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that respond to light by forming a complex circuitry transmitting these visual signals to the brain via the optic nerve (Fig. 2). Recent data strongly suggest that lasting harm to the retinal neurons has already ensued before the onset of the more noticeable abnormalities in blood vessels of the diabetic retina. Hence, it is highly desirable to develop biomarkers that allow early detection of neuronal degeneration in patients with diabetes and diagnose DR before clinical signs become apparent. In this context, identification of the core molecular mechanisms leading to neuronal degeneration is the first crucial step toward enabling preventative treatment strategies and targeting early DR pathology.
Fundamental mechanisms underlying neuronal degeneration are customarily studied by isolating neurons from the retinal tissue of embryos or young mouse pups within 1–10 days after birth. These neurons are then cultured in a dish and maintained in
live conditions by providing
them with adequate nutrition
and specific factors needed
for their growth. However,
this approach has several
drawbacks: Neurodegenerative
diseases such as DR typically
affect mature or aged neurons,
rather than embryonic neurons.
Therefore, isolating neurons
from adult animals would
definitely be more relevant
for this kind of research.
Moreover, cells cultured from
rodents, such as mice or rats,
frequently do not recapitulate
the physiological processes
observed in humans, resulting
in failure at the clinical trial stage after preclinical verification in mice. In our lab, we cultured adult neurons isolated from goat retina as a distinctive model to observe the effects
Dr Harshini Chakravarthy || 23
of high glucose levels on mature neurons. Our studies in goat may expedite the detection of new, functionally important pathways in higher mammals that may not be discovered through studies in rodent-derived cells.
“Neurite” is a term that refers to the extension of slender projections from the cell body of a neuron. The extension of neurites is crucial for transferring signals from one neuron to another through synapses. Several proteins and receptors present on the tip of the neurite help in sensing appropriate guidance cues from outside the cell, which ultimately drives neurite extension by transmitting these signals to the interior of the neuron. Among these are certain proteins called cell adhesion molecules (CAMs) located on the neuronal cell membrane. In the brain, CAMs such as contactin and Caspr have been well studied for their role in myelination. These CAMs are also found in retinal neurons, which are not
myelinated. So, we wondered whether the CAMs found on the surface of retinal neurons could be involved in neurite extension or synapse formation, which helps in the transmission of visual signals. We also wanted to find out whether the function of these CAMs was affected by high glucose levels, which is a major factor in the development of diabetic complications.
To test our hypothesis, we first cultured live retinal neurons isolated from an adult goat and maintained them in cell-culture dishes for 10 days. We probed the cells using specific cell- surface biomarkers to help us
detect the presence of neurons in our culture of retinal cells. From our studies, we identified approximately 30%–40% of cells having neuronal markers, indicating that they were
   The management of DR poses a serious challenge in the clinic, since current approaches for the treatment do not fully prevent or reverse the pathology. Understanding the physiological processes associated with DR is therefore essential for developing new and effective treatment strategies for this debilitating complication of diabetes.
  






































































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