hCD2-iCre and Vav-iCre Mediated Gene Recombination Patterns in Murine Hematopoietic Cells

Cre-recombinase mediated conditional deletion of Lox-P site flanked ("floxed") genes is widely used for functional gene annotation in mice. Many different Cre-transgenic mouse lines have been developed for cell-type specific gene disruption. But often, the precise tissue-patterns of Cre activity remain incompletely characterized. Two widely used transgenes for conditional gene recombination in hematopoietic cells are Vav-iCre driven from the murine Vav1 promotor, and hCD2-iCre driven from the human CD2 promotor. Vav-iCre expresses active Cre in fetal and adult hematopoietic stem cells and all descendants, hCD2-iCre in immature and mature B and T lymphocytes. To better characterize which hematopoietic cells contain hCD2-iCre activity, we compared EYFP fluorescence in hCD2-iCre^+/- R26-stop-EYFP^+/- and Vav-iCre^+/- R26-stop-EYFP^+/-mice. R26-stop-EYFP ubiquitously encodes EYFP preceded by a floxed stop cassette. By removing it, Cre activity induces measurable EYFP expression. Our results confirm the known activity patterns for both Cre transgenes and unveil additional hCD2-iCre mediated reporter gene recombination in common lymphoid progenitors, in natural killer cells and their progenitors, and in plasmacytoid and conventional dendritic cells. This supports previously proposed common lymphoid origins for natural killer cells and subsets of dendritic cells, and indicates the need to consider pleiotropic effects when studying hCD2-iCre mediated conditional knockout mice. Vav-iCre^+/- R26-stop-EYFP^+/-mice did not show the non-hematopoietic recombination in vascular endothelial cells seen in other Vav-Cre mouse lines, but displayed an unexpected Vav-iCre mediated recombination in a bone cell subset lacking hematopoietic markers. This pinpoints the need to consider stromal cell contributions to phenotypes of Vav-iCre mediated conditional knockout mice. Altogether, our data provide the first detailed assessment of hCD2-iCre and Vav-iCre mediated deletion of floxed genes during lymphocyte development from hematopoietic stem cells and open up novel applications for either Cre-transgenic mouse line.     

PDGF-D contributes to neointimal hyperplasia in rat model of vessel injury

In this study, we determined the role of PDGF-D, a new member of the PDGF family, in a rat model of balloon injured artery made with a 2F catheter in Sprague-Dawley male rats. PDGF-D expression was studied in the injured and control segments of abdominal aorta. The function of PDGF-D was evaluated in rat vascular smooth muscle cells stably transfected with PDGF-D gene. We found that in normal abdominal aorta, PDGF-D was highly expressed in adventia, moderate in endothelia, and unidentified in media. Stable transfection of PDGF-D gene into vascular smooth muscle cells increased the cell migration by 2.2-fold, and the proliferation by 2.3-fold, respectively, and MMP-2 production and activity as well. These results support the fact that PDGF-D is involved in the formation of neointimal hyperplasia induced by balloon catheter injury and may serve as a target in preventing vascular restenosis after coronary angioplasty.     

Prox1 Inhibits Proliferation and Is Required for Differentiation of the Oligodendrocyte Cell Lineage in the Mouse

Central nervous system injury induces a regenerative response in ensheathing glial cells comprising cell proliferation, spontaneous axonal remyelination, and limited functional recovery, but the molecular mechanisms are not fully understood. In Drosophila, this involves the genes prospero and Notch controlling the balance between glial proliferation and differentiation, and manipulating their levels in glia can switch the response to injury from prevention to promotion of repair. In the mouse, Notch1 maintains NG2 oligodendrocyte progenitor cells (OPCs) in a progenitor state, but what factor may enable oligodendrocyte (OL) differentiation and functional remyelination is not understood. Here, we asked whether the mammalian homologue of prospero, Prox1, is involved. Our data show that Prox1 is distributed in NG2+ OPCs and in OLs in primary cultured cells, and in the mouse spinal cord in vivo. siRNA prox1 knockdown in primary OPCs increased cell proliferation, increased NG2+ OPC cell number and decreased CC1+ OL number. Prox1 conditional knockout in the OL cell lineage in mice increased NG2+ OPC cell number, and decreased CC1+ OL number. Lysolecithin-induced demyelination injury caused a reduction in CC1+ OLs in homozygous Prox1-/- conditional knockout mice compared to controls. Remarkably, Prox1-/- conditional knockout mice had smaller lesions than controls. Altogether, these data show that Prox1 is required to inhibit OPC proliferation and for OL differentiation, and could be a relevant component of the regenerative glial response. Therapeutic uses of glia and stem cells to promote regeneration and repair after central nervous system injury would benefit from manipulating Prox1.     

