Meteorin-like promotes heart repair through endothelial KIT receptor tyrosine kinase.

Effective tissue repair after myocardial infarction entails a vigorous angiogenic response, guided by incompletely defined immune cell-endothelial cell interactions. We identify the monocyte- and macrophage-derived cytokine METRNL (meteorin-like) as a driver of postinfarction angiogenesis and high-affinity ligand for the stem cell factor receptor KIT (KIT receptor tyrosine kinase). METRNL mediated angiogenic effects in cultured human endothelial cells through KIT-dependent signaling pathways. In a mouse model of myocardial infarction, METRNL promoted infarct repair by selectively expanding the KIT-expressing endothelial cell population in the infarct border zone. Metrnl-deficient mice failed to mount this KIT-dependent angiogenic response and developed severe postinfarction heart failure. Our data establish METRNL as a KIT receptor ligand in the context of ischemic tissue repair.

Myeloid-Derived Growth Factor Protects Against Pressure Overload-Induced Heart Failure by Preserving Sarco/Endoplasmic Reticulum Ca2+-ATPase Expression in Cardiomyocytes.

BACKGROUND: Inflammation contributes to the pathogenesis of heart failure, but there is limited understanding of inflammation's potential benefits. Inflammatory cells secrete MYDGF (myeloid-derived growth factor) to promote tissue repair after acute myocardial infarction. We hypothesized that MYDGF has a role in cardiac adaptation to persistent pressure overload. METHODS: We defined the cellular sources and function of MYDGF in wild-type (WT), Mydgf-deficient (Mydgf-/-), and Mydgf bone marrow-chimeric or bone marrow-conditional transgenic mice with pressure overload-induced heart failure after transverse aortic constriction surgery. We measured MYDGF plasma concentrations by targeted liquid chromatography-mass spectrometry. We identified MYDGF signaling targets by phosphoproteomics and substrate-based kinase activity inference. We recorded Ca2+ transients and sarcomere contractions in isolated cardiomyocytes. Additionally, we explored the therapeutic potential of recombinant MYDGF. RESULTS: MYDGF protein abundance increased in the left ventricular myocardium and in blood plasma of pressure-overloaded mice. Patients with severe aortic stenosis also had elevated MYDGF plasma concentrations, which declined after transcatheter aortic valve implantation. Monocytes and macrophages emerged as the main MYDGF sources in the pressure-overloaded murine heart. While Mydgf-/- mice had no apparent phenotype at baseline, they developed more severe left ventricular hypertrophy and contractile dysfunction during pressure overload than WT mice. Conversely, conditional transgenic overexpression of MYDGF in bone marrow-derived inflammatory cells attenuated pressure overload-induced hypertrophy and dysfunction. Mechanistically, MYDGF inhibited G protein-coupled receptor agonist-induced hypertrophy and augmented SERCA2a (sarco/endoplasmic reticulum Ca2+-ATPase 2a) expression in cultured neonatal rat ventricular cardiomyocytes by enhancing PIM1 (Pim-1 proto-oncogene, serine/threonine kinase) expression and activity. Along this line, cardiomyocytes from pressure-overloaded Mydgf-/- mice displayed reduced PIM1 and SERCA2a expression, greater hypertrophy, and impaired Ca2+ cycling and sarcomere function compared with cardiomyocytes from pressure-overloaded WT mice. Transplanting Mydgf-/- mice with WT bone marrow cells augmented cardiac PIM1 and SERCA2a levels and ameliorated pressure overload-induced hypertrophy and dysfunction. Pressure-overloaded Mydgf-/- mice were similarly rescued by adenoviral Serca2a gene transfer. Treating pressure-overloaded WT mice subcutaneously with recombinant MYDGF enhanced SERCA2a expression, attenuated left ventricular hypertrophy and dysfunction, and improved survival. CONCLUSIONS: These findings establish a MYDGF-based adaptive crosstalk between inflammatory cells and cardiomyocytes that protects against pressure overload-induced heart failure.

Identification of the Cleavage Domain within Glycoprotein G of Herpes Simplex Virus Type 2.

