Macrophages retain hematopoietic stem cells in the spleen via VCAM-1

Splenic myelopoiesis provides a steady flow of leukocytes to inflamed tissues, and leukocytosis correlates with cardiovascular mortality. Yet regulation of hematopoietic stem cell (HSC) activity in the spleen is incompletely understood. Here, we show that red pulp vascular cell adhesion molecule 1 (VCAM-1)⁺ macrophages are essential to extramedullary myelopoiesis because these macrophages use the adhesion molecule VCAM-1 to retain HSCs in the spleen. Nanoparticle-enabled in vivo RNAi silencing of the receptor for macrophage colony stimulation factor (M-CSFR) blocked splenic macrophage maturation, reduced splenic VCAM-1 expression and compromised splenic HSC retention. Both, depleting macrophages in CD169 iDTR mice or silencing VCAM-1 in macrophages released HSCs from the spleen. When we silenced either VCAM-1 or M-CSFR in mice with myocardial infarction or in ApoE^−/− mice with atherosclerosis, nanoparticle-enabled in vivo RNAi mitigated blood leukocytosis, limited inflammation in the ischemic heart, and reduced myeloid cell numbers in atherosclerotic plaques.Leukocytosis correlates closely with cardiovascular mortality. In the steady state, blood leukocytes derive exclusively from bone marrow hematopoietic stem cells (HSCs). Supporting cells (Sugiyama et al., 2006; Ding et al., 2012; Ding and Morrison, 2013), including macrophages (Winkler et al., 2010; Chow et al., 2011), maintain the bone marrow HSC niche and regulate hematopoietic stem and progenitor cell (HSPC) activity by supplying various cytokines and retention factors. Systemic inflammation can stimulate extramedullary hematopoiesis in adult mice and humans. Splenic myelopoiesis supplies inflammatory monocytes to atherosclerotic plaques (Robbins et al., 2012) and the ischemic myocardium (Leuschner et al., 2012). In ischemic heart disease, HSPCs emigrate from the bone marrow, seed the spleen, and amplify leukocyte production (Dutta et al., 2012). Splenic HSPCs localize in the red pulp near the sinusoids in parafollicular areas (Kiel et al., 2005). Likewise, after adoptive transfer of GFP⁺ HSPCs, GFP⁺ colonies populate the splenic red pulp of atherosclerotic ApoE^−/− mice (Robbins et al., 2012). During myocardial infarction (MI), proinflammatory monocytes derived from the spleen accelerate atherosclerotic progression (Dutta et al., 2012). Collectively, these data suggest that splenic myelopoiesis has promise as a therapeutic target; however, the components of the splenic hematopoietic niche are incompletely understood, especially compared with the well-studied bone marrow niche. Understanding HSC retention factors and their regulation in the spleen was the purpose of this study.Because the spleen harbors very few HSCs in the steady state, we investigated the splenic hematopoietic niche after injecting the Toll-like receptor ligand LPS to activate extramedullary hematopoiesis. In the bone marrow, macrophages are an integral part of the HSC niche (Winkler et al., 2010; Chow et al., 2011) and differentiation depends on the receptor for macrophage colony-stimulating factor (M-CSFR, CD115; Auffray et al., 2009). We thus hypothesized that splenic hematopoietic niche assembly also requires M-CSFR signaling. In line with knockout studies (Takahashi et al., 1994; Dai et al., 2002), in vivo knockdown of M-CSFR with nanoparticle-encapsulated siRNA reduced splenic macrophage numbers substantially. Interestingly, decreased macrophage numbers were associated with a reduction of splenic HSCs. Depleting macrophages with diphtheria toxin (DT) in CD169 iDTR mice reproduced the findings obtained with M-CSF–directed siRNA treatment, thereby indicating that macrophages have a key role in splenic HSC maintenance. To investigate how splenic macrophages retain HSCs, we measured changes in splenic expression of major bone marrow retention factors after M-CSFR silencing. Silencing M-CSFR selectively reduced splenic VCAM-1, and the adhesion molecule was primarily expressed by macrophages. Inhibiting macrophage expression of VCAM-1 with siRNA targeting this adhesion molecule reduced splenic HSPC numbers. Finally, we found that M-CSFR and macrophage-directed VCAM-1 silencing in mice with atherosclerosis mitigated blood leukocytosis and dampened inflammation in atherosclerotic plaques and the infarcted myocardium. These data reveal the importance of VCAM-1 expression by splenic macrophages for extramedullary hematopoiesis and illustrate the therapeutic potential of RNAi as an antiinflammatory that mutes emergency overproduction and provision of myeloid cells.     

