There is much interest in using embryonic stem cells to regenerate tissues and organs. For this approach to succeed, these stem cells or their derivatives must engraft in patients over the long term. Unless a cell transplant is derived from the patient's own cells, however, the cells will be targeted for rejection by the immune system. Although standard methods for suppressing the immune system achieve some success, rejection of the transplant is inevitable. Emerging approaches to address this issue include 're-educating' the immune system to induce tolerance to foreign cells and reducing the immune targeting of the transplant by administering 'self stem cells' instead of foreign cells, but each of these approaches has associated challenges.

Replication timing is an important developmentally-regulated regional property that is correlated with chromosome structure and gene expression, but little is known about the establishment and maintenance of these patterns. Here we followed the fate of replication timing patterns in cells that undergo reprogramming either through somatic-cell nuclear transplantation (SCNT) or by the generation of induced pluripotential stem (iPS) cells. We have investigated three different paradigms, stage-specific replication timing, parental allele-specific asynchrony (imprinted regions) and random allelic asynchronous replication. In all cases, somatic replication timing patterns were reset exactly at the appropriate stage in early development and could be properly established upon re-differentiation. Taken together, these results suggest that unlike DNA methylation, the molecular mechanisms governing replication timing are not only stable, but can also be easily reprogrammed.

ABSTRACT: Human stem cells are in evaluation in clinical stem cell trials, primarily as autologous bone marrow studies, autologous and allogenic mesenchymal stem cell trials, and some allogenic neural stem cell transplantation projects. Safety and efficacy are being addressed for a number of disease state applications. There is considerable data supporting safety of bone marrow and mesenchymal stem cell transplants but the efficacy data are variable and of mixed benefit. Mechanisms of action of many of these cells are unknown and this raises the concern of unpredictable results in the future. Nevertheless there is considerable optimism that immune suppression and anti-inflammatory properties of mesenchymal stem cells will be of benefit for many conditions such as graft versus host disease, solid organ transplants and pulmonary fibrosis. Where bone marrow and mesenchymal stem cells are being studied for heart disease, stroke and other neurodegenerative disorders, again progress is mixed and mostly without significant benefit. However, correction of multiple sclerosis, at least in the short term is encouraging. Clinical trials on the use of embryonic stem cell derivatives for spinal injury and macular degeneration are beginning and a raft of other clinical trials can be expected soon, for example, the use of neural stem cells for killing inoperable glioma and embryonic stem cells for regenerating b islet cells for diabetes. The change in attitude to embryonic stem cell research with the incoming Obama administration heralds a new co-operative environment for study and evaluation of stem cell therapies. The Californian stem cell initiative (California Institute for Regenerative Medicine) has engendered global collaboration for this new medicine that will now also be supported by the US Federal Government. The active participation of governments, academia, biotechnology, pharmaceutical companies, and private investment is a powerful consortium for advances in health.

Measuring the dynamics of plant growth is fundamental to the understanding of plant development processes. This paper describes a high throughput, automatic method to trace Arabidopsis thaliana seedling roots grown on agarose plates. From the trace, additional software can quantify length, curvature and stimulus response parameters such as onset of gravitropism. The method combines a particle filtering algorithm with a graph-based method to trace the centre-line of a root. This top-down approach is robust to a variety of noise effects, and is reasonably flexible across different image sets. The resulting tool requires minimal interaction from the user, and is able to process long timelapse sequences with user interaction only required on the first frame. The tool is described first, followed by its use on two sample datasets, one measuring root lengths and the other additionally analysing the gravitropic response and curvature. The tool, RootTrace is open source; both the program and source code will be available online.

Acute respiratory distress syndrome is characterized by loss of lung tissue as a result of inflammation and fibrosis. Augmenting tissue repair by the use of mesenchymal stem cells may be an important advance in treating this condition. We evaluated the role of term human umbilical cord cells derived from Wharton's jelly with a phenotype consistent with mesenchymal stem cells (uMSCs) in the treatment of a bleomycin-induced mouse model of lung injury. uMSCs were administered systemically, and lungs were harvested at 7, 14, and 28 days post-bleomycin. Injected uMSCs were located in the lung 2 weeks later only in areas of inflammation and fibrosis but not in healthy lung tissue. The administration of uMSCs reduced inflammation and inhibited the expression of transforming growth factor-beta, interferon-gamma, and the proinflammatory cytokines macrophage migratory inhibitory factor and tumor necrosis factor-alpha. Collagen concentration in the lung was significantly reduced by uMSC treatment, which may have been a consequence of the simultaneous reduction in Smad2 phosphorylation (transforming growth factor-beta activity). uMSCs also increased matrix metalloproteinase-2 levels and reduced their endogenous inhibitors, tissue inhibitors of matrix metalloproteinases, favoring a pro-degradative milieu following collagen deposition. Notably, injected human lung fibroblasts did not influence either collagen or matrix metalloproteinase levels in the lung. The results of this study suggest that uMSCs have antifibrotic properties and may augment lung repair if used to treat acute respiratory distress syndrome.

