Etanercept administration to neonatal SH3BP2 knock-in cherubism mice prevents TNF-α-induced inflammation and bone loss

The bone phenotype associated with cherubism is independent of Caspase-1-dependent inflammasome activation in the mouse

Cherubism is a rare genetic disorder caused by SH3BP2 mutations. This sterile autoinflammatory disease is characterized by jaw osteolysis, in which bone tissue is replaced by multinucleated giant cells containing fibrous tissue. The cherubism mouse model (Sh3bp2 KI) is characterized by systemic bone loss as well as inflammatory phenotypes induced and maintained by TNFα. IL-1β, produced by the NRLP3 inflammasome through recruitment of Caspase-1, is involved in the development of sterile autoinflammatory disease. We previously reported a cherubism patient with elevated serum IL-1β, and cherubism mice also have elevated serum IL-1β levels. Thus, we wanted to disentangle the role of IL-1β in cherubism. To that end, we deleted Caspase-1 in Sh3bp2 KI mice to tamp down IL-1β production. However, deleting Caspase-1 did not rescue the systemic bone and inflammatory phenotypes.

Silencing of SH3BP2 Inhibits Microglia Activation Via the JAK/STAT Signaling in Spinal Cord Injury Models

The purpose of our study was to investigate the expression of SH3 domain-binding protein 2 (SH3BP2) in spinal cord injury (SCI) rats and lipopolysaccharide (LPS)-induced microglia, and explored its impact as well as potential mechanism. We examined the level of SH3BP2 in SCI rats using GEO data, immunofluorescence co-staining, qRT-PCR and western blotting. Next, we constructed a rat model with SH3BP2 silencing by injecting LV-shSH3BP2 into the injury site of SCI rats, and then evaluated its neurological outcome, functional recovery, M1 polarization and neuroinflammation by Basso-Beattie-Bresnahan (BBB) score, inclined plane test, Nissl staining and hematoxylin-eosin (H&E). The SH3BP2-related signaling pathway was predicted by KEGG analysis in GSE45006 dataset. BV2 microglial cells and primary microglia were incubated with LPS, and then measured its activation and inflammation by qRT-PCR, western blotting and immunofluorescence. Further complement experiments were performed to explore the molecular mechanisms of SH3BP2. The expression of SH3BP2 was increased in the spinal dorsal horn tissues of SCI rats and LPS-induced microglia. Silencing of SH3BP2 improved neurological outcomes and functional recovery, attenuated neuroinflammation and microglia polarization in SCI rats. Additionally, the JAK/STAT pathway was regulated by SH3BP2. Silencing of SH3BP2 inhibited LPS-induced microglia inflammation and activation, decreased the phosphorylation levels of JAK and STAT. Silencing of SH3BP2 attenuated SCI by regulating the JAK/STAT pathway to inhibit the activation of microglia.

Suppression of TNF-α activity by immobilization rescues Mkx expression and attenuates tendon ossification in a mouse Achilles tenotomy model

Traumatic heterotopic ossification is a condition in which extraskeletal bone formation occurs in soft tissues after injury. It most commonly occurs in patients who had major orthopedic surgery and in those with severe extremity injuries. The lesion causes local pain and can impair motor function of the affected limb, but there is currently no established prophylaxis or treatment for this condition. In this study, we show that immobilization at an early stage of the inflammatory response after injury can attenuate ossification formation in a murine Achilles tenotomy model. Gene expression analysis revealed a decrease in the expression of Tnf and an increase in the expression of Mkx, which encodes one of the master regulators of tendon differentiation, Mohawk. Notably, we found that TNF-α suppressed the expression of Mkx transcripts and accelerated the osteogenic differentiation of tendon-derived mesenchymal stem cells (MSCs), suggesting that TNF-α acts as a negative regulator of Mkx transcription. Consistent with these findings, pharmaceutical inhibition of TNF-α increased the expression of Mkx transcripts and suppressed bone formation in this mouse model. These findings reveal the previously unrecognized involvement of TNF-α in regulating tendon MSC fate through suppression of Mkx expression and suggest that TNF-α is a potential target for preventing traumatic heterotopic ossification.

Nonfamilial cherubism in a 6-month-old infant: a case report

BACKGROUND

Cherubism is known as a very rare autosomal dominant familial disorder of childhood caused by a mutation in the SH3BP2 gene on 4p16.3. It has not yet been observed at birth and is usually diagnosed in children aged 2-7. Here, we present a non-hereditary case of cherubism at a very early age.

