Mesenchymal stem cells (MSC) that can differentiate to various connective tissue cells may be useful for autologous cell transplantation to defects of bone, cartilage, and tendon, if MSC can be expanded in vitro. However, a short life span of MSC and a reduction in their differentiation potential in culture have limited their clinical application. The purpose of this study is to identify a growth factor(s) involved in self-renewal of MSC and the maintenance of their multilineage differentiation potential. Fibroblast growth factor-2 (FGF-2) markedly increased the growth rate and the life span of rabbit, canine, and human bone marrow MSC in monolayer cultures. This effect of FGF-2 was more prominent in low-density cultures than in high-density cultures. In addition, all MSC expanded in vitro with FGF-2, but not without FGF-2, differentiated to chondrocytes in pellet cultures. The FGF+ MSC also retained the osteogenic and adipogenic potential throughout many mitotic divisions. These findings suggest that FGFs play a crucial role in self-renewal of MSC.

The genome is folded into domains located in either transcriptionally inert or permissive compartments. Here we used genome-wide strategies to characterize domains during B cell development. Structured Interaction Matrix Analysis revealed that CTCF occupancy was primarily associated with intra-domain interactions, whereas p300, E2A and PU.1 bound sites were associated with intra- and inter-domain interactions that are developmentally regulated. We identified a spectrum of genes that switched nuclear location during early B cell development. In progenitors the transcriptionally inactive Ebf1 locus was sequestered at the nuclear lamina, thereby preserving multipotency. Upon development into the pro-B cell stage Ebf1 and other genes switched compartments to establish de novo intra- and inter-domain interactions that are associated with a B lineage specific transcription signature.

We isolated and expanded BMSCs from human alveolar/jaw bone at a high success rate (70%). These cells had potent osteogenic potential in vitro and in vivo, although their chondrogenic and adipogenic potential was less than that of iliac cells.Introduction: Human bone marrow stromal cells (BMSCs) have osteogenic, chondrogenic, and adipogenic potential, but marrow aspiration from iliac crest is an invasive procedure. Alveolar BMSCs may be more useful for regenerative medicine, because the marrow can be aspirated from alveolar bone with minimal pain. Materials and Methods: In this study, alveolar bone marrow samples were obtained from 41 patients, 6-66 years of age, during the course of oral surgery. BMSCs were seeded and maintained in culture with 10% FBS and basic fibroblast growth factor. In addition, BMSCs were induced to differentiate into osteoblasts, chondrocytes, or adipocytes in appropriate medium. Results and Conclusion: From a small volume (0.1-3 ml) of aspirates, alveolar BMSCs expanded at a success ratio of 29/41 (70%). The success rate decreased with increasing donor age, perhaps because of age-dependent decreases in the number and proliferative capacity of BMSCs. The expanded BMSCs differentiated into osteoblasts under osteogenic conditions in 21-28 days: the mRNA levels of osteocalcin, osteopontin, and bone sialoprotein, along with the calcium level, in alveolar BMSC cultures were similar to those in iliac cultures. However, unlike iliac BMSC, alveolar BMSC showed poor chondrogenic or adipogenic potential, and similar differences were observed between canine alveolar and iliac BMSCs. Subsequently, human alveolar BMSCs attached to ␤-tricalcium phosphate were transplanted into immunodeficient mice. In transplants, new bone formed with osteoblasts and osteocytes that expressed human vimentin, human osteocalcin, and human GAPDH. These findings suggest that BMSCs have distinctive features depending on their in vivo location and that alveolar BMSCs will be useful in cell therapy for bone diseases.

In the present study, we found that hypoxia or CoCl 2 enhanced the mRNA expression of DEC2, as well as DEC1, within 24 h in chondrogenic ATDC5, 293T, and HeLa cells. In luciferase assays, the regions between ؊524 and ؊401 in the DEC1 promoter, and between ؊863 and ؊258 in the DEC2 promoter, were responsible for the hypoxia-or hypoxiainducible factor-1␣ (HIF-1␣)-induced transcription. In these regions, we identified functional hypoxia response elements (HREs) that bound to HIF-1␣ and HIF-1␤. In addition to an HIF-1 binding site consensus sequence, the DEC1 HRE had cAMP response element-like and CACAG sequences, which were also involved in the transcription activation in response to HIF-1␣. Although the DEC2 HRE did not have a cAMP response element-like or CACAG sequence, it showed a higher affinity for HIF-1 than did the DEC1 HRE. Because DEC1 and DEC2 are directly inducible by HIF-1, these transcription factors may be crucial for the adaptation to hypoxia.Recently we cloned the cDNA for the novel basic helix-loophelix (bHLH) 1 transcription factor DEC1 (BHLHB2), which was expressed at a higher level in human primary chondrocytes than in fibroblastic cells (1). A mouse ortholog (Stra13) and a rat ortholog (SHARP-2) of DEC1 were identified independently by others in the P19 embryonal carcinoma cells and rat brain, respectively (2, 3), and the mRNA of DEC1 was found in a variety of embryonic and adult tissues (1-3). In addition, we cloned a member of the DEC subfamily of bHLH proteins, DEC2 (BHLHB3), by searching the expressed sequence tags data bank (4). DEC2 is similar to SHARP-1 (3), which is a truncated molecule of DEC2 produced by a sequencing error or a minor frameshift mutant (4). The bHLH regions of DEC1 and DEC2 exhibit the highest similarities to those of Drosophila Hairy, Enhancer of split and mammal HES, which are known as transcriptional repressors with the WRPW motif, which interacts with the Groucho family members of corepressors. Although the Stra13/DEC1 and DEC2/SHARP-1 lack the WRPW motif, they also act as transcriptional repressors by a discrete mechanism (5, 6). Stra13/DEC1 interacts physically with the components of the basal transcription machineries, such as TATA-binding protein and TFIIB, and can recruit the histone deacetylase 1-Sin3A-NcoR corepressor complex through their carboxyl-terminal repression domain (5).DEC1/Stra13/SHARP-2 may be involved in the control of the proliferation and/or differentiation of chondrocytes, nerve cells, fibroblasts, and T cells (1-3, 7). The overexpression of DEC1/ Stra13 promoted a chondrogenic differentiation of the mesenchymal stem cells, 2 and a neural differentiation of the P19 cells (2). Recently, Stra13-deficient mice were generated, and it was shown that Stra13/DEC1 is a key regulator of lymphocyte activation that is vital for the maintenance of self-tolerance and constraint of autoimmunity. Other phenotypic differences between Stra13 Ϫ/Ϫ mutants and the wild-type littermates have not been reported (7). On the other hand, DEC2/SHARP-1 worked as a tran...

It is established that E2A and its antagonist, Id3, modulate developmental progression at the pre-TCR receptor (pre-TCR) and TCR checkpoints. Here we demonstrate that Id3 expression is elevated beyond the pre-TCR checkpoint, remains high in naive T cells and shows a bimodal pattern in the effector/memory population. We show how E2A promotes T-lineage specification and how pre-TCR mediated signaling affects E2A genome-wide occupancy. Thymi in Id3-deficient mice exhibited aberrant development of effector/memory cells, increased CXCR5 and Bcl6 expression, T-B cell conjugates and remarkably B cell follicles. Collectively, these data show how E2A acts globally to orchestrate T-lineage development and that Id3 antagonizes E2A activity beyond the pre-TCR checkpoint to enforce the naïve T cell fate.