技术资料

Human embryonic stem cells (hESCs) have the potential to generate multiple cell types and hold promise for future therapeutic applications. Although undifferentiated hESCs can proliferate indefinitely,hESC derivatives significantly downregulate telomerase and have limited replication potential. In this study we examine whether the replicative lifespan of hESC derivatives can be extended by ectopic expression of human telomerase reverse transcriptase (hTERT),the catalytic component of the telomerase complex. To this end,we have derived HEF1 cells,a fibroblast-like cell type,differentiated from hESCs. Infection of HEF1 cells with a retrovirus expressing hTERT extends their replicative capacity,resulting in immortal human HEF1-hTERT cells. HEF1-hTERT cells can be used to produce conditioned medium (CM) capable of supporting hESC growth under feeder-free conditions. Cultures maintained in HEF1-CM show characteristics similar to mouse embryonic fibroblast CM control cultures,including morphology,surface marker and transcription factor expression,telomerase activity,differentiation,and karyotypic stability. In addition,HEF1-hTERT cells have the capacity to differentiate into cells of the osteogenic lineage. These results suggest that immortalized cell lines can be generated from hESCs and that cells derived from hESCs can be used to support their own growth,creating a genotypically homogeneous system for the culture of hESCs. View Publication

Rheumatoid Arthritis (RA) causes chronic inflammation of joints. The cytokines TNFalpha and IFNgamma are central players in RA,however their source has not been fully elucidated. Natural Killer (NK) cells are best known for their role in elimination of viral-infected and transformed cells,and they secrete pro-inflammatory cytokines. NK cells are present in the synovial fluids (SFs) of RA patients and are considered to be important in bone destruction. However,the phenotype and function of NK cells in the SFs of patients with erosive deformative RA (DRA) versus non-deformative RA (NDRA) is poorly characterized. Here we characterize the NK cell populations present in the blood and SFs of DRA and NDRA patients. We demonstrate that a distinct population of activated synovial fluid NK (sfNK) cells constitutes a large proportion of immune cells found in the SFs of DRA patients. We discovered that although sfNK cells in both DRA and NDRA patients have similar phenotypes,they function differently. The DRA sfNK secrete more TNFalpha and IFNgamma upon exposure to IL-2 and IL-15. Consequently,we suggest that sfNK cells may be a marker for more severely destructive RA disease. View Publication

Background and Aims Epithelial expression of the insulin receptor in the colon has previously been reported to correlate with extent of colonic inflammation. However,the impact of insulin signalling in the intestinal mucosa is still unknown. Here,we investigated the effects of inactivating the epithelial insulin receptor in the intestinal tract,in an experimental model of inflammation-induced colorectal cancer. Methods The mice were generated by utilizing the intestinal- and epithelial-specific villin promoter and the Cre-Lox technology. All mice included in the cohorts were generated by crossing [vil-Cre-INSR+/-] × [INSRfl/fl] to obtain [vil-Cre-INSR-/-],and their floxed littermates [INSRfl/fl] served as the control group. For the intervention study,phosphate-buffered saline with or without insulin was instilled rectally in anaesthetized wild-type mice with chemically induced colitis. Results We found higher endoscopic colitis scores together with potentiated colonic tumorigenesis in the knockout mice. Furthermore,we showed that topically administered insulin in inflamed colons of wild-type mice reduced inflammation-induced weight loss and improved remission in a dose-dependent manner. Mice receiving rectal insulin enemas exhibited lower colitis endoscopic scores and reduced cyclooxygenase 2 mRNA expression,and developed significantly fewer and smaller tumours compared with the control group receiving phosphate-buffered saline only. Conclusions Rectal insulin therapy could potentially be a novel treatment,targeting the epithelial layer to enhance mucosal healing in ulcerated areas. Our findings open up new possibilities for combination treatments to synergize with the existing anti-inflammatory therapies. View Publication

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia in the United States and globally. Despite the availability of pneumococcal capsular polysaccharide (PPS) and protein conjugate-based vaccines,the prevalence of antibiotic-resistant pneumococcal strains,serotype (ST) replacement in nonconjugate vaccine strains,and uncertainty as to whether the PPS vaccine that is used in adults protects against pneumonia emphasize the need for continued efforts to understand the nature of protective PPS antibody responses. In this study,we generated mouse monoclonal antibodies (MAbs) to a conjugate consisting of the PPS of serotype 8 (PPS8) S. pneumoniae and tetanus toxoid. Thirteen MAbs,including four IgMs that bound to PPS8 and phosphorylcholine (PC) and five IgMs and four IgG1s that bound to PPS8 but not PC,were produced,and their nucleotide sequences,epitope and fine specificity,and efficacy against lethal challenge with ST8 S. pneumoniae were determined. MAbs that bound to PPS8 exhibited gene use that was distinct from that exhibited by MAbs that bound to PC. Only PPS8-binding MAbs that did not bind PC were protective in mice. All 13 MAbs used germ line variable-region heavy (V(H)) and light (V(L)) chain genes,with no evidence of somatic hypermutation. Our data reveal a relationship between PPS specificity and V(H) gene use and MAb efficacy in mice. These findings provide insight into the relationship between antibody molecular structure and function and hold promise for the development of novel surrogates for pneumococcal vaccine efficacy. View Publication

