1Medizinische Hochschule Hannover Institut für Molekulare und Translationale Therapiestrategien, OE-8886 Hannover, Deutschland
Cardiovascular diseases are the leading cause of death worldwide. Considering that current treatments are mostly of symptomatic and supportive nature there is a great need for new therapeutics. In the last decade, non-coding RNAs have emerged as potential new therapeutic targets. Our group identified the long non-coding RNA Foxo6os as upregulated in the developing heart and downregulated in the diseased heart by genome-wide RNA deep sequencing. We found that Foxo6os is highly expressed in the heart compared to other organs and within the heart, it is enriched in cardiomyocytes as compared to endothelial cells and fibroblasts. Importantly, Foxo6os expression could also be modulated in vitro. Overexpression of Foxo6os is beneficial for cardiomyocyte survival whereas the knockdown induces apoptosis. Taken together, these experiments show that Foxo6os is not only regulated during different (patho) physiological conditions but also has functional roles in cardiomyocytes as shown in gain- and loss-of-function experiments.
Aiming at the translation of our findings to the human setting, we evaluated the conservation across species and found the lncRNA AC093151.2 as a potentially locus-conserved human transcript of Foxo6os. The transcript is highly enriched in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) compared to hiPSC and human cardiac fibroblasts. Importantly, similar to Foxo6os expression, AC093151.2 expression was downregulated in hiPSC-CM disease models such as ISO/PE-induced hypertrophy and hypoxic conditions.
Based on our very supportive in vitro data, we generated a Foxo6os knockout mouse using the Cre/LoxP system to generate a Foxo6os-/- mouse line. By performing myocardial infarction (MI) surgery on these mice, we found that the knockout mice tended to have exacerbated fibrosis and show worse cardiac function.
To further evaluate the therapeutic potential in a human disease setting, we overexpressed the human Foxo6os in living myocardial slices (LMS) and evaluated the contractile function. We observed that after the treatment of the hypertrophic LMS with adeno-associated virus (AAV9) overexpressing the human Foxo6os, improved contractile function. We are currently testing the therapeutic potential in vivo. Therefore, we are overexpressing Foxo6os using AAV9 directly after myocardial infarction surgery in mice.
In conclusion, our findings suggest an important functional role of Foxo6os in heart diseases. Additionally, Foxo6os gene therapy suggest a promising therapeutic potential. These data warrant further validation of the therapeutic potential in vivo and elucidation of the underlying mechanism.