Studies in mouse models of night blindness have demonstrated that vision can be restored by transplanting rod precursor cells taken from mouse neonates directly into the retina of recipient animals. The University College London (UCL) Institute of Ophthalmology-led team showed that the transplanted rod cells made synaptic connections with the existing retinal circuitry, were light responsive, and generated visual signals. The transplantation built on their previous photoreceptor transplantation research, and was optimized to increase the number of cells that integrated in the retina.
Critically, a range of tests in animals receiving the transplants confirmed that the treatment restored vision. The level of apparent visual correction correlated with the number of functional transplanted cells, and some restoration of vision was achieved even when the numbers of integrated photoreceptors accounted for less than 1% of the total rods in the retina. And while the reported studies used donor cells taken from newborn rats, the team is hopeful that it will be possible to derive transplantable photoreceptor cells from embryonic stem cells.
Reporting their findings in Nature, Robin Ali, M.D., and colleagues admit far more work will be needed before this approach can be translated into the clinic. However, they conclude, their results “demonstrate for the first time that transplanted rod-photoreceptor precursors can integrate into a dysfunctional adult retina and, by directly connecting with the host retinal circuitry, truly improve vision.” Their published paper is titled “Restoration of vision after transplantation of photoreceptors.”
The research team is separately working to improve the efficiency of cone photoreceptor transplantation in parallel with rod transplantation, and to increase the effectiveness of the transplantation process. “We will probably need to do both in order to develop effective treatments for patients,” comments co-researcher Rachael Pearson, M.D. Nevertheless, comments Rob Buckle, M.D., head of regenerative medicine at the MRC, “this is a landmark study that will inform future research across a wide range of fields including vision research, neuroscience, and regenerative medicine. It provides clear evidence of functional recovery in the damaged eye through cell transplantation, providing great encouragement for the development of stem cell therapies to address the many debilitating eye conditions that affect millions worldwide.”