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Suppressed retinal degeneration in aged wild type and APPswe/PS1ΔE9 mice by bone marrow transplantation.

Yang Y, Shiao C, Hemingway JF, Jorstad NL, Shalloway BR, Chang R, Keene CD - PLoS ONE (2013)

Bottom Line: BMT resulted in near complete replacement of host retinal microglia with BMT-derived cells and normalized total AD retinal microglia to non-transplanted wt levels.Interestingly, aged wt BMT recipients also had significantly more neurons (25.4%) compared with non-transplanted aged wt controls.We found increased MHC class II expression in BMT-derived microglia and decreased oxidative damage in retinal ganglion cell layer neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Washington, Seattle, Washington, USA.

ABSTRACT
Alzheimer's disease (AD) is an age-related condition characterized by accumulation of neurotoxic amyloid β peptides (Aβ) in brain and retina. Because bone marrow transplantation (BMT) results in decreased cerebral Aβ in experimental AD, we hypothesized that BMT would mitigate retinal neurotoxicity through decreased retinal Aβ. To test this, we performed BMT in APPswe/PS1ΔE9 double transgenic mice using green fluorescent protein expressing wild type (wt) mice as marrow donors. We first examined retinas from control, non-transplanted, aged AD mice and found a two-fold increase in microglia compared with wt mice, prominent inner retinal Aβ and paired helical filament-tau, and decreased retinal ganglion cell layer neurons. BMT resulted in near complete replacement of host retinal microglia with BMT-derived cells and normalized total AD retinal microglia to non-transplanted wt levels. Aβ and paired helical filament-tau were reduced (61.0% and 44.1% respectively) in BMT-recipient AD mice, which had 20.8% more retinal ganglion cell layer neurons than non-transplanted AD controls. Interestingly, aged wt BMT recipients also had significantly more neurons (25.4%) compared with non-transplanted aged wt controls. Quantitation of retinal ganglion cell layer neurons in young mice confirmed age-related retinal degeneration was mitigated by BMT. We found increased MHC class II expression in BMT-derived microglia and decreased oxidative damage in retinal ganglion cell layer neurons. Thus, BMT is neuroprotective in age-related as well as AD-related retinal degeneration, and may be a result of alterations in innate immune function and oxidative stress in BMT recipient mice.

