Abstract
Purpose :
Anterior segment dysgenesis involves abnormal development of one or more anterior segment structures, including the trabecular meshwork (TM) and Schlemm’s canal (SC); this increases risk of developing glaucoma due to elevated intraocular pressure (IOP). We have generated a unique mouse model by deleting activating protein-2β (AP-2β) transcription factor from the developing periocular mesenchyme and its derivatives. The resultant mutant shows a partial angle closure and increased IOP. We hypothesize that the uveoscleral pathway remains functional in this model and thus IOP can be reduced through treatment with prostaglandin analogs such as latanaprost (LTP).
Methods :
MgpCre+/- mice were bred with tfap2b+/- mice. Male MgpCre+/-;tfap2b+/- offspring were then crossed with female tfap2blox/lox mice to obtain the final offspring, the MgpCre+/-;tfap2b-/lox or AP-2β trabecular meshwork region knockout (TMR-KO) mice, as well as littermate controls. A 40 kDA FITC-conjugated dextran tracer was injected into the anterior segment of mutant and control mice. 0.005% LTP eye drops were used for topical treatment of the eye. The mice were euthanized 10 minutes after injection and eyes were enucleated, fixed, and cryosectioned. RNAscope Hiplex Assay was performed to determine changes in key genes in the mutants that are critical for proper functioning of TM and SC.
Results :
In control mice, dextran clumps were observed in the TM region, both with and without LTP treatment (n=6 eyes). This was absent in the mutant mice, likely due to a blocked conventional pathway as demonstrated by previous histological staining. In comparison, dextran was observed along the uveoscleral pathway in the mutants after 5 and 10 minutes of LTP treatment (n=6 eyes). The RNAscope Assay performed in control and mutant mice revealed decreased levels of important SC markers, including Prox1 and Klf4, in the mutant.
Conclusions :
Our findings show that while the conventional pathway is blocked in the TMR-KO mutants, the uveoscleral pathway remains functional. Reduction in both Prox1 and Klf4 levels further supports that development of the conventional pathway is altered in the TMR-KO mutants. Since these genes encode pressure-induced transcription factors, it is surmised that lack of aqueous flow through the SC region during development contributed to the phenotype.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.