Abstract
Purpose :
In congenital glaucoma, the ocular developmental abnormalities cause high intraocular pressure which places mechanical stress on the optic nerve head (ONH) and leads to optic nerve degeneration. Untreated or treated late children develop irreversible blindness. Astrocytes are the major glial cells in the ONH. Astrocytic mechanotransduction transduces mechanical stress to biological signals and regulates cell activity. In this study, we investigated the mechanosensing channels involved in ONH astrocyte mechanotransduction in an early-onset glaucoma mouse model.
Methods :
Homozygous egl1 mutant mice were obtained from the Jackson Laboratory. Intraocular pressure (IOP) was measured in conscious mice using the TonoLab tonometer. Mice were sacrificed and the ONH were collected before, 1 and 4 weeks after IOP elevation. Primary mouse ONH astrocytes were also cultured from the egl1 mice and subjected to mechanical stretch of 10% strain for 2 hours using a FlexCell Tension System. Real time quantitative PCR was performed to assess the expression levels of mechanosensing channels in the ONH tissue. The astrocytic location of significantly regulated genes in the ONH was further validated by immunohistochemistry staining co-labeling with astrocyte marker glial fibrillary acidic protein (GFAP).
Results :
The egl1 mutant mice developed elevated IOP starting from 4 weeks of age (22.1 ± 3.7 mmHg vs. 16.5 ± 1.7 mmHg in age-matched wild type animals, Mean ± S.D., n=10-14, p<0.01). Gene expression levels of mechanically activated ion channels of Piezo, transient receptor potential and potassium mechanosensing channel families were assessed. Expression levels of Piezo1 and Pkd2 in the ONH were upregulated in response to IOP elevation. Immunohistochemistry staining showed astrocytic location of elevated Piezo1 and Pkd2 in the ONH. After 2 hours of stretch, the morphology of astrocytes did not show significant changes; however, there was a significantly increased expression of Piezo1 and Pkd2 in stretch stimulated cells.
Conclusions :
Mechanosensing channels Piezo1 and Pkd2 respond to mechanical stretch and IOP elevation. Piezo1’s activity is regulated by Pkd2. The Piezo1 and Pkd2 interaction may play a role in ONH astrocyte reactivity in response to IOP elevation and contribute to pathogenesis of congenital glaucoma.
This is a 2021 ARVO Annual Meeting abstract.