An important problem in neuroscience is to obtain quantitative knowledge of how information is represented, or encoded, in the signals that nerve cells process and transmit. Sensory receptors have provided important models for the study of neural coding because their inputs can often be relatively easily controlled and measured, while the resultant activity is recorded. A variety of engineering concepts have been successfully applied to physiological sciences, particularly those related to control of dynamic systems. Linear systems analysis was one of the earliest methods used to probe sensory coding, and measurements such as step responses and frequency responses have become standard tools for describing sensory functions. Modern systems analysis has evolved to provide accurate and efficient linear identification of encoding in sensory receptors that use either graded potentials or action potentials. It has also led to nonlinear systems analysis, the creation of parametric nonlinear models, and measures of information coding by sensory neurons. These methods promise to provide important new knowledge about sensory systems in the future, especially when complemented with parallel biophysical and molecular studies of sensory neurons. Mechanoreceptors provided some of the earliest preparations for the investigation of neural coding, and both the linear and nonlinear properties of wide variety of vertebrate and invertebrate mechanoreceptors continue to be explored.

Human embryonic stem cells (HESCs) carrying specific mutations potentially provide a valuable tool for studying genetic disorders in humans. One preferable approach for obtaining these cell lines is by deriving them from affected preimplantation genetically diagnosed embryos. These unique cells are especially important for modeling human genetic disorders for which there are no adequate research models. They can be further used to gain new insights into developmentally regulated events that occur during human embryo development and that are responsible for the manifestation of genetically inherited disorders. They also have great value for the exploration of new therapeutic protocols, including gene-therapy-based treatments and disease-oriented drug screening and discovery. Here, we report the establishment of 15 different mutant human embryonic stem cell lines derived from genetically affected embryos, all donated by couples undergoing preimplantation genetic diagnosis in our in vitro fertilization unit. For further information regarding access to HESC lines from our repository, for research purposes, please email dalitb@tasmc.health.gov.il.

The use of iPSCs and tetraploid complementation for human reproductive cloning would raise profound ethical objections. Professional standards and laws that ban human reproductive cloning by somatic cell nuclear transfer should be revised to also forbid it by other methods, such as iPSCs via tetraploid complementation.

Research in human pluripotent stem cells, including human embryonic stem cells (hESC) and human induced pluripotent stem cells (hiPSC), is one of the most dynamic research fields. Despite the high public attention especially for hESC research, there is only scattered information on the number of hESC lines, the degree, dynamics and diversification of their use on a global level. In this study we present data on the current number of publicly disclosed hESC lines, on the extent and impact of experimental work involving hESCs and on the use of specific hESC lines in international research. The results are based on the evaluation of nearly 1000 research papers published by the end of 2008 and describing experimental work on hESCs and a comprehensive database of published hESC lines. The average impact of hESC research papers is high at 7.422, with a predominance of research output by the United States. Of at least 1071 original hESC lines derived until November 2009 at 87 institutions in 24 countries, only a fraction is thoroughly characterized. Our data show the global predominance of a few hESC lines in research, but also reveal remarkable country-specific differences. Comparison of hESC and hiPSC application did not show a diminished role for hESC research, but rather revealed that until now, both fields further expand, exist independently and partially overlap.

Somatic cell nuclear transfer or therapeutic cloning has provided great hope for stem cell-based therapies. However, therapeutic cloning has been experiencing both ethical and technical difficulties. Recent breakthrough studies using a combination of four factors to reprogram human somatic cells into pluripotent stem cells without using embryos or eggs have led to an important revolution in stem cell research. Comparative analysis of human induced pluripotent stem cells and human embryonic stem cells using assays for morphology, cell surface marker expression, gene expression profiling, epigenetic status, and differentiation potential have revealed a remarkable degree of similarity between these two pluripotent stem cell types. This mini-review summarizes these ground-breaking studies. These advances in reprogramming will enable the creation of patient-specific stem cell lines to study various disease mechanisms. The cellular models created will provide valuable tools for drug discovery. Furthermore, this reprogramming system provides great potential to design customized patient-specific stem cell therapies with economic feasibility.