On the Role of Histamine Receptors in the Regulation of Circadian Rhythms

Several lines of evidence suggest a regulatory role of histamine in circadian rhythms, but little is known about signaling pathways that would be involved in such a putative role. The aim of this study was to examine whether histamine mediates its effects on the circadian system through Hrh1 or Hrh3 receptors. We assessed both diurnal and free-running locomotor activity rhythms of Hrh1 ^-/- and Hrh3 ^-/- mice. We also determined the expression of Per1, Per2 and Bmal1 genes in the suprachiasmatic nuclei, several areas of the cerebral cortex and striatum under symmetric 24 h light-dark cycle at zeitgeber times 14 and 6 by using radioactive in situ hybridization. We found no differences between Hrh1 ^-/- and wild type mice in the length, amplitude and mesor of diurnal and free-running activity rhythms as well as in expression of Per1, Per2 and Bmal1 genes in any of the examined brain structures. The amplitude of free-running activity rhythm of the Hrh3 ^-/- mice was significantly flattened, whereas the expression of the clock genes in Hrh3 ^-/- mice was similar to the wild type animals in all of the assessed brain structures. Therefore, the knockout of Hrh1 receptor had no effects on the circadian rhythm of spontaneous locomotion, and a knockout of Hrh3 receptor caused a substantial reduction of free-running activity rhythm amplitude, but none of these knockout models affected the expression patterns of the core clock genes in any of the studied brain structures.     

Sirtuin 3 is essential for hypertension‐induced cardiac fibrosis via mediating pericyte transition

Hypertension is the key factor for the development of cardiac fibrosis and diastolic dysfunction. Our previous study showed that knockout of sirtuin 3 (SIRT3) resulted in diastolic dysfunction in mice. In the present study, we explored the role of SIRT3 in angiotensin II (Ang‐II)–induced cardiac fibrosis and pericyte‐myofibroblast transition. NG2 tracing reporter NG2‐DsRed mouse was crossed with wild‐type (WT) mice and SIRT3KO mice. Cardiac function, cardiac fibrosis and reactive oxygen species (ROS) were measured. Mice infused with Ang‐II for 28 days showed a significant reduction of SIRT3 expression in the mouse hearts. Knockout of SIRT3 sensitized Ang‐II‐induced elevation of isovolumic relaxation time (IVRT) and reduction of ejection fraction (EF) and fractional shortening (FS). Ang‐II‐induced cardiac fibrosis, capillary rarefaction and hypertrophy were further enhanced by knockout of SIRT3. NG2 pericyte tracing reporter mice infused with Ang‐II had a significantly increased number of NG2‐DsRed pericyte in the heart. Knockout of SIRT3 further enhanced Ang‐II‐induced increase of pericytes. To examine pericyte‐myofibroblast/fibroblast transition, DsRed pericytes were co‐stained with FSP‐1 and α‐SMA. Ang‐II infusion led to a significant increase in numbers of DsRed⁺/FSP‐1⁺ and DsRed⁺/α‐SMA⁺ cells, while SIRT3KO further developed pericyte‐myofibroblast/fibroblast transition. In addition, knockout of SIRT3 promoted Ang‐II‐induced NADPH oxidase‐derived ROS formation together with increased expression of transforming growth factor beta 1 (TGF‐β1). We concluded that Ang‐II induced cardiac fibrosis partly by the mechanisms involving SIRT3‐mediated pericyte‐myofibroblast/fibroblast transition and ROS‐TGF‐β1 pathway.     