CASE PRESENTATION

A 6-month-old girl presented with bilateral progressive jaw enlargement. On physical examination, bilateral asymmetrical jaw enlargement, predominantly on the left side, and some enlarged, non-tender, mobile submandibular lymph nodes were detected. No other abnormality was observed. Further investigations with radiology suggested cherubism and Burkitt's lymphoma as differential diagnoses. Later on, histopathologic evaluations were suggestive of cherubism. No surgical interventions were indicated, and the child is on regular follow-ups.

CONCLUSION

Non-hereditary Cherubism, despite scarcity, can present in children below two years of age, even as early as the beginning of primary dentition. Accurate and swift diagnosis is essential to avert physical and psychological complications. Our case report shows the importance of keeping cherubism in mind as a differential diagnosis of bone disease, even in children under a year old, and the value of interdisciplinary collaboration in dealing with rare genetic disorders.

Imatinib has minimal effects on inflammatory and osteopenic phenotypes in a murine cherubism model

OBJECTIVE

Cherubism is a genetic disorder characterised by bilateral jawbone deformation. The associated jawbone lesions regress after puberty, whereas severe cases require surgical treatment. Although several drugs have been tested, fundamental treatment strategies for cherubism have not been established. The effectiveness of imatinib has recently been reported; however, its pharmaceutical mechanism remains unclear. In this study, we tested the effects of imatinib using a cherubism mouse model.

METHODS

We used Sh3bp2 P416R cherubism mutant mice, which exhibit systemic organ inflammation and osteopenia. The effects of imatinib were determined using primary bone marrow-derived macrophages. Imatinib was administered intraperitoneally to the mice, and serum tumour necrosis factor-α (TNFα), organ inflammation and bone properties were examined.

RESULTS

The cherubism mutant macrophages produced higher levels of TNFα in response to lipopolysaccharide compared to wild-type macrophages, and imatinib did not significantly suppress TNFα production. Although imatinib suppressed osteoclast formation in vitro, administering it in vivo did not suppress organ inflammation and osteopenia.

CONCLUSION

The in vivo administration of imatinib had a minimal therapeutic impact in cherubism mutant mice. To establish better pharmaceutical interventions, it is necessary to integrate new findings from murine models with clinical data from patients with a definitive diagnosis of cherubism.

Tumour necrosis factor plays a deleterious role in the pathogenesis of chikungunya virus infection

Arthralgia is a hallmark of chikungunya virus (CHIKV) infection and can be very debilitating and associated with a robust local inflammatory response. Many pathophysiological aspects associated with the disease remain to be elucidated. Here, we describe a novel model of CHIKV infection in immunocompetent mice and evaluate the role of tumour necrosis factor in the pathogenesis of the disease. C57BL/6 wild type (WT) or TNF receptor 1 deficient (TNFR1^-/- ) mice were inoculated with 1 × 10⁶ PFU of CHIKV in the paw. Alternatively, etanercept was used to inhibit TNF in infected WT mice. Hypernociception, inflammatory and virological analysis were performed. Inoculation of CHIKV into WT mice induced persistent hypernociception. There was significant viral replication in target organs and local production of inflammatory mediators in early time-points after infection. CHIKV infection was associated with specific humoral IgM and IgG responses. In TNFR1^-/- mice, there was a decrease in the hypernociception threshold, which was associated with a milder local inflammatory response in the paw but delayed viral clearance. Local or systemic treatment with etanercept reduced CHIKV-induced hypernociception. This is the first study to describe hypernociception, a clinical correlation of arthralgia, in immunocompetent mice infected with CHIKV. It also demonstrates the dual role of TNF in contributing to viral clearance but driving tissue damage and hypernociception. Inhibition of TNF may have therapeutic benefits but its role in viral clearance suggests that viral levels must be monitored in CHIKV-infected patients and that TNF inhibitors should ideally be used in combination with anti-viral drugs.

