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Zhongxiao Wang, Chi-Hsiu Liu, Ye Sun, Samuel Burnim, Steven Meng, Zhongjie Fu, Yan Gong, Jing Chen; Pro-angiogenic Role of Amino Acid Transporter Slc38a5 in Retinal Vascular Endothelial Cells. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1532.
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An amino acid transporter, Slc38a5 (solute carrier family 38 member 5), was found down-regulated in the retinas of Lrp5-/- and Norriny/ -mice, two animal models of familial exudative vitreoretinopathy (FEVR) and Norrie disease. Patients with FEVR or Norrie disease suffer from incomplete retinal vasculature and visual loss, yet the underlying mechanisms to control retinal vascular development are not completely defined. This project aims to study the role of Slc38a5 in retinal vascular endothelial cell (EC) function.
Whole retinas (n=6) and retinal vessels (n=4) collected by laser capture microdissected (LCM) were isolated from Lrp5-/- and Norriny/- mice, and their controls (wild type (WT) and Norriny/+) at postnatal day 17. Slc38a5 mRNA and protein levels were analyzed by RT-qPCR and Western blot. SLC38A5-siRNA was transfected into human retinal microvascular endothelial cells (HRMECs), followed by cell proliferation and tubular formation assays to determine EC function, and the expression of angiogenic genes were measured by RT-qPCR(n=3). Two-tailed Student’s t-test was used for statistical analysis.
Slc38a5 mRNA levels were decreased in both whole retinas of Lrp5-/- (17.56 %±3.14 % compared to control, p=0.0085) and Norriny/- (5.26%±1.23 %, p=0.0005), and retinal vessels of Lrp5-/- (6.20 %±1.89 %, p=0.0006) and Norriny/- (1.26%±0.40%, p=0.0002). Protein levels of Slc38a5 were significantly reduced in Lrp5-/- retinas by ~4 fold, and in Norriny/- retinas by ~2 fold compared their control retinas.In HRMECs, SLC38A5-siRNA suppressed SLC38A5 expression by 86.86%±2.56%, and inhibited the angiogenic factor receptors including VEGFR2 (62.10%±1.01%, p=0.0003), FGFR2 (24.4%±1.50%, p<0.0001) and IGFR (28.5%±0.30%, p<0.0001). Knockdown of SLC38A5 significantly inhibited HRMEC proliferation by 29.91%±2.80% (p<0.0001) and tubular formation with reduction in the number of junctions (57.42±3.96/field compared to 130.9±4.19/field, p<0.0001) and vascular length (29.21±0.93 mm/field compared to 43.53±0.63 mm/field, p<0.0001).
The amino acid transporter Slc38a5 is down-regulated in retinal blood vessels in Wnt signaling deficient mice, and a novel pro-angiogenic regulator of EC function. Slc38a5 may contribute to the defective vascular development in Lrp5-/- and Norriny/- eyes through modulating the availability and homeostasis of amino acids essential for EC proliferation and growth.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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