PS 01-25] NINJURIN1 IS A NOVEL FACTOR TO MEDIATE VESSEL MATURATION THROUGH ENDOTHELIAL-PERICYTES INTERACTIONS

Abstract

Objective : It is known that abnormality of adventitial microvessel (vasa vasorum) is involved in vascular remodeling and progression of atherosclerosis. Although the normalization/maturation of micorvessels is attractive approach for anti-atherosclerosis, the knowledge about the mechanisms for microvascular normalization is limited. Interaction of vascular endothelial cells (ECs) and pericytes (PCs) is crucial to vascular maturation. Recently, we have reported that Ninjrin1(Ninj1) in PCs inhibit ECs growth. However, the role of Ninj1 in patho-physiological angiogenesis is still unclear . Accordingly, we examined the effects of Ninj1on the formation of neovessels using mouse hind limb ischemia (HLI) model. Design and Method: Capillary ECs and PCs were prepared from adventitia of mouse femoral artery . Cell cluster or 3D-gel assay was performed by mixture of ECs and PCs in non-adherent or Matri-gel-coated wells. Knock down of Ninj1 in cells or tissues were induced by transfection of Ninj1-SiRNA or biodegradable microspheres releasing Ninj1-siRNA. Blood flow recovery and formation of microvessels in limbs were measured by Doppler flow meter and staining with anti-CD31 or lectin-FITC. Results: Ninj1 was expressed in microvessels, both dominantly PCs and ECs. Cell cluster assay demonstrated that down-regulation of Ninj1 in PCs or ECs reduced the PC-EC interaction. When ECs were co-incubated with PCs in 3D-gel, they made matured mirovessel structure, i.e. EC-tube wrapped with PCs. Down-regulation of Ninj1 in PCs or ECs reduced inhibited the formation of this matured vessel structure. Ninj1 was expressed in microvessels within skeletal muscle tissues, and their expression was enhanced after HLI operation. When the expression of Ninj1 was inhibited by intra-muscular injection of Ninj1-siRNA leads the formation of lectin/CD31-positive functional matured microvessels and the blood flow recovery was decreased. Conclusions: Ninj1 is important for the association between PCs and ECs to form functional matured vessels. This finding would provide insights into the therapy for atherosclerosis in addition to ischemic diseases.