Research progress on the correlation between circadian rhythm and clock genes and the pathogenesis of diabetic retinopathy / 国际眼科杂志(Guoji Yanke Zazhi)

Diabetic retinopathy(DR)is the most common microvascular complication of patients with diabetes mellitus, and it has become one of the leading causes of visual impairment among working-age people worldwide. The pathogenesis of DR is complicated with multiple mechanisms. Plenty of studies have indicated that circadian rhythm and clock genes are closely related to the pathogenesis of DR. Circadian rhythm is a physiological process regulated by clock genes, which takes 24h as a cycle and is consistent with the changes of light and dark outside. Circadian rhythm regulates various physiological activities of the body. The disturbance of circadian rhythm induces DR by affecting the blood glucose level and the physiological homeostasis of the eye in patients with diabetes mellitus, and clock genes may be involved in the pathogenesis of DR by regulating oxidative stress response, inflammatory response, retinal autophagy rhythm, mitochondrial dysfunction and endothelial progenitor cell function. This paper will introduce the generation and regulation mechanism of circadian rhythm, as well as the internal circadian rhythm of retina, and further discuss the influence of circadian rhythm and clock genes on the occurrence and development of DR, aiming to provide a reference for the prevention and treatment of DR.

Inhibition of proliferation of retinal microvascular endothelial cells by pericytes through down-regulating KDR/Flk-1 in a co-culture system / 国际眼科杂志(Guoji Yanke Zazhi)

· AIM :To investigate the role of pericytes in growth of retinal microvascular endothelial cells with a co-culture system in order to understand some mechanism of angiogenesis in hypoxia induced retinal neovascular disorders.(RMECs) were isolated by a modified protocol using CD31 coated Dynabeads, and identified by immunocytochemical staining with anti-Factor Ⅷ and CD31 antibodies. Rat retinal pericytes were isolated and characterized by immunofluorescent staining with PDGFR-β; and desmin antibodies. Pericytes and RMECs were cultured in a contact co-culture system both under normoxia and hypoxia by Millicell chamber. RMECs proliferation was evaluated by MTT and cell cycle assay with flow cytometry. RT-PCR was used to detect the alteration of KDR/Flk-1 mRNA level in RMECs under normoxia or hypoxia in the co-culture system.harvested with the modified isolating method. The two cell types were identified by positive Factor Ⅷ, CD31 and PDGFR-β, desmin cytochemical staining respectively.RMECs proliferated significantly under hypoxia from 3 to 9d with a maximal rate on day 6 (24.9%, P ＜ 0.01) by MTT. In the co-culture system, the proliferation of RMECs was inhibited by pericytes. After 6d exposure to hypoxia,the fraction of S-phase RMECs number was greatly increased by 43.9% (P ＜ 0.01). In the co-culture system,RMECs proliferation was inhibited by pericytes through decreasing the fraction of S-phase cell number both under normoxia (3.6%, P＜0.05) and under hypoxia (15.1%,P＜0.01). KDR/Flk-1 mRNA level in single cultured RMECs was shown to increase approximately 1.3-fold when exposed to hypoxia. Compared with single cultured RMECs, co-culture with pericytes could decrease KDR/Flk-1 mRNA by 45.1% (P＜0.05) and 27.7% (P ＜ 0.05) under normoxia and hypoxia condition respectively.pericytes could inhibit proliferation of RMECs under both normoxia and hypoxia. The inhibition effects of pericytes maybe, at least in part, due to downregulation of KDR/Flk-1 of RMECs. These findings confirm that pericytes could be a potential inhibitor in the pathogenesis of retinal neovascularization.