Split-Cre Complementation Indicates Coincident Activity of Different Genes In Vivo

Cre/LoxP recombination is the gold standard for conditional gene regulation in mice in vivo. However, promoters driving the expression of Cre recombinase are often active in a wide range of cell types and therefore unsuited to target more specific subsets of cells. To overcome this limitation, we designed inactive “split-Cre” fragments that regain Cre activity when overlapping co-expression is controlled by two different promoters. Using transgenic mice and virus-mediated expression of split-Cre, we show that efficient reporter gene activation is achieved in vivo. In the brain of transgenic mice, we genetically defined a subgroup of glial progenitor cells in which the Plp1- and the Gfap-promoter are simultaneously active, giving rise to both astrocytes and NG2-positive glia. Similarly, a subset of interneurons was labelled after viral transfection using Gad67- and Cck1 promoters to express split-Cre. Thus, split-Cre mediated genomic recombination constitutes a powerful spatial and temporal coincidence detector for in vivo targeting.     

A novel murine PDGF-D splicing variant results in significant differences in peptide expression and function

Platelet-derived growth factor (PDGF) is a potent mesenchymal cell mitogen and chemoattractant involved in the pathogenesis of fibroproliferative diseases. There are four known PDGF ligand isoforms designated A-D, two of which, C and D, were only recently discovered. We have identified a splicing variant in the PDGF-D isoform that occurs in mice, but not in humans. The presence of the splicing variant in murine PDGF-D appears to be due to an aberration in the splicing site at the junction of exons 5 and 6. The splicing variant results in a deletion predicted to have significant effects on peptide activity since it results in the deletion of bases within the cysteine knot domain that are important for peptide dimerization and receptor binding. It is important to appreciate differences between murine and human PDGF gene expression because PDGF is a key mitogen in the pathogenesis of fibrosis and mice are commonly employed as models for human disease.     

Hepatic Overexpression of Soluble Urokinase Receptor (uPAR) Suppresses Diet-Induced Atherosclerosis in Low-Density Lipoprotein Receptor-Deficient (LDLR-/-) Mice

Objective

Atherosclerosis, a chronic inflammatory disease, arises from metabolic disorders and is driven by inappropriate recruitment and proliferation of monocytes / macrophages and vascular smooth-muscle-cells. The receptor for the urokinase-type plasminogen activator (uPAR, Plaur) regulates the proteolytic activation of plasminogen. It is also a coactivator of integrins and facilitates leukocyte-endothelial interactions and vascular smooth-muscle-cell migration. The role of uPAR in atherogenesis remains elusive.

Methods and Results

We generated C57Bl6/J low-density lipoprotein receptor (LDL) and uPAR double knockout (uPAR^-/-/LDLR^-/-) mice to test the role of uPAR in two distinct atherosclerosis models. In LDLR^-/- mice, hepatic overexpression following hydrodynamic transfection of soluble uPAR that competes with endogenous membrane-bound uPAR was performed as an interventional strategy. Aortic root atherosclerotic lesions induced by feeding a high-fat diet were smaller and comprised less macrophages and vascular smooth-muscle-cells in double knockout mice and animals overexpressing soluble uPAR when compared to controls. In contrast, lesion size, lipid-, macrophage-, and vascular smooth muscle cell content of guide-wire-induced intima lesions in the carotid artery were not affected by uPAR deficiency. Adhesion of uPAR^-/--macrophages to TNFα-stimulated endothelial cells was decreased in vitro accompanied by reduced VCAM-1 expression on primary endothelial cells. Hepatic overexpression of soluble full-length murine uPAR in LDLR^-/- mice led to a reduction of diet-induced atherosclerotic lesion formation and monocyte recruitment into plaques. Ex vivo incubation with soluble uPAR protein also inhibited adhesion of macrophages to TNFα-stimulated endothelial cells in vitro.

