miR-181 expression and inhibition: a potential new treatment for dominant rhodopsin associated retinitis pigmentosa.

Abstract

Purpose : Retinitis pigmentosa (RP) is an inherited retinal degenerative disease caused by death of rod photoreceptor cells. While gene augmentation is a promising treatment strategy for patients with early-stage disease, this approach is unlikely to be effective for those with dominantly inherited forms of RP that result from production of a toxic protein product. The leading cause of dominantly inherited RP in the western world is Pro23His rhodopsin. In a recent study, inhibition of signaling microRNAs with proposed ties to apoptosis called miR-181a/b was shown to be neuroprotective in settings of neurodegeneration in the rat CNS. The purpose of this study was to determine if miR-181 is expressed in the rat retina and to assess toxicity and function of a novel miR-181 inhibitor following subretinal injection.

Methods : To inhibit miR-181 as previously described, we used AAVs encoding a “tough decoy” (TuD) which sequesters miR-181a/b using high-affinity antisense binding (AAV5-TuD-181). To assess toxicity AAVs (1x109 vg) were injected subretinally in wild-type rats. Animals were sacrificed and eyes were harvested at 1-week and 1-month post-injection. Presence of miR-181 was assessed via PCR. AAV5 transduction efficiency and local toxicity were assessed via confocal microscopy. TuD-181 function was measured by evaluating expression of the miR-181 target NRF1.

Results : Expression analysis revealed robust expression of miR-181a in the rat retina. Confocal microscopy revealed excellent AAV transduction efficiency and robust expression of TuD-181 as determined by GFP expression (Figure 1). No evidence of photoreceptor cell toxicity was detected at either 7- or 30-days following subretinal injection. Overexpression of TuD-181 increased expression of NRF1, indicating robust suppression of miR-181 in animals following subretinal injection (Figure 1).

Conclusions : MiR-181a is expressed at high levels in rat retina. AAV5 delivered TuD-181 was found to be stably expressed, well tolerated, and functional in rat photoreceptor cells following subretinal injection. Studies designed to evaluate the ability of AAV5-TuD-181 to delay disease progression are underway.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.