Beating cardiomyocyte  (Source: Paul Burridge)
Researchers say the new method is almost 100 percent efficient

Researchers from the Johns Hopkins Institute for Cell Engineering and the Kimmel Cancer Center have developed a new, nearly 100 percent efficient technique for turning blood cells into beating heart cells. 

Elias Zambidis, M.D., Ph.D., study leader and assistant professor of oncology and pediatrics at the Johns Hopkins Institute for Cell Engineering and the Kimmel Cancer Center, along with Paul Burridge, Ph.D., a postdoctoral scientist at Johns Hopkins, and a team of researchers, developed the method for creating simple and virus-free beating heart cells. 

Previous studies used viruses to send genes into cells, which then turned them into stem cells. The problem with this method is that viruses can mutate genes, which may introduce cancer in new cells. 

But now, Zambidis and Burridge have developed a new method for delivering genes to cells without the use of viruses. Instead, the new technique involves the use of plasmids, which are rings of DNA that replicate inside cells and then degrade over time. In addition, the new technique is inexpensive, easy and almost 100 percent efficient. 

They were able to do this by studying approximately 30 papers on other techniques that create cardiac cells. They also drew charts of over 48 different variables that play a role in creating cardiac cells, like enzymes, growth factors buffers and timing. Making sure the stem cells are supplied with a mixture of growth factors, nutrients and the right environmental conditions is a large part of the process. This mixture can be different from laboratory to laboratory, and now, after testing hundreds of different combinations of these variables, Zambidis and Burridge have found four to nine vital recipes for each stage of cardiac development.

"We have recently optimized the conditions for complete removal of the fetal bovine serum from one brief step of the procedure - it's made from an animal product and could introduce unwanted viruses," said Zambidis. 

Researchers then experimented with the new growth medium by coupling it with cord blood stem cells and a plasmid that sends seven genes into the stem cells. An electric pulse was sent to the cells as well, which created tiny holes in the stem cells allowing the plasmids to enter. The plasmids then cause the cell to slip into a "primitive" state, and can change into different cells. These are called induced pluripotent stem cells (iPSC). From there, the iPSCs were supplied with the new mixture, which is called the "universal cardiac differentiation system." the cells were then placed in containers where oxygen was reduced to a quarter of "ordinary atmospheric levels," and a chemical called PVA was added to link the cells together. In a matter of nine days, the iPSCs became tiny beating cardiac cells.   

According to results, the mixture worked consistently for 11 different stem cell lines. In each of the 11 cell lines, each plate of cells had around 94.5 percent beating heart cells. It also worked for embryonic stem cells and adult blood stem cells. 

"Most scientists get 10 percent efficiency for iPSC lines if they're lucky," said Zambidis. 

In addition to efficiency, another benefit was that the cost to make the universal cardiac differentiation system was one-tenth cheaper than traditional mixtures used for stem cells. 

The universal cardiac differentiation system took two years to make, and recently, the team created similar methods for neural, vascular and retinal cells. 

This study was published in PLoS One.

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