To date, there is no suitable in vitro model to study human adult cardiac cell biology. Although embryonic stem cells are able to differentiate into cardiomyocytes in vitro, the efficiency of this process is very low. Other methods to differentiate progenitor cells into beating cardiomyocytes rely on coculturing with rat neonatal cardiomyocytes, making it difficult to study human cardiomyocyte differentiation and (patho)physiology. Here we have developed a method for efficient isolation and expansion of human cardiomyocyte progenitor cells (CMPCs) from cardiac surgical waste or alternatively from fetal heart tissue. Furthermore, we provide a detailed in vitro protocol for efficient differentiation of CMPCs into cardiomyocytes with great efficiency (80-90% of differentiation). Once CMPCs are rapidly dividing ( approximately 1 month after isolation), differentiation can be achieved in 3-4 weeks.

Objective-To improve regeneration of the injured myocardium, it is necessary to enhance the intrinsic capacity of the heart to regenerate itself and/or replace the damaged tissue by cell transplantation. Cardiomyocyte progenitor cells (CMPCs) are a promising cell population, easily expanded and efficiently differentiated into beating cardiomyocytes.Recently, several studies have demonstrated that microRNAs (miRNAs) are important for stem cell maintenance and differentiation via translational repression. We hypothesize that miRNAs are also involved in proliferation/differentiation of the human CMPCs in vitro. Methods and Results-Human fetal CMPCs were isolated, cultured, and efficiently differentiated into beating cardiomyocytes. miRNA expression profiling demonstrated that muscle-specific miR-1 and miR-499 were highly upregulated in differentiated cells.

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