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Increased microglia density in experimental AD is mitigated by BMT.A: Representative retinal cryosections from wt (left) and APPswe-PS1ΔE9 mice (right) were stained with anti-Iba-1 antibody and visualized with Cy3-conjugated secondary antibody. Ramified microglia were primarily identified in ganglion cell layer (gcl), inner plexiform layer (ipl) and outer plexiform layer (opl) in wt and APPswe-PS1ΔE9 retinas. B: Unbiased stereologic analysis revealed increased microglia density in control (untreated) APPswe-PS1ΔE9 retina compared with wt control mice (*P<0.05, n = 7–9, student's t test). C: Average Iba-1+ microglia density in the different retinal layers. Significantly higher numbers of Iba-1+ microglia were noted in gcl, ipl and opl in APPswe-PS1ΔE9 mice (*P<0.05, ***P<0.001, n = 7–9, two-way ANOVA followed by Bonferroni post test.) Confocal images from wt (D) and APPswe-PS1ΔE9 (E) retinas immunostained with Iba-1 (red) demonstrate that BM-derived GFP+ cells (green) exhibited ramified microglia morphology and had near-uniform expression of Iba-1. In both wt and APPswe-PS1ΔE9 BMT recipient mice, host microglia were almost completely replaced with BM-derived cells. F: Unbiased stereologic quantitation of retinal microglia engraftment revealed 91.2±4.0% of wt and 73.2±16.0% of APPswe-PS1ΔE9 Iba-1+ microglia were BM derived (GFP+). G: Microglia density in retina of wt BMT recipients was not different from non-transplanted wt mice, but BMT in APPswe-PS1ΔE9 mice normalized microglia density to wt levels. Data are percent of wt Iba-1+ cells/mm2 in non-transplanted APPswe-PS1ΔE9 untreated mice (AD no Tx) or APPswe-PS1ΔE9 and wt BMT recipients (*P<0.05, **P<0.01, n = 6–10, one-way ANOVA followed by Bonferroni post test). Scale bars  = 30 μm.
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pone-0064246-g002: Increased microglia density in experimental AD is mitigated by BMT.A: Representative retinal cryosections from wt (left) and APPswe-PS1ΔE9 mice (right) were stained with anti-Iba-1 antibody and visualized with Cy3-conjugated secondary antibody. Ramified microglia were primarily identified in ganglion cell layer (gcl), inner plexiform layer (ipl) and outer plexiform layer (opl) in wt and APPswe-PS1ΔE9 retinas. B: Unbiased stereologic analysis revealed increased microglia density in control (untreated) APPswe-PS1ΔE9 retina compared with wt control mice (*P<0.05, n = 7–9, student's t test). C: Average Iba-1+ microglia density in the different retinal layers. Significantly higher numbers of Iba-1+ microglia were noted in gcl, ipl and opl in APPswe-PS1ΔE9 mice (*P<0.05, ***P<0.001, n = 7–9, two-way ANOVA followed by Bonferroni post test.) Confocal images from wt (D) and APPswe-PS1ΔE9 (E) retinas immunostained with Iba-1 (red) demonstrate that BM-derived GFP+ cells (green) exhibited ramified microglia morphology and had near-uniform expression of Iba-1. In both wt and APPswe-PS1ΔE9 BMT recipient mice, host microglia were almost completely replaced with BM-derived cells. F: Unbiased stereologic quantitation of retinal microglia engraftment revealed 91.2±4.0% of wt and 73.2±16.0% of APPswe-PS1ΔE9 Iba-1+ microglia were BM derived (GFP+). G: Microglia density in retina of wt BMT recipients was not different from non-transplanted wt mice, but BMT in APPswe-PS1ΔE9 mice normalized microglia density to wt levels. Data are percent of wt Iba-1+ cells/mm2 in non-transplanted APPswe-PS1ΔE9 untreated mice (AD no Tx) or APPswe-PS1ΔE9 and wt BMT recipients (*P<0.05, **P<0.01, n = 6–10, one-way ANOVA followed by Bonferroni post test). Scale bars  = 30 μm.

Mentions: Microglia are the principle innate immune effector cells in brain and retina and are implicated in Aβ-related retinal degeneration [25], [26]. We hypothesized that BMT-mediated mitigation of pathologic changes in AD retina would necessarily require engraftment of transplanted cells. However, in order to understand the effects of BMT on resident microglia, we first characterized Iba-1 immunopositive microglia in non-transplanted, aged (13-month-old) wt and APPswe-PS1ΔE9 control retina. Iba-1 is a calcium binding adaptor protein that is expressed in monocytes, macrophages and microglia. Iba-1 immunopositive cells in wt and APPswe-PS1ΔE9 retina exhibited a range of morphologies from classically ramified (small soma and multiple long delicate processes) to reactive (cytoplasmic enlargement and fewer, coarser processes) (Fig. 2A). In agreement with previously published observations, microglia in APPswe-PS1ΔE9 mice were identified in outer plexiform layer in addition to layers of inner retina normally populated with microglia [22]. Stereologic quantification of Iba-1+ cells revealed 48.5±19.9% more Iba-1+ cells in APPswe-PS1ΔE9 retina compared with wt (Fig. 2B, P<0.05, student's t test). Quantification of Iba-1+ microglia in different retinal layers demonstrated significantly more Iba-1+ cells in RGCL, inner plexiform layer and outer plexiform layer of APPswe-PS1ΔE9 compared with wt mice (Fig. 2C, *P<0.05, ***P<0.001, two-way ANOVA with Bonferroni post test).


