Multiple, Interconvertible States of Human Pluripotent Stem Cells

Three recent studies, including Buecker et al. (2010), in this issue of Cell Stem Cell, report that human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) can exist in distinct but interconvertible states and describe a robust expansion of human ESCs/iPSCs that resemble mouse ESCs

And Then There Were None: No Need for Pluripotency Factors to Induce Reprogramming

While most factors used as reprogramming transgenes can be replaced by other means, Oct4 has remained essential until now. Three recent papers have now broken this barrier through the use of opposing lineage specifying transgenes and chemical modulation, thus signifying a milestone in advancing our understanding of pluripotency induction

Early intervention for spinal cord injury with human induced pluripotent stem cells oligodendrocyte progenitors

10.1371/journal.pone.0116933PLoS ONE101e011693

Molecular Imaging and Stem Cell Research

During the last decade, there has been enormous progress in understanding both multipotent stem cells such as hematopoietic stem cells and pluripotent stem cells such as embryonic stem cells and induced pluripotent stem cells. However, it has been challenging to study developmental potentials of these stem cells because they reside in complex cellular environments and aspects of their distribution, migration, engraftment, survival, proliferation, and differentiation often could not be sufficiently elucidated based on limited snapshot images of location or environment or molecular markers. Therefore, reliable imaging methods to monitor or track the fate of the stem cells are highly desirable. Both short-term and more permanent monitoring of stem cells in cultures and in live organisms have benefited from recently developed imaging approaches that are designed to investigate cell behavior and function. Confocal and multiphoton microscopy, time-lapse imaging technology, and series of noninvasive imaging technologies enable us to investigate cell behavior in the context of a live organism. In turn, the knowledge gained has brought our understanding of stem cell biology to a new level. In this review, we discuss the application of current imaging modalities for research of hematopoietic stem cells and pluripotent stem cells and the challenges ahead

An Energy Solution for Predicting Buried Pipeline Response Induced by Tunneling Based on a Uniform Ground Movement Model

The construction of shield tunnels inevitably causes displacement of the surrounding soil and additional stress and deformation of the buried pipeline. An energy solution for predicting the deformation of buried pipelines caused by tunneling is proposed in this study. First, based on the uniform ground movement model, the interval of the free displacement field of soil around the pipeline induced by tunneling is calculated. Then, we use the Pasternak model to establish the total potential energy equation of the tunnel-soil-pipeline interaction. The final settlement interval of the pipeline is obtained by solving the numerical calculation program with MATLAB. The calculation results of the energy solution are compared with the results of the centrifugal test and the reported theoretical solutions of Winkler and Pasternak, and then the applicability of the solution for predicting the pipeline response under different geotechnical conditions is verified. Combined with an engineering case, the energy method calculation results, numerical simulation results, and measured results are compared to obtain the most unfavorable position of the pipeline caused by tunneling. At the end of this study, the application steps of the proposed method in actual construction are summarized. These steps are used to predict pipeline response in order to take protective measures

Analysis on Deformation and Stress Characteristics of a Multibraced Pit-in-Pit Excavation in a Subway Transfer Station

As an important part of subway transfer station construction, pit-in-pit (PIP) excavation has always been a key object of monitoring and control. In this study, taking the PIP excavation project of Hefei metro line 4 and line 7 transfer station as the background, combined with on-site monitoring and numerical simulation, the variation law of lateral wall displacement, ground surface settlement, and strut force during the PIP excavation were analyzed. The results showed that the maximum lateral deformation of the pile caused by the excavation of the external pit accounted for 80%–90% of the total deformation and the surface settlement accounted for 70% of the total settlement. The excavation of the inner pit only made the maximum lateral wall displacement of the outer pit and the surface settlement behind the wall increase slightly, the growth rate tended to zero, and the maximum lateral deformation depth was all above the excavation surface, which indicated that, for this project, the inner excavation had little effect on the outer pit retaining structure. In addition, the increased exposure time of the soil at the bottom of the pit and the presence of the corner effect will cause the further development of the structure displacement and the surface settlement. Based on strut force measurements, using the tributary area load distribution procedure, it was obtained that 0.3γHe was used as the upper limit index of strut force in the region, where γ is the weight of the soil and He is the excavation depth of the foundation pit. The research conclusions were helpful for the construction and sustainable development of the PIP project

Scalable expansion of human induced pluripotent stem cells in the defined xeno-free E8 medium under adherent and suspension culture conditions

AbstractLarge-scale production of human induced pluripotent stem cells (hiPSCs) by robust and economic methods has been one of the major challenges for translational realization of hiPSC technology. Here we demonstrate a scalable culture system for hiPSC expansion using the E8 chemically defined and xeno-free medium under either adherent or suspension conditions. To optimize suspension conditions guided by a computational simulation, we developed a method to efficiently expand hiPSCs as undifferentiated aggregates in spinner flasks. Serial passaging of two different hiPSC lines in the spinner flasks using the E8 medium preserved their normal karyotype and expression of undifferentiated state markers of TRA-1–60, SSEA4, OCT4, and NANOG. The hiPSCs cultured in spinner flasks for more than 10 passages not only could be remained pluripotent as indicated by in vitro and in vivo assays, but also could be efficiently induced toward mesodermal and hematopoietic differentiation. Furthermore, we established a xeno-free protocol of single-cell cryopreservation and recovery for the scalable production of hiPSCs in spinner flasks. This system is the first to enable an efficient scale-up bioprocess in completely xeno-free condition for the expansion and cryopreservation of hiPSCs with the quantity and quality compliant for clinical applications