Microglia and Microglia-Like Cells: Similar but Different

Abstract

Microglia are the tissue-resident macrophages of the central nervous parenchyma. In mammals, microglia are thought to originate from yolk sac precursors and posteriorly maintained through the entire life of the organism. However, the contribution of microglial cells from other sources should also be considered. In addition to “true” or “bona-fide” microglia, which are of embryonic origin, the so-called “microglia-like cells” are hematopoietic cells of bone marrow origin that can engraft the mature brain mainly under pathological conditions. These cells implement great parts of the microglial immune phenotype, but they do not completely adopt the “true microglia” features. Because of their pronounced similarity, true microglia and microglia-like cells are usually considered together as one population. In this review, we discuss the origin and development of these two distinct cell types and their differences. We will also review the factors determining the appearance and presence of microglia-like cells, which can vary among species. This knowledge might contribute to the development of therapeutic strategies aiming at microglial cells for the treatment of diseases in which they are involved, for example neurodegenerative disorders like Alzheimer’s and Parkinson’s diseases.

Transcriptional and epigenetic regulation of microglia in maintenance of brain homeostasis and neurodegeneration

“…They interact with neurons via various signaling molecules including transforming growth factor-β (TGF-β), brain-derived neurotrophic factor (BDNF), and complement proteins including CR3 and C1q ( Cornell et al, 2022 ). Epigenome and genome-wide transcriptome studies have shown that microglia are different from other glial cells and tissue macrophages ( Cuadros et al, 2022 ). A number of microglia specific signature genes have been identified to be involved in diverse functions of microglia.…”

Study on Biomarkers Related to the Treatment of Post-Stroke Depression and Alternative Medical Treatment Methods

“… 23 At the same time, M2 microglia also release brain-derived neurotrophic factor (BDNF) to promote synapse formation. 23 Therefore, we hypothesized that acupuncture might ameliorate the PSD inflammatory environment, modulate the M1/M2 polarization direction of microglia, upregulate the NRBP1-CREB-BDNF pathway in microglia, and promote synaptic motility by producing more BDNF, thereby improving PSD symptoms, 24 which has also been verified experimentally and subsequently clinically. Combined with relevant literature, the polarization direction of microglia M1/M2 is closely related to the treatment of ischemic PSD, 22 , 25 Sirt1 can inhibit the expression of IL-1, IL-6, TNF-α pro-inflammatory factors, and Sirt1/NF- The κB pathway also plays an important role in regulating microglial M1/M2 polarization.…”

Density of TMEM119-positive microglial cells in postmortem cerebrospinal fluid as a surrogate marker for assessing complex neuropathological processes in the CNS

“…They supplement the growing concept of glymphatic pathways and warrant further studies to clarify diverging quantitative differences in cases with similar causes of death together with the reason of selective laminar vulnerability at the border of isocortical layers I/II and deep layers V/VI including U-fibers. Forensic autopsy tissue proved invaluable in addressing fundamental neurobiologic and pathologic questions and interpretation of results of animal studies [ 38 , 39 ].…”