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. 2015 May 10:12:87.
doi: 10.1186/s12974-015-0314-8.

Aging increases microglial proliferation, delays cell migration, and decreases cortical neurogenesis after focal cerebral ischemia

Ana Moraga  1 , Jesús M Pradillo  2 , Alicia García-Culebras  3 , Sara Palma-Tortosa  4 , Ivan Ballesteros  5 , Macarena Hernández-Jiménez  6 , María A Moro  7 , Ignacio Lizasoain  8
Affiliations

Aging increases microglial proliferation, delays cell migration, and decreases cortical neurogenesis after focal cerebral ischemia

Ana Moraga et al. J Neuroinflammation. .

Abstract

Background: Aging is not just a risk factor of stroke, but it has also been associated with poor recovery. It is known that stroke-induced neurogenesis is reduced but maintained in the aged brain. However, there is no consensus on how neurogenesis is affected after stroke in aged animals. Our objective is to determine the role of aging on the process of neurogenesis after stroke.

Methods: We have studied neurogenesis by analyzing proliferation, migration, and formation of new neurons, as well as inflammatory parameters, in a model of cerebral ischemia induced by permanent occlusion of the middle cerebral artery in young- (2 to 3 months) and middle-aged mice (13 to 14 months).

Results: Aging increased both microglial proliferation, as shown by a higher number of BrdU(+) cells and BrdU/Iba1(+) cells in the ischemic boundary and neutrophil infiltration. Interestingly, aging increased the number of M1 monocytes and N1 neutrophils, consistent with pro-inflammatory phenotypes when compared with the alternative M2 and N2 phenotypes. Aging also inhibited (subventricular zone) SVZ cell proliferation by decreasing both the number of astrocyte-like type-B (prominin-1(+)/epidermal growth factor receptor (EGFR)(+)/nestin(+)/glial fibrillary acidic protein (GFAP)(+) cells) and type-C cells (prominin-1(+)/EGFR(+)/nestin(-)/Mash1(+) cells), and not affecting apoptosis, 1 day after stroke. Aging also inhibited migration of neuroblasts (DCX(+) cells), as indicated by an accumulation of neuroblasts at migratory zones 14 days after injury; consistently, aged mice presented a smaller number of differentiated interneurons (NeuN(+)/BrdU(+) and GAD67(+) cells) in the peri-infarct cortical area 14 days after stroke.

Conclusions: Our data confirm that stroke-induced neurogenesis is maintained but reduced in aged animals. Importantly, we now demonstrate that aging not only inhibits proliferation of specific SVZ cell subtypes but also blocks migration of neuroblasts to the damaged area and decreases the number of new interneurons in the cortical peri-infarct area. Thus, our results highlight the importance of using aged animals for translation to clinical studies.