Glycoprotein G (gG) from herpes simplex virus type 1 and 2 (HSV-1 and HSV-2, respectively) functions as a viral chemokine binding protein (vCKBP). Soluble recombinant forms of gG of HSV-1 and HSV-2 (SgG1 and SgG2, respectively) enhance chemokine-mediated leukocyte migration, in contrast to most known vCKBPs, including those from animal alpha-herpesviruses. Furthermore, both proteins bind to nerve growth factor (NGF), but only SgG2 enhances NGF-dependent neurite outgrowth. The basis and implications of this functional difference between the two proteins are still unknown. While gG1 and gG2 are positional homologues in the genome, they share very limited sequence homology. In fact, US4, the open reading frame encoding gG is the most divergent genetic locus between these viruses. Full-length gG1 and gG2 are type I transmembrane proteins located on the plasma membrane of infected cells and at the viral envelope. However, gG2 is larger than gG1 and is cleaved during protein maturation, secreting the N-terminal domain to the supernatant of infected cells, whereas gG1 is not. The enzyme involved in gG2 cleavage and the functional relevance of gG2 cleavage and secretion are unknown. We aim to identify the gG2 sequence required for cleavage to determine its functional role in future experiments. Our results prove the existence of at least two cleavage motifs in gG2 within the amino acid region 314-343. Transfer of this sequence to a fusion protein results in cleavage. Finally, we show that propeptide convertases like furin are responsible for gG2 cleavage.

Continuous WNT Control Enables Advanced hPSC Cardiac Processing and Prognostic Surface Marker Identification in Chemically Defined Suspension Culture.

Aiming at clinical translation, robust directed differentiation of human pluripotent stem cells (hPSCs), preferentially in chemically defined conditions, is a key requirement. Here, feasibility of suspension culture based hPSC-cardiomyocyte (hPSC-CM) production in low-cost, xeno-free media compatible with good manufacturing practice standards is shown. Applying stirred tank bioreactor systems at increasing dimensions, our advanced protocol enables routine production of about 1 million hPSC-CMs/mL, yielding ∼1.3 × 108 CM in 150 mL and ∼4.0 × 108 CMs in 350-500 mL process scale at >90% lineage purity. Process robustness and efficiency is ensured by uninterrupted chemical WNT pathway control at early stages of differentiation and results in the formation of almost exclusively ventricular-like CMs. Modulated WNT pathway regulation also revealed the previously unappreciated role of ROR1/CD13 as superior surrogate markers for predicting cardiac differentiation efficiency as soon as 72 h of differentiation. This monitoring strategy facilitates process upscaling and controlled mass production of hPSC derivatives.

Plasma Concentrations of Myeloid-Derived Growth Factor in Healthy Individuals and Patients with Acute Myocardial Infarction as Assessed by Multiple Reaction Monitoring-Mass Spectrometry.

Myeloid-derived growth factor (MYDGF in humans, Mydgf in mice) is a secreted protein with previously unknown biological functions. In a recent study, Mydgf was shown to mediate cardiac repair after acute myocardial infarction (MI) in mice. Lack of a sensitive assay to measure MYDGF in the circulation has hampered its further investigation. Here, we developed a liquid chromatography/multiple reaction monitoring-mass spectrometry MYDGF assay, employing SDS-PAGE-based protein fractionation to deplete high-abundant proteins and a stable isotope-labeled synthetic standard peptide for quantification. The assay had a lower limit of quantification of 0.8 ng/mL and a linear range up to 190 ng/mL. Within-run and total imprecision ranged from 8 to 17% and 11 to 20%, respectively. MYDGF plasma concentrations were not affected by either storage at room temperature for 4 h or up to three freeze-thaw cycles. Apparently healthy adults presented with a median (range) MYDGF concentration of 3.3 (1.3-6.7) ng/mL ( n = 120). MYDGF concentrations were elevated 2.7-fold ( P < 0.001) in patients with acute MI ( n = 101) and were associated with inflammatory biomarkers, renal dysfunction, and long-term cardiovascular mortality. The new assay and the favorable preanalytic characteristics of the analyte will facilitate studies into the pathophysiology of MYDGF and its potential use as a biomarker or protein therapeutic in patients with acute MI or other disease states.

EMC10 (Endoplasmic Reticulum Membrane Protein Complex Subunit 10) Is a Bone Marrow-Derived Angiogenic Growth Factor Promoting Tissue Repair After Myocardial Infarction.

