Abstract
Aquaporins (AQPs), by playing essential roles in the maintenance of ocular lens homeostasis, contribute to the establishment and maintenance of the overall optical properties of the lens over many decades of life. Three aquaporins, AQP0, AQP1 and AQP5, each with distinctly different functional properties, are abundantly and differentially expressed in the different regions of the ocular lens. Furthermore, the diversity of AQP functionality is increased in the absence of protein turnover by age-related modifications to lens AQPs that are proposed to alter AQP function in the different regions of the lens. These regional differences in AQP functionality are proposed to contribute to the generation and directionality of the lens internal microcirculation; a system of circulating ionic and fluid fluxes that delivers nutrients to and removes wastes from the lens faster than could be achieved by passive diffusion alone. In this review, we present how regional differences in lens AQP isoforms potentially contribute to this microcirculation system by highlighting current areas of investigation and emphasizing areas where future work is required.
Highlights
Our sense of sight is critically dependent on the optical properties of the lens and age dependent changes to these properties manifest as presbyopia in middle age and cataract in the elderly
To preserve its cellular structure the lens possesses a unique internal microcirculation system that, in the absence of a blood supply, delivers nutrients, removes metabolic wastes and controls the ionic homeostasis of the deeper lens cells [11,12,13]. Since this microcirculation involves the creation of a water flux that circulates throughout the lens, it has been proposed that the differential expression of members of the aquaporin (AQP) family of water channels in these different lens regions plays an important role in the generation of the microcirculation [12]
In this review we investigate how the specific properties of the three AQPs whose expression has been confirmed in the lens, AQP0, AQP1 and AQP5, contribute to the functionality of the different regions of the lens and how these water channels contribute to the generation and regulation of the microcirculation system that actively maintains the overall transparent and refractive properties of the lens [1]
Summary
Our sense of sight is critically dependent on the optical properties of the lens and age dependent changes to these properties manifest as presbyopia in middle age and cataract in the elderly. To preserve its cellular structure the lens possesses a unique internal microcirculation system that, in the absence of a blood supply, delivers nutrients, removes metabolic wastes and controls the ionic homeostasis of the deeper lens cells [11,12,13]. Since this microcirculation involves the creation of a water flux that circulates throughout the lens, it has been proposed that the differential expression of members of the aquaporin (AQP) family of water channels in these different lens regions plays an important role in the generation of the microcirculation [12]. We start our review with an overview of lens structure and function to provide the necessary framework to discuss the specific contributions of each lens AQP in the different lens regions
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
