Sulfatase modifying factor 1–mediated fibroblast growth factor signaling primes hematopoietic multilineage development

Self-renewal and differentiation of hematopoietic stem cells (HSCs) are balanced by the concerted activities of the fibroblast growth factor (FGF), Wnt, and Notch pathways, which are tuned by enzyme-mediated remodeling of heparan sulfate proteoglycans (HSPGs). Sulfatase modifying factor 1 (SUMF1) activates the Sulf1 and Sulf2 sulfatases that remodel the HSPGs, and is mutated in patients with multiple sulfatase deficiency. Here, we show that the FGF signaling pathway is constitutively activated in Sumf1^−/− HSCs and hematopoietic stem progenitor cells (HSPCs). These cells show increased p-extracellular signal-regulated kinase levels, which in turn promote β-catenin accumulation. Constitutive activation of FGF signaling results in a block in erythroid differentiation at the chromatophilic erythroblast stage, and of B lymphocyte differentiation at the pro–B cell stage. A reduction in mature myeloid cells and an aberrant development of T lymphocytes are also seen. These defects are rescued in vivo by blocking the FGF pathway in Sumf1^−/− mice. Transplantation of Sumf1^−/− HSPCs into wild-type mice reconstituted the phenotype of the donors, suggesting a cell autonomous defect. These data indicate that Sumf1 controls HSPC differentiation and hematopoietic lineage development through FGF and Wnt signaling.To catalyze the hydrolysis of their natural substrates, sulfatases must be posttranslationally activated. A consensus sequence in their catalytic domain contains a cysteine that is modified into formylglycine by the formylglycine-generating enzyme encoded by the sulfatase modifying factor 1 (SUMF1) gene (Schmidt et al., 1995; Cosma et al., 2003; Dierks et al., 2003). SUMF1 exerts its activity within the ER; however, it can also be secreted and taken up by distant cells and tissues, where it relocalizes in the ER as an active enzyme (Zito et al., 2007). Multiple sulfatase deficiency (MSD) is a human monogenic disorder in which all of the sulfatase activities are simultaneously defective (Hopwood and Ballabio, 2001). Patients with MSD have mutations in SUMF1 (Cosma et al., 2004). A Sumf1^−/− strain has been generated as a mouse model of MSD, and it shows a complete loss of sulfatase activities, early mortality, congenital growth retardation, skeletal abnormalities, neurological defects, and a generalized inflammatory process in many organs (Settembre et al., 2007).These Sumf1^−/− mice represent an important resource to study developmental defects associated with SUMF1 lack of function. Indeed, SUMF1 also has putative activity during development specification. To date, 17 different sulfatases have been described in humans, and all are activated by SUMF1 (Sardiello et al., 2005). Among this large sulfatase family, Sulf1 and Sulf2 are localized on the cell surface and catalyze hydrolysis of the 6-O-sulfate of the N-acetyl glucosamines of heparan during degradation of heparan sulfate proteoglycans (HSPGs; Morimoto-Tomita et al., 2002). Wingless (Wg)/Wnt belongs to a family of secreted morphogenic proteins that control tissue-specific cell fate decisions during embryogenesis, and that bind to the heparan sulfate moieties on the cell surface of HSPGs (Logan and Nusse, 2004; Bejsovec, 2005). QSulf, the avian orthologue of human Sulf (hSulf), removes the sulfate from heparan sulfate, and releases Wnt from HSPGs. This released Wnt associates with Frizzled (Fz) and LRP5/6 receptors, resulting in inactivation of a multiprotein destruction complex, which is composed of glycogen synthase kinase-3 (GSK-3), Axin2, and adenomatous polyposis coli (APC). This inactivation leads to translocation of β-catenin into the nucleus, where it activates several target genes (Hoppler and Kavanagh, 2007). In addition to its role in embryogenesis, Wnt is involved in controlling proliferation of stem cells. Wnt3a belongs to the Wnt family, and has been shown to enhance self-renewal and maintain totipotency/multipotency of embryonic stem cells and hematopoietic stem cells (HSCs), respectively, through accumulation of β-catenin in the cell nucleus (Reya et al., 2003; Anton et al., 2007). Furthermore, transplantation