militates against the presence of sizable water movements across the cell. By contrast, AQP1 null mice cells have reduced regulatory volume decrease (only 60% of control), which suggests a possible involvement of AQP1 in either the function or the expression of volume-sensitive membrane channels/transporters. A mathematical model of Corneal Endothelium predicts experimental results only when based on paracellular electro-osmosis, and not when transcellular local osmosis is assumed instead. Our experimental findings in Corneal Endothelium have allowed us to develop a novel paradigm for this preparation that includes: (1) paracellular fluid flow; (2) a crucial role for the junctions; (3) hypotonicity of the primary secretion; (4) an AQP role in regulation and not as a significant water pathway. These elements are remarkably similar to those proposed by the Hill laboratory for leaky epithelia.