Bone morphogenetic protein 6-induced interleukin-1β expression in macrophages requires PU.1/Smad1 interaction

BMP-6 promotes type 2 immune response during enhancement of rat mandibular bone defect healing

Introduction

Bone morphogenetic proteins (BMPs) are used as key therapeutic agents for the treatment of difficult fractures. While their effects on osteoprogenitors are known, little is known about their effects on the immune system.

Methods

We used permutations of BMP-6 (B), vascular endothelial growth factor (V), and Hedgehog signaling pathway activator smoothened agonist (S), to treat a rat mandibular defect and investigated healing outcomes at week 8, in correlation with the cellular landscape of the immune cells in the fracture callus at week 2.

Results

Maximum recruitment of immune cells to the fracture callus is known to occur at week 2. While the control, S, V, and VS groups remained as nonunions at week 8; all BMP-6 containing groups - B, BV, BS and BVS, showed near-complete to complete healing. This healing pattern was strongly associated with significantly higher ratios of CD4 T (CD45⁺CD3⁺CD4⁺) to putative CD8 T cells (CD45⁺CD3⁺CD4^-), in groups treated with any permutation of BMP-6. Although, the numbers of putative M1 macrophages (CD45⁺CD3^-CD11b/c⁺CD38^high) were significantly lower in BMP-6 containing groups in comparison with S and VS groups, percentages of putative - Th1 cells or M1 macrophages (CD45⁺CD4⁺IFN-γ⁺) and putative - NK, NKT or cytotoxic CD8T cells (CD45⁺CD4^-IFN-γ⁺) were similar in control and all treatment groups. Further interrogation revealed that the BMP-6 treatment promoted type 2 immune response by significantly increasing the numbers of CD45⁺CD3^-CD11b/c⁺CD38^low putative M2 macrophages, putative - Th2 cells or M2 macrophages (CD45⁺CD4⁺IL-4⁺) cells and putative - mast cells, eosinophils or basophils (CD45⁺CD4^-IL-4⁺ cells). CD45^- non-haematopoietic fractions of cells which encompass all known osteoprogenitor stem cells populations, were similar in control and treatment groups.

Discussion

This study uncovers previously unidentified regulatory functions of BMP-6 and shows that BMP-6 enhances fracture healing by not only acting on osteoprogenitor stem cells but also by promoting type 2 immune response.

Recapitulation of pro-inflammatory signature of monocytes with ACVR1A mutation using FOP patient-derived iPSCs

BACKGROUND

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease characterized by progressive heterotopic ossification (HO) in soft tissues due to a heterozygous mutation of the ACVR1A gene (FOP-ACVR1A), which erroneously transduces the BMP signal by Activin-A. Although inflammation is known to trigger HO in FOP, the role of FOP-ACVR1A on inflammatory cells remains to be elucidated.

RESULTS

We generated immortalized monocytic cell lines from FOP-iPSCs (FOP-ML) and mutation rescued iPSCs (resFOP-ML). Cell morphology was evaluated during the monocyte induction and after immortalization. Fluorescence-activated cell sorting (FACS) was performed to evaluate the cell surface markers CD14 and CD16 on MLs. MLs were stimulated with lipopolysaccharide or Activin-A and the gene expression was evaluated by quantitative PCR and microarray analysis. Histological analysis was performed for HO tissue obtained from wild type mice and FOP-ACVR1A mice which conditionally express human mutant ACVR1A gene by doxycycline administration. Without any stimulation, FOP-ML showed the pro-inflammatory signature of CD16+ monocytes with an upregulation of INHBA gene, and treatment of resFOP-ML with Activin-A induced an expression profile mimicking that of FOP-ML at baseline. Treatment of FOP-ML with Activin-A further induced the inflammatory profile with an up-regulation of inflammation-associated genes, of which some, but not all, of which were suppressed by corticosteroid. Experiments using an inhibitor for TGFβ or BMP signal demonstrated that Activin-A-induced genes such as CD16 and CCL7, were regulated by both signals, indicating Activin-A transduced dual signals in FOP-ML. A comparison with resFOP-ML identified several down-regulated genes in FOP-ML including LYVE-1, which is known to suppress matrix-formation in vivo. The down-regulation of LYVE-1 in HO tissues was confirmed in FOP model mice, verifying the significance of the in vitro experiments.

