**3.6** *In vitro* **migration assay**

The intercellular communication can be executed through a direct cell–cell interaction or through paracrine signaling mediated by a combination of active molecules. The major signaling molecules include cytokines, growth factors, chemokines, which can be generated and expressed in a wide variety of cell types including tumor cells and MSCs in response to multiple signals such as inflammatory or tumor microenvironment. Circulating MSCs are driven by such signaling molecules to home and subsequently migrate into the sites of tissue injury or disease. It is critical for the ability of MSCs to migrate and identify the injury sites for tissue repair and regeneration. Clinical data are still lacking for MSCs' homing and distribution of transplanted MSCs in the body, albeit a large number of *in vivo* studies are conducted on homing and migration pathways of MSCs for targeted stem cell-based therapies.

*Isolation and Expansion of Mesenchymal Stem/Stromal Cells, Functional Assays and Long-Term… DOI: http://dx.doi.org/10.5772/intechopen.100286*

There are different approaches for improvement of MSC homing and migration. In this section, *in vitro* migration capacity of human BM-MSCs is evaluated by using an 8 μm-pore transwell chamber inserts (Corning).

