Differentiation and characterization of human MSCs.

One of the hallmark characteristics of human MSCs (hMSCs) is their ability to differentiate into adipocytes, chondrocytes and osteocytes in culture. The default fate for hMSCs appears to be bone: if late-passage cultures are left in basic culture medium, the hMSCs will become confluent and produce mineral, an indication of bone formation. However, when grown under certain culture conditions or in media containing specific components, the cells can be driven to become a number of other specific cell types including neural cells, myocytes, and cardiomyocytes. The protocols given here are the basic differentiation procedures for inducing osteogenesis, adipogenesis, and chondrogenesis in cultures of hMSCs. Although there is still no clear consensus on the antigen expression pattern that will define hMSCs, a protocol is also presented for the flow cytometric analysis using a series of antibody panels. The analysis of these surface epitope patterns can aide in the isolation and characterization of hMSCs.

Freezing harvested hMSCs and recovery of hMSCs from frozen vials for subsequent expansion, analysis, and experimentation.

Human multipotential stromal cells (hMSCs) are easily isolated from bone marrow and can be expanded by up to 200-fold in culture. Cultures of hMSCs are heterogeneous mixtures of stem/progenitor cells and more mature cell types. The proportion of each cell type in a given culture depends on how the cells are maintained. To maintain their stem cell-like qualities, hMSCs should be plated at low seeding densities (60-150 cells/cm2), lifted when between 60% and 80% confluent and should not be expanded beyond 4-5 passages. Thus, it is useful to establish a frozen bank of early passage cells. hMSCs store well in vapor phase liquid nitrogen (LN2) and are easily recovered for further expansion. This chapter describes one method of establishing a bank of early passage hMSCs using a seed lot system and the subsequent recovery of hMSCs from frozen stocks. The recovered cells can then be harvested and used for analyses of identification, functionality, in vitro and/or in vivo experimentation, or further expanded.