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Morphological and Phagocytic Profile of Microglia in the Developing Rat Cerebellum(1,2,3).

Perez-Pouchoulen M, VanRyzin JW, McCarthy MM - eNeuro (2015)

Bottom Line: We found that microglial morphology changed from amoeboid to ramified during the first 3 postnatal weeks in a region specific manner.At P17 males showed an approximately twofold increase in microglia with thin processes compared with females.Our findings indicate a continuous process of microglial maturation and a nonuniform distribution of microglia in the cerebellar cortex that implicates microglia as an important cellular component of the developing cerebellum.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pharmacology, University of Maryland School of Medicine , Baltimore, Maryland 21201.

ABSTRACT
Microglia are being increasingly recognized as playing important roles in neurodevelopment. The cerebellum matures postnatally, undergoing major growth, but the role of microglia in the developing cerebellum is not well understood. Using the laboratory rat we quantified and morphologically categorized microglia throughout the vermis and across development using a design-based unbiased stereology method. We found that microglial morphology changed from amoeboid to ramified during the first 3 postnatal weeks in a region specific manner. These morphological changes were accompanied by the sudden appearance of phagocytic cups during the third postnatal week from P17 to P19, with an approximately fourfold increase compared with the first week, followed by a prompt decline at the end of the third week. The microglial phagocytic cups were significantly higher in the granular layer (∼69%) than in the molecular layer (ML; ∼31%) during a 3 d window, and present on ∼67% of microglia with thick processes and ∼33% of microglia with thin processes. Similar proportions of phagocytic cups associated to microglia with either thick or thin processes were found in the ML. We observed cell nuclei fragmentation and cleaved caspase-3 expression within some microglial phagocytic cups, presumably from dying granule neurons. At P17 males showed an approximately twofold increase in microglia with thin processes compared with females. Our findings indicate a continuous process of microglial maturation and a nonuniform distribution of microglia in the cerebellar cortex that implicates microglia as an important cellular component of the developing cerebellum.

No MeSH data available.


Related in: MedlinePlus

Frequency of phagocytosis by microglia changes by location in the cerebellar cortex across development. A, The density of phagocytic cups was higher in the ML than the GL at P12 (**p < 0.01), and P14 (*p < 0.05), but switched at P17 (***p < 0.000) and P21 (*p < 0.05), so that the GL exhibited more phagocytic cups than the ML. The highest density of phagocytic cups was found in the GL at P17 compared with P12, P14, and P21 (@p < 0.000). Scale bar, 100 µm. B, Proportion of microglia that exhibited phagocytic cups in the GL at P17: 67% of all phagocytic microglia had thick processes and 33% had thin processes. No round/amoeboid or stout microglia showed phagocytic cups. C, A difference in the density of phagocytic cups was found at younger ages (P15, **p = 0.003; P16, *p = 0.05) compared with P17, but no significant differences were found at older ages (P18, p = 0.583; P19, p = 0.615). In contrast, in the ML, the density of phagocytic cups was lower only at P19 (^p = 0.043) compared with P17. Additionally, a difference in the density of phagocytic cups between the GL and ML was found from P16 to P19 (P16, #p < 0.000; P17; +p < 0.000; P18, &p < 0.000; P19, @p < 0.000) but not at P15 (p = 0.467) (n = 6, 3 males + 3 females for each group for A, B, and C). In this experiment the density of phagocytic cups was not counted in animals at P21 but the dashed lines depict the pattern previously observed at the end of the third postnatal week in both the GL and ML (Fig. 5A). D, The diameter of microglial phagocytic cups was bigger on P17 compared with P10 (@p = 0.06; see effect size estimation in Table 2), P14 (*p < 0.000) and P21 (#p = 0.003). All data are expressed as mean ± SEM (^n = 4, 2 males + 2 females; *n = 8, 4 males + 4 females: ^P10, *P14, *P17, and *P21).
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Figure 5: Frequency of phagocytosis by microglia changes by location in the cerebellar cortex across development. A, The density of phagocytic cups was higher in the ML than the GL at P12 (**p < 0.01), and P14 (*p < 0.05), but switched at P17 (***p < 0.000) and P21 (*p < 0.05), so that the GL exhibited more phagocytic cups than the ML. The highest density of phagocytic cups was found in the GL at P17 compared with P12, P14, and P21 (@p < 0.000). Scale bar, 100 µm. B, Proportion of microglia that exhibited phagocytic cups in the GL at P17: 67% of all phagocytic microglia had thick processes and 33% had thin processes. No round/amoeboid or stout microglia showed phagocytic cups. C, A difference in the density of phagocytic cups was found at younger ages (P15, **p = 0.003; P16, *p = 0.05) compared with P17, but no significant differences were found at older ages (P18, p = 0.583; P19, p = 0.615). In contrast, in the ML, the density of phagocytic cups was lower only at P19 (^p = 0.043) compared with P17. Additionally, a difference in the density of phagocytic cups between the GL and ML was found from P16 to P19 (P16, #p < 0.000; P17; +p < 0.000; P18, &p < 0.000; P19, @p < 0.000) but not at P15 (p = 0.467) (n = 6, 3 males + 3 females for each group for A, B, and C). In this experiment the density of phagocytic cups was not counted in animals at P21 but the dashed lines depict the pattern previously observed at the end of the third postnatal week in both the GL and ML (Fig. 5A). D, The diameter of microglial phagocytic cups was bigger on P17 compared with P10 (@p = 0.06; see effect size estimation in Table 2), P14 (*p < 0.000) and P21 (#p = 0.003). All data are expressed as mean ± SEM (^n = 4, 2 males + 2 females; *n = 8, 4 males + 4 females: ^P10, *P14, *P17, and *P21).