Etanercept prevents TNF-α mediated mandibular bone loss in FcγRIIb-/- lupus model

Patients with systemic lupus erythematosus are at increased risk for alveolar bone loss due to periodontitis possibly as a result of a pathogenic immune response to oral bacteria and inflammation. The aim of the present study was to investigate whether an anti-TNF-α antagonist could prevent mandibular bone loss in the FcγRIIb^-/- mouse model of lupus. Mice lacking FcγRIIb had decreased cancellous and cortical bone volume at 6 months of age. Etanercept increased cancellous but not cortical bone volume in WT and increased both cancellous bone volume and cortical thickness in FcγRIIb-deficient mice. FcγRIIb deficiency decreased mRNA levels for osteoblast marker genes, Osx, Col1a1 and Alp without any change in osteoclast marker genes. Etanercept increased Osx, Alp, and Ocn in both WT and FcγRIIb^-/- mice. Osteoclast marker genes including TNF-α, Trap and RANKL/OPG ratio was decreased in WT. Serum markers of proinflammatory cytokines, TNF-α, IFNγ, IL-6, and IL-17A, were increased in FcγRIIb^-/- mice and etanercept antagonized these effects in FcγRIIb^-/- mice. Etanercept increased serum PTH levels in the FcγRIIb^-/- mouse model of lupus. Our results suggest that deletion of FcγRIIb induces osteopenia by increasing the level of proinflammatory cytokines. Etanercept is effective in preventing mandibular bone loss in FcγRIIb^-/- mice, suggesting that anti-TNF-α therapy may be able to ameliorate mandibular bone loss in SLE patients with periodontitis.

Adjuvant Alendronic Acid in the Management of Severe Cherubism: A Case Report and Literature Review

Cherubism is a rare disease of the jaws characterized by bilateral symmetrical painless expansion of the mandible and maxilla. In extreme cases, larger lesions can become exophytic and have profound functional and esthetic implications. Several pharmacologic agents have been trialed in the treatment of cherubism with variable success reported. Bisphosphonates have not been significantly studied in this setting. We present a case where oral alendronic acid was used as an adjuvant treatment after surgical debulking of the maxilla in a 13-year-old boy with a severe case of cherubism.

Lupus-like Disease in FcγRIIB-/- Mice Induces Osteopenia

Osteoporotic fracture is a major cause of morbidity in patients with systemic lupus erythematosus (SLE). Mice lacking Fc gamma receptor IIb (FcγRIIB) spontaneously develop lupus-like disease or SLE at 6-month-old. The aim of this study was to investigate whether FcγRIIB deletion induces osteopenia. μCT analysis indicated that deleting FcγRIIB did not affect cancellous bone microarchitecture in 3-month-old mice in which SLE had not yet developed. However, 6- and 10-month-old FcγRIIB^−/− males that developed an SLE-like phenotype were osteopenic and FcγRIIB deletion resulted in decreased cancellous bone volume. Histomorphometry confirmed a significant decrease in cancellous bone volume in 6- and 10-month-old FcγRIIB^−/− males. The osteoclast number was increased without any change in osteoblast number. In vitro assays indicated that deleting FcγRIIB increased osteoclast differentiation while alkaline phosphatase activity and mineralization were unaltered. These changes were associated with increases in steady-state mRNA levels for the osteoclast marker genes Trap and Ctsk. Moreover, FcγRIIB^−/− mice had higher level of serum TNFα, a proinflammatory cytokine. A soluble TNFα receptor, etanercept, prevented cancellous bone loss in FcγRIIB^−/− mice. Our results indicate that FcγRIIB indirectly regulates cancellous bone homeostasis following SLE development. FcγRIIB deletion induces inflammatory bone loss due to increased TNFα-mediated bone resorption without any change in bone formation in mice with SLE-like syndrome.

Tankyrase (PARP5) Inhibition Induces Bone Loss through Accumulation of Its Substrate SH3BP2

There is considerable interest in tankyrase because of its potential use in cancer therapy. Tankyrase catalyzes the ADP-ribosylation of a variety of target proteins and regulates various cellular processes. The anti-cancer effects of tankyrase inhibitors are mainly due to their suppression of Wnt signaling and inhibition of telomerase activity, which are mediated by AXIN and TRF1 stabilization, respectively. In this review, we describe the underappreciated effects of another substrate, SH3 domain-binding protein 2 (SH3BP2). Specifically, SH3BP2 is an adaptor protein that regulates intracellular signaling pathways. Additionally, in the human genetic disorder cherubism, the gain-of-function mutations in SH3BP2 enhance osteoclastogenesis. The pharmacological inhibition of tankyrase in mice induces bone loss through the accumulation of SH3BP2 and the subsequent increase in osteoclast formation. These findings reveal the novel functions of tankyrase influencing bone homeostasis, and imply that tankyrase inhibitor treatments in a clinical setting may be associated with adverse effects on bone mass.

