Abstract
Purpose :
Astrocytes are crucial regulators of retinal angiogenesis, and are therefore poised to influence the pathobiology of retinopathy of prematurity (ROP). However the role of oxygen in retinal astrocyte development is poorly understood, and disruption of oxygenation is one the principal ROP risk factors. We hypothesized that perturbing environmental oxygen would disorder astrocyte development and contribute to pathologic angiogenesis. To test this hypothesis, we modulated environmental oxygen in neonatal mice and examined the effects on developing astrocyte-vascular networks.
Methods :
Neonatal CD1 mouse pups were placed either in room air (21% O2) or in a chamber to regulate oxygen concentrations. Mice were sacrificed at different ages, and their retinas fixed, immunostained and imaged by confocal microscopy. Data reported as mean +/- SEM with T-tests for statistical significance.
Results :
Oxygen levels were found to regulate proliferation of immature astrocytes, thereby influencing astrocyte number and density of the angiogenic astrocyte template. Raising mice in hyperoxia (75% O2) from P0-P4 and then returning them to room air results in an exuberant proliferation of astrocytes (P6-8 control 32 ± 8 % Ki67+ astrocytes, n=7; hyperoxia 47 ± 7% Ki67+, n=6; p<0.01), with numbers peaking at P8 (control 24,908 ± 1490, n=3; hyperoxia 44,121 ± 2413, n=2; p<0.05). Meanwhile, astrocyte numbers seem to be reduced and mitotic activity suppressed at P4 during the period of hyperoxia. We also found that angiogenesis was delayed by hyperoxia (P4: control 24 ± 3% retinal area, n=4; hyperoxia 5 ± 2%, n=3), and resumed after return to room air but with qualitative defects in patterning.
Conclusions :
We demonstrate that neonatal hyperoxia stalls vascular development, and that return to the relative hypoxia of room air stimulates a proliferative response in the astrocyte population. When angiogenesis resumes, there are qualitative patterning defects in both the astrocyte template and developing vascular network. Our results suggest that oxygen-induced dysregulation of astrocyte development may contribute to pathogenesis of ROP.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.