Microglial Cell Density Research Articles

Quantitative neuropathological changes in presymptomatic Huntington's disease

Morphometric studies of the tail of the caudate nucleus, the site where the pathology is first seen, were performed on 16 brain specimens collected from individuals at risk for inheriting Huntington's disease (HD). Medical records and information obtained from immediate family members indicated that all had died without symptoms of HD. Six individuals had 37 or more CAG repeats and were designated HD gene carriers, whereas 10 were determined to be non-carriers. Cell counts of the tail of the caudate nucleus revealed an increased density of oligodendrocytes among the presymptomatic HD gene carriers (mean cells/field: carriers = 40.0, noncarrier = 21.3; age, sex, repeated measure adjusted F[126] = 11.7, p = 0.0008). No statistically significant differences were found between HD carriers and noncarriers in the density of neurons (carriers = 16.9, noncarriers = 15.5), astrocytes (carriers = 27.8, noncarriers = 21.3) or microglial cells (carriers = 7.9, noncarriers = 5.6). Ubiquitin immunostaining performed in 3 gene carriers revealed intranuclear inclusions in all 3 cases, including 1, with 37 repeats, who died 3 decades before the expected age for onset of the clinical syndrome. Normal densities of other cell types and careful macroscopic examination suggest that the increase in oligodendroglial density is not a consequence of atrophy and may instead reflect a developmental effect of the HD gene. Ann Neurol 2001;49:29–34

Quantitative neuropathological changes in presymptomatic Huntington's disease

Morphometric studies of the tail of the caudate nucleus, the site where the pathology is first seen, were performed on 16 brain specimens collected from individuals at risk for inheriting Huntington's disease (HD). Medical records and information obtained from immediate family members indicated that all had died without symptoms of HD. Six individuals had 37 or more CAG repeats and were designated HD gene carriers, whereas 10 were determined to be non-carriers. Cell counts of the tail of the caudate nucleus revealed an increased density of oligodendrocytes among the presymptomatic HD gene carriers (mean cells/field: carriers = 40.0, noncarrier = 21.3; age, sex, repeated measure adjusted F[126] = 11.7, p = 0.0008). No statistically significant differences were found between HD carriers and noncarriers in the density of neurons (carriers = 16.9, noncarriers = 15.5), astrocytes (carriers = 27.8, noncarriers = 21.3) or microglial cells (carriers = 7.9, noncarriers = 5.6). Ubiquitin immunostaining performed in 3 gene carriers revealed intranuclear inclusions in all 3 cases, including 1, with 37 repeats, who died 3 decades before the expected age for onset of the clinical syndrome. Normal densities of other cell types and careful macroscopic examination suggest that the increase in oligodendroglial density is not a consequence of atrophy and may instead reflect a developmental effect of the HD gene.

Peripheral administration of novel anti-inflammatories can attenuate the effects of chronic inflammation within the CNS

In the present study we investigated whether nitroflurbiprofen (NFP) or nitro-aspirin can reduce the inflammatory response induced by continuous infusion of lipopolysaccharide (LPS) into the fourth ventricular space of the rat's brain for 30 days. The chronic LPS infusion produced an extensive inflammation that was particularly evident in the hippocampus, subiculum and entorhinal and piriform cortices. Daily peripheral administration of NFP dose-dependently, and significantly, attenuated the brain inflammation as indicated by the decreased density and reactive state of microglial cells. Daily peripheral administration of nitro-aspirin also attenuated the brain inflammation, but to a much lesser degree than NFP. The results demonstrated that nonsteroidal anti-inflammatory drugs (NSAIDs) could reduce brain inflammation and that NFP is an effective anti-inflammatory agent.

Reduced number and altered morphology of microglial cells in colony stimulating factor-1-deficient osteopetrotic op/op mice

The numerical density of microglial cells is reduced by 47% in the corpus callosum, by 37% in the parietal cortex and by 34% in the frontal cortex of mice mutant at the op locus which are totally devoid of colony stimulating factor-1 (CSF-1), the major growth factor for macrophages. Moreover, microglia in the frontal cortex of the op/op mice are smaller and have shorter cytoplasmic processes compared to control mice. Study suggests that CSF-1 plays a role in vivo in the formation and maturation of microglia and has little or no effect on perivascular cells.

