Yang Chen-Yuan Charlie, Huynh Tiffany, Johnson Mark, Gong Haiyan
Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, USA; Department of Ophthalmology, Boston University School of Medicine, Boston, MA, USA.
Department of Ophthalmology, Boston University School of Medicine, Boston, MA, USA.
Exp Eye Res. 2014 Nov;128:27-33. doi: 10.1016/j.exer.2014.08.015. Epub 2014 Sep 9.
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.
血管内皮上的糖萼层作为一种运输屏障以及在流体剪切应力的机械转导中发挥着重要作用。糖萼在牛和人房水流出途径中的详细结构和分布尚未见报道。本研究的目的是确定该层是否存在于牛和人的房水流出途径中，并比较其在其中的分布和厚度。摘除的牛眼（N = 4）和人眼（N = 4）用阿尔辛蓝固定以保存糖萼。在小梁网（TM）、施莱姆管（SC）/房水丛（AP）和集合管（CC）上测量糖萼的分布和厚度（在可见区域）。糖萼表现为一层毛发状刷状物，在牛和人的房水流出途径中不均匀地覆盖在内皮表面，牛眼中厚度为68 - 122纳米，人眼中厚度为52 - 166纳米（第25至75百分位数）。糖萼在流出途径不同区域的分布在牛眼和人眼之间并不相同。在这两个物种中，糖萼在集合管中最为均匀。在牛眼中，房水丛中糖萼的覆盖比小梁网少，而在人眼中，施莱姆管中糖萼的覆盖比小梁网多。最有趣的是，在牛眼和人眼中，还发现糖萼填充了房水丛/施莱姆管内皮的大多数孔隙。通常未发现糖萼覆盖巨大液泡（GVs）的内膜；然而，在有可见孔隙的巨大液泡中，经常在巨大液泡的内膜上观察到糖萼。基于我们的发现以及来自血管内皮的发现，施莱姆管中的糖萼可能在剪切应力的转导以及或许在流出阻力的调节中发挥作用。
