M-CSF: haematopoietic growth factor or inflammatory cytokine?

An Exploration of the Role of Osteoclast Lineage Cells in Bone Tissue Engineering

Bone defects because of age, trauma, and surgery, which are exacerbated by medication side effects and common diseases such as osteoporosis, diabetes, and rheumatoid arthritis, are a problem of epidemic scale. The present clinical standard for treating these defects includes autografts and allografts. Although both treatments can promote robust regenerative outcomes, they fail to strike a desirable balance of availability, side effect profile, consistent regenerative efficacy, and affordability. This difficulty has contributed to the rise of bone tissue engineering (BTE) as a potential avenue through which enhanced bone regeneration could be delivered. BTE is founded upon a paradigm of using biomaterials, bioactive factors, osteoblast lineage cells (ObLCs), and vascularization to cue deficient bone tissue into a state of regeneration. Despite promising preclinical results, BTE has had modest success in being translated into the clinical setting. One barrier has been the simplicity of its paradigm relative to the complexity of biological bone. Therefore, this paradigm must be critically examined and expanded to better account for this complexity. One potential avenue for this is a more detailed consideration of osteoclast lineage cells (OcLCs). Although these cells ostensibly oppose ObLCs and bone regeneration through their resorptive functions, a myriad of investigations have shed light on their potential to influence bone equilibrium in more complex ways through their interactions with both ObLCs and bone matrix. Most BTE research has not systematically evaluated their influence. Yet contrary to expectations associated with the paradigm, a selection of BTE investigations has demonstrated that this influence can enhance bone regeneration in certain contexts. In addition, much work has elucidated the role of many controllable scaffold parameters in both inhibiting and stimulating the activity of OcLCs in parallel to bone regeneration. Therefore, this review aims to detail and explore the implications of OcLCs in BTE and how they can be leveraged to improve upon the existing BTE paradigm.

Colony stimulating factor-1 receptor drives glomerular parietal epithelial cell activation in focal segmental glomerulosclerosis

Parietal epithelial cells (PECs) are kidney progenitor cells with similarities to a bone marrow stem cell niche. In focal segmental glomerulosclerosis (FSGS) PECs become activated and contribute to extracellular matrix deposition. Colony stimulating factor-1 (CSF-1), a hematopoietic growth factor, acts via its specific receptor, CSF-1R, and has been implicated in several glomerular diseases, although its role on PEC activation is unknown. Here, we found that CSF-1R was upregulated in PECs and podocytes in biopsies from patients with FSGS. Through in vitro studies, PECs were found to constitutively express CSF-1R. Incubation with CSF-1 induced CSF-1R upregulation and significant transcriptional regulation of genes involved in pathways associated with PEC activation. Specifically, CSF-1/CSF-1R activated the ERK1/2 signaling pathway and upregulated CD44 in PECs, while both ERK and CSF-1R inhibitors reduced CD44 expression. Functional studies showed that CSF-1 induced PEC proliferation and migration, while reducing the differentiation of PECs into podocytes. These results were validated in the Adriamycin-induced FSGS experimental mouse model. Importantly, treatment with either the CSF-1R-specific inhibitor GW2580 or Ki20227 provided a robust therapeutic effect. Thus, we provide evidence of the role of the CSF-1/CSF-1R pathway in PEC activation in FSGS, paving the way for future clinical studies investigating the therapeutic effect of CSF-1R inhibitors on patients with FSGS.

Characterizing 3T3-L1 MBX Adipocyte Cell Differentiation Maintained with Fatty Acids as an In Vitro Model to Study the Effects of Obesity

The increasing prevalence of obesity has prompted intensive research into understanding its role in pathogenesis and designing appropriate treatments. To determine the signals generated from the interaction of fat cells with a target organ, a reliable white adipocyte model in vitro is needed. Differentiated fibroblasts are the most extensively studied using in vitro cell models of white adipocytes. However, it can be argued that differentiated fibroblasts minimally recapitulate the consequences of obesity. Here, we describe 3T3-L1 MBX cells as a culture model for studying obese adipocytes and their effects. Differentiation of 3T3-L1 MBX cells was at first optimized and then maintained in the presence of fatty acids cocktail combination to induce the obese condition. Lipid accumulation and adipokine secretion profiles were analyzed. Results showed that fatty acid-maintained, differentiated 3T3-L1 MBX cells had significantly greater accumulation of lipids and significant changes in the adipokine secretions in comparison to differentiated 3T3-L1 MBX cells maintained in medium without fatty acids. To elucidate the molecular changes associated with adipogenesis and lipid accumulation profile of 3T3-L1 MBX cells, we have also explored the expression of some of the regulatory proteins related to the development and maintenance of adipocytes from the preadipocyte lineage.

Molecular characterization, gene expression and functional analysis of goldfish (Carassius auratus L.) macrophage colony stimulating factor 2

Background

Macrophage colony-stimulating factor 2 (MCSF-2) is an important cytokine that controls how cells of the monocyte/macrophage lineage proliferate, differentiate, and survive in vertebrates. Two isoforms of MCSF have been identified in fish, each exhibiting distinct gene organization and expression patterns. In this study, we investigated a goldfish MCSF-2 gene in terms of its immunomodulatory and functional properties.

Methods

In this study, goldfish were acclimated for 3 weeks and sedated with TMS prior to handling. Two groups of fish were used for infection experiments, and tissues from healthy goldfish were collected for RNA isolation. cDNA synthesis was performed, and primers were designed based on transcriptome database sequences. Analysis of gfMCSF-2 sequences, including nucleotide and amino acid analysis, molecular mass prediction, and signal peptide prediction, was conducted. Real-time quantitative PCR (qPCR) was used to analyze gene expression levels, while goldfish head kidney leukocytes (HKLs) were isolated using standard protocols. The expression of gfMCSF-2 in activated HKLs was investigated, and recombinant goldfish MCSF-2 was expressed and purified. Western blot analysis, cell proliferation assays, and flow cytometric analysis of HKLs were performed. Gene expression analysis of transcription factors and pro-inflammatory cytokines in goldfish head kidney leukocytes exposed to rgMCSF-2 was conducted. Statistical analysis using one-way ANOVA and Dunnett's post hoc test was applied.

Results

We performed a comparative analysis of MCSF-1 and MCSF-2 at the protein and nucleotide levels using the Needleman-Wunsch algorithm. The results revealed significant differences between the two sequences, supporting the notion that they represent distinct genes rather than isoforms of the same gene. Sequence alignment demonstrated high sequence identity with MCSF-2 homologs from fish species, particularly C. carpio, which was supported by phylogenetic analysis. Expression analysis in various goldfish tissues demonstrated differential expression levels, with the spleen exhibiting the highest expression. In goldfish head kidney leukocytes, gfMCSF-2 expression was modulated by chemical stimuli and bacterial infection, with upregulation observed in response to lipopolysaccharide (LPS) and live Aeromonas hydrophila. Recombinant gfMCSF-2 (rgMCSF-2) was successfully expressed and purified, showing the ability to stimulate cell proliferation in HKLs. Flow cytometric analysis revealed that rgMCSF-2 induced differentiation of sorted leukocytes at a specific concentration. Moreover, rgMCSF-2 treatment upregulated TNFα and IL-1β mRNA levels and influenced the expression of transcription factors, such as MafB, GATA2, and cMyb, in a time-dependent manner.

Conclusion

Collectively, by elucidating the effects of rgMCSF-2 on cell proliferation, differentiation, and the modulation of pro-inflammatory cytokines and transcription factors, our findings provided a comprehensive understanding of the potential mechanisms underlying gfMCSF-2-mediated immune regulation. These results contribute to the fundamental knowledge of MCSF-2 in teleosts and establish a foundation for further investigations on the role of gfMCSF-2 in fish immune responses.

Oncostatin M attenuates tumor necrosis factor-α-induced synthesis of macrophage-colony stimulating factor via suppression of Akt in osteoblasts

BACKGROUND

Oncostatin M produced by osteal macrophages, a cytokine that belongs to the interleukin-6 family, is implicated in bone fracture healing. Macrophage colony-stimulating factor (M-CSF) secreted from osteoblasts plays an important role in osteoclastogenesis. We have previously reported that tumor necrosis factor-α (TNF-α), a potent bone resorptive agent, stimulates the activation of p44/p42 mitogen-activated protein (MAP) kinase, Akt, and p70 S6 kinase in osteoblast-like MC3T3-E1 cells, and induces the synthesis of M-CSF at least in part via Akt.

