Biomechanical, ultrastructural, and electrophysiological characterization of the non-human primate experimental glaucoma model.

Laser-induced experimental glaucoma (ExGl) in non-human primates (NHPs) is a common animal model for ocular drug development. While many features of human hypertensive glaucoma are replicated in this model, structural and functional changes in the unlasered portions of trabecular meshwork (TM) of laser-treated primate eyes are understudied. We studied NHPs with ExGl of several years duration. As expected, ExGl eyes exhibited selective reductions of the retinal nerve fiber layer that correlate with electrophysiologic measures documenting a link between morphologic and elctrophysiologic endpoints. Softening of unlasered TM in ExGl eyes compared to untreated controls was observed. The degree of TM softening was consistent, regardless of pre-mortem clinical findings including severity of IOP elevation, retinal nerve fiber layer thinning, or electrodiagnostic findings. Importantly, this softening is contrary to TM stiffening reported in glaucomatous human eyes. Furthermore, microscopic analysis of unlasered TM from eyes with ExGl demonstrated TM thinning with collapse of Schlemm's canal; and proteomic analysis confirmed downregulation of metabolic and structural proteins. These data demonstrate unexpected and compensatory changes involving the TM in the NHP model of ExGl. The data suggest that compensatory mechanisms exist in normal animals and respond to elevated IOP through softening of the meshwork to increase outflow.

Endothelial glycocalyx layer in the aqueous outflow pathway of bovine and human eyes.

The glycocalyx layer on the vascular endothelium is known to have an important role as a transport barrier and in the mechanotransduction of fluid shear stress. The detailed structure and distribution of the glycocalyx in the bovine and human aqueous humor outflow pathways has not yet been reported. The purpose of this study was to determine whether this layer exists in the bovine and human aqueous outflow pathways and to compare the distribution and thickness therein. Enucleated bovine (N = 4) and human (N = 4) eyes were fixed using Alcian Blue to preserve the glycocalyx. The glycocalyx distribution and thickness (in regions where it was seen) were measured on the trabecular beams (TM), Schlemm's canal (SC)/aqueous plexus (AP), and collector channels (CC). The glycocalyx, which appears as a layer of hair-like brushes, coats the surface of the endothelium non-uniformly in the bovine and human aqueous outflow pathways with a thickness in bovine eyes of 68-122 nm and in human eyes of 52-166 nm (25th to 75th percentiles). The distribution of the glycocalyx in different regions of the outflow pathway is not the same between bovine and human eyes. In both species, the glycocalyx was most uniform in the CCs. Less coverage of glycocalyx was found in the AP than the TM in bovine eyes, while more coverage was found in SC than the TM in human eyes. Most interestingly, glycocalyx was also found filling most pores of the endothelium of AP/SC in both bovine and human eyes. Glycocalyx was usually not found coating the inner membranes of the giant vacuoles (GVs); however, in GVs with a visible pore, glycocalyx was frequently observed on the inner membranes of the GVs. Based on our findings and those from the vascular endothelium, it is likely that the glycocalyx in SC plays a role in transduction of shear stress and perhaps regulation of outflow resistance.

Morphological and hydrodynamic correlations with increasing outflow facility by rho-kinase inhibitor Y-27632.

Abstract Rho-kinase inhibitors affect actomyosin cytoskeletal networks and have been shown to significantly increase outflow facility and lower intraocular pressure in various animal models and human eyes. This article summarizes common morphological changes in the trabecular meshwork induced by Rho-kinase inhibitors and specifically compares the morphological and hydrodynamic correlations with increased outflow facility by Rho-kinase inhibitor, Y-27632, in bovine, monkey, and human eyes under similar experimental conditions. Interspecies comparison has shown that morphological changes in the juxtacanalicular connective tissue (JCT) of these 3 species were different. However, these different morphological changes in the JCT, no matter if it's separation between the JCT and inner wall in bovine eyes, or separation between the JCT cells or between the JCT cells and their matrix in monkey eyes, or even no separation between the inner wall and the JCT but a more subtle expansion of the JCT in human eyes, appear to correlate with the increased percent change of outflow facility. More importantly, these different morphological changes all resulted in an increase in effective filtration area, which was positively correlated with increased outflow facility in all 3 species. These results suggest a link among changes in outflow facility, tissue architecture, and aqueous outflow pattern. Y-27632 increases outflow facility by redistributing aqueous outflow through a looser and larger area in the JCT.

Effects of Y27632 on aqueous humor outflow facility with changes in hydrodynamic pattern and morphology in human eyes.

