**4.1 Homing and chemotactic activity**

Several studies have shown that MSCs are capable of migrating selectively and exert homing capabilities to different organs [29, 30]. Even if they are transplanted by local or systemic pathways, MSCs are principally guided to damaged tissues by the coordinate expression of specific receptors and ligands that allow them to reach their desired target and effectuate different mechanisms [31]. Additionally, MSCs possess a high chemotactic activity that increases the recruitment of different cells. Indeed, fibroblasts accelerate migration, proliferation, and integrin expression in response to MSC secretome [32, 33]. Similarly, neutrophils increase migration rate and immunological response when they are stimulated with MSCs after microbial challenge in vitro [34, 35]. In murine SCI models, the MSC-grafted SC has proven to amplify granulocytes and antigen-presenting cell recruitment in early stages by a wide variety of cytokines and chemokines such as CXCL10, CXCL12, CXCL1, and CL5 to boost SC recovery [34, 36].
