A Biodegradable Hydroxyapatite-Coated Magnesium Drainage Plate Enables Medium-Term Suprachoroidal Outflow Preservation and Stable Intraocular Pressure Reduction in Rabbits.

Abstract

Postoperative scarring and failure of surgically created drainage pathways limit durable glaucoma surgery. We developed a solid plate-type suprachoroidal space (SCS) implant based on hydroxyapatite-coated magnesium (HA-Mg) to provide temporary pathway support, an HA-modified material-tissue interface, and progressive biodegradation. TGF-β2-stimulated human iris pigment epithelial cells were used to assess material-associated effects on migration and fibrotic activation. In a paired-eye normotensive New Zealand White rabbit model, trabeculectomy, sham SCS surgery, titanium, uncoated magnesium, and HA-Mg groups were evaluated for 24 weeks using intraocular pressure (IOP) monitoring, ex vivo SCS angiography, micro-computed tomography, histology, α-smooth muscle actin (α-SMA) immunofluorescence, corneal endothelial assessment, aqueous humor pH, and systemic safety analyses. HA-Mg produced a sustained, stable IOP-lowering profile, whereas both Mg and HA-Mg showed greater net IOP reduction at Week 24 than the other surgically treated groups. HA-Mg showed broader posterior SCS contrast enhancement at Weeks 12 and 24. From Week 4 to Week 24, residual implant volume and surface area decreased by 93.6% and 86.3%, respectively, although residual material remained. Histology and α-SMA analysis were consistent with reduced fibrosis-associated interface remodeling, and Mg and HA-Mg extracts attenuated TGF-β2-induced migration and α-SMA expression. No evident ocular or systemic safety concerns were detected within 24 weeks. HA-Mg therefore supported medium-term preservation of the surgically created SCS outflow pathway while undergoing substantial but incomplete degradation; longer-term studies extending through and beyond complete implant resorption are required to determine whether pathway patency and safety are maintained thereafter. STATEMENT OF SIGNIFICANCE: Glaucoma drainage surgery remains limited by progressive fibrosis, foreign-body responses, and loss of long-term drainage pathway function. Although suprachoroidal space (SCS) approaches provide an alternative aqueous outflow route, maintaining pathway patency while minimizing the burden of permanent implants remains challenging. Here, we developed a biodegradable hydroxyapatite-coated magnesium (HA-Mg) drainage plate designed to provide temporary structural support and gradually degrade during tissue remodeling. The study integrates material characterization, medium-term in vivo evaluation, degradation tracking, fibrosis-associated remodeling assessment, and biosafety analysis in a rabbit model. Our findings support a biomaterial strategy that couples progressive biodegradation with preservation of SCS outflow-associated function, providing a potential framework for next-generation biodegradable implants in glaucoma surgery and other applications requiring temporary tissue-implant interfaces.