OBJECTIVE

In the present study, we investigated whether oncostatin M affects the TNF-α-induced M-CSF synthesis in MC3T3-E1 cells and the underlying mechanisms.

METHODS

Clonal osteoblast-like MC3T3-E1 cells were treated with oncostatin M or rapamycin and then stimulated with TNF-α. M-CSF release was assessed by ELISA. M-CSF mRNA expression level was assessed by real-time RT-PCR. Phosphorylation of Akt, p44/p42 MAP kinase, and p70 S6 kinase was detected by Western blot analysis.

RESULTS

Oncostatin M dose-dependently reduced the TNF-α-stimulated M-CSF release. The expression of M-CSF mRNA induced by TNF-α was significantly suppressed by oncostatin M. Rapamycin, an inhibitor of mTOR/p70 S6 kinase, had little effect on the M-CSF release by TNF-α. Oncostatin M significantly reduced the TNF-α-induced phosphorylation of Akt and p44/p42 MAP kinase. However, the p70 S6 kinase phosphorylation by TNF-α was not affected by oncostatin M.

CONCLUSION

These results strongly suggest that oncostatin M attenuates TNF-α-stimulated synthesis of M-CSF in osteoblasts, and the inhibitory effect is exerted at a point upstream of Akt and p44/p42 MAP kinase but not p70 S6 kinase.

Hematologic dysfunction in cancer: Mechanisms, effects on antitumor immunity, and roles in disease progression

With the major advances in cancer immunology and immunotherapy, it is critical to consider that most immune cells are short-lived and need to be continuously replenished from hematopoietic stem and progenitor cells. Hematologic abnormalities are prevalent in cancer patients, and many ground-breaking studies over the past decade provide insights into their underlying cellular and molecular mechanisms. Such studies demonstrate that the dysfunction of hematopoiesis is more than a side-effect of cancer pathology, but an important systemic feature of cancer disease. Here we review these many advances, covering the cancer-associated phenotypes of hematopoietic stem and progenitor cells, the dysfunction of myelopoiesis and erythropoiesis, the importance of extramedullary hematopoiesis in cancer disease, and the developmental origins of tumor associated macrophages. We address the roles of many secreted mediators, signaling pathways, and transcriptional and epigenetic mechanisms that mediate such hematopoietic dysfunction. Furthermore, we discuss the important contribution of the hematopoietic dysfunction to cancer immunosuppression, the possible avenues for therapeutic intervention, and highlight the unanswered questions and directions for future work. Overall, hematopoietic dysfunction is established as an active component of the cancer disease mechanisms and an important target for therapeutic intervention.

Selective estrogen receptor modulators, acting as agonists of estrogen receptor α in osteoblasts, reduce the TGF-β-induced synthesis of macrophage colony-stimulating factor via inhibition of JNK signaling pathway

Selective estrogen receptor modulator (SERM) binds to estrogen receptors (ERs) and acts as both an agonist or an antagonist, depending on the target tissue. Raloxifene and bazedoxifene as SERMs are currently used hormone replacement medicines for postmenopausal osteoporosis. Macrophage colony-stimulating factor (M-CSF) secreted from osteoblasts promotes osteoclastogenesis. We have previously demonstrated that transforming growth factor (TGF)-β induces the synthesis of M-CSF via SMAD2/3, p38 mitogen-activated protein kinase (MAPK), p44/p42 MAPK and c-Jun N-terminal kinase (JNK) in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether SERM affects the M-CSF synthesis by TGF-β in MC3T3-E1 cells. Raloxifene and bazedoxifene significantly suppressed the synthesis of M-CSF. PPT, an ERα agonist, but not ERB041, an ERβ agonist, inhibited the release of M-CSF. MPP, an ERα antagonist, reversed the suppression by raloxifene of the M-CSF release. Raloxifene attenuated the TGF-β-induced phosphorylation of JNK but not SMAD3, p42 MAPK and p38 MAPK. Bazedoxifene and PPT also inhibited the phosphorylation of JNK. Furthermore, MPP, an ERα antagonist, reversed the suppression by both raloxifene and bazedoxifene of the phosphorylation of JNK. Our results strongly indicate that raloxifene and bazedoxifene, SERMs, suppress the TGF-β-induced synthesis of M-CSF through ERα-mediated inhibition of JNK pathway in osteoblasts.

Immunomodulatory effects of chicken cathelicidin-2 on a primary hepatic cell co-culture model

Cathelicidin-2 is an antimicrobial peptide (AMP) produced as part of the innate immune system of chickens and might be a new candidate to combat infection and inflammation within the gut-liver axis. Studying the hepatic immune response is of high importance as the liver is primarily exposed to gut-derived pathogen-associated molecular patterns. The aim of the present study was to assess the effects of chicken cathelicidin-2 alone or combined with lipoteichoic acid (LTA) or phorbol myristate acetate (PMA) on cell viability, immune response and redox homeostasis in a primary hepatocyte-non-parenchymal cell co-culture of chicken origin. Both concentrations of cathelicidin-2 decreased the cellular metabolic activity and increased the extracellular lactate dehydrogenase (LDH) activity reflecting reduced membrane integrity. Neither LTA nor PMA affected these parameters, and when combined with LTA, cathelicidin-2 could not influence the LDH activity. Cathelicidin-2 had an increasing effect on the concentration of the proinflammatory CXCLi2 and interferon- (IFN-)γ, and on that of the anti-inflammatory IL-10. Meanwhile, macrophage colony stimulating factor (M-CSF), playing a complex role in inflammation, was diminished by the AMP. LTA elevated IFN-γ and decreased M-CSF levels, while PMA only increased the concentration of M-CSF. Both concentrations of cathelicidin-2 increased the H2O2 release of the cells, but the concentration of malondialdehyde as a lipid peroxidation marker was not affected. Our findings give evidence that cathelicidin-2 can also possess anti-inflammatory effects, reflected by the alleviation of the LTA-triggered IFN-γ elevation, and by reducing the M-CSF production induced by PMA. Based on the present results, cathelicidin-2 plays a substantial role in modulating the hepatic immune response with a multifaceted mode of action. It was found to have dose-dependent effects on metabolic activity, membrane integrity, and reactive oxygen species production, indicating that using it in excessively high concentrations can contribute to cell damage. In conclusion, cathelicidin-2 seems to be a promising candidate for future immunomodulating drug development with an attempt to reduce the application of antibiotics.

The influence of M-CSF on fracture healing in a mouse model

Macrophage colony-stimulating factor 1 (M-CSF) is known to play a critical role during fracture repair e.g. by recruiting stem cells to the fracture site and impacting hard callus formation by stimulating osteoclastogenesis. The aim of this experiment was to study the impact of systemic M-CSF application and its effect on bony healing in a mouse model of femoral osteotomy. Doing so, we studied 61 wild type (wt) mice (18-week-old female C57BL/6) which were divided into three groups: (1) femoral osteotomy, (2) femoral osteotomy + stabilization with external fixator and (3) femoral osteotomy + stabilization with external fixator + systemic M-CSF application. Further, 12 op/op mice underwent femoral osteotomy and served as proof of concept. After being sacrificed at 28 days bony bridging was evaluated ex vivo with µCT, histological and biomechanical testing. Systemic M-CSF application impacted osteoclasts numbers, which were almost as low as found in op/op mice. Regarding callus size, the application of M-CSF in wt mice resulted in significantly larger calluses compared to wt mice without systemic M-CSF treatment. We further observed an anabolic effect of M-CSF application resulting in increased trabecular thickness compared to wt animals without additional M-CSF application. Systemic M-CSF application did not alter biomechanical properties in WT mice. The impact of M-CSF application in a mouse model of femoral osteotomy was oppositional to what we were expecting. While M-CSF application had a distinct anabolic effect on callus size as well as trabecular thickness, this on bottom line did not improve biomechanical properties. We hypothesize that in addition to the well-recognized negative effects of M-CSF on osteoclast numbers this seems to further downstream cause a lack of feedback on osteoblasts. Ultimately, continuous M-CSF application in the absence of co-stimulatory signals (e.g. RANKL) might overstimulate the hematopoietic linage in favor of tissue macrophages instead of osteoclasts.