CONCLUSION

These results indicate that FOP-ML faithfully recapitulated the phenotype of primary monocytes of FOP and the combination with resFOP-ML is a useful tool to investigate molecular events at the initial inflammation stage of HO in FOP.

Gender-Related Differences in BMP Expression and Adult Hippocampal Neurogenesis within Joint-Hippocampal Axis in a Rat Model of Rheumatoid Arthritis

BMPs regulate synovial quiescence and adult neurogenesis in the hippocampus in non-stress conditions. However, changes in BMP expression that are induced by inflammation during rheumatoid arthritis (RA) have not yet been reported. Here, we show that signalling with synovial BMPs (BMP-4 and -7) mediates the effect of systemic inflammation on adult neurogenesis in the hippocampus during pristane-induced arthritis (PIA) in Dark Agouti (DA) rats, an animal model of RA. Moreover, we show gender differences in BMP expressions and their antagonists (Noggin and Gremlin) during PIA and their correlations with the clinical course and IL-17A and TNF-α levels in serum. Our results indicate gender differences in the clinical course, where male rats showed earlier onset and earlier recovery but a worse clinical course in the first two phases of the disease (onset and peak), which correlates with the initial increase of serum IL-17A level. The clinical course of the female rats worsened in remission. Their prolonged symptoms could be a reflection of an increased TNF-α level in serum during remission. Synovial inflammation was greater in females in PIA-remission with greater synovial BMP and antagonist expressions. More significant correlations between serum cytokines (IL-17A and TNF-α), and synovial BMPs and their antagonists were found in females than in males. On the other hand, males showed an increase in hippocampal BMP-4 expression during the acute phase, but both genders showed a decrease in antagonist expressions during PIA in general. Both genders showed a decrease in the number of Ki-67⁺ and SOX-2⁺ and DCX⁺ cells and in the ratio of DCX⁺ to Ki67⁺ cells in the dentate gyrus during PIA. However, in PIA remission, females showed a faster increase in the number of Ki67⁺, SOX-2⁺, and DCX⁺ cells and a faster increase in the DCX/Ki67 ratio than males. Both genders showed an increase of hippocampal BMP-7 expression during remission, although males constantly showed greater BMP-7 expression at all time points. Our data show that gender differences exist in the BMP expressions in the periphery-hippocampus axis and in the IL-17A and TNF-α levels in serum, which could imply differences in the mechanisms for the onset and progression of the disease, the clinical course severity, and adult neurogenesis with subsequent neurological complications between genders.

Role of the BMP6 protein in breast cancer and other types of cancer

The BMP6 protein (Bone Morphogenetic Protein 6) is part of the superfamily of transforming growth factor-beta (TGF-β) ligands, participates in iron homeostasis, inhibits invasion by increasing adhesions and cell-cell type interactions and induces angiogenesis directly on vascular endothelial cells. BMP6 is coded by a tumor suppressor gene whose subexpression is related to the development and cancer progression; during neoplastic processes, methylation is the main mechanism by which gene silencing occurs. This work presents a review on the role of BMP6 protein in breast cancer (BC) and other types of cancer. The studies carried out to date suggest the participation of the BMP6 protein in the epithelial-mesenchymal transition (EMT) phenotype, cell growth and proliferation; however, these processes are affected in a variable way in the different types of cancer, the methylated CpG sites in BMP6 gene promoter, as well as the interaction with other proteins could be the cause of such variation.

Adipose tissue plasticity and the pleiotropic roles of BMP signaling

Adipose tissues, including white, beige, and brown adipose tissue, have evolved to be highly dynamic organs. Adipose tissues undergo profound changes during development and regeneration and readily undergo remodeling to meet the demands of an everchanging metabolic landscape. The dynamics are determined by the high plasticity of adipose tissues, which contain various cell types: adipocytes, immune cells, endothelial cells, nerves, and fibroblasts. There are numerous proteins that participate in regulating the plasticity of adipose tissues. Among these, bone morphogenetic proteins (BMPs) were initially found to regulate the differentiation of adipocytes, and they are being reported to have pleiotropic functions by emerging studies. Here, in the first half of the article, we summarize the plasticity of adipocytes and macrophages, which are two groups of cells targeted by BMP signaling in adipose tissues. We then review how BMPs regulate the differentiation, death, and lipid metabolism of adipocytes. In addition, the potential role of BMPs in regulating adipose tissue macrophages is considered. Finally, the expression of BMPs in adipose tissues and their metabolic relevance are discussed.