Haploinsufficiency for ribosomal protein genes has been implicated in the pathophysiology of Diamond-Blackfan anemia (DBA) and the 5q-syndrome,a subtype of myelodysplastic syndrome. The p53 pathway is activated by ribosome dysfunction,but the molecular basis for selective impairment of the erythroid lineage in disorders of ribosome function has not been determined. We found that p53 accumulates selectively in the erythroid lineage in primary human hematopoietic progenitor cells after expression of shRNAs targeting RPS14,the ribosomal protein gene deleted in the 5q-syndrome,or RPS19,the most commonly mutated gene in DBA. Induction of p53 led to lineage-specific accumulation of p21 and consequent cell cycle arrest in erythroid progenitor cells. Pharmacologic inhibition of p53 rescued the erythroid defect,whereas nutlin-3,a compound that activates p53 through inhibition of HDM2,selectively impaired erythropoiesis. In bone marrow biopsies from patients with DBA or del(5q) myelodysplastic syndrome,we found an accumulation of nuclear p53 staining in erythroid progenitor cells that was not present in control samples. Our findings indicate that the erythroid lineage has a low threshold for the induction of p53,providing a basis for the failure of erythropoiesis in the 5q-syndrome,DBA,and perhaps other bone marrow failure syndromes. View Publication

Th17 cells play a significant role in inflammatory and autoimmune responses. Although a number of molecular pathways that contribute to the lineage differentiation of T cells have been discovered,the mechanisms by which lineage commitment occurs are not fully understood. Transcription factors play a key role in driving T cells toward specific lineages. We have identified a role for the transcription factor Kruppel-like factor (KLF) 4 in the development of IL-17-producing CD4(+) T cells. KLF4 was required for the production of IL-17,and further,chromatin immunoprecipitation analysis demonstrated binding of KLF4 to the IL-17 promoter,indicating a direct effect on the regulation of IL-17. Further,KLF4-deficient T cells upregulated expression of retinoic acid-related orphan receptor γt similar to wild-type during the polarization process toward Th17,suggesting that these two transcription factors are regulated independently. View Publication

In vitro differentiation of embryonic stem cells is tightly regulated by the same key signaling pathways that control pattern formation during embryogenesis. Small molecules that selectively target these developmental pathways,including Wnt,and BMP signaling may be valuable for directing differentiation of pluripotent stem cells toward many desired tissue types,but to date only few such compounds have been shown to promote cardiac differentiation. Here,we show that XAV939,a recently discovered small molecule inhibitor of Wnt/β-catenin signaling,can robustly induce cardiomyogenesis in mouse ES cells. Our results suggest that a timely administration of XAV939 immediately following the formation of mesoderm progenitor cells promotes cardiomyogenic development at the expense of other mesoderm derived lineages,including the endothelial,smooth muscle,and hematopoietic lineages. Given the critical role that Wnt/β-catenin signaling plays in many aspects of embryogenesis and tissue regeneration,XAV939 is a valuable chemical probe to dissect in vitro differentiation of stem cells and to explore their regenerative potential in a variety of contexts. View Publication

The cell surface antigen,epithelial glycoprotein,defined by the monoclonal antibody HEA 125,is expressed on virtually all epithelial cell membranes but not on mesodermal or neural cell membranes. The cDNA encoding epithelial glycoprotein was isolated by HEA 125 antibody enrichment of colon tumor cDNA expressed transiently in COS cells. The sequence of the epithelial glycoprotein antigen is identical to the cell membrane protein recognized by the monoclonal antibody KS 1/4 and is homologous to the tumor-associated antigen GA733. These proteins share sequence homology to nidogen,an extracellular matrix component that appears to participate in cell-matrix adhesion. These proteins also share a homologous domain found in the B1 chain of laminin,a matrix adhesion protein,and placental protein 12,an insulin-like growth factor I binding protein secreted during pregnancy that has been implicated in regulation of fetal growth. This common domain is also repeated multiple times within the thyroglobulin precursor. These findings suggest epithelial glycoprotein is a cell surface molecule involved in cell-cell or cell-matrix interaction. View Publication

