Calcific aortic valve disease-associated long noncoding RNA H19 promotes the osteogenic transition of valvular interstitial cells via the JAG1/NOTCH1 axis

Background: Calcific aortic valve disease (CAVD) is the most prevalent valvular heart disease causing tremendous suffering globally. The osteogenic differentiation of the valvular interstitial cells (VICs) is a key process in the pathogenesis of CAVD leading to calcification and stiffening. Here, we focus on the contribution of long noncoding RNA H19 in the osteogenic differentiation of VICs promoting CAVD.

Methods and results: A human lncRNA array performed in AVS patients with coronary artery disease (CAD) revealed the differential expression of lncRNA H19. For the experiments in this study, loss of function (LOF) was performed in primary VICs isolated from the aortic valves of patients with CAVD, and commercially-available VICs. Therefore, H19 expression was effectively downregulated via RNAi. Subsequent gene expression analysis via RT-qPCR revealed that the expression of calcification markers RUNX2 and BMP2, as well as the expression of the H19 downstream targets JAG1 and NOTCH1 were unchanged after the H19 knockdown alone. Then, the VICs were additionally treated with osteogenic medium (OM) and procalcifying medium (PCM) for 7 d to induce the calcification of the cells. In the OM, inorganic phosphate is generated in an alkaline phosphatase (ALPL)-dependent manner and integrated into newly formed hydroxyapatite crystals, thus promoting cellular calcification. PCM contains inorganic phosphate to form hydroxyapatite crystals and is therefore not ALPL-dependent. Gene expression analysis via RT-qPCR and protein analysis via immunofluorescence revealed that the calcification markers BMP2 and RUNX2 were upregulated after H19 knockdown and calcification induction. This indicates that H19 regulates the expression of calcification makers promoting cellular calcification. Furthermore, RT-qPCR and immunoblotting revealed the differential expression of several potential H19 downstream targets, namely JAG1, NOTCH1, and STAT3. The analysis showed that the potential downstream targets were upregulated after H19 knockdown and calcification treatment hinting at the involvement of the NOTCH1 or STAT3 pathway in the pathogenesis of CAVD. Moreover, an Alizarin Red S staining of calcified nodules revealed reduced calcification after H19 knockdown and calcification treatment for 21 d. This demonstrates that H19 also regulates a late-stage event in the cellular calcification of VICs.

Conclusion: Our study showed that H19 regulates calcification marker expression and the expression of potential downstream targets JAG1, NOTCH1, and STAT3 both in healthy and AVS patient VICs. This hints at the involvement of the H19/JAG1/NOTCH1 pathway in the calcification of VICs, which might play a critical role in the pathogenesis of CAVD. Further pathway analyses and animal experiments in a murine model of AVS should confirm the H19-regulated CAVD.