Olive polyphenols attenuate TNF-α-stimulated M-CSF and IL-6 synthesis in osteoblasts: Suppression of Akt and p44/p42 MAP kinase signaling pathways

BACKGROUND

Olive oil polyphenols, which possess cytoprotective activities like anti-oxidant and anti-inflammatory effects, could modulate osteoblast functions. The aim of this study is to elucidate the effects and the underlying mechanisms of hydroxytyrosol and oleuropein on the tumor necrosis factor-α (TNF-α)-induced macrophage colony-stimulating factor (M-CSF) and interleukin-6 (IL-6) synthesis in osteoblasts.

METHODS

Osteoblast-like MC3T3-E1 cells were pretreated with hydroxytyrosol, oleuropein, deguelin, PD98059 or wedelolactone, and then stimulated by TNF-α. The levels of M-CSF and IL-6 in the conditioned medium were determined with ELISA. The mRNA expression levels of M-CSF or IL-6 were determined with real-time RT-PCR. The phosphorylation levels of Akt, p44/p42 mitogen-activated protein (MAP) kinase or NF-κB in the cell lysates were determined with Western blot analysis.

RESULTS

Hydroxytyrosol and oleuropein attenuated the TNF-α-stimulated M-CSF release. Deguelin, an inhibitor of Akt, significantly suppressed the TNF-α-stimulated M-CSF release, which failed to be affected by the MEK1/2 inhibitor PD98059 or the IκB inhibitor wedelolactone. Hydroxytyrosol and oleuropein suppressed the TNF-α-induced phosphorylation of Akt and p44/p42 MAP kinase. Hydroxytyrosol and oleuropein attenuated the TNF-α-stimulated IL-6 release. Hydroxytyrosol suppressed the TNF-α-induced mRNA expressions of M-CSF and IL-6. Hydroxytyrosol or oleuropein failed to affect the cell viability.

CONCLUSION

Our present findings strongly suggest that olive oil polyphenols hydroxytyrosol and oleuropein down-regulates TNF-α signaling at the points upstream of Akt and p44/p42 MAP kinase in osteoblasts, leading to the attenuation of M-CSF and IL-6 synthesis.

Overexpression of macrophage-colony stimulating factor-1 receptor as a prognostic factor for survival in cancer: A systematic review and meta-analysis

BACKGROUND

The relation between the expression of macrophage-colony stimulating factor-1 receptor (CSF-1R) and prognosis of cancer patients has been evaluated in multiple studies, but the results remain controversial. We, therefore, performed a meta-analysis and systematic review to figure out the role of CSF-1R in the prognosis of patients with cancer.

METHODS

Several databases were searched, including Web of Science, PubMed, and EMBASE. All human studies were published as full text. The Newcastle-Ottawa risk of bias scale was applied to evaluate the research. We extracted hazard ratios (HRs) with 95% confidence interval (95% CI) which assessed progression-free survival (PFS) and overall survival (OS) in order to assess the impacts of CSF-1R on the prognosis of cancer patients.

RESULTS

A total of 12 citations were identified, with studies including 2260 patients in different cancer types that met the eligibility criteria. It was suggested in a pooled analysis that the over-expression of CSF-1R was significantly related to worse PFS (HR: 1.68; P < .001, 1.25-2.10, 95% CI) and also poorer OS (HR=1.28; P < .001, 1.03-1.54, 95% CI). Analysis in subgroups indicated over-expressed CSF-1R was significantly associated with worse OS in hematological malignancy (HR = 2.29; P < .001, 1.49-3.09, 95% CI; model of fixed-effects; I2 = 0.0%, P < .001). Sensitivity analysis suggested that there was no study influencing the stability of the results.

CONCLUSIONS

The overexpression of CSF-1R was significantly predictive of worse prognosis in those who suffer from different kinds of malignancies, particularly in hematological malignancy, which indicates that it might be a potential biomarker of prognosis in cancer survival and a potential molecular target in the treatment of malignant tumors.

Epigenetics and Communication Mechanisms in Microglia Activation with a View on Technological Approaches

Microglial cells, the immune cells of the central nervous system (CNS), play a crucial role for the proper brain development and function and in CNS homeostasis. While in physiological conditions, microglia continuously check the state of brain parenchyma, in pathological conditions, microglia can show different activated phenotypes: In the early phases, microglia acquire the M2 phenotype, increasing phagocytosis and releasing neurotrophic and neuroprotective factors. In advanced phases, they acquire the M1 phenotype, becoming neurotoxic and contributing to neurodegeneration. Underlying this phenotypic change, there is a switch in the expression of specific microglial genes, in turn modulated by epigenetic changes, such as DNA methylation, histones post-translational modifications and activity of miRNAs. New roles are attributed to microglial cells, including specific communication with neurons, both through direct cell–cell contact and by release of many different molecules, either directly or indirectly, through extracellular vesicles. In this review, recent findings on the bidirectional interaction between neurons and microglia, in both physiological and pathological conditions, are highlighted, with a focus on the complex field of microglia immunomodulation through epigenetic mechanisms and/or released factors. In addition, advanced technologies used to study these mechanisms, such as microfluidic, 3D culture and in vivo imaging, are presented.

Osteoblast-Osteoclast Communication and Bone Homeostasis

Bone remodeling is tightly regulated by a cross-talk between bone-forming osteoblasts and bone-resorbing osteoclasts. Osteoblasts and osteoclasts communicate with each other to regulate cellular behavior, survival and differentiation through direct cell-to-cell contact or through secretory proteins. A direct interaction between osteoblasts and osteoclasts allows bidirectional transduction of activation signals through EFNB2-EPHB4, FASL-FAS or SEMA3A-NRP1, regulating differentiation and survival of osteoblasts or osteoclasts. Alternatively, osteoblasts produce a range of different secretory molecules, including M-CSF, RANKL/OPG, WNT5A, and WNT16, that promote or suppress osteoclast differentiation and development. Osteoclasts also influence osteoblast formation and differentiation through secretion of soluble factors, including S1P, SEMA4D, CTHRC1 and C3. Here we review the current knowledge regarding membrane bound- and soluble factors governing cross-talk between osteoblasts and osteoclasts.

BTK Inhibition Impairs the Innate Response Against Fungal Infection in Patients With Chronic Lymphocytic Leukemia

Infections represent a cause of morbidity and mortality in patients affected by chronic lymphocytic leukemia (CLL). Introduction of new drugs in CLL clinical practice has showed impressive efficacy, in particular those targeting BTK. Among the consistent clinical data, an increasing number of reports describing the occurrence of unexpected opportunistic fungal infections has been reported during treatment with ibrutinib in the first 6 months of treatment. The reason underlying manifestations of invasive fungal infections in patients treated with ibrutinib is still under investigation. Our study aimed to understand the impact of BTK inhibition on immune response to fungal infection mediated by macrophages and CD14+ monocytic population obtained from CLL patients. Exposure to ibrutinib and acalabrutinib reduced signaling pathways activated by Aspergillus fumigatus determining an exacerbation of an immunosuppressive signature, a reduction of phagocytosis and a significant deficit in the secretion of inflammatory cytokines either in macrophages and monocytes isolated from CLL patients and healthy donors. These effects lead to a failure in completely counteracting conidia germination. In addition we investigated the biological effects of ibrutinib on monocyte counterpart in patients who were undergoing therapy. A significant impairment in cytokine secretion and a deficit of phagocytosis in circulating monocytes were detected after 3 months of treatment. Thus, our results uncover modifications in the innate response in CLL patients induced by ibrutinib that may impair the immunological response to fungal infection.

KEYPOINTS

•BTK inhibition affects a productive immune response of CLL-associated macrophages (NLC) during Aspergillus fumigatus infection.•Reduction of TNF-α secretion and phagocytosis are detected in monocytes isolated from CLL patients during ibrutinib therapy.

