The Role of Mesenchymal Stem Cells in Angiogenesis

Mesenchymal stem cells (MSC) are a heterogeneous subset of stromal stem cells that can be isolated from many adult tissues. They can differentiate into cells of the mesodermal lineage, such as adipocytes, osteocytes and chondrocytes, providing a promising tool for tissue repair. MSC can interact with cells of both the innate and adaptive immune systems, leading to the modulation of several effector functions. The immunoregulatory functions of human MSC, coupled with their low immunogenicity, provide a rationale for the use of allogeneic MSC to treat severe graft-versus-host disease (GvHD) and, possibly, autoimmune disorders. In addition, MSC exhibit tropism for sites of tissue damage as well as for the tumor microenvironment, where they integrate into the tumor-associated stroma supporting cancer growth. However, studies investigating the in vivo and in vitro effects mediated by MSC on tumor growth provided conflicting results, depending on the experimental model tested. This chapter reviews the role of MSC in different angiogenic processes and underlying mechanisms. In particular, we discuss the involvement of MSC in angiogenesis in ischemic brain and heart after stroke, wound healing, tumor angiogenesis and maintenance of hematopoietic stem cell niche.