Interrogating new targets for glaucoma gene therapy

Abstract

Purpose : We aimed to identify targets that regulate retinal ganglion cell (RGC) function, and to subsequently modulate these using gene therapy approaches to treat glaucoma. Exercise has been demonstrated to be profoundly effective at preventing the loss of RGC function, as measured by pSTR, in aged mice with elevated intraocular pressure (IOP). The aged IOP model recapitulates a transient loss of RGC function that is hypothesised to parallel the sustained loss of nerve cell function in glaucoma patients, prior to RGC death.

Methods : Acute IOP elevation injury (50 mmHg, 30min) was applied to 12 month old male C57Bl6 mice, and a cohort of mice were exercised for seven days post-injury. After seven days from the IOP injury RNA was harvested from the whole retina of four cohorts of mice (control [no IOP, no exercise], IOP, exercised, and IOP+exercised, n=4), cDNA was prepared for microarray analysis (Illumina gene chip, mouse), and analysis was performed in collaboration with AGRF (Melbourne, Australia). An adjusted p-value and B-statistic were used to screen candidate transcripts.

Results : Surprisingly, exercise was the dominant principal component within the microarray data (contributing 70.2% of observed variance), while IOP injury contributed less (1.1%) to the observed transcriptional changes. The transcriptional changes that were present in exercise, regardless of IOP injury, included genes involved with the β-catenin and BMP signaling pathways, and genes encoding mitochondrial enzymes. Elevated IOP altered the transcriptional levels of genes in the complement and inflammatory pathways. Edn2 was also significantly upregulated following IOP injury compared to uninjured control mice (adjusted p-value=1.93E-08, B-statistic=17.1), and was the only transcript that was elevated in exercised mice with IOP injury compared to mice that were only exercised (adjusted p-value=3.9E-05, B-statistic=4.2).

Conclusions : Exercise has a potent effect on retinal transcription, while the sustained transcriptional changes from IOP injury were less obvious after 7 days of recovery. The stress response gene Edn2, which has shown to be elevated in several glaucoma models^{1, 2}, warrants further investigation.

1. Howell, G.R., et al., JCI, 2011. 121(4): p. 1429-1444.
2. Yang, Z.Y., et al., IOVS, 2007. 48(12): p. 5539-5548.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.