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Microglia activation in a model of retinal degeneration and TUDCA neuroprotective effects.

Noailles A, Fernández-Sánchez L, Lax P, Cuenca N - J Neuroinflammation (2014)

Bottom Line: In the P23H rat retina, microglial cells increased in number in all layers compared with control SD rat retinas, preserving the regular mosaic distribution.In addition, a large number of amoeboid CD11b-positive cells were observed in the P23H rat retina, even in the subretinal space.Retinas of TUDCA-treated P23H animals exhibited lower microglial cell number in all layers and absence of microglial cells in the subretinal space.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Retinitis pigmentosa is a heterogeneous group of inherited neurodegenerative retinal disorders characterized by a progressive peripheral vision loss and night vision difficulties, subsequently leading to central vision impairment. Chronic microglia activation is associated with various neurodegenerative diseases including retinitis pigmentosa. The objective of this study was to quantify microglia activation in the retina of P23H rats, an animal model of retinitis pigmentosa, and to evaluate the therapeutic effects of TUDCA (tauroursodeoxycholic acid), which has been described as a neuroprotective compound.

Methods: For this study, homozygous P23H line 3 and Sprague-Dawley (SD) rats were injected weekly with TUDCA (500 mg/kg, ip) or vehicle (saline) from 20 days to 4 months old. Vertical retinal sections and whole-mount retinas were immunostained for specific markers of microglial cells (anti-CD11b, anti-Iba1 and anti-MHC-II). Microglial cell morphology was analyzed and the number of retinal microglial was quantified.

Results: Microglial cells in the SD rat retinas were arranged in regular mosaics homogenously distributed within the plexiform and ganglion cell layers. In the P23H rat retina, microglial cells increased in number in all layers compared with control SD rat retinas, preserving the regular mosaic distribution. In addition, a large number of amoeboid CD11b-positive cells were observed in the P23H rat retina, even in the subretinal space. Retinas of TUDCA-treated P23H animals exhibited lower microglial cell number in all layers and absence of microglial cells in the subretinal space.

Conclusions: These results report novel TUDCA anti-inflammatory actions, with potential therapeutic implications for neurodegenerative diseases, including retinitis pigmentosa.

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Related in: MedlinePlus

Number and distribution of macrophages in the ganglion cell layer (GCL). (A-C) Representative images of whole-mount rat retinas from a SD (A), untreated P23H (B) and tauroursodeoxycholic acid (TUDCA)-treated P23H rat (C) labeled with immunoperoxidase. (D, E) Density of macrophages, expressed as number of cells per mm2, in each of 12 representative regions in each retina: 6 equidistantly arranged on the superior-inferior axis of the retina (D) and 6 disposed on the temporal-nasal axis (E). The scheme in the margin of each panel represents the position in the retina of each representative region analyzed. Scale bar: 40 μm.
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Fig11: Number and distribution of macrophages in the ganglion cell layer (GCL). (A-C) Representative images of whole-mount rat retinas from a SD (A), untreated P23H (B) and tauroursodeoxycholic acid (TUDCA)-treated P23H rat (C) labeled with immunoperoxidase. (D, E) Density of macrophages, expressed as number of cells per mm2, in each of 12 representative regions in each retina: 6 equidistantly arranged on the superior-inferior axis of the retina (D) and 6 disposed on the temporal-nasal axis (E). The scheme in the margin of each panel represents the position in the retina of each representative region analyzed. Scale bar: 40 μm.

Mentions: Microglial activation was assessed in SD, untreated P23H and TUDCA-treated P23H rats by analyzing vertical retinal sections immunostained with Iba1, a constitutively expressed microglial specific marker, and MHC-II, a marker that is frequently present on activated microglia. The total number of microglial cells expressing one or both markers was counted. As we can see in Figure 9, MHC-II-negative cells labeled with anti-Iba1 antibody (Iba1+/MHC-II−) had the typical appearance of resting microglia, while MHC-II-positive cells showed morphologic features of activated microglia; thus proving that MHC-II expression is associated to microglial activation. In SD rat retinas, all Iba1-positive cells found showed morphologic features of resting microglia and were not labeled by anti-MHC-II antibody (Iba1+/MHC-II−, Figure 9A-C and Figure 10B). In the retinas of untreated P23H rats, microglia density was significantly higher than the one observed in the SD rats (183%; ANOVA, Bonferroni’s test, P <0.001; Figure 9D-E and Figure 10A). Moreover, a high proportion of microglial cells in untreated P23H rat retinas were MHC-II-positive (43%; Figure 10B). Finally, a small group of MHC-II-positive cells found in untreated P23H rat retinas was not labeled by anti-Iba1 antibody (5%; Iba1−/MHC-II+; Figure 10B). In TUDCA-treated P23H rats, microglia density was similar to the one observed in the SD rats (108%), and significantly smaller than that found in untreated P23H rats (59%; ANOVA, Bonferroni’s test, P <0.001; Figure 9G-I and Figure 10A). The relative number of MHC-II-positive cells not labeled by anti-Iba1 antibody in TUDCA-treated P23H rats was also lower than in untreated P23H rats (27.8%; Iba1−/MHC-II+; Figure 10B).Figure 10


Microglia activation in a model of retinal degeneration and TUDCA neuroprotective effects.