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Figures

Figure 1
Figure 1
Effect of aging on infarct development. Infarct size was determined by MRI (2 days) and Nissl (7 days) after MCAO in young (2 to 3 months) and aged (13 to 14 months) mice after proximal (A) and distal (B) occlusions (see Methods). Data are mean ± SD, n = 8, *P < 0.05. MCAO, middle cerebral artery occlusion.
Figure 2
Figure 2
Effect of aging on microglial proliferation and cell infiltration. Number of BrdU+ (A) and BrdU+/Iba1+ (B) cells in the peri-infarct area (cortex) at 7 and 14 days after MCAO in young and aged mice. The number of BrdU+ and BrdU+/Iba1+ cells (microglial/macrophages cells) was quantified on digitalized confocal images (see Methods). Representative images of Iba1+ cells in the ipsilesional peri-infarct hemispheres in young and aged mice. Scale bar = 50 μm (C). MCAO, middle cerebral artery occlusion.
Figure 3
Figure 3
Effect of aging on cell infiltration. Flow cytometric analysis of brain neutrophils and monocytes in sham or ischemic mice brain 1 and 2 days after ischemia in young and aged mice (A, B). Upper: quantification of total neutrophils and monocytes. Right Lower: quantification of N1 (Ym1−) and N2 (Ym1+) neutrophils (Cd11b+, Ly6Ghi, CD45hi). Left Lower: quantification of M1 (Ym1−) and M2 (Ym1+) monocytes (Cd11b+, CD45hi, CCR2+). Data are mean ± SD, n = 6 to 8 in each group. P < 0.05.
Figure 4
Figure 4
Effect of aging on SVZ cell proliferation. (A) Number of BrdU+ cells in the SVZ at 7 and 14 days after MCAO in young and aged mice. Data are mean ± SD, n = 6 to 8. (B) Correlation between number of BrdU+ cells in SVZ at 7 days and infarct size from aged mice (n = 10). (C) Diagram with SVZ cell markers. (D) Scheme. (E) Cytometric quantification of prominin-1+/EGFR+/nestin+ cell population (right upper) and of type-B cells (GFAP+ cells; right lower). (F) Quantification of prominin-1+/EGFR+/nestin− cell population (left upper) and of type-C cells (Mash1+ cells; left lower). SVZ cells were obtained after MCAO from young and aged mice. Cell suspensions were labeled with antibodies for the different markers and analyzed by flow cytometry (see Methods for details). Data are mean ± SD, n = 6 to 8, *P < 0.05. MCAO, middle cerebral artery occlusion; EGFR, epidermal growth factor receptor; GFAP, glial fibrillary acidic protein; SVZ, subventricular zone.
Figure 5
Figure 5
Effect of aging on neuroblast migration. (A) Scheme, (B) representative images, and (C, D) number of neuroblasts (doublecortin+ DCX+ cells) in three migratory zones (Z1, Z2, Z3) at 7 and 14 days after MCAO in young and aged mice. Migratory zones were established from the SVZ (Z1) through the corpus callosum (Z2) toward the damaged area (Z3) (see Methods). Data are mean ± SD, n = 6 to 8, *P < 0.05. Scale bar = 200 μm. MCAO, middle cerebral artery occlusion.
Figure 6
Figure 6
Effect of aging on the number of new neurons in the peri-infarct cortex. (A) Representative images and (B) number of adult interneurons (BrdU+/NeuN+/GAD67+ cells) in the ipsilesional cortex at 14 days after MCAO in young and aged mice. Data are mean ± SD, n = 6-8, *P < 0.05. Scale bar = 25 μm.
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References

    1. Popa-Wagner A, Buga AM, Kokaia Z. Perturbed cellular response to brain injury during aging. Ageing Res Rev. 2011;10:71–9. doi: 10.1016/j.arr.2009.10.008. - DOI - PubMed
    1. Franceschi C, Bonafè M, Valensin S, Olivieri F, De Luca M, Ottaviani E, et al. Inflamm-aging. An evolutionary perspective on immunosenescence. Ann NY Acad Sci. 2000;908:244–54. doi: 10.1111/j.1749-6632.2000.tb06651.x. - DOI - PubMed
    1. Badan I, Buchhold B, Hamm A, Gratz M, Walker LC, Platt D, et al. Accelerated glial reactivity to stroke in aged rats correlates with reduced functional recovery. J Cereb Blood Flow Metab. 2003;23:845–54. doi: 10.1097/01.WCB.0000071883.63724.A7. - DOI - PubMed
    1. Sandhir R, Onyszchuk G, Berman NE. Exacerbated glial response in the aged mouse hippocampus following controlled cortical impact injury. Exp Neurol. 2008;213:372–80. doi: 10.1016/j.expneurol.2008.06.013. - DOI - PMC - PubMed
    1. Hamilton LK, Joppé SE, Cochard L, Fernandes KJ. Aging and neurogenesis in the adult forebrain: what we have learned and where we should go from here. Eur J Neurosci. 2013;37:1978–86. doi: 10.1111/ejn.12207. - DOI - PubMed

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