Overview

The ability of induced pluripotent stem cells or iPSCs to differentiate into most body cell types has stimulated repair and regenerative medicine research over the past few decades. iPSC-derived blood cells, hepatocytes, beta islet cells, cardiomyocytes, neurons, and other cell types can repair injuries or regenerate damaged tissue in diseases such as diabetes and neurodegenerative disorders.

iPSCs have been successfully used to treat age-related macular degeneration (AMD), a form of blindness. This disorder is caused by the loss of retinal pigment epithelium (RPE) due to aging. Skin cells from an AMD patient were isolated and reprogrammed to form iPSCs, which were then differentiated into RPE cells. When these newly formed RPE cells were transplanted into the patient's retina, they restored the patient's vision.

iPSCs have shown potential for treating sickle cell anemia using a patient's own cells. Researchers reprogrammed the bone marrow stromal cells of a sickle cell anemia patient to form iPSCs. The mutation that causes the sickle cell phenotype in iPSCs was corrected using the CRISPR-Cas system. These iPSCs, when differentiated into erythroid cells, expressed the normal β-globin protein.

iPSC-derived cells are also being explored for their potential in cancer therapy. Tissues destroyed in a cancer patient due to radiation or chemotherapy can be replaced using cells differentiated from the patient's cells. However, attempts to transplant such iPSC-derived cells have not to date been successful.

Procedure

Scientists can promote induced pluripotent stem cell or iPS cell differentiation into various specialized cell types, including pancreatic beta cells, liver cells, and cardiomyocytes, using different methods.  

Cells are grown using different techniques, and differentiation is induced by adding specific growth factors to the cell culture medium in a particular sequence at specific times.

In one method, the iPS cells are grown in a culture medium, where they form three-dimensional cell clusters called embryoid bodies or EBs  that later form differentiated cells. 

For example, EBs differentiate into neurons when grown in a special culture medium supplemented with molecules, such as growth factors or vitamins, that trigger the neuronal differentiation pathway.

This method sequentially transforms the EBs from pluripotent cells to neural progenitor cells and, finally, to terminally differentiated and active motor neurons.

In another method, iPS cells are grown on artificial scaffolds that provide the extracellular matrix proteins for growth. The cells directly transform into specialized cells without forming the intermediate embryoid bodies.