The M-CSF receptor in osteoclasts and beyond

Colony-stimulating factor 1 receptor (CSF1R, also known as c-FMS) is a receptor tyrosine kinase. Macrophage colony-stimulating factor (M-CSF) and IL-34 are ligands of CSF1R. CSF1R-mediated signaling is crucial for the survival, function, proliferation, and differentiation of myeloid lineage cells, including osteoclasts, monocytes/macrophages, microglia, Langerhans cells in the skin, and Paneth cells in the intestine. CSF1R also plays an important role in oocytes and trophoblastic cells in the female reproductive tract and in the maintenance and maturation of neural progenitor cells. Given that CSF1R is expressed in a wide range of myeloid cells, altered CSF1R signaling is implicated in inflammatory, neoplastic, and neurodegenerative diseases. Inhibiting CSF1R signaling through an inhibitory anti-CSF1R antibody or small molecule inhibitors that target the kinase activity of CSF1R has thus been a promising therapeutic strategy for those diseases. In this review, we cover the recent progress in our understanding of the various roles of CSF1R in osteoclasts and other myeloid cells, highlighting the therapeutic applications of CSF1R inhibitors in disease conditions.

Drugs directed at a key signaling receptor involved in breaking down bone tissue could help treat diseases marked by pathological bone loss and destruction. In a review article, Kyung-Hyun Park-Min and colleagues from the Hospital for Special Surgery in New York, USA, discuss the essential roles played by the colony-stimulating factor 1 receptor (CSF1R) protein in the survival, function, proliferation and differentiation of myeloid lineage stem cells in the bone marrow, including bone-resorbing osteoclasts. They explore the links between the CSF1R-mediated signaling pathway and diseases such as cancer and neurodegeneration. The authors largely focus on bone conditions, highlighting mouse studies in which CSF1R-blocking drugs were shown to ameliorate bone loss and inflammatory symptoms in models of arthritis, osteoporosis and metastatic cancer. Clinical trials are ongoing to test therapeutic applications.

Airway Epithelial Cell-Derived Colony Stimulating Factor-1 Promotes Allergen Sensitization

Airway epithelial cells (AECs) secrete innate immune cytokines that regulate adaptive immune effector cells. In allergen-sensitized humans and mice, the airway and alveolar microenvironment is enriched with colony stimulating factor-1 (CSF1) in response to allergen exposure. In this study we found that AEC-derived CSF1 had a critical role in the production of allergen reactive-IgE production. Furthermore, spatiotemporally secreted CSF1 regulated the recruitment of alveolar dendritic cells (DCs) and enhanced the migration of conventional DC2s (cDC2s) to the draining lymph node in an interferon regulatory factor 4 (IRF4)-dependent manner. CSF1 selectively upregulated the expression of the chemokine receptor CCR7 on the CSF1R⁺ cDC2, but not the cDC1, population in response to allergen stimuli. Our data describe the functional specification of CSF1-dependent DC subsets that link the innate and adaptive immune responses in T helper 2 (Th2) cell-mediated allergic lung inflammation.

Niche-induced extramedullary hematopoiesis in the spleen is regulated by the transcription factor Tlx1

Extramedullary hematopoiesis (EMH) in postnatal life is a pathological process in which the differentiation of hematopoietic stem/progenitor cells (HSPCs) occurs outside the bone marrow (BM) to respond to hematopoietic emergencies. The spleen is a major site for EMH; however, the cellular and molecular nature of the stromal cell components supporting HSPC maintenance, the niche for EMH in the spleen remain poorly understood compared to the growing understanding of the BM niche at the steady-state as well as in emergency hematopoiesis. In the present study, we demonstrate that mesenchymal progenitor-like cells expressing Tlx1, an essential transcription factor for spleen organogenesis, and selectively localized in the perifollicular region of the red pulp of the spleen, are a major source of HSPC niche factors. Consistently, overexpression of Tlx1 in situ induces EMH, which is associated with mobilization of HSPC into the circulation and their recruitment into the spleen where they proliferate and differentiate. The alterations in the splenic microenvironment induced by Tlx1 overexpression in situ phenocopy lipopolysaccharide (LPS)-induced EMH, and the conditional loss of Tlx1 abolished LPS-induced splenic EMH. These findings indicate that activation of Tlx1 expression in the postnatal splenic mesenchymal cells is critical for the development of splenic EMH.

Autonomous Cell Migration to CSF1 Sources via a Synthetic Protein-Based System

Inflammatory lesions, often seen in diseases such as rheumatoid arthritis, atherosclerosis and cancer, feature an acidic (i.e., low pH) microenvironment rampant with cytokines, such as CSF1. For potential therapeutic intervention targeted at these CSF1 sources, we have assembled a system of four proteins inside a cell (i.e., HEK293) that initially had no natural CSF1-seeking ability. This system included a newly engineered CSF1 chimera receptor (named CSF1Rchi), the previously engineered Ca²⁺ activated RhoA (i.e., CaRQ), vesicular stomatitis virus glycoprotein G (VSVG) and thymidine kinase (TK). The binding of CSF1 to the CSF1Rchi generated a Ca²⁺ signal that activated CaRQ-mediated cellular blebbing, allowing autonomous cell migration toward the CSF1 source. Next, the VSVG protein allowed these engineered cells to fuse with the CSF1 source cells, upon low pH induction. Finally, these cells underwent death postganciclovir treatment, via the TK suicide mechanism. Hence, this protein system could potentially serve as the basis of engineering a cell to target inflammatory lesions in diseases featuring a microenvironment with high levels of CSF1 and low pH.

Modeling the Role of Lanthionine Synthetase C-Like 2 (LANCL2) in the Modulation of Immune Responses to Helicobacter pylori Infection

Immune responses to Helicobacter pylori are orchestrated through complex balances of host-bacterial interactions, including inflammatory and regulatory immune responses across scales that can lead to the development of the gastric disease or the promotion of beneficial systemic effects. While inflammation in response to the bacterium has been reasonably characterized, the regulatory pathways that contribute to preventing inflammatory events during H. pylori infection are incompletely understood. To aid in this effort, we have generated a computational model incorporating recent developments in the understanding of H. pylori-host interactions. Sensitivity analysis of this model reveals that a regulatory macrophage population is critical in maintaining high H. pylori colonization without the generation of an inflammatory response. To address how this myeloid cell subset arises, we developed a second model describing an intracellular signaling network for the differentiation of macrophages. Modeling studies predicted that LANCL2 is a central regulator of inflammatory and effector pathways and its activation promotes regulatory responses characterized by IL-10 production while suppressing effector responses. The predicted impairment of regulatory macrophage differentiation by the loss of LANCL2 was simulated based on multiscale linkages between the tissue-level gastric mucosa and the intracellular models. The simulated deletion of LANCL2 resulted in a greater clearance of H. pylori, but also greater IFNγ responses and damage to the epithelium. The model predictions were validated within a mouse model of H. pylori colonization in wild-type (WT), LANCL2 whole body KO and myeloid-specific LANCL2-/- (LANCL2^Myeloid) mice, which displayed similar decreases in H. pylori burden, CX3CR1+ IL-10-producing macrophages, and type 1 regulatory (Tr1) T cells. This study shows the importance of LANCL2 in the induction of regulatory responses in macrophages and T cells during H. pylori infection.

Early risk prognosis of free-flap transplant failure by quantitation of the macrophage colony-stimulating factor in patient plasma using 2-dimensional liquid-chromatography multiple reaction monitoring-mass spectrometry

Although great success of microvascular free-flap transplantation surgery has been achieved in recent years, between 1.5% and 15% of flaps are still lost due to vascular occlusion. The clinical challenge remains to salvage a transplant in the case of vascular complications. Since flap loss is devastating for the patient, it is of utmost importance to detect signs of complications or of conspicuities as soon as possible. Rescue success rates highly depend on early revision. In this study, we collected blood samples during transplantation surgery from either the contributory artery or the effluent vein of the flap and applied a targeted mass spectrometry-based approach to quantify 24 acute phase proteins, cytokines, and growth factors in 63 plasma samples from 21 hospitalized patients, generating a dataset with 9450 protein concentration values. Biostatistical analyses of the targeted plasma protein concentrations in all 63 plasma samples showed that venous concentrations of macrophage colony-stimulating factor (M-CSF) provided the highest accuracy for discriminating patients with either clinical conspicuities or complications from control individuals. Using 21.33 ng/mL of M-CSF as the diagnostic threshold when analyzing venous blood plasma samples, the assay obtained a sensitivity of 0.93 and a specificity of 0.85 with an area under the curve value of 0.902 in the receiver operating characteristic analysis. Overall, our results indicate that M-CSF is a potential molecular marker for early risk prognosis of free-flap transplant failure.

