Long non-coding (lncRNAs) are a large and versatile subclass of non-coding RNAs characterized by a length of more than 200 nucleotides. They can modulate gene expression transcriptional and posttranslational via various mechanisms, but the distinct molecular function of the majority of the thousands of lncRNAs is not understood so far. LncRNAs can regulate epigenetic modulations, transcription, influence the function of miRNAs and proteins as a scaffold or decoy or serve as templates for micro peptides. As lncRNAs are often disease, developmental stage or cell type specific expressed they harbor a huge potential as novel therapeutic targets.

During cardiac injury a tremendous amount of cardiomyocytes are lost and due to the limited regenerative capacity of the heart, cardiac remodeling leads to a significant reduction in cardiac function that might be life threatening. Therapeutic options are limited, therefore, novel regenerative and therapeutic strategies are needed. Besides exogenously applied cell therapy, the stimulation of the low but existing intrinsic proliferative potential of cardiomyocytes is persued. 

Through datamining of publicly available RNA sequencing data sets of regenerating and non-regenerating hearts, lncRNA Cyrano was identified as a candidate to influence cardiomyocyte proliferation. Cyrano is highly conserved in vertebrates, which is uncommon for lncRNAs, and suggests an important regulatory role across the evolution. Cyrano is highly expressed in the brain and the heart, in the latter Cyrano is enriched in cardiomyocytes compared to cardiac fibroblasts and endothelial cells. 

To investigate the role of Cyrano in cardiac regeneration and cardiomyocyte health we used knockdown models in human iPSC-derived cardiomyocytes. Initially, we demonstrated that the depletion of Cyrano does not influence the stemness and pluripotency. Consequently, Cyrano deficient human iPSCs can be efficiently differentiated via Wnt modulation into cardiomyocytes and used as an in vitro platform. Specific siRNAs were used to silence Cyrano expression. Global expression changes were analyzed by RNA sequencing in Cyrano depleted cardiomyocytes and revealed alterations in the cell cycle and cell cycle associated pathways. First functional assays identified a pro-proliferative effect of the Cyrano knockdown in cardiomyocytes: by counting the total number of cardiomyocytes we observed an increase of cell counts after silencing. Also Cyclin B1, regulating the cell cycle progression, was significantly induced after Cyrano knockdown. 

As Cyrano is mainly expressed in the cytoplasm we aimed to identify direct protein interaction partners to reveal its mode of action. Therefore, we performed a pulldown experiment with biotinylated DNA-probes. The Cyrano-bound proteins were subsequently analyzed by mass spectrometry. Thereby we identified different proteins, which are already known in the context of mitosis and cell cycle progression. Further investigations to decipher the exact molecular mechanism of Cyrano in cardiomyocytes are ongoing. 

In conclusion, the highly conserved lncRNA Cyrano represents an interesting candidate for cardiac regeneration in terms of boosting cardiomyocytes proliferation. New therapeutic options for cardiac injury are urgently needed and the stimulation of the proliferation of remaining cardiomyocytes by modulating lncRNAs might play a crucial role in future therapeutic strategies after myocardial infarction.