Expression of PIEZO1 and PIEZO2 Mechanosensitive Ion Channels in the Ocular Anterior Segment.

Abstract

Purpose : The mechanosensitive ion channels PIEZO1 and PIEZO2 play important roles in many physiological processes. The eye experiences mechanical forces and in particular, elevated intraocular pressure (IOP) is the primary risk factor for glaucoma. However, knowledge about the expression and role of PIEZO channels in the eye is still scarce. The objective of this study is to determine the expression of PIEZO channels in the anterior segment of the eye and review their potential functions.

Methods : We performed single molecule fluorescence in situ hybridization (smFISH) in C57BL/6 wildtype mice to probe for Piezo1 and Piezo2 mRNA. We also performed immunohistochemistry (IHC) in sectioned eyes from Piezo1^tdTomato and Piezo2^GFP transgenic reporter mice. Piezo1^tdTomato and Piezo2^GFP express tdTomato and Green Fluorescent Protein (EGFP) C-terminal fusion proteins of PIEZO1 and PIEZO2, respectively, under the control of their native promoters. PIEZO fusion proteins were detected using antibodies for the fluorescent protein tags.

Results : In the cornea, smFISH revealed robust Piezo1 and Piezo2 mRNA in the corneal epithelium. IHC using Piezo1^tdTomato and Piezo2^GFP reporter mice showed that Piezo1^tdTomato and Piezo2^GFP have a punctate localization pattern enriched at the plasma membrane. In the ciliary body process, we also found abundant expression of both Piezo1 mRNA and Piezo1^tdTomato. However, there was little expression of Piezo2 mRNA and no detectable Piezo2^GFP signal. Additionally, we detected Piezo1 and Piezo2 mRNA in the trabecular meshwork (TM), but we could not detect Piezo1^tdTomato and Piezo2^GFP by IHC. In the lens, we detected Piezo1 mRNA and Piezo1^tdTomato expression in the lens epithelium. We also found Piezo2 mRNA in the lens epithelium, but no significant levels of Piezo2^GFP expression. Lastly in the iris, there was no detectable expression of Piezo1 and Piezo2 by smFISH or IHC.

Conclusions : Piezo1 and Piezo2 channels are robustly expressed in the corneal epithelium. We also found both Piezo1 and Piezo2 mRNA in the TM and lens, as well as abundant expression of Piezo1 in the ciliary body process. This suggests that PIEZO1 and PIEZO2 may have diverse roles as mechanosensors in many tissues in the ocular anterior segment, including in IOP regulation.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.