Research on induced pluripotent stem (iPS) cells has been progressing feverishly since 2006, when Japanese researcher, Shinya Yamanaka of Kyoto University, first managed in 2006 to make skin cells behave like embryonic stem cells.

The latest success comes from the University of Wisconsin School of Medicine and Public Health. They have been able to grow multiple types of retinal cells from both embryonic stem cells and iPS cells.

The results have been published in the latest issue of the Proceedings of the National Academy of Sciences (PNAS).

In normal human development, embryonic stem cells begin to differentiate into more specialised cell types about five days after fertilization. The retina develops from a group of cells that arise during the earliest stages of the developing nervous system. The Wisconsin team has been able to use embryonic stem cells as well as pluripotent stem cells to trigger the development of retinal cell types.

Till date, researchers have been unable to produce “a highly enriched population of cells at the earliest stage of retinal specification that can progress through each of the major developmental stages” to become the retina.

The researchers from the University of Wisconsin have succeeded in doing this — studying all of the key events that lead to the generation of specialised neural cells. The highlight has been their ability to do it using both the embryonic stem cells and the iPS cells.

They first tried it out using embryonic stem cells and replicated the process using iPS cells. They were able to produce cells that expressed morphological features and/or markers of the eye field, retinal pigment epithelium, photoreceptors precursors etc.

The researchers were able to get a clear understanding of the time course through which cells differentiate to become the retina using both embryonic stem cells and iPS cells.

This is a landmark achievement as it will provide an ideal opportunity for studying and understanding the fundamental questions of human retinal development. A more practical application will be the use of iPS cells to produce pluripotent stem cell derivatives for testing drugs by pharmaceutical companies.

Studying retinal development in detail and treating conditions that are genetically linked will now become possible, by using the iPS-cell route. For example, skin from a patient with retinitis pigmentosa could be reprogrammed into iPS cells, and then into retina cells, which would allow researchers to screen large numbers of potential drugs for treating or curing the condition.

There is also a possibility, though distant at this stage, of repairing a damaged retina by using iPS cells produced from the patient’s skin cells.

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