One of the biggest challenges in regenerative medicine is ensuring the long-term survival and integration into tissue of any meaningful fraction of transplanted cells. Most transplanted cells simply die. Most early cell therapies achieve benefits via the signaling generated by transplanted cells, in the short period of time before they die. Numerous approaches are under development to try to ensure long-term survival of transplanted cells, but successes have so far been few and far between. Here, researchers report on one of these successes, generating retinal cells that integrate into the retina to produce tissue regeneration.
Researchers have presented the first successful attempt to generate retinal cells that can integrate into the retina. Retinal ganglion cells (RGCs), commonly damaged in glaucoma, are responsible for the transmission of visual information. The scientists managed to not only grow neurons (retinal ganglion cells are considered specialized neurons), but also transplant them into the eyes of mice, achieving the correct ingrowth of artificial retinal tissue. Without treatment, glaucoma can lead to irreversible damage to the optic nerve and, as a result, the loss of part of the visual field. Progression of this disease can lead to complete blindness.
Retinal cells were grown using special organoids, with the tissue formed in a petri dish. These cells were subsequently transplanted into several groups of mice. "Our studies in mice have shed light on some of the basic questions surrounding retina cell replacement, i.e. can donor RGCs survive within diseased host retinas? Or are transplants only possible within young hosts? Using mice in which we used microbeads to artificially elevate intraocular pressure and a model of chemically induced neurotoxicity, we could show that transplanted donor cells survive in disease-like microenvironments. In addition, we could demonstrate that cells survived independent of the donor's age and the location to which the cells were delivered within the retina."
According to the authors, these cells have successfully existed inside mouse retinas for 12 months, which is a significant period for the species. Scientists confirmed that they were able to receive signals from other neurons in the retina; however, the ability of the cells to transmit signals to the brain has yet to be assessed with absolute certainty.