Microglia development in the quail cerebellum

We used the QH1 antibody to study changes in the morphological features and distribution of microglial cells throughout development in the quail cerebellum. Few microglial precursors were present in the cerebellar anlage before the ninth incubation day (E9), whereas many precursors apparently entered the cerebellum from the meninges in the basal region of the cerebellar peduncles between E9 and E16. From this point of entry into the nervous parenchyma, they spread through the cerebellar white matter, forming a ‘stream’ of labeled cells that could be seen until hatching (E16). The number of microglial cells in the cerebellar cortex increased during the last days of embryonic life and first posthatching week, whereas microglial density within the white matter decreased after hatching. As a consequence, the differences in microglial cell density observed in the cerebellar cortex and the white matter during embryonic life diminished after hatching, and microglia showed a nearly homogeneous pattern of distribution in adult cerebella. Ameboid and poorly ramified microglial cells were found in developing stages, whereas only mature microglia appeared in adult cerebella. Our observations suggest that microglial precursors enter the cerebellar anlage mainly by traversing the pial surface at the basal region of the peduncles, then migrate along the white matter, and finally move radially to the different cortical layers. Differentiation occurs after the microglial cells have reached their final position. In other brain regions the development of microglia follows similar stages, suggesting that these steps are general rules of microglial development in the central nervous system. J. Comp. Neurol. 389:390–401, 1997. © 1997 Wiley-Liss, Inc.

Microglia development in the quail cerebellum

We used the QH1 antibody to study changes in the morphological features and distribution of microglial cells throughout development in the quail cerebellum. Few microglial precursors were present in the cerebellar anlage before the ninth incubation day (E9), whereas many precursors apparently entered the cerebellum from the meninges in the basal region of the cerebellar peduncles between E9 and E16. From this point of entry into the nervous parenchyma, they spread through the cerebellar white matter, forming a 'stream' of labeled cells that could be seen until hatching (E16). The number of microglial cells in the cerebellar cortex increased during the last days of embryonic life and first posthatching week, whereas microglial density within the white matter decreased after hatching. As a consequence, the differences in microglial cell density observed in the cerebellar cortex and the white matter during embryonic life diminished after hatching, and microglia showed a nearly homogeneous pattern of distribution in adult cerebella. Ameboid and poorly ramified microglial cells were found in developing stages, whereas only mature microglia appeared in adult cerebella. Our observations suggest that microglial precursors enter the cerebellar anlage mainly by traversing the pial surface at the basal region of the peduncles, then migrate along the white matter, and finally move radially to the different cortical layers. Differentiation occurs after the microglial cells have reached their final position. In other brain regions the development of microglia follows similar stages, suggesting that these steps are general rules of microglial development in the central nervous system.

Distribution of microglia and astrocytes in different regions of the normal adult rat brain

The distribution of glial cells (microglia and astrocytes) in different regions of normal adult rat brain was studied using immunohistochemical techniques and computer analysis. Antibodies against lipocortin 1 (LC1) and phosphotyrosine (PT), as well as an isolectin, GSA B4 (GSA), were used for identification of microglial units, while antibodies against protein S100β allowed us to identify astrocytes. If LC1 was used as a marker, more microglial cells were detected than with the use of PT or GSA. The highest density of LC1-positive microglial cells (on average, 130±5 cells/mm2 of the brain section area) was found in the neostriatum, while the lowest density (51±4 cells/mm2) was observed in the medulla oblongata. In general, the density of an LC1-positive microglial population was higher in the forebrain and lower in the midbrain, and the smallest number of these cells was detected in the brainstem and cerebellum. The number of astrocytes was, on average, 2–3 times as large as the number of microglial cells. High density of astrocytes, was found in the hypothalamus and hippocampus (more than 260 cells/mm2); they were more, numerous in the white matter than in the gray matter. Lower densities of this type cells were observed in the cerebral cortex, neostriatum, midbrain, medulla oblongata, and cerebellum (less than 200 cells/mm2).

Microglial cells of the rat brain in postnatal period (comparative immunocytochemical analysis)

In the course of the brain’s development, distribution of microglial cells was studied in rats using immunocytochemical detection. To identify the microglial cells, antibodies to lipocortin 1 (LC1) and phosphotyrosine (PT) were used. On postnatal day 1, LC1-positive microglial cells of an ameboid shape were distributed mainly in the subventricular zone; their mean density was 31±8 cells/mm2 (counted across the total area of frontal sections). On postnatal day 7, microglial cells of an intermediate type were located throughout the whole brain; their density was 54±15 cells/mm2. On the 15th day, LC1-positive cells were of a ramified shape, and their density reached 104±20 cells/mm2 (the microglial cell density in the mature normal brain was 103±3 cells/mm2). On postnatal day 7, PT-positive cells were similar in their morphology to LC1-positive cells of an intermediate type, while their mean density was 32 cells/mm2. In the mature brain, the density of PT-positive microglia was 53±5 cells/mm2; the shape of the cells in the white and gray matter of the brain was, on the whole, similar to that of LC1-positive microglia. Therefore, LC1 is a specific marker for different types of microglial cells in the developing brain. Our data about 3D distribution and morphological peculiarities of microglial cells at different stages of postnatal development are consistent with the hypothesis on the neuroectodermal origin of microglia.

