Autologous bone marrow mononuclear cells therapy attenuates activated microglial/macrophage response and improves spatial learning after traumatic brain injury.

BACKGROUND: Autologous bone marrow-derived mononuclear cells (AMNCs) have shown therapeutic promise for central nervous system insults such as stroke and traumatic brain injury (TBI). We hypothesized that intravenous injection of AMNC provides neuroprotection, which leads to cognitive improvement after TBI. METHODS: A controlled cortical impact (CCI) rodent TBI model was used to examine blood-brain barrier (BBB) permeability, neuronal and glial apoptosis, as well as cognitive behavior. Two groups of rats underwent CCI with AMNC treatment (CCI-autologous) or without AMNC treatment (CCI-alone), consisting of 2 million AMNC per kilogram body weight harvested from the tibia and intravenously injected 72 hours after injury. CCI-alone animals underwent sham harvests and received vehicle injections. RESULTS: Ninety-six hours after injury, AMNC significantly reduced the BBB permeability in injured animals, and there was an increase in apoptosis of proinflammatory activated microglia in the ipsilateral hippocampus. At 4 weeks after injury, we observed significant improvement in probe testing of CCI-Autologous group in comparison to CCI-Alone in the Morris Water Maze paradigm. CONCLUSION: Our data demonstrate that the intravenous injection of AMNC after TBI leads to neuroprotection by preserving early BBB integrity, increasing activated microglial apoptosis and improving cognitive function.

Intravenous multipotent adult progenitor cell therapy after traumatic brain injury: modulation of the resident microglia population.

INTRODUCTION: We have demonstrated previously that the intravenous delivery of multipotent adult progenitor cells (MAPC) after traumatic brain injury affords neuroprotection via interaction with splenocytes, leading to an increase in systemic anti-inflammatory cytokines. We hypothesize that the observed modulation of the systemic inflammatory milieu is related to T regulatory cells and a subsequent increase in the locoregional neuroprotective M2 macrophage population. METHODS: C57B6 mice were injected with intravenous MAPC 2 and 24 hours after controlled cortical impact injury. Animals were euthanized 24, 48, 72, and 120 hours after injury. In vivo, the proportion of CD4(+)/CD25(+)/FOXP3(+) T-regulatory cells were measured in the splenocyte population and plasma. In addition, the brain CD86(+) M1 and CD206(+) M2 macrophage populations were quantified. A series of in vitro co-cultures were completed to investigate the need for direct MAPC:splenocyte contact as well as the effect of MAPC therapy on M1 and M2 macrophage subtype apoptosis and proliferation. RESULTS: Significant increases in the splenocyte and plasma T regulatory cell populations were observed with MAPC therapy at 24 and 48 hours, respectively. In addition, MAPC therapy was associated with an increase in the brain M2/M1 macrophage ratio at 24, 48 and 120 hours after cortical injury. In vitro cultures of activated microglia with supernatant derived from MAPC:splenocyte co-cultures also demonstrated an increase in the M2/M1 ratio. The observed changes were secondary to an increase in M1 macrophage apoptosis. CONCLUSIONS: The data show that the intravenous delivery of MAPC after cortical injury results in increases in T regulatory cells in splenocytes and plasma with a concordant increase in the locoregional M2/M1 macrophage ratio. Direct contact between the MAPC and splenocytes is required to modulate activated microglia, adding further evidence to the central role of the spleen in MAPC-mediated neuroprotection.