Oncostatin M suppresses bone morphogenetic protein-4-induced osteoprotegerin synthesis in MC3T3-E1 osteoblast-like cells: p70 S6 kinase attenuation.

Evidence is accumulating that osteal macrophages, in addition to bone-resorbing osteoclasts and bone-forming osteoblasts, participate vitally in bone remodeling process. Oncostatin M (OSM), an inflammatory cytokine belonging to interleukin-6 superfamily, is recognized as an essential factor secreted by osteal macrophages to orchestrate bone remodeling. Osteoprotegerin (OPG) produced by osteoblasts regulates osteoclastogenesis. We have reported that bone morphogenetic protein-4 (BMP-4) stimulates OPG synthesis in MC3T3-E1 osteoblast-like cells, and that SMAD1/5/8(9), p38 mitogen-activated protein kinase (MAPK), and p70 S6 kinase are involved in the OPG synthesis. The present study aims to investigate the effect of OSM on the synthesis of OPG stimulated by BMP-4 in osteoblasts. OSM suppressed the release and the mRNA expression of OPG upregulated by BMP-4 in MC3T3-E1 cells. Neither the BMP-4-induced phosphorylation of SMAD1/5/9 nor that of p38 MAPK was affected by OSM. On the other hand, the phosphorylation of p70 S6 kinase stimulated by BMP-4 was considerably suppressed by OSM. These results strongly suggest that OSM suppresses the BMP-4-stimulated OPG synthesis via inhibition of the p70 S6 kinase-mediated pathway in osteoblast-like cells.

Oncostatin M: Dual Regulator of the Skeletal and Hematopoietic Systems.

PURPOSE OF THE REVIEW: The bone and hematopoietic tissues coemerge during development and are functionally intertwined throughout mammalian life. Oncostatin M (OSM) is an inflammatory cytokine of the interleukin-6 family produced by osteoblasts, bone marrow macrophages, and neutrophils. OSM acts via two heterodimeric receptors comprising GP130 with either an OSM receptor (OSMR) or a leukemia inhibitory factor receptor (LIFR). OSMR is expressed on osteoblasts, mesenchymal, and endothelial cells and mice deficient for the Osm or Osmr genes have both bone and blood phenotypes illustrating the importance of OSM and OSMR in regulating these two intertwined tissues. RECENT FINDINGS: OSM regulates bone mass through signaling via OSMR, adaptor protein SHC1, and transducer STAT3 to both stimulate osteoclast formation and promote osteoblast commitment; the effect on bone formation is also supported by action through LIFR. OSM produced by macrophages is an important inducer of neurogenic heterotopic ossifications in peri-articular muscles following spinal cord injury. OSM produced by neutrophils in the bone marrow induces hematopoietic stem and progenitor cell proliferation in an indirect manner via OSMR expressed by bone marrow stromal and endothelial cells that form hematopoietic stem cell niches. OSM acts as a brake to therapeutic hematopoietic stem cell mobilization in response to G-CSF and CXCR4 antagonist plerixafor. Excessive OSM production by macrophages in the bone marrow is a key contributor to poor hematopoietic stem cell mobilization (mobilopathy) in people with diabetes. OSM and OSMR may also play important roles in the progression of several cancers. It is increasingly clear that OSM plays unique roles in regulating the maintenance and regeneration of bone, hematopoietic stem and progenitor cells, inflammation, and skeletal muscles. Dysregulated OSM production can lead to bone pathologies, defective muscle repair and formation of heterotopic ossifications in injured muscles, suboptimal mobilization of hematopoietic stem cells, exacerbated inflammatory responses, and anti-tumoral immunity. Ongoing research will establish whether neutralizing antibodies or cytokine traps may be useful to correct pathologies associated with excessive OSM production.

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.

Oncostatin M and Nivolumab Affect the Cytotoxic T-Cell Proportions and the Susceptibility to TRAIL-Induced Death in Non-Leukocyte Cell Subpopulations in Soft Tissue Sarcomas.

