ABSTRACT
Bone marrow–derived mesenchymal stem cells (MSCs) have been recently used in clinical trials as treatment for liver diseases. However, the underlying mechanism of their effectiveness remains ...largely unexplored. In the present study, we confirmed that the protective effects of MSCs on mouse model of acute liver failure (ALF) were based on MSC‐secreted prostaglandin (PG)E2. Our data confirmed that MSC‐secreted PGE2 not only inhibited apoptosis but also enhanced hepatocyte proliferation, thus attenuating ALF. Moreover, Yes‐associated protein (YAP) played a major role in PGE2‐triggered hepatocyte proliferation. In vitro studies showed that PGE2 increased the expression of PGE4 and enhanced the phosphorylation of cAMP response element binding protein, resulting in YAP activation and increased expression of YAP‐related genes. Furthermore, the mammalian target of rapamycin, another major regulator of cell proliferation, was activated by YAP via suppressing phosphatase and tensin homolog through miR‐29a‐3p. These pathways coordinated to control cell proliferation. Collectively, MSCs could promote the recovery of ALF through PGE2‐induced hepatocyte proliferation.—Liu, Y., Ren, H., Wang, J., Yang, F., Li, J., Zhou, Y., Yuan, X., Zhu, W., Shi, X. Prostaglandin E2 secreted by mesenchymal stem cells protects against acute liver failure via enhancing hepatocyte proliferation. FASEB J. 33, 2599–2609 (2019). www.fasebj.org
The high incidence of aneuploidy in the embryo is considered the principal cause for low human fecundity. However, the prevalence of aneuploidy dramatically declines as pregnancy progresses, with the ...steepest drop occurring as the embryo completes implantation. Despite the fact that the plasticity of the embryo in dealing with aneuploidy is fundamental to normal development, the mechanisms responsible for eliminating aneuploid cells are unclear. Here, using a mouse model of chromosome mosaicism, we show that aneuploid cells are preferentially eliminated from the embryonic lineage in a p53-dependent process involving both autophagy and apoptosis before, during and after implantation. Moreover, we show that diploid cells in mosaic embryos undertake compensatory proliferation during the implantation stages to confer embryonic viability. Together, our results indicate a close link between aneuploidy, autophagy, and apoptosis to refine the embryonic cell population and ensure only chromosomally fit cells proceed through development of the fetus.
Newborn microglia rapidly replenish the whole brain after selective elimination of most microglia (>99%) in adult mice. Previous studies reported that repopulated microglia were largely derived from ...microglial progenitor cells expressing nestin in the brain. However, the origin of these repopulated microglia has been hotly debated. In this study, we investigated the origin of repopulated microglia by a series of fate-mapping approaches. We first excluded the blood origin of repopulated microglia via parabiosis. With different transgenic mouse lines, we then demonstrated that all repopulated microglia were derived from the proliferation of the few surviving microglia (<1%). Despite a transient pattern of nestin expression in newly forming microglia, none of repopulated microglia were derived from nestin-positive non-microglial cells. In summary, we conclude that repopulated microglia are solely derived from residual microglia rather than de novo progenitors, suggesting the absence of microglial progenitor cells in the adult brain.
The cell proliferation antigen Ki-67 is widely used in cancer histopathology, but estimations of Ki-67 expression levels are inconsistent and understanding of its regulation is limited. Here we show ...that cell-cycle regulation underlies variable Ki-67 expression in all situations analyzed, including nontransformed human cells, normal mouse intestinal epithelia and adenomas, human cancer cell lines with or without drug treatments, and human breast and colon cancers. In normal cells, Ki-67 was a late marker of cell-cycle entry; Ki-67 mRNA oscillated with highest levels in G
while protein levels increased throughout the cell cycle, peaking in mitosis. Inhibition of CDK4/CDK6 revealed proteasome-mediated Ki-67 degradation in G
After cell-cycle exit, low-level Ki-67 expression persisted but was undetectable in fully quiescent differentiated cells or senescent cells. CDK4/CDK6 inhibition
and in tumors in mice caused G
cell-cycle arrest and eliminated Ki-67 mRNA in RB1-positive cells but had no effect in RB1-negative cells, which continued to proliferate and express Ki-67. Thus, Ki-67 expression varies due to cell-cycle regulation, but it remains a reliable readout for effects of CDK4/CDK6 inhibitors on cell proliferation.
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Microglial cells are integral to the pathogenesis of Alzheimer's disease (AD). The observed sex disparity in AD prevalence, with a notable predominance in women, implies a potential influence of sex ...hormones, such as androgens, on disease mechanisms. Despite this, the specific effects of androgens on microglia remain unclear. This study is designed to delineate the interplay between androgens and the survival and inflammatory profile of microglial cells, as well as to explore their contribution to the progression of AD.