Microglial reaction in Pick's disease

Number and morphology of microglial cells (MC) were compared in 6 cases each of Pick's disease (PD), Alzheimer's disease (AD) and controls using immunohistochemistry with the monoclonal antibody Ki-M1P. The severely involved neocortex of both PD and AD, and in particular the white matter subjacent to spongy PD lesions showed a marked increased of MC density, whereas non-affected PD areas and AD white matter showed no MC changes. The PD hippocampus, particularly the dentate gyrus, showed reduction of MC density and processes. We conclude that (1) MC reaction represents a major element of PD histopathology, and (2) density, morphology and distribution of MC are different in AD and PD.

Diffuse microgliosis associated with cerebral atrophy in the acquired immunodeficiency syndrome.

The cause of cerebral atrophy in patients with acquired immunodeficiency syndrome (AIDS) is obscure because human immunodeficiency virus type 1 (HIV-1)-related histopathological changes hardly correlate with cerebral atrophy. In this study, brain ventricular expansion was compared to the frontal lobe density of mononuclear and astroglial cells at autopsy. Twenty-eight male patients with AIDS displaying varying degrees of atrophy were compared to 17 age-matched male control subjects without AIDS or atrophy. An index of ventricular expansion was measured in uniformly sliced, formalin-fixed brain specimens, and immunochemically marked cells in coronal sections of the left superior frontal gyrus (Brodmann area 8) were quantified by field counting and planimetry. In the cortex, diffuse ferritin-stained microglia and glial fibrillary acidic protein-positive astrocytes were about twice as numerous in the patients with AIDS. Sixty-five percent (18/28) of the patients with AIDS had a microglial cell density greater than 2 standard deviations above the control mean. Microglial cell density was correlated positively with the severity of ventricular expansion (r = 0.71, p < 0.0001), while hypertrophied astroglial cells were very weakly related. In white matter, Ham-56-positive macrophages and glial fibrillary acidic protein-positive astrocytes were not meaningfully correlated with the index of ventricular expansion. Brain ventricular expansion and diffuse cortical microgliosis are highly prevalent anomalies in patients with AIDS, and their interrelationship may be more important than previously recognized.

Effect of axotomy on perineuronal glial cells in the hypoglossal and dorsal motor vagal nuclei of the cat

An approximate twofold increase in microglial cell densities occurred in the hypoglossal and dorsal motor vagal nuclei of the cat after transection of their respective nerves. The densities of astrocytes and oligodendrocytes were unaffected. A significant loss of neurons was demonstrated in both nuclei. These findings indicate that a perineuronal microglial cell reaction occurs in craniomotor nuclei of the cat following nerve transection, but to a considerably lesser extent than in rats and rabbits. We suggest that the different glial response after nerve transection compared with nerve crush in the cat may be related to differences in the degree of axotomy-induced neuronal degeneration.

Lumbar cord neurons at the origin of the spinothalamic tract in the rat

Neuroinflammation is known to play a key role in the prognosis of functional recovery after spinal cord injury (SCI). The involvement of microglial and mast cells in early and late stages of inflammation has been receiving increasing attention. This study was aimed at determining the influence of a pro-inflammatory cytokine, the granulocyte macrophage-colony stimulating factor (GM-CSF), on microglia and mast cell activation, glial scar formation and functional recovery following SCI. Rats were randomly injected with saline or GM-CSF one hour after a C4–C5 medio-lateral hemisection. To assess functional impairment and recovery, the rats were subjected to sensorimotor tasks for one month. Then, responses evoked by forepaw stimulation in the primary somatosensory cortex were recorded. We also quantified the changes in GM-CSF, IL-1β, IL-6 and BDNF levels, the gliosis and lesion volume as well as microglial and mast cell density, and mast cell surface. Our findings show that GM-CSF promotes cortical reactivation and recovery of tactile abilities, whereas it does not influence motor performances. A transient decrease in pro-inflammatory cytokines after GM-CSF treatment was also observed, whereas the endogenous GM-CSF level was unchanged. While the beneficial role of GM-CSF in reducing glial scar is confirmed, our findings reveal that neuroinflammatory events mediated by microglial and mast cells as well as the alteration of IL-1β and IL-6 levels are paralleled with an improvement in tactile recovery. These mechanisms could limit the duration and intensity of homeostatic imbalance and promote the plasticity of spared tissues.