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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

Analysis of the distribution pattern of microglial cells. (A-C) Drawings of microglial cell bodies labeled with immunoperoxidase in a representative area of the retina of a SD (A), untreated P23H (B) and tauroursodeoxycholic acid (TUDCA)-treated P23H rat (C). The localization of microglial cells in each of the retinal layers studied has been specified: GCL, red; IPL, green; OPL, blue. All images were collected from the medial area of the retina, in the superior quadrant. (D-F) Histograms of the nearest neighbors analysis in the OPL, IPL and GCL of SD (D), untreated P23H (E) and TUDCA-treated P23H rats (F). The solid line indicates the Gaussian function fitted to the data. The nearest neighbors analysis of a random pattern of the same density and standard deviation has been included for comparisons (dotted line). GCL, ganglion cell layer; IPL, inner plexiform layer; OPL, outer plexiform layer. Scale bar: 500 μm.
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Fig5: Analysis of the distribution pattern of microglial cells. (A-C) Drawings of microglial cell bodies labeled with immunoperoxidase in a representative area of the retina of a SD (A), untreated P23H (B) and tauroursodeoxycholic acid (TUDCA)-treated P23H rat (C). The localization of microglial cells in each of the retinal layers studied has been specified: GCL, red; IPL, green; OPL, blue. All images were collected from the medial area of the retina, in the superior quadrant. (D-F) Histograms of the nearest neighbors analysis in the OPL, IPL and GCL of SD (D), untreated P23H (E) and TUDCA-treated P23H rats (F). The solid line indicates the Gaussian function fitted to the data. The nearest neighbors analysis of a random pattern of the same density and standard deviation has been included for comparisons (dotted line). GCL, ganglion cell layer; IPL, inner plexiform layer; OPL, outer plexiform layer. Scale bar: 500 μm.

Mentions: Figure 5 shows representative drawings of the CD11b-positive cells found in the medial area of the retina (superior quadrant) of a SD, untreated P23H and TUDCA-treated P23H rat, differentiating microglial cells located in the GCL, IPL and OPL. According to data obtained in the quantitative analysis shown in Figure 4, we can see that TUDCA-treated P23H rat retinas (Figure 5C) had a density of microglial cells intermediate between the one found in SD rats (Figure 5A) and observed in untreated P23H rats (Figure 5B), indicating a significant effect of TUDCA reducing the relative number of microglial cells in all retinal layers. Representative drawings in Figure 5 (A-C) also show that, regardless of the microglia density, microglial cells are regularly distributed within each retinal layer in SD, untreated P23H and TUDCA-treated P23H rats. As we can see in Figure 5 (D-F) the distribution patterns of microglial cells in the GCL, IPL and OPL, obtained by measuring the distances to the nearest neighbors of each microglial cell, show a Gaussian form and are symmetric around the mean (Figure 5D-F, solid line). As we can see in the figure, these histograms cannot be described by the nearest neighbors analysis of random patterns of the same density and standard deviation (Figure 5D-F, dotted line). It indicates that the distances to the nearest neighbors are uniform, and that microglial cells are arranged in a regular mosaic and are not distributed at random.Figure 9


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

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

Analysis of the distribution pattern of microglial cells. (A-C) Drawings of microglial cell bodies labeled with immunoperoxidase in a representative area of the retina of a SD (A), untreated P23H (B) and tauroursodeoxycholic acid (TUDCA)-treated P23H rat (C). The localization of microglial cells in each of the retinal layers studied has been specified: GCL, red; IPL, green; OPL, blue. All images were collected from the medial area of the retina, in the superior quadrant. (D-F) Histograms of the nearest neighbors analysis in the OPL, IPL and GCL of SD (D), untreated P23H (E) and TUDCA-treated P23H rats (F). The solid line indicates the Gaussian function fitted to the data. The nearest neighbors analysis of a random pattern of the same density and standard deviation has been included for comparisons (dotted line). GCL, ganglion cell layer; IPL, inner plexiform layer; OPL, outer plexiform layer. Scale bar: 500 μm.
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Fig5: Analysis of the distribution pattern of microglial cells. (A-C) Drawings of microglial cell bodies labeled with immunoperoxidase in a representative area of the retina of a SD (A), untreated P23H (B) and tauroursodeoxycholic acid (TUDCA)-treated P23H rat (C). The localization of microglial cells in each of the retinal layers studied has been specified: GCL, red; IPL, green; OPL, blue. All images were collected from the medial area of the retina, in the superior quadrant. (D-F) Histograms of the nearest neighbors analysis in the OPL, IPL and GCL of SD (D), untreated P23H (E) and TUDCA-treated P23H rats (F). The solid line indicates the Gaussian function fitted to the data. The nearest neighbors analysis of a random pattern of the same density and standard deviation has been included for comparisons (dotted line). GCL, ganglion cell layer; IPL, inner plexiform layer; OPL, outer plexiform layer. Scale bar: 500 μm.
Mentions: Figure 5 shows representative drawings of the CD11b-positive cells found in the medial area of the retina (superior quadrant) of a SD, untreated P23H and TUDCA-treated P23H rat, differentiating microglial cells located in the GCL, IPL and OPL. According to data obtained in the quantitative analysis shown in Figure 4, we can see that TUDCA-treated P23H rat retinas (Figure 5C) had a density of microglial cells intermediate between the one found in SD rats (Figure 5A) and observed in untreated P23H rats (Figure 5B), indicating a significant effect of TUDCA reducing the relative number of microglial cells in all retinal layers. Representative drawings in Figure 5 (A-C) also show that, regardless of the microglia density, microglial cells are regularly distributed within each retinal layer in SD, untreated P23H and TUDCA-treated P23H rats. As we can see in Figure 5 (D-F) the distribution patterns of microglial cells in the GCL, IPL and OPL, obtained by measuring the distances to the nearest neighbors of each microglial cell, show a Gaussian form and are symmetric around the mean (Figure 5D-F, solid line). As we can see in the figure, these histograms cannot be described by the nearest neighbors analysis of random patterns of the same density and standard deviation (Figure 5D-F, dotted line). It indicates that the distances to the nearest neighbors are uniform, and that microglial cells are arranged in a regular mosaic and are not distributed at random.Figure 9

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