The Mediator complex forms the bridge between transcriptional activators and the RNA polymerase II. Med1 (also known as PBP or TRAP220) is a key component of Mediator that interacts with nuclear hormone receptors and GATA transcription factors. Here,we show dynamic recruitment of GATA-1,TFIIB,Mediator,and RNA polymerase II to the β-globin locus in induced mouse erythroid leukemia cells and in an erythropoietin-inducible hematopoietic progenitor cell line. Using Med1 conditional knockout mice,we demonstrate a specific block in erythroid development but not in myeloid or lymphoid development,highlighted by the complete absence of β-globin gene expression. Thus,Mediator subunit Med1 plays a pivotal role in erythroid development and in β-globin gene activation. View Publication

SPARC is an extracellular matrix protein that exerts pleiotropic effects on extracellular matrix organization,growth factor availability,cell adhesion,differentiation,and immunity in cancer. Chronic myelogenous leukemia (CML) cells resistant to the BCR-ABL inhibitor imatinib (IM-R cells) were found to overexpress SPARC mRNA. In this study,we show that imatinib triggers SPARC accumulation in a variety of tyrosine kinase inhibitor (TKI)-resistant CML cell lines. SPARC silencing in IM-R cells restored imatinib sensitivity,whereas enforced SPARC expression in imatinib-sensitive cells promoted viability as well as protection against imatinib-mediated apoptosis. Notably,we found that the protective effect of SPARC required intracellular retention inside cells. Accordingly,SPARC was not secreted into the culture medium of IM-R cells. Increased SPARC expression was intimately linked to persistent activation of the Fyn/ERK kinase signaling axis. Pharmacologic inhibition of this pathway or siRNA-mediated knockdown of Fyn kinase resensitized IM-R cells to imatinib. In support of our findings,increased levels of SPARC mRNA were documented in blood cells from CML patients after 1 year of imatinib therapy compared with initial diagnosis. Taken together,our results highlight an important role for the Fyn/ERK signaling pathway in imatinib-resistant cells that is driven by accumulation of intracellular SPARC. View Publication

Recent studies have demonstrated that cancer stem cells play an important role in the pathobiology of head and neck squamous cell carcinomas (HNSCC). However,little is known about functional interactions between head and neck cancer stem-like cells (CSC) and surrounding stromal cells. Here,we used aldehyde dehydrogenase activity and CD44 expression to sort putative stem cells from primary human HNSCC. Implantation of 1,000 CSC (ALDH+CD44+Lin-) led to tumors in 13 (out of 15) mice,whereas 10,000 noncancer stem cells (ALDH-CD44-Lin-) resulted in 2 tumors in 15 mice. These data demonstrated that ALDH and CD44 select a subpopulation of cells that are highly tumorigenic. The ability to self-renew was confirmed by the observation that ALDH+CD44+Lin- cells sorted from human HNSCC formed more spheroids (orospheres) in 3-D agarose matrices or ultra-low attachment plates than controls and were serially passaged in vivo. We observed that approximately 80% of the CSC were located in close proximity (within 100-μm radius) of blood vessels in human tumors,suggesting the existence of perivascular niches in HNSCC. In vitro studies demonstrated that endothelial cell-secreted factors promoted self-renewal of CSC,as demonstrated by the upregulation of Bmi-1 expression and the increase in the number of orospheres as compared with controls. Notably,selective ablation of tumor-associated endothelial cells stably transduced with a caspase-based artificial death switch (iCaspase-9) caused a marked reduction in the fraction of CSC in xenograft tumors. Collectively,these findings indicate that endothelial cell-initiated signaling can enhance the survival and self-renewal of head and neck CSC. View Publication

Fibrosis is a pathological feature observed in patients with Duchenne muscular dystrophy (DMD) and in mdx mice,the experimental model of DMD. We evaluated the effect of suramin,a transforming growth factor-beta 1 (TGF-β1) blocker,on fibrosis in mdx mice. mdx mice (6 months old) received suramin for 7 weeks. Suramin- and saline-treated (control) mdx mice performed exercise on a treadmill to worsen disease progression. Immunoblotting showed an increase of TGF-β1 in mdx diaphragm,limb,and cardiac muscles. Suramin decreased creatine kinase in mdx mice and attenuated fibrosis in all muscles studied,except for cardiac muscle. Suramin protected limb muscles against damage and reduced the exercise-induced loss of strength over time. These findings support a role for TGF-β1 in fibrinogenesis and myonecrosis during the later stages of disease in mdx mice. Suramin might be a useful therapeutic alternative for the treatment of dystrophinopathies. View Publication