Mesenchymal Stem Cell Isolation and Expansion Methodology

Mesenchymal stem cells (MSCs) are adult non-hematopoietic stem cells originally isolated from bone marrow (BM) (Prockop, 1997), but they are virtually present and can be isolated from almost every tissue of the body (Da Silva et al., 2006), including peripheral blood (Roufosse et al., 2004). This evidence suggests that MSCs could be part of a mesenchymal-stromal cell system diffused throughout the body. The real in vivo counterpart of culture-expanded MSCs is still unknown; however, different Authors suggested that MSCs are a subgroup of vessel-lining pericytes that may contribute to vessel homeostasis by reacting to tissue damage with regenerative processes, locally modulating the inflammatory reaction, and entering systemic circulation to migrate according to cytokine gradients (Crisan et al., 2008). The International Society of Cellular Therapy (ISCT) stated the following three criteria for the definition of MSCs after in vitro expansion (Dominici et al., 2006): (1) the adherence to plastic under standard tissue culture conditions; (2) the expression of a specific combination of cell surface markers; (3) the capability of multilineage differentiation under appropriate in vitro conditions. These criteria are necessary to overcome the problems due to the absence of MSC-specific cell surface markers, the high heterogeneity in terms of differentiation potential, and the similarities to fibroblasts displayed by isolated and expanded MSCs. Consequently, ISTC suggested to define MSCs as “Multipotent Mesenchymal Stromal Cells” instead of “Mesenchymal Stem Cells”. In this Chapter, MSC isolation, expansion and functional characterization will be discussed in details.