Characterization of mesenchymal stromal cells derived from full-term umbilical cord blood

Background Multipotent mesenchymal stromal cells (MSC) are of interest for their potential to repair bone and cartilage, and also their immunosuppressive properties. Umbilical cord blood (UCB) is reported to contain MSC, and therefore may be a useful source of these cells for clinical applications. Methods We evaluated protocols for isolating MSC from UCB and characterized the surface phenotype, differentiation potential and immunoregulatory properties of the cells obtained. Results Ten of 25 UCB units processed yielded MSC-like colonies, with depletion of lineage+ cells providing a higher efficiency. Only two of the cultures could be expanded satisfactorily; the remainder failed to proliferate. One culture generated transformed lines that were grossly aneuploid, had up-regulated TERT transcripts and had lost CD90 expression and the capacity to differentiate. The two propagated UCB-MSC lines were similar to those from bone marrow but were not identical to each other, with differences seen in expression of surface markers and cytoskeletal proteins. Both underwent osteogenesis, but at different rates and to different degrees, while neither generated adipocytes. When added as a third party to a mixed lymphocyte culture, both suppressed proliferation. Discussion MSC-like cells can be isolated from UCB, but at low efficiencies, and they exhibit a variety of morphologies, growth rates and differentiation potentials and can transform in culture.