Currently, induced pluripotent stem cells are created by introducing four defined genes to an adult cell. The genes reprogram the adult cell into a stem cell, which can differentiate into many different types of the cells in the body. Typically, the four genes introduced are Oct4, Sox2, Klf4 and c-Myc, a combination known as OSKM.
New Strategy to Improve Development of Induced Pluripotent Stem Cells
The researchers found that by fusing two proteins – a master stem cell regulator (Oct4) and a fragment of a muscle cell inducer (MyoD) – they succeeded in “powering up” the stem cell regulator, which can dramatically improve the efficiency and purity of reprogrammed induced pluripotent stem cells.
“Our team discovered that by fusing a fragment of the powerful protein MyoD to Oct4 we could create a ‘super gene’ which would improve the induced pluripotent stem reprogramming process,” said senior author Dr. Nobuaki Kikyo. “The result is what we termed M3O, or ‘super Oct4′ – a gene that improves the creation of induced pluripotent stem cells in a number of ways. In the process we shed new light on the mechanism of making induced pluripotent stem cells.”
The challenge with the previous method – OSKM – has been that very few cells actually become induced pluripotent stem cells during reprogramming. In fact, the rates currently stand at about 0.1 percent. Another issue has been tumor development. Because some of the reprogramming genes introduced are oncogenes, the risk of developing tumors grows.
The research led to a new gene model that minimizes such complications while amplifying the benefits of the process.
According to Kikyo, the new gene model – called M3O-SKM – improves induced pluripotent stem development by:
- Increasing efficiency. The efficiency of making mouse and human induced pluripotent stem cells was increased over 50-fold compared with the standard OSKM combination.
- Increasing purity. The purity of the induced pluripotent stem cells was much higher with the M3O-SKM gene introduction (98% of the colonies) compared with OSKM (5%).
- Facilitating the reprogramming. induced pluripotent stem cell colonies appeared in around five days with M3O-SKM, in contrast to around two weeks with OSKM.
- Decreasing the potential for tumor formation. M3O achieved high efficiency of making induced pluripotent stem cells without c-Myc, an oncogene that can potentially lead to tumor formation.
In addition, human induced pluripotent stem cells usually require co-culture with feeder cells typically prepared from mouse cells, obviously creating a problem when the cells are destined for human transplantation. The M3O model did not require such feeder cells, greatly simplifying the process.
According to senior author Kikyo, this new strategy will dramatically speed up the process of making patient-specific induced pluripotent stem cells, which makes clinical applications via transplantation of the cells more feasible to treat many diseases incurable otherwise.
Reference for: New Strategy to Improve Development of Induced Pluripotent Stem Cells
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