No abstract

A superparamagnetic iron oxide (SPIO) nanoparticle is emerging as an ideal probe for noninvasive cell tracking. However, its low intracellular labeling efficiency has limited the potential usage and has evoked great interest in developing new labeling strategies. We have developed fluorescein isothiocyanate (FITC)-incorporated silica-coated core-shell SPIO nanoparticles, SPIO@SiO2(FITC), with diameters of 50 nm, as a bifunctionally magnetic vector that can efficiently label human mesenchymal stem cells (hMSCs), via clathrin- and actin-dependent endocytosis with subsequent intracellular localization in late endosomes/lysosomes. The uptake process displays a time- and dose-dependent behavior. In our system, SPIO@SiO2(FITC) nanoparticles induce sufficient cell MRI contrast at an incubation dosage as low as 0.5 microg of iron/mL of culture medium with 1.2x105 hMSCs, and the in vitro detection threshold of cell number is about 1x104 cells. Furthermore, 1.2x105 labeled cells can also be MRI-detected in a subcutaneous model in vivo. Labeled hMSCs are unaffected in their viability, proliferation, and differentiation capacities into adipocytes and osteocytes which can still be readily MRI detected. This is the first report that hMSCs can be efficiently labeled with MRI contrast nanoparticles and can be monitored in vitro and in vivo with a clinical 1.5-T MRI imager under low incubation concentration of iron oxide, short incubation time, and low detection cell numbers at the same time.

Current sources of stem cells include embryonic stem cells (ESCs) and adult stem cells (ASCs). However, concerns exist with either source: ESCs, with their significant ethical considerations, tumorigenicity, and paucity of cell lines; and ASCs, which are possibly more limited in potential. Thus, the search continues for an ethically conducive, easily accessible, and high-yielding source of stem cells. We have isolated a population of multipotent cells from the human term placenta, a temporary organ with fetal contributions that is discarded postpartum. These placenta-derived multipotent cells (PDMCs) exhibit many markers common to mesenchymal stem cells-including CD105/endoglin/SH-2, SH-3, and SH-4-and they lack hematopoietic-, endothelial-, and trophoblastic-specific cell markers. In addition, PDMCs exhibit ESC surface markers of SSEA-4, TRA-1-61, and TRA-1-80. Adipogenic, osteogenic, and neurogenic differentiation were achieved after culturing under the appropriate conditions. PDMCs could provide an ethically uncontroversial and easily accessible source of multipotent cells for future experimental and clinical applications. Stem Cells 2005;23:3-9

No abstract

Several types of nonhematopoietic stem cells, including bone marrow mesenchymal stem cells (BMMSCs) and embryonic stem cells, have been shown to have immunosuppressive properties. We show that human placenta-derived multipotent cells (PDMCs), which are isolated from a source without ethical concern and harbor multilineage differentiation potential, have strong immunosuppressive properties. PDMCs suppress both mitogen-induced and allogeneic lymphocyte proliferation in both CD4 and CD8 populations. The immunosuppression seen with PDMCs was significantly stronger than that with BMMSCs. Both PDMCs and BMMSCs express indoleamine 2,3-dioxygenase, but only PDMCs are positive for intracellular human leukocyte antigen-G (HLA). Mechanistically, suppression of lymphocyte reactivity by PDMCs is not due to cell death but to decreased cell proliferation and increased numbers of regulatory T cells. Addition of neutralizing antibodies to interleukin-10 and transforming growth factor (TGF)-␤ partially restored lymphocyte proliferation. Unlike BMMSCs, PDMCs treated with interferon-␥ for 3 days only very minimally upregulated HLA-DR. On the contrary, PD-L1, a cell surface marker that plays an inhibitory role in T-cell activation, was upregulated and TGF-␤ expression was seen. The immunosuppressive properties of PDMCs, along with their multilineage differentiation potential, ease of accessibility, and abundant cell numbers, may render these cells as good potential sources for future therapeutic applications. STEM

No abstract

DNMT3A mutations are associated with poor prognosis in acute myeloid leukemia (AML), but the stability of this mutation during the clinical course remains unclear. In the present study of 500 patients with de novo AML, DNMT3A mutations were identified in 14% of total patients and in 22.9% of AML patients with normal karyotype. DNMT3A mutations were positively associated with older age, higher WBC and platelet counts, intermediate-risk and normal cytogenetics, FLT3 internal tandem duplication, and NPM1, PTPN11, and IDH2 mutations, but were negatively associated with CEBPA mutations. Multivariate analysis demonstrated that the DNMT3A mutation was an independent poor prognostic factor for overall survival and relapse-free survival in total patients and also in normokaryotype group. A scoring system incorporating the DNMT3A mutation and 8 other prognostic factors, including age, WBC count, cytogenetics, and gene mutations, into survival analysis was very useful in stratifying AML patients into different prognostic groups (P < .001). Sequential study of 138 patients during the clinical course showed that DNMT3A mutations were stable during AML evolution. In conclusion, DNMT3A mutations are associated with distinct clinical and biologic features and poor prognosis in de novo AML patients. Furthermore, the DNMT3A mutation may be a potential biomarker for monitoring of minimal residual disease. (Blood. 2012;119(2):559-568)

Tracking the distribution of stem cells is crucial to their therapeutic use. However, the usage of current vectors in cellular labeling is restricted by their low internalizing efficiency. Here, we reported a cellular labeling approach with a novel vector composed of mesoporous silica nanoparticles (MSNs) conjugated with fluorescein isothiocyanate in human bone marrow mesenchymal stem cells and 3T3-L1 cells, and the mechanism about fluorescein isothiocyanate-conjugated MSNs (FITC-MSNs) internalization was studied. FITC-MSNs were efficiently internalized into mesenchymal stem cells and 3T3-L1 cells even in short-term incubation. The process displayed a time- and concentration-dependent manner and was dependent on clathrin-mediated endocytosis. In addition, clathrin-dependent endocytosis seemed to play a decisive role on more internalization and longer stay of FITC-MSNs in mesenchymal stem cells than in 3T3-L1 cells. The internalization of FITC-MSNs did not affect the cell viability, proliferation, immunophenotype, and differentiation potential of mesenchymal stem cells, and 3T3-L1 cells. Finally, FITC-MSNs could escape from endolysosomal vesicles and were retained the architectonic integrity after internalization. We conclude that the advantages of biocompatibility, durability, and higher efficiency in internalization suit MSNs to be a better vector for stem cell tracking than others currently used.