The role of the lncRNA MEG3 in cardiovascular disease and cardiac unloading

Aortic stenosis (AS), representing one of the most common valve diseases, is accompanied by progressive left ventricular remodeling transitioning towards heart failure (HF). The implantation of a transcatheter aortic valve (TAVI) has emerged as the preferred treatment strategy for patients with severe AS leading to improved cardiac function. However, a notable number of patients are re-admitted to hospital due to the progression to HF, which is mainly associated with cardiac fibrosis (CF). CF is characterized as excessive extracellular matrix deposition and mainly driven by the activation of cardiac fibroblasts, leading to their transdifferentiation into contractile cells, referred to as myofibroblasts. Despite numerous improvements in pharmacological treatment strategies, the prospects of cure for patients undergoing TAVI remain poor, indicating the urgent need for innovative therapeutic strategies specifically targeting CF. However, for testing such therapies, we first needed to establish an in vivo model resembling AS and TAVI. To this end, we performed an 8-weeks and 12-weeks in vivo experiment in which first pressure-overload induced cardiac hypertrophy was induced by transverse aortic constriction (TAC) surgery. After 4-weeks or 6-weeks the previously performed TAC was removed simulating TAVI (referred to as debanding, DeTAC). Echocardiographic and histological assessments revealed only partial recovery of LV mass, LV wall thickness and ejection fraction in the 12-weeks approach, indicating incomplete reverse remodeling in this model. Moreover, cardiomyocyte hypertrophy as well as increased heart weight was still present in the DeTAC group. Based on these results the 12-weeks experiment proved to be a suitable model mimicking TAVI-induced cardiac unloading and therefore represents a promising tool for the investigation of adjuvants supporting cardiac recovery.

Long non-coding RNAs (lncRNAs) represent promising therapeutic targets as they have already been proven to be involved in the progression of various diseases, including cardiovascular diseases. The well-conserved lncRNA Meg3 is enriched in cardiac fibroblasts and dysregulated in HF models. In preceding studies, the role of Meg3 in the development of cardiac fibrosis was validated in vitro an in vivo. For proof-of-concept, we combined our newly established 12-weeks DeTAC model with an adjuvant therapy inducing the inhibition of the lncRNA Meg3. Indeed, anti-Meg3 therapy, enhanced cardiac recovery as indicated by a significantly increased stroke volume. The anti-fibrotic effect of MEG3 is conserved in human as revealed by performing knockdown experiments in human living myocardial slices (LMS) and human cardiac fibroblasts (HCFs) combined with pro-fibrotic transforming growth factor ß (TGFß) stimulation, which further strengthens the translational potential. MEG3 inhibition significantly reduced expression levels of fibrosis-related genes. To further unravel the underlying cellular and molecular mechanisms, mRNA Sequencing and subsequent KEGG pathway analysis of HCFs treated with MEG3 GapmeR and TGFß was performed and revealed an association of MEG3 with fibrosis-related pathways. In summary, our results highlight anti-Meg3 therapy as an effective anti-fibrotic treatment and as a promising adjuvant treatment strategy in the context of cardiac unloading therapy.