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The chemokine (C-C motif) receptor 5 (CCR5) serves as an HIV-1 co-receptor and is essential for cell infection with CCR5-tropic viruses. Loss of functional receptor protects against HIV infection. Here,we report the successful targeting of CCR5 in GFP-marked human induced pluripotent stem cells (iPSCs) using CRISPR/Cas9 with single and dual guide RNAs (gRNAs). Following CRISPER/Cas9-mediated gene editing using a single gRNA,12.5% of cell colonies demonstrated CCR5 editing,of which 22.2% showed biallelic editing as determined by a Surveyor nuclease assay and direct sequencing. The use of dual gRNAs significantly increased the efficacy of CCR5 editing to 27% with a biallelic gene alteration frequency of 41%. To ensure the homogeneity of gene editing within cells,we used single cell sorting to establish clonal iPSC lines. Single cell-derived iPSC lines with homozygous CCR5 mutations displayed the typical characteristics of pluripotent stem cells and differentiated efficiently into hematopoietic cells,including macrophages. Although macrophages from both wild-type and CCR5-edited iPSCs supported CXCR4-tropic virus replication,macrophages from CCR5-edited iPSCs were uniquely resistant to CCR5-tropic virus challenge. This study demonstrates the feasibility of applying iPSC technology for the study of the role of CCR5 in HIV infection in vitro,and generation of HIV-resistant cells for potential therapeutic applications. View Publication

The existence of a hyaluronic acid-rich node and duct system (HAR-NDS) within the lymphatic and blood vessels was demonstrated previously. The HAR-NDS was enriched with small (3.0-5.0 μm in diameter),adult stem cells with properties similar to those of the very small embryonic-like stem cells (VSELs). Sca-1(+)Lin(-)CD45(-) cells were enriched approximately 100-fold in the intravascular HAR-NDS compared with the bone marrow. We named these adult stem cells node and duct stem cells (NDSCs)." NDSCs formed colonies on C2C12 feeder layers were positive for fetal alkaline phosphatase and could be subcultured on the feeder layers. NDSCs were Oct4(+)Nanog(+)SSEA-1(+)Sox2(+) while VSELs were Oct4(+)Nanog(+)SSEA-1(+)Sox2(-). NDSCs had higher sphere-forming efficiency and proliferative potential than VSELs and they were found to differentiate into neuronal cells in vitro. Injection of NDSCs into mice partially repaired ischemic brain damage. Thus we report the discovery of potential adult stem cells that may be involved in tissue regeneration. The intravascular HAR-NDS may serve as a route that delivers these stem cells to their target tissues. View Publication

T-cell-mediated processes play an essential role in the pathogenesis of several inflammatory skin diseases such as atopic dermatitis,allergic contact dermatitis and psoriasis. The aim of this study was to investigate the role of the IL-2-inducible tyrosine kinase (Itk),an enzyme acting downstream of the T-cell receptor (TCR),in T-cell-dependent skin inflammation using three approaches. Itk knockout mice display significantly reduced inflammatory symptoms in mouse models of acute and subacute contact hypersensitivity (CHS) reactions. Systemic administration of a novel small molecule Itk inhibitor,Compound 44,created by chemical optimization of an initial high-throughput screening hit,inhibited Itk's activity with an IC50 in the nanomolar range. Compound 44 substantially reduced proinflammatory immune responses in vitro and in vivo after systemic administration in two acute CHS models. In addition,our data reveal that human Itk,comparable to its murine homologue,is expressed mainly in T cells and is increased in lesional skin from patients with atopic dermatitis and allergic contact dermatitis. Finally,silencing of Itk by RNA interference in primary human T cells efficiently blocks TCR-induced lymphokine secretion. In conclusion,Itk represents an interesting new target for the therapy of T-cell-mediated inflammatory skin diseases. View Publication

