In this regard, such natomical structure and spatial distribution characteristics in ONH astrocytes may provide certain advantages in vascular regulation.Īstrocytes, which link neurons to blood and provide structural and physiological support to optic nerve head axons, are essential for the maintenance of ocular tissue homeostasis ( 13, 14). The endfoot processes of astrocytes completely envelop all retinal blood vessels ( 12). Morover, astrocytes have an intimate structural relationship with the retinal microvasculature. Astrocytes in the diffusely vascularized retina have been posited to be derived from the optic nerve ( 11). Additionally, the presence and distribution of retinal astrocytes have been shown to possess high consistency with the presence and distribution of retinal blood vessels, while only vascularized retina contain astrocytes ( 10). The arterial wall near the optic disk is composed of five to seven layers of smooth muscle cells. Retinal arteries differ from arteries of the same size in other organs as they have an unusually developed smooth muscle layer and lack an internal elastic lamina. Accordingly, certain structural similarities may indicate that ONH astrocytes play a similar role in the eye. The optic nerve is considered to be a continuation of the central nervous system. Astrocytes, in addition to these supportive roles, may play a central role in many other aspects of brain function, including neuronal signal regulation and cerebrovascular regulation ( 8, 9). These findings indicated the possible involvement of glial cells in the autoregulation of ONH blood flow ( 7). Recent studies have found that the perfusion pressure of ONH decreased significantly when intraocular pressure was artificially elevated in gliotoxic compound treated rabbits, whereas blood flow was maintained in control eyes. Glial cells have been shown to contribute to basal retinal vascular tone and modify the dynamic response of arteries and veins toward changes in perfusion pressure ( 6). Studies have also suggested the presence of paracrine and/or autocrine signaling within the LC( 3– 5). Two distinct cell types are believed to serve the LC: ONH astrocytes and LC cells ( 1, 2). The LC region is composed of glial columns and connective tissue plates.

The lamina cribrosa (LC) of the optic nerve head (ONH) serve as the definite site in which the central retinal artery and vein (CRA and CRV) pass through to enter or leave the eye. The contractile response of VSMCs in the co-culture system provided direct evidence for the involvement of ONH astrocytes in vascular associated effects, which may signify a potentially novel direction for future research. In ONH astrocytes and VSMCs co-culture system, the length-to-width ratio of VSMCs was shown to significantly increase on days 3 and 7 in hyperoxia compared with normoxia.Ĭonclusions: There is an abundance of expression of vasoactive substances within LC tissue and ONH astrocytes. ET-1 and RAS elements were observed to be upregulated, whereas NOS was downregulated.

Moreover, hyperoxia inhibited NO production both in vivo and in vitro. Retinal vessel diameter was found obviously decreased following hyperoxia exposure. Results: Endothelin-1 (ET-1), nitric oxide synthase (NOS) and renin-angiotensin system (RAS) were detected in both LC tissue and ONH astrocytes. Morphological parameters of VSMCs were finally analyzed in order to evaluate cell contraction. ONH astrocytes and vascular smooth muscle cells (VSMCs) were then incubated in a direct co-culture manner. The variations of protein and gene expression associated with vasoactive substances were subsequently tested. Hyperoxia exposure was carried out both in vivo and in vitro, after which nitric oxide (NO) levels in LC tissue and cell supernatant were detected. Immunofluorescent staining was then used to detect the expression of vasoactive substances. Methods: LC tissue sections and primary cultured ONH astrocytes were obtained from adult Sprague-Dawley (SD) rats. Purpose: This study was conducted in order to test the expression of vasoactive substances within rat lamina cribrosa (LC) and optic nerve head (ONH) astrocytes, so as to investigate the role and potential mechanism of ONH astrocytes in vascular associated effects. 2State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.1Department of Ophthalmology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.Yanmin Dong 1,2 Yue Fu 2 Xiaobing Qian 2 Leilei Lin 2 Yongguang Yuan 2 Yujie Li 2 Wanwen Shao 2 Qianying Gao 2 *

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