Su Jung Hwang^1,2, Bum Ju Ahn³, Min-Wook Shin³, Ye-Seul Song¹, Youngbin Choi¹, Goo Taeg Oh⁴, Kyu-Won Kim³ and Hyo-Jong Lee^1,*

¹School of Pharmacy, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, South Korea. ²College of Pharmacy, Inje University, 607 Obang-dong, Gimhae, Gyungnam 621-749, South Korea. ³College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 08826, South Korea. ⁴Immune and Vascular Cell Network Research Center, National Creative Initiatives, Department of Life Sciences, Ewha Womans University, Seoul 03760, South Korea.

^*Corresponding author.

Ninjurin1 (Ninj1), an adhesion molecule, regulates macrophage function in hyaloid regression, multiple sclerosis, and atherosclerosis. However, its biological relevance and the mechanism underlying its function in vascular network integrity have not been studied. In this study, we investigated the role of Ninj1 in physiological (postnatal vessel formation) and pathological (endotoxin-mediated inflammation and diabetes) conditions and developed a strategy to regulate Ninj1 using specific micro (mi)RNAs under pathological conditions. Ninj1-deficient mice exhibited decreased hyaloid regression, tip cell formation, retinal vascularized area, recruitment of macrophages, and endothelial apoptosis during postnatal development, resulting in delayed formation of the vascular network. Five putative miRNAs targeting Ninj1 were selected using the miRanda algorithm and comparison of expression patterns. Among them, miR-125a-5p showed a profound inhibitory effect on Ninj1 expression, and miR-125a-5p mimic suppressed the cell-to-cell and cell-to-matrix adhesion of macrophages and expression of pro-inflammatory factors mediated by Ninj1. Furthermore, miR-125a-5p mimic inhibited the recruitment of macrophages into inflamed retinas in endotoxin-induced inflammation and streptozotocin-induced diabetes in vivo. In particular, miR-125a-5p mimic significantly attenuated vascular leakage in diabetic retinopathy. Taken together, these findings suggest that Ninj1 plays a pivotal role in macrophage-mediated vascular integrity and that miR-125a-5p acts as a novel regulator of Ninj1 in the management of inflammatory diseases and diabetic retinopathy.