Conclusion

uPAR-deficiency as well as competitive soluble uPAR reduced diet-promoted but not guide-wire induced atherosclerotic lesions in mice by preventing monocyte recruitment and vascular smooth-muscle-cell infiltration. Soluble uPAR may represent a therapeutic tool for the modulation of hyperlipidemia-associated atherosclerotic lesion formation.     

Platelet-derived growth factor receptors direct vascular development independent of vascular smooth muscle cell function

Complete loss of platelet-derived growth factor (PDGF) receptor signaling results in embryonic lethality around embryonic day 9.5, but the cause of this lethality has not been identified. Because cardiovascular failure often results in embryonic lethality at this time point, we hypothesized that a failure in cardiovascular development could be the cause. To assess the combined role of PDGF receptor α (PDGFRα) and PDGFRβ, we generated embryos that lacked these receptors in cardiomyocytes and vascular smooth muscle cells (VSMC) using conditional gene ablation. Deletion of either PDGFRα or PDGFRβ caused no overt vascular defects, but loss of both receptors using an SM22α-Cre transgenic mouse line led to a disruption in yolk sac blood vessel development. The cell population responsible for this vascular defect was the yolk sac mesothelial cells, not the cardiomyocytes or the VSMC. Coincident with loss of PDGF receptor signaling, we found a reduction in collagen deposition and an increase in MMP-2 activity. Finally, in vitro allantois cultures demonstrated a requirement for PDGF signaling in vessel growth. Together, these data demonstrate that PDGF receptors cooperate in the yolk sac mesothelium to direct blood vessel maturation and suggest that these effects are independent of their role in VSMC development.     

乙肝病毒X蛋白结合蛋白通过下调PEPCK的表达抑制肝脏糖异生

乙肝病毒X蛋白结合蛋白（hepatitis B X-interacting protein,HBXIP）可以调节乳腺癌中糖代谢重编程. 为了研究HBXIP在生理条件下对糖代谢的调节作用及机制,本研究利用Cre/loxP重组酶系统成功构建了肝脏组织中HBXIP特异敲除小鼠. 当小鼠接受刺激后,与正常组小鼠相比,肝脏HBXIP敲除小鼠表现基础糖代谢功能异常,如葡萄糖、丙酮酸;相对于对照小鼠,肝脏HBXIP敲除小鼠对糖异生和胰岛素耐受性减弱. RT-PCR、Western blot实验和免疫组化实验结果表明,HBXIP敲除小鼠肝脏组织中糖异生关键酶磷酸烯醇式丙酮酸羧化酶(phosphoenolpyruvate carboxykinase,PEPCK)表达显著增加. QRT-PCR 分析30例临床肝组织中HBXIP mRNA和PEPCK mRNA表达水平发现,HBXIP与PEPCK表达水平呈负相关. 荧光素酶报告基因实验和ChIP实验结果表明HBXIP可以在基因转录水平调节PEPCK表达. 以上结果表明,HBXIP通过调节糖异生关键酶PEPCK的表达参与调控小鼠肝脏糖异生.     

Clonal analysis for elucidating the lineage potential of embryonic NG2+ cells

Background aimsThe widespread NG2-expressing neural progenitors in the central nervous system (CNS) are considered to be multifunctional cells with lineage plasticity, thereby possessing the potential for treating CNS diseases. Their lineages and functional characteristics have not been completely unraveled. The present study aimed to disclose the lineage potential of clonal NG2⁺ populations in vitro and in vivo.MethodsTwenty-four clones from embryonic cerebral cortex-derived NG2⁺ cells were induced for oligodendrocyte, astrocyte, neuronal and chondrocyte differentiation. The expression profiles of neural progenitor markers chondroitin sulfate proteoglycan 4 (NG2), platelet-derived growth factor-α receptor (PDGFαR); nestin and neuronal cell surface antigen (A2B5) were subsequently sorted on cells with distinct differentiation capacity. Transplantation of these NG2⁺ clones into the spinal cord was used to examine their lineage potential in vivo.ResultsIn vitro differentiation analysis revealed that all the clones could differentiate into oligodendrocytes, and seven of them were bipotent (oligodendrocytes and astrocytes). Amazingly, one clone exhibited a multipotent capacity of differentiating into not only neuronal–glial lineages but also chondrocytes. These distinct subtypes were further found to exhibit phenotypic heterogeneity based on the examination of a spectrum of neural progenitor markers. Transplanted clones survived, migrated extensively and differentiated into oligodendrocytes, astrocytes or even neurons to integrate with the host spinal cord environmentConclusionsThese results suggest that NG2⁺ cells contain heterogeneous progenitors with distinct differentiation capacities, and the immortalized clonal NG2⁺ cell lines might provide a cell source for treating spinal cord disorders.     

