Here, we compared the transcriptome profile of hAMCS and hBMSCs during directed differentiation into bone, cartilage, and fat. Our data revealed considerable similarities between bone marrow-derived MSCs (BMSCs) and adipose tissue-derived MSCs (AMSCs). We uncovered an interesting bifurcation of pathways in both BMSCs and AMSCs, in which osteogenesis and adipogenesis appear to be linked in a differentiation branch separate from chondrogenesis. Our data suggest that although a set of common genes may be needed for early differentiation into all three lineages, a different set of signature genes is associated with maturation into fully differentiated cells. The recruitment of different late differentiation factors explains and supports our conclusion that BMSCs differentiate more efficiently into bone and cartilage, whereas AMSCs differentiate better into adipocytes. This study not only generated a rich database for continuing molecular characterization of various MSCs but also provided a rational basis for assessing qualities of MSCs from different sources for the purpose of cell-based therapy and tissue engineering. STEM CELLS 2007;25:750 -760

Adult tissue-derived mesenchymal stem cells (MSCs) have demonstrated therapeutic efficacy in treating diseases or repairing damaged tissues through mechanisms thought to be mediated by either cell replacement or secretion of paracrine factors. Characterized, self-renewing human ESCs could potentially be an invariable source of consistently uniform MSCs for therapeutic applications. Here we describe a clinically relevant and reproducible manner of generating identical batches of hESC-derived MSC (hESC-MSC) cultures that circumvents exposure to virus, mouse cells, or serum. Trypsinization and propagation of HuES9 or H1 hESCs in feeder- and serum-free selection media generated three polyclonal, karyotypically stable, and phenotypically MSC-like cultures that do not express pluripotency-associated markers but displayed MSC-like surface antigens and gene expression profile. They differentiate into adipocytes, osteocytes, and chondrocytes in vitro. Gene expression and fluorescence-activated cell sorter analysis identified CD105 and CD24 as highly expressed antigens on hESC-MSCs and hESCs, respectively. CD105+, CD24- monoclonal isolates have a typical MSC gene expression profiles and were identical to each other with a highly correlated gene expression profile (r(2) > .90). We have developed a protocol to reproducibly generate clinically compliant and identical hESC-MSC cultures.

Spermatogonia are the male germ stem cells that continuously produce sperm for the next generation. Spermatogenesis is a complicated process that proceeds through mitotic phase of stem cell renewal and differentiation, meiotic phase, and postmeiotic phase of spermiogenesis. Full recapitulation of spermatogenesis in vitro has been impossible, as generation of normal spermatogonial stem cell lines without immortalization and production of motile sperm from these cells after long-term culture have not been achieved. Here we report the derivation of a normal spermatogonial cell line from a mature medakafish testis without immortalization. After 140 passages during 2 years of culture, this cell line retains stable but growth factor-dependent proliferation, a diploid karyotype, and the phenotype and gene expression pattern of spermatogonial stem cells. Furthermore, we show that this cell line can undergo meiosis and spermiogenesis to generate motile sperm. Therefore, the ability of continuous proliferation and sperm production in culture is an intrinsic property of medaka spermatogonial stem cells, and immortalization apparently is not necessary to derive male germ cell cultures. Our findings and cell line will offer a unique opportunity to study and recapitulate spermatogenesis in vitro and to develop approaches for germ-line transmission.germ stem cells ͉ meiosis ͉ Oryzias latipes ͉ spermiogenesis ͉ testis