Minimally invasive drug delivery of Galectin-3 inhibitors is neuroprotective in a mouse model of glaucoma

Purpose:
Galectin-3, a secreted lectin produced by microglia in neurodegeneration, plays a critical role in the pathogenesis of glaucoma. Our previous study has shown promising neuroprotective effects of intravitreal injections of a galectin-3 inhibitor in a mouse model of glaucoma. However, more translatable methods of galectin-3 inhibitor delivery to the retina remain to be developed. Here, we utilized the microbead (MB) mouse model of glaucoma to evaluate and optimize two minimally invasive drug delivery methods of two different galectin-3 inhibitors.

Methods:
Elevated intraocular pressure was induced in two-month-old wildtype C57BL/6J mice by injecting MBs into the anterior chamber, while control mice received sham injections. Ten days after MB injection, treatment with two galectin-3 inhibitors (TD139 or N-Acetyl-D-lactosamine (LacNAc)) was administered via two methods: a slow-release subconjunctival gel that solidifies upon exposure to body temperature, or eyedrops prepared by dissolving hydroxyethyl cellulose in PBS. For the slow-release gel administration, 2 μl of vehicle gel, TD139 gel, or LacNAc gel were injected subconjunctivally into the temporal eye quadrant using a 33-gauge needle (n = 10–12). For the eyedrop treatment, vehicle drops, TD139 drops, or LacNAc drops were applied twice daily for 20 days (n = 15–19). Eyes were collected 30 days after the MB injection, and retinal ganglion cell (RGC) survival was assessed by quantifying Brn3a+ cells.

Results:
A significant loss of RGCs was observed in the MB-injected group treated with the gel vehicle compared to the sham-injected group (p < 0.0001). In contrast, MB-injected animals treated with TD139 gel or LacNAc gel were protected from RGC loss (TD139 gel: p = 0.0066; LacNAc gel: p = 0.0487). Similarly, significant RGC loss was observed in the MB-injected group treated with the eyedrop vehicle compared to the sham-injected group (p = 0.0021). However, MB-injected animals treated with TD139 eye drops or LacNAc eyedrops were protected from RGC loss (TD139 eye drops: p = 0.0066; LacNAc eye drops: p = 0.0487).

Conclusions:
We have demonstrated that both slow-release subconjunctival gel and eyedrops are effective methods for delivering Galectin-3 inhibitors to prevent RGC loss in a mouse model of glaucoma. These findings offer minimally invasive approaches for delivering Galectin-3 inhibitors as a neuroprotective treatment for glaucoma.