Assessment of umbilical cord tissue as a source of mesenchymal stem cell/endothelial cell mixtures for bone regeneration

Aim: To enumerate and characterize mesenchymal stem cells (MSCs) and endothelial cells (ECs) in umbilical cord (UC) tissue digests. Materials & methods: Cultured UC cells were characterized phenotypically, and functionally by using 48-gene arrays. Native MSCs and ECs were enumerated using flow cytometry. Results: Compared with bone marrow (BM) MSCs, UC MSCs displayed significantly lower (range 4-240-fold) basal levels of bone-related transcripts, but their phenotypes were similar (CD73(+), CD105(+), CD90(+), CD45(-) and CD31(-)). UC MSCs responded well to osteogenic induction, but day 21 postinduction levels remained below those achieved by BM MSCs. The total yield of native UC MSCs (CD90(+), CD45(-) and CD235(-)) and ECs (CD31(+), CD45(-) and CD235(-)) exceeded 150 and 15 million cells/donation, respectively. Both UC MSCs and ECs expressed CD146. Conclusion: While BM MSCs are more predisposed to osteogenesis, UC tissue harbors large numbers of MSCs and ECs; such minimally manipulated off-the-shelf' cellular mixtures can be used for regenerating bone in patients with compromised vascular supply.