Application of human embryonic stem cells (hESCs) to stem-cell therapy is not feasible because of the risk of tumorigenicity and rejection. In contrast, human mesenchymal stem cells (hMSCs) are free from the risk of tumorigenicity and also have immune privilege. However, hMSCs obtained from adults have infinite variety in terms of the biological characteristics and functionality. We report here a new derivation method of hMSCs from hESCs. The derivation of hMSCs from three different hESC lines (SNUhES3, CHA3-hESC, and H9) was performed by embryoid bodies formation and subsequent culture with stage-different media without using inductive xenogenic feeder and mechanical selection procedure. The derived cells were morphologically similar to the unique fingerprint-like pattern of hMSCs and grew stably for at least 35 passages in vitro. These cells had hMSCs-like immunophenotypes: negative for CD34 and CD45; positive for CD29, CD44, CD73, CD90, and CD105. They could be differentiated into multiple lineages including osteocytes, chondrocytes, adipocytes, and myocytes. They maintained normal karyotype during the long-term cultivation and did not show tumorigenicity when transplanted into the immunodeficient mice. In conclusion, the new embryoid body-based derivation method of hMSCs from hESCs is simple, safe, and reproducible in three different hESC lines. We expect that this method will provide a more effective and powerful tool to derive hMSCs from various hESC lines.

The self-renewal of hESC is probably maintained by coordinated regulation of signalling-specific molecules and in a signalling-specific manner.

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Human embryonic stem (hES) cells are capable of differentiating into pluralistic cell types, however, spontaneous differentiation generally gives rise to a limited number of specific differentiated cell types and a large degree of cell heterogeneity. In an effort to increase the efficiency of specified hES cell differentiation, we performed a series of transient transfection of hES cells with EGFP expression vectors driven by different promoter systems, including human cellular polypeptide chain elongation factor 1 alpha (hEF1alpha), human cytomegalo-virus, and chicken beta-actin. All these promoters were found to lead reporter gene expression in undifferentiated hES cells, but very few drug-selectable transfectants were obtained and failed to maintain stable expression of the transgene with either chemical or electroporation methods. In an attempt to increase transfection efficiency and obtain stable transgene expression, differentiated hES cells expressing both mesodermal and ectodermal markers were derived using a defined medium. Differentiated hES cells were electroporated with a hEF1alpha promoter-driven EGFP or human noggin expression vector. Using RT-PCR, immunocytochemistry and fluorescence microscopy, the differentiated hES cells transfected with foreign genes were confirmed to retain stable gene and protein expression during prolonged culture. These results may provide a new tool for introducing exogenous genes readily into hES cells, thereby facilitating more directed differentiation into specific and homogenous cell populations.