{1372} revision 1 modified: 02-02-2017 23:24 gmt

PMID-24973296 The roles of blood-derived macrophages and resident microglia in the neuroinflammatory response to implanted intracortical microelectrodes.

  • Quite good introductory review on current understanding of immune / inflammatory / BBB breakdown response to indwelling neural implants.
  • Used chimera mice with marrow from CFP mice transplanted into irradiated hosts, so myeloid cells were labeled (including macrophages and monocytes).
    • Details of this process are properly fascinating ... there are clever ways of isolating and selecting the right marrow cells.
  • Implanted with a dummy Michigan style probe, 2mm x 123 um x 15um.
  • Histological processes and cell sorting / labeling also highly detailed.
  • 60% of the infiltrating cells (CFP+) are macrophages.
    • Within the total IBA1+ population (macrophages + microglia), we saw that only 20% of the total IBA1+ population was comprised of microglia at two weeks post implantation (Fig. 9G).
    • Additionally, at chronic time points (four, eight and sixteen weeks), we observed that less than 40% of the total IBA1+ population was comprised of microglia (Fig. 9G).
    • On the other hand, no significant differences were observed in microglia populations over time (Fig. 9G, Table 4). Together, our results suggest a predominant role of infiltrating macrophages surrounding implanted microelectrodes over time.
  • IBA1 = marker for ionized calcium binding adapter molecule, to label the total population of microglia/ macrophages (both resting and activated)
  • CD68 = activated microglia / macrophage.
    • Hard to discriminate microglia and infiltrating macrophages.
  • Interestingly, fluctuations in GFAP+ immunoreactivity correlated well with neuronal density and CFP+ immunoreactivty, suggesting a possible role of astrocytes in facilitating trafficking of blood-derived cells.
  • Contrary to what has been suggested by many intracortical microelectrode studies, a consistent connection was not found between activated microglia/macrophages and neuron density in our chimera models