A brefeldin A (BFA)-inhibited guanine nucleotide-exchange protein (GEP) for ADP-ribosylation factors (ARF) was purified earlier from bovine brain cytosol. Cloning and expression of the cDNA confirmed that the recombinant protein (p200) is a BFA-sensitive ARF GEP. p200 contains a domain that is 50% identical in amino acid sequence to a region in yeast Sec7,termed the Sec7 domain. Sec7 domains have been identified also in other proteins with ARF GEP activity,some of which are not inhibited by BFA. To identify structural elements that influence GEP activity and its BFA sensitivity,several truncated mutants of p200 were made. Deletion of sequence C-terminal to the Sec7 domain did not affect GEP activity. A protein lacking 594 amino acids at the N terminus,as well as sequence following the Sec7 domain,also had high activity. The mutant lacking 630 N-terminal amino acids was,however,only 1% as active,as was the Sec7 domain itself (mutant lacking 697 N-terminal residues). It appears that the Sec7 domain of p200 contains the catalytic site but additional sequence (perhaps especially that between positions 595 and 630) modifies activity dramatically. Myristoylated recombinant ARFs were better than non-myristoylated as substrates; ARFs 1 and 3 were better than ARF5,and no activity was detected with ARF6. Physical interaction of the Sec7 domain with an ARF1 mutant was demonstrated,but it was much weaker than that of the cytohesin-1 Sec7 domain with the same ARF protein. Effects of BFA on p200 and all mutants with high activity were similar with approximately 50% inhibition at textless/=50 microM. The inactive BFA analogue B36 did not inhibit the Sec7 domain or p200. Thus,the Sec7 domain of p200,like that of Sec7 itself (Sata,M.,Donaldson,J. G.,Moss,J.,and Vaughan,M. (1998) Proc. Natl. Acad. Sci. U. S. A. 95,4204-4208),plays a role in BFA inhibition as well as in GEP activity,although the latter is markedly modified by other structural elements. View Publication

It is widely accepted that canonical Wnt (cWnt) signaling is required for the differentiation of osteoprogenitors into osteoblasts. Furthermore,tumor-derived secretion of the cWnt-antagonist Dickkopf-1 (Dkk-1) is known to cause bone destruction,inhibition of repair and metastasis in many bone malignancies,but its role in osteosarcoma (OS) is still under debate. In this study,we examined the role of Dkk-1in OS by engineering its overexpression in the osteochondral sarcoma line MOS-J. Consistent with the known role of Dkk-1 in osteoblast differentiation,Dkk-1 inhibited osteogenesis by the MOSJ cells themselves and also in surrounding tissue when implanted in vivo. Surprisingly,Dkk-1 also had unexpected effects on MOSJ cells in that it increased proliferation and resistance to metabolic stress in vitro and caused the formation of larger and more destructive tumors than controls upon orthotopic implantation. These effects were attributed in part to upregulation of the stress response enzyme and cancer stem cell marker aldehyde-dehydrogenase-1 (ALDH1). Direct inhibition of ALDH1 reduced viability under stressful culture conditions,whereas pharmacological inhibition of cWnt or overexpression of ALDH1 had a protective effect. Furthermore,we observed that ALDH1 was transcriptionally activated in a c-Jun-dependent manner through a pathway consisting of RhoA,MAP-kinase-kinase-4 and Jun N-terminal Kinase (JNK),indicating that noncanonical planar cell polarity-like Wnt signaling was the mechanism responsible. Together,our results therefore demonstrate that Dkk-1 enhances resistance of OS cells to stress by tipping the balance of Wnt signaling in favor of the non-canonical Jun-mediated Wnt pathways. In turn,this results in transcriptional activation of ALDH1 through Jun-responsive promoter elements. This is the first report linking Dkk-1 to tumor stress resistance,further supporting the targeting of Dkk-1 not only to prevent and treat osteolytic bone lesions but also to reduce numbers of stress-resistant tumor cells. View Publication