Project description:We perform RNAseq in NAFLD livers from WT and miR-33-AlbCRE conditional knock-out mice. Liver were isolated from mice after 3 months of feeding a choline deficient high fat diet to analyze the effect of miR-33 deficiency.
Project description:We perform sc-RNAseq in NASH livers from WT and miR-33-AlbCRE conditional knock-out mice. Liver were isolated from mice after 6 months of feeding a choline deficient high fat diet to analyze the effect of miR-33 deficiency specifically in hepatocytes and the crosstalk between hepatocytes and other cell types in the liver.
Project description:miR-33 is an intronic microRNA within the gene encoding the SREBP2 transcription factor. Like its host gene, miR-33 has been shown to be an important regulator of lipid metabolism. Inhibition of miR-33 has been shown to promote cholesterol efflux in macrophages by targeting the cholesterol transporter ABCA1, thus reducing atherosclerotic plaque burden. Inhibition of miR-33 has also been shown to improve high-density lipoprotein (HDL) biogenesis in the liver and increase circulating HDL-C levels in both rodents and nonhuman primates. However, evaluating the extent to which these changes in HDL metabolism contribute to atherogenesis has been hindered by the obesity and metabolic dysfunction observed in whole-body miR-33–knockout mice. To determine the impact of hepatic miR-33 deficiency on obesity, metabolic function, and atherosclerosis, we have generated a conditional knockout mouse model that lacks miR-33 only in the liver. Characterization of this model demonstrates that loss of miR-33 in the liver does not lead to increased body weight or adiposity. Hepatic miR-33 deficiency actually improves regulation of glucose homeostasis and impedes the development of fibrosis and inflammation. We further demonstrate that hepatic miR-33 deficiency increases circulating HDL-C levels and reverse cholesterol transport capacity in mice fed a chow diet, but these changes are not sufficient to reduce atherosclerotic plaque size under hyperlipidemic conditions. By elucidating the role of miR-33 in the liver and the impact of hepatic miR-33 deficiency on obesity and atherosclerosis, this work will help inform ongoing efforts to develop novel targeted therapies against cardiometabolic diseases.
Project description:Mouse peritoneal macrophages were transfected with 80-120 nM miRIDIAN miRNA mimics (miR-mimic-33/miR-mimic-33*) or with 80-120 nM miRIDIAN miRNA inhibitors (anti-miR-33 ASO/anti-miR-33*ASO) Control samples were treated with an equal concentration of a non-targeting control mimics sequence (control mimic) or inhibitor negative control sequence (control aso), to control for non-specific effects in miRNA experiments.
Project description:We used single cell RNA-sequencing of aortic CD45+ cells, combined with immunohistologic, morphometric and flow cytometric analyses to define the changes in plaque immune cell composition, gene expression and function following miR-33 inhibition. We report that anti-miR-33 treatment of Ldlr–/– mice with advanced atherosclerosis reduced plaque burden and altered the plaque immune cell landscape by shifting the balance of pro- and anti-atherosclerotic macrophage and T cell subsets. By quantifying the kinetic processes that determine plaque macrophage burden, we found that anti-miR-33 reduced levels of circulating monocytes and splenic myeloid progenitors, decreased macrophage proliferation and retention, and promoted macrophage attrition by apoptosis and efferocytotic clearance. scRNA-sequencing of aortic arch plaques showed that anti-miR-33 reduced the frequency of MHCIIhi “inflammatory” and Trem2hi “metabolic” macrophages, but not tissue resident macrophages. Furthermore, anti-miR-33 led to derepression of distinct miR-33 target genes in the different macrophage subsets: in resident and Trem2hi macrophages, anti-miR-33 relieved repression of miR-33 target genes involved in lipid metabolism (e.g., Abca1, Ncoa1, Ncoa2, Crot), whereas in MHCIIhi macrophages, anti-miR-33 upregulated target genes involved in chromatin remodeling and transcriptional regulation. Anti-miR-33 also reduced the accumulation of aortic CD8+ and CD4+ Th1 cells, and increased levels of FoxP3+ regulatory T cells in plaques, consistent with an immune-dampening effect on plaque inflammation.
Project description:Background: Senescent hepatocytes accumulate in parallel with fibrosis progression during NASH. The mechanisms that enable progressive expansion of nonreplicating cell populations and the significance of that process in determining NASH outcomes are unclear. Many types of senescing cells upregulate the THBD-PAR-1 signaling axis to remain viable. Vorapaxar, an FDA-approved PAR-1 inhibitor, blocks the activity of that pathway. We used vorapaxar to determine if and how THBD-PAR1 signaling promotes fibrosis progression in NASH. Methods: We evaluated the THBD-PAR1 pathway in liver biopsies from NAFLD patient cohorts with a spectrum of liver fibrosis. Chow fed mice were treated with viral vectors to over-express p16 specifically in hepatocytes and induce replicative senescence. Effects on the THBD-PAR-1 axis and regenerative capacity were assessed; the transcriptome of p16 over-expressing hepatocytes was characterized and we examined how conditioned medium from senescent but viable (dubbed ‘undead’) hepatocytes reprograms hepatic stellate cells. A genetically obese mouse model of NASH with little liver fibrosis, and a diet-induced mouse model of NASH with advanced fibrosis were treated with vorapaxar to determine effects on hepatocyte senescence and liver damage. Results: Inducing senescence up-regulates the THBD-PAR1 signaling axis in hepatocytes and induces their expression of fibrogenic factors, including hedgehog ligands. Hepatocyte THBD-PAR1 signaling increases in NAFLD and supports sustained hepatocyte senescence that limits effective liver regeneration and promotes maladaptive repair. Inhibiting PAR-1 signaling with vorapaxar interrupts this process, reduces the burden of ‘undead’ senescent cells, and safely improves NASH and fibrosis despite ongoing lipotoxic stress Conclusion: The THBD-PAR1 signaling axis is a novel therapeutic target for NASH because blocking this pathway prevents accumulation of senescing but viable hepatocytes that generate factors that promote maladaptive liver repair.
Project description:miR-33 is an intronic miRNA within the gene encoding the SREBP2 transcription factor. Like its host gene, miR-33 has been shown to be an important regulator of lipid metabolism. Inhibition of miR-33 has been shown to promote cholesterol efflux in macrophages by targeting the cholesterol transporter ABCA1, thus reducing atherosclerotic plaque burden. Inhibition of miR-33 has also been shown to improve HDL biogenesis in the liver and increase circulating HDL-C levels in both rodents and non-human primates. However, evaluating the extent to which these changes in HDL metabolism contribute to atherogenesis has been hindered by the obesity and metabolic dysfunction observed in whole body miR-33 knockout mice. To determine the impact of hepatic miR-33 deficiency on obesity, metabolic function and atherosclerosis, we have generated a conditional knockout mouse model that lacks miR-33 only in the liver. Characterization of this model demonstrates that loss of miR-33 in the liver does not lead to increased body weight or adiposity. Hepatic miR-33 deficiency actually improves regulation of glucose homeostasis and impedes the development of fibrosis and inflammation. We further demonstrate that hepatic miR-33 deficiency increases circulating HDL-C levels and reverse cholesterol transport capacity in mice fed a chow diet, but these changes are not sufficient to reduce atherosclerotic plaque size under hyperlipidemic conditions. By elucidating the role of miR-33 in the liver, and the impact of hepatic miR-33 deficiency on obesity and atherosclerosis, this work will help inform ongoing efforts to develop novel targeted therapies against cardio-metabolic diseases.