Mesenchymal stem cells (MSCs) have been investigated as promising candidates for use in new cell-based therapeutic strategies such as mesenchyme-derived tissue repair. MSCs are easily isolated from adult tissues and are not ethically restricted. MSC-related literature, however, is conflicting in relation to MSC differentiation potential and molecular markers. Here we compared MSCs isolated from bone marrow (BM), umbilical cord blood (UCB), and adipose tissue (AT). The isolation efficiency for both BM and AT was 100%, but that from UCB was only 30%. MSCs from these tissues are morphologically and immunophenotypically similar although their differentiation diverges. Differentiation to osteoblasts and chondroblasts was similar among MSCs from all sources, as analyzed by cytochemistry. Adipogenic differentiation showed that UCB-derived MSCs produced few and small lipid vacuoles in contrast to those of BM-derived MSCs and AT-derived stem cells (ADSCs) (arbitrary differentiation values of 245.57 +/- 943 and 243.89 +/- 145.52 mum(2) per nucleus, respectively). The mean area occupied by individual lipid droplets was 7.37 mum(2) for BM-derived MSCs and 2.36 mum(2) for ADSCs, a finding indicating more mature adipocytes in BM-derived MSCs than in treated cultures of ADSCs. We analyzed FAPB4, ALP, and type II collagen gene expression by quantitative polymerase chain reaction to confirm adipogenic, osteogenic, and chondrogenic differentiation, respectively. Results showed that all three sources presented a similar capacity for chondrogenic and osteogenic differentiation and they differed in their adipogenic potential. Therefore, it may be crucial to predetermine the most appropriate MSC source for future clinical applications.

Endothelial progenitor cells (EPCs), which express the CD133 marker, can differentiate into mature endothelial cells (ECs) and create new blood vessels. Normal angiogenesis is unable to repair the injured tissues that result from myocardial infarction (MI). Patients who have high cardiovascular risks have fewer EPCs and their EPCs exhibit greater in vitro senescence. Human umbilical cord blood (HUCB)-derived EPCs could be an alternative to rescue impaired stem cell function in the sick and elderly. The aim of this study was to purify HUCB-derived CD133(+) cells, expand them in vitro and evaluate the efficacy of the purified and expanded cells in treating MI in rats. CD133(+) cells were selected for using CD133-coupled magnetic microbeads. Purified cells stained positive for EPC markers. The cells were expanded and differentiated in media supplemented with fetal calf serum and basic fibroblast growth factor, insulin-like growth factor-I and vascular endothelial growth factor (VEGF). Differentiation was confirmed by lack of staining for EPC markers. These expanded cells exhibited increased expression of mature EC markers and formed tubule-like structures in vitro. Only the expanded cells expressed VEGF mRNA. Cells were expanded up to 70-fold during 60 days of culture, and they retained their functional activity. Finally, we evaluated the therapeutic potential of purified and expanded CD133(+) cells in treating MI by intramyocardially injecting them into a rat model of MI. Rats were divided into three groups: A (purified CD133(+) cells-injected); B (expanded CD133(+) cells-injected) and C (saline buffer-injected). We observed a significant improvement in left ventricular ejection fraction for groups A and B. In summary, CD133(+) cells can be purified from HUCB, expanded in vitro without loosing their biological activity, and both purified and expanded cells show promising results for use in cellular cardiomyoplasty. However, further pre-clinical testing should be performed to determine whether expanded CD133(+) cells have any clinical advantages over purified CD133(+) cells.

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