Retinal Pigment Epithelial Cells of Living Retina Imaged For First Time
February 26, 2009
Biology News Net reports that a layer of “dark cells” in the retina (referred to as retinal pigment epithelial, or RPE, cells) that is responsible for maintaining the health of the light-sensing cells in our eyes, has been imaged in a living retina for the first time. The findings were reported in the most recent issue of Investigative Ophthalmology and Visual Science.
Lead researcher David Williams, director of the Center for Visual Science and professor in the Institute of Optics at the University of Rochester, stated that one of the goals of his team’s research is to figure out why macular degeneration actually happens. According to the article, the techniques being developed by Williams’ team could eventually help spot illness in the RPE cells long before patients experience symptoms, thus allowing doctors to start patients on therapies early enough to possibly slow or stop the onset of macular degeneration.
Read more about this research breakthrough on Biology News Net.
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8 Responses to “Retinal Pigment Epithelial Cells of Living Retina Imaged For First Time”
Ari,
A late thought:
It occurs to me that the RPE cells might be heavily pigmented to protect them from cumulative photo-oxidative damage, the very thing that they protect the photo-receptor outer segments from! If this is the case, then even animals with a more limited colour vision than us will have black RPE cells, so it’s bad news. 🙁
Sorry, I made two mistakes in my last post. The 10 billion molecules/second must have been retinal, not opsin, because the opsin comes woven into the disc, and it is the retinal that has to be continuously replenished at a high rate. The other mistake was the “schoolboy howler” of implying that the RPE cells were not part of the choroid! (I am a physicist by training, and only self-taught in biology.)
However, the issue of blood for disc recycling versus blood for retinal flow is still of interest, and in that regard, it seems relevant that disc recycling requires oxygenated blood, because it is an energetic process, whereas retinal flow is not.
Ari, two questions:
1. Where exactly does the retina usually detach – is it (1) the conecting cilium of the photosensors, (2) the interface between the photoreceptors and the RPE cells, or (3) the back of the RPE cells, at the choroid?
If it is (1), I should simply correct my initial point about the chewing, because that is apparently at the wrong end of the rod outer segment, but neither (1) nor (2) would affect my previous conclusion that it is the need to recycle opsin discs that makes the mammalian/vertebrate retina more easily detached than it might have been. Option (3), in which RPE cells remain attached to the rest of the retina, however, would.
2. Which process do you think uses more blood: continuous opsin renewal (10 billion molecules per second according to a recent paper) or daily opsin disc recycling (a shorter, but perhaps more intense energy demand)?
PS, if you don’t have time for this, I’ll understand 🙂 , but I am trying to understand a bit of biology that may be important to the evolution of vertebrates, as well as ophthalmology, I think.
understood!
Ari, I wasn’t arguing against that. I was merely pointing out that the retina is only delicately attached to the RPE cells so that they can have their hindmost opsin discs chewed off, and that this delicateness makes retinal detachment more likely than if there was a firmer bond. A firmer bond would presumably make it difficult for the RPE cells to perform that function.
the retina gets detached due to vitreous tugging, not due to disease or function of the rpe.
My previous understanding of the RPE cells was that they chew off the hindmost few opsin discs from the light sensing cells, but this is on a daily basis, not from moment to moment, as they get charged and discharged. Presumably, this is a separate function, and (I’m guessing) is the underlying reason for our delicate, easily detached retinas. This would not be a competing explanation to the hair-like projections at the backs of the light sensors, rather it would be another aspect of it.
PS, my interest in eyes is as a physicist with a professional interest in optics and an amateur interest in evolutionart biology.
Thanks in advance for any replies.
I’ve been able to capture a picture of the imaging of the RPE cells in a living retina from another source of the story. It, along with a nice drawing showing the location of the RPE layer in the retina are shown in my writeup of this story.
Here’s the link:
http://irvaronsjournal.blogspot.com/2009/02/amd-update-4-does-visualizing-rpe-cells.html
Irv Arons