The Impact of Graphene and Diatomite Admixtures on the Performance and Properties of High-Performance Magnesium Oxychloride Cement Composites

A high-performance magnesium oxychloride cement (MOC) composite composed of silica sand, diatomite powder, and doped with graphene nanoplatelets was prepared and characterized. Diatomite was used as a 10 vol.% replacement for silica sand. The dosage of graphene was 0.5 wt.% of the sum of the MgO and MgCl₂·6H₂O masses. The broad product characterization included high-resolution transmission electron microscopy, X-ray diffraction, X-ray fluorescence, scanning electron microscopy and energy dispersive spectroscopy analyses. The macrostructural parameters, pore size distribution, mechanical resistance, stiffness, hygric and thermal parameters of the composites matured for 28-days were also the subject of investigation. The combination of diatomite and graphene nanoplatelets greatly reduced the porosity and average pore size in comparison with the reference material composed of MOC and silica sand. In the developed composites, well stable and mechanically resistant phase 5 was the only precipitated compound. Therefore, the developed composite shows high compactness, strength, and low water imbibition which ensure high application potential of this novel type of material in the construction industry.     

Cardiorespiratory fitness predicts insulin action and secretion in healthy individuals

Long-term cardiorespiratory fitness (CRF) and the development of type 2 diabetes mellitus are inversely correlated. Here, we examined the relationships between peak oxygen uptake (VO(2)peak), on the one hand, and glucose infusion rate at rest (GIR(rest)) and during exercise (GIR(exercise)), as well as insulin secretion (both the early and late phases of response [area under the curve {AUC}(insulin)]), on the other. Eight male and 4 female healthy, lean, nonsmoking volunteers were recruited. The VO(2)peak was measured during graded exercise on a cycle ergometer until exhaustion was reached. The GIR(rest) and GIR(exercise) were determined using a euglycemic-hyperinsulinemic clamp, and insulin secretion at rest was evaluated with an intravenous glucose tolerance test. The VO(2)peak correlated positively to GIR(rest) (r = 0.81, P = .001) and GIR(exercise) (r = 0.87, P < .001) and negatively to AUC(insulin) (r = -0.64, P = .03). The respiratory exchange ratio (RER) during insulin infusion was positively correlated to GIR(rest) (r = 0.83, P < .001) and GIR(exercise) (r = 0.86, P < .01) and negatively correlated to both the early insulin response (r = -0.86, P < .0001) and AUC(insulin) (r = -0.87, P = .001). The VO(2)peak accounted for 45% of the variability in RER (R(2) = 0.45, P = .035). In this healthy population, CRF and RER were highly correlated to insulin sensitivity and secretion, as well as to the ability to alter the substrate being oxidized during exercise. These findings highlight the importance of good CRF to maintaining normal insulin action.     

Treatment of hepatitis C virus infection in adults and children: updated Swedish consensus recommendations

Swedish recommendations for the treatment of hepatitis C virus (HCV) infection were updated at a recent expert meeting. Therapy for acute HCV infection should be initiated if spontaneous resolution does not occur within 12 weeks. The recommended standard-of-care therapy for chronic HCV genotype 1 infection is an HCV protease inhibitor in combination with peginterferon (peg-IFN) and ribavirin. Treatment is strongly recommended in patients with bridging fibrosis and cirrhosis, whereas in patients with less advanced fibrosis, deferring therapy may be preferential in light of likely therapeutic improvements in the near future. Patients with chronic genotype 2/3 infection should generally be treated with peg-IFN and ribavirin for 24 weeks. In patients with a very rapid viral response (i.e. HCV RNA below 1000 IU/ml on day 7), or favourable baseline characteristics and undetectable HCV RNA week 4, treatment can be shortened to 12-16 weeks, provided that no dose reductions are needed.     

Unbiased plasma proteomics for novel diagnostic biomarkers in cardiovascular disease: identification of quiescin Q6 as a candidate biomarker of acutely decompensated heart failure

Aims Biochemical marker testing has improved the evaluation and management of patients with cardiovascular diseases over the past decade. Natriuretic peptides (NPs), used in clinical practice to assess cardiac dysfunction, exhibit many limitations, however. We used an unbiased proteomics approach for the discovery of novel diagnostic plasma biomarkers of heart failure (HF). Methods and results A proteomics pipeline adapted for very low-abundant plasma proteins was applied to clinical samples from patients admitted with acute decompensated HF (ADHF). Quiescin Q6 (QSOX1), a protein involved in the formation of disulfide bridges, emerged as the best performing marker for ADHF (with an area under the receiver operator characteristic curve of 0.86, 95% confidence interval: 0.79-0.92), and novel isoforms of NPs were also identified. Diagnostic performance of QSOX1 for ADHF was confirmed in 267 prospectively collected subjects of whom 76 had ADHF. Combining QSOX1 to B-type NP (BNP) significantly improved diagnostic accuracy for ADHF by particularly improving specificity. Using thoracic aortic constriction in rats, QSOX1 was specifically induced within both left atria and ventricles at the time of HF onset. Conclusion The novel biomarker QSOX1 accurately identifies ADHF, particularly when combined with BNP. Through both clinical and experimental studies we provide lines of evidence for a link between ADHF and cardiovascular production of QSOX1.