AUTHOR=Zhao Hongwei , Shi Yuanyuan , Qiu Changyu , Zhao Jun , Gong Yubo , Nie Chuang , Wu Bin , Yang Yanyan , Wang Fei , Luo Ling 

TITLE=Effects of Simulated Microgravity on Ultrastructure and Apoptosis of Choroidal Vascular Endothelial Cells

JOURNAL=Frontiers in Physiology

VOLUME=Volume 11 - 2020

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.577325

DOI=10.3389/fphys.2020.577325

ISSN=1664-042X

ABSTRACT=Background: It was confirmed that simulated microgravity (SMG) led to ultrastructural alterations and apoptosis in many types of microvascular endothelial cells. However, whether SMG would also affect choroidal vascular endothelial cells (CVECs) remains unknown. This study was designed to investigate effects of SMG on ultrastructure and apoptosis of CVECs. 
Methods: The rotary cell culture system (RCCS) was utilized to simulate microgravity condition. Human CVECs were cultured under normal gravity (NG) or SMG condition for 3 days. The ultrastructure was viewed under transmission electron microscopy, and the organization of F-actin was observed by immunofluorescence staining. Besides, the apoptosis percentage was calculated using flow cytometry. Moreover, the mRNA and protein expression of BAX, Bcl-2, Caspase3, and Cytochrome C, p-AKT, p-PI3K were detected with quantitative PCR and Western blot at different exposure time.
Results: In SMG group, CVECs presented with shrunk cell body, chromatin condensation and margination, mitochondria vacuolization, and apoptotic bodies. The amount of F-actin decreased and the filaments of F-actin were sparse or even partly discontinuous after cultivation under SMG for 72h. The proportions of apoptotic CVECs in SMG groups at 24h and 72h were significantly higher than those in the NG group (P<0.001). The mRNA and protein expression of Bax, Caspase3, Cytochrome C of CVECs in SMG groups at 24h and 72h significantly increased than those of the NG group, respectively (P<0.001). Besides, the alterations of p-AKT, p-PI3K protein expression possessed similar trends. On the contrary, the mRNA and protein expression of Bcl-2 in CVECs under SMG at 24h and 72h were significantly less than that of the NG group, respectively (P<0.001).
Conclusion: SMG condition can lead to the alterations of F-actin structure and apoptosis of CVECs. Bcl-2 apoptosis pathway and PI3K/AKT pathway may participate in the damage of CVECs caused by SMG.