of Wnt3a-treated BM increases the survival of lethally irradiated mice (Willert et al., 2003).HSCs reside in the BM and are a rare population of adult pluripotent stem cells that have the dual capability of self-renewal and differentiation into all blood cell lineages. Based on their ability to self-renew, HSCs can be defined as long-term (LT-HSCs) and short-term (ST-HSCs) HSCs. LT-HSCs have extensive self-renewal abilities and sustain life-long hematopoiesis, whereas ST-HSCs represent a more committed population with short self-renewal potential (Laiosa et al., 2006a). That Wnt signaling stimulates proliferation and self-renewal of HSCs was suggested >10 yr ago (Austin et al., 1997). More recently, it has been shown that exposure of HSCs to Wnt antagonists in vitro reduces their proliferation ability and that Bcl-2 transgenic HSCs transduced with retroviral vectors encoding β-catenin can fully reconstitute the hematopoietic compartments of recipients (Reya et al., 2003). On the other hand, stable expression of β-catenin from the Rosa26 locus in transgenic mice led to loss of HSC repopulation and multilineage differentiation potential (Kirstetter et al., 2006). Mice with β-catenin deletion in their HSCs show normal hematopoiesis (Cobas et al., 2004). These apparently contradictory data might reveal some novel aspects of the function of the Wnt signaling pathway. Indeed, it appears that different and specific amounts of β-catenin confer divergent phenotypes and differentiation capabilities to HSCs.In addition, a fine-tuned balance between different signaling pathways might be important to control self-renewal and differentiation of HSCs. The Notch and Wnt pathways have been shown to act in synergy to maintain the HSC pool, with Wnt being important to induce proliferation and support viability of HSCs, and Notch being important in the maintenance of HSCs in an undifferentiated state (Duncan et al., 2005). Furthermore, in vivo inhibition of GSK-3β augments the repopulation abilities of transplanted HSCs via modulation of gene targets of both the Wnt and Notch pathways (Trowbridge et al., 2006).Interestingly, the activities of Sulf1 and Sulf2 modulate Wnt signaling by modifying the sulfation state of the heparan sulfates contained in HSPGs, thereby impairing fibroblast growth factor (FGF) signaling. Crystal structure studies have demonstrated that binding of FGF1 and FGF2 to the FGF receptor is stabilized by 6-O-sulfation of the heparan sulfates of the HSPGs (Pellegrini et al., 2000). Thus, through desulfation of these heparan sulfates, hSulf1 can down-regulate FGF-dependent extracellular signal-regulated kinase (ERK) kinase activity (Lai et al., 2003). FGF1 and FGF2 signaling preserves ex vivo expansion of primitive HSCs (Yeoh et al., 2006).Thus, an intriguing question is raised: does Sumf1 act as a master regulator of the signaling of the Wnt and FGF pathways through activation of Sulf1 and/or Sulf2, resulting, in turn, in modulation of developmental signals and of HSC self-renewal and cell lineage commitment?Here, we show that SUMF1 has a role in promoting cell lineage commitment. Sumf1^−/− HSCs and hematopoietic stem progenitor cells (HSPCs) show constitutive activation of the FGF signaling pathway, and the consequent increase in p-ERK leads to GSK3-β phosphorylation and β-catenin accumulation. In turn, Notch is also accumulated. These altered signaling pathways lead to a block of erythroid, myeloid, and lymphoid differentiation in Sumf1^−/− mice. We also provide evidence that Sulf2^−/− mice recapitulates the Sumf1^−/− BM phenotype up to a certain point. In contrast, Ids^−/− and Sgsh^−/− mice, which are two mouse loss-of-function sulfatase models, did not show any relevant hematopoietic differentiation defects. Furthermore, upon transplantation of Sumf1^−/− HSPCs into lethally irradiated WT mice, there was impaired differentiation of the donor cells, which recapitulates the hematopoietic defects seen in the Sumf1^−/− mice; furthermore, in the recipient mice, a decrease in the frequency of LT-HSCs was observed. These findings confirm that the differentiation impairment of the mutant HSCs and their progeny is caused by SUMF1 loss of function, and not by different environmental features.     

