Jason Hamilton

Multipotent adult progenitor cells prevent macrophage-mediated axonal dieback and promote regrowth after spinal cord injury.

Macrophage-mediated axonal dieback presents an additional challenge to regenerating axons after spinal cord injury. Adult adherent stem cells are known to have immunomodulatory capabilities, but their potential to ameliorate this detrimental inflammation-related process has not been investigated. Using an in vitro model of axonal dieback as well as an adult rat dorsal column crush model of spinal cord injury, we found that multipotent adult progenitor cells (MAPCs) can affect both macrophages and dystrophic neurons simultaneously. MAPCs significantly decrease MMP-9 (matrix metalloproteinase-9) release from macrophages, effectively preventing induction of axonal dieback. MAPCs also induce a shift in macrophages from an M1, or “classically activated” proinflammatory state, to an M2, or “alternatively activated” antiinflammatory state. In addition to these effects on macrophages, MAPCs promote sensory neurite outgrowth, induce sprouting, and further enable axons to overcome the negative effects of macrophages as well as inhibitory proteoglycans in their environment by increasing their intrinsic growth capacity. Our results demonstrate that MAPCs have therapeutic benefits after spinal cord injury and provide specific evidence that adult stem cells exert positive immunomodulatory and neurotrophic influences.

Intravenous multipotent adult progenitor cell therapy for traumatic brain injury: preserving the blood brain barrier via an interaction with splenocytes.

Recent investigation has shown an interaction between transplanted progenitor cells and resident splenocytes leading to the modulation of the immunologic response in neurological injury. We hypothesize that the intravenous injection of multipotent adult progenitor cells (MAPC) confers neurovascular protection after traumatic brain injury through an interaction with resident splenocytes, subsequently leading to preservation of the blood brain barrier. Four groups of rats underwent controlled cortical impact injury (3 groups) or sham injury (1 group). MAPC were injected via the tail vein at two doses (2*10(6) MAPC/kg or 10*10(6) MAPC/kg) 2 and 24h after injury. Blood brain barrier permeability was assessed by measuring Evans blue dye extravasation (n=6/group). Additionally, splenic mass was measured (n=12/group) followed by splenocyte characterization (n=9/group) including: cell cycle analysis (n=6/group), apoptosis index (n=6/group), cell proliferation (n=6/group), and inflammatory cytokine measurements (n=6/group). Vascular architecture was determined by immunohistochemistry (n=3/group). Traumatic brain injury results in a decrease in splenic mass and increased blood brain barrier permeability. Intravenous infusion of MAPC preserved splenic mass and returned blood brain barrier permeability towards control sham injured levels. Splenocyte characterization indicated an increase in the number and proliferative rate of CD4+ T cells as well as an increase in IL-4 and IL-10 production in stimulated splenocytes isolated from the MAPC treatment groups. Immunohistochemistry demonstrated stabilization of the vascular architecture in the peri-lesion area. Traumatic brain injury causes a reduction in splenic mass that correlates with an increase in circulating immune cells leading to increased blood brain barrier permeability. The intravenous injection of MAPC preserves splenic mass and the integrity of the blood brain barrier. Furthermore, the co-localization of transplanted MAPC and resident CD4+ splenocytes is associated with a global increase in IL-4 and IL-10 production and stabilization of the cerebral microvasculature tight junction proteins.

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

IntroductionWe 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.MethodsC57B6 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.ResultsSignificant 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.ConclusionsThe 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.