INTRODUCTION: Soft tissue sarcomas (STSs) are malignant tumors arising from mesenchymal tissues. Patients with advanced and metastatic STSs have low overall survival rates and relatively limited treatment options. Oncostatin M (OSM) is a pleiotropic cytokine that was shown to carry both pro- and anti-tumorigenic properties in various cancer types. However, the role of OSM in STSs has not yet been elucidated. Moreover, the potential additive effects of combining OSM and anti-PD-1 therapy have not been carried out so far. METHODS: The aim of this study was to determine the effects of in vitro OSM administration on liposarcoma, leiomyosarcoma, and myxofibrosarcoma immune cells isolated from peripheral blood and tumor tissues and the potential cooperative nature of OSM and nivolumab in treating these STSs. We designed a cohort study to explore novel histology-driven therapies in our target STSs. The immune cells were isolated from the peripheral blood and tumors of patients with STS, and the proportions and phenotypes of immune cells were evaluated with flow cytometry after cultivation with therapeutic monoclonal antibodies. RESULTS: The proportion of peripheral CD45+ cells was not affected by OSM but was significantly increased by nivolumab, whereas both treatments had an effect on CD8+ T cells. In tumor tissues, CD8+ T cell and CD45‒ TRAIL+ cell cultures were boosted by nivolumab and significantly enriched by OSM. Our data suggest that OSM may play a role in the treatment of leiomyosarcoma, myxofibrosarcoma, and liposarcoma. CONCLUSION: In conclusion, the biological efficacy of OSM is reflected in the tumor microenvironment rather than in the peripheral blood of the patients in our cohort, and nivolumab could potentiate its mechanism of action in selected cases. Nevertheless, more histotype-tailored studies are needed to fully understand the functions of OSM in STSs.

Oncostatin M Contributes to Airway Epithelial Cell Dysfunction in Chronic Rhinosinusitis with Nasal Polyps.

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a typical type-2 inflammation involving several cytokines and is associated with epithelial cell dysfunction. Oncostatin M (OSM) (belonging to the interleukin(IL)-6 family) could be a key driver of epithelial barrier dysfunction. Therefore, we investigated the presence of OSM and IL-6 and the expression pattern of tight junctions (TJs) in the nasal tissue of CRSwNP patients and controls using reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and Western blotting. Then, their potential role in the epithelial barrier was evaluated in vitro in 27 different primary cultures of human nasal epithelial cells (HNECs) by measuring TJ expression and transepithelial electric resistance (TEER) with or without OSM or IL-6 (1, 10, and 100 ng/mL). The effect on ciliary beating efficiency was evaluated by high-speed videomicroscopy and on repair mechanisms with a wound healing model with or without OSM. OSM and IL-6 were both overexpressed, and TJ (ZO-1 and occludin) expression was decreased in the nasal polyps compared to the control mucosa. OSM (100 ng/mL) but not IL-6 induced a significant decrease in TJ expression, TEER, and ciliary beating efficiency in HNECs. After 24 h, the wound repair rate was significantly higher in OSM-stimulated HNECs at 100 ng/mL. These results suggest that OSM could become a new target for monoclonal antibodies.

Oncostatin M-Enriched Small Extracellular Vesicles Derived from Mesenchymal Stem Cells Prevent Isoproterenol-Induced Fibrosis and Enhance Angiogenesis.

Myocardial fibrosis is a pathological hallmark of cardiac dysfunction. Oncostatin M (OSM) is a pleiotropic cytokine that can promote fibrosis in different organs after sustained exposure. However, OSM released by macrophages during cardiac fibrosis suppresses cardiac fibroblast activation by modulating transforming growth factor beta 1 (TGF-ß1) expression and extracellular matrix deposition. Small extracellular vesicles (SEVs) from mesenchymal stromal cells (MSCs) are being investigated to treat myocardial infarction, using different strategies to bolster their therapeutic ability. Here, we generated TERT-immortalized human MSC cell lines (MSC-T) engineered to overexpress two forms of cleavage-resistant OSM fused to CD81TM (OSM-SEVs), which allows the display of the cytokine at the surface of secreted SEVs. The therapeutic potential of OSM-SEVs was assessed in vitro using human cardiac ventricular fibroblasts (HCF-Vs) activated by TGF-ß1. Compared with control SEVs, OSM-loaded SEVs reduced proliferation in HCF-V and blunted telo-collagen expression. When injected intraperitoneally into mice treated with isoproterenol, OSM-loaded SEVs reduced fibrosis, prevented cardiac hypertrophy, and increased angiogenesis. Overall, we demonstrate that the enrichment of functional OSM on the surface of MSC-T-SEVs increases their potency in terms of anti-fibrotic and pro-angiogenic properties, which opens new perspectives for this novel biological product in cell-free-based therapies.