Noailles A, Fernández-Sánchez L, Lax P, Cuenca N - J Neuroinflammation (2014)

Number and distribution of macrophages in the ganglion cell layer (GCL). (A-C) Representative images of whole-mount rat retinas from a SD (A), untreated P23H (B) and tauroursodeoxycholic acid (TUDCA)-treated P23H rat (C) labeled with immunoperoxidase. (D, E) Density of macrophages, expressed as number of cells per mm2, in each of 12 representative regions in each retina: 6 equidistantly arranged on the superior-inferior axis of the retina (D) and 6 disposed on the temporal-nasal axis (E). The scheme in the margin of each panel represents the position in the retina of each representative region analyzed. Scale bar: 40 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Fig11: Number and distribution of macrophages in the ganglion cell layer (GCL). (A-C) Representative images of whole-mount rat retinas from a SD (A), untreated P23H (B) and tauroursodeoxycholic acid (TUDCA)-treated P23H rat (C) labeled with immunoperoxidase. (D, E) Density of macrophages, expressed as number of cells per mm2, in each of 12 representative regions in each retina: 6 equidistantly arranged on the superior-inferior axis of the retina (D) and 6 disposed on the temporal-nasal axis (E). The scheme in the margin of each panel represents the position in the retina of each representative region analyzed. Scale bar: 40 μm.
Mentions: Microglial activation was assessed in SD, untreated P23H and TUDCA-treated P23H rats by analyzing vertical retinal sections immunostained with Iba1, a constitutively expressed microglial specific marker, and MHC-II, a marker that is frequently present on activated microglia. The total number of microglial cells expressing one or both markers was counted. As we can see in Figure 9, MHC-II-negative cells labeled with anti-Iba1 antibody (Iba1+/MHC-II−) had the typical appearance of resting microglia, while MHC-II-positive cells showed morphologic features of activated microglia; thus proving that MHC-II expression is associated to microglial activation. In SD rat retinas, all Iba1-positive cells found showed morphologic features of resting microglia and were not labeled by anti-MHC-II antibody (Iba1+/MHC-II−, Figure 9A-C and Figure 10B). In the retinas of untreated P23H rats, microglia density was significantly higher than the one observed in the SD rats (183%; ANOVA, Bonferroni’s test, P <0.001; Figure 9D-E and Figure 10A). Moreover, a high proportion of microglial cells in untreated P23H rat retinas were MHC-II-positive (43%; Figure 10B). Finally, a small group of MHC-II-positive cells found in untreated P23H rat retinas was not labeled by anti-Iba1 antibody (5%; Iba1−/MHC-II+; Figure 10B). In TUDCA-treated P23H rats, microglia density was similar to the one observed in the SD rats (108%), and significantly smaller than that found in untreated P23H rats (59%; ANOVA, Bonferroni’s test, P <0.001; Figure 9G-I and Figure 10A). The relative number of MHC-II-positive cells not labeled by anti-Iba1 antibody in TUDCA-treated P23H rats was also lower than in untreated P23H rats (27.8%; Iba1−/MHC-II+; Figure 10B).Figure 10

Bottom Line: In the P23H rat retina, microglial cells increased in number in all layers compared with control SD rat retinas, preserving the regular mosaic distribution.In addition, a large number of amoeboid CD11b-positive cells were observed in the P23H rat retina, even in the subretinal space.Retinas of TUDCA-treated P23H animals exhibited lower microglial cell number in all layers and absence of microglial cells in the subretinal space.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Retinitis pigmentosa is a heterogeneous group of inherited neurodegenerative retinal disorders characterized by a progressive peripheral vision loss and night vision difficulties, subsequently leading to central vision impairment. Chronic microglia activation is associated with various neurodegenerative diseases including retinitis pigmentosa. The objective of this study was to quantify microglia activation in the retina of P23H rats, an animal model of retinitis pigmentosa, and to evaluate the therapeutic effects of TUDCA (tauroursodeoxycholic acid), which has been described as a neuroprotective compound.

Methods: For this study, homozygous P23H line 3 and Sprague-Dawley (SD) rats were injected weekly with TUDCA (500 mg/kg, ip) or vehicle (saline) from 20 days to 4 months old. Vertical retinal sections and whole-mount retinas were immunostained for specific markers of microglial cells (anti-CD11b, anti-Iba1 and anti-MHC-II). Microglial cell morphology was analyzed and the number of retinal microglial was quantified.

Results: Microglial cells in the SD rat retinas were arranged in regular mosaics homogenously distributed within the plexiform and ganglion cell layers. In the P23H rat retina, microglial cells increased in number in all layers compared with control SD rat retinas, preserving the regular mosaic distribution. In addition, a large number of amoeboid CD11b-positive cells were observed in the P23H rat retina, even in the subretinal space. Retinas of TUDCA-treated P23H animals exhibited lower microglial cell number in all layers and absence of microglial cells in the subretinal space.

Conclusions: These results report novel TUDCA anti-inflammatory actions, with potential therapeutic implications for neurodegenerative diseases, including retinitis pigmentosa.

Show MeSH
Related in: MedlinePlus