Intravitreal HC-HA/PTX3: A potential novel therapy for proliferative vitreoretinopathy

Abstract

Purpose : Proliferative vitreoretinopathy (PVR), characterized by retinal surface membranes, is the main cause of failure of rhegmatogenous retinal detachments (RRDs). PVR is mediated by proliferation and epithelial mesenchymal transition (EMT) of RPE cells under the influence of vitreous growth factors. Heavy chain-hyaluronic acid/pentraxin 3 (HC-HA/PTX3) complex is a unique matrix component from amniotic membrane that exerts anti-inflammatory and anti-EMT effects. HC-HA/PTX3 is soluble and can be injected intravitreally. Therefore, we investigated whether HC-HA/PTX3 inhibits rabbit RPE cell proliferation in vitro and evaluated the safety and efficacy of intravitreal HC-HA/PTX3 in an established rabbit PVR model.

Methods : Primary rabbit RPE was isolated using dispase. HC-HA/PTX3 was prepared by our optimized manufacturing procedure. First, we tested if 12.5 to 200 µg/ml HC-HA/PTX3 was toxic to rabbit RPE cells in comparison to HA by the WST-1 assay. Next, we assessed the inhibitory effect of HC-HA/PTX3 on epidermal growth factor (EGF) and fibroblast growth factor 2 (FGF2)-induced proliferation in vitro by the WST-1 assay and immunostaining. Then, we tested the safety of intravitreal HC-HA/PTX3 injections using weekly ERGs and fundus exams for four weeks, followed by histologic analysis. Additionally, in New Zealand white (NZW) rabbits, we compared the ability of intravitreal HC-HA/PTX3 and PBS to inhibit PVR, which was induced using gas displacement of vitreous with intravitreal C₃F₈ and intravitreal injection of NZW RPE cells.

Results : HC-HA/PTX3 (up to 200 µg/ml), similar to HA, is not toxic to unstimulated rabbit RPE cells. EGF+FGF induced a 7-fold increase (p<0.05) in proliferation, which was inhibited in a dose-dependent fashion by HC-HA/PTX3, up to 2.2-fold (p<0.05) with 25 µg/ml. The addition of HA alone did not inhibit proliferation. Two rabbits injected with intravitreal HC-HA/PTX3 did not demonstrate any ERG or fundus exam changes and did not develop any histologic changes. 2 of 4 (50%) rabbits treated with HC-HA/PTX3 developed Grade 3 PVR compared to 7 of 8 (87.5%) of rabbits treated with PBS that developed Grade 3 or worse PVR.

Conclusions : HC-HA/PTX3 is a non-toxic matrix component in vitro and in vivo. HC-HA/PTX3 is a potent inhibitor of RPE cell proliferation and EMT in vitro and inhibits PVR formation in a rabbit model.

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