Mir-34a is upregulated during liver regeneration in rats and is associated with the suppression of hepatocyte proliferation

Background

MicroRNAs are a class of small regulatory RNAs that modulate a variety of biological processes, including cellular differentiation, apoptosis, metabolism and proliferation. This study aims to explore the effect of miR-34a in hepatocyte proliferation and its potential role in liver regeneration termination.

Methodology/Principal Finding

MiR-34a was highly induced after partial hepatectomy. Overexpression of miR-34a in BRL-3A cells could significantly inhibit cell proliferation and down-regulate the expression of inhibin βB (INHBB) and Met. In BRL-3A cells, INHBB was identified as a direct target of miR-34a by luciferase reporter assay. More importantly, INHBB siRNA significantly repressed cell proliferation. A decrease of INHBB and Met was detected in regenerating liver.

Conclusion/Significance

MiR-34a expression was upregulated during the late phase of liver regeneration. MiR-34a-mediated regulation of INHBB and Met may collectively contribute to the suppression of hepatocyte proliferation.     

The Bryopsis hypnoides plastid genome: multimeric forms and complete nucleotide sequence

Background

Bryopsis hypnoides Lamouroux is a siphonous green alga, and its extruded protoplasm can aggregate spontaneously in seawater and develop into mature individuals. The chloroplast of B. hypnoides is the biggest organelle in the cell and shows strong autonomy. To better understand this organelle, we sequenced and analyzed the chloroplast genome of this green alga.

Principal Findings

A total of 111 functional genes, including 69 potential protein-coding genes, 5 ribosomal RNA genes, and 37 tRNA genes were identified. The genome size (153,429 bp), arrangement, and inverted-repeat (IR)-lacking structure of the B. hypnoides chloroplast DNA (cpDNA) closely resembles that of Chlorella vulgaris. Furthermore, our cytogenomic investigations using pulsed-field gel electrophoresis (PFGE) and southern blotting methods showed that the B. hypnoides cpDNA had multimeric forms, including monomer, dimer, trimer, tetramer, and even higher multimers, which is similar to the higher order organization observed previously for higher plant cpDNA. The relative amounts of the four multimeric cpDNA forms were estimated to be about 1, 1/2, 1/4, and 1/8 based on molecular hybridization analysis. Phylogenetic analyses based on a concatenated alignment of chloroplast protein sequences suggested that B. hypnoides is sister to all Chlorophyceae and this placement received moderate support.

Conclusion

All of the results suggest that the autonomy of the chloroplasts of B. hypnoides has little to do with the size and gene content of the cpDNA, and the IR-lacking structure of the chloroplasts indirectly demonstrated that the multimeric molecules might result from the random cleavage and fusion of replication intermediates instead of recombinational events.     

Imaging long-term fate of intramyocardially implanted mesenchymal stem cells in a porcine myocardial infarction model

The long-term fate of stem cells after intramyocardial delivery is unknown. We used noninvasive, repetitive PET/CT imaging with [(18)F]FEAU to monitor the long-term (up to 5 months) spatial-temporal dynamics of MSCs retrovirally transduced with the sr39HSV1-tk gene (sr39HSV1-tk-MSC) and implanted intramyocardially in pigs with induced acute myocardial infarction. Repetitive [(18)F]FEAU PET/CT revealed a biphasic pattern of sr39HSV1-tk-MSC dynamics; cell proliferation peaked at 33-35 days after injection, in periinfarct regions and the major cardiac lymphatic vessels and lymph nodes. The sr39HSV1-tk-MSC-associated [(18)F]FEAU signals gradually decreased thereafter. Cardiac lymphography studies using PG-Gd-NIRF813 contrast for MRI and near-infrared fluorescence imaging showed rapid clearance of the contrast from the site of intramyocardial injection through the subepicardial lymphatic network into the lymphatic vessels and periaortic lymph nodes. Immunohistochemical analysis of cardiac tissue obtained at 35 and 150 days demonstrated several types of sr39HSV1-tk expressing cells, including fibro-myoblasts, lymphovascular cells, and microvascular and arterial endothelium. In summary, this study demonstrated the feasibility and sensitivity of [(18)F]FEAU PET/CT imaging for long-term, in-vivo monitoring (up to 5 months) of the fate of intramyocardially injected sr39HSV1-tk-MSC cells. Intramyocardially transplanted MSCs appear to integrate into the lymphatic endothelium and may help improve myocardial lymphatic system function after MI.     

