Abstract
Purpose :
We previously found that the expression of arginase 1 and 2 (Arg1, Arg2) may contribute to intraocular pressure (IOP) homeostasis. The exogenous nitric oxide (NO) pathway has been shown to play a role in IOP regulation. Due to the role of sex and aging on NO production, we aim to investigate the effect of biological sex on IOP regulation.
Methods :
Weekly IOP levels were measured in 3 groups: 1) wild type (C57/BL6, 21 males/ 19 females), 2) Arg1+/- (20 males/ 14 females), and 3) Arg2-/- (77 males/ 66 females) mice using rebound tonometry in both eyes from 24 to 108 weeks. The IOP levels were compared using student t-test. We evaluated the iridocorneal angles using a Leica Envision SD-OCT R2200 system. After the study, collected mouse eyes were fixed and embedded using the JB-4 Embedding kit for structure analysis. We examined the expression of ARG1 and 2 in human and mouse corneal rims. Human corneal rims were fixed and embedded in paraffin for histological sections. Outflow tissues were then incubated with primary antibodies against ARG1 or ARG2, followed up with incubation of the 2nd antibody for immunofluorescence-based protein analysis. We examined the expression of ARG1 and ARG2 in a single cell RNA-Seq database in the anterior segment of human eyes.
Results :
There was a significant IOP decrease from 13mmHg to 12mmHg following week 50 in both female and male WT mice. While male Arg1+/- and Arg2-/- mice did not demonstrate an age-related IOP decrease following week 50 with IOP remaining stable at 13-14mmHg, the female knockout mice exhibited major fluctuations after week 50 with IOPs ranging from 12-15mmHg. After 95 weeks, the WT mice experienced further IOP decrease to 10-11mmHg. Thus, the male mice showed separation between the WT and knockout genotypes. However, the female mice saw less difference among the WT, Arg1+/-, and Arg2-/- groups over time due to the considerable fluctuations in all genotypes. We confirmed an open iridocorneal angle in all the aging mice using SD-OCT imaging and histological analysis. The expression of ARG1 and 2 was identified in human outflow tissues. scRNA-Seq suggested a high ARG2 gene expression in the anterior segment of human eyes.
Conclusions :
The loss of Arg1 or Arg2 in male mice prevented the age-related IOP reduction observed in WT male/female mice. For the first time, our data suggests a potential role of biological sex and aging in ARG1/ARG2-mediated IOP homeostasis.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.