In a study led by Martin Fussenegger of ETH Zurich, stem cells extracted from the fat of a 50-year-old test subject were transformed into mature, insulin-secreting pancreatic beta cells.
Fussenegger and his colleagues isolated stem cells from the fat of a 50-year-old man and used these cells to make induced pluripotent stem cells (iPSCs). These iPSCs were then differentiated into pancreatic progenitor cells and then into insulin-secreting beta cells but means of a “genetic software” approach.
Genetic software refers to the complex synthetic network of genes required to differentiate pancreatic progenitor cells into insulin-secreting beta cells. In particular, three genes, all of which expression transcription factors, Ngn3, Pdx1, and MafA, are particularly crucial for beta cell differentiation.
Fussenegger and his team designed a a protocol that would express within these fat-based stem cells the precise concentration and combination of these transcription factors. This feature is quite important because the concentration of these factors changes during the differentiation process. For example, MafA is not present at the start of beta cells maturation, but appears on day four on the final data of maturation when its concentration rises precipitously. The concentration of Ngn3 rises and then falls and the levels of Pdx1 rise at the beginning and towards the end of maturation.
The Zurich team used ingenious genetic tools to reproduce these vicissitudes of gene expression as precisely as possible. By doing so, they were able to differentiate the iPSC-derived pancreatic progenitor cells into insulin-secreting beta cells.
This work was published in Nature Communications 7, doi:10.1038/ncomms11247.
The fact that Fussenegger’s team was able to use a synthetic gene network to form mature beta cells from adult stem cells is a genuine breakthrough. The genetic network approach also seems to work better than the traditional technique of adding various chemicals and growth factors to cultures cells. “It’s not only really hard to add just the right quantities of these components (growth factors) at just the right time, it’s also inefficient and impossible to scale up,” said Fussenegger.
This new process can successfully transform three out of four fat stem cells into beta cells. Also the beta cells made with this method have the same microscopic appearance of natural beta cells in that they contain internal granules full of insulin. They also secrete insulin in response to increased blood glucose concentrations. Unfortunately the amount of insulin made by these cells is lower than that made by natural beta cells.
Pancreatic islet transplants have been performed in diabetic patients, but such transplantations also require treatment with potent antirejection drugs that have potent side effects.
“With our beta cells, there would likely be no need for this action (administering antitransplantation drugs), since we can make them using endogenous cell material taken from the patient’s own body. This is why our work is of such interest in the treatment of diabetes,” said Fussenegger.
Fussenegger and his group have made these beta cells in the laboratory, but they have yet to transplant them into a diabetic patient. However, the success of this synthetic genetic software technology might also be useful in the reprogramming of adult cells into other types of cells that are useful for therapeutic purposes.