Interleukin-33 stimulates GM-CSF and M-CSF production by human endothelial cells

Interleukin (IL)-33, a member of the IL-1 family of cytokines, is involved in various inflammatory conditions targeting amongst other cells the endothelium. Besides regulating the maturation and functions of myeloid cells, granulocyte macrophage-colony stimulating factor (GM-CSF) and macrophage-CSF (M-CSF) have been shown to play a role in such pathologies too. It was the aim of our study to investigate a possible influence of IL-33 on GM-CSF and M-CSF production by human endothelial cells. IL-33, but not IL-18 or IL-37, stimulated GM-CSF and M-CSF mRNA expression and protein production by human umbilical vein endothelial cells (HUVECs) and human coronary artery ECs (HCAECs) through the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway in an IL-1-independent way. This effect was inhibited by the soluble form of ST2 (sST2), which is known to act as a decoy receptor for IL-33. The 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor fluvastatin could also be shown to moderately reduce the IL-33-mediated effect on M-CSF, but not on GM-CSF expression. In addition, IL-33, IL-1β, GM-CSF and M-CSF were detected in endothelial cells of human carotid atherosclerotic plaques using immunofluorescence. Upregulation of GM-CSF and M-CSF production by human endothelial cells, an effect that appears to be mediated by NF-κB and to be independent of IL-1, may be an additional mechanism through which IL-33 contributes to inflammatory activation of the vessel wall.

Role of the colony-stimulating factor (CSF)/CSF-1 receptor axis in cancer

Cancer cells employ a variety of mechanisms to evade apoptosis and senescence. Pre-eminent among these is the aberrant co-expression of growth factors and their ligands, forming an autocrine growth loop that promotes tumour formation and progression. One growth loop whose transforming potential has been repeatedly demonstrated is the CSF-1/CSF-1R axis. Expression of CSF-1 and/or CSF-1R has been documented in a number of human malignancies, including breast, prostate and ovarian cancer and classical Hodgkin's lymphoma (cHL). This review summarizes the large body of work undertaken to study the role of this cytokine receptor system in malignant transformation. These studies have attributed a key role to the CSF-1/CSF-1R axis in supporting tumour cell survival, proliferation and enhanced motility. Moreover, increasing evidence implicates paracrine interactions between CSF-1 and its receptor in defining a tumour-permissive and immunosuppressive tumour-associated stroma. Against this background, we briefly consider the prospects for therapeutic targeting of this system in malignant disease.

Control of CSF-1 induced inflammation in teleost fish by a soluble form of the CSF-1 receptor

The colony-stimulating factor-1 (CSF-1) is the principal regulator of the survival, proliferation, differentiation, and function of macrophages and their precursors, and has been shown to play a role in the etiology of inflammation. We recently identified a novel mechanism for the control of CSF-1 activity in teleost fish, through the production of an inhibitory soluble form of the CSF-1 receptor (sCSF-1R). Primary goldfish kidney macrophages selectively expressed sCSF-1R during the senescence phase, which corresponds to a defined stage of in vitro culture development where inhibition of macrophage proliferation and apoptotic cell death are prominent. In contrast, primary macrophage cultures undergoing active proliferation displayed low levels of sCSF-1R expression. Addition of purified recombinant sCSF-1R to developing primary macrophage cultures leads to a dose-dependent decrease in macrophage proliferation and inhibits macrophage antimicrobial functions including chemotaxis, phagocytosis, and production of reactive oxygen intermediates. Using a goldfish in vivo model of self-resolving peritonitis, we found that sCSF-1R plays a role in the inhibition of inflammation, following an initial acute phase of antimicrobial responses within an inflammatory site. Soluble CSF-1R inhibits pro-inflammatory cytokine production, inhibits leukocyte recruitment to the inflammatory site and decreases ROS production in a dose-dependent manner. This sCSF-1R-dependent regulation of inflammation appears to be an elegant mechanism for the control of macrophage numbers at inflammatory sites of lower vertebrates. Overall, our results provide new insights into the evolutionary origins of the CSF-1 immune regulatory axis.

Exploring the relationship of macrophage colony-stimulating factor levels on neuroaxonal metabolism and cognition during chronic human immunodeficiency virus infection

Macrophage colony-stimulating factor (M-CSF) promotes macrophage differentiation, increases susceptibility of macrophages to viral infection, and enhances human immunodeficiency virus (HIV) replication in infected macrophages. Given the current model of HIV neuropathogenesis, which involves monocyte trafficking into the central nervous system, immune factors linked with macrophage maturation and survival may be associated with cognitive decline (measured by neuropsychological z-score [NPZ-8] or Memorial Sloan-Kettering [MSK] score) and alterations in a marker of neuronal integrity, N-acetylaspartate (NAA). Fifty-four chronically infected HIV+ subjects underwent neuropsychological assessment, magnetic resonance spectroscopic imaging, and quantification of M-CSF in plasma and cerebrospinal fluid (CSF) at baseline. Thirty-nine of those subjects underwent further examination at 3 and 10 months after initiation of combination antiretroviral therapy (ART) regimens. Within 3 months of therapy use, CSF M-CSF and viral RNA levels were reduced, whereas NAA concentrations in many brain regions were increased. Neither baseline levels nor the change in M-CSF levels had the ability to predict changes in NAA levels observed after 10 months of combination ART use. At study entry those with the lowest M-CSF levels in the CSF had the least cognitive impairment (NPZ-8). Those who had higher baseline CSF M-CSF levels and exhibited larger decreases in M-CSF after therapy, tended to have greater cognitive improvement after 10 months. Increased prevalence of M-CSF in the setting of HIV infection could contribute to neuronal injury and may be predictive of cognitive impairment.

Biological therapy of bone defects: the immunology of bone allo-transplantation

IMPORTANCE OF THE FIELD

Bone is one of the most transplanted tissues worldwide. Autograft is the ideal bone graft but is not widely used because of donor site morbidity and restricted availability. Allograft is easily accessible but can transmit infections and elicit an immune response.

AREAS COVERED IN THIS REVIEW

This review identifies all in vitro and in vivo evidence of immune responses following bone transplantation and highlights methods of improving host tolerance to bone allotransplantation.

WHAT THE READER WILL GAIN

In humans, the presence of anti-HLA specific antibodies against freeze-dried and fresh-frozen bone allografts has been demonstrated. Fresh-frozen bone allograft can still generate immune reactions whilst freeze-dried bone allografts present with less immunogenicity but have less structural integrity. This immune response can have an adverse effect on the graft's incorporation and increase the incidence of rejection. Decreasing the immune reaction against the allograft by lowering the immunogenic load of the graft or lowering the host immune response, would result in improved bone incorporation.

TAKE HOME MESSAGE

It is essential that the complex biological processes related to bone immunogenicity are understood, since this may allow the development of safer and more successful ways of controlling the outcome of bone allografting.

Pro- and anti-inflammatory control of M-CSF-mediated macrophage differentiation

Macrophages play a key role in inflammation, tissue regeneration and tolerance. Their differentiation is regulated by tissue cells derived CSF-1 (M-CSF). The ability of macrophages to use autocrine M-CSF to control their differentiation and function remained controversial. In this study we investigated the regulation of M-CSF production by Th1 and Th2 cytokines (IFN-γ and IL-4) and tolerogenic stimuli - glucocorticoid dexamethasone in primary human monocyte derived macrophages. We show that IFN-γ and IL-4 efficiently induce production of M-CSF while glucocorticoid inhibited it in a dose dependent manner. Since glucocorticoid inhibits production of inflammatory cytokines we tested whether this effect is a result of inhibited M-CSF production. We showed that exogenous M-CSF rescues the ability of glucocorticoid-treated macrophages to produce TNF and IL-6 in response to LPS. These data indicate that glucocorticoid-treated macrophages retain the ability to respond to M-CSF. Analyzing the mechanism of this responsiveness, we showed that dexamethasone up-regulates surface expression of M-CSF receptor - CSF-1R. We conclude that the ability of macrophages to produce M-CSF secures macrophage differentiation under Th1 and Th2 conditions if tissue cells are unable to supply enough M-CSF. Increased surface expression of CSF-1R in tolerogenic conditions guarantees response to minute amounts of exogenous M-CSF.