Blockade of bone morphogenetic protein signaling potentiates the pro-inflammatory phenotype induced by interleukin-17 and tumor necrosis factor-α combination in rheumatoid synoviocytes

Introduction

Bone morphogenetic proteins (BMPs) are multifunctional secreted growth factors regulating a broad spectrum of functions in numerous systems. An increased expression and production of specific BMPs have been described in the rheumatoid arthritis (RA) synovium. The aim of this study was to analyze the involvement of the BMP signaling pathway in RA synoviocytes in response to interleukin-17 (IL-17) and tumor necrosis factor-alpha (TNF-α).

Methods

The expression of components of the BMP signaling pathway (BMP receptors, BMP ligands, BMP signal transducers, and BMP antagonists) was analyzed by quantitative polymerase chain reaction before and after treatment of RA synoviocytes with TNF-α or IL-17 or both. Regulation was studied in the presence of the specific BMP inhibitor DMH1 (dorsomorphin homologue 1) or an exogenous BMP ligand, BMP6. Expression and production of pro-inflammatory cytokines (IL-6 and granulocyte-macrophage colony-stimulating factor), chemokines (IL-8, CCL2, CCL5, and CXCL10), and matrix metalloproteinases (MMP-1, −2, −3, −9, and −13) were analyzed.

Results

RA synoviocytes express BMP receptors (mainly BMPRIA, ACTRIA, and BMPRII), signal transducers of the Smad family (Smad1 and 5 and co-Smad4), and different BMP antagonists. The modulation of the expression of the BMP target genes—Id (inhibitor of DNA-binding/differentiation) proteins and Runx (Runt-related transcription factor) transcription factors—after the addition of exogenous BMP shows that the BMP signaling pathway is active. RA synoviocytes also express BMP ligands (BMP2, BMP6, and BMP7) which are highly upregulated after activation with TNF-α and IL-17. Autocrine BMP signaling pathway can be blocked by treatment with the inhibitor DMH1, leading to an increase in the upregulated expression of pro-inflammatory cytokines, chemokines, and MMPs induced by the activation of RA synoviocytes with TNF-α and IL-17. Conversely, the additional stimulation of the BMP pathway with the exogenous addition of the BMP6 ligand decreases the expression of those pro-inflammatory and pro-destructive factors.

Conclusion

The results indicate that the canonical BMP pathway is functionally active in human RA synoviocytes and that the inhibition of autocrine BMP signaling exacerbates the pro-inflammatory phenotype induced in RA synoviocytes by the stimulation with IL-17 and TNF-α.

Inhibition of BMP signaling suppresses metastasis in mammary cancer

Bone morphogenetic proteins (BMPs) are secreted cytokines/growth factors that have differing roles in cancer. BMPs are overexpressed in human breast cancers, but loss of BMP signaling in mammary carcinomas can accelerate metastasis. We show that human breast cancers display active BMP signaling, which is rarely downregulated or homozygously deleted. We hypothesized that systemic inhibition of BMP signaling in both the tumor and the surrounding microenvironment could prevent tumor progression and metastasis. To test this hypothesis, we used DMH1, a BMP antagonist, in MMTV.PyVmT expressing mice. Treatment with DMH1 reduced lung metastasis and the tumors were less proliferative and more apoptotic. In the surrounding tumor microenvironment, treatment with DMH1 altered fibroblasts, lymphatic vessels and macrophages to be less tumor promoting. These results indicate that inhibition of BMP signaling may successfully target both the tumor and the surrounding microenvironment to reduce tumor burden and metastasis.

