Cheap and Simple: Human Tube Mesenchymal Stem Cells as Feeder Layer for Human Embryonic Stem Cells

Engineering of Human Pluripotent Stem Cells by AAV-mediated Gene Targeting

The role of microRNAs in self-renewal and differentiation of mesenchymal stem cells

European Stem Cell Patents: Taking the Moral High Road?

SummaryThe gap in knowledge of the molecular mechanisms underlying differentiation of human pluripotent stem cells (hPSCs) into the mesenchymal cell lineages hinders the application of hPSCs for cell-based therapy. In this study, we identified a critical role of muscle segment homeobox 2 (MSX2) in initiating and accelerating the molecular program that leads to mesenchymal stem/stromal cell (MSC) differentiation from hPSCs. Genetic deletion of MSX2 impairs hPSC differentiation into MSCs. When aided with a cocktail of soluble molecules, MSX2 ectopic expression induces hPSCs to form nearly homogeneous and fully functional MSCs. Mechanistically, MSX2 induces hPSCs to form neural crest cells, an intermediate cell stage preceding MSCs, and further differentiation by regulating TWIST1 and PRAME. Furthermore, we found that MSX2 is also required for hPSC differentiation into MSCs through mesendoderm and trophoblast. Our findings provide novel mechanistic insights into lineage specification of hPSCs to MSCs and effective strategies for applications of stem cells for regenerative medicine.

To the Editor: The molecular mechanisms and the control of smooth muscle cell (SMC) differentiation have been extensively investigated because of its therapeutic potential.1 To date, different cell types have been used to study SMC differentiation, including a variety of mouse embryonic stem cells,2 adult stem cells,3,4 and others.5 Because several fundamental differences exist between mouse and human embryonic development,6 lack of a good model system to study human SMC differentiation has hampered the progress of translating SMC knowledge to novel clinical therapies. Human embryonic stem (hES) cells provide a valuable source of cells for studying human cell differentiation and developing therapeutic potentials in regenerative medicine. Since the initial report describing the derivation of hES cells,7 a variety of studies have established in vitro differentiation strategies to several lineages. Recently, it has been demonstrated that vascular progenitors derived from hES cells could be differentiated into endothelial cells and SMCs by endothelial …

To the Editor: The article by Xue et al1 on human embryonic stem cell-derived pacemakers illustrates that embryonic stem cells differentiated into spontaneously beating cardiocytes may function as biological pacemakers and mentions a potential limitation: The intrinsic pacemaker rate was slower than desirable. They suggest that incorporating HCN pacemaker channel genes might achieve more desirable rates, an idea consistent with our published results using HCN2 in gene- and adult human mesenchymal stem cell (hMSC)-based therapies.2–4 However, certain of the comments by Xue et al misinterpret our own work on HCN-loaded hMSCs. They state that “…these modified, undifferentiated, human mesenchymal stem cells are incapable of pacing quiescent cells because the former are neither electrically active nor genuine cardiac cells” (p 19). This statement suggests a misunderstanding of the rationale and underlying biophysics of the hMSC experiments. In fact, generation of pacemaker activity does not require delivery of an “excitable differentiated cardiac cell,” but only that the delivered cell (1) carry sufficient pacemaker current and (2) make gap junctions; thus, the hMSC-myocyte pair should behave as a pacemaker unit entirely equivalent to a single heart cell with substantial if. We clearly demonstrated both …

Low Oxygen Tension and Synthetic Nanogratings Improve the Uniformity and Stemness of Human Mesenchymal Stem Cell Layer

