Progressive ganglion cell loss and optic nerve degeneration in DBA/2J mice is variable and asymmetric

Abstract

Background: Glaucoma is a chronic neurodegenerative disease of the retina, characterized by the degeneration of axons in the optic nerve and retinal ganglion cell apoptosis. DBA/2J inbred mice develop chronic hereditary glaucoma and are an important model system to study the molecular mechanisms underlying this disease and novel therapeutic interventions designed to attenuate the loss of retinal ganglion cells. Although the genetics of this disease in these mice are well characterized, the etiology of its progression, particularly with respect to retinal degeneration, is not. We have used two separate labeling techniques, post-mortem DiI labeling of axons and ganglion cell-specific expression of the βGeo reporter gene, to evaluate the time course of optic nerve degeneration and ganglion cell loss, respectively, in aging mice.

Early microglia activation in a mouse model of chronic glaucoma

“…Astrocyte and Müller glia reactivity is associated with D2 glaucoma progression, and recent research has focused on the role of glia in the initial alterations detected in the ONH and OL (Howell et al, 2007; Inman and Horner, 2007; Jakobs et al, 2005; Schlamp et al, 2006; Soto et al, 2008). Since the potential triggers for gliosis are signals from RGCs and/or between glia, we assessed the spatial relationship of microglia to other glial populations.…”

“…Since the earliest signs of RGC axonal damage localize to the unmyelinated laminar region in D2 optic nerves immediately distal to the ONH and retina (Howell et al, 2007; Soto et al, 2008), we sought to define whether microglia localized in these regions undergo changes indicative of cell activation and/or redistribution. We compared both cell density and signs of activation in D2 mice starting at prepathological ages (1 month) through ages when RGC axonal and somal pathology is known to prevail (up to 12 months; Buckingham et al, 2008; Crish et al, 2010; Howell et al, 2007a; Jakobs et al, 2005; Libby et al, 2005a,b; Reichstein et al, 2007; Schlamp et al, 2006; Soto et al, 2008). Next, we carried out identical analysis in age-matched D2G non-glaucoma mice.…”

“…Many of these studies also report concurrent alteration in RGC gene expression. Notably, RGC apoptosis and somal loss is a relatively late event (12 months; Libby et al, 2005a,b; Reichstein et al, 2007; Schlamp et al, 2006). Spatially, RGC axonal decline is first detectable in the unmyelinated portion within the ONH and nerve laminar region (Howell et al, 2007a; Soto et al, 2008).…”

“…The decline of RGCs is associated with increased astrocyte and Müller glia reactivity and slow microglia proliferation (Buckingham et al, 2007; Crish et al, 2010; Howell et al, 2007a; Inman and Horner, 2007; Jakobs et al, 2005; Libby et al, 2005; Schlamp et al, 2006; Son et al, 2010; Stevens et al, 2007). Much effort has focused on elucidating the role of glia in D2 glaucoma, mostly on the relation of astrocyte gliosis and axonopathy within the proximal optic nerve (Du et al, 2007; Howell et al, 2007; Son et al, 2010; Sun et al, 2009).…”

A new PCR-based approach for the preparation of RNA probe

“…Only the preparation of RNA probes differed in that we employed a PCR-based method using a commercially available kit instead of the conventional vector-based probe preparation. To test our approach, RNA probes were generated with the aid of primers such as rhodopsin, mGluR6, and Thy1, which are well known as unique retinal markers for, respectively, photoreceptor cells, bipolar cells, and ganglion cells [11][12][13][14], and which were used in the RT-PCR or ISH experiments of other studies [11,13,14]. Examination of the expression patterns of mRNAs clearly showed expression in all the sections hybridized with antisense probes, whereas no positive signals were detected in any sections serving as negative controls and hybridized with sense probes.…”