Avolio et al. show that cardiac pericytes have intrinsic vascular plasticity and can be pharmacologically reprogrammed using a MEK inhibitor to aid neovascularization of the ischemic heart. The cover image shows cardiomyocytes stained with α-sarcomeric actin (red) and TUNEL (green; recognizing apoptotic cell nuclei) from a mouse heart treated with a MEK inhibitor.
Acute megakaryoblastic leukemia of Down syndrome (DS-AMKL) is a model of clonal evolution from a preleukemic transient myeloproliferative disorder requiring both a trisomy 21 (T21) and a GATA1s mutation to a leukemia driven by additional driver mutations. We modelled the megakaryocyte differentiation defect through stepwise gene editing of GATA1s, SMC3+/- and MPLW515K providing 20 different trisomy or disomy 21 iPSC clones. GATA1s profoundly reshaped iPSC-derived hematopoietic architecture with gradual myeloid-to-megakaryocyte shift and megakaryocyte differentiation alteration upon addition of SMC3 and MPL mutations. Transcriptional, chromatin accessibility and GATA1 binding data showed alteration of essential megakaryocyte differentiation genes, including NFE2 downregulation that was associated with loss of GATA1s binding and functionally-involved in megakaryocyte differentiation blockage. T21 enhanced the proliferative phenotype reproducing the cellular and molecular abnormalities of DS-AMKL. Our study provides a unique array of human cell-based models revealing individual contributions of different mutations to DS-AMKL differentiation blockage, a major determinant of leukemic progression.
Brahim Arkoun, Elie Robert, Fabien Boudia, Stefania Mazzi, Virginie Dufour, Aurelie Siret, Yasmine Mammasse, Zakia Aid, Mathieu Vieira, Aygun Imanci, Marine Aglave, Marie Cambot, Rachel Petermann, Sylvie Souquere, Philippe Rameau, Cyril Catelain, Romain Diot, Gerard Tachdjian, Olivier Hermine, Nathalie Droin, Najet Debili, Isabelle Plo, Sebastien Malinge, Eric Soler, Hana Raslova, Thomas Mercher, William Vainchenker
Elevated hematocrit is associated with cardiovascular risk; however, the causality and mechanisms are unclear. The JAK2V617F (Jak2VF) mutation increases cardiovascular risk in myeloproliferative disorders and in clonal hematopoiesis (CH). Jak2VF mice with elevated white blood cells, platelets and red blood cells (RBCs) display accelerated atherosclerosis and macrophage erythrophagocytosis. To investigate whether selective erythroid Jak2VF expression promotes atherosclerosis, we developed hyperlipidemic Erythropoietin Receptor Cre mice that express Jak2VF in the erythroid lineage (VFEpoR mice). VFEpoR mice without elevated blood cell counts showed increased atherosclerotic plaque necrosis, erythrophagocytosis and ferroptosis. Selective induction of erythrocytosis with low dose erythropoietin further exacerbated atherosclerosis with prominent ferroptosis, lipid peroxidation and endothelial damage. VFEpoR RBCs had reduced antioxidant defenses and increased lipid hydroperoxides. Phagocytosis of human or murine WT or JAK2VF RBCs by WT macrophages induced ferroptosis, which was prevented by the ferroptosis inhibitor Liproxstatin-1. Liproxstatin-1 reversed increased atherosclerosis, lipid peroxidation, ferroptosis and endothelial damage in VFEpoR mice and in Jak2VF chimeric mice simulating CH, but had no impact in controls. Erythroid lineage Jak2VF expression leads to qualitative and quantitative defects in RBCs that exacerbate atherosclerosis. Phagocytosis of RBCs by plaque macrophages promotes ferroptosis, suggesting a new therapeutic target to reduce RBC-mediated cardiovascular risk.
Wenli Liu, Nataliya K. Östberg, Mustafa Yalcinkaya, Huijuan Dou, Kaori Endo-Umeda, Yang Tang, Xintong Hou, Tong Xiao, Trevor Filder, Sandra Abramowicz, Yong-Guang Yang, Oliver Soehnlein, Alan R. Tall, Nan Wang
A prophylactic hepatitis C virus (HCV) vaccine that elicits neutralizing antibodies could be key to HCV eradication. However, the genetic and antigenic properties of HCV envelope (E1E2) proteins capable of inducing anti-HCV broadly neutralizing antibodies (bNAbs) in humans have not been defined. Here, we investigated the development of bNAbs in longitudinal plasma of HCV-infected persons with persistent infection or spontaneous clearance of multiple reinfections. By measuring plasma antibody neutralization of a heterologous virus panel, we found that the breadth and potency of the antibody response increased upon exposure to multiple genetically distinct infections and with longer duration of viremia. Greater genetic divergence between infecting strains was not associated with enhanced neutralizing breadth. Rather, repeated exposure to antigenically-related, antibody sensitive E1E2s was associated with potent bNAb induction. These data reveal that a prime-boost vaccine strategy with genetically distinct, antibody sensitive viruses is a promising approach to induce potent bNAbs in humans.