影响因子（impact factor）

影响因子是美国科学信息情报研究所（Institute？for？Scientific？Information,ISI）的期刊引证报告（JCR）中的一项数据。指的是某一期刊的文章在特定年份或时期被引用的频率，是衡量学术期刊影响力的一个重要指标。是用该期刊前2年发表论文在当年被引用的次数除以该期刊前2年发表论文的总数所得到的值。可以用来评估同一研究领域不同期刊的相对重要性。这是一个国际上通行的期刊评价指标。     

Experimental research of curing sciatic nerve injury using nerve growth factor and basic fibroblast growth factor combination

AIM:To explore the co-effect of nerve growth factor (NGF)and basic fibroblast growth factor(bFGF) on the sciatic nerve after injury.METHODS:96 rats were divided into normal saline group,NGF group,bFGF group and NGF bFGF group.Sciatic nerve function index(SFI),nerve conduction velocity,regeneration axon counting were detected in the 3rd,6th,9th,12th week postinjury.RESULTS:The end of SFI,nerve conduction velocity,regeneration axon counting in NGF bFGF group were higher than those in the other groups.CONCLUSION:The co-effect of NGF and bFGF on sciatic nerve is better than the effect of NGF or bFGF alone.     

Serum uric acid--a cardiovasular risk factor?

Serum uric acid represents an important, independent risk factor for cardiovascular and renal disease in patients with hypertension, heart failure, or diabetes. Elevated serum uric acid is highly predictive of mortality in patients with heart failure or coronary artery disease and of cardiovascular events in patients with diabetes. Although the mechanism(s) by which uric acid may play a pathogenetic role in cardiovascular disease is unclear, hyperuricemia is associated with deleterious effects on endothelial dysfunction, oxidative metabolism, platelet adhesiveness, hemrheology, and aggregation. Whether a reduction in uric acid impacts CV and renal disease remains to be determined. However, recent findings from LIFE in hypertensive patients with LVH suggest the possibility that a treatment-induced decrease in serum uric acid may indeed attenuate cardiovascular risk. Almost one third of the treatment benefit of a losartan-based versus atenolol-based therapy on the composite endpoint (death, myocardial infarction, or stroke) may be ascribed to differences in achieved serum uric acid levels. Clearly, randomized clinical trials are needed to investigate further the long-term cardioprotective benefits issue of reducing hyperuricemia in hypertensive patients.     

High concentrations of circulating macrophage migration inhibitory factor in patients with severe blunt trauma: Is serum macrophage migration inhibitory factor concentration a valuable prognostic factor?

OBJECTIVE: To determine serum concentrations of macrophage migration inhibitory factor and other cytokines in severe blunt trauma patients in critical settings and to evaluate their association with patient outcome. DESIGN: Prospective, observational study. SETTING: Emergency department and surgical intensive care unit of a university hospital. PATIENTS: Fifty-four severe blunt trauma patients with systemic inflammatory response syndrome requiring intensive care, emergency surgical intervention, or both were enrolled in the study. Forty-four patients with minor injuries were the controls. INTERVENTIONS: Serum macrophage migration inhibitory factor concentrations were measured in the emergency department <4 hrs postinjury (day 1) and the surgical intensive care unit 24 hrs later (day 2). Blood samples for determination of tumor necrosis factor-alpha, interleukin-6, interleukin-8, and interleukin-10 were measured both in patients with severe blunt trauma and in controls. The Acute Physiology and Chronic Health Evaluation II, Injury Severity Score, Revised Trauma Score, and Trauma Revised Injury Severity Score were used for clinical evaluation of trauma severity. MEASUREMENTS AND MAIN RESULTS: Serum macrophage migration inhibitory factor concentrations were higher in severe blunt trauma patients than in controls; were significantly correlated with Acute Physiology and Chronic Health Evaluation II, Revised Trauma Score, and Trauma Revised Injury Severity Score scores in severe blunt trauma patients but not in controls; and were higher in nonsurvivors than in survivors. CONCLUSIONS: Our data suggest that the serum macrophage migration inhibitory factor concentration is higher in severe blunt trauma and that it reflects the severity of trauma. The serum macrophage migration inhibitory factor concentration might be a valuable predictor for the outcome of severe blunt trauma.     