Noggin improves ischemic brain tissue repair and promotes alternative activation of microglia in mice

We previously reported that bone morphogenetic proteins (BMPs) and their endogenous antagonist noggin are expressed in the brain weeks after an ischemic insult. Here, to define their roles in ischemic brain tissue repair and remodeling, we infused recombinant BMP7 or noggin into the ipsilateral ventricle of mice for 2weeks starting 2weeks after transient middle cerebral artery occlusion (MCAO). Four weeks after MCAO, we measured ischemic brain volume, functional recovery, and molecules related to neurogenesis and angiogenesis such as synaptophysin, GAP-43, and VEGF. Noggin-treated mice but not BMP7-treated mice showed preserved ipsilateral brain volume and reduced neurological deficits compared with artificial cerebrospinal fluids (aCSF)-treated mice. Noggin treatment also decreased glial scar thickness, increased levels of GAP-43 and VEGF protein, and increased the number of Iba1-positive activated microglia in the ipsilateral brain. Furthermore, noggin treatment decreased M1 markers (IL-1β, TNF-α, IL-12, CCL2 and CD86) and increased M2 markers (IL-1ra, IL-10, arginase 1, CD206 and Ym1) of activated microglia, suggesting a shift from M1 to M2 phenotypes. These results suggest that noggin improves functional recovery from ischemic stroke and enhances alternatively activated microglia, thereby promoting tissue repair and remodeling.

Autocrine activation of canonical BMP signaling regulates PD-L1 and PD-L2 expression in human dendritic cells

Bone morphogenetic proteins (BMPs) are multifunctional growth factors regulating differentiation and proliferation in numerous systems including the immune system. Previously, we described that the BMP signaling pathway is functional in human monocyte-derived dendritic cells (MoDCs), which were found to express both the specific receptors and the Smad proteins required for signal transduction. In this study, we provide evidence that human MoDCs produce BMP-4 and that this production is increased over the maturation process as is BMP signal transduction. When DCs are matured in the presence of an inhibitor of the BMP pathway, the expression of the maturation markers PD-L1 and PD-L2 is reduced, while cytokine production is not affected. As a result, these mature DCs present an augmented ability to stimulate both T cells and NK cells. Eventually, the inhibition of BMP signaling during maturation causes a reduced expression of IRF-1, a transcription factor that positively regulates the expression of PD-L1 and PD-L2. The present study indicates that the BMP signaling pathway regulates PD-L1 and PD-L2 expression in human MoDCs during the maturation process, probably through the IRF-1 transcription factor, and also points out that the manipulation of BMP signaling might considerably improve the immunogenicity of MoDCs used in immunotherapy.

BMPR1B up-regulation via a miRNA binding site variation defines endometriosis susceptibility and CA125 levels

Background

Bone morphogenetic protein receptor I B (BMPR1B) is a transmembrane receptor mediating TGF-β signal transduction. Recent studies indicate a tumor suppressor role for BMPR1B in ovarian cancer. Polymorphism at BMPR1B 3′UTR within the miR-125b binding site alters its binding affinity toward the miRNA, which may result in insufficient post-transcriptional repression.

Methods

Single-nucleotide polymorphisms rs1970801, rs1434536, and rs11097457 near the miR-125b binding site in BMPR1B were genotyped by Taqman assay on 193 endometriosis patients and 202 healthy controls. BMPR1B and CA125 levels in ectopic endometrial tissues were evaluated by quantitative PCR and immunohistochemistry. Luciferase reporter assay was utilized to verify regulatory roles of BMPR1B 3′UTR with allelic variants of rs1434536 in a cell line model. Cell proliferation and migration were recorded, while expression of BMPR1B, CA125, glucocorticoid receptor (GCCR) and IL-1β were measured by quantitative PCR in endometrial cells transfected with wild-type or mutated miR-125b.

Results

This study found two endometriosis-associated SNPs, rs1434536 (P = 0.010) and rs1970801 (P = 0.0087), located within and next to a miR-125b binding site on BMPR1B. Interestingly, patients with homozygous variant alleles at rs1434536 showed significantly lower serum CA125 levels. Immunohistochemistry staining further confirmed inverse correlation between BMPR1B and CA125 levels in three rs1434536 genotypes. Cell assays demonstrated the variant allele of rs1434536 up-regulating BMPR1B at both mRNA and protein levels, which negatively correlated with CA125 and IL-1β levels. Disruption of the binding between miR-125b and BMPR1B hampered abnormal cell proliferation.

Conclusions

SNPs of BMPR1B within and next to the miR-125b binding site manifested strong correlation with endometriosis development in a Taiwanese cohort. Disrupting the binding of miR-125b toward BMPR1B would increase protein expression, diminishing abnormal cell proliferation as well as serum and cellular CA125 levels. Genetic variation at the miR-125b binding site may play functional roles to protect against endometriosis progression.

