Mesenchymal stem cells (MSCs) represent a promising tool for new clinical concepts in supporting cellular therapy. Bone marrow (BM) was the first source reported to contain MSCs. However, for clinical use, BM may be detrimental due to the highly invasive donation procedure and the decline in MSC number and differentiation potential with increasing age. More recently, umbilical cord blood (UCB), attainable by a less invasive method, was introduced as an alternative source for MSCs. Another promising source is adipose tissue (AT). We compared MSCs derived from these sources regarding morphology, the success rate of isolating MSCs, colony frequency, expansion potential, multiple differentiation capacity, and immune phenotype. No significant differences concerning the morphology and immune phenotype of the MSCs derived from these sources were obvious. Differences could be observed concerning the success rate of isolating MSCs, which was 100% for BM and AT, but only 63% for UCB. The colony frequency was lowest in UCB, whereas it was highest in AT. However, UCB-MSCs could be cultured longest and showed the highest proliferation capacity, whereas BM-MSCs possessed the shortest culture period and the lowest proliferation capacity. Most strikingly, UCB-MSCs showed no adipogenic differentiation capacity, in contrast to BM-and AT-MSCs. Both UCB and AT are attractive alternatives to BM in isolating MSC: AT as it contains MSCs at the highest frequency and UCB as it seems to be expandable to higher numbers. STEM CELLS 2006;24: 1294 -1301

Evidence has emerged that mesenchymal stem cells (MSCs) represent a promising population for supporting new clinical concepts in cellular therapy. However, attempts to isolate MSCs from umbilical cord blood (UCB) of full-term deliveries have previously either failed or been characterized by a low yield. We investigated whether cells with MSC characteristics and multilineage differentiation potential can be cultivated from UCB of healthy newborns and whether yields might be maximized by optimal culture conditions or by defining UCB quality criteria.Using optimized isolation and culture conditions, in up to 63% of 59 low-volume UCB units, cells showing a characteristic mesenchymal morphology and immune phenotype (MSC-like cells) were isolated. These were similar to control MSCs from adult bone marrow (BM). Crucial points to isolate MSC-like cells from UCB were a time from collection to isolation of less than 15 hours, a net volume of more than 33 ml, and an MNC count of more than 1 ✕ 10 8 MNCs. Because MSC-like cells can be isolated at high efficacy from full-term UCB donations, we regard UCB as an additional stem cell source for experimental and potentially clinical purposes. The frequency of MSC-like cells ranged from

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