Bone marrow and umbilical cord blood are reported to be the main sources of mesenchymal stem cells (MSCs), which have been proposed for many clinical applications. This study evaluated and quantitated the differentiation potential of bone marrow-derived MSCs (bmMSCs) and cord bloodderived MSCs (cbMSCs) by in vitro induction. Results indicated that cbMSCs had a significantly stronger osteogenic potential but lower capacity for adipogenic differentiation than bmMSCs. Leptin, an important regulator of mesenchymal differentiation, has a significantly stronger effect of promoting osteogenesis and inhibiting adipogenesis in bmMSCs than in cbMSCs. Moreover, Cbfa1 mRNA expression in bmMSCs and cbMSCs was affected to different degrees by leptin during osteogenesis. In contrast, leptin reduced PPAR␥2 mRNA expression to the same level during adipogenesis in both types of MSCs. These results demonstrate the disparate capacities of MSCs from bone marrow and cord blood and suggest that they be used differently in experimental and therapeutic studies. In addition, the disparate differentiation tendencies of MSCs from different sources should be considered in further applications. STEM CELLS 2006;24:679 -685

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POU5F1 is essential for maintaining pluripotency in embryonic stem cells (ESCs). It has been reported that the constitutive activation of POU5F1 is sustained by the core transcriptional regulatory circuitry in ESCs; however, the means by which POU5F1 is epigenetically regulated remains enigmatic. In this study a fluorescence-based reporter system was used to monitor the interplay of 5 reprogramming-associated TFs and 17 chromatin regulators in the transcription of POU5F1. We show the existence of a stoichiometric effect for SOX2, POU5F1, NANOG, MYC and KLF4, in regulating POU5F1 transcription. Chromatin regulators EP300, KDM5A, KDM6A and KDM6B cooperate with KLF4 in promoting the transcription of POU5F1. Moreover, inhibiting HDAC activities induced the expression of Pou5f1 in mouse neural stem cells (NSCs) in a spatial- and temporal- dependent manner. Quantitative chromatin immunoprecipitation-PCR (ChIP-qPCR) shows that treatment with valproic acid (VPA) increases the recruitment of Kdm5a and Kdm6a to proximal promoter (PP) and proximal enhancer (PE) of Pou5f1 whereas enrichment of Ep300 and Kdm6b was seen in PP but not PE of Pou5f1 promoter. These findings reveal the interplay between the chromatin regulators and histone modifications in the expression of POU5F1.