Suppressed retinal degeneration in aged wild type and APPswe/PS1ΔE9 mice by bone marrow transplantation.

Yang Y, Shiao C, Hemingway JF, Jorstad NL, Shalloway BR, Chang R, Keene CD - PLoS ONE (2013)

Increased microglia density in experimental AD is mitigated by BMT.A: Representative retinal cryosections from wt (left) and APPswe-PS1ΔE9 mice (right) were stained with anti-Iba-1 antibody and visualized with Cy3-conjugated secondary antibody. Ramified microglia were primarily identified in ganglion cell layer (gcl), inner plexiform layer (ipl) and outer plexiform layer (opl) in wt and APPswe-PS1ΔE9 retinas. B: Unbiased stereologic analysis revealed increased microglia density in control (untreated) APPswe-PS1ΔE9 retina compared with wt control mice (*P<0.05, n = 7–9, student's t test). C: Average Iba-1+ microglia density in the different retinal layers. Significantly higher numbers of Iba-1+ microglia were noted in gcl, ipl and opl in APPswe-PS1ΔE9 mice (*P<0.05, ***P<0.001, n = 7–9, two-way ANOVA followed by Bonferroni post test.) Confocal images from wt (D) and APPswe-PS1ΔE9 (E) retinas immunostained with Iba-1 (red) demonstrate that BM-derived GFP+ cells (green) exhibited ramified microglia morphology and had near-uniform expression of Iba-1. In both wt and APPswe-PS1ΔE9 BMT recipient mice, host microglia were almost completely replaced with BM-derived cells. F: Unbiased stereologic quantitation of retinal microglia engraftment revealed 91.2±4.0% of wt and 73.2±16.0% of APPswe-PS1ΔE9 Iba-1+ microglia were BM derived (GFP+). G: Microglia density in retina of wt BMT recipients was not different from non-transplanted wt mice, but BMT in APPswe-PS1ΔE9 mice normalized microglia density to wt levels. Data are percent of wt Iba-1+ cells/mm2 in non-transplanted APPswe-PS1ΔE9 untreated mice (AD no Tx) or APPswe-PS1ΔE9 and wt BMT recipients (*P<0.05, **P<0.01, n = 6–10, one-way ANOVA followed by Bonferroni post test). Scale bars  = 30 μm.
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Related In: Results  -  Collection