TET1s deficiency exacerbates oscillatory shear flow-induced atherosclerosis

Background: TET1 has been implicated in regulating inflammation and cardiovascular disease, but a newly discovered short isoform of TET1 (termed TET1s) exhibits higher expression in adult tissues than full-length TET1. However, the precise role of TET1 in cardiovascular disease remains undefined.Methods and Results: Based on TET1^-/- knockout mice (with deletion of both TET1 and TET1s ) and TET1^cs/cs mice (with deletion of only TET1), we found that TET1s deletion in TET1^-/- mice resulted in more serious atherosclerotic lesions in the whole aorta than TET1cs/cs in the ApoE^-/- background mice fed a high-fat diet. Atherosclerotic lesions with Oil red staining were dramatically localized in the aortic arch, abdominal aorta and ligated LCA, where they were exposed to OSS. Furthermore, the OSS-induced depression of TET1s in vitro and in vivo increased inflammatory cell and red blood cell infiltration into the subendothelial layer by impairing the vascular intimal barrier. TET1s upregulation enhanced vascular endothelial barrier function by increasing gap protein connexin 40 (CX40) expression as measured by RNA-seq and was confirmed by CX40 knockdown. TET1s interaction with Sin3a increased the global and CX40 promoter histone H3K27 acetylation levels, but not DNA methylation, to induce CX40 expression.Conclusions: These data demonstrate the unexpected discovery that laminar shear stress induces TET1s expression to protect the vascular endothelial barrier by increasing CX40 expression in ECs and that TET1s overexpression may be the core step for OSS-induced atherosclerosis therapy.     

PDZK1 Prevents Neointima Formation via Suppression of Breakpoint Cluster Region Kinase in Vascular Smooth Muscle

Scavenger receptor class B, type I (SR-BI) and its adaptor protein PDZK1 mediate responses to HDL cholesterol in endothelium. Whether the receptor-adaptor protein tandem serves functions in other vascular cell types is unknown. The current work determined the roles of SR-BI and PDZK1 in vascular smooth muscle (VSM). To evaluate possible VSM functions of SR-BI and PDZK1 in vivo, neointima formation was assessed 21 days post-ligation in the carotid arteries of wild-type, SR-BI^-/- or PDZK1^-/- mice. Whereas neointima development was negligible in wild-type and SR-BI^-/-, there was marked neointima formation in PDZK1^-/- mice. PDZK1 expression was demonstrated in primary mouse VSM cells, and compared to wild-type cells, PDZK1^-/- VSM displayed exaggerated proliferation and migration in response to platelet derived growth factor (PDGF). Tandem affinity purification-mass spectrometry revealed that PDZK1 interacts with breakpoint cluster region kinase (Bcr), which contains a C-terminal PDZ binding sequence and is known to enhance responses to PDGF in VSM. PDZK1 interaction with Bcr in VSM was demonstrated by pull-down and by coimmunoprecipitation, and the augmented proliferative response to PDGF in PDZK1^-/- VSM was abrogated by Bcr depletion. Furthermore, compared with wild-type Bcr overexpression, the introduction of a Bcr mutant incapable of PDZK1 binding into VSM cells yielded an exaggerated proliferative response to PDGF. Thus, PDZK1 has novel SR-BI-independent function in VSM that affords protection from neointima formation, and this involves PDZK1 suppression of VSM cell proliferation via an inhibitory interaction with Bcr.     

