Purchase this article with an account.
Murray A Johnstone, Yi Jiang, Steven Padilla, Chen Xin, Elizabeth Martin, Ruikang Wang; Aqueous Outflow Pathways That May Be Specially Organized to Sense Flow and Pressure. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4707.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To describe highly organized aqueous pathways that may sense flow & pressure.
Ex vivo primate (nemestrina) eye; radial SEM sections - complete 360O of limbus. Karnovsky’s fixative perfusion-IOP 8 mm Hg. SEM protocol optimized for SC (SC) endothelium (SCE) preservation, Segments (135), Images (755).
Conduit-like pathways (CLP) arise from SCE to create a funnel-shape, then narrow to a cylindrical SCE-lined lumen that courses across SC to collector channel entrances (Fig. 1). Sections radial to the CLP funnel entrances in the juxtacanalicular space reveal a circular lumen composed of ring-forming scaffold cells (RSC). Funnel lumen interiors have 2 configurations: Type 1 (T1) lumens, (23 identified) contain sail-like cells (SLC) (Fig. 2B (*)). Cellular processes tether the SLC to the RSC. Type 2 (T2) lumens, (16 identified) have long cellular processes (LCP) spanning between RSC lumen walls (Fig. 2D). T2 lumens cut radially were measured: (n=9); width, 36.9±12.6 µm; height 21.8 µm±6.6 µm; area, 604.1±227 µm. In image in Fig. 2D, 57 total LCP were identified. In LCP close to the section surface (n=10): Mean length, 9.2±5.2 µm, R= 3.3-20.2 µm, mean minimal thickness, 131±34.4 nm, R= 79-198 nm. SEM reveals recurring highly organized CLP: T1 SLC present a large surface area to aqueous flow. Tethering of SLC to RSC walls by thin cellular processes assures both freedom of SLC movement and amplification of flow-induced forces at cell process-attachments to RSC walls. T2 lumen LCP span between RSC walls. IOP changes will increase RSC walls dimensions causing locally amplified forces at LCP attachments, a means of sensing pressure. Integrin signaling may provide local intrinsic regulation; the highly innervated region provides a means to couple sensory input to regional signaling pathways. The cochlea has structures somewhat similar dimensions, organization, and mechanisms to sense both fluid motion and pressure waves.
Our SEM protocol permits identifying highly organized conduits with 2 types of structures within their lumen, an arrangement somewhat analogous to the cochlea. T1 structures may permit sensing of flow by means of large sail-like cells that present a large surface area in the path of aqueous movement. T2 structures may permit sensing of pressure by means of prestressed processes suspended in a distending ring.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
This PDF is available to Subscribers Only