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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

Morphological profile of microglia in the postnatal developing cerebellum. A, The frequency of round/amoeboid microglia significantly decreased after the first postnatal week (B), as well as stout microglia. C, Conversely, the density of microglia with thick processes increased only during the second postnatal week followed by a decrease in the third postnatal week. D, The density of microglia with thin processes gradually increased after the first postnatal week doubling their density by the third postnatal week. E, Sagittal views of the midvermis, labeled with Iba1, across the first 3 postnatal weeks. All data are expressed as mean ± SEM (n = 4, 2 males + 2 females for each group). Significant differences are detonated by *p < 0.05, **p < 0.01, and ***p < 0.000 compared with P5. Insets depict a higher magnification of selected microglia (red squares) in each panel. Scale bars: gray scale images, 100 µm; color images (inset), 25 µm; E, 500 µm (from P5 to P21). Images in A, B, C, and D depict the morphology of microglia at two different postnatal ages: P7 (A, B) and P12 (C, D).
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Figure 2: Morphological profile of microglia in the postnatal developing cerebellum. A, The frequency of round/amoeboid microglia significantly decreased after the first postnatal week (B), as well as stout microglia. C, Conversely, the density of microglia with thick processes increased only during the second postnatal week followed by a decrease in the third postnatal week. D, The density of microglia with thin processes gradually increased after the first postnatal week doubling their density by the third postnatal week. E, Sagittal views of the midvermis, labeled with Iba1, across the first 3 postnatal weeks. All data are expressed as mean ± SEM (n = 4, 2 males + 2 females for each group). Significant differences are detonated by *p < 0.05, **p < 0.01, and ***p < 0.000 compared with P5. Insets depict a higher magnification of selected microglia (red squares) in each panel. Scale bars: gray scale images, 100 µm; color images (inset), 25 µm; E, 500 µm (from P5 to P21). Images in A, B, C, and D depict the morphology of microglia at two different postnatal ages: P7 (A, B) and P12 (C, D).

Mentions: We categorized and counted microglia based on their morphological features across the vermis at different time points during postnatal development. The density of amoeboid microglia were the least common and they significantly decreased after the first postnatal week (p < 0.000)b. Compared with P5, there were significantly fewer amoeboid microglia at later ages from P10 to P21 (P10, p = 0.04; P12, p = 0.009; P14, p = 0.007; P17, p = 0.007; P21, p = 0.007; except at P7, p = 0.232; Fig. 2A). Likewise, the density of stout microglia decreased after the first postnatal week (p < 0.000)c from P12 to P21 compared with P5 (P12, p = 0.001; P14, p < 0.000; P17, p < 0.000; P21, p < 0.000; but not at P7, p = 0.706 or P10, p = 0.108; Fig. 2B). In contrast, the density of microglia with thick processes significantly increased after the first week (p < 0.000)d with there being more on P7 (p = 0.038), P10 (p < 0.000), P12 (p < 0.000), and P14 (p = 0.002) compared with P5. However, by the third postnatal week (*P17 and ^P21) the density of thick processed microglia dropped back down to immature levels (*p = 0.102 and ^p = 0.167, respectively; Fig. 2C). By contrast, the density of microglia with thin processes steadily increased as the cerebellum developed (p < 0.000)e with a significant difference from P10 until P21 (P10, p = 0.002; P12, p = 0.015; P14, p = 0.003; P17, p < 0.000; P21, p < 0.000 compared with P5; Fig. 2D).


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

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

Morphological profile of microglia in the postnatal developing cerebellum. A, The frequency of round/amoeboid microglia significantly decreased after the first postnatal week (B), as well as stout microglia. C, Conversely, the density of microglia with thick processes increased only during the second postnatal week followed by a decrease in the third postnatal week. D, The density of microglia with thin processes gradually increased after the first postnatal week doubling their density by the third postnatal week. E, Sagittal views of the midvermis, labeled with Iba1, across the first 3 postnatal weeks. All data are expressed as mean ± SEM (n = 4, 2 males + 2 females for each group). Significant differences are detonated by *p < 0.05, **p < 0.01, and ***p < 0.000 compared with P5. Insets depict a higher magnification of selected microglia (red squares) in each panel. Scale bars: gray scale images, 100 µm; color images (inset), 25 µm; E, 500 µm (from P5 to P21). Images in A, B, C, and D depict the morphology of microglia at two different postnatal ages: P7 (A, B) and P12 (C, D).
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Figure 2: Morphological profile of microglia in the postnatal developing cerebellum. A, The frequency of round/amoeboid microglia significantly decreased after the first postnatal week (B), as well as stout microglia. C, Conversely, the density of microglia with thick processes increased only during the second postnatal week followed by a decrease in the third postnatal week. D, The density of microglia with thin processes gradually increased after the first postnatal week doubling their density by the third postnatal week. E, Sagittal views of the midvermis, labeled with Iba1, across the first 3 postnatal weeks. All data are expressed as mean ± SEM (n = 4, 2 males + 2 females for each group). Significant differences are detonated by *p < 0.05, **p < 0.01, and ***p < 0.000 compared with P5. Insets depict a higher magnification of selected microglia (red squares) in each panel. Scale bars: gray scale images, 100 µm; color images (inset), 25 µm; E, 500 µm (from P5 to P21). Images in A, B, C, and D depict the morphology of microglia at two different postnatal ages: P7 (A, B) and P12 (C, D).
Mentions: We categorized and counted microglia based on their morphological features across the vermis at different time points during postnatal development. The density of amoeboid microglia were the least common and they significantly decreased after the first postnatal week (p < 0.000)b. Compared with P5, there were significantly fewer amoeboid microglia at later ages from P10 to P21 (P10, p = 0.04; P12, p = 0.009; P14, p = 0.007; P17, p = 0.007; P21, p = 0.007; except at P7, p = 0.232; Fig. 2A). Likewise, the density of stout microglia decreased after the first postnatal week (p < 0.000)c from P12 to P21 compared with P5 (P12, p = 0.001; P14, p < 0.000; P17, p < 0.000; P21, p < 0.000; but not at P7, p = 0.706 or P10, p = 0.108; Fig. 2B). In contrast, the density of microglia with thick processes significantly increased after the first week (p < 0.000)d with there being more on P7 (p = 0.038), P10 (p < 0.000), P12 (p < 0.000), and P14 (p = 0.002) compared with P5. However, by the third postnatal week (*P17 and ^P21) the density of thick processed microglia dropped back down to immature levels (*p = 0.102 and ^p = 0.167, respectively; Fig. 2C). By contrast, the density of microglia with thin processes steadily increased as the cerebellum developed (p < 0.000)e with a significant difference from P10 until P21 (P10, p = 0.002; P12, p = 0.015; P14, p = 0.003; P17, p < 0.000; P21, p < 0.000 compared with P5; Fig. 2D).

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