m8ta
you are not logged in, login. new entry
text: sort by
tags: modified
type: chronology
{1404}
hide / edit[1] / print
ref: -0 tags: tissue response indwelling implants dialysis kozai date: 04-04-2018 00:28 gmt revision:1 [0] [head]

PMID-25546652 Brain Tissue Responses to Neural Implants Impact Signal Sensitivity and Intervention Strategies

  • (Interesting): eight identical electrode arrays implanted into the same region of different animals have shown that half the arrays continue to record neural signals for >14 weeks while in the other half of the arrays, single-unit yield rapidly degraded and ultimately failed over the same timescale.
  • In another study, aimed at uncovering the time course of insertion-related bleeding and coagulation, electrodes were implanted into the cortex of rats at varying time intervals (−120, −90, −60, −30, −15, and 0 min) using a micromanipulator and linear motor with an insertion speed of 2 mm/s.40 The results showed dramatic variability in BBB leakage that washed out any trend (Figure 3), suggesting that a separate underlying cause was responsible for the large inter- and intra-animal variability.

{1372}
hide / edit[1] / print
ref: -0 tags: bone marrow transplant chimera immune response to indwelling electrode implant capadona inflammation date: 02-02-2017 23:24 gmt revision:1 [0] [head]

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