Abstract
Purpose :
Glucocorticoids are widely prescribed to treat various ocular inflammatory diseases. Unfortunately, prolonged steroid usage can cause adverse effects in the eye, one of the most critical being steroid induced ocular hypertension (SI-OHT) and if left untreated, can lead to iatrogenic glaucoma and irreversible vision loss. Recent human genetics findings have identified common and rare coding variants in the Angiopoietin-like 7 (ANGPTL7) gene that are associated with lower intraocular pressure (IOP) and decrease risk for glaucoma. ANGPTL7 has also been shown clinically to be highly upregulated in the aqueous humor of glaucoma and steroid treated patients. The purpose of this study was to determine whether knocking out or reducing ocular Angptl7 mRNA levels can inhibit steroid induced ocular hypertension in mice.
Methods :
First, an Angptl7 genetic knockout mouse line was created using the VelocigeneTM platform. RT-qPCR and RNAscope confirmed Angptl7 knockout. Next, to develop SI-OHT, Angptl7 KO and WT mice were periocularly injected with dexamethasone-21-acetate (DEX-Ac) or vehicle control every week and IOP measurements were collected using a rebound tonometer. We also screened several Angptl7 siRNA duplexes for candidates that had the highest knockdown of Angplt7 mRNA via RT-qPCR. After three weeks of SI-OHT caused by DEX-Ac periocular injections, we IVT injected Angptl7 siRNA and followed IOP changes.
Results :
We found the IOP of naïve Angptl7 KO mice approximately 2-3mmHg lower than WT controls, which were consistent with human genetics findings. When WT mice were treated with DEX-Ac, we saw ~4-5mmHg increase in IOP compared to baseline and vehicle injected group over the course of 7 weeks. DEX-Ac did not elevate IOP in Angptl7 KO mice. To further test these findings, we decided to use siRNA to lower Angptl7 mRNA levels in mice after IVT injection. Out of several siRNA duplexes screened we found two that achieved >50% knockdown of Angptl7 mRNA and lowered IOP ~3-4mmHg when compared to control groups. When these Angptl7 siRNAs were injected in mice after 3 weeks of DEX-Ac treatment, it significantly lowered IOP within 7 days to baseline thus reversing SI-OHT in mice.
Conclusions :
These results suggest that knocking down ANGPTL7 could be a feasible therapeutic approach to lower IOP, which is currently the only modifiable risk factor for the various forms of glaucoma.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.