Current Issues and Regulations in Tendon Regeneration and Musculoskeletal Repair with Mesenchymal Stem Cells

Mesenchymal stem cells are multipotent stromal cells residing within the connective tissue of most organs. Their surface phenotype has been well described. Most commonly, mesenchymal stem cells demonstrate the ability to differentiate into mesenchymal tissues (bone, catailge, fat, etc...), however, under the proper conditions these cells can differentiate into epithelial cells and neuroectoderm derived lineages. Their developmental plasticity also depends on the ability of mesenchymal stem cells to alter the tissue microenvironment by secreting soluble factors, as well as their capacity for differentiation in tissue repair. It is the cell-matrix interaction which defines the tissue characteristics. The molecular and functional heterogeneity of this cell population may confound interpretation of their differentiation potential, but it is this heterogeneity that is believed to provide for their therapeutic efficacy. Stem cell therapies are an attractive therapeutic approach for soft tissues as they offer a vehicle for repair and regeneration at the end of a needle. The early introduction of stem cell treatments into the therapeutic armamentarium involves both commercial and non-commercial multidisciplinary partnerships and has occurred in a climate of regulatory reform, so not all the relevant information resides in the public domain, but early clinical studies have shown promising results. Against this backdrop, novel techniques and early results of a small series of tendon and musculotendinous junction interventions are being published and other ongoing studies are yet to report their results. The issue of ensuring governance of these novel technologies falls upon both the scientific community and the established licensing authorities

Early Acquisition of Neural Crest Competence During hESCs Neuralization

Background: Neural crest stem cells (NCSCs) are a transient multipotent embryonic cell population that represents a defining characteristic of vertebrates. The neural crest (NC) gives rise to many derivatives including the neurons and glia of the sensory and autonomic ganglia of the peripheral nervous system, enteric neurons and glia, melanocytes, and the cartilaginous, bony and connective tissue of the craniofacial skeleton, cephalic neuroendocrine organs, and some heart vessels. Methodology/Principal Findings: We present evidence that neural crest (NC) competence can be acquired very early when human embryonic stem cells (hESCs) are selectively neuralized towards dorsal neuroepithelium in the absence of feeder cells in fully defined conditions. When hESC-derived neurospheres are plated on fibronectin, some cells emigrate onto the substrate. These early migratory Neural Crest Stem Cells (emNCSCs) uniformly upregulate Sox10 and vimentin, downregulate N-cadherin, and remodel F-actin, consistent with a transition from neuroepithelium to a mesenchymal NC cell. Over 13% of emNCSCs upregulate CD73, a marker of mesenchymal lineage characteristic of cephalic NC and connexin 43, found on early migratory NC cells. We demonstrated that emNCSCs give rise in vitro to all NC lineages, are multipotent on clonal level, and appropriately respond to developmental factors. We suggest that human emNCSC resemble cephalic NC described in model organisms. Ex vivo emNCSCs can differentiate into neurons in Ret.k- mouse embryonic gut tissue cultures and transplanted emNCSCs incorporate into NC-derived structures but not CNS tissues in chick embryos. Conclusions/Significance: These findings will provide a framework for further studying early human NC development including the epithelial to mesenchymal transition during NC delamination

Using action research to design and evaluate sustained and inclusive engagement to improve children’s knowledge and perception of STEM careers

Previous research suggests that early experience of and exposure to the world of work is an important predictor of a child’s future involvement in a STEM career. Many interventions have focused on those in secondary education age 11 years and above. Far fewer interventions have explored the impact of STEM outreach engagements among younger age groups. This study investigates the impact of a project that delivered career-driven STEM interventions on young children’s (7–10 years old) career knowledge and perceptions over time. Using an action research approach, this study outlines 10 distinct features for designing child-centred STEM interventions. These were delivered in 6 primary schools across North-East England over a 2-year period. A STEM Career Knowledge and Aspirations Tool was used to collect data to evaluate the impact of these interventions. Children sorted 30 job cards (mix of STEM and non-STEM) into jobs they knew, and also into jobs they would like to do. Baseline data and follow up data were collected in 2015 (n = 352) and 2017 (n = 356). Data analysis suggests the sustained interventions had a particularly positive effect on girls. In 2015 prior to the interventions, girls were significantly less likely than boys to know the following STEM jobs: surveyor, technician and game tester. In 2017, following the sustained intervention, there was no significant difference between boys and girls. Furthermore, one of the STEM jobs, Engineer, showed the greatest increase in the percentage of boys and girls that wanted to do it in 2017 compared to 2015

Differential Hox expression in murine embryonic stem cell models of normal and malignant hematopoiesis

The Hox family are master transcriptional regulators of developmental processes, including hematopoiesis. The Hox regulators, caudal homeobox factors (Cdx1-4), and Meis1, along with several individual Hox proteins, are implicated in stem cell expansion during embryonic development, with gene dosage playing a significant role in the overall function of the integrated Hox network. To investigate the role of this network in normal and aberrant, early hematopoiesis, we employed an in vitro embryonic stem cell differentiation system, which recapitulates mouse developmental hematopoiesis. Expression profiles of Hox, Pbx1, and Meis1 genes were quantified at distinct stages during the hematopoietic differentiation process and compared with the effects of expressing the leukemic oncogene Tel/PDGFR;2. During normal differentiation the Hoxa cluster, Pbx1 and Meis1 predominated, with a marked reduction in the majority of Hox genes (27/39) and Meis1 occurring during hematopoietic commitment. Only the posterior Hoxa cluster genes (a9, a10, a11, and a13) maintained or increased expression at the hematopoietic colony stage. Cdx4, Meis1, and a subset of Hox genes, including a7 and a9, were differentially expressed after short-term oncogenic (Tel/PDGFR;2) induction. Whereas Hoxa4-10, b1, b2, b4, and b9 were upregulated during oncogenic driven myelomonocytic differentiation. Heterodimers between Hoxa7/Hoxa9, Meis1, and Pbx have previously been implicated in regulating target genes involved in hematopoietic stem cell (HSC) expansion and leukemic progression. These results provide direct evidence that transcriptional flux through the Hox network occurs at very early stages during hematopoietic differentiation and validates embryonic stem cell models for gaining insights into the genetic regulation of normal and malignant hematopoiesis

