Background: In a phase II randomized, placebo controlled trial, MultiStem, an adult stem cell, was administered IV within 24 to 48 hrs after stroke onset. Earlier administration of MultiStem (<36 hrs) may have provided a benefit. In preclinical studies, we explored immune targets during this time frame that may underlie potential treatment effects.
Methods: Rats underwent tandem CCA/MCA occlusion and then at 24 hrs were randomized to receive IV MultiStem or saline (N=3-6 per group). At 3 days after infusion, rats were sacrificed and RNA was isolated from the injured cortex and spleen. To assess differential expression, noninformative probes were removed with a variance cut-off and genes having p-value < 0.01 were retained for gene set enrichment analysis. Principal component analysis and hierarchical clustering were performed.
Results: Among 364 selected genes within the brain, the gene expression profile of MultiStem treated stroke animals aligned with sham animals while there was a clear divergent profile of expression in vehicle treated stroke rats (fig). At 28d, samples from MultiStem treated animals clustered even more closely with shams and remained distinct from vehicle treated animals. Highly enriched gene expression categories downregulated by MultiStem included leukocyte activation, antigen presentation, and immune effector processing. Gene expression profiles in spleens derived from MultiStem treated rats closely resembled shams at 3 and 28 days. Using Ingenuity Pathway Analysis, MultiStem was shown to suppress the activation of various inflammatory signaling pathways regulated by TNF-α, IL-1β, IL-6, and IFN-γ, within peri-infarct tissue at 3 days after infusion.
Conclusion: MultiStem restores expression of multiple genes and pathways involved in immune and inflammatory responses after stroke. Optimal therapeutic windows for acute stroke may depend upon targeting the activation of immune responses from peripheral tissues such as the spleen.