Colorblindness and macular degeneration are
both eye diseases that scientists have been researching in order to eliminate. In a
study set for publication in the journal Science, biologists at Johns Hopkins
have created “organoids” as a model to study the development of the human eye.
Developmental biologist Robert Johnston and his team focused on the growth of cells that allow people to see the colors red, blue, and green.
The team grew human eyes in a lab from stem cells as
opposed to experimenting on the eyes of mice or fish as they can’t process color the way humans
can. It was discovered that the three color detecting cells (red, blue, and
green) were induced by thyroid hormone. Determining how much thyroid hormone
made a particular color cell allowed the team to manipulate the outcome
creating specific color photoreceptors. Their finding gives insight as the why
pre-term babies have higher evidence of vision disorders since they have
lowered thyroid hormone. The team also hopes to use these “organoids” to
develop other parts of the eye like the macula in an effort to eradicate
macular degeneration.
In
class we discussed color theories and how each part of the eye contributed to
vision. There are two forms of color blindness, true and partial. True
colorblindness means that the eye has no cones whatsoever and vision is only
processed through rods. Partial colorblindness means that photopigment is
missing. The retina is the light-sensitive tissue that lines the back of the eye
and houses two different photoreceptors, cones and rods. Cones are
photoreceptors that function well in bright light. Red, blue, and green are the
three cone photoreceptors that are responsible for color vision. Rods are the
photoreceptors that function oppositely since they are light sensitive. What
was not expressed in class is the process by which these red, blue, and green
cones are forged. This study furthers the understanding of the development of
these important cones and heightens the chances of eliminating
colorblindness through the use of thyroid hormone. Finding out
what grows cones can lead to discovering what other hormone or processes are involved in the shaping of other parts of the eye. This could in turn resolve other eye diseases like macular degeneration and even presumably blindness.
https://www.sciencedaily.com/releases/2018/10/181011143112.htm
By creating human retina cells with stem cells, it made for a great discovery. It seems that thyroid hormone plays multiple roles, especially in color photoreceptors. I wanted to connect new information that I learned to your post. I want to presume that pre-term babies with low thyroid hormone can be treated with sobetirome, which is a thyroid hormone receptor agonist. Which can aid in more actions of thyroid hormone to have more receptors to bind to. Resulting in a lowering of vision disorders.
ReplyDeleteI agree with Ashley, using human stem cells to create retina cells is a lot more effective than using another animal's retina cells because it eliminates the need for comparison. I wonder if thyroid hormone levels effect overall vision ability or just color-blindness? I found an article that stated that the thyroid hormone controls the retinal cone opsin expression which is the protein of color vision in rats. In rats with hypothyroidism, the color contrast sensitivity was impaired compared to control groups. When treated for the disease, the rats' color vision improved. I don't know if the rats were colorblind though, just less color sensitive. I think a downside to treating colorblindness with thyroid hormones would be then the overproduction of the hormone, which could cause hyperthyroidism.
ReplyDeletehttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC4404894/
ReplyDeleteI found it interesting that Johns Hopkins is also researching for a method to eradicate macular degeneration as well. Macular degeneration is a degenerative disease in which the macula, which is responsible for focusing central vision (reading, driving, recognizing faces and color, fine detail) is lost. Peripheral vision would still be retained, however, vision would be greatly impaired. Unfortunately, this disease is incurable. However, it can be treated to ease the symptoms and damage. There is an article about how a xanthophyll that has been found to mitigate the damage and progression of macular degeneration in different areas of vision such as quality of vision, sensitivity to contrast, as well as glare recovery. This study also proved that macular degeneration is partially a nutrition-responsive disorder.
Here is the link to the article mentioned:
Deletehttps://www.macular.org/lutein-antioxidant-supplementation-trial