A Paradigm Shift in the Management of Cherubism? A Preliminary Report Using Imatinib

Cherubism is an autosomal-dominant inherited mutation in the SH3BP2 gene on chromosome 4p16.3. It is characterized by bilateral symmetric fibro-osseous lesions that are limited to the maxilla and mandible. The lesions present in early childhood and typically spontaneously involute after puberty. Current standard practice is to reserve surgery for symptomatic or severely disfiguring cases. This report presents 3 patients with cherubism who exhibited marked reduction in tumor size with imatinib, a tyrosine kinase inhibitor. Treatment was well tolerated, with few side effects.

Risk Assessment of Etanercept in Mice Chronically Infected With Toxoplasma gondii

Toxoplasma gondii (T. gondii) is a zoonotic parasite that severely harms the health of the host. The cysts of T. gondii can reactivate from bradyzoites to tachyzoites, if the individual develops low or defective immunity, causing lethal toxoplasmosis. The host resists T. gondii infection by mediating Th1-type cellular immunity to generate pro-inflammatory cytokines. Tumor necrosis factor (TNF) is an important pro-inflammatory cytokine, which can induce lysosomal fusion of parasitophorous vacuole (PV) to kill parasites. Etanercept is a soluble TNF receptor fusion protein, which is widely used clinically to cure autoimmune diseases. The effects and specific molecular mechanisms of etanercept treatment on patients co-infected with autoimmune diseases and chronic toxoplasmosis are rarely reported. In our study, a mouse model of chronic infection with T. gondii and murine macrophages RAW264.7 cells infected with T. gondii were employed to investigate the impact of etanercept on the status of chronic infection. The cytokines levels and a series of phenotypic experiments in vivo and in vitro were measured. In the present study, the expression levels of TNF, IL-1β, and IL-6 were decreased and the brain cysts number was increased in mice chronically infected with T. gondii after being treated with etanercept. In vivo experiments confirmed that etanercept caused a decrease in the immune levels of the mice and activated the brain cysts, which would lead to conversion from chronic infection to acute infection, causing severe clinical and pathological symptoms. Murine macrophages RAW264.7 cells were pretreated with etanercept, and then infected with T. gondii. In vitro experiments, the expression levels of cytokines were decreased, indicating that etanercept could also reduce the cells’ immunity and promote the transformation of bradyzoites to tachyzoites, but did not affect the intracellular replication of tachyzoites. In summary, etanercept treatment could activate the conversion of bradyzoites to tachyzoites through reducing host immunity in vivo and in vitro. The results obtained from this study suggest that the use of etanercept in patients co-infected with autoimmune diseases and chronic toxoplasmosis may lead to the risk of activation of chronic infection, resulting in severe acute toxoplasmosis.

Second-Generation SYK Inhibitor Entospletinib Ameliorates Fully Established Inflammation and Bone Destruction in the Cherubism Mouse Model

Cherubism is a craniofacial disorder characterized by maxillary and mandibular bone destruction. Gain-of-function mutations in the SH3-domain binding protein 2 (SH3BP2) are responsible for the excessive bone resorption caused by fibrous inflammatory lesions. A homozygous knock-in (KI) mouse model for cherubism (Sh3bp2^KI/KI ) develops autoinflammation resulting in systemic bone destruction. Although administration of the TNF-α blocker etanercept to neonatal Sh3bp2^KI/KI mice prevented the disease onset, this therapy was not effective for adult Sh3bp2^KI/KI mice or human cherubism patients who already had lesions. Because genetic ablation of spleen tyrosine kinase (SYK) in myeloid cells rescues Sh3bp2^KI/KI mice from inflammation, we examined whether SYK inhibitor administration can improve fully developed cherubism symptoms in adult Sh3bp2^KI/KI mice. Entospletinib (GS-9973) was intraperitoneally injected into 10-week-old Sh3bp2^KI/KI mice every day for 6 weeks. Treatment with GS-9973 improved facial swelling and histomorphometric analysis of lung and liver tissue showed that GS-9973 administration significantly reduced inflammatory infiltrates associated with decreased levels of serum TNF-α. Micro-computed tomography (μCT) analysis showed that GS-9973 treatment reduced bone erosion in mandibles, calvariae, and ankle and elbow joints of Sh3bp2^KI/KI mice compared to Sh3bp2^KI/KI mice treated with dimethyl sulfoxide (DMSO). Taken together, the results demonstrate that administration of the SYK inhibitor ameliorates an already established cherubism phenotype in mice, suggesting that pharmacological inhibition of SYK may be a treatment option for cherubism patients with active disease progression. © 2018 American Society for Bone and Mineral Research.