BACKGROUND: Clinical trials of bone marrow cell-based therapies after acute myocardial infarction (MI) have produced mostly neutral results. Treatment with specific bone marrow cell-derived secreted proteins may provide an alternative biological approach to improving tissue repair and heart function after MI. We recently performed a bioinformatic secretome analysis in bone marrow cells from patients with acute MI and discovered a poorly characterized secreted protein, EMC10 (endoplasmic reticulum membrane protein complex subunit 10), showing activity in an angiogenic screen. METHODS: We investigated the angiogenic potential of EMC10 and its mouse homolog (Emc10) in cultured endothelial cells and infarcted heart explants. We defined the cellular sources and function of Emc10 after MI using wild-type, Emc10-deficient, and Emc10 bone marrow-chimeric mice subjected to transient coronary artery ligation. Furthermore, we explored the therapeutic potential of recombinant Emc10 delivered by osmotic minipumps after MI in heart failure-prone FVB/N mice. RESULTS: Emc10 signaled through small GTPases, p21-activated kinase, and the p38 mitogen-activated protein kinase (MAPK)-MAPK-activated protein kinase 2 (MK2) pathway to promote actin polymerization and endothelial cell migration. Confirming the importance of these signaling events in the context of acute MI, Emc10 stimulated endothelial cell outgrowth from infarcted mouse heart explants via p38 MAPK-MK2. Emc10 protein abundance was increased in the infarcted region of the left ventricle and in the circulation of wild-type mice after MI. Emc10 expression was also increased in left ventricular tissue samples from patients with acute MI. Bone marrow-derived monocytes and macrophages were the predominant sources of Emc10 in the infarcted murine heart. Emc10 KO mice showed no cardiovascular phenotype at baseline. After MI, however, capillarization of the infarct border zone was impaired in KO mice, and the animals developed larger infarct scars and more pronounced left ventricular remodeling compared with wild-type mice. Transplanting KO mice with wild-type bone marrow cells rescued the angiogenic defect and ameliorated left ventricular remodeling. Treating FVB/N mice with recombinant Emc10 enhanced infarct border-zone capillarization and exerted a sustained beneficial effect on left ventricular remodeling. CONCLUSIONS: We have identified Emc10 as a previously unknown angiogenic growth factor that is produced by bone marrow-derived monocytes and macrophages as part of an endogenous adaptive response that can be enhanced therapeutically to repair the heart after MI.

Quantification of small GTPase glucosylation by clostridial glucosylating toxins using multiplexed MRM analysis.

Large clostridial toxins mono-O-glucosylate small GTPases of the Rho and Ras subfamily. As a result of glucosylation, the GTPases are inhibited and thereby corresponding downstream signaling pathways are disturbed. Current methods for quantifying the extent of glucosylation include sequential [14 C]glucosylation, sequential [32 P]ADP-ribosylation, and Western Blot detection of nonglucosylated GTPases, with neither method allowing the quantification of the extent of glucosylation of an individual GTPase. Here, we describe a novel MS-based multiplexed MRM assay to specifically quantify the glucosylation degree of small GTPases. This targeted proteomics approach achieves a high selectivity and reproducibility, which allows determination of the in vivo substrate pattern of glucosylating toxins. As proof of principle, GTPase glucosylation was analyzed in CaCo-2 cells treated with TcdA, and glucosylation kinetics were determined for RhoA/B, RhoC, RhoG, Ral, Rap1, Rap2, (H/K/N)Ras, and R-Ras2.

Myeloid-derived growth factor (C19orf10) mediates cardiac repair following myocardial infarction.

Paracrine-acting proteins are emerging as a central mechanism by which bone marrow cell-based therapies improve tissue repair and heart function after myocardial infarction (MI). We carried out a bioinformatic secretome analysis in bone marrow cells from patients with acute MI to identify novel secreted proteins with therapeutic potential. Functional screens revealed a secreted protein encoded by an open reading frame on chromosome 19 (C19orf10) that promotes cardiac myocyte survival and angiogenesis. We show that bone marrow-derived monocytes and macrophages produce this protein endogenously to protect and repair the heart after MI, and we named it myeloid-derived growth factor (MYDGF). Whereas Mydgf-deficient mice develop larger infarct scars and more severe contractile dysfunction compared to wild-type mice, treatment with recombinant Mydgf reduces scar size and contractile dysfunction after MI. This study is the first to assign a biological function to MYDGF, and it may serve as a prototypical example for the development of protein-based therapies for ischemic tissue repair.