ESCs provide a vital and renewable cell source capable of repairing or replacing damaged tissues from degenerative diseases like Alzheimer's disease, stroke, and myocardial infarction (MI), potentially revolutionizing medicine(Duncan and Valenzuela 2017; Hao et al. 2014; Larijani et al. 2012). Myocardial infarction can result in myocardial necrosis and a poor prognosis. ESCs’ transplantation after myocardial infarction can promote cardiac repair and enhancement of cardiac functions by maintaining ESCs’ survival and migration, enhancing their differentiation toward cardiomyocytes and inducing angiogenesis(Pal 2009; Zhang et al. 2018). Thus, it is necessary to study the mechanism of ESCs’ differentiation further. This study investigated the effects of miR-322 and celf1 on the differentiation of ESCs towards cardiomyocytes.
The development of the heart involves a succession of cellular migrations, fusions, and specific differentiation. Several key regulatory factors, such as NKX2.5, Tbx5, and α-MHC, play a vital role in cardiac development(Fujikura et al. 2002; Zhao et al. 2008). ESCs can generate several fully differentiated cells in the body, including cardiomyocytes, which can decrease ischemia myocardium and improve heart function(Lee et al. 2017; Ng et al. 2010). Various studies have concluded that miRNA regulates the direction of ESCs’ differentiation by controlling a large number of genes by post-transcriptional regulation(Cordes et al. 2009; Yang et al. 2011). Previous studies have indicated that miR-322 plays a protective function in MI and regulates ESCs’ differentiation(Dong et al. 2019; Youn et al. 2019). Meanwhile, this study found that the overexpression of miR-322 had little effect on pluripotency (Oct4 and Sox2) but could significantly increase the mRNA expression of cardiomyocyte markers Nkx2-5, MLC2V, and α-MHC. The results indicated that miR-322 could promote the differentiation of ESCs towards cardiomyocytes, denoting that it might enhance the capability of such differentiation after engrafting in areas of myocardial damage.
CELF, also known as CUGBP, is an RNA-binding protein. The members of this protein family regulate pre-mRNA alternative splicing and may also be involved in mRNA editing and translation(Barreau et al. 2006; Good et al. 2000; Ladd et al. 2001). As a member of the CELF family, celf1 can regulate embryonic development and cardiomyocyte maturation, adipose tissue, and skeletal muscle differentiation(Blech-Hermoni et al. 2016; Marquis et al. 2006). Celf1 abnormalities can be the pathogenesis of various diseases(Blech-Hermoni et al. 2013; Dasgupta and Ladd 2012). Previous studies have revealed that celf1 can mediate connexin 43 mRNA degradation in dilated cardiomyopathy(Chang et al. 2017). In addition, celf1 can contribute to dilated cardiomyopathy via regulating gap junction integrity(Jeffrey and Sucharov 2018). Furthermore, putative miR-322/-503 target sites on the Celf1 3’UTR have been predicted through using several computational programs such as Miranda and TargetScan(Sarkar et al. 2010). Experiments were performed in vitro to investigate the role of celf1 in ESCs’ differentiation towards cardiomyocytes. They found that the overexpression of celf1 had little effect on pluripotency (Oct4 and Sox2) but could significantly increase the mRNA expression of Nkx2-5, MLC2V, and α-MHC. Moreover, celf1 could inhibit ESCs’ differentiation towards cardiomyocytes. The results further indicated that miR-322 could inhibit celf1 protein expression, signifying that celf1 could be a target of miR-322.
This study proved that miR-322 might promote the differentiation of ESCs into cardiomyocytes via regulating celf1. Furthermore, its results suggested that overexpression of miR-322 might enhance the protective role of ESCs’ transplantation after myocardial infarction. Thus, this study generally provides theoretical guidance for the clinical application of ESCs in myocardial infarction treatment. Nevertheless, more experiments still need to be designed to support this study further.