Transduction of the rat brain by Bovine Herpesvirus 4

The purpose of this study was to assess the behavior of pseudotyped recombinant adeno-associated virus type 1 (rAAV2/1) vector genomes in dystrophic skeletal muscle. A comparison was made between a therapeutic vector and a reporter vector by injecting the hindlimb in a mouse model of Limb Girdle Muscular Dystrophy Type 2D (LGMD-2D) prior to disease onset. We hypothesized that the therapeutic vector would establish long-term persistence through prevention of myofiber turnover. In contrast, the reporter vector genome copy number would diminish over time due to disease-associated muscle degradation. One day old alpha sarcoglycan knockout mice (sgca ^-/-) were injected with 1 × 10¹¹ vector genomes of rAAV2/1-tMCK-sgca in one hindlimb and the same dose of rAAV2/1-tMCK-LacZ in the contra lateral hindlimb. Newborn mice are tolerant of the foreign transgene allowing for long-term expression of both the marker and the therapeutic gene in the null background. At 2 time-points following vector administration, hindlimb muscles were harvested and analyzed for LacZ or sarcoglycan expression. Our data demonstrate prolonged vector genome persistence in skeletal muscle from the hindlimbs injected with the therapeutic transgene as compared to hindlimbs injected with the reporter gene. We observed loss of vector genomes in skeletal muscles that were there were not protected by the benefits of therapeutic gene transfer. In comparison, the therapeutic vector expressing sarcoglycan led to reduction or elimination of myofiber loss. Mitigating the membrane instability inherent in dystrophic muscle was able to prolong the life of individual myofibers.     

microRNA let‐7g suppresses PDGF‐induced conversion of vascular smooth muscle cell into the synthetic phenotype

Platelet‐derived growth factor (PDGF) can promote vascular smooth muscle cells (VSMCs) to switch from the quiescent contractile phenotype to synthetic phenotype, which contributes to atherosclerosis. We aimed to investigate the role of microRNA let‐7g in phenotypic switching. Bioinformatics prediction was used to find let‐7g target genes in the PDGF/mitogen‐activated protein kinase kinase kinase 1 (MEKK1)/extracellular signal‐regulated kinase (ERK)/Krüppel‐like factor‐4 (KLF4) signalling pathway that affects VSMC phenotypic switching. The luciferase reporter assay and let‐7g transfection were used to confirm let‐7g target genes. Two contractile proteins alpha‐smooth muscle actin (α‐SMA) and calponin were VSMC‐specific genes and were measured as the indicators for VSMC phenotype. Lentivirus carrying the let‐7g gene was injected to apolipoprotein E knockout (apoE^?/?) mice to confirm let‐7g's effect on preventing atherosclerosis. Through the PDGF/MEKK1/ERK/KLF4 signalling pathway, PDGF‐BB can inhibit α‐SMA and calponin. The PDGFB and MEKK1 genes were predicted to harbour let‐7g binding sites, which were confirmed by our reporter assays. Transfection of let‐7g to VSMC also reduced PDGFB and MEKK1 levels. Moreover, we showed that let‐7g decreased phosphorylated‐ERK1/2 while had no effect on total ERK1/2. KLF4 can reduce VSMC‐specific gene expression by preventing myocardin–serum response factor (SRF) complex from associating with these gene promoters. The immunoprecipitation assay showed that let‐7g decreased the interaction between KLF4 and SRF. Further experiments demonstrated that let‐7g can increase α‐SMA and calponin levels to maintain VSMC in the contractile status. Injection of lentivirus carrying let‐7g gene increased let‐7g's levels in aorta and significantly decreased atherosclerotic plaques in the apoE^?/? mice. We demonstrated that let‐7g reduces the PDGF/MEKK1/ERK/KLF4 signalling to maintain VSMC in the contractile status, which further reduce VSMC atherosclerotic change.     