Hydrogen sulfide attenuates carbon tetrachloride-induced hepatotoxicity, liver cirrhosis and portal hypertension in rats

Background

Hydrogen sulfide (H₂S) displays vasodilative, anti-oxidative, anti-inflammatory and cytoprotective activities. Impaired production of H₂S contributes to the increased intrahepatic resistance in cirrhotic livers. The study aimed to investigate the roles of H₂S in carbon tetrachloride (CCl₄)-induced hepatotoxicity, cirrhosis and portal hypertension.

Methods and Findings

Sodium hydrosulfide (NaHS), a donor of H₂S, and DL-propargylglycine (PAG), an irreversible inhibitor of cystathionine γ-lyase (CSE), were applied to the rats to investigate the effects of H₂S on CCl₄-induced acute hepatotoxicity, cirrhosis and portal hypertension by measuring serum levels of H₂S, hepatic H₂S producing activity and CSE expression, liver function, activity of cytochrome P450 (CYP) 2E1, oxidative and inflammatory parameters, liver fibrosis and portal pressure. CCl₄ significantly reduced serum levels of H₂S, hepatic H₂S production and CSE expression. NaHS attenuated CCl₄-induced acute hepatotoxicity by supplementing exogenous H₂S, which displayed anti-oxidative activities and inhibited the CYP2E1 activity. NaHS protected liver function, attenuated liver fibrosis, inhibited inflammation, and reduced the portal pressure, evidenced by the alterations of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hyaluronic acid (HA), albumin, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and soluble intercellular adhesion molecule (ICAM)-1, liver histology, hepatic hydroxyproline content and α-smooth muscle actin (SMA) expression. PAG showed opposing effects to NaHS on most of the above parameters.

Conclusions

Exogenous H₂S attenuates CCl₄-induced hepatotoxicity, liver cirrhosis and portal hypertension by its multiple functions including anti-oxidation, anti-inflammation, cytoprotection and anti-fibrosis, indicating that targeting H₂S may present a promising approach, particularly for its prophylactic effects, against liver cirrhosis and portal hypertension.     

Developmental localization and methylesterification of pectin epitopes during somatic embryogenesis of banana (Musa spp. AAA)

Background

The plant cell walls play an important role in somatic embryogenesis and plant development. Pectins are major chemical components of primary cell walls while homogalacturonan (HG) is the most abundant pectin polysaccharide. Developmental regulation of HG methyl-esterification degree is important for cell adhesion, division and expansion, and in general for proper organ and plant development.

Methodology/Principal Findings

Developmental localization of pectic homogalacturonan (HG) epitopes and the (1→4)-β-D-galactan epitope of rhamnogalacturonan I (RG-I) and degree of pectin methyl-esterification (DM) were studied during somatic embryogenesis of banana (Musa spp. AAA). Histological analysis documented all major developmental stages including embryogenic cells (ECs), pre-globular, globular, pear-shaped and cotyledonary somatic embryos. Histochemical staining of extracellularly secreted pectins with ruthenium red showed the most intense staining at the surface of pre-globular, globular and pear-shaped somatic embryos. Biochemical analysis revealed developmental regulation of galacturonic acid content and DM in diverse embryogenic stages. Immunodots and immunolabeling on tissue sections revealed developmental regulation of highly methyl-esterified HG epitopes recognized by JIM7 and LM20 antibodies during somatic embryogenesis. Cell walls of pre-globular/globular and late-stage embryos contained both low methyl-esterified HG epitopes as well as partially and highly methyl-esterified ones. Extracellular matrix which covered surface of early developing embryos contained pectin epitopes recognized by 2F4, LM18, JIM5, JIM7 and LM5 antibodies. De-esterification of cell wall pectins by NaOH caused a decrease or an elimination of immunolabeling in the case of highly methyl-esterified HG epitopes. However, immunolabeling of some low methyl-esterified epitopes appeared stronger after this base treatment.

Conclusions/Significance

These data suggest that both low- and highly-methyl-esterified HG epitopes are developmentally regulated in diverse embryogenic stages during somatic embryogenesis. This study provides new information about pectin composition, HG methyl-esterification and developmental localization of pectin epitopes during somatic embryogenesis of banana.     

