begun to utilize techniques to inject M2 cells directly or cause polarization indirectly. In spinal cord injury, the transplantation of mesenchymal stem cells has been shown to increase IL-4/13 and decrease TNFα levels [85]. These cytokine changes were associated with increased Arg1+ staining, consistent with an M2 response, and associated with downregulation of inflammation, locomotor recovery and reduced scar formation [85]. This has been shown in several other cases, where M2 cell induction appeared to alleviate spinal cord injury pathology [86-89]. This beneficial result is not limited to spinal cord injury. By targeting the PPARγ pathway with PPARγ agonists that potentially lead to induction of M2 microglia, several groups have shown efficacy in treating traumatic brain injury [71,72] and ischemia [90]. As summarized in Table 2, there are several other examples of investigators using various molecules that are now known to induce M2 polarization in order to treat CNS injuries.
