A Feedforward Regulatory Loop between HuR and Long Noncoding RNA MALAT1 Promotes Osteogenic Differentiation of Human Aortic Valve Interstitial Cells

Abstract

Objective: Aortic valve calcification (AVC) is common in aging populations without effective pharmacological interventions. Our previous in vitro data revealed a critical role for long non-coding RNA (lncRNA) MALAT1 as a positive regulator of osteogenic differentiation in AVC pathogenesis. The current study sought to determine whether MALAT1 deficiency could prevent AVC progression in vivo and the mechanism by which MALAT1 is regulated in AVC. Approach and Results: AVC was evaluated in Apoe-/- mice (n = 10) or in mice with dual deficiencies of Apoe and MALAT1 (Apoe-/-MALAT1-/-, n = 10) fed a Western diet for 24 weeks. Genetic ablation of MALAT1 attenuated pro-calcification signaling activation, and valvular calcification in the leaflets of Apoe-/- mice. In cultured human aortic valvular interstitial cells (VICs), we found RNA-binding protein (RBP) human antigen R (HuR) enhanced the mRNA stability of MALAT1 and thus promoted MALAT1 expression. Moreover, HuR was significantly upregulated in mouse and human calcific aortic valves and VICs following osteogenic induction. HuR partly relied on MALAT1 to positively regulate osteogenic differentiation of VICs. Luciferase reporter assays validated HuR as the direct target of miR-191-3p. Importantly, MALAT1 positively regulated the expression of HuR through sponging miR-191-3p. Conclusions: This study demonstrates the existence of a regulatory loop in which the expression of MALAT1 and HuR is reciprocally regulated during osteogenic differentiation of VICs. Our findings provide novel mechanistic insights into a critical role of HuR in the AVC progression, and shed new light on RBPs-directed diagnostics and therapeutics in AVC. Funding: This work was supported by the National Natural Science Foundation of China (No. 81500300) and the National Key Research and Development Program of China (No. 2016YFA0101100). Declaration of Interest: None. Ethical Approval: All animal experimental protocols complied with the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH Publication No. 85-23, revised 1996). All animal protocols were approved by the Institutional Animal Research Committee of Tongji Medical College. The protocol complied with the Declaration of Helsinki, was approved by the Ethic Board of Tongji Medical College of Huazhong University of Science and Technology. Written informed consents were obtained before surgeries from all patients.