Intravenous Multipotent Adult Progenitor Cell Therapy Attenuates Activated Microglial/Macrophage Response and Improves Spatial Learning After Traumatic Brain Injury

We previously demonstrated that the intravenous delivery of multipotent adult progenitor cells (MAPCs) after traumatic brain injury (TBI) in rodents provides neuroprotection by preserving the blood‐brain barrier and systemically attenuating inflammation in the acute time frame following cell treatment; however, the long‐term behavioral and anti‐inflammatory effects of MAPC administration after TBI have yet to be explored. We hypothesized that the intravenous injection of MAPCs after TBI attenuates the inflammatory response (as measured by microglial morphology) and improves performance at motor tasks and spatial learning (Morris water maze [MWM]). MAPCs were administered intravenously 2 and 24 hours after a cortical contusion injury (CCI). We tested four groups at 120 days after TBI: sham (uninjured), injured but not treated (CCI), and injured and treated with one of two concentrations of MAPCs, either 2 million cells per kilogram (CCI‐2) or 10 million cells per kilogram (CCI‐10). CCI‐10 rats showed significant improvement in left hind limb deficit on the balance beam. On the fifth day of MWM trials, CCI‐10 animals showed a significant decrease in both latency to platform and distance traveled compared with CCI. Probe trials revealed a significant decrease in proximity measure in CCI‐10 compared with CCI, suggesting improved memory retrieval. Neuroinflammation was quantified by enumerating activated microglia in the ipsilateral hippocampus. We observed a significant decrease in the number of activated microglia in the dentate gyrus in CCI‐10 compared with CCI. Our results demonstrate that intravenous MAPC treatment after TBI in a rodent model offers long‐term improvements in spatial learning as well as attenuation of neuroinflammation.

Intravenous multipotent adult progenitor cell treatment decreases inflammation leading to functional recovery following spinal cord injury.

Following spinal cord injury (SCI), immune-mediated secondary processes exacerbate the extent of permanent neurological deficits. We investigated the capacity of adult bone marrow-derived stem cells, which exhibit immunomodulatory properties, to alter inflammation and promote recovery following SCI. In vitro, we show that human multipotent adult progenitor cells (MAPCs) have the ability to modulate macrophage activation, and prior exposure to MAPC secreted factors can reduce macrophage-mediated axonal dieback of dystrophic axons. Using a contusion model of SCI, we found that intravenous delivery of MAPCs one day, but not immediately, after SCI significantly improves urinary and locomotor recovery, which was associated with marked spinal cord tissue sparing. Intravenous MAPCs altered the immune response in the spinal cord and periphery, however biodistribution studies revealed that no MAPCs were found in the cord and instead preferentially homed to the spleen. Our results demonstrate that MAPCs exert their primary effects in the periphery and provide strong support for the use of these cells in acute human contusive SCI.

Multipotent Adult Progenitor Cells Enhance Recovery After Stroke by Modulating the Immune Response from the Spleen

Stem cell therapy modulates not only the local microenvironment of the brain but also the systemic immune responses. We explored the impact of human multipotent adult progenitor cells (MAPC) modulating splenic activation and peripheral immune responses after ischemic stroke. Hundred twenty‐six Long‐Evans adult male rats underwent middle cerebral artery occlusion. Twenty‐four hours later, they received IV MAPC or saline treatment. At 3 days after infusion, RNA was isolated from the injured cortex and spleen for microarray analysis. Spleen mass, splenocyte phenotype, and releasing cytokines were measured. Serum cytokines, MAPC biodistribution, brain lesion sizes and neurofunctional deficits were compared in rats treated with MAPC or saline with and without spleens. Stroked animals treated with MAPC exhibited genes that more closely resembled animals with sham surgery. Gene categories downregulated by MAPC included leukocyte activation, antigen presentation, and immune effector processing, associated with the signaling pathways regulated by TNF‐α, IL‐1β, IL‐6, and IFN‐γ within the brain. MAPC treatment restored spleen mass reduction caused by stroke, elevated Treg cells within the spleen, increased IL‐10 and decreased IL‐1β released by splenocytes. MAPC reduced IL‐6 and IL‐1β and upregulated IL‐10 serum levels. Compared with saline, MAPC enhance stroke recovery in rats with intact spleens but had no effects in rats without spleens. MAPC restores expression of multiple genes and pathways involved in immune and inflammatory responses after stroke. Immunomodulation of the splenic response by the intravenous administration of MAPC may create a more favorable environment for brain repair after stroke. Stem Cells 2017;35:1290–1302