Detection of lymphatic biomarker D2-40 in human trabecular meshwork

Abstract

Background The pathological basis of human primary open angle glaucoma mainly is the degeneration of trabecular meshwork and Schlemm canal.As the outflow pathway of aqueous humor, the tissue origin and characteristics of trabecular meshwork remain less clear.Studying the characteristics of trabecular meshwork may contribute a new thought to the treatment of primary open angle glaucoma. Objective This study was to explore the histological property of trabecular meshwork by detecting the expression of D2-40, a lymphatic biomarker, and CD31, CD34 and smooth muscle actin (SMA), some vascular endothelial biomarkers. Methods Twenty specimens of adult eyeballs were collected from Zhongshan Ophthalmic Center of Sun Yat-sen University, including 10 eyeballs from accident death donors, 3 enucleated eyeballs due to posterior segment of choroidal malignant melanoma and 7 orbital exenterated eyeballs.The series ocular meridian sections with the thickness of 4 μm were prepared for the haematoxylin-eosin staining.Immunohistochemistry was employed to detect the expression of D2-40, CD31, CD34 and SMA in trabecular meshwork and Schlemm canal. Results Intact structure of chamber angle was observed under the optical microscope by haematoxylin-eosin staining.Human trabecular meshwork tissue was presented with mesh-like structure, while Schlemm canal showed the lumen structure.No abnormal substance and periphery synechia were found.D2-40 was strongly expressed in the trabecular meshwork endothelial cells with staining score for 3 points, but CD31, CD34 and SMA were negatively expressed.In contrast, CD31, CD34 and SMA rather than D2-40 were positively expressed in the Schlemm canal.In addition, CD31 and CD34 were also positively expressed in the vascular endothelial cells around the trabecular meshwork. Conclusions The trabecular meshwork expresses lymphatic biomarker rather than vascular biomarkers.This result indicates that trabecular meshwork of human eyes is lymphatic vessel-like tissue. Key words: Trabecular meshwork; Biological markers/analysis; Anterior chamber angle/anatomy & histology; Humans; Lymphatic system; Immunohistochemistry; Schlemm canal