Abstract
Purpose:
Astrocytes provide support to retinal neurons and are fundamental for the maintenance of normal retinal function. They are important for energetic metabolism, remove the neurotransmitters and are crucial for maintaining the blood-retinal barrier. It has been suggested that astrocytes may play an important role in glaucoma disease. The aim of this study was to evaluate the function and morphology of astrocytes in DBA/2J aging mice.
Methods:
DBA/2J mice were studied at 3, 8 and 16 months, and C57BL/6 mice were used as age-matched controls. Astrocytes responsiveness was evaluated on whole-mount retinas using the Ca2+ indicator dye fluo-4 AM, and measuring the Ca2+ transients evoked by pressure application of ATP. Whole-mount retinas were immunostained against GFAP, to visualize astrocytes and Müller gliosis; Collagen IV, to stain vessels; Connexin 43 for gap junctions and Brn3a for retinal ganglion cells, to study the astrocytes network and their relationship with ganglion cells and vessels.
Results:
GFAP and Brn3a immunostaining showed, in DBA/2J retinas, a progressive fall in GFAP immunofluorescence associated to ganglion cell death. The astrocytes morphology and their relationship with vessels and/or other astrocytes revealed morphological changes in astrocytes, especially in the end-feet, getting worse with aging. Müller cells gliosis was detected by expression of GFAP. Connexin 43 staining showed loss of gap junctions between astrocytes and vessels. Ca2+ image analysis showed no statistical differences regarding astrocytes response to ATP at 3 and 8 months when comparing DBA/2J and C57BL/6 mice.
Conclusions:
The immunostaining could indicate that there is a decoupling of gap junctions, which may accelerate the pathology of the disease in this mouse model. However, the astrocytes in DBA/2J retina did not present alterations in the propagation of Ca2+ waves through extracellular messenger ATP. More studies are necessary to clear up astrocytes implications in the physiopathology of glaucoma disease.
Keywords: 429 astrocyte •
691 retina: proximal (bipolar, amacrine, and ganglion cells) •
695 retinal degenerations: cell biology