Functional alterations of proinflammatory monocytes by T regulatory cells: implications for the prevention and reversal of type 1 diabetes

The onset and development of type 1 diabetes (T1D) occurs in genetically predisposed individuals, and is attributed to autoimmune destruction of pancreatic beta-cells involving a multitude of immune mechanisms. Defects in immune regulation may play a central role in T1D, involving impaired function and communication of both myeloid and lymphoid cells of the innate and adaptive immune compartments. Dendritic cells and regulatory T (Treg) cells are part of this network, which seem to be hampered in their quest to control and regulate tissue-destructive autoimmunity. Recent studies have shown that in vivo activated CD16- blood monocytes exhibiting proinflammatory features are present in diabetic subjects. These monocytes may govern T cell-mediated immune responses towards the development of tissue-destructive Th1 and Th17 subtypes, and give rise to inflammatory macrophages in tissues. Differential effects of cytokines IFN-gamma and IL-4 in the development of inflammatory macrophages, and the distinct developmental pathways of proinflammatory or tissue-repair-associated monocytes suggest that controlling the activity of these monocytes could be part of an immune intervention strategy to prevent T1D. Similarly, strategies to target autoantigens to immature, steady-state dendritic cells could guide the immune response away from Th1 and Th17 immune effectors. This review examines potential approaches to this goal by manipulation of myeloid and lymphoid cell regulatory networks in T1D.

Development of disseminated histiocytic sarcoma in a patient with autoimmune lymphoproliferative syndrome and associated Rosai-Dorfman disease

Patients with autoimmune lymphoproliferative syndrome (ALPS) have defective lymphocyte apoptosis with increased risk for lymphoid malignancies. Herein, we report a patient with ALPS who developed histiocytic sarcoma in a background of sinus histiocytosis and massive lymphadenopathy or Rosai- Dorfman disease. This patient had documented ALPS type Ia with a germline missense mutation in exon 9 of the TNFRSF6 gene (973 A>T, D244V) encoding Fas (CD95/Apo-1). He presented at 10 months with hepatosplenomegaly and autoimmune hemolytic anemia and was diagnosed with ALPS. At the age of 6 (1/2) years, he developed classic Hodgkin lymphoma which was treated using standard chemotherapy. Two years later, a biopsy of a positron emission tomography-positive axillary node showed features of ALPS and focal involvement by sinus histiocytosis and massive lymphadenopathy. Thereafter, the patient continued to have continued lymphadenopathy and progressive splenomegaly, leading to exploratory surgery at the age of 13 years for suspicion of lymphoma. Para-abdominal nodes revealed sheets of malignant- looking histiocytes with increased mitotic activity and areas of necrosis, indicative of histiocytic sarcoma. Spleen and lymph nodes also showed involvement by Rosai-Dorfman disease. Both components had an identical phenotype of S-100+/CD68+/ CD163+. The occurrence of malignancies involving 2 separate hematopoietic lineages in ALPS has not been reported earlier. Given the central role of defective Fas signaling in ALPS, histiocytes may be yet another lineage at risk for neoplastic transformation secondary to a block in apoptosis.

Targeting extracellular signal-regulated kinase (ERK) signaling has therapeutic implications for inflammatory osteolysis

The extracellular signal-regulated kinase 1/2 (ERK) pathway, part of the mitogen-activated protein kinase (MAPK) family, is well-known for its role in cell differentiation and proliferation. In the context of osteoclastogenesis, macrophage colony stimulating factor (M-CSF) is an upstream activator of ERK signals for the survival of osteoclast precursors prior to their differentiation into multinucleated osteoclasts. In this study, we demonstrate by using both in vivo and in vitro models that the ERK signaling pathway involves an inflammatory response of various cells mediating osteolysis. Osteoblasts exhibit innate immune response by expressing M-CSF in response to lipopolysaccharide (LPS). LPS induced M-CSF expression is mediated by ERK. The inhibition of ERK signaling attenuated the inflammatory response to LPS both in vivo and in vitro. Thus, the ERK pathway may be a potentially important therapeutic target in the treatment of inflammatory osteolysis.

LDL receptor-related protein 1: unique tissue-specific functions revealed by selective gene knockout studies

The LDL receptor-related protein (originally called LRP, but now referred to as LRP1) is a large endocytic receptor that is widely expressed in several tissues. LRP1 is a member of the LDL receptor family that plays diverse roles in various biological processes including lipoprotein metabolism, degradation of proteases, activation of lysosomal enzymes, and cellular entry of bacterial toxins and viruses. Deletion of the LRP1 gene leads to lethality in mice, revealing a critical, but as of yet, undefined role in development. Tissue-specific gene deletion studies reveal an important contribution of LRP1 in the vasculature, central nervous system, macrophages, and adipocytes. Three important properties of LRP1 dictate its diverse role in physiology: 1) its ability to recognize more than 30 distinct ligands, 2) its ability to bind a large number of cytoplasmic adaptor proteins via determinants located on its cytoplasmic domain in a phosphorylation-specific manner, and 3) its ability to associate with and modulate the activity of other transmembrane receptors such as integrins and receptor tyrosine kinases.

Macrophage colony-stimulating factor in the pathogenesis of HIV infection: potential target for therapeutic intervention

Macrophage colony stimulating factor (M-CSF) appears to play a major role in promoting and maintaining reservoirs of human immunodeficiency virus type 1 (HIV-1) in infected individuals. HIV-1 infection induces production of M-CSF by macrophages, which in turn promotes further infection of macrophages via increases in CD4 and CCR5 receptors, as well as increases in virus gene expression. M-CSF promotes the ontogeny and survival of macrophages, contributing to both the number and longevity of these infected cells. M-CSF dysregulation promotes the differentiation of monocytes toward macrophages and osteoclasts and at the same time may inhibit differentiation toward dendritic cells, resulting in immune impairment. The potential role of M-CSF in HIV-associated end organ diseases including HIV-associated dementia, HIV-associated nephropathy, and osteoporosis is discussed. This review emphasizes the need for developing M-CSF antagonists for treatment of HIV-1-infected patients.

Cell surface colony-stimulating factor 1 can be cleaved by TNF-alpha converting enzyme or endocytosed in a clathrin-dependent manner

CSF-1 is a hemopoietic growth factor, which plays an essential role in macrophage and osteoclast development. Alternative splice variants of CSF-1 are synthesized as soluble or membrane-anchored molecules, although membrane CSF-1 (mCSF-1) can be cleaved from the cell membrane to become soluble CSF-1. The activities involved in this proteolytic processing, also referred to as ectodomain shedding, remain poorly characterized. In the present study, we examined the properties of the mCSF-1 sheddase in cell-based assays. Shedding of mCSF-1 was up-regulated by phorbol ester treatment and was inhibited by the metalloprotease inhibitors GM6001 and tissue inhibitor of metalloproteases 3. Moreover, the stimulated shedding of mCSF-1 was abrogated in fibroblasts lacking the TNF-alpha converting enzyme (TACE, also known as a disintegrin and metalloprotease 17) and was rescued by expression of wild-type TACE in these cells, strongly suggesting that the stimulated shedding is TACE dependent. Additionally, we observed that mCSF-1 is predominantly localized to intracellular membrane compartments and is efficiently internalized in a clathrin-dependent manner. These results indicate that the local availability of mCSF-1 is actively regulated by ectodomain shedding and endocytosis. This mechanism may have important implications for the development and survival of monocyte lineage cells.

Macrophage colony stimulating factor expression in human cardiac cells is upregulated by tumor necrosis factor-alpha via an NF-kappaB dependent mechanism

INTRODUCTION

Macrophage colony stimulating factor (M-CSF) is a key factor for monocyte and macrophage survival and proliferation. M-CSF has been implicated in cardiac healing and repair after myocardial infarction.

