Steven Schwartz and a team of researchers at the University of California carried out a study that involved implanting human embryonic stem cells (hESC) into patients with different forms of macular degeneration – a disease in which a wall of cells in the macula (centre of retina), known as the pigment epithelium, begin to degenerate. This causes patients to lose light sensing cells, known as photoreceptors, and central vision. The study was primarily to investigate the safety of implanting hESC’s into the body, and the results of this study prove to be very promising.
The study was performed on two women with different forms of macular degeneration. The first had dry age-related macular degeneration, which is the most common cause of blindness, found in older adults, shown in Figure 1. The second woman had Stargardts macular dystrophy, which is a rare hereditary disease found in adolescents and young adults.
Schwartz and his team used hESC’s from spare embryo’s donated to them by patients undergoing invitro fertilization, and developed them into retinal pigment epithelial cells (RPE) that could be implanted into the patients’ eyes. This was done by growing hESC into RPE cells on the skin cells of mice in a laboratory. The cells were then purified to make sure that they were human RPE cells, and did not contain any animal DNA or human pathogens. The cells were able to be detected as female RPE cells by analyzing the DNA of the cells, as humans have a unique number of chromosomes.
Once the cells were purified, 50,000 RPE cells were implanted into the centre of the retina. The patients had been on immunosuppressant’s prior to the procedure in order to reduce the chances of rejection. Following the trial, the patients were monitored intensively for any signs or abnormal cell growth, which could potentially lead to cancer, cataracts, increased pressure on the eye, or retinal detachment.
Four months after the procedure, there were still no signs of abnormal growth or rejection, and the cells appeared to be accepted by the tissue. The patients also began to experience improvements with their sight. The woman with Stargardts macular dystrophy was able to read the first five letters on the eye chart, and detect motion of a hand being waved in front of her treated eye.
While this study seems to be a breakthrough in regenerative medicine, many more studies need to be performed. The patients of the study will be continuously monitored, to ensure that the cells will still be accepted without long-term immunosuppressant’s, and more trials need to be carried out on other patients with macular degeneration. Unfortunately, as the retina is blocked off from the immune system, there is no way of knowing whether other parts of the body would accept the hESC as successfully.
Despite the improvement in sight of the patients, the primary purpose of the study was to assess the safety of transplanting hESC in humans. As it would seem, the future is looking bright, and it won’t be long before regenerative medicine is brought out into the light.