The effect of hypoxia on adult mouse retinal ganglion cell and amacrine cell survival
Skaribas, Elena Evangelia
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Glaucoma is a group of ocular disorders characterized by optic nerve damage that leads to vision loss and blindness. Damage to retinal ganglion cells (RGCs), particularly through axonal damage due to an increase in intraocular pressure (IOP), is a proposed mechanism behind glaucomatous injury. Other than increased IOP, vascular changes leading to ischemia are another explanation for glaucoma. A state of ischemia leads to a decrease in nutrients supplied to neurons of the retina and creates a hypoxic environment which is linked to cell death in both IOP- and non-IOP-related injury. Injury during glaucoma not only affects RGCs but also has secondary effects that impact the function of other cells in the retina like amacrine cells (ACs). To better understand how RGCs and ACs respond during glaucomatous injury, this study characterized the changes in viability of these cells under hypoxic conditions over time. With the use of a unique immunopanning technique, RGCs and two subpopulations of ACs (CD15+ and CD57+) were isolated from 12-week-old C57BL/6J mice and cultured for 6 to 9 days. After about a week of culturing, the three cell types were placed under either normoxic (n = 5) or hypoxic (n = 6) conditions, and cell viabilities were measured at 1-hour time intervals over 24 hours. RGC and AC isolations based on the immunopanning technique resulted in high yield and viability, confirming the findings of previous optimization studies. In response to hypoxic conditions, RGCs and the two subpopulations of ACs all experienced a decrease in cell viability over the course of 24 hours. Surprisingly, CD57+ cells showed increased susceptibility to injury and death during isolation. However, the remaining CD57+ cells that stayed alive in culture by the start of the time-course experiment were the most resilient to cell death during hypoxia, showing significantly higher cell viability compared with CD15+ and Thy1.2+ cells. The characterization of CD15+, CD57+, and Thy1.2+ cells in response to hypoxia highlights a difference in resilience across neuronal cell types in the retina. Although CD57+ exhibited greater resilience than its counterparts, the mechanism behind neuroprotection among these cells is still unknown and requires further study.
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