Characterization of the antigenic phenotype of αB-crystallin-expressing peripapillary glial cells in the developing chick retina

Abstract

Radial glia are transdifferentiated into astrocytes within the developing brain and spinal cord. The neural retina contains Müller cells, which are retinal radial glia. Some of the cells that surround the optic nerve head among Müller cells in the chicken retina are called peripapillary glial cells (PPGCs). PPGCs express different molecules compared to typical Müller cells. However, an antigenic PPGC phenotype has not yet been clearly established. In this study, we classified the antigenic PPGC phenotypes and identified the differentiation stages of these cells. At embryonic day (E)8, αB-crystallin-positive PPGCs had a bipolar shape with long processes that traversed entire layers of the retina. Pax2 and vimentin were expressed in αB-crystallin-positive PPGCs. Glial fibrillary acidic protein (GFAP) immunoreactivity was not observed in PPGCs. At E18, αB-crystallin immunoreactivity disappeared from the vitread processes of PPGCs. However, the PPGC cell bodies and ventricular processes contained αB-crystallin protein, and the PPGCs retained the same Pax2-positive/vimentin-positive/GFAP-negative profile as that seen at E8. At post-hatch day 120, αB-crystallin and Pax2 immunoreactivity was not observed, but vimentin and GFAP expression was clearly observed in the presumptive location of the PPGCs. Furthermore, these two proteins overlapped within that location. Considering that vimentin expression is prolonged until the post-hatching period in chicken brain, these findings suggest that Pax2-negative/vimentin-positive/GFAP-positive PPGCs are phenotypically identical to mature astrocytes in this avian species.

Impact of diabetes on alpha-crystallins and other heat shock proteins in the eye

“…Despite the previously described regulatory mechanisms and their disruptive effect, two recent studies demonstrated that systemic administration of alphaB-crystallin could rescue cells in models of stroke and retinal ischemia [80,81]. Administration of alphaBcrystallin 12 h after an experimentally induced stroke was shown to result in both reduced stroke volume and inflammatory cytokines associated with stroke pathology [16,80]. With a similar approach, Pangratz-Fuehrer et al demonstrated that alphaB-crystallin administration further enhanced the protective adaptive response following anterior ischemic optic neuropathy by decreasing microglial activation and promoting optic nerve oligodendrocyte survival [81].…”

“…Like other heat shock proteins, crystallin expression may be instrumental in retinal development. A subpopulation of Müller cells, called peripapillary glial cells (PPGCs), which are located adjacent to the optic nerve head (ONH), expresses alphaB-crystallin during retinal development [16]. AlphaB-crystallin, unlike alphaA-crystallin, is also specifically expressed in the retinal pigment epithelium at specific stages during rat retinal development [17].…”

Metformin treatment confers protection of the optic nerve following photoreceptor degeneration

“…Also, Metformin attenuated oxidative stress with corresponding induction of antioxidative defenses in oligodendrocytes exposed to cytokines via AMPK activation [ 5 , 22 , 23 ]. Moreover, Kim et al [ 24 ] reported that αB-crystallin protein was expressed in peripapillary glial cells and some oligodendrocytes. The crystallin proteins which might be upregulated by metformin were proved to be protective in nerve injury [ 25 ].…”

Immunohistological Study of Monkey Foveal Retina

“…In primate retinas, astrocytes display immunostaining for GFAP, yet Müller cells do not, except those that are undifferentiated Müller cell during the fetal stage and reactive Müller cells that appear after tissue injury 29 . On the other hand, astrocytes in the optic disc and around the peripapillary blood vessels in the nerve fiber layer are known to display strong immunostaining for GFAP 30 . Our findings indicated that the inner layer of the foveola ( i.e ., the inner-half layer of the Müller cell cone) showed a GFAP staining pattern that well-resembled that displayed by astrocytes in the peripapillary area.…”