Electrician’s Nightmare

Rods and cones. I learned those words back in the sixties in science class. We were studying the eye.

Rod cells are concentrated in the peripheral sections of the retina. They work well in dim light. They play a key role in night vision. While we need rod cells for good, overall vision, they have their limits. Rod cells are lacking in sharp vision and color perception.

That brings us to the discussion of cones. Cones are located most densely in the center of the eye. Their jobs are to see sharply in bright light and to easily perceive color.

Considering many of us have trouble with sharp, central vision and ‘wash-out’ in bright light, as well as have trouble with color perception, it comes as no surprise that we, those with AMD, are a little short on cone cells. If you have seen images of the ‘divot’ in your macula, that cone-shaped hole should be full of cone cells. Mine is not.

Because we are a bit short on cone cells, cone cells were what researchers were trying to grow for us. After a number of years the breakthrough came at the University of Montreal and was published in 2015. The head researcher was Gilbert Bernier. Merci, Gilbert!

Dr. Bernier came to the idea there must be something that helps to grow all those cone cells in the macula. After all, the embryonic cells are pluripotent. That means they are capable of becoming any one of several different cells. What makes it so these particular cells became cone cells?

Bernier discovered a protein that limited the stem cells to becoming pretty much only cone cells. He actually achieved about 80% purity, a pretty much unheard of accomplishment before this.

Even more exciting, Bernier’s cells organized themselves into nice, pretty sheets of retinal tissue. Not a disorganized mess.

And if that were not enough, when his cells were injected into the eyes of healthy mice, they migrated to exactly where they were supposed to be!!!! Stem cells with the homing instinct! Pretty cool. They were doing the happy dance in Montreal.

This is a huge step but not yet the answer to replacing cone cells, the photoreceptors we lack, and ultimately our vision. As I have said before, the cone cells grown in the lab are like cell phones without a tower. They do what they should do but have no way to send the signal to the brain.

According to the Discovery Eye article on the optic nerve and how it links to the brain, there are approximately 125 million photoreceptors, rods and cones, in the human eye. These connect to two, different intermediate neuron types and 23 different kinds of other retinal ganglion cells. Some of the retinal ganglion cells communicate with as few as five photoreceptors.

In short, the eye would be an electrician’s nightmare! It is no wonder no one has been able to figure it out yet.

There is, however, a way for it to be done. The knowledge of the body – remember these cells both organize themselves and migrate accurately – is miraculous. The next step is finding out how to give the connect order. I suspect the Montreal crew is working on it even now.

Bonne chance, Gilbert, bonne chance. [“Good luck, Gilbert, good luck” for those of us who don’t know French.]

written April 14th, 2017

Next: Cautionary Tale

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