A highly-magnified image of photoreceptors, also known as rods and cones, in the human retina.

So, here I am catching up on some journal reading, when Nature sends out an eblast touting new exciting advances in stem cell work, including a paper about the eye. Of course, I immediately jump to the site and find a research paper published online that reports on the modestly successful transplantation of precursor rod cells — cells that are more developed than stem cells but not quite mature rod cells — into mice with night blindness (congenital stationary night blindness). While vision improvement was not dramatic, the treated mice did see better in dim lighting; they were able to navigate a water maze in greatly reduced light much better than untreated mice.

The most important aspect of this project is that the University College London research team, led by Dr. Robin Ali, was able to get some of the transplanted precursor rod cells to functionally integrate into the mouse retinas.  Even though only a fraction of the transplanted cells integrated — up to 16 percent — the cells did make the necessary connections in the retina to send visual information back to the brain. Functional integration has been an elusive but critical step for all researchers working in cell transplantation. So, this is an important advancement for the stem cell research field.

Dr. Ali’s ultimate goal is to derive both rod and cone cells from embryonic stem cells and transplant them into humans with various retinal degenerations, including macular degeneration and retinitis pigmentosa. He notes that cones, the cells that give us central, color and daytime vision, are more challenging to transplant than rods, the cells we use to see in the dark. But, I am confident he is on the right track. Dr. Ali and his lab do outstanding work.

This rod transplantation project is a great example of how scientific progress is so often incremental. While researchers occasionally hit home runs with big breakthroughs, advancements are usually achieved in a stepwise fashion, and every step forward gets us closer to treatments and cures.