As any sports coach, hopeful lottery winner, or child in a candy store will tell you, an effective selection strategy is vitally important to a successful outcome. Selection is also an important concept for scientists and clinicians hoping to take advantage of the ability that human pluripotent stem cells (hPSCs) have to differentiate into multiple useful cell types. Each month brings new means to derive specific cell types from human pluripotent stem cells, but the end product generally represents a non-purified heterogeneous cell population. While transplanting some “polluting” cells may be harmless, some may inhibit cellular function or even promote tumorigenesis.
So how do we purify these cells? Cell-surface markers are the number one choice, but this approach suffers from a lack of known markers or a lack of specificity. Many studies have assessed other selection techniques with varying success, but now researchers from the laboratories of Hirohide Saito and Yoshinori Yoshida (CiRA, Kyoto University, Japan) think they have come up with the best strategy yet – synthetic miRNA-responsive “switches”.
These miRNA switches are composed of a miRNA recognition sequence controlling the expression of a desired gene (e.g. a fluorescent or pro-apoptotic protein) and using these synthetic switches the researchers effectively selected highly pure cell populations.
- miR-1-, miR-208a-, and miR-499a-5p-switches mediated a cardiomyocyte specific inhibition of a fluorescent signal to allow the selection of a high purity human pluripotent stem cell-derived cardiomyocyte population.
- miR-1- and miR-208a-switches expressing the pro-apoptotic Bim gene promoted the death of non-cardiomyocyte cells and gave a pure cardiomyocyte population without the requirement for cell sorting.
- Excitingly, miRNA switch-purified cardiomyocytes engrafted and survived in mouse hearts, and did not form tumors.
- Specific miRNA switches efficiently purified endothelial cells (miR-126), hepatocytes (miR-122-5p) and Insulin-producing cells (miR-375) differentiated from human pluripotent stem cell, and hence demonstrates the generally applicability of this approach.
Overall, this strategy resulted in higher purification levels than standard methods and represents a safer choice compared to other recently devised techniques due to the non-integrative nature of the miRNA switches. Consequently, the widespread application of this methodology could allow for the clinically application of human pluripotent stem cell-derived cells in future regenerative medicine applications.
To read more about this new technological advance, “switch” over to Cell Stem Cell, May 2015.