Rescue of a cherubism bone marrow stromal culture phenotype by reducing TGFβ signaling

We utilized a bone marrow stromal culture system to investigate changes in TGFβ signaling in a mouse model for cherubism (Sh3bp2^KI/KI). Interestingly, bone marrow cultures derived from cherubism mice not only displayed impaired osteoblast differentiation, but also had spontaneous osteoclast formation. PAI1, a target gene of TGFβ signaling, was elevated 2-fold in cherubism CD11b^-,CD45^- cells compared to wild type cells, while the expression of BAMBI, an inhibitor of TGFβ signaling, was down-regulated. We also discovered that treatment of cherubism cultures with antagonists of the TGFβ signaling pathway could largely rescue osteoblast differentiation and markedly reduce spontaneous osteoclast formation. Treatment with the type I TGFβ receptor small molecule inhibitor SB505124 increased osteoblast reporter gene Col1a1-2.3 expression 24-fold and increased the expression of osteoblast gene markers Osterix (Sp7) 25-fold, Bone Sialoprotein (BSP) 7-fold, Osteocalcin (Bglap1) 100-fold, and Dentin Matrix Protein 1 (DMP1) 35-fold. In contrast, SB505124 treatment resulted in a significant reductions in osteoclast number and size. Gene expression analyses for RANKL, a positive regulator of osteoclast formation was 2.5-fold higher in osteoblast cultures derived from Sh3bp2^KI/KI mice compared to wild type cultures, whereas OPG, an inhibitor of RANKL was 5-fold lower. However, SB505124 treatment reduced RANKL almost back down to wild type levels, while increasing OPG expression. Our studies also implicate a role for TGFβ ligands in the etiology of cherubism. Blocking of TGFβ ligands with the monoclonal antibody 1D11 increased Col1a1-2.3 reporter expression 4-fold and 13-fold in cultures derived from Sh3bp2^KI/+ and Sh3bp2^KI/KI mice, respectively. Serum levels of latent TGFβ1 were also 2-fold higher in SH3BP2^KI/KI mice compared to wild type littermates. Taken together, these studies provide evidence that elevated levels of TGFβ signaling may contribute to the disease phenotype of cherubism and a reduction in pathway activity may be an effective therapeutic approach to treat this rare disease.

Inhibiting tumor necrosis factor-alpha diminishes desmoplasia and inflammation to overcome chemoresistance in pancreatic ductal adenocarcinoma

Background

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common cancer death reasons. Anti-tumor necrosis factor-alpha (TNF-α) antibodies have shown promising effects in PDAC pre-clinical models. However, the prognostic values of TNF-α, underlying mechanisms by which anti-TNF-α treatments inhibit PDAC, and potential synergistic effects of anti-TNF-α treatments with chemotherapy are still unclear.

Results and Methods

To identify the targeting values of TNF-α in PDAC, we measured TNF-α expression in different stages of PDAC initiation and evaluated its prognostic significance in a pancreatic cancer cohort. We found that TNF-α expression elevated in PDAC initiation process, and high expression of TNF-α was an independent prognostic marker of poor survival. We further evaluated anti-tumor effects of anti-TNF-α treatments in PDAC. Anti-TNF-α treatments resulted in decreased cell viability in both PDAC tumor cells and pancreatic satellite cells in similar dose in vitro. In vivo, anti-TNF-α treatments showed effects in reducing desmoplasia and the tumor promoting inflammatory microenvironment in PDAC. Combination of anti-TNF-α treatments with chemotherapy partly overcame chemoresistance of PDAC tumor cells and prolonged the survival of PDAC mouse model.

Conclusions

In conclusion, our findings indicated that TNF-α in PDAC can be a prognostic and therapeutic target. Inhibition of TNF-α synergized with chemotherapy in PDAC resulted in better pre-clinical responses via killing tumor cells as well as diminishing desmoplasia and inflammation in PDAC tumor stroma.

Expression of the mRNA stability regulator Tristetraprolin is required for lactation maintenance in the mouse mammary gland

Tristetraprolin (TTP), an mRNA-binding protein that negatively controls levels of inflammatory factors, is highly expressed in the lactating mouse mammary gland. To determine the biological relevance of this expression profile, we developed bi-transgenic mice in which this protein is specifically down-regulated in the secretory mammary epithelium in the secretory mammary epithelium during lactation. Our data show that TTP conditional KO mice produced underweight litters, possibly due to massive mammary cell death induced during lactation without the requirement of additional stimuli. This effect was linked to overexpression of inflammatory cytokines, activation of STAT3 and down-regulation of AKT phosphorylation. Importantly, blocking TNFα activity in the lactating conditional TTP KO mice inhibited cell death and similar effects were observed when this treatment was applied to wild-type animals during 48 h after weaning. Therefore, our results demonstrate that during lactation TTP wards off early involution by preventing the increase of local inflammatory factors. In addition, our data reveal the relevance of locally secreted TNFα for triggering programmed cell death after weaning.

