Induced Pluripotent Stem Cells
A new study conducted by stem cell researchers and ophthalmologists shows that the vision of blind mice can be improved through the use of an experimental treatment. This treatment uses stem cells taken from the skins of patients. The findings of the study show that induced pluripotent stem cells (or iPS cells) can be used to restore the vision of patients suffering from macular degeneration. Researchers suggest that the vision of patients suffering from other retina affecting diseases could also be improved through this novel method. iPS cells are derived from the adult human skin cells, however they retain their embryonic properties. The study has been recently published in the online journal Molecular Medicine.
“With eye diseases, I think we’re getting close to a scenario where a patient’s own skin cells are used to replace retina cells destroyed by disease or degeneration”, said the main author of the study, Dr Stephen Tsang. He also added that the current study strengthens the idea that in the near future, iPS transplants will have a major impact on the medical practice of the near future, suggesting that this near future is very close. Dr Tsang is an associate professor of ophthalmology at the Columbia University College of Physicians and Surgeons, in the United States.
The first information about human iPS cells arose in 2007 and was greeted by scientists who commended the discovery as a way of avoiding any ethical complications through the possibility of creating stem cells that are specific for each patient. iPS cells can evolve into any time of cell, very much like embryonic stem cells. There have been thousands of different iPS cell lines created from healthy patients and donors in the past years. However, most of the created cell lines have been used in drug screening and various research projects. Ophthalmologists support the transplantation of iPS cells into human subjects, saying that the eye is perfect for testing future iPS therapies.
“The eye is a transparent and accessible part of the central nervous system, and that’s a big advantage. We can put cells into the eye and monitor them every day with routine non-invasive clinical exams”, said Dr Tsang, whilst adding that even the most serious complications are not life-threatening. In the preclinical iPS study that was led by Dr Tsang, human iPS cells that were taken from a patient aged 53. These cells were first combined with growth factors which aided their transformation into specific cells found in the retina.
The main role of these cells is to nurture the light-sensing cells (the rods and the cones) and protect them from excessive cellular debris, heat and light. In the event that these retina cells are destroyed, the light-sensing cells degenerate, thus causing the patient to lose vision. The destruction of these retina cells happens in macular degeneration and retinitis pigmentosa. The main cause of vision loss in older patients is macular degeneration. Researchers estimate that almost 30% of people will suffer of a form of macular degeneration by the age of 75. Almost 7 million Americans are currently affected by this disease, scientists suggesting that this number will double by the year 2020.
The research team injected these iPS-derived cells directly into the right-hand side eyes of 34 laboratory mice. All of the mice suffered from a genetic mutation causing the degeneration of their own retina cells. In most of the tested subjects, the iPS cells were assimilated into the retina without causing any disruption. A group of control mice was also used, which received an injection of saline solution. The control group showed no improvement in the further tests.
Dr Tsang notes that these findings offer evidence that stem cell transplantation can cause a life-long neuronal recovery. He also added that neither of the mice showed any signs of tumor growth, thus showing that there is no reason to fear that the stem cell transplantation causes tumors. Dr Tsang said that future clinical trials on patients suffering from macular degeneration are planned for the next 3 years, following an extensive preclinical testing of animal subjects.
A similar clinical trial, published earlier this year, showed promising preliminary results for the use of retina cells that were derived from embryonic stem cells. These cells were used to treat 2 patients suffering from macular degeneration.
“These results are encouraging, but iPS cells could be a more attractive option than embryonic stem cells because patients may not need drugs to prevent rejection of the transplanted cells”, concluded Dr Tsang.
Full study text – “Long-term safety and efficacy of human induced pluripotent stem cell (iPS) grafts in a preclinical model of retinitis pigmentosa” can be found here.