Stem cells generated through novel method

Researchers at Hopkins have designed a new, potentially safer method of generating pluripotent stem cells from blood cells.

While scientists have been able to derive pluripotent stem cells from differentiated cells like skin, researchers are far from being able to use these cells in clinical applications.

The use of these cells continues to face many hurdles. In particular, induced pluripotent stem cells (iPSCs) can become cancerous, effectively doing more harm than good for the patient.

However, recent work by researchers at the Hopkins School of Medicine has overcome this challenge.

Members of the Cheng Laboratory, part of the Stem Cell Program in the Institute for Cell Engineering, have developed a new method of changing differentiated human cells into iPSCs by introducing certain regulatory genes.

Circular DNA containing the desired regulatory genes are directed into the cells by electroporation. In a departure from current methods, the researchers prepared their iPSCs from blood cells.

Having successfully converted the blood cells into stem cells, the team was then able to subsequently differentiate iPSCs into other types of cells. The group’s paper was published last month in the journal Cell Research.

Studies of pluripotent stem cells have focused on their potential applications in the field of regenerative medicine.

By inducing cells from any part of the body, such as skin or blood cells, to change into another type, these cells have the potential to create new tissues and organs.

Previous work in generating iPSCs relied on the use of viruses to introduce a plasmid containing the necessary genes to reprogram the cell, which involves switching on and off certain genes that are used by specific cells.

First developed in 2007, this method of turning specialized cells into stem cells has one glaring issue should these cells be applied to regenerative medicine: virus-transformed iPSCs have a tendency to form tumors. To overcome this, the group utilized a different approach.

One other common method in the realm of genetics and cell biology, electroporation, applies a small voltage across the membrane of cells to make them permeable to larger molecules by opening up larger pores. In this case, a circular piece of DNA is able to enter the cells through these openings, which close up after the cells are given time to heal.

The Cheng Laboratory utilized non-integrating plasmids, ones that remain separate from the rest of the cell’s genome, to introduce the new genes.

“Integrating plasmids will insert into human genome and may lead to unexpected results in the future, like tumor formation. On the other hand, non-integrating plasmids won’t incorporate with human genome,” writes Bin-Kwan Chou, graduate student of Cellular and Molecular Medicine at the Hopkins School of Medicine and member of the Cheng Laboratory, in an email to The News-Letter.

After a number of rounds of replication, the group found that the iPSCs eventually lost the inserted circular DNA. However, the cells maintained the physiological changes induced during transformation.

The major test for whether a cell has been successfully reprogrammed as a pluripotent stem cell is their ability to differentiate into other types of cells that may not even be remotely related in function to their original form.

According to Chou, one method is to allow the cells to cluster together and differentiate on their own accord.

“One of the simplest ways is to culture iPSCs in suspension then form embryoid body (EB). It is like a sphere and cells will differentiate to different cell types,” he writes.

Researchers also overcame several other challenges; specifically, the team streamlined the cell culturing process. Fibroblasts are the most commonly used cells in producing iPSCs, yet they require extensive culturing; establishing a cell culture of fibroblasts takes weeks after extracting them from a donor biopsy.

In contrast, the researchers were able to transform adult and umbilical blood in 14 days, presenting a time-saving benefit that can greatly reduce the lead time involved in future iPSCs studies.