Splenomegaly, myeloid lineage expansion and increased osteoclastogenesis in osteogenesis imperfecta murine

Osteogenesis imperfecta (OI) is a disease caused by defects in type I collagen production that results in brittle bones. While the pathology is mainly caused by defects in the osteoblast lineage, there is also elevated bone resorption by osteoclasts resulting in high bone turnover in severe forms of the disease. Osteoclasts originate from hematopoietic myeloid cells, however changes in hematopoiesis have not been previously documented in OI. In this study, we evaluated hematopoietic lineage distribution and osteoclast progenitor cell frequency in bone marrow, spleen and peripheral blood of osteogenesis imperfecta murine (OIM) mice, a model of severe OI. We found splenomegaly in all ages examined, and expansion of myeloid lineage cells (CD11b⁺) in bone marrow and spleen of 7-9week old male OIM animals. OIM spleens also showed an increased frequency of purified osteoclast progenitors. This phenotype is suggestive of chronic inflammation. Isolated osteoclast precursors from both spleen and bone marrow formed osteoclasts more rapidly than wild-type controls. We found that serum TNFα levels were increased in OIM, as was IL1α in OIM females. We targeted inflammation therapeutically by treating growing animals with murine TNFR2:Fc, a compound that blocks TNFα activity. Anti-TNFα treatment marginally decreased spleen mass in OIM females, but failed to reduce bone resorption, or improve bone parameters or fracture rate in OIM animals. We have demonstrated that OIM mice have changes in their hematopoietic system, and form osteoclasts more rapidly even in the absence of OI osteoblast signals, however therapy targeting TNFα did not improve disease parameters.

Modeling craniofacial and skeletal congenital birth defects to advance therapies

Craniofacial development is an intricate process of patterning, morphogenesis, and growth that involves many tissues within the developing embryo. Genetic misregulation of these processes leads to craniofacial malformations, which comprise over one-third of all congenital birth defects. Significant advances have been made in the clinical management of craniofacial disorders, but currently very few treatments specifically target the underlying molecular causes. Here, we review recent studies in which modeling of craniofacial disorders in primary patient cells, patient-derived induced pluripotent stem cells (iPSCs), and mice have enhanced our understanding of the etiology and pathophysiology of these disorders while also advancing therapeutic avenues for their prevention.

Fibrous dysplasia and cherubism

Fibrous dysplasia (FD) is a non-malignant fibro-osseous bony lesion in which the involved bone/bones gradually get converted into expanding cystic and fibrous tissue. The underlying defect in FD is post-natal mutation of GNAS1 gene, which leads to the proliferation and activation of undifferentiated mesenchymal cells arresting the bone development in woven phase and ultimately converting them into fibro-osseous cystic tissue. Cherubism is a hereditary form of fibrous dysplasia in which the causative factor is transmission of autosomal dominant SH3BP2 gene mutation. The disease may present in two distinct forms, a less severe and limited monostotic form, and a more aggressive and more widespread polyostotic form. Polyostotic form may be associated with various endocrine abnormalities, which require active management apart from the management of FD. Management of FD is not free from controversies. While total surgical excision of the involved area and reconstruction using newer micro-vascular technique is the only definitive treatment available from the curative point of view, but this can be only offered to monostotic and very few polyostotic lesions. In polyostotic varieties on many occasions these radical surgeries are very deforming in these slow growing lesions and so their indication is highly debated. The treatment of cranio-facial fibrous dysplasia should be highly individualized, depending on the fact that the clinical behavior of lesion is variable at various ages and in individual patients. A more conservative approach in the form of aesthetic recontouring of deformed bone, orthodontic occlusal correction, and watchful expectancy may be the more accepted form of treatment in young patients. Newer generation real-time imaging guidance during recontouring surgery adds to accuracy and safety of these procedures. Regular clinical and radiological follow up is required to watch for quiescence, regression or reactivation of the disease process. Patients must be warned and watched for any sign of nerve compression, especially visual impairment due to optic nerve compression. Rather than going for prophylactic optic canal decompression (which does more harm than good), optic nerve decompression should be done in symptomatic patients only, and preferably be done via minimal invasive endoscopic neuro-surgical approach than the conventional more morbid open craniotomy approach. There is growing research and possibilities that newer generation bisphosphonate medication may change the management scenario, as these medications show encouraging response in not only reducing the osteoclastic activity, but simultaneously also stimulating the osteoblastic and osteocytic activities. The explosion of genetic research and stem cell therapy may lead to better understanding and subsequently better treatment of FD in future.

