Comments on: Stem Cells for Blindness

By: willradik

willradik — Thu, 26 Jan 2012 05:40:17 +0000

Is it feasible that a technique to regenerate damaged optic nerve tissue (such as that from glaucoma) might be developed from stem cells at some time? Or does the optic nerve present any special challenges that would make it less possible than the application you describe above?

By: Marshall

Marshall — Wed, 25 Jan 2012 21:35:00 +0000

I’m wondering if we can really isolate this as placebo. Regions of cortex that receive jumbled/signal-free information more or less stop working and might become co-adopted by other nearby networks. Couldn’t it be possible that the increased acuity in one eye “jump-started’ some of the binocular cells in V1 that receive inputs from both eyes, and that had previously been “sleeping” so to speak, leading to increased visual acuity in both?

By: daedalus2u

daedalus2u — Wed, 25 Jan 2012 16:43:38 +0000

In the eye there are some good ways (but indirect and non-standard) to test for basal nitric oxide levels. The vessels in the retina can be imaged in real time. These vessels respond to changes in light levels by dilating or contracting. How fast those vessels respond to changes in light levels is an indication of background NO levels.

Most of the retinal degenerative disorders are vascular in nature and are associated with other vascular disorders, hypertension, obesity, diabetes. Often these are secondary to low nitric oxide levels, for example tortuous retinal vessels is (to me) a classic sign of low NO causing flow mediated morphological changes in vessel anatomy due to normal vascular remodeling.

These are the same types of changes that occur in other tissue compartments, for example capillary rarefaction is commonly observed in diabetes, hypertension, vascular dementia, etc.

A common treatment for some types of retinopathy is to reduce the number of retinal cells by killing some via laser ablation. My hypothesis is that this reduces metabolic load to what the rarefacted retinal vasculature can support, so vision is improved even though there are fewer cells.

Since the physiological placebo effect is mediated through nitric oxide, a placebo effect would very likely lead to improved vision.

Stem cells might also generate NO, they might also trigger immune system interactions and inflammation which triggers NO and angiogenesis.

What would be an interesting test would be to put a reporter system that is activated by cGMP (which is activated by NO) into the stem cells that are being used, like in this work (which was not in stem cells).

http://www.ncbi.nlm.nih.gov/pubmed/22016390

You couldn’t really do this in humans, unless maybe you tied it to something so it would default to “off” (maybe not even then). Then you could image where the NO levels are, and how various treatments affect them.

By: starskeptic

starskeptic — Wed, 25 Jan 2012 10:35:19 +0000

“due to placebo”
…in other words – the placebo did nothing and this particular case “improved” on its own…

By: BillyJoe7

BillyJoe7 — Tue, 24 Jan 2012 20:32:02 +0000

This is how the ABC treated this story;

http://www.abc.net.au/pm/content/2012/s3414738.htm

A reporter interviewed Martin Pera, professor of Stem Cell Sciences at the University of Melbourne. It’s not bad except for the fact that the professor failed to mention that the “improvement” in the second patient was most likely due to placebo (because the vision in the intreated eye “improved” also).