The differentiation potential of embryonic stem (ES) cells seems to be higher when compared to adult stem cells, which mainly differentiate into certain tissue types only. ES cells have the potential to play an important role in regenerative medicine as demonstrated with murine ES cells. However, with human embryonic stem cells (hESC) several obstacles still have to be overcome, when these are to be used in clinical applications. The expansion of hESC, safety issues as well as the immune-tolerance after transplantation are all problems that still have to be solved. Since 2005 the derivation of hESC lines from super-numerous embryos has become permitted in Switzerland, albeit under strictly restrictive guidelines. In 2008 the Basler hESC laboratory was successful in derivating the first hESC line with a normal chromosome complement in Switzerland (CHES2). Now, new applications allow the personalized establishment of immune-tolerant stem cells, which lead to the replacement of therapeutic cloning by induced pluripotent stem cells (iPS).

The discovery of human embryonic stem cells (hESCs) raised promises for a universal resource for cell based therapies in regenerative medicine. Recently, fast-paced progress has been made towards the generation of pluripotent stem cells (PSCs) amenable for clinical applications, culminating in reprogramming of adult somatic cells to autologous PSCs that can be indefinitely expanded in vitro. However, besides the efficient generation of bona fide, clinically safe PSCs (e.g., without the use of oncoproteins and gene transfer based on viruses inserting randomly into the genome), a major challenge in the field remains how to efficiently differentiate PSCs to specific lineages and how to select cells that will function normally upon transplantation in adults. In this review, we analyse the in vitro differentiation potential of PSCs to the hematopoietic lineage by discussing blood cell types that can be currently obtained, limitations in derivation of adult-type HSCs and prospects for clinical application of PSCs-derived blood cells.

Recent seminal discoveries have significantly advanced the field of stem cell research and received worldwide attention. Improvements in somatic cell nuclear transfer (SCNT) technology, enabling the cloning of Dolly the sheep, and the derivation and differentiation of human embryonic stem cells raised hopes that normal cells could be generated to replace diseased or injured tissue. At the same time, in vitro and in vivo studies demonstrated that somatic cells of one tissue are capable of generating cells of another tissue. It was theorized that any cell might be reprogrammed, by exposure to a new environment, to become another cell type. This concept contradicts two established hypotheses:(1) that only specific tissues are generated from the endoderm, mesoderm, and ectoderm and (2) that tissue cells arise from a rare population of tissue-specific stem cells in a hierarchical fashion. SCNT, cell fusion experiments, and most recent gene transfer studies also contradict these hypotheses, as they demonstrate that mature somatic cells can be reprogrammed to regain pluripotent (or even totipotent) stem cell capacity. On the basis of the stem cell theory, hierarchical cancer stem cell differentiation models have been proposed. Cancer cell plasticity is an established phenomenon that supports the notion that cellular phenotype and function might be altered. Therefore, mechanisms of cellular plasticity should be exploited and the clinical significance of the cancer stem cell theory cautiously assessed.

It is well known that oocytes can reprogram differentiated cells, allowing animal cloning by nuclear transfer. We have recently shown that fertilized zygotes retain reprogramming activities, suggesting that such activities might also persist in cleavage-stage embryos. Here, we used chromosome transplantation techniques to investigate whether the blastomeres of two-cell-stage mouse embryos can reprogram more differentiated cells. When chromosomes from one of the two blastomeres were replaced with the chromosomes of an embryonic or CD4(+) T lymphocyte donor cell, we observed nuclear reprogramming and efficient contribution of the manipulated cell to the developing blastocyst. Embryos produced by this method could be used to derive stem cell lines and also developed to term, generating mosaic "cloned" animals. These results demonstrate that blastomeres retain reprogramming activities and support the notion that discarded human preimplantation embryos may be useful recipients for the production of genetically tailored human embryonic stem cell lines.

We examine whether the current regulatory regime instituted in South Korea and the United States would have prevented Hwang's potential transgressions in oocyte procurement for somatic cell nuclear transfer, we compare the general aspects and oversight framework of the Bioethics and Biosafety Act in South Korea and the US National Academies' Guidelines for Human Embryonic Stem Cell Research, and apply the relevant provisions and recommendations to each transgression. We conclude that the Act would institute centralized oversight under governmental auspices while the Guidelines recommend politically-independent, decentralized oversight bodies including a special review body for human embryonic stem cell research at an institutional level and that the Guidelines would have provided more vigorous protection for the women who had undergone oocyte procurement for Hwang's research than the Act. We also suggest additional regulations to protect those who provide oocytes for research in South Korea.