Exogenous Oncostatin M induces Cardiac Dysfunction, Musculoskeletal Atrophy, and Fibrosis.

Musculoskeletal diseases such as muscular dystrophy, cachexia, osteoarthritis, and rheumatoid arthritis impair overall physical health and reduce survival. Patients suffer from pain, dysfunction, and dysmobility due to inflammation and fibrosis in bones, muscles, and joints, both locally and systemically. The Interleukin-6 (IL-6) family of cytokines, most notably IL-6, is implicated in musculoskeletal disorders and cachexia. Here we show elevated circulating levels of OSM in murine pancreatic cancer cachexia and evaluate the effects of the IL-6 family member, Oncostatin M (OSM), on muscle and bone using adeno-associated virus (AAV) mediated over-expression of murine OSM in wildtype and IL-6 deficient mice. Initial studies with high titer AAV-OSM injection yielded high circulating OSM and IL-6, thrombocytosis, inflammation, and 60% mortality without muscle loss within 4 days. Subsequently, to mimic OSM levels in cachexia, a lower titer of AAV-OSM was used in wildtype and Il6 null mice, observing effects out to 4 weeks and 12 weeks. AAV-OSM caused muscle atrophy and fibrosis in the gastrocnemius, tibialis anterior, and quadriceps of the injected limb, but these effects were not observed on the non-injected side. In contrast, OSM induced both local and distant trabecular bone loss as shown by reduced bone volume, trabecular number, and thickness, and increased trabecular separation. OSM caused cardiac dysfunction including reduced ejection fraction and reduced fractional shortening. RNA-sequencing of cardiac muscle revealed upregulation of genes related to inflammation and fibrosis. None of these effects were different in IL-6 knockout mice. Thus, OSM induces local muscle atrophy, systemic bone loss, tissue fibrosis, and cardiac dysfunction independently of IL-6, suggesting a role for OSM in musculoskeletal conditions with these characteristics, including cancer cachexia.

Oncostatin M triggers brain inflammation by compromising blood-brain barrier integrity.

Oncostatin M (OSM) is an IL-6 family member which exerts neuroprotective and remyelination-promoting effects after damage to the central nervous system (CNS). However, the role of OSM in neuro-inflammation is poorly understood. Here, we investigated OSM's role in pathological events important for the neuro-inflammatory disorder multiple sclerosis (MS). We show that OSM receptor (OSMRß) expression is increased on circulating lymphocytes of MS patients, indicating their elevated responsiveness to OSM signalling. In addition, OSM production by activated myeloid cells and astrocytes is increased in MS brain lesions. In experimental autoimmune encephalomyelitis (EAE), a preclinical model of MS, OSMRß-deficient mice exhibit milder clinical symptoms, accompanied by diminished T helper 17 (Th17) cell infiltration into the CNS and reduced BBB leakage. In vitro, OSM reduces BBB integrity by downregulating the junctional molecules claudin-5 and VE-cadherin, while promoting secretion of the Th17-attracting chemokine CCL20 by inflamed BBB-endothelial cells and reactive astrocytes. Using flow cytometric fluorescence resonance energy transfer (FRET) quantification, we found that OSM-induced endothelial CCL20 promotes activation of lymphocyte function-associated antigen 1 (LFA-1) on Th17 cells. Moreover, CCL20 enhances Th17 cell adhesion to OSM-treated inflamed endothelial cells, which is at least in part ICAM-1 mediated. Together, these data identify an OSM-CCL20 axis, in which OSM contributes significantly to BBB impairment during neuro-inflammation by inducing permeability while recruiting Th17 cells via enhanced endothelial CCL20 secretion and integrin activation. Therefore, care should be taken when considering OSM as a therapeutic agent for treatment of neuro-inflammatory diseases such as MS.

