MyoD-expressing progenitors are essential for skeletal myogenesis and satellite cell development

AbstractSkeletal myogenesis in the embryo is regulated by the coordinated expression of the MyoD family of muscle regulatory factors (MRFs). MyoD and Myf-5, which are the primary muscle lineage-determining factors, function in a partially redundant manner to establish muscle progenitor cell identity. Previous diphtheria toxin (DTA)-mediated ablation studies showed that MyoD+ progenitors rescue myogenesis in embryos in which Myf-5-expressing cells were targeted for ablation, raising the possibility that the regulative behavior of distinct, MRF-expressing populations explains the functional compensatory activities of these MRFs. Using MyoDiCre mice, we show that DTA-mediated ablation of MyoD-expressing cells results in the cessation of myogenesis by embryonic day 12.5 (E12.5), as assayed by myosin heavy chain (MyHC) and Myogenin staining. Importantly, MyoDiCre/+;R26DTA/+ embryos exhibited a concomitant loss of Myf-5+ progenitors, indicating that the vast majority of Myf-5+ progenitors express MyoD, a conclusion consistent with immunofluorescence analysis of Myf-5 protein expression in MyoDiCre lineage-labeled embryos. Surprisingly, staining for the paired box transcription factor, Pax7, which functions genetically upstream of MyoD in the trunk and is a marker for fetal myoblasts and satellite cell progenitors, was also lost by E12.5. Specific ablation of differentiating skeletal muscle in ACTA1Cre;R26DTA/+ embryos resulted in comparatively minor effects on MyoD+, Myf-5+ and Pax7+ progenitors, indicating that cell non-autonomous effects are unlikely to explain the rapid loss of myogenic progenitors in MyoDiCre/+;R26DTA/+ embryos. We conclude that the vast majority of myogenic cells transit through a MyoD+ state, and that MyoD+ progenitors are essential for myogenesis and stem cell development

Human Chorionic Gonadotropin modulates CXCL10 Expression through Histone Methylation in human decidua

The process of implantation, trophoblast invasion and placentation demand continuous adaptation and modifications between the trophoblast (embryonic) and the decidua (maternal). Within the decidua, the maternal immune system undergoes continued changes, as the pregnancy progress, in terms of the cell population, phenotype and production of immune factors, cytokines and chemokines. Human chorionic gonadotropin (hCG) is one of the earliest hormones produced by the blastocyst and has potent immune modulatory effects, especially in relation to T cells. We hypothesized that trophoblast-derived hCG modulates the immune population present at the maternal fetal interface by modifying the cytokine profile produced by the stromal/decidual cells. Using in vitro models from decidual samples we demonstrate that hCG inhibits CXCL10 expression by inducing H3K27me3 histone methylation, which binds to Region 4 of the CXCL10 promoter, thereby suppressing its expression. hCG-induced histone methylation is mediated through EZH2, a functional member of the PRC2 complex. Regulation of CXCL10 expression has a major impact on the capacity of endometrial stromal cells to recruit CD8 cells. We demonstrate the existence of a cross talk between the placenta (hCG) and the decidua (CXCL10) in the control of immune cell recruitment. Alterations in this immune regulatory function, such as during infection, will have detrimental effects on the success of the pregnancy.Peer reviewe

Trend of Blood Cholesterol Level in Iran: Results of Four National Surveys During 1991-2008

Trends in cholesterol level of different populations have been investigated in several studies. This study is conducted to determine the trend of cholesterol level of Iranian adults from 1990 to 2007. Data on cholesterol measurements of four national health surveys that have been carried out in Iran used in this study. Cholesterol level of 12728 adults aged 25-64 were measured in 1990-1 survey. Also in 1999, 2005, and 2007 surveys, blood cholesterol level of 18398, 52344 and 19630 have been sampled, respectively. The median of cholesterol were modeled with age for men and women separately for the four surveys using fractional polynomials. Then, trends in the median of cholesterol across these four surveys were studied. The analysis of cholesterol data over four national health surveys showed that the change in males' cholesterol level had a decreasing trend. This decreasing trend was more pronounced in ages younger than 45 years. However, the medians of cholesterol of females during 16 years of four national surveys had a varying trend. It was decreasing in ages younger than 45; but increasing in ages over 45 years. The median of the cholesterol level of males and females in 2005 survey was on average about 10 mg/dl higher in comparison with the other surveys. Our findings showed that the pattern of trend in cholesterol level of Iranian men and women adults have a considerable difference with those of the other developing and developed countries