Differentiating cardiomyocytes from human pluripotent stem cells is a promising next chapter in the fight against cardiovascular disease, which is the leading cause of death globally. Researchers from Kyoto University (Kyoto, Japan) and the University of Tokyo (Chiba, Japan) describe a method of purifying differentiated target cells using synthetic miRNA switches that isolate desired cell types safely and efficiently without affecting cellular properties.
Potential uses of cardiomyocytes derived from pluripotent progenitors span from transplantation to testing an individual’s susceptibility to a drug to truly personalize treatment. However, at present, differentiated cells are often a mix of heterogeneous populations. Cardiomyocytes lack specific cell surface markers, which makes their identification difficult. This study describes a method of effectively purifying such cells. The team hypothesized that using a microRNA (miRNA)-responsive modified mRNA (modRNA) switch could surpass previous attempts at differentiated cell purification in terms of selectivity, efficiency and safety.
The method involved detecting cells based on their miRNA activities compared with non-target cells. Following a screen for cardiomyocyte-specific miRNAs, miR-1, miR-208a and miR-499a-5p were found to be actively expressed in the stem cell-derived cardiomyocytes, allowing efficient purification. To avoid genome integration, modRNAs that target tissue-specific miRNAs were used to reprogram somatic cells into human pluripotent stem cells.
Not only were the switches tissue specific, but they also induced apoptosis in non-target cells, leaving only the purified cardiomyocytes, thus bypassing the need for cell sorting. This autonomous cell death and the high yield of recovered target cells suggest that large-scale clinical purification may one day be possible. Other cell types, such as hepatocytes and pancreatic beta cells were also efficiently purified, suggesting that this technique could have far reaching scope.
This method demonstrated approximately 90% purification of cardiomyocytes and was described by the authors are being more effective than existing methods. The transplantation potential of the purified cardiomyocytes was tested in a mouse model of acute myocardial infarction. The cells engrafted and survived in the heart, without tumorigenesis, which are positive steps towards restoration of heart function.
The authors highlight the simplicity of transfecting the miRNA switch into the progenitors and the use of specific miRNAs to identify target cells. Hopes are that advances in RNA transduction technology could result in an even more efficient miRNA switch method. The team see a bright future for this ‘safe’ and ‘versatile’ tool in both basic and clinical stem cell research.
Source: Miki K, Endo K, Takahashi S et al. Efficient Detection and Purification of Cell Populations Using Synthetic MicroRNA Switches. Cell Stem Cell doi: http://dx.doi.org/10.1016/j.stem.2015.04.005