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Michelle Lajko, Herminio J. Cardona, Joann M. Taylor, Kathryn N. Farrow, Amani A Fawzi; Retinal HIF-1α and VEGF levels differ between C57BL/6N and C57BL/6J mice with hyperoxia induced lung injury. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3629.
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© ARVO (1962-2015); The Authors (2016-present)
The levels of hypoxia inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in the retinas of two strains of mice with hyperoxia induced lung injury have yet to be investigated. We hypothesize that HIF-1α and VEGF levels would be greatest 24h after removal from 75% oxygen, and no interstrain difference would be observed.
Neonatal mice from two different strains (C57BL/6N and C57BL/6J) were exposed to 75% oxygen from P0 to P14. At P14 mice were removed to room air (21% oxygen). We examined the retinas at P14, P14+1, P14+7, or P14+14. Age-matched room air control mice of the same strain were sacrificed at the same time points. The retina was dissected from one eye and homogenized for protein, and the other eye was fixed in 4% paraformaldehyde and sectioned (N=5-6). HIF-1α protein expression was quantified using western blots of retinal lysates, normalized to β-actin loading control, and represented as fold change relative to room air control mice. VEGF levels were measured by ELISA. Data presented as mean ± SEM. Retinal cross sections were examined using immunohistochemistry to locate the source of HIF-1α and VEGF.
At P14+1, HIF-1α was significantly increased in both strains of BPD mice compared to respective P14 BPD mice. Comparing the two strains, HIF-1α levels in C57BL/6J BPD mice were greater than C57BL/6N mice at every time point. C57BL/6J had significantly more HIF-1α protein than C57BL/6N at P14 (6J 4.6 ± 0.4 fold change, 6N 0.4 ± 0.2 fold change, p=0.004) and P14+1 (6J 9.4 ± 0.3 fold change, 6N 4.0 ± 0.1 fold change, p=0.001). Comparing VEGF levels in C57BL/6N BPD mice, VEGF levels peaked at P14+1 (336.7 ± 108.11 pg/mL, p=0.033). In C57BL/6J BPD mice, VEGF levels peaked at P14+7 (163.1 ± 28.1 pg/mL, ns). Stained sections showed HIF-1α and VEGF in the retinal ganglion cells and cells in the inner nuclear layer.
Our results were consistent with the hypothesis that HIF-1α and VEGF would be highest 24h after removal from 75% oxygen. However, there was a strain difference in HIF-1α protein levels. The VEGF ELISAs showed that C57BL/6N had peak levels at P14+1, and C57BL/6J BPD mice had peak levels at P14+7. We believe these strain differences may be related to variability in response to reactive oxygen species, which we are currently exploring.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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