Regular Article
Motility and Ramification of Human Fetal Microglia in Culture: An Investigation Using Time-Lapse Video Microscopy and Image Analysis

https://doi.org/10.1006/excr.2001.5431Get rights and content

Abstract

Microglia are mononuclear phagocytes of the central nervous system and are considered to derive from circulating bone marrow progenitors that colonize the developing human nervous system in the second trimester. They first appear as ameboid forms and progressively differentiate to process-bearing “ramified” forms with maturation. Signals driving this transformation are known to be partly derived from astrocytes. In this investigation we have used cocultures of astrocytes and microglia to demonstrate the relationship between motility and morphology of microglia associated with signals derived from astrocytes. Analysis of progressive cultures using time-lapse video microscopy clearly demonstrates the dynamic nature of microglia. We observe that ameboid microglial cells progressively ramify when cocultured with astrocytes, mirroring the “differentiation” of microglia in situ during development. We further demonstrate that individual cells undergo morphological transformations from “ramified” to “bipolar” to “tripolar” and “ameboid” states in accordance with local environmental cues associated with astrocytes in subconfluent cultures. Remarkably, cells are still capable of migration at velocities of 20–35 μm/h in a fully ramified state overlying confluent astrocytes, as determined by image analysis of motility. This is in keeping with the capacity of microglia for a rapid response to inflammatory cues in the CNS. We also demonstrate selective expression of the chemokines MIP-1α and MCP-1 by confluent human fetal astrocytes in cocultures and propose a role for these chemotactic cytokines as regulators of microglial motility and differentiation. The interchangeable morphological continuum of microglia supports the view that these cells represent a single heterogeneous population of resident mononuclear phagocytes capable of marked plasticity.

References (72)

  • G.M. Lauro et al.

    Human microglial cultures: A powerful model to study their origin and immunoreactive capacity

    Int. J. Dev. Neurosci.

    (1995)
  • K. Ohno et al.

    Production of granulocyte/macrophage colony stimulating factor by cultured astrocytes

    Biochem. Biophys. Res. Commun.

    (1990)
  • R. Parnaik et al.

    Differences between the clearance of apoptotic cells by professional and non-professional phagocytes

    Curr. Biol.

    (2000)
  • M. Sawada et al.

    Activation and proliferation of the isolated microglia by colony stimulating factor-1 and possible involvement of protein kinase C

    Brain Res.

    (1990)
  • S. Sudo et al.

    Neurons induce the activation of microglial cells in vitro

    Exp. Neurol.

    (1998)
  • A. Suzumura et al.

    Morphological transformation of microglia in vitro

    Brain Res.

    (1991)
  • A. Suzumura et al.

    Effects of colony-stimulating factors on isolated microglia in vitro

    J. Neuroimmunol.

    (1990)
  • J. Tanaka et al.

    Microglial ramification requires nondiffusible factors derived from astrocytes

    Exp. Neurol.

    (1996)
  • J. Tanaka et al.

    Morphological differentiation of microglial cells in culture: Involvement of insoluble factors derived from astrocytes

    Neurosci. Res.

    (1999)
  • W.E. Thomas

    Characterisation of the dynamic nature of microglial cells

    Brain Res. Bull.

    (1990)
  • Y. Tomozawa et al.

    Apoptosis of cultured microglia by the deprivation of macrophage colony-stimulating factor

    Neurosci. Res.

    (1996)
  • T. Yamada et al.

    White matter microglia produce membrane-type matrix metalloproteases, an activator of gelatinase A, in human brain tissues

    Acta Neuropathol.

    (1995)
  • F. Alliot et al.

    Microglial progenitors with a high proliferative potential in the embryonic and adult mouse brain

    Proc. Natl. Acad. Sci. USA

    (1991)
  • G. Blevins et al.

    Microglia in colony-stimulating factor 1-deficient op/op mice

    J. Neurosci. Res.

    (1995)
  • J. Brockhaus et al.

    Membrane properties of ameboid microglial cells in the corpus callosum slice from early postnatal mice

    J. Neurosci.

    (1993)
  • J. Brockhaus et al.

    Phagocytosing ameboid microglial cells studied in a mouse corpus callosum slice preparation

    Glia

    (1996)
  • C.F. Calvo et al.

    Production of monocyte chemotactic protein-1 by rat brain macrophages

    Eur. J. Neurosci.

    (1996)
  • A.K. Cross et al.

    Chemokines induce migration and changes in actin polymerization in adult rat brain microglia and a human fetal microglial cell line in vitro

    J. Neurosci. Res.

    (1999)
  • M. Czapiga et al.

    Function of microglia in organotypic slice cultures

    J. Neurosci. Res.

    (1999)
  • H. Fujita et al.

    Effects of GM-CSF and ordinary supplements on the ramification of microglia in culture: A morphometrical study

    Glia

    (1996)
  • S. Ganter et al.

    Growth control of cultured microglia

    J. Neurosci. Res.

    (1992)
  • D. Giulian et al.

    Colony-stimulating factors as promoters of ameboid microglia

    J. Neurosci.

    (1988)
  • I.K. Grundt et al.

    Exposure of cultured microglial cells to interferon-gamma

    Altern. Lab. Anim.

    (1996)
  • N.P. Hailer et al.

    Fluorescent dye prelabelled microglial cells migrate into organotypic hippocampal slice cultures and ramify

    Eur. J. Neurosci.

    (1997)
  • C. Hao et al.

    Production of colony stimulating factor-1 (CSF-1) by mouse astroglia in vitro

    J. Neurosci. Res.

    (1990)
  • Cited by (59)

    • Microglia in CNS development: Shaping the brain for the future

      2017, Progress in Neurobiology
      Citation Excerpt :

      In particular, the expression of MMP-8 and −9 plays a key role in the spreading of microglia and MMP inhibition impairs microglia expansion (Kierdorf et al., 2013). Similarly to the migration of oligodendrocytic cells, the migration of the microglial cells could be guided by a gradient of guiding cues such as semaphorins and netrins (Spassky et al., 2002) but also by chemoattracting molecules such as MCP1, MIP-1alpha (Rezaie et al., 2002), CXCL12 (Arno et al., 2014) or ligands of CSF-1R and VGEFR1 (Lelli et al., 2013). In the postnatal CNS, other neuronal factors help microglial cells to reach their final destination in the CNS parenchyma.

    • Regulation of brain microglia by female gonadal steroids

      2015, Journal of Steroid Biochemistry and Molecular Biology
      Citation Excerpt :

      Microglial cells after having invaded the brain typically acquire a ramified morphology [42]. This ramification process which is often termed as developmental plasticity occurs simultaneously with the radial migration of microglia [43] and has been confirmed in vitro [44]. This branching habit containing a small soma and several thin and branched processes provides a large surface area and allows covering a broader area in the surrounding to sense and monitor changes in their local environment.

    • Understanding the behavioural phenotype of the precocial spiny mouse

      2014, Behavioural Brain Research
      Citation Excerpt :

      However, spiny mice appear to display inherently lower levels of anxiety and fear compared to conventional rodents, as our wild-type adult spiny mice demonstrate comparable patterns of open field, central zone activity as do adult rats selectively bred from a low-anxiety behaviour line [34]. Spiny mice also show greater activity in open (dangerous/fearful) arms of the EPM compared to adult mice [35]. The novel object recognition test involves making alterations to previously stored information, and is thus an assessment of memory and learning [13,14,36].

    View all citing articles on Scopus
    1

    To whom reprint requests should be addressed. Fax: +44-207-708-3895. E-mail: [email protected].

    View full text