Bone marrow transplantation improves autoinflammation and inflammatory bone loss in SH3BP2 knock-in cherubism mice

Cherubism (OMIM#118400) is a genetic disorder in children characterized by excessive jawbone destruction with proliferation of fibro-osseous lesions containing a large number of osteoclasts. Mutations in the SH3-domain binding protein 2 (SH3BP2) are responsible for cherubism. Analysis of the knock-in (KI) mouse model of cherubism showed that homozygous cherubism mice (Sh3bp2(KI/KI)) spontaneously develop systemic autoinflammation and inflammatory bone loss and that cherubism is a TNF-α-dependent hematopoietic disorder. In this study, we investigated whether bone marrow transplantation (BMT) is effective for the treatment of inflammation and bone loss in Sh3bp2(KI/KI) mice. Bone marrow (BM) cells from wild-type (Sh3bp2(+/+)) mice were transplanted to 6-week-old Sh3bp2(KI/KI) mice with developing inflammation and to 10-week-old Sh3bp2(KI/KI) mice with established inflammation. Six-week-old Sh3bp2(KI/KI) mice transplanted with Sh3bp2(+/+) BM cells exhibited improved body weight loss, facial swelling, and survival rate. Inflammatory lesions in the liver and lung as well as bone loss in calvaria and mandibula were ameliorated at 10weeks after BMT compared to Sh3bp2(KI/KI) mice transplanted with Sh3bp2(KI/KI) BM cells. Elevation of serum TNF-α levels was not detected after BMT. BMT was effective for up to 20weeks in 6-week-old Sh3bp2(KI/KI) mice transplanted with Sh3bp2(+/+) BM cells. BMT also ameliorated the inflammation and bone loss in 10-week-old Sh3bp2(KI/KI) mice. Thus our study demonstrates that BMT improves the inflammation and bone loss in cherubism mice. BMT may be effective for the treatment of cherubism patients.

SH3BP2 cherubism mutation potentiates TNF-α-induced osteoclastogenesis via NFATc1 and TNF-α-mediated inflammatory bone loss

Cherubism (OMIM# 118400) is a genetic disorder with excessive jawbone resorption caused by mutations in SH3 domain binding protein 2 (SH3BP2), a signaling adaptor protein. Studies on the mouse model for cherubism carrying a P416R knock-in (KI) mutation have revealed that mutant SH3BP2 enhances tumor necrosis factor (TNF)-α production and receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation in myeloid cells. TNF-α is expressed in human cherubism lesions, which contain a large number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells, and TNF-α plays a critical role in inflammatory bone destruction in homozygous cherubism mice (Sh3bp2(KI/KI) ). The data suggest a pathophysiological relationship between mutant SH3BP2 and TNF-α-mediated bone loss by osteoclasts. Therefore, we investigated whether P416R mutant SH3BP2 is involved in TNF-α-mediated osteoclast formation and bone loss. Here, we show that bone marrow-derived M-CSF-dependent macrophages (BMMs) from the heterozygous cherubism mutant (Sh3bp2(KI/+) ) mice are highly responsive to TNF-α and can differentiate into osteoclasts independently of RANKL in vitro by a mechanism that involves spleen tyrosine kinase (SYK) and phospholipase Cγ2 (PLCγ2) phosphorylation, leading to increased nuclear translocation of NFATc1. The heterozygous cherubism mutation exacerbates bone loss with increased osteoclast formation in a mouse calvarial TNF-α injection model as well as in a human TNF-α transgenic mouse model (hTNFtg). SH3BP2 knockdown in RAW264.7 cells results in decreased TRAP-positive multinucleated cell formation. These findings suggest that the SH3BP2 cherubism mutation can cause jawbone destruction by promoting osteoclast formation in response to TNF-α expressed in cherubism lesions and that SH3BP2 is a key regulator for TNF-α-induced osteoclastogenesis. Inhibition of SH3BP2 expression in osteoclast progenitors could be a potential strategy for the treatment of bone loss in cherubism as well as in other inflammatory bone disorders.