To create a chronic androgen deficiency model, 3-month-old wild-type (WT) mice and APP/PS1 mice underwent bilateral orchiectomy (ORX), with age-matched sham-operated controls. Cognitive and memory were evaluated at 5 and 12 months, paralleled by assessments of amyloid-beta (Aβ) and microglial morphology in hippocampal and cortical areas. The ORX treatment in mice resulted in diminished microglial populations and morphological alterations, alongside an increase in Aβ plaques and a concomitant decline in cognitive performance that exacerbated over time. In vitro, dihydrotestosterone (DHT) was found to stimulate microglial proliferation and ameliorate Aβ1–42-induced apoptosis.
These findings suggested that androgens may exert a protective role, maintaining the normal proliferation and functionality of microglial cells. This preservation could potentially slow the progression of AD. As a result, our study provided a conceptual framework for the development of novel therapeutic strategies for AD.
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•Bilateral orchiectomy in mice leads to a significant decrease in the number of microglial cells in the brain.•Bilateral orchiectomy in mice exhibit an increase in amyloid-beta deposition.•The cognitive abilities of mice subjected to bilateral orchiectomy are markedly diminished.
Prostate cancer (PCa) is one of the most commonly diagnosed cancers in males worldwide. Circular RNA (circRNA) is a unique class of RNA transcribed by RNA polymerase II characterized by jointing 3′ ...and 5′ ends together via exon or intron circularization. However, the molecular functions of circRNAs in prostate cancer have rarely been explored. In present study, we found circ-SMARCA5 was up-regulated in prostate cancer samples compared to match normal tissues. We also observed circ-SMARCA5 expression was significantly induced after DHT treatment. Functional experiments showed circ-SMARCA5 acted as an oncogene in prostate cancer by promoting cell cycle and inhibiting cell apoptosis. We thought this study provided useful information for exploring circRNAs as potential therapeutic and prognostic targets for prostate cancer.
•To our knowledge, this is the first study to explore the molecular functions of circRNA in prostate cancer.•Our study showed that circ-SMARCA5 promoted cell proliferation and inhibited cell apoptosis in prostate cancer.•circ-SMARCA5 was for the first time reported as an androgen-responsive circRNA.•circ-SMARCA5 was for the first time reported to be up-regulated in prostate cancer.
Autophagy has been associated with oncogenesis with one of its emerging key functions being its contribution to the metabolism of tumors. Therefore, deciphering the mechanisms of how autophagy ...supports tumor cell metabolism is essential. Here, we demonstrate that the inhibition of autophagy induces an accumulation of lipid droplets (LD) due to a decrease in fatty acid β-oxidation, that leads to a reduction of oxidative phosphorylation (OxPHOS) in acute myeloid leukemia (AML), but not in normal cells. Thus, the autophagic process participates in lipid catabolism that supports OxPHOS in AML cells. Interestingly, the inhibition of OxPHOS leads to LD accumulation with the concomitant inhibition of autophagy. Mechanistically, we show that the disruption of mitochondria-endoplasmic reticulum (ER) contact sites (MERCs) phenocopies OxPHOS inhibition. Altogether, our data establish that mitochondria, through the regulation of MERCs, controls autophagy that, in turn finely tunes lipid degradation to fuel OxPHOS supporting proliferation and growth in leukemia.
Bone is one of the most common sites for metastasis across cancers. Cancer cells that travel through the vasculature and invade new tissues can remain in a non-proliferative dormant state for years ...before colonizing the metastatic site. Switching from dormancy to colonization is the rate-limiting step of bone metastasis. Here we develop an ex vivo co-culture method to grow cancer cells in mouse bones to assess cancer cell proliferation using healthy or cancer-primed bones. Profiling soluble factors from conditioned media identifies the chemokine CXCL5 as a candidate to induce metastatic colonization. Additional studies using CXCL5 recombinant protein suggest that CXCL5 is sufficient to promote breast cancer cell proliferation and colonization in bone, while inhibition of its receptor CXCR2 with an antagonist blocks proliferation of metastatic cancer cells. This study suggests that CXCL5 and CXCR2 inhibitors may have efficacy in treating metastatic bone tumors dependent on the CXCL5/CXCR2 axis.
The proteins extracellular signal-regulated kinase 1 (ERK1) and ERK2 are the downstream components of a phosphorelay pathway that conveys growth and mitogenic signals largely channelled by the small ...RAS GTPases. By phosphorylating widely diverse substrates, ERK proteins govern a variety of evolutionarily conserved cellular processes in metazoans, the dysregulation of which contributes to the cause of distinct human diseases. The mechanisms underlying the regulation of ERK1 and ERK2, their mode of action and their impact on the development and homeostasis of various organisms have been the focus of much attention for nearly three decades. In this Review, we discuss the current understanding of this important class of kinases. We begin with a brief overview of the structure, regulation, substrate recognition and subcellular localization of ERK1 and ERK2. We then systematically discuss how ERK signalling regulates six fundamental cellular processes in response to extracellular cues. These processes are cell proliferation, cell survival, cell growth, cell metabolism, cell migration and cell differentiation.
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