Abstract
Purpose :
Intracameral injections are an effective delivery route to tissues in the conventional outflow tract. One consequence of intracameral injection is a full-thickness corneal puncture and subsequent inflammatory response. This study assesses macrophage number and distribution in the conventional outflow tract after intracameral injection.
Methods :
Intracameral injections were performed by a single puncture using beveled glass microneedles. C57Bl/6 mice, aged 3-5 months, received unilateral intracameral injection of 2μl of PBS with the contralateral eyes serving as untreated controls (n=3). In a separate cohort, mice underwent unilateral transcorneal needle puncture to one-half anterior chamber depth (without injection) with untreated contralateral eyes (n=2). Intraocular pressure (IOP) was monitored at baseline and daily after treatment. Mice were sacrificed and eyes enucleated 3 days post-treatment. Eyes were fixed and immunostained to identify macrophages in the conventional outflow tract. Anterior segment whole mounts were imaged by confocal microscopy, and macrophages were quantified from 5-6 non-consecutive 40X magnification images per eye. Statistical analysis was performed by one-way ANOVA and post hoc tests with p < 0.05 considered significant.
Results :
At 3 days post-treatment, macrophage numbers increased in PBS injected and needle puncture eyes in the trabecular meshwork (TM) (53% with p < 0.002 and 40% with p < 0.03, respectively) and around distal vessels (DVs) (47% with p < 0.0001 and 60% with p < 0.0001, respectively) compared with untreated eyes. The number of macrophages in Schlemm’s canal (SC) was unchanged with PBS injection or needle puncture (p = 0.23) compared with control eyes. There were no significant differences in IOP from baseline in sham injection, needle puncture and untreated groups (p = 0.25, 0.25, 0.99, respectively).
Conclusions :
Intracameral injection of PBS results in an increased number of macrophages in TM and DVs but not SC, and our results suggest that this effect is due to needle puncture injury.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.