Mentions: A significant interaction for age X cerebellar layer for phagocytic cups was also found (p < 0.000)l. Post hoc pairwise comparison revealed a higher density of phagocytic cups in the ML than the GL at younger ages (P12, p = 0.002; P14, p = 0.037). However, this pattern reversed at slightly older ages with the GL exhibiting more phagocytic cups than the ML at P17 (p < 0.000) and P21 (p = 0.046) (Fig. 5A).


Morphological and Phagocytic Profile of Microglia in the Developing Rat Cerebellum(1,2,3).

Perez-Pouchoulen M, VanRyzin JW, McCarthy MM - eNeuro (2015)

Frequency of phagocytosis by microglia changes by location in the cerebellar cortex across development. A, The density of phagocytic cups was higher in the ML than the GL at P12 (**p < 0.01), and P14 (*p < 0.05), but switched at P17 (***p < 0.000) and P21 (*p < 0.05), so that the GL exhibited more phagocytic cups than the ML. The highest density of phagocytic cups was found in the GL at P17 compared with P12, P14, and P21 (@p < 0.000). Scale bar, 100 µm. B, Proportion of microglia that exhibited phagocytic cups in the GL at P17: 67% of all phagocytic microglia had thick processes and 33% had thin processes. No round/amoeboid or stout microglia showed phagocytic cups. C, A difference in the density of phagocytic cups was found at younger ages (P15, **p = 0.003; P16, *p = 0.05) compared with P17, but no significant differences were found at older ages (P18, p = 0.583; P19, p = 0.615). In contrast, in the ML, the density of phagocytic cups was lower only at P19 (^p = 0.043) compared with P17. Additionally, a difference in the density of phagocytic cups between the GL and ML was found from P16 to P19 (P16, #p < 0.000; P17; +p < 0.000; P18, &p < 0.000; P19, @p < 0.000) but not at P15 (p = 0.467) (n = 6, 3 males + 3 females for each group for A, B, and C). In this experiment the density of phagocytic cups was not counted in animals at P21 but the dashed lines depict the pattern previously observed at the end of the third postnatal week in both the GL and ML (Fig. 5A). D, The diameter of microglial phagocytic cups was bigger on P17 compared with P10 (@p = 0.06; see effect size estimation in Table 2), P14 (*p < 0.000) and P21 (#p = 0.003). All data are expressed as mean ± SEM (^n = 4, 2 males + 2 females; *n = 8, 4 males + 4 females: ^P10, *P14, *P17, and *P21).
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Figure 5: Frequency of phagocytosis by microglia changes by location in the cerebellar cortex across development. A, The density of phagocytic cups was higher in the ML than the GL at P12 (**p < 0.01), and P14 (*p < 0.05), but switched at P17 (***p < 0.000) and P21 (*p < 0.05), so that the GL exhibited more phagocytic cups than the ML. The highest density of phagocytic cups was found in the GL at P17 compared with P12, P14, and P21 (@p < 0.000). Scale bar, 100 µm. B, Proportion of microglia that exhibited phagocytic cups in the GL at P17: 67% of all phagocytic microglia had thick processes and 33% had thin processes. No round/amoeboid or stout microglia showed phagocytic cups. C, A difference in the density of phagocytic cups was found at younger ages (P15, **p = 0.003; P16, *p = 0.05) compared with P17, but no significant differences were found at older ages (P18, p = 0.583; P19, p = 0.615). In contrast, in the ML, the density of phagocytic cups was lower only at P19 (^p = 0.043) compared with P17. Additionally, a difference in the density of phagocytic