Tissue factor assays as diagnostic tools for cancer? Correlation between urinary and monocyte tissue factor activity

Monocyte and urinary tissue factors (mTF and uTF) are both elevated in a number of pathologic conditions, including cancer. This study validates the best available uTF and mTF assays as diagnostic tools for cancer and examines if uTF levels reflect monocyte activation. Using kinetic chromogenic assays for uTF and mTF (measured on fresh resting cells [baseline], unstimulated cells, and lipopolysaccharide [LPS]-stimulated cells), we assessed TF levels in normal individuals, surgical controls, and patients with benign and malignant diseases. Each benign disease group was stratified as inflammatory or noninflammatory. Controls and benign noninflammatory results were indistinguishable. The malignant and inflammatory groups showed raised uTF levels over controls (p < 0.001). mTF levels differ similarly. For mTF and uTF assays, there was no significant difference between the malignant and inflammatory groups. The relative operating characteristic (ROC) curve plots sensitivity against false positive rate (1-specificity) for all possible cutoff values of a diagnostic test. Assay performance is assessed as the area under the curve (AUC). The ROC curve for the uTF assay displayed both sensitivity and specificity for cancer, the AUC being 0.83. Of the three mTF levels, LPS-stimulated cells gave the optimum curve (AUC = 0.71). uTF showed a weak to moderate association with mTF levels but correlated best and was statistically significant when compared with levels in the LPS-stimulated cells. uTF represents an intrinsic, kidney-derived, physiologic concentration rather than that of preactivated or postactivated monocytes. In conclusion, both uTF and LPS-stimulated mTF levels showed sensitivity and specificity in detecting cancer and inflammatory diseases. However, the two forms of TF appear to be independently derived.     

Tissue factor and tissue factor pathway inhibitor: a potential role in pregnancy and obstetric vascular complications?

Tissue factor (TF) is the principal cellular initiator of normal blood coagulation. As a result it is considered to be a major regulator of haemostasis and thrombogenesis. In vivo TF activity is regulated by specific circulating inhibitor known as "tissue factor pathway inhibitor (TFPI)". TF is also essential for other cellular processes including embryogenesis and angiogenesis as well as in implantation where it is particularly important in the first trimester. TF is highly expressed in syncytiotrophoblasts (STB) while TFPI is expressed in human umbilical vein endothelial cells (HUVEC). TFPI may be internalized via an endocytic pathway and recycled to the cell surface. The procoagulant tendency of STB may reflect a physiological need for immediate inhibition of hemorrhage in the placental intervillous spaces. Furthermore, the haemostatic balance involving STB and HUVEC may be critical for normal placental function and pregnancy outcome. Homozygous knockouts of both TF and TFPI are generally lethal in fetal mice; heterozygotes survive but with altered coagulation parameters. Despite their apparent association with placental microcirculation-thrombi-formation only few studies have addressed the role of TF and TFPI in the pathogenesis of gestational vascular complications. In this context, detailed studies could provide clinically relevant information.     

Homocysteine: an emergent cardiovascular risk factor?

Cardiovascular disease is the leading cause of mortality and disability in the western world. In the last years, the accumulation of evidence coming from both retrospective and prospective clinical studies has led to an increased interest in the potential role of mild hyperhomocysteinemia as a major, independent risk factor for cardiovascular disease. The present paper reviews the position of homocysteine in metabolism to understand the pathogenesis of hyperhomocysteinemia, as well as the clinical data pointing to its proposed role as an independent cardiovascular disease risk factor.     

Krüppel-like factor 4 regulates macrophage polarization

Current paradigms suggest that two macrophage subsets, termed M1 and M2, are involved in inflammation and host defense. While the distinct functions of M1 and M2 macrophages have been intensively studied - the former are considered proinflammatory and the latter antiinflammatory - the determinants of their speciation are incompletely understood. Here we report our studies that identify Krüppel-like factor 4 (KLF4) as a critical regulator of macrophage polarization. Macrophage KLF4 expression was robustly induced in M2 macrophages and strongly reduced in M1 macrophages, observations that were recapitulated in human inflammatory paradigms in vivo. Mechanistically, KLF4 was found to cooperate with Stat6 to induce an M2 genetic program and inhibit M1 targets via sequestration of coactivators required for NF-κB activation. KLF4-deficient macrophages demonstrated increased proinflammatory gene expression, enhanced bactericidal activity, and altered metabolism. Furthermore, mice bearing myeloid-specific deletion of KLF4 exhibited delayed wound healing and were predisposed to developing diet-induced obesity, glucose intolerance, and insulin resistance. Collectively, these data identify KLF4 as what we believe to be a novel regulator of macrophage polarization.