The JAK inhibitor baricitinib inhibits oncostatin M induction of proinflammatory mediators in ex-vivo synovial derived cells.

OBJECTIVES: To investigate the ex vivo effect of the JAK1/2 inhibitor baricitinib on expression of pro-inflammatory mediators in rheumatoid arthritis (RA) fibroblast like synoviocytes (FLS) stimulated with TNFα, IL-1ß and oncostatin M (OSM), and in RA synovial membrane cells (SMCs). METHODS: RA and osteoarthritis (OA) SMCs, were isolated from arthroplasty specimens of RA (n=8) and OA (n=8) patients, respectively, using enzymatic digestion followed by cell propagation to obtain RA (n=5) and OA (n=3) FLS. Normal FLS and normal human foreskin fibroblasts (HSF) were purchased from commercial sources. Fibroblasts were stimulated with cytokines with or without baricitinib. RA SMCs were cultured in the presence of baricitinib without stimulation. JAK/STAT activation and levels of mRNA and proteins of the various inflammatory cytokines (IL-6, IL-8, MCP-1, RANTES and IP-10) were determined by qPCR, ELISA and MSD. RESULTS: Baricitinib inhibited OSM-induced JAK signalling in RA synovial fibroblasts and effectively suppressed subsequent expression of the proinflammatory mediators IL-6, MCP-1 and IP-10. However, baricitinib was not effective in altering levels of spontaneously released TNFα, IL-6 and IL-8 in RA SMC. Although both TNFα and IL-1ß signal independently of the JAK/STAT pathway, in HSF, but not in RA FLS, baricitinib significantly inhibited TNFα- and IL-1ß-induced MCP-1 and IP-10 protein levels in a dose dependent manner. Furthermore, baricitinib did not inhibit TNFα- and IL-1ß-induced expression of IL-6, IL-8 and MCP-1 in RA FLS. CONCLUSIONS: These findings are consistent with known signalling pathways employed by OSM, TNFα and IL-1ß, but our data suggest that in HSF, baricitinib may have anti-inflammatory effects via downstream modulation of cytokines and chemokines produced in response to TNFα or IL-1ß.

Oncostatin M Counteracts the Fibrotic Effects of TGF-ß1 and IL-4 on Nasal-Polyp-Derived Fibroblasts: A Control of Fibrosis in Chronic Rhinosinusitis with Nasal Polyps?

Chronic rhinosinusitis with nasal polyps (CRSwNP) is associated with inflammation and tissue remodeling including myofibroblasts differentiation and extracellular matrix (ECM) deposition mediated by TGF-ß1 and IL-4. Oncostatin M (OSM) is a cytokine involved in fibrotic processes in other cellular subtypes. We investigated the mechanisms of action of OSM in the fibrosis process associated with CRSwNP. The expression of IL-4, OSM and TGF-ß1 was assessed by RT-qPCR. Primary human cultures of nasal-polyp-derived fibroblasts were established and stimulated by TGF-ß1 and/or IL-4 and/or OSM. The expression of ECM components and αSMA was determined by RT-qPCR and Western blot. TGF-ß1-Smad3 signaling was investigated by immunofluorescence. TGF-ß1, IL-4 and OSM as well as αSMA were overexpressed in nasal polyps when compared to noninflammatory nasal mucosa. In TGF-ß1-stimulated nasal-polyp-derived fibroblasts, ECM genes and αSMA gene and protein were overexpressed, as well as αSMA in IL-4-stimulated fibroblasts. OSM counteracted the profibrotic effect of TGF-ß1 on ECM components and αSMA. TGF-ß1-induced nuclear translocation of Smad3 was completely reversed by OSM. OSM counteracts the profibrotic effect of IL-4 and also TGF-ß1, by inhibiting the nuclear translocation of Smad3. We suggest OSM could be an efficient tool to protect against fibrosis in CRSwNP.

Novel mechanism for OSM-promoted extracellular matrix remodeling in breast cancer: LOXL2 upregulation and subsequent ECM alignment.

BACKGROUND: Invasive ductal carcinoma (IDC) is a serious problem for patients as it metastasizes, decreasing 5-year patient survival from > 95 to ~ 27%. The breast tumor microenvironment (TME) is often saturated with proinflammatory cytokines, such as oncostatin M (OSM), which promote epithelial-to-mesenchymal transitions (EMT) in IDC and increased metastasis. The extracellular matrix (ECM) also plays an important role in promoting invasive and metastatic potential of IDC. Specifically, the reorganization and alignment of collagen fibers in stromal ECM leads to directed tumor cell motility, which promotes metastasis. Lysyl oxidase like-2 (LOXL2) catalyzes ECM remodeling by crosslinking of collagen I in the ECM. We propose a novel mechanism whereby OSM induces LOXL2 expression, mediating stromal ECM remodeling of the breast TME. METHODS: Bioinformatics was utilized to determine survival and gene correlation in patients. IDC cell lines were treated with OSM (also IL-6, LIF, and IL-1ß) and analyzed for LOXL2 expression by qRT-PCR and immunolabelling techniques. Collagen I contraction assays, 3D invasion assays, and confocal microscopy were performed with and without LOXL2 inhibition to determine the impact of OSM-induced LOXL2 on the ECM. RESULTS: Our studies demonstrate that IDC patients with high LOXL2 and OSM co-expression had worse rates of metastasis-free survival than those with high levels of either, individually, and LOXL2 expression is positively correlated to OSM/OSM receptor (OSMR) expression in IDC patients. Furthermore, human IDC cells treated with OSM resulted in a significant increase in LOXL2 mRNA, which led to upregulated protein expression of secreted, glycosylated, and enzymatically active LOXL2. The expression of LOXL2 in IDC cells did not affect OSM-promoted EMT, and LOXL2 was localized to the cytoplasm and/or secreted. OSM-induced LOXL2 promoted an increase in ECM collagen I fiber crosslinking, which led to significant fiber alignment between cells and increased IDC cell invasion. CONCLUSIONS: Aligned collagen fibers in the ECM provide pathways for tumor cells to migrate more easily through the stroma to nearby vasculature and tissue. These results provide a new paradigm through which proinflammatory cytokine OSM promotes tumor progression. Understanding the nuances in IDC metastasis will lead to better potential therapeutics to combat against the possibility.

Analysis of hiPSCs differentiation toward hepatocyte-like cells upon extended exposition to oncostatin.

The capability to produce and maintain functional human adult hepatocytes remains one of the major challenges for the use of in-vitro models toward liver cell therapy and industrial drug-screening applications. Among the suggested strategies to solve this issue, the use of human-induced pluripotent stem cells (hiPSCs), differentiated toward hepatocyte-like cells (HLCs) is promising. In this work, we propose a 31-day long protocol, that includes a final 14-day long phase of oncostatin treatment, as opposed to a 7-day treatment which led to the formation of a hepatic tissue functional for CYP1A2, CYP2B6, CYP2C8, CYP2D6, and CYP3A4. The production of albumin, as well as bile acid metabolism and transport, were also detected. Transcriptome profile comparisons and liver transcription factors (TFs) motif dynamics revealed increased expression of typical hepatic markers such as HNF1A and of important metabolic markers like PPARA. The performed analysis has allowed for the extraction of potential targets and pathways which would allow enhanced hepatic maturation in-vitro. From this investigation, NRF1 and SP3 appeared as transcription factors of importance. Complex epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) patterns were also observed during the differentiation process. Moreover, whole transcriptome analysis highlighted a response typical of the one observed in liver regeneration and hepatocyte proliferation. While a complete maturation of hepatocytes was yet to be obtained, the results presented in this work provide new insights into the process of liver development and highlight potential targets aimed to improve in-vitro liver regeneration.

Interferon-γ is a master checkpoint regulator of cytokine-induced differentiation.

Cytokines are protein mediators that are known to be involved in many biological processes, including cell growth, survival, inflammation, and development. To study their regulation, we generated a library of 209 different cytokines. This was used in a combinatorial format to study the effects of cytokines on each other, with particular reference to the control of differentiation. This study showed that IFN-γ is a master checkpoint regulator for many cytokines. It operates via an autocrine mechanism to elevate STAT1 and induce internalization of gp130, a common component of many heterodimeric cytokine receptors. This targeting of a receptor subunit that is common to all members of an otherwise diverse family solves the problem of how a master regulator can control so many diverse receptors. When one adds an autocrine mechanism, fine control at the level of individual cells is achieved.

The Anti-ADAMTS-5 Nanobody® M6495 Protects Cartilage Degradation Ex Vivo.

Osteoarthritis (OA) is associated with cartilage breakdown, brought about by ADAMTS-5 mediated aggrecan degradation followed by MMP-derived aggrecan and type II collagen degradation. We investigated a novel anti-ADAMTS-5 inhibiting Nanobody® (M6495) on cartilage turnover ex vivo. Bovine cartilage (BEX, n = 4), human osteoarthritic - (HEX, n = 8) and healthy-cartilage (hHEX, n = 1) explants and bovine synovium and cartilage were cultured up to 21 days in medium alone (w/o), with pro-inflammatory cytokines (oncostatin M (10 ng/mL) + TNFα (20 ng/mL) (O + T), IL-1α (10 ng/mL) or oncostatin M (50 ng/mL) + IL-1ß (10 ng/mL)) with or without M6495 (1000-0.46 nM). Cartilage turnover was assessed in conditioned medium by GAG (glycosaminoglycan) and biomarkers of ADAMTS-5 driven aggrecan degradation (huARGS and exAGNxI) and type II collagen degradation (C2M) and formation (PRO-C2). HuARGS, exAGNxI and GAG peaked within the first culture week in pro-inflammatory stimulated explants. C2M peaked from day 14 by O + T and day 21 in co-culture experiments. M6495 dose dependently decreased huARGS, exAGNxI and GAG after pro-inflammatory stimulation. In HEX C2M was dose-dependently reduced by M6495. M6495 showed no effect on PRO-C2. M6495 showed cartilage protective effects by dose-dependently inhibiting ADAMTS-5 mediated cartilage degradation and inhibiting overall cartilage deterioration in ex vivo cartilage cultures.

Oncostatin M inhibits differentiation of rat stem Leydig cells in vivo and in vitro.

Oncostatin M (OSM) is a pleiotropic cytokine within the interleukin six family of cytokines, which regulate cell growth and differentiation in a wide variety of biological systems. However, its action and underlying mechanisms on stem Leydig cell development are unclear. The objective of the present study was to investigate whether OSM affects the proliferation and differentiation of rat stem Leydig cells. We used a Leydig cell regeneration model in rat testis and a unique seminiferous tubule culture system after ethane dimethane sulfonate (EDS) treatment to assess the ability of OSM in the regulation of proliferation and differentiation of rat stem Leydig cells. Intratesticular injection of OSM (10 and 100 ng/testis) from post-EDS day 14 to 28 blocked the regeneration of Leydig cells by reducing serum testosterone levels without affecting serum luteinizing hormone and follicle-stimulating hormone levels. It also decreased the levels of Leydig cell-specific mRNAs (Lhcgr, Star, Cyp11a1, Hsd3b1, Cyp17a1 and Hsd11b1) and their proteins by the RNA-Seq and Western blotting analysis. OSM had no effect on the proliferative capacity of Leydig cells in vivo. In the seminiferous tubule culture system, OSM (0.1, 1, 10 and 100 ng/mL) inhibited the differentiation of stem Leydig cells by reducing medium testosterone levels and downregulating the expression of Leydig cell-specific genes (Lhcgr, Star, Cyp11a1, Hsd3b1, Cyp17a1 and Hsd11b1) and their proteins. OSM-mediated action was reversed by S3I-201 (a STAT3 antagonist) or filgotinib (a JAK1 inhibitor). These data suggest that OSM is an inhibitory factor of rat stem Leydig cell development.

Oncostatin M induces C2C12 myotube atrophy by modulating muscle differentiation and degradation.

Oncostatin M (OSM) is a cytokine of the interleukin-6 family and plays a role in various disorders such as cancer and inflammatory diseases, which are often accompanied by skeletal muscle atrophy, or sarcopenia. However, the role of OSM in the regulation of skeletal muscle mass remains to be identified. In this study, we investigated the effect of OSM on C2C12 myotube formation in vitro. C2C12 myoblasts were induced to differentiate into myotubes for 3 days and then treated with OSM for 24 or 48 h. The diameter of differentiated C2C12 myotubes were reduced by 18.7% and 23.3% compared to control cells after treatment with OSM for 24 and 48 h, respectively. The expression levels of MyoD and myogenin were decreased, while those of atrogin-1, CCAAT/enhancer binding protein δ, and OSM receptor were increased in C2C12 myotubes treated with OSM for 24 h compared to control cells. Furthermore, the inhibitory effect of OSM on myotube formation was significantly attenuated by pretreatment with an inhibitor of signal transducer and activator of transcription (STAT) 3 or by knockdown of Stat3. Finally, the OSM-induced changes in the expression levels of MyoD, myogenin, and atrogin-1 were reversed by pretreatment with an inhibitor of STAT3 or by Stat3 knockdown in C2C12 myotubes. In conclusion, OSM induces C2C12 myotube atrophy by inhibiting myogenic differentiation and activating muscle degradation in a STAT3-dependent manner.

M2 polarization of macrophages by Oncostatin M in hypoxic tumor microenvironment is mediated by mTORC2 and promotes tumor growth and metastasis.

Oncostatin M (OSM), an inflammatory cytokine belonging to the interleukin-6 (IL-6) superfamily, plays a vital role in multitude of physiological and pathological processes. Its role in breast tumor progression and metastasis to distant organs is well documented. Recent reports implicate OSM in macrophage M2 polarization, a key pro-tumoral phenomenon. M2 polarization of macrophages is believed to promote tumor progression by potentiating metastasis and angiogenesis. In the current study, we delineated the mechanism underlying OSM induced macrophage M2 polarization. The findings revealed that OSM skews macrophages towards an M2 polarized phenotype via mTOR signaling complex 2 (mTORC2). mTORC2 relays signals through two effector kinases i.e. PKC-α and Akt. Our results indicated that mTORC2 mediated M2 polarization of macrophages is not dependent on PKC-α and is primarily affected via Akt, particularly Akt1. In vivo studies conducted on 4T1/BALB/c mouse orthotropic model of breast cancer further corroborated these observations wherein i.v. reintroduction of mTORC2 abrogated monocytes into orthotropic mouse model resulted in diminished acquisition of M2 specific attributes by tumor associated macrophages. Metastasis to distant organs like lung, liver and bone was reduced as evident by decrease in formation of focal metastatic lesions in mTORC2 abrogated monocytes mice. Our study pinpoints key role of mTORC2-Akt1 axis in OSM induced macrophage polarization and suggests for possible usage of Oncostatin-M blockade and/or selective mTORC2 inhibition as a potential anti-cancer strategy particularly with reference to metastasis of breast cancer to distant organs such as lung, liver and bone.

Oncostatin M receptor, positively regulated by SP1, promotes gastric cancer growth and metastasis upon treatment with Oncostatin M.

BACKGROUND: Oncostatin M receptor (OSMR) is a member of the interleukin 6 (IL-6) receptor family that transduces signaling events of Oncostatin M (OSM). OSM-OSMR signaling plays a key role in inflammation and cancer progression. However, the role of OSM-OSMR in gastric cancer (GC) is still unknown. METHODS: OSMR expression in GC was determined by real-time PCR (RT-PCR), immunohistochemistry (IHC) and Western blot. The effects of OSM-OSMR on GC cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) in vitro and metastasis in vivo were examined. The pathways underlying OSM-OSMR signaling were explored by Western blot. Regulatory mechanism between SP1 and OSMR was explored in vitro. RESULTS: OSMR was highly expressed in GC tissues and its expression level was closely associated with age, T stage, Lauren classification, lymph node metastasis, TNM stage and worse prognosis of patients with GC. Knockdown of OSMR expression in GC cells significantly inhibited cell proliferation, migration, invasion, and EMT in vitro, as well as tumorigenesis and peritoneal metastasis in vivo induced by OSM. These effects mediated by OSM-OSMR were dependent on the activation of STAT3/FAK/Src signaling. SP1 could bind to the promoter region of human OSMR gene from - 255 to - 246 bp, and transcriptionally regulated OSMR overexpression in GC cells. CONCLUSIONS: OSM-OSMR contributes to GC progression through activating STAT3/FAK/Src signaling, and OSMR is transcriptionally activated by SP1.

Oncostatin M Suppresses Activation of IL-17/Th17 via SOCS3 Regulation in CD4+ T Cells.

Oncostatin M (OSM) is a pleiotropic cytokine and a member of the IL-6 family. It has both proinflammatory and anti-inflammatory functions and is involved in the activation of STAT3 and STAT5. Rheumatoid arthritis is an autoimmune disease that causes chronic and excessive inflammation. Rheumatoid arthritis can lead to induction of Th17 cells, which express IL-17. The aim of this study was to measure the effects of OSM on the proliferation of regulatory T cells and Th17 cells from mice. IL-2 immune complex suppressed the development of collagen-induced arthritis in mice and altered the regulatory T/Th17 cell balance by increasing OSM expression. OSM mitigated the proliferation of Th17 cells and decreased the expression of IL-17 and IL-21. It promoted the activation of suppressor of cytokine signaling 3 (SOCS3), STAT3, and STAT5. Inhibition of SOCS3, STAT3, and STAT5 lessened the OSM-induced reduction in proliferation of Th17 cells. These observations suggest that OSM can inhibit Th17 differentiation by reciprocally controlling SOCS3, STAT3, and STAT5.

Adenosine Attenuates Aortic Smooth Muscle Cell Calcification through A3 Adenosine Receptor.

Vascular calcification is a typical feature of atherosclerosis and is associated with adverse cardiovascular events such as myocardial infarction and stroke. Several studies have suggested that adenosine, an ATP metabolite may function as an endogenous regulator of arterial calcification. However, its effects on vascular smooth muscle cell calcification have not been clarified. In this study, we investigated the inhibitory effects of adenosine on vascular calcification in vitro by utilizing the culture of human aortic smooth muscle cells (HASMCs). Osteoblastic differentiation of HASMCs was induced by the treatment with oncostatin M and osteogenic differentiation medium. Adenosine and its metabolically stable analogue, 2-chloroadenosine (CADO) significantly reduced matrix mineralization and alkaline phosphatase (ALP) activities in HASMCs. The mRNA expression of tissue non-specific alkaline phosphatase (TNAP) was down-regulated by adenosine and CADO, but the mRNA expression of other osteoblastic differentiation markers, such as Runt-related transcription factor 2 (RUNX2) and bone sialoprotein (BSP)-II, was not significantly affected by these two reagents. Among the adenosine receptor (AR) subtype-selective agonists used, only IB-MECA (A3 AR-selective agonist) significantly decreased in vitro mineralization and ALP activities in HASMCs, but not with CCPA (A1 AR-selective agonist), CGS21680 (A2a AR-selective agonist), or BAY60-6583 (A2b AR-selective agonist). Importantly, IB-MECA also down-regulated expression of TNAP mRNA. Finally, knockdown of A3 AR, but not A1 AR, A2a AR, or A2b AR, significantly reversed the inhibitory actions of adenosine, CADO, or IB-MECA on in vitro calcification and ALP activities in HASMCs. These data suggest that adenosine attenuates HASMC calcification through A3 AR.