PURPOSE: To determine the effect of Y27632, a Rho-kinase inhibitor on aqueous outflow facility, flow pattern, and juxtacanalicular tissue (JCT)/trabecular meshwork (TM) morphology in human eyes. METHODS: Sixteen enucleated human eyes were perfused with PBS plus glucose (GPBS) at 15 mm Hg to establish the baseline outflow facility. Six eyes were perfused for short-duration (30 minute) with either 50 µM Y27632 or GPBS (n = 3 per group). Ten eyes were perfused for long duration (3 hours) with either 50 µM Y27632 or GPBS (n = 5 per group). Outflow pattern was labeled using fluorescent microspheres, and effective filtration length (EFL) was measured. Morphologic changes and their relationship to EFL and facility were analyzed. RESULTS: Outflow facility significantly increased after short-duration perfusion with Y27632 compared with its own baseline (P = 0.03), but did not reach statistical significance compared with its controls (P = 0.07). Outflow facility (P = 0.01) and EFL (P < 0.05) were significantly increased after long-duration perfusion with Y27632 compared with its controls. Increases in outflow facility and EFL demonstrated a positive correlation. Morphologically, the TM and JCT of high-tracer regions were more expanded compared with low-tracer regions. A significant increase in JCT thickness was found in the long-duration Y27632 group compared with its control group (10.0 vs. 8.0 µm, P < 0.01). CONCLUSIONS: Y27632 increases outflow facility in human eyes. This increase correlates positively with an increase in EFL, which is associated with an increased expansion in the JCT. Our data suggest that EFL could serve as a novel parameter to correlate with outflow facility.

Effect of pre-eclampsia-eclampsia on major cardiovascular events among peripartum women in Taiwan.

There is no large-scale population-based study to clarify the association between major adverse cardiovascular events (MACEs) and pre-eclampsia/eclampsia. A population-based Taiwanese cohort study was performed in 1,132,064 parturients from 1999 to 2003 using a dataset linking birth certificates and National Health Insurance hospital discharge data. Sociodemographic factors and obstetric complications were used in multivariate logistic regression models to determine adjusted hazard ratios of pre-eclampsia/eclampsia on risks of MACEs and mortality during pregnancy to at least the third year postpartum. Incidence rates of MACEs and all maternal mortality in women with pre-eclampsia/eclampsia were 16.21 and 40.38 per 100,000 patients per year, respectively. Women with pre-eclampsia/eclampsia had a 13.0-fold higher incidence of myocardial infarction, a 8.3-fold higher incidence of heart failure, a 14.5-fold higher incidence of stroke, a 12.6-fold higher incidence of MACEs, a 7.3-fold higher incidence of MACEs without stroke, a 2.3-fold higher incidence of MACE-related deaths, and a 6.4-fold higher incidence of overall death than women without pre-eclampsia/eclampsia. Kaplan-Meier survival curve discriminated in MACEs, nonstroke MACEs, MACE related death and overall death. In conclusion, women with pre-eclampsia/eclampsia have a significantly higher risk of MACEs, especially myocardial infarction and stroke, during pregnancy and their risk remains significant to ≥36 months postpartum. Our results suggest that women with pre-eclampsia/eclampsia should be closely monitored during pregnancy and for up to ≥3 years postpartum.

Preeclampsia-eclampsia and the risk of stroke among peripartum in Taiwan.

BACKGROUND AND PURPOSE: The occurrence of preeclampsia-eclampsia during pregnancy has been reported to increase the risk of stroke in mainly Western populations. However, few studies have evaluated stroke risk in Asian populations and followed women beyond the early postpartum period. Thus, the present study determined the risk of stroke in women in Taiwan during pregnancy and the first postpartum year. METHODS: A population-based cohort study was performed on 1,132,019 parturients during 1999 to 2003 using a dataset linking birth certificates and National Health Insurance hospital discharge data. Stroke-free survival rates were estimated using the Kaplan-Meier method, and the log-rank test was used to examine the effect of preelampsia-eclampsia on the prevalence of stroke. Sociodemographic factors and obstetric complications were used in multivariate logistic regression models to determine the adjusted odds ratios of preeclampsia-eclampsia on the risk of hemorrhagic and ischemic stroke during pregnancy and within the first postpartum year. RESULTS: The incidence of stroke was 21.47 cases per 100,000 deliveries. There were 139 cases of hemorrhagic stroke and 107 cases of ischemic stroke. The respective adjusted relative risk of preeclampsia-eclampsia for hemorrhagic and ischemic stroke were 10.68 (95% CI, 3.40 to 33.59) and 40.86 (95% CI, 12.14 to 137.47) within 3 months antepartum; 6.45 (95% CI, 1.42 to 29.29) and 34.71 (95% CI, 11.08 to 108.68) in the first 3 days postpartum; 5.61 (95% CI, 0.71 to 44.10) and 11.23 (95% CI, 2.45 to 51.59) from 3 days to 6 weeks postpartum; 11.76 (95% CI, 4.05 to 34.11) and 11.60 (95% CI, 3.30 to 40.82) from 6 weeks to 6 months pospartum; and 19.90 (95% CI, 7.75 to 51.11) and 4.35 (95% CI, 0.58 to 32.92) from 6 months to 12 months postpartum. CONCLUSIONS: Women with preeclampsia-eclampsia have a significantly higher risk of stroke during pregnancy and in the first postpartum year. These results suggest that women with preeclampsia-eclampsia should be closely monitored even after pregnancy.