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pone-0064246-g002: Increased microglia density in experimental AD is mitigated by BMT.A: Representative retinal cryosections from wt (left) and APPswe-PS1ΔE9 mice (right) were stained with anti-Iba-1 antibody and visualized with Cy3-conjugated secondary antibody. Ramified microglia were primarily identified in ganglion cell layer (gcl), inner plexiform layer (ipl) and outer plexiform layer (opl) in wt and APPswe-PS1ΔE9 retinas. B: Unbiased stereologic analysis revealed increased microglia density in control (untreated) APPswe-PS1ΔE9 retina compared with wt control mice (*P<0.05, n = 7–9, student's t test). C: Average Iba-1+ microglia density in the different retinal layers. Significantly higher numbers of Iba-1+ microglia were noted in gcl, ipl and opl in APPswe-PS1ΔE9 mice (*P<0.05, ***P<0.001, n = 7–9, two-way ANOVA followed by Bonferroni post test.) Confocal images from wt (D) and APPswe-PS1ΔE9 (E) retinas immunostained with Iba-1 (red) demonstrate that BM-derived GFP+ cells (green) exhibited ramified microglia morphology and had near-uniform expression of Iba-1. In both wt and APPswe-PS1ΔE9 BMT recipient mice, host microglia were almost completely replaced with BM-derived cells. F: Unbiased stereologic quantitation of retinal microglia engraftment revealed 91.2±4.0% of wt and 73.2±16.0% of APPswe-PS1ΔE9 Iba-1+ microglia were BM derived (GFP+). G: Microglia density in retina of wt BMT recipients was not different from non-transplanted wt mice, but BMT in APPswe-PS1ΔE9 mice normalized microglia density to wt levels. Data are percent of wt Iba-1+ cells/mm2 in non-transplanted APPswe-PS1ΔE9 untreated mice (AD no Tx) or APPswe-PS1ΔE9 and wt BMT recipients (*P<0.05, **P<0.01, n = 6–10, one-way ANOVA followed by Bonferroni post test). Scale bars  = 30 μm.
Mentions: Microglia are the principle innate immune effector cells in brain and retina and are implicated in Aβ-related retinal degeneration [25], [26]. We hypothesized that BMT-mediated mitigation of pathologic changes in AD retina would necessarily require engraftment of transplanted cells. However, in order to understand the effects of BMT on resident microglia, we first characterized Iba-1 immunopositive microglia in non-transplanted, aged (13-month-old) wt and APPswe-PS1ΔE9 control retina. Iba-1 is a calcium binding adaptor protein that is expressed in monocytes, macrophages and microglia. Iba-1 immunopositive cells in wt and APPswe-PS1ΔE9 retina exhibited a range of morphologies from classically ramified (small soma and multiple long delicate processes) to reactive (cytoplasmic enlargement and fewer, coarser processes) (Fig. 2A). In agreement with previously published observations, microglia in APPswe-PS1ΔE9 mice were identified in outer plexiform layer in addition to layers of inner retina normally populated with microglia [22]. Stereologic quantification of Iba-1+ cells revealed 48.5±19.9% more Iba-1+ cells in APPswe-PS1ΔE9 retina compared with wt (Fig. 2B, P<0.05, student's t test). Quantification of Iba-1+ microglia in different retinal layers demonstrated significantly more Iba-1+ cells in RGCL, inner plexiform layer and outer plexiform layer of APPswe-PS1ΔE9 compared with wt mice (Fig. 2C, *P<0.05, ***P<0.001, two-way ANOVA with Bonferroni post test).

Bottom Line: BMT resulted in near complete replacement of host retinal microglia with BMT-derived cells and normalized total AD retinal microglia to non-transplanted wt levels.Interestingly, aged wt BMT recipients also had significantly more neurons (25.4%) compared with non-transplanted aged wt controls.We found increased MHC class II expression in BMT-derived microglia and decreased oxidative damage in retinal ganglion cell layer neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Washington, Seattle, Washington, USA.

ABSTRACT
Alzheimer's disease (AD) is an age-related condition characterized by accumulation of neurotoxic amyloid β peptides (Aβ) in brain and retina. Because bone marrow transplantation (BMT) results in decreased cerebral Aβ in experimental AD, we hypothesized that BMT would mitigate retinal neurotoxicity through decreased retinal Aβ. To test this, we performed BMT in APPswe/PS1ΔE9 double transgenic mice using green fluorescent protein expressing wild type (wt) mice as marrow donors. We first examined retinas from control, non-transplanted, aged AD mice and found a two-fold increase in microglia compared with wt mice, prominent inner retinal Aβ and paired helical filament-tau, and decreased retinal ganglion cell layer neurons. BMT resulted in near complete replacement of host retinal microglia with BMT-derived cells and normalized total AD retinal microglia to non-transplanted wt levels. Aβ and paired helical filament-tau were reduced (61.0% and 44.1% respectively) in BMT-recipient AD mice, which had 20.8% more retinal ganglion cell layer neurons than non-transplanted AD controls. Interestingly, aged wt BMT recipients also had significantly more neurons (25.4%) compared with non-transplanted aged wt controls. Quantitation of retinal ganglion cell layer neurons in young mice confirmed age-related retinal degeneration was mitigated by BMT. We found increased MHC class II expression in BMT-derived microglia and decreased oxidative damage in retinal ganglion cell layer neurons. Thus, BMT is neuroprotective in age-related as well as AD-related retinal degeneration, and may be a result of alterations in innate immune function and oxidative stress in BMT recipient mice.

Show MeSH
Related in: MedlinePlus