Mth10b, a unique member of the Sac10b family, does not bind nucleic acid

The Sac10b protein family is regarded as a group of nucleic acid-binding proteins that are highly conserved and widely distributed within archaea. All reported members of this family are basic proteins that exist as homodimers in solution and bind to DNA and/or RNA without apparent sequence specificity in vitro. Here, we reported a unique member of the family, Mth10b from Methanobacterium thermoautotrophicum ΔH, whose amino acid sequence shares high homology with other Sac10b family proteins. However, unlike those proteins, Mth10b is an acidic protein; its potential isoelectric point is only 4.56, which is inconsistent with the characteristics of a nucleic acid-binding protein. In this study, Mth10b was expressed in Escherichia coli and purified using a three-column chromatography purification procedure. Biochemical characterization indicated that Mth10b should be similar to typical Sac10b family proteins with respect to its secondary and tertiary structure and in its preferred oligomeric forms. However, an electrophoretic mobility shift analysis (EMSA) showed that neither DNA nor RNA bound to Mth10b in vitro, indicating that either Mth10b likely has a physiological function that is distinct from those of other Sac10b family members or nucleic acid-binding ability may not be a fundamental factor to the actual function of the Sac10b family.     

The histone demethylases Jhdm1a/1b enhance somatic cell reprogramming in a vitamin-C-dependent manner

Reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) resets the epigenome to an embryonic-like state. Vitamin C enhances the reprogramming process, but the underlying mechanisms are unclear. Here we show that the histone demethylases Jhdm1a/1b are key effectors of somatic cell reprogramming downstream of vitamin C. We first observed that vitamin C induces H3K36me2/3 demethylation in mouse embryonic fibroblasts in culture and during reprogramming. We then identified Jhdm1a/1b, two known vitamin-C-dependent H3K36 demethylases, as potent regulators of reprogramming through gain- and loss-of-function approaches. Furthermore, we found that Jhdm1b accelerates cell cycle progression and suppresses cell senescence during reprogramming by repressing the Ink4/Arf locus. Jhdm1b also cooperates with Oct4 to activate the microRNA cluster 302/367, an integral component of the pluripotency machinery. Our results therefore reveal a role for H3K36me2/3 in cell fate determination and establish a link between histone demethylases and vitamin-C-induced reprogramming.     

On Polydispersity of Plant Biomass Recalcitrance and Its Effects on Pretreatment Optimization for Sugar Production

This paper discusses a property associated with plant biomass recalcitrance to enzyme and microbial deconstructions in sugar production from cellulose and hemicelluloses. The hemicelluloses are more readily hydrolyzed to sugars than is cellulose. As a result, optimization to maximize individual glucose and hemicellulose sugar recovery is not possible. This property is an inherent feature of plant biomass and is named polydispersity of plant biomass recalcitrance (PPBR) in this study. A set of pretreatment experiments using eucalyptus and sulfite pretreatment to overcome recalcitrance of lignocelluloses was conducted. The results were used to predict the conditions for individually maximizing enzymatic glucose and xylose yields. The predicted maximal yields were used to quantitatively illustrate the PPBR concept. The effect of PPBR on pretreatment optimization and strategies for maximal sugar recovery using two-stage pretreatment are discussed.     

Genetic characteristics of 2009 pandemic H1N1 influenza a viruses isolated from Mainland China

A total of 100 HIN1 flu real-time-PCR positive throat swabs collected from fever patients in Zhejiang,Hubei and Guangdong between June and November 2009,were provided by local CDC laboratories.After MDCK cell culture,57 Influenza A Pandemic (H1N1) viruses were isolated and submitted for whole genome sequencing.A total of 39 HA sequences,52 NA sequences,36 PB2 sequences,31 PB1 sequences,40 PA sequences,48 NP sequences,51 MP sequences and 36 NS sequences were obtained,including 20 whole genome sequences.Sequence comparison revealed they shared a high degree of homology (96％～99％) with known epidemic strains (A/Califomia/04/2009(H1N1).Phylogenetic analysis showed that although the sequences were highly conserved,they clustered into a small number of groups with only a few distinct strains.Site analysis revealed three substitutions at loop 220 (221-228) of the HA receptor binding site in the 39 HA sequences:A/Hubei/86/2009 PKVRDQEG→PKVRDQEA,A/Zhejiang/08/2009 PKVRDQEG→PKVRDQER,A/Hubei/75/2009PKVRDQEG→PKVRDQGG,the A/Hubei/75/2009 was isolated from an acute case,while the other two were from patients with mild symptoms.Other key sites such as 119,274,292 and 294 amino acids of NA protein,627 of PB2 protein were conserved.Meanwhile,all the M2 protein sequences possessed the Ser32Asn mutation,suggesting that these viruses were resistant to adamantanes.Comparison of these sequences with other H1N1 viruses collected from the NCBI database provides insight into H1N1 transmission and circulation patterns.