METHODS AND RESULTS

We show by immunohistochemistry and Western blotting analysis that M-CSF protein is present in human heart tissue. Cultured human adult cardiac myocytes (HACM) and human adult cardiac fibroblasts (HACF) isolated from human myocardial tissue constitutively express M-CSF. When HACM and HACF were treated with tumor necrosis factor-alpha (TNF-alpha) M-CSF protein production and M-CSF mRNA expression, determined by ELISA or by using RT-PCR, respectively, was significantly increased. To determine a possible role of nuclear factor kappaB (NF-kappaB) and activating protein 1 (AP-1) in M-CSF regulation, blockers to both pathways and an adenovirus overexpressing a dominant negative (dn) form of IkappaB kinase 2 (IKK2) were used. Only the NF-kappaB blocker dimethylfumarate and the dn IKK2, but not januskinase inhibitor-1 (JNK-I), were able to block the TNF-alpha-induced increase in M-CSF production in these cells, suggesting that the induction of M-CSF through TNF-alpha is mainly dependent on the activation of the NF-kappaB pathway. The monocyte activation marker CD11b was significantly increased after incubating U937 cells with conditioned medium from HACM or HACF as determined by FACS analysis.

CONCLUSIONS

Our in vitro data taken together with our immunohistochemistry data suggest that human cardiac cells constitutively express M-CSF. This expression of M-CSF in the human heart and its upregulation by TNF-alpha might contribute to monocyte and macrophage survival and differentiation.

Macrophage-colony stimulating factor enhances MHC-restricted presentation of exogenous antigen in dendritic cells

Previous studies have shown that dendritic cells (DCs) can phagocytize, process and present a microencapsulated form of ovalbumin (OVA) in the context of class I MHC as well as class II MHC. In the present study, we examined the effects of recombinant human macrophage-colony stimulating factor (M-CSF) on the MHC-restricted presentation of microencapsulated OVA by DCs. Two types of DCs were generated from mouse bone marrow (BM) cells, one type with granulocyte/macrophage-colony stimulating factor (GM-CSF) alone, the other type with GM-CSF and interleukin (IL)-4. Pretreatment with M-CSF significantly enhanced both class I MHC and class II MHC-restricted presentation of exogenous OVA by both types of DCs. The enhancing activity of M-CSF on antigen presentation was more potent in DCs generated with GM-CSF alone compared to DCs generated with both GM-CSF and IL-4. Pretreatment of the DCs with M-CSF did not increase phagocytic activity or total level of expression of class I MHC (H-2K(b)) molecules, but increased expression of OVA peptide-H-2K(b) complexes upon phagocytosis of microencapsulated OVA. These results demonstrate that M-CSF increases intracellular processing events of phagocytized antigen in DCs.

A mechanism of transcriptional regulation of the CSF-1 gene by interferon-gamma

Interferon (IFN)-gamma exerts multiple functions including antiviral, anti-proliferative and immunomodulatory activities, which are mediated through the JAK-STAT pathway. We observed that IFN-gamma significantly increases the production of colony stimulating factor-1 (CSF-1) by a human lung carcinoma cell line, A549. To gain insight into this mechanism, we determined the unknown nucleotide sequences of 5'-flanking region of human CSF-1 gene. About 60 bases upstream of the transcription start site of the CSF-1 gene contains a possible gamma interferon activated site (GAS), TTCCCATAA. The promoter assay and the electrophoretic mobility gel shift assay revealed that IFN-gamma stimulates transcription of the CSF-1 gene through this sequence, which binds STAT1.

Elevated gelatinase activity in pulmonary alveolar proteinosis: role of macrophage-colony stimulating factor

Pulmonary alveolar proteinosis (PAP) is an anti-granulocyte macrophage-colony stimulating factor (GM-CSF) autoimmune disease resulting in the accumulation of phospholipids in the alveoli. GM-CSF knockout (KO) mice exhibit a strikingly similar lung pathology to patients with PAP. The lack of functionally active GM-CSF correlates with highly elevated concentrations of M-CSF in the lungs of PAP patients and GM-CSF KO mice. M-CSF has been associated with alternative macrophage activation, and in models of pulmonary fibrosis, M-CSF also contributes to tissue resorption and fibrosis. Matrix metalloproteinase-2 (MMP-2) and MMP-9 have been implicated in extracellular matrix degradation in animal models of fibrosis and asthma. We show for the first time that the lungs of PAP patients contain highly elevated levels of MMP-2 and MMP-9. PAP broncholaveolar lavage (BAL) cells but not bronchial epithelial cells expressed increased MMP-2 and MMP-9 mRNA relative to healthy controls. Both MMPs were detectable as pro and active proteins by gelatin zymography; and by fluorometric global assay, PAP-MMP activity was elevated. BAL cells/fluids from GM-CSF KO mice also demonstrated significantly elevated MMP-2 and MMP-9 gene expression, protein, and activity. Finally, PAP patients undergoing GM-CSF therapy exhibited significantly reduced MMPs and M-CSF. These data suggest that in the absence of GM-CSF, excess M-CSF in PAP may redirect alveolar macrophage activation, thus potentially contributing to elevated MMP expression in the lung.

Histologic features of sinus histiocytosis with massive lymphadenopathy in patients with autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is an inherited disorder associated with defects in Fas-mediated apoptosis, characterized most often by childhood onset of lymphadenopathy, splenomegaly, hypergammaglobulinemia, and autoimmune phenomena. Children with sinus histiocytosis with massive lymphadenopathy (SHML) have a somewhat similar clinical phenotype in which prominent adenopathy also is associated with hypergammaglobulinemia, and autoimmune phenomena are reported in 10-15% of cases. We observed histopathological features of SHML in the lymph nodes of some of our ALPS patients, further suggesting an association between these two disorders. We, thus, reviewed the lymph nodes from 44 patients ALPS type Ia, all of whom were confirmed to have germline mutations in the TNFRSF6 gene encoding Fas (CD95/Apo-1). Eighteen of 44 (41%) patients had a histiocytic proliferation resembling SHML. The affected patients included 15 males and 3 females ranging in age from 11 months to 30 years at the time of the LN biopsy. The lymph nodes contained S-100+ histiocytes with characteristic nuclear features of SHML, and showed evidence of emperipolesis in both hematoxylin and eosin (H and E) and immunostained sections. The extent of the histiocytic proliferation was variable, being confluent in 2 cases, multifocal in 13, and only evident as isolated SHML-type histiocytes in 3. In lymph nodes without confluent SHML changes, increased numbers of CD3+CD4-CD8+ (double negative) alphabeta T-cells, also negative for CD45RO, a feature of ALPS, could be identified in the paracortex. Furthermore, because SHML shares many clinical features with ALPS, we sought evidence of ALPS in sporadic SHML. We attempted to sequence TNFRSF6 DNA from archived tissue of 14 cases of Rosai-Dorfman disease. Full sequencing of the gene was successful in 4 of the cases; no mutations were identified. Nevertheless, our observations suggest that histologic features of SHML are part of the pathologic spectrum of ALPS type Ia. It remains to be determined if some cases of apparently sporadic SHML may be associated with heritable defects in Fas-mediated apoptosis.

Expression of mRNA and protein of macrophage colony-stimulating factor and its receptor in human follicular luteinized granulosa cells

OBJECTIVE

To evaluate the concentration of macrophage colony-stimulating factor (M-CSF) in serum and follicular fluid (FF) at the time of oocyte retrieval and to detect expression of M-CSF and its receptor by luteinized granulosa cells (GCs).

DESIGN

Collection of serum and FF at the time of oocyte retrieval.

SETTING

A university IVF- intracytoplasmic sperm injection (ICSI) program.

PATIENT(S)

Serum and FF were obtained from 85 women undergoing oocyte retrieval.

INTERVENTION(S)

Serum and FF were obtained from 85 women. The GCs were pooled from 15 (3 x 5) patients (3-14 oocytes each).

MAIN OUTCOME MEASURE(S)

The M-CSF concentration was determined by ELISA, the expression of M-CSF and its receptor by the immunocytochemical technique and reverse transcription polymerase chain reaction analysis. In addition, M-CSF expression was investigated by cell culture time course studies.

RESULTS

The median M-CSF concentration in FF (2,409.2 pg/mL) was significantly higher than that in serum (242.5 pg/mL). The M-CSF and its receptor were expressed by GCs.

