The Promise of Stem Cells in Neurodegenerative Diseases

Human embryonic stem cells – the earliest cells within a fertilized human blastocyst (a 4-5 days old embryo consisting of just 150-200 cells) – hold great potential for cell replacement therapies, where cells are lost due to disease and/or injury. Why is this the case? Well, embryonic stem cells have two key properties that make them so valuable: First, they can be expanded in culture – thus, researchers can obtain the necessary amount of cells that are needed for therapeutic treatment. Second, these cells can then be transformed into any cell type of the human body – like nerve cells that could then potentially be used for treatment of patients suffering from certain neurodegenerative diseases. Nevertheless, isolating embryonic stem cells ultimately results in the destruction of the fertilized human embryo, which always raises ethical issues. Furthermore, since every person is equipped with a different immune system, patients would have to take immunosuppressants in order to avoid the rejection of the newly transplanted cells from the body.

However, during the last decade, we have witnessed the development of the so called “induced pluripotent stem cell” (iPSC) technology, which revolutionized the stem cell field, as well as the regenerative medicine.


So…..what are iPSC?


In simple terms, these type of stem cells are artificially derived from adult cells by inducing a “forced” expression of specific stem cell genes (genes that are “very active” in embryonic stem cells). In other words, researchers are able to turn the clock of our cells backwards!

Since the source of the “reprogrammed” cells (e.g., skin cells, blood cells, etc.) as part of the generation of iPSCs is readily accessible, this opened up an entirely new chapter in regenerative medicine by not only going around the ethical issues, but also significantly reducing immune rejection problems after transplantation since these IPSCs are derived from skin or blood cells from the patient himself. Furthermore, by taking adult cells directly from patients, we now have the ability to create “disease models” (also know as “disease in a dish”) for many conditions that were not possible before. As of today, numerous diseases have been modeled using iPSCs and many researchers are exploring the possibility of utilizing iPSC-derived cells for cell replacement therapy.

One of the pioneers of the iPSC work, Shinya Yamanaka, was awarded the Nobel Prize in Physiology or Medicine (together with John B. Gurdon) this year. Considering that Dr. Yamanaka’s first study related to iPSCs was published in 2006, it’s easy to appreciate the enormous impact that this technology has created as substantiated by the decision of the Nobel Prize committee.

describe the imageEven though, iPSCs can be generated reproducibly, the efficiency of the reprograming remains low (i.e., around 1% using the original method). Furthermore, the initial generation of iPSCs utilized technologies that can lead to certain gene mutation (leading, for example, to cancer). However, the beauty of the iPSC technology is its simplicity and reproducibility. Since 2007, iPSCs have been in the central focus of stem cell research and regenerative medicine, and researchers throughout the world have made a number of improvements to Yamanaka’s original protocol. Today, we have safer and more efficient methods for generation human iPSCs for disease modeling or cell replacement therapies, and by the look of how much has been achieved so far, the technology is only going to get better and more proficient. Considering that human embryonic stem cell derived approaches have been successfully used at the clinical level for cell replacement therapies, there is no doubt that iPSCs will eventually prove to be the ultimate source for regenerative medicine in the future.



describe the imageVolkan Coskun is an Assistant Researcher & Lecturer at UCLA. He received his M.D. from Ankara University and his Ph.D. from Emory University. Volkan‘s research interests include neuroscience, regenerative medicine, stem cells and cancer research.


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