CircCDR1as Suppresses Bone Microvascular Endothelial Cell Activity and Angiogenesis Through Targeting miR-135b/ FIH-1 Axis

CircCDR1as decreases angiogenesis and proliferation of BMECs by sponging miR-135b and upregulate FIH-1.

Forty corticosteroid-induced ONFH patients received THA were enrolled in our study. Expressions of CircCDR1as, miR-135b, and FIH-1 were detected by qRT-PCR in affected necrosis tissue and non-affected normal tissue. Bone microvascular endothelial cells (BMEC) were isolated from six patients and treated with 0.1 mg/mL hydrocortisone to establish a GC-damaged model of BMECs. Circ CDR1as plasmid and miR-135b mimic were transfected into BMECs. BMEC proliferation was assessed using MTT assays. The migration ability of cells was detected by scratch-wound assays. Matrigel assay was performed to detect angiogenesis in vitro. Western blot assay was used to detect HIF-1α, VEGF, and FIH-1 expressions. FISH, RNA pull down, RIP, and luciferase assay were carried out to determine the interaction of CircCDR1as, miR-135b, and FIH-1.

The current study investigated the role of CircCDR1as on angiogenesis of bone microvascular endothelial cells (BMECs) isolated from non-traumatic ONFH.

CircCDR1as was upregulated(2.02 ± 0.30 vs. 1.00 ± 0.10,P < 0.001) whereas miR-135b was downregulated (0.55 ± 0.12 vs. 1.00 ± 0.10,P < 0.001) in affected tissues than in non-affected tissues. Expression of CircCDR1as and FIH-1 were negatively associated with miR-135b in affected tissues (CircCDR1as with miR-135b: r = -0.506, P < 0.001; FIH-1 with miR-135b r = -0.510, P < 0.001). Total blood tubule density was increased when CircCDR1as was silenced compared with NC (P < 0.01 vs. NC). The number of migrated BMECs were significantly increased in CircCDR1as silencing group compared with NC group (P < 0.05 vs. NC). In addition, CircCDR1as plasmids transfection increased the protein expressions of FIH-1 (P < 0.05 vs. NC) and reduced the HIF-1α as well as VEGF expression compared with NC group (P < 0.05 vs. NC). FISH, RNA pull down, RIP, and luciferase assay identified that FIH-1 was a target of miR-135b and could be modulated by CircCDR1as.