Tissue injury may create a specific microenvironment for inducing the systemic participation of stromal-like cells in the repair process. Here we show that substance P is an injury-inducible factor that acts early in the wound healing process to induce CD29(+) stromal-like cell mobilization. Likewise, mobilization of such cells also occurs in uninjured mice, rats and rabbits if substance P is intravenously injected. Upon further characterization these substance P-mobilized CD29(+) cells were found to be similar to stromal cells from a number of connective tissues, including bone marrow (that is, bone marrow stromal cells, or BMSCs). Both substance P injection and transfusion of autologously derived substance P-mobilized CD29(+) cells from uninjured rabbits accelerated wound healing in an alkali burn model. Also, epithelial engraftment of the transfused cells into the injured tissue occurred during the wound healing. Finally, using human BMSCs as a test population, we show that substance P stimulates transmigration, cell proliferation, activation of the extracellular signal-related kinases (Erk) 1 and 2 and nuclear translocation of beta-catenin in vitro. This finding highlights a previously undescribed function of substance P as a systemically acting messenger of injury and a mobilizer of CD29(+) stromal-like cells to participate in wound healing.

The potential benefits or the tissue-damaging effects of inflammatory response after central nervous system injuries have long been disputed. Recent studies have noted that substance P (SP), a neuropeptide, plays an important role in the wound-healing process by recruiting bone marrow stem cells to the injured tissue. In this study, we examined whether SP can enhance recovery from spinal cord injury (SCI) in Sprague-Dawley rats through its known function of stem cell mobilization and/or through the modulation of inflammation. We examined proinflammatory and anti-inflammatory cytokines and markers for macrophage subtypes. SP treatment modulated the SCI microenvironment toward a more anti-inflammatory and reparative one by inducing interleukin-10 and M2 macrophages and suppressing inducible nitric oxide synthase and tumor necrosis factor-α. This modulation was achieved at 1 day much earlier than SP-stimulated bone marrow stem cells' mobilization. Early intervention of the devastating inflammatory response by SP treatment caused the lesion cavity to become filled with robust axonal outgrowth that overlaid the M2 macrophages at 2 weeks--all of which culminated in tissue sparing and improvement in functional recovery from the SCI. SP is therefore a potential anti-inflammatory modulator for the treatment of injury-induced inflammatory central nervous system disorders.

Macrophage polarization plays an important role in tissue damage and repair. In this study, we show that Substance-P (SP) can directly induce M2 polarization of inflammatory macrophages. SP induced the differentiation of GM-CSF-differentiated pro-inflammatory macrophages into alternatively activated phagocytic M2 like macrophages (M2SP) through direct activation of the PI3K/Akt/mTOR/S6kinase pathway and induction of Arginase-1, CD163, and CD206, all of which were nullified by pretreatment with the neurokinin-1 receptor (NK-1R) antagonist RP67580 and specific signaling pathway inhibitors. M2SP were distinct from IL-4/IL-13-induced M2a and IL-10-induced M2c subtypes; they did not show STAT activation and exhibited high phagocytic and endothelial adhesive activity. Furthermore, SP had a dominant effect on M2 polarization over Interferon gamma (IFNγ), a potent M1-skewing cytokine, and effectively induced the M2 phenotype in monocytes and the human THP-1 cell line. Finally, adoptively transferred M2SP migrated to a spinal cord injury (SCI) lesion site and improved functional recovery. Collectively, our findings show that SP, a neuropeptide, plays a role as a novel cytokine by inducing tissue-repairing M2SP macrophages and thus may be developed for pharmacological intervention in diseases involving chronic inflammation and acute injury.

Intravenous administration of mesenchymal stem cells (MSCs) has served as a clinical intervention for inflammatory diseases. Once entered to blood circulation, MSCs are exposed to a harsh environment which sharply decreases cell viability due to the fact that injected cells, being susceptible to shear stress, are subjected to the high velocities of the bloodstream and lack of proper mechanical support that keeping them in an attachment-deprived state. Here, we coated the nanofilm onto viable MSCs by depositing poly-l-lysine and hyaluronic acid molecules along with arginine-glycine-aspartic acid (RGD peptide) as building blocks to protect cells from shear stress and stabilize them in a single cell, suspension state. In this article, we found that nanofilm-coated cells showed significantly increased cell survival in vitro and in vivo, which was also supported by the activation of survival-related protein, Akt. The coated nanofilm did not interfere with the stemness of MSCs which was determined based on the colony forming unit-fibroblast (CFU-F) assay and in vitro differentiation potential. Because of the characteristics of films showing light molecular deposition density, flexibility, and looseness, application of nanofilms did not block cell migration. When the cells were administrated intravenously, the nanofilm coated MSCs not only prolonged blood circulation lifetime but also showed increased stem cell recruitment to injured tissues in the muscle injury in vivo model, due to prolonged survival. Surface modification of MSCs using nanofilms successfully modulated cell activity enabling them to survive the anoikis-inducing state, and this can provide a valuable tool to potentiate the efficacy of MSCs for in vivo cell therapy.

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