Cosmological Consequences of QCD Phase Transition(s) in Early Universe

We discuss the cosmological consequences of QCD phase transition(s) on the early universe. We argue that our recent knowledge about the transport properties of quark-gluon plasma (QGP) should throw additional lights on the actual time evolution of our universe. Understanding the nature of QCD phase transition(s), which can be studied in lattice gauge theory and verified in heavy ion experiments, provides an explanation for cosmological phenomenon stem from early universe.Comment: 8 pages, 2 eps figure

Characterization of interstitial stem cells in hydra by cloning

A procedure has been developed for cloning interstitial stem cells from hydra. Clones are prepared by introducing small numbers of viable cells into aggregates of nitrogen mustard-inactivated host tissue. Clones derived from added stem cells are identified after 1–2 weeks of growth by staining with toluidine blue. The incidence of clones increases with increasing input of viable cells according to one-hit Poisson statistics, indicating that clones arise from single cells. After correction for cell losses in the procedure, about 1.2% of the input cells are found to form clones. This compares with estimates from in vivo experiments of about 4% stem cells in whole hydra [David, C. N., and Gierer, A. (1974). Cell cycle kinetics and development of Hydra attenuata. III. Nerve and nematocyte differentiation. J. Cell Sci. 16, 359–375.] Differentiation of nematocytes and nerve cells in clones was analyzed by labeling precursors with [3H]thymidine and scoring labeled nerves and nematocytes 2 days later. Nine clones examined in this way contained both differentiated nerve cells and nematocytes, demonstrating that the interstitial stem cell is multipotent. This result suggests that the observed localization of nerve and nematocyte differentiation in whole hydra probably occurs at the level of stemcell determination. The observation that differentiated cells occur very early in clone development suggests that a stem cell's decision to proliferate or differentiate is regulated by shortrange feedback signals which are already saturated in young clones

REST/NRSF Knockdown Alters Survival, Lineage Differentiation and Signaling in Human Embryonic Stem Cells.

REST (RE1 silencing transcription factor), also known as NRSF (neuron-restrictive silencer factor), is a well-known transcriptional repressor of neural genes in non-neural tissues and stem cells. Dysregulation of REST activity is thought to play a role in diverse diseases including epilepsy, cancer, Down's syndrome and Huntington's disease. The role of REST/NRSF in control of human embryonic stem cell (hESC) fate has never been examined. To evaluate the role of REST in hESCs we developed an inducible REST knockdown system and examined both growth and differentiation over short and long term culture. Interestingly, we have found that altering REST levels in multiple hESC lines does not result in loss of self-renewal but instead leads to increased survival. During differentiation, REST knockdown resulted in increased MAPK/ERK and WNT signaling and increased expression of mesendoderm differentiation markers. Therefore we have uncovered a new role for REST in regulation of growth and early differentiation decisions in human embryonic stem cells

Appropriations and Stem Cell Research Arlen Specter’s Senate Legacy

Pennsylvania Republican Senator Arlen Specter sat at the center of battles over stem cell research. Focusing on Specter’s efforts allows sustained exploration of policy entrepreneurship in the Senate. Building on Fenno’s seminal work on Arlen Specter, which focused mostly on Specter’s first term in office. Specter’s early work on criminal justice policy helped to prepare him for the weighty work involved in the stem cell debate. However, it was his ascendance on the Senate Appropriations Committee, and his position on the Labor, Health, and Human Services subcommittee in particular, that allowed him to become a leader on the stem cell issue. Specter’s work on the Judiciary Committee stereotyped Specter as a “show horse,” his work on stem cell research highlights his “workhorse” qualities. I begin with an overview of agenda setting and policy entrepreneurship in Congress. The purpose of the discussion is to place Senator Arlen Specter’s legislative activities in a theoretical context. I then turn to the politics and policy that shaped the debate surrounding stem cell research. In particular, I demonstrate how the development of stem cell policy necessarily tiptoed through the minefield of abortion politics. I then discuss Senator Specter’s involvement in shaping stem cell research policy by focusing on several vignettes where his involvement illustrates the important role of the political entrepreneur. Despite what sometimes appears as “failure,” we gain insight into the role of Specter as a policy entrepreneur and this role in shaping public policy. This work contributes to the literature on Congress and public policy in several ways. Making extensive use of newly available archival material I contribute to our historical understanding of stem cell policy and its relationship to abortion policy. Focusing on Senator Arlen Specter allows us to examine how policy leaders learn and adapt to political and institutional change to realize their policy goals. It also expands our understanding of policy entrepreneurs. Many students of legislative entrepreneurship focus on legislative accomplishment—success. Specter did not pass any landmark legislation into law related to stem cell research. This study addresses a blind spot in the study of legislative entrepreneurs; the skills policy leaders use to prevent legislation from becoming la