Fibrosis is a hallmark of almost all cardiac diseases, but despite the very similar mechanism of fibroblast activation in different organs, the pathogenesis within the heart is quite complex. Chronic heart failure is characterized by cardiomyocyte hypertrophy as an initial response to cardiac overload caused for example by high blood pressure. This is accompanied by the activation of quiescent fibroblasts and their transdifferentiation into so-called myofibroblasts. The master regulator TGFβ1 (transforming growth factor beta 1) is crucially involved in this process by combining diverse cellular responses, making it the key driver of cardiac fibrosis. However, since TGFβ1 functions are not limited to the cardiovascular system, its potential as a clinically relevant therapeutic target is limited. A conceivable solution to circumvent undesirable side effects is to modulate TGFβ1 downstream targets, enabling an organ-specific inhibition of fibrosis. A promising tool to modulate downstream effectors in a more organ- and cell type-specific manner is via non-coding RNAs (ncRNAs) such as long non-coding RNAs (lncRNAs). This emerging group of non-protein coding transcripts is the most diverse class of ncRNAs. Although their important roles in development and disease are now undisputed, owing to their large number and complexity they are far from being fully understood. Here, through datamining of a publicly available large-scale RNA-sequencing data set of human cardiac fibroblasts treated with TGFβ1, we identified 15 strongly deregulated lncRNA candidates in comparison to untreated controls. In vitro responsiveness to TGFβ1 was validated in independent samples by RT-qPCR and functional assays with specific lncRNA inhibitors (GapmeRs) identified two lead candidates. LncFIB#10 and LncFIB#11 showed a remarkable induction upon fibroblast activation assuming a potential role in this process. The efficient knockdown by specific GapmeRs and heart specific expression of LncFIB#10 and LncFIB #11 was confirmed by quantitative RT-PCR. Importantly, inhibition of both lncRNAs led to a pronounced decline in the expression of common fibrosis marker genes e.g. ACTA2, POSTN, CTGF, MMP2 and COL1A1. Different in vitro assays to investigate key fibroblast phenotypes such as proliferation and migration were conducted in primary human cardiac fibroblasts from different origin. These findings indeed indicate an impaired proliferation and migration after lncRNA inhibition. Next, the GapmeRs were tested in the highly translational model of living human myocardial slices in a 4-day ex vivo culture. While parameters such as the maximum force and the relaxation time showed a trend towards improved tissue function, even more strikingly, the fibrosis markers within the whole tissue were profoundly downregulated, therefore, underpinning the potential therapeutic applicability of LncFIB#10 and LncFIB#11. 

In conclusion, inhibition of TGFβ1-induced LncFIB#10 and LncFIB#11 potently suppresses the major hallmarks of fibrosis in human cardiac fibroblasts. LncFIB#10 and LncFIB#11 represent highly interesting targets for the treatment of cardiac disease of different origin since cardiac fibrosis is such a central process in the progression to heart failure. In depth characterization of the modified gene expression profiles and interactome analyses are currently ongoing to unravel the mode of action of LncFIB#10 and LncFIB#11.