VEGFR1-Positive Macrophages Facilitate Liver Repair and Sinusoidal Reconstruction after Hepatic Ischemia/Reperfusion Injury

Liver repair after acute liver injury is characterized by hepatocyte proliferation, removal of necrotic tissue, and restoration of hepatocellular and hepatic microvascular architecture. Macrophage recruitment is essential for liver tissue repair and recovery from injury; however, the underlying mechanisms are unclear. Signaling through vascular endothelial growth factor receptor 1 (VEGFR1) is suggested to play a role in macrophage migration and angiogenesis. The aim of the present study was to examine the role of VEGFR1 in liver repair and sinusoidal reconstruction after hepatic ischemia/reperfusion (I/R). VEGFR1 tyrosine kinase knockout mice (VEGFR1 TK^-/- mice) and wild-type (WT) mice were subjected to hepatic warm I/R, and the processes of liver repair and sinusoidal reconstruction were examined. Compared with WT mice, VEGFR1 TK^-/- mice exhibited delayed liver repair after hepatic I/R. VEGFR1-expressing macrophages recruited to the injured liver showed reduced expression of epidermal growth factor (EGF). VEGFR1 TK^-/- mice also showed evidence of sustained sinusoidal functional and structural damage, and reduced expression of pro-angiogenic factors. Treatment of VEGFR1 TK^-/- mice with EGF attenuated hepatoceullar and sinusoidal injury during hepatic I/R. VEGFR1 TK^-/- bone marrow (BM) chimeric mice showed impaired liver repair and sinusoidal reconstruction, and reduced recruitment of VEGFR1-expressing macrophages to the injured liver. VEGFR1-macrophages recruited to the liver during hepatic I/R contribute to liver repair and sinusoidal reconstruction. VEGFR1 activation is a potential therapeutic strategy for promoting liver repair and sinusoidal restoration after acute liver injury.     

Reduction in Tcf7l2 expression decreases diabetic susceptibility in mice

Objective: The WNT signaling pathway effector gene TCF7L2 has been associated with an increased risk of type 2 diabetes. However, it remains unclear how this gene affects diabetic pathogenesis. The goal of this study was to investigate the effects of Tcf7l2 haploinsufficiency on metabolic phenotypes in mice.Experimental Design: Tcf7l2 knockout (Tcf7l^-/-) mice were generated. Because of the early mortality of Tcf7l2^-/- mice, we characterized the metabolic phenotypes of heterozygous Tcf7l2^+/- mice in comparison to the wild-type controls. The mice were fed a normal chow diet or a high fat diet (HFD) for 9 weeks.Results: The Tcf7l2^+/- mice showed significant differences from the wild-type mice with regards to body weight, fasting glucose and insulin levels. Tcf7l2^+/- mice displayed improved glucose tolerance. In the liver of Tcf7l2^+/- mice fed on the HFD, reduced lipogenesis and hepatic triglyceride levels were observed when compared with those of wild-type mice. Furthermore, the Tcf7l2^+/- mice fed on the HFD exhibited decreased peripheral fat deposition. Immunohistochemistry in mouse pancreatic islets showed that endogenous expression of Tcf7l2 was upregulated in the wild-type mice, but not in the Tcf7l2^+/- mice, after feeding with the HFD. However, the haploinsufficiency of Tcf7l2 in mouse pancreatic islets resulted in little changes in glucose-stimulated insulin secretion.Conclusion: These results suggest that decreased expression of Tcf7l2 confers reduction of diabetic susceptibility in mice via regulation on the metabolism of glucose and lipid.     

Haptoglobin and malaria

Abstract

Haptoglobin gene knockout mice and wild-type controls were infected with Plasmodium berghei ANKA or Plasmodium chabaudi. The peak parasitaemia and parasite burden were higher in Hp^-/- mice than in Hp^+/+ mice. The increase in spleen weight following malaria infection was smaller in Hp^-/- mice than in Hp^+/+ animals. The occurrence of cerebral malaria in P. berghei ANKA infection was not different in Hp gene knockout mice and their controls.