Properties of human astrocytes and NG2 glia

Abstract

Since animal models are inevitable for medical research, information on species differences in glial cell properties is critical for successful translational research. Here, we review current knowledge about morphological and functional properties of human astrocytes and NG2 glial cells and compare these data with those obtained for the comparable cells in rodents. Morphological analyses of astrocytes in the neocortex of rodents versus humans have demonstrated clear differences. In contrast, the functional properties of astrocytes or NG2 glial cells in these species are surprisingly similar. However, these findings should be interpreted with caution, as so far functional analyses of human cells are only available from neocortex and hippocampus, and it is known from rodent studies that the properties of astrocytes in different brain regions may vary considerably. Moreover, technical challenges render astrocyte electrophysiological measurements in situ unreliable, and human cell properties may be affected by medications. Nevertheless, based on the limited data currently available, there is substantial similarity between human and rodent astrocytes with regard to those functional properties studied to date. The unique morphological characteristics of astrocytes in human neocortex call for further physiological analysis. The basic properties for NG2 glia are even less completely evaluated with regard to the question of species differences but no glaring differences have been reported so far. In conclusion, it remains justifiable to employ mouse or rat models to investigate the etiology of human CNS diseases that might involve astrocytes or NG2 glia.

Acute brain injuries trigger microglia as an additional source of the proteoglycan NG2

“…On the other hand, previous immunohistochemical studies in human specimen suggested a similar NG2 expression pattern as in rodents. For example, NG2 could be detected in OPCs and pericytes in the healthy human CNS and was also found upregulated under pathological conditions [ 4 , 54 ]. Furthermore, NG2 was immuno-detectable in microglia/macrophages in samples from patients who encountered acute CNS injuries such as SCI or stroke, though the functions were not determined [ 7 , 52 ].…”

Metabolic compartmentalization between astroglia and neurons in physiological and pathophysiological conditions of the neurovascular unit

“…A major criticism is that rodent neurons and astroglia might not be an appropriate model for human brain cells. 165 In particular, the high glycolytic metabolic activity with lactate production might be a characteristic of rodent cell cultures only. Recent technology utilizing inducedpluripotent stem cells (iPSCs) has enabled us to evaluate human neurons and astroglia in vitro.…”

“…Of note, most available evidence is based on in vitro studies using rodent neural cell cultures. A major criticism is that rodent neurons and astroglia might not be an appropriate model for human brain cells . In particular, the high glycolytic metabolic activity with lactate production might be a characteristic of rodent cell cultures only.…”

Tuberous Sclerosis Complex as Disease Model for Investigating mTOR-Related Gliopathy During Epileptogenesis

“…Apart from astrocytes and oligodendrocytes, NG2 glial cells represent a third macroglial subtype in the CNS, which has received much attention in the past decade [for a detailed review, see ( 162 )]. In the literature, these cells are primarily referred to as OPCs, but also as complex cells, synantocytes, polydendrocytes, and GluR cells, as they depict glial and neuronal functions ( 163 , 164 ).…”