Background: We have determined the effects of human telomerase RNA inhibiton using siRNA in tumor cells and human embryonic and mesenchymal stem cells. Methods: We selected the sequences against the predicted loop; these sequneces were comprised of nucleotides from 76 to 94 residues and from 143 to 163 residues as the target sequences, and we cloned these sequences into pU6sh75 and pU6sh143 cells. Three different kinds of cell lines were used: HeLa, SNUhES3, and human mesenchymal stem cells. The degree of inhibition of telomerase activity was assessed by TRAP assay and RT-PCR. Results: The telomerase activity of the HeLa and SNUhES3 cells were 135.3±14.5 and 109.0±18.2; these cells showed higher activity than human mesenchymal stem cells and Wi38 cells (46.3±5.0 and 26.0±12.0), which were control cells. When each of the types of cells was treated with siRNA-hTR, the transfection efficiency of pU6sh75 for the HeLa, SNUhES3, and human mesenchymal stem cells was 91.0±8.4%, 83.3±16.0% and 81.9±12.3%, respectively. In the case of pU6sh143, its transfection efficiency was similar to pU6sh75; the HeLa, SNUhES3 and human mesenchymal stem cells tranfection efficiency was 90.1±9.0%, 79.9±18.2% and 79.4±15.1%, respectively. After two days of transfection, the level of telomerase activity in the pU6sh75 transfected cells decreased to 64.3±10.1% and 56.0±11.0% in the HeLa and SNUhES3 cells, respectively. When the cells were transfected with pU6sh143, the telomerase activity also decreased in the HeLa and SNUhES3 cells (71.3±9.1% and 61.6±8.3%, respectively). However, the difference of telomerase activity was not significant in the human mesenchymal stem cells: 43.0±7.2% with pU6sh75 and 46.0±9.0% with pU6sh143. Conclusion: Telomerase RNA inhibiton with siRNA may be a feasible way to inhibit the telomerase activity of human tumor and embryonic stem cells.

Defining Human Pluripotency.

Historical Perspectives and Advances in Mesenchymal Stem Cell Research for the Treatment of Liver Diseases

Stem Cells and Drug Discovery: The Beginning of a New Era?

Embryonic stem cells are pluripotent and capable of unlimited self-renewal. Elucidation of the underlying molecular mechanism may contribute to the advancement of cell-based regenerative medicine. In the present work, we performed a large scale analysis of the phosphoproteome in mouse embryonic stem (mES) cells. Using multiplex strategies, we detected 4581 proteins and 3970 high confidence distinct phosphosites in 1642 phosphoproteins. Notably, 22 prominent phosphorylated stem cell marker proteins with 39 novel phosphosites were identified for the first time by mass spectrometry, including phosphorylation sites in NANOG (Ser-65) and RE1 silencing transcription factor (Ser-950 and Thr-953). Quantitative profiles of NANOG peptides obtained during the differentiation of mES cells revealed that the abundance of phosphopeptides and non-phosphopeptides decreased with different trends. To our knowledge, this study presents the largest global characterization of phosphorylation in mES cells. Compared with a study of ultimately differentiated tissue cells, a bioinformatics analysis of the phosphorylation data set revealed a consistent phosphorylation motif in human and mouse ES cells. Moreover, investigations into phosphorylation conservation suggested that phosphoproteins were more conserved in the undifferentiated ES cell state than in the ultimately differentiated tissue cell state. However, the opposite conclusion was drawn from this conservation comparison with phosphosites. Overall, this work provides an overview of phosphorylation in mES cells and is a valuable resource for the future understanding of basic biology in mES cells.

Global Challenges in Stem Cell Research and the Many Roads Ahead

Background: Human embryonic stem (hES) cells are pluripotent, and can differentiate into three germ layers. Traditionally, cultures of hES cells are maintained in a system containing mouse embryonic fibroblasts as a feeder layer for support of undifferentiated growth. However, contamination by animal cells limits the use of hES cells. Objective: We evaluated the use of human dental pulp stem cells (hDPSCs) as a feeder layer for hES cell culture. It should be possible to obtain a new source of human mesenchymal stem cells for feeder cells to maintain undifferentiated growth of hES cells. Methods: hDPSCs from removed impacted wisdom teeth (third molars) were extracted, cultured, and characterized for mesenchymal stem cell properties. Furthermore, hDPSCs were used as a feeder layer for culturing Chula2 and Chula5 hES cell lines. Finally, hES cell lines grown on hDPSCs feeders were examined embryonic stem cell properties. Results: We found that hDPSCs, which have mesenchymal properties, can support undifferentiated growth of hES cell lines. After prolonged culture (passage 17), these hES cell lines still maintain ES cell properties including typical morphology seen in hES cells, the expression of pluripotency markers (Oct4, Sox2, Nanog, Rex1, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81), embryoid body formation and retention of a normal karyotype. Conclusion: hDPSCs, derived from the pulp tissue of impacted third molars, are a potential source of human feeder cells for the culture of undifferentiated hES cells.

Stem Cells Derived from Human Amniotic Fluid Contribute to Acute Kidney Injury Recovery