In vitro markers predict in vivo efficacy of a nano-structured glaucoma shunt

Abstract

Purpose : Cell-biomaterial interactions and aqueous soluble factors regulate the initiation and progression of fibrosis, which is a primary cause of glaucoma drainage implant (GDI) failure. We created smooth and nano-structured electrospun scaffolds to evaluate and compare the expression of fibrosis-related genes in fibroblasts in vitro. We then designed two nano-structured, partially degradable GDIs and evaluated their performance in rabbit eyes.

Methods : Fibroblasts were seeded on scaffolds made from electrospun polyethylene terephthalate (PET) nanofibers or smooth PET films. Transcription of fibrosis-related genes in unstimulated and activated fibroblasts was quantified by qPCR. Predictive fluid flow modeling was applied to develop nano-structured GDIs of different lengths, both with an inner diameter of 75 µm and a 25 µm degradable polyglycolide core (Pressure Control Shunt, PCS1 and PCS2). Intraocular pressure (IOP), GDI patency, bleb morphology, and capsule thickness were evaluated for 91 days in normotensive New Zealand White rabbits.

Results : Fibroblasts cultured on nanofibers showed reduced levels of gene expression related to activation (MYOCD and SMA), collagen synthesis (COL6A6), focal adhesion-associated genes (rho-kinase signaling, ITGA6, ITGB1) and increased expression of MMP-1 and ITGA2 compared to cells cultured on smooth surfaces. In vivo, a mean reduction in IOP from baseline of 4 (PCS1) and 2.8 mmHg (PCS2) at 28 days and 1.8 (PCS2) and 0.9 mmHg (PCS1) at 91 days was observed post-operatively. Histological analysis revealed a fibrotic capsule thickness of 350 ± 149 µm in PCS1 and 55 ± 23 µm in PCS2 (p=0.041), likely due to decreased aqueous flow rate through the longer PCS2.

Conclusions : Nanofibers significantly attenuate expression of markers associated with fibroblast activation and collagen production in vitro. Nano-structured shunts can be designed to safely and effectively reduce IOP for a period of at least 91 days in vivo while minimizing fibrotic encapsulation.

This is a 2021 ARVO Annual Meeting abstract.

 

(A) Morphology of fibroblasts cultured on a nanofiber surface as visualized by (i) confocal microscopy and (ii) SEM. (B) Differential gene expression in fibroblasts cultured on nanofibers as compared to a smooth surface with top 10 fibrosis associated genes highlighted. (C) (i) Schematic of PCS1 and PCS2 designs and (ii) in vivo IOP change from pre-operative baseline. (D) Masson’s trichrome staining images of (i) PCS1 and (ii) PCS2.