Researchers mass-producing stem cells to satisfy the demands of regenerative medicine

Steve Oh had been growing stem cells by conventional means at the A*STAR Bioprocessing Technology Institute (BTI) for seven years, when in 2008 his colleague Shaul Reuveny proposed an idea for speeding up the process.

Instead of culturing the cells on round, flat Petri dishes, he could try growing them on tiny polystyrene beads known as microcarriers floating in a nutritional brew, suggested Reuveny, a visiting scientist at the BTI. This technique had been used for decades to mass-produce virus-infected cells for the vaccine industry, which Reuveny was very familiar with.

The average Petri dish fits fewer than 100,000 cells, a miniscule amount when stacked against the 2 billion muscle cells that make up the heart or the 100 billion red blood cells needed to fill a bag of blood. The approach Reuveny suggested potentially could produce cells in much vaster numbers to make them more practical for therapy.

Oh's Stem Cell Group first tried the approach on human embryonic stem cells. These are found in the early embryo and have the potential to mature into any type of cell in the body, a state known as pluripotency. For months, they struggled to develop a coating that would make the stem cells stick to the microcarriers, and to formulate a solution that contained the right mixture of nutrients for the cells to grow. "Without Reuveny's know-how, we probably would have failed," says Oh.

The group has spent the last six years refining their processes to produce even more cells using cheaper materials and fewer steps. "We are easily achieving three times higher cell densities than the Petri dish approach," says Oh. "In some cases, by modifying the feeding strategy, we can get six times more cell densities, and we could probably reach ten with a bit of work."