CONCLUSION(S)

The significantly higher level of M-CSF in FF than in serum and the expression of M-CSF and its receptor in FF by GCs suggest an important role for this growth factor in ovarian function.

Molecular cloning and expression analysis of a macrophage-colony stimulating factor receptor-like gene from rainbow trout, Oncorhynchus mykiss

The M-CSF and its receptor (M-CSFR, CSF-1R or c-fms proto-oncogene) system were initially implicated as essential in mammals for normal monocyte development as well as for pregnancy. To allow a comparison with the M-CSF and M-CSFR system of an oviparous animal, we cloned a M-CSFR-like gene from rainbow trout (Oncorhynchus mykiss). The gene was cloned from a cDNA library of head kidney. It contained an open reading frame encoding 967 amino acids with a predicted size of 109 kDa. The putative amino acid sequence of rainbow trout M-CSFR showed 54% amino acid identity to fugu (Takifugu rubripes) M-CSFR, 52% to zebrafish (Danio rerio) M-CSFR and 40% to mouse (Mus musculus) and human (Homo sapiens) M-CSFR. The M-CSFR-like gene was constitutively expressed in head kidney, kidney, intestine, spleen and blood. The gene was detected especially in the ovary of immature female rainbow trout. These results suggest that a M-CSFR-like receptor may be involved in female reproductive tracts even in an oviparous animal like fish.

Macrophage colony-stimulating factor receptor c-fms is a novel target of imatinib

Imatinib is a tyrosine kinase inhibitor that suppresses the growth of bcr-abl-expressing chronic myeloid leukemia (CML) progenitor cells by blockade of the adenosine triphosphate (ATP)-binding site of the kinase domain of bcr-abl. Imatinib also inhibits the c-abl, platelet-derived growth factor (PDGF) receptor, abl-related gene (ARG) and stem-cell factor (SCF) receptor tyrosine kinases, and has been used clinically to inhibit the growth of malignant cells in patients with CML and gastrointestinal stromal tumors (GISTs). Although initially considered to have minimal effects of normal hematopoiesis, recent studies show that imatinib also inhibits the growth of some nonmalignant hematopoietic cells, including monocyte/macrophages. This inhibition could not be attributed to the known activity profile of imatinib. Here, we demonstrate for the first time that imatinib targets the macrophage colony-stimulating factor (M-CSF) receptor c-fms. Phosphorylation of c-fms was inhibited by therapeutic concentrations of imatinib, and this was not due to down-regulation in c-fms expression. Imatinib was also found to inhibit M-CSF-induced proliferation of a cytokine-dependent cell line, further supporting the hypothesis that imatinib affects the growth and development of monocyte and/or macrophages through inhibition of c-fms signaling. Importantly, these results identify an additional biologic target to those already defined for imatinib. Imatinib should now be assessed for activity in diseases where c-fms activation is implicated, including breast and ovarian cancer and inflammatory conditions.

Identification of the M-CSF Receptor in Endometriosis by Immunohistochemistry and RT-PCR

PROBLEM

The aim of this paper is to provide further evidence that the dystopic proliferation of endometriotic epithelia is caused by the stimulation of peritoneal macrophages. It is essential to show that endometriotic epithelial cells express the macrophage colony-stimulating factor receptor (M-CSFR) which binds the M-CSF produced by the peritoneal macrophages.

METHOD OF STUDY

For the detection of M-CSFR, samples of ectopic endometrium (n = 79) and eutopic endometrium (n = 18) were compared. The specimens were gained at operative laparoscopy in the proliferative phase of the cycle. Cryostat sections were used for immunohistochemical detection. For in vitro reverse transcriptase polymerase chain reaction (RT-PCR) tests, the tissue was immediately shock frozen on paraffin sections. For the in situ RT-PCR technique the specimens were placed in a para-formaldehyde solution, embedded in paraffin and later processed. The Gene Amp 1000 in situ PCR system (Perkin Elmer) was used as the thermal cycler.

RESULTS

M-CSF and the M-CSF receptor are present in eutopic and ectopic endometrium. Qualitatively, with both PCR techniques we found the M-CSF receptor to be present in all samples examined. Using the histochemical detection technique, the M-CSF receptor was found in nearly 70% of endometriosis patients compared with a statistically significant lower percentage in normal endometrium.

CONCLUSIONS

The in situ RT-PCR technique and immunohistochemistry elaborated the need to trace the cellular sources of the M-CSF receptor. The identification of the M-CSF receptor in endometriotic tissue and in endometrium is apt to open a new experimental field in endometriosis research.

Serum levels of macrophage-colony stimulating factor (M-CSF): a marker of kidney allograft rejection

BACKGROUND

Macrophage-colony stimulating factor (M-CSF) is the principal factor for survival of monocytes and macrophages that play an important role in allograft rejection. We studied M-CSF serum levels during successful renal transplantation and acute graft rejection.

METHODS

A total of 114 kidney allograft recipients were assessed for M-CSF levels by enzyme-linked immunosorbent assay (ELISA).

RESULTS

M-CSF serum levels were elevated in pre-transplant haemodialysis patients (611+/-355 IU/ml vs 168+/-61 in normal controls, P<0.01). Following successful renal transplantation, M-CSF decreased in the first month, stabilizing at 257+/-222 IU/ml (not significantly different from normal controls) in 52 post-transplant stable patients. There was no correlation between M-CSF level and creatinine clearance. M-CSF levels increased significantly (2-5 times) during biopsy-proven acute rejection episodes in 20 of 25 patients. All rejection episodes were successfully treated and serum M-CSF decreased rapidly to pre-rejection levels in 17/20 patients. In contrast, in five patients with cyclosporin toxicity and four patients with other causes of allograft dysfunction, M-CSF serum levels did not change.

CONCLUSIONS

M-CSF serum level might be a specific marker of acute rejection. The source of increased production during rejection warrants further investigation, with infiltrating T cells and resident kidney cells being likely candidates.

Hyaluronan-mediated CD44 interaction with RhoGEF and Rho kinase promotes Grb2-associated binder-1 phosphorylation and phosphatidylinositol 3-kinase signaling leading to cytokine (macrophage-colony stimulating factor) production and breast tumor progression

In this study we have examined CD44 (a hyaluronan (HA) receptor) interaction with a RhoA-specific guanine nucleotide exchange factor (p115RhoGEF) in human metastatic breast tumor cells (MDA-MB-231 cell line). Immunoprecipitation and immunoblot analyses indicate that both CD44 and p115RhoGEF are expressed in MDA-MB-231 cells and that these two proteins are physically associated as a complex in vivo. The binding of HA to MDA-MB-231 cells stimulates p115RhoGEF-mediated RhoA signaling and Rho kinase (ROK) activity, which, in turn, increases serine/threonine phosphorylation of the adaptor protein, Gab-1 (Grb2-associated binder-1). Phosphorylated Gab-1 promotes PI 3-kinase recruitment to CD44v3. Subsequently, PI 3-kinase is activated (in particular, alpha, beta, gamma forms but not the delta form of the p110 catalytic subunit), AKT signaling occurs, the cytokine (macrophage-colony stimulating factor (M-CSF)) is produced, and tumor cell-specific phenotypes (e.g. tumor cell growth, survival and invasion) are up-regulated. Our results also demonstrate that HA/CD44-mediated oncogenic events (e.g. AKT activation, M-CSF production and breast tumor cell-specific phenotypes) can be effectively blocked by a PI 3-kinase inhibitor (LY294002). Finally, we have found that overexpression of a dominant-negative form of ROK (by transfection of MBA-MD-231 cells with the Rho-binding domain cDNA of ROK) not only inhibits HA/CD44-mediated RhoA-ROK activation and Gab-1 phosphorylation but also down-regulates oncogenic signaling events (e.g. Gab-1.PI 3-kinase-CD44v3 association, PI 3-kinase-mediated AKT activation, and M-CSF production) and tumor cell behaviors (e.g. cell growth, survival, and invasion). Taken together, these findings strongly suggest that CD44 interaction with p115RhoGEF and ROK plays a pivotal role in promoting Gab-1 phosphorylation leading to Gab-1.PI 3-kinase membrane localization, AKT signaling, and cytokine (M-CSF) production during HA-mediated breast cancer progression.