I am currently a senior at a public South Bay Area high school. After developing a passion for human biology through my high school studies, I am planning to pursue the pre-med path in college in hopes of becoming a physician one day.
I enjoy sharing my findings here from the medical research project that I worked on last summer.
Diabetic retinopathy (DR) is the leading cause of blindness in the working age population. It is an eye disease that develops when a diabetic patient’s hyperglycemia has been left untreated or has been present for a long period of time.
Unfortunately, there is no cure for this disease at the moment. Physically, someone might experience blurred vision, dark splotches, or floaters in their view. On a microscopic level, it has been concluded that acellular capillaries and pericyte ghosts are histological hallmarks of early stage DR. Therefore, diabetic patients who exhibit these symptoms may be at a risk of having DR. Acellular capillaries, pericyte ghosts, and leakage of blood ultimately contribute to blindness or loss of vision.
Altered gene expression can have a profound effect on the survival of retinal endothelial cells and pericytes, which are the structural support cells of the retinal vasculature. In order to study the effects of altered gene expression in the retinal capillaries, one needs to isolate the retinal capillaries first.
In this lab, I learned how to isolate the retinal capillary network of mouse eyes, stain them, take images, and look for variability in the retinal capillary network. In particular, I looked for acellular capillaries and pericyte loss which are associated with the development and progression of DR.
To begin with some foundational information, the retina is a light sensitive tissue in the posterior portion of the eye that transmits light to the brain through a series of neurons. The retina, which is responsible for the central vision, contains the macula and fovea, which contribute to visual acuity (as show in the figure).
The retina consists of 10 different layers, 3 of which contain nerve layers and 2 of which are synapse layers. In the retinal vasculature there are structural cells called pericytes, which are embedded on the outside of the capillaries, and there are endothelial cells, which line the inner lumen of the capillaries.
DR is a disease that causes damage to the blood vessels in the retina and changes the morphology of these capillaries. In a diabetic condition, the structural pericytes begin to undergo apoptosis, and when they die, the capillary loses its structure. This forms acellular capillaries, which are thin, collapsed tubules that are prevalent in patients with DR.
In order to actually analyze for the presence of collapsed tubules in the mice, the vasculature is isolated through a 2-day process called Retinal Trypsin Digest, RTD, followed by a staining procedure to make the capillaries visible.
In the RTD process, the retina is put through numerous washes with a 3% Trypsin solution. The retinal vasculature is finally mounted onto a slide and stained with Periodic Acid- Schiff’s Reagent (PAS) and Hematoxylin before being imaged. The resulting images of the stained slides have a varying number of acellular capillaries in the retina.
There are some mouse retinas that have 6-10 thin acellular capillaries while others only have 1-3 acellular capillaries.
From these results, I have been able to show that diabetic retinas have more acellular capillaries (approximately 6-10 per region). Wildtype, non-diabetic, mice tend to have 0-2 acellular capillaries, because the mouse does not have diabetes and does not have the risk of getting diabetic retinopathy.
Essentially, in diabetic, high glucose animals, acellular capillaries as well as pericyte ghosts develop from compromised capillary structure and barriers.
I look forward to my exciting college years to prepare me for my future medical career.
ABOUT THE AUTHOR:
Shaili is currently a senior at a public South Bay Area high school. After developing a sincere passion for human biology through her high school experiences, she is planning to pursue the pre-med path in college in hopes of becoming a physician one day.
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