Nicole Frumento, Alexis Figueroa, Tingchang Wang, Muhammad Nauman Zahid, Shuyi Wang, Guido Massaccesi, Georgia Stavrakis, James E. Crowe, Jr., Andrew I. Flyak, Hongkai Ji, Stuart C. Ray, George Shaw, Andrea L Cox, Justin R. Bailey
In lymphopenic environments, secondary lymphoid organs regulate the size of B and T-cell compartments by supporting homeostatic proliferation of mature lymphocytes. The molecular mechanisms underlying these responses and their functional consequences remain incompletely understood. To evaluate homeostasis of the mature B-cell pool during lymphopenia, we turned to an adoptive transfer model of purified follicular B-cells into Rag2-/- mouse recipients. Highly purified follicular B-cells transdifferentiated into marginal zone-like B-cells when transferred into Rag2-/- lymphopenic hosts, but not into wild-type hosts. In lymphopenic spleens, transferred B-cells gradually lost their follicular phenotype and acquired characteristics of marginal zone B-cells, as judged by cell surface phenotype, expression of integrins and chemokine receptors, positioning close to the marginal sinus, and an ability to rapidly generate functional plasma cells. Initiation of follicular to marginal zone B-cell transdifferentiation preceded proliferation. Furthermore, the transdifferentiation process was dependent on Notch2 receptors in B-cells and expression of Delta-like1 Notch ligands by splenic Ccl19-Cre+ fibroblastic stromal cells. Gene expression analysis showed rapid induction of Notch-regulated transcripts followed by upregulated Myc expression and acquisition of broad transcriptional features of marginal zone B-cells. Thus, naïve mature B-cells are endowed with plastic transdifferentiation potential in response to increased stromal Notch ligand availability during lymphopenia.
Daniela Gómez Atria, Brian T. Gaudette, Jennifer Londregan, Samantha Kelly, Eric Perkey, Anneka Allman, Bhaskar Srivastava, Ute Koch, Freddy Radtke, Burkhard Ludewig, Christian W. Siebel, Russell J.H. Ryan, Tanner F. Robertson, Janis K. Burkhardt, Warren S. Pear, David Allman, Ivan Maillard
Charcot-Marie-Tooth disease type 1A (CMT1A), the most common inherited demyelinating peripheral neuropathy, is caused by PMP22 gene duplication. Over-expression of wild-type PMP22 in Schwann cells destabilizes the myelin sheath, leading to demyelination and ultimately to secondary axonal loss and disability. No treatments currently exist that modify the disease course. The most direct route to CMT1A therapy will involve reducing PMP22 to normal levels. To accomplish this, we developed a gene therapy strategy to reduce PMP22 using novel artificial microRNAs targeting human and mouse PMP22/Pmp22 mRNAs. Our lead therapeutic microRNA, miR871, was packaged into an AAV9 vector and delivered by lumbar intrathecal injection into C61-het mice, a model of CMT1A. AAV9-miR871 efficiently transduced Schwann cells in C61-het peripheral nerves and reduced human and mouse PMP22/Pmp22 mRNA and protein levels. Treatment at early and late stages of the disease significantly improved multiple functional outcome measures and nerve conduction velocities. Furthermore, myelin pathology in lumbar roots and femoral motor nerves was ameliorated. Treated mice also showed reductions in circulating biomarkers of CMT1A. Taken together, our data demonstrate that AAV9-miR871-driven silencing of PMP22 rescues a CMT1A model and provides proof of principle for treating CMT1A using a translatable gene therapy approach.
Marina Stavrou, Alexia Kagiava, Sarah G. Choudury, Matthew J. Jennings, Lindsay M. Wallace, Allison M. Fowler, Amanda Heslegrave, Jan Richter, Christina Tryfonos, Christina Christodoulou, Henrik Zetterberg, Rita Horvath, Scott Q. Harper, Kleopas A. Kleopa
JCI This Month is a digest of the research, reviews, and other features published each month.
Cardiovascular diseases remain a leading cause of death worldwide, and treatment is complicated by the inadequacies of available therapies. This collection of reviews, developed by Daniel P. Kelly, explores emerging strategies for treating a range of cardiac pathologies, including: recent discoveries of epigenetic regulators that can be targeted to combat cardiac fibrosis, state of the art in genome-editing therapies, interactions of the vascular endothelium with metabolic tissues, current understanding of myosin modulators, and novel targets for treating dyslipidemia. Together, the reviews provide a broad update on numerous advances in cardiovascular medicine.