Cherubism with multiple dental abnormalities: a rare presentation

Cherubism is a progressive, hereditary fibro-osseous lesion exclusively affecting the jaw bones. It is caused by the abnormal functioning of osteoblasts and osteoclasts, leading to replacement of normal bone by cellular fibrous tissue and immature bone, which produces painless progressive growth of the jaw, with a round facial appearance. It was first described in 1933 by Jones as 'familial multilocular cystic disease of the jaws'. The term 'cherubism' was later coined to describe the rounded facial appearance resulting from jaw hypertrophy that was reminiscent of cherubs depicted throughout Renaissance art. The bony lesions generally occur at an early age, affect one or both jaws symmetrically, and grow progressively until puberty. Spontaneous regression is seen in most cases, although surgical re-contouring may be required for others for aesthetic reasons.

Enhanced TLR-MYD88 signaling stimulates autoinflammation in SH3BP2 cherubism mice and defines the etiology of cherubism

Cherubism is caused by mutations in SH3BP2. Studies of cherubism mice showed that tumor necrosis factor α (TNF-α)-dependent autoinflammation is a major cause of the disorder but failed to explain why human cherubism lesions are restricted to jaws and regress after puberty. We demonstrate that the inflammation in cherubism mice is MYD88 dependent and is rescued in the absence of TLR2 and TLR4. However, germ-free cherubism mice also develop inflammation. Mutant macrophages are hyperresponsive to PAMPs (pathogen-associated molecular patterns) and DAMPs (damage-associated molecular patterns) that activate Toll-like receptors (TLRs), resulting in TNF-α overproduction. Phosphorylation of SH3BP2 at Y183 is critical for the TNF-α production. Finally, SYK depletion in macrophages prevents the inflammation. These data suggest that the presence of a large amount of TLR ligands, presumably oral bacteria and DAMPs during jawbone remodeling, may cause the jaw-specific development of human cherubism lesions. Reduced levels of DAMPs after stabilization of jaw remodeling may contribute to the age-dependent regression.

SH3BP2 gain-of-function mutation exacerbates inflammation and bone loss in a murine collagen-induced arthritis model

Objective

SH3BP2 is a signaling adapter protein which regulates immune and skeletal systems. Gain-of-function mutations in SH3BP2 cause cherubism, characterized by jawbone destruction. This study was aimed to examine the role of SH3BP2 in inflammatory bone loss using a collagen-induced arthritis (CIA) model.

Methods

CIA was induced in wild-type (Sh3bp2^+/+) and heterozygous P416R SH3BP2 cherubism mutant knock-in (Sh3bp2^KI/+) mice, an SH3BP2 gain-of-function model. Severity of the arthritis was determined by assessing the paw swelling and histological analyses of the joints. Micro-CT analysis was used to determine the levels of bone loss. Inflammation and osteoclastogenesis in the joints were evaluated by quantitating the gene expression of inflammatory cytokines and osteoclast markers. Furthermore, involvement of the T- and B-cell responses was determined by draining lymph node cell culture and measurement of the serum anti-mouse type II collagen antibody levels, respectively. Finally, roles of the SH3BP2 mutation in macrophage activation and osteoclastogenesis were determined by evaluating the TNF-α production levels and osteoclast formation in bone marrow-derived M-CSF-dependent macrophage (BMM) cultures.

Results

Sh3bp2^KI/+ mice exhibited more severe inflammation and bone loss, accompanying an increased number of osteoclasts. The mRNA levels for TNF-α and osteoclast marker genes were higher in the joints of Sh3bp2^KI/+ mice. Lymph node cell culture showed that lymphocyte proliferation and IFN-γ and IL-17 production were comparable between Sh3bp2^+/+ and Sh3bp2^KI/+ cells. Serum anti-type II collagen antibody levels were comparable between Sh3bp2^+/+ and Sh3bp2^KI/+ mice. In vitro experiments showed that TNF-α production in Sh3bp2^KI/+ BMMs is elevated compared with Sh3bp2^+/+ BMMs and that RANKL-induced osteoclastogenesis is enhanced in Sh3bp2^KI/+ BMMs associated with increased NFATc1 nuclear localization.

Conclusion

Gain-of-function of SH3BP2 augments inflammation and bone loss in the CIA model through increased macrophage activation and osteoclast formation. Therefore, modulation of the SH3BP2 expression may have therapeutic potential for the treatment of rheumatoid arthritis.