Jasmine Peng

Introduction: Retinopathy of prematurity (ROP) is a spectrum of retinal pathologies, ranging from spontaneous regression to retinal detachment, and is a leading cause of childhood blindness worldwide¹. A defining characteristic of ROP is neovascularization, a pathological over-vascularization of the retina mostly caused by changes in metabolism and oxygen availability in preterm infants^2,3. Because current therapeutics are extremely invasive or do not produce lasting effects^1,4,5,6, the recent paradigm shift has been toward exploring gene expression regulators of angiogenesis, specifically long noncoding RNAs (lncRNAs). Of the known lncRNAs, metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is one conserved across many organisms and shows high expressivity in vascular endothelial cells, indicating its potential role in regulating angiogenesis. Methods: Oxygen-induced retinopathy (OIR) mouse models were created by placing mice in 75% O2 chambers for 5 days^7,8. MALAT1 silencing was conducted by small interfering RNA (siRNA) transfection, and MALAT1 expression was measured with RT-qPCR^7,8. To test the effect of Quercetin, HUVEC cells were pretreated with at IC50 for 24, 48, and 72 hours⁹. Total RNA was extracted, and cDNA synthesized. RT-PCR was conducted to determine MALAT1 expression⁹. Results: MALAT1 was shown to regulate endothelial cell proliferation and vessel outgrowth, and MALAT1 expression was increased during hyperoxia¹⁰. Under-expression of MALAT1 lead to decreased angiogenesis^10,11. Three downstream effectors were shown to be upregulated because of increased MALAT1 expression: VEGF¹¹, EGR1⁸, and HIF-1α¹². Furthermore, VEGF levels were shown to be overexpressed with increased levels of EGR1, indicating that VEGF is likely a downstream effector of EGR1¹³. HIF-1α has been shown to induce upregulation of VEGF, and this system is highly active in establishing microvasculature¹³. Quercetin treatment had an anti-angiogenic effect on HUVEC cells that can at least partially be attributed to the downregulation of MALAT1⁹. Significance: LncRNA research is a very new field, and most lncRNAs exhibit a multitude of functions. Thus, understanding the entire mechanistic landscape of MALAT1 is challenging and complicated. This project, however, provides more insight on a potentially less invasive and more effective therapeutic target for ROP. During initial vascular development, expression of angiogenic factors is highly active during the hypoxic conditions in utero^14,15. Following vascular remodeling, hyperoxic conditions induce overexpression of MALAT1, leading neovascularization. Thus, there has been conflicting literature describing the oxygen conditions that lead to hyper vs hypo activity of VEGF, EGR1, and HIF-1α. More research must be conducted on the specifics of MALAT1 effector expression during the entire retinal vascularization timeline.

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