Etanercept Administration to Neonatal SH3BP2 Knock-In Cherubism Mice Prevents TNF-α-induced Inflammation and Bone Loss

摘要

Cherubism is a genetic disorder of the craniofacial skeleton caused by gain-of-function mutations in the signaling adaptor protein, SH3-domain binding protein 2 (SH3BP2). In a knock-in mouse model for cherubism, we previously demonstrated that homozygous mutant mice develop T/B cell-independent systemic macrophage inflammation leading to bone erosion and joint destruction. Homozygous mice develop multiostotic bone lesions while cherubism lesions in humans are limited to jawbones. We identified a critical role of TNF-α in the development of autoinflammation by creating homozygous TNF-α-deficient cherubism mutants, where systemic inflammation and bone destruction were rescued. In the current study, we examined whether postnatal administration of an anti-TNF-α antagonist can prevent or ameliorate the disease progression in cherubism mice. Neonatal homozygous mutants, where active inflammation has not yet developed, were treated with a high dose of etanercept (25 mg/kg, twice/week) for 7 weeks. Etanercept-treated neonatal mice showed strong rescue of facial swelling and bone loss in jaws and calvariae. Destruction of joints was fully rescued in the high dose group. Moreover, the high dose treatment group showed a significant decrease in lung and liver inflammatory lesions. However, inflammation and bone loss, which were successfully treated by etanercept administration recurred after etanercept discontinuation. No significant effect was observed in low dose- (0.5 mg/kg, twice/week) and vehicle-treated groups. In contrast, when 10-week-old cherubism mice with fully active inflammation were treated with etanercept for 7 weeks, even the high dose administration did not decrease bone loss, lung or liver inflammation. Taken together, the results suggest that anti-TNF-α therapy may be effective in young cherubism patients, if treated before