cups between the GL and ML was found from P16 to P19 (P16, #p < 0.000; P17; +p < 0.000; P18, &p < 0.000; P19, @p < 0.000) but not at P15 (p = 0.467) (n = 6, 3 males + 3 females for each group for A, B, and C). In this experiment the density of phagocytic cups was not counted in animals at P21 but the dashed lines depict the pattern previously observed at the end of the third postnatal week in both the GL and ML (Fig. 5A). D, The diameter of microglial phagocytic cups was bigger on P17 compared with P10 (@p = 0.06; see effect size estimation in Table 2), P14 (*p < 0.000) and P21 (#p = 0.003). All data are expressed as mean ± SEM (^n = 4, 2 males + 2 females; *n = 8, 4 males + 4 females: ^P10, *P14, *P17, and *P21).
Mentions: A significant interaction for age X cerebellar layer for phagocytic cups was also found (p < 0.000)l. Post hoc pairwise comparison revealed a higher density of phagocytic cups in the ML than the GL at younger ages (P12, p = 0.002; P14, p = 0.037). However, this pattern reversed at slightly older ages with the GL exhibiting more phagocytic cups than the ML at P17 (p < 0.000) and P21 (p = 0.046) (Fig. 5A).

Bottom Line: We found that microglial morphology changed from amoeboid to ramified during the first 3 postnatal weeks in a region specific manner.At P17 males showed an approximately twofold increase in microglia with thin processes compared with females.Our findings indicate a continuous process of microglial maturation and a nonuniform distribution of microglia in the cerebellar cortex that implicates microglia as an important cellular component of the developing cerebellum.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pharmacology, University of Maryland School of Medicine , Baltimore, Maryland 21201.

ABSTRACT
Microglia are being increasingly recognized as playing important roles in neurodevelopment. The cerebellum matures postnatally, undergoing major growth, but the role of microglia in the developing cerebellum is not well understood. Using the laboratory rat we quantified and morphologically categorized microglia throughout the vermis and across development using a design-based unbiased stereology method. We found that microglial morphology changed from amoeboid to ramified during the first 3 postnatal weeks in a region specific manner. These morphological changes were accompanied by the sudden appearance of phagocytic cups during the third postnatal week from P17 to P19, with an approximately fourfold increase compared with the first week, followed by a prompt decline at the end of the third week. The microglial phagocytic cups were significantly higher in the granular layer (∼69%) than in the molecular layer (ML; ∼31%) during a 3 d window, and present on ∼67% of microglia with thick processes and ∼33% of microglia with thin processes. Similar proportions of phagocytic cups associated to microglia with either thick or thin processes were found in the ML. We observed cell nuclei fragmentation and cleaved caspase-3 expression within some microglial phagocytic cups, presumably from dying granule neurons. At P17 males showed an approximately twofold increase in microglia with thin processes compared with females. Our findings indicate a continuous process of microglial maturation and a nonuniform distribution of microglia in the cerebellar cortex that implicates microglia as an important cellular component of the developing cerebellum.

No MeSH data available.


Related in: MedlinePlus