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Rumi Kawashima, Kenji Matsushita, Kohji Nishida; EXPRESSION OF AQUA/AQUAGLYCEROPORINS IN MURINE OPTIC NERVE HEAD ASTROCYTES. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2276.
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Aqua/aquaglyceroporins (AQPs) absorb small metabolites around the optic nerve head (ONH). We analyzed the expression of AQPs in the ONH astrocytes.
We studied ONH astrocytes with high glial fibrillary acidic protein (GFAP) positivity cultured from C57BL6 mice and ONH tissue. The AQP (AQP1 to 12) expression levels in mRNAs from cultured astrocytes were analyzed by reverse-transcription polymerase chain reaction (RT-PCR). Expressed AQPs (AQP 1, 4, 5, and 9) were immunostained in cultured astrocytes and ONH tissue. Whole-mount immunostaining was performed for AQP4 and AQP9 to investigate the communication between vessels and glia cells. LSM Software ZEN 2008 (Carl Zeiss MicroImaging Co., Ltd.) was used for image analysis.
RT-PCR showed cultured ONH astrocytes expressed AQP1, 5 and AQP9 strongly and AQP4 weakly. In culture, the immunostaining showed AQP1 and AQP5 in cytosol, the perinuclear area, and cell membranes and AQP9 was on cell membranes; no AQP4 was expressed. Immunostaining of tissue sections showed mainly AQP9 in ONH astrocytes and little AQP4 at the edge of the ONH on the vitreous surface and in the optic nerve astrocytes. In whole mounts, within a 75-micron radius from the ONH center, AQP9 was colocalized with GFAP; within that area AQP4 were not colocalized with GFAP. AQP9 was expressed in the cell body and processes of the astrocyte (cell body 100%; primary processes 100%; branchings 42.1%; endfeet 0% [n=10]). AQP9s on the astrocytes might have contact with surrounding nerve fiber layers. Astrocytes had endfeet on the retinal large vessels (35.70±9.91 microns [n=10]) and small vessels (7.93±1.46 microns [n=15]). No AQP9 was expressed at the endfeet of the astrocytes. AQP4 was immunostained on the large and small retinal vessels, which might be expressed at the endfeet of the retinal Müller cells.
Murine cultured ONH astrocytes expressed aquaporin and aquaglyceroporin. Some AQPs were expressed in tissue and distributed in different ways . Thus, the various distributions of each AQP might have a role in controlling homeostasis of the small metabolites in neural tissue.
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