Bone Morphogenetic Proteins stimulate mammary fibroblasts to promote mammary carcinoma cell invasion

Bone Morphogenetic Proteins (BMPs) are secreted cytokines that are part of the Transforming Growth Factor β (TGFβ) superfamily. BMPs have been shown to be highly expressed in human breast cancers, and loss of BMP signaling in mammary carcinomas has been shown to accelerate metastases. Interestingly, other work has indicated that stimulation of dermal fibroblasts with BMP can enhance secretion of pro-tumorigenic factors. Furthermore, treatment of carcinoma-associated fibroblasts (CAFs) derived from a mouse prostate carcinoma with BMP4 was shown to stimulate angiogenesis. We sought to determine the effect of BMP treatment on mammary fibroblasts. A large number of secreted pro-inflammatory cytokines and matrix-metallo proteases (MMPs) were found to be upregulated in response to BMP4 treatment. Fibroblasts that were stimulated with BMP4 were found to enhance mammary carcinoma cell invasion, and these effects were inhibited by a BMP receptor kinase antagonist. Treatment with BMP in turn elevated pro-tumorigenic secreted factors such as IL-6 and MMP-3. These experiments demonstrate that BMP may stimulate tumor progression within the tumor microenvironment.

Bone Morphogenetic Proteins stimulate mammary fibroblasts to promote mammary carcinoma cell invasion

Bone Morphogenetic Proteins (BMPs) are secreted cytokines that are part of the Transforming Growth Factor β (TGFβ) superfamily. BMPs have been shown to be highly expressed in human breast cancers, and loss of BMP signaling in mammary carcinomas has been shown to accelerate metastases. Interestingly, other work has indicated that stimulation of dermal fibroblasts with BMP can enhance secretion of pro-tumorigenic factors. Furthermore, treatment of carcinoma-associated fibroblasts (CAFs) derived from a mouse prostate carcinoma with BMP4 was shown to stimulate angiogenesis. We sought to determine the effect of BMP treatment on mammary fibroblasts. A large number of secreted pro-inflammatory cytokines and matrix-metallo proteases (MMPs) were found to be upregulated in response to BMP4 treatment. Fibroblasts that were stimulated with BMP4 were found to enhance mammary carcinoma cell invasion, and these effects were inhibited by a BMP receptor kinase antagonist. Treatment with BMP in turn elevated pro-tumorigenic secreted factors such as IL-6 and MMP-3. These experiments demonstrate that BMP may stimulate tumor progression within the tumor microenvironment.

BMP-6 in renal cell carcinoma promotes tumor proliferation through IL-10-dependent M2 polarization of tumor-associated macrophages

Dysregulated bone morphogenetic proteins (BMP) may contribute to the development and progression of renal cell carcinoma (RCC). Herein, we report that BMP-6 promotes the growth of RCC by interleukin (IL)-10-mediated M2 polarization of tumor-associated macrophages (TAM). BMP-6-mediated IL-10 expression in macrophages required Smad5 and STAT3. In human RCC specimens, the three-marker signature BMP-6/IL-10/CD68 was associated with a poor prognosis. Furthermore, patients with elevated IL-10 serum levels had worse outcome after surgery. Together, our results suggest that BMP-6/macrophage/IL-10 regulates M2 polarization of TAMs in RCC.

Pathways for bone loss in inflammatory disease

Chronic inflammation including autoimmune disease is an important risk factor for the development of osteoporosis. Receptor activator of nuclear factor-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) play a central role in osteoclast differentiation and function, and the molecular pathways by which M-CSF and RANKL induce osteoclast differentiation have been analyzed in detail. Proinflammatory cytokines directly or indirectly regulate osteoclastogenesis and bone resorption providing a link between inflammation and osteoporosis. Tumor necrosis factor-α, interleukin (IL)-1, IL-6, and IL-17 are the most important proinflammatory cytokines triggering inflammatory bone loss. Inhibition of these cytokines has provided potent therapeutic effects in the treatment of diseases such as rheumatoid arthritis. Further investigation is needed to understand the pathophysiology and to develop new strategies to treat inflammatory bone loss. This review summarizes new data on inflammatory bone loss obtained in 2011.