Braakman Sietse T, Read A Thomas, Chan Darren W-H, Ethier C Ross, Overby Darryl R
Department of Bioengineering, Imperial College London, London, United Kingdom.
Department of Ophthalmology and Vision Sciences, University of Toronto, Canada.
Exp Eye Res. 2015 Jan;130:87-96. doi: 10.1016/j.exer.2014.11.008. Epub 2014 Nov 13.
All aqueous humor draining through the conventional outflow pathway must cross the endothelium of Schlemm's canal (SC), likely by passing through micron-sized transendothelial pores. SC pores are non-uniformly distributed along the inner wall endothelium, but it is unclear how the distribution of pores relates to the non-uniform or segmental distribution of aqueous humor outflow through the trabecular meshwork. It is hypothesized that regions in the juxtacanalicular tissue (JCT) with higher local outflow should coincide with regions of greater inner wall pore density compared to JCT regions with lower outflow. Three pairs of non-glaucomatous human donor eyes were perfused at 8 mmHg with fluorescent tracer nanospheres to decorate local patterns of outflow segmentation through the JCT. The inner wall was stained for CD31 and/or vimentin and imaged en face using confocal and scanning electron microscopy (SEM). Confocal and SEM images were spatially registered to examine the spatial relationship between inner wall pore density and tracer intensity in the underlying JCT. For each eye, tracer intensity, pore density (n) and pore diameter (D) (for both transcellular "I" and paracellular "B" pores) were measured in 4-7 regions of interest (ROIs; 50 × 150 μm each). Analysis of covariance was used to examine the relationship between tracer intensity and pore density, as well as the relationship between tracer intensity and three pore metrics (nD, nD(2) and nD(3)) that represent the local hydraulic conductivity of the outflow pathway as predicted by various hydrodynamic models. Tracer intensity in the JCT correlated positively with local pore density when considering total pores (p = 0.044) and paracellular B pores on their own (p = 0.016), but not transcellular I-pores on their own (p = 0.54). Local hydraulic conductivity as predicted by the three hydrodynamic models all showed a significant positive correlation with tracer intensity when considering total pores and B-pores (p < 0.0015 and p < 10(-4)) but not I-pores (p > 0.38). These data suggest that aqueous humor passes through micron-sized pores in the inner wall endothelium of SC. Paracellular B-pores appear to have a dominant contribution towards transendothelial filtration across the inner wall relative to transcellular I-pores. Impaired pore formation, as previously described in glaucomatous SC cells, may thereby contribute to greater outflow heterogeneity, outflow obstruction, and IOP elevation in glaucoma.
所有经传统流出途径引流的房水都必须穿过施莱姆管(SC)的内皮,可能是通过微米大小的跨内皮孔。SC孔沿内壁内皮呈非均匀分布,但尚不清楚孔的分布与通过小梁网的房水流出的非均匀或节段性分布之间有何关系。据推测,与流出量较低的近管组织(JCT)区域相比,局部流出量较高的JCT区域应与内壁孔密度较大的区域一致。用荧光示踪纳米球以8 mmHg的压力灌注三对非青光眼患者的供体眼,以描绘通过JCT的流出节段的局部模式。对内壁进行CD31和/或波形蛋白染色,并使用共聚焦显微镜和扫描电子显微镜(SEM)进行正面成像。对共聚焦图像和SEM图像进行空间配准,以检查内壁孔密度与下方JCT中示踪剂强度之间的空间关系。对于每只眼睛,在4 - 7个感兴趣区域(ROI;每个区域50×150μm)中测量示踪剂强度、孔密度(n)和孔径(D)(跨细胞“ I”孔和细胞旁“ B”孔)。使用协方差分析来检查示踪剂强度与孔密度之间的关系,以及示踪剂强度与三种孔指标(nD、nD²和nD³)之间的关系,这些指标代表了各种流体动力学模型预测的流出途径的局部水力传导率。当考虑总孔时,JCT中的示踪剂强度与局部孔密度呈正相关(p = 0.044),单独考虑细胞旁B孔时也呈正相关(p = 0.016),但单独考虑跨细胞I孔时则不然(p = 0.54)。当考虑总孔和B孔时,三种流体动力学模型预测的局部水力传导率均与示踪剂强度呈显著正相关(p < 0.0015和p < 10⁻⁴),但与I孔无关(p > 0.38)。这些数据表明,房水通过SC内壁内皮中的微米大小的孔。相对于跨细胞I孔,细胞旁B孔似乎对跨内壁的跨内皮滤过起主要作用。如先前在青光眼性SC细胞中所描述的,孔形成受损可能因此导致青光眼患者更大的流出异质性、流出阻塞和眼压升高。