Hyposmotic stress causes ATP release in a discrete zone within the outer cortex of rat lens.

Purpose: Purinergic signaling pathways activated by extracellular ATP have been implicated in the regulation of lens volume and transparency. In this study, we investigated the location of ATP release from whole rat lenses and the mechanism by which osmotic challenge alters such ATP release. Methods: Three-week-old rat lenses were cultured for 1 h in isotonic artificial aqueous humor (AAH) with no extracellular Ca2+, hypotonic AAH, or hypertonic AAH. The hypotonic AAH-treated lenses were also cultured in the absence or presence of connexin hemichannels and the pannexin channel blockers carbenoxolone, probenecid, and flufenamic acid. The ATP concentration in the AAH was determined using a Luciferin/luciferase bioluminescence assay. To visualize sites of ATP release induced by hemichannel and/or pannexin opening, the lenses were cultured in different AAH solutions, as described above, and incubated in the presence of Lucifer yellow (MW = 456 Da) and Texas red-dextran (MW = 10 kDa) for 1 h. Then the lenses were fixed, cryosectioned, and imaged using confocal microscopy to visualize areas of dye uptake from the extracellular space. Results: The incubation of the rat lenses in the AAH that lacked Ca2+ induced a significant increase in the extracellular ATP concentration. This was associated with an increased uptake of Lucifer yellow but not of Texas red-dextran in a discrete region of the outer cortex of the lens. Hypotonic stress caused a similar increase in ATP release and an increase in the uptake of Lucifer yellow in the outer cortex, which was significantly reduced by probenecid but not by carbenoxolone or flufenamic acid. Conclusions: Our data suggest that in response to hypotonic stress, the intact rat lens is capable of releasing ATP. This seems to be mediated via the opening of pannexin channels in a specific zone of the outer cortex of the lens. Our results support the growing evidence that the lens actively regulates its volume and therefore, its optical properties, via puerinergic signaling pathways.

Verification and spatial localization of aquaporin-5 in the ocular lens.

Until recently, the lens was thought to express only two aquaporin (AQP) water channels, AQP1 and AQP0. In this study we confirm lenticular AQP5 protein expression by Western blotting and mass spectrometry in lenses from a variety of species. In addition, confocal microscopy was used to map cellular distributions of AQP5 in mouse, rat and human lenses. Tandem mass spectrometry of a human lens membrane preparation revealed extensive sequence coverage (56.2%) of AQP5. Western blotting performed on total fiber cell membranes from mouse, rat, bovine and human lenses confirmed AQP5 protein expression is conserved amongst species. Western blotting of dissected lens fractions suggests that AQP5 is processed in the lens core by C-terminal truncation. Immunohistochemistry showed that AQP5 signal was most abundant in the lens outer cortex and decreased in intensity in the lens core. Furthermore, AQP5 undergoes differentiation-dependent changes in subcellular location from an intracellular localization in differentiating fiber cells to the plasma membrane of mature fiber cells upon the loss of fiber cell nuclei. Our results show that AQP5 is a significant component of lens fiber cell membranes, representing the second most abundant water channel in these cells. Together, the changes to AQP5 distribution and structure are likely to modulate the functional role of AQP5 in different regions of the lens.

Establishment and 12-month progress of the New Zealand Motor Neurone Disease Registry.

There are only limited treatments currently available for Motor Neurone Disease, each with modest benefits. However, there is a large amount of research and drug discovery currently underway worldwide. The New Zealand Motor Neurone Disease Registry was established in 2017 to facilitate participation in research and clinical trials, and to aid researchers in planning and recruitment. The NZ MND Registry is an opt in patient registry which collects demographic, contact and clinical data for those who choose to enrol. We report anonymised aggregated data from the first year's enrolment. 12th July 2018, there were 142 participants enrolled in the NZ MND Registry. Participant sex distribution reflects the demographics reported worldwide, but ethnicity is divergent from what is seen in New Zealand overall, with an over-representation of people who identify as New Zealand European. 85.5% of participants are diagnosed with sporadic MND and 6.1% with familial MND. The remainder were participants who have not been diagnosed but have a family history, or positive genetic test for a MND-causing mutation. Levels of disability are reported using ALSFRS-R scores, and show that the majority of participants are within the higher range of the scale. The registry has facilitated entry of patients into three studies to date. The establishment of the NZ MND Registry illustrates a swift launch of a rare disease patient registry. The role of patient registries is an ever changing one, but with clear utility at every point of along the pathway to drug discovery.

Confocal microscopy reveals zones of membrane remodeling in the outer cortex of the human lens.

PURPOSE: To optimize fixation, sectioning, and immunolabeling protocols to map the morphology of the human lens with confocal microscopy. METHODS: Transparent human lenses were fixed in 0.75% paraformaldehyde for 24 hours, cut in half, and fixed for another 24 hours. Lenses were cryoprotected, sectioned, and labeled with wheat germ agglutinin, aquaporin-0 antibodies, Hoechst, or toluidine blue. Before fixation, some lenses were incubated in an extracellular marker dye, Texas Red-dextran. Labeled sections were imaged with a confocal microscope. Overlapping images were tiled together to form a continuous image montage of fiber cell morphology from the periphery to the lens center. RESULTS: Fiber cell morphologies were identical with those previously described by electron microscopy and allowed immunohistochemistry to be performed for a representative membrane protein, aquaporin-0. Sectioning protocols enabled the epithelium and outer cortex to be retained, leading to the identification of two unique morphologic zones. In the first zone, an age-independent compaction of nucleated fiber cells and the initiation of extensive membrane remodeling occur. In the second zone, fiber cells retain their interdigitations but lose their nuclei, exhibit a distorted shape, and are less compressed. These zones are followed by the adult nucleus, which is marked by extensive compaction and a restriction of the extracellular space to the diffusion of Texas Red-dextran. CONCLUSIONS: The authors have developed sectioning and imaging protocols to capture differentiation-dependent changes in fiber cell morphology and protein expression throughout the human lens. Results reveal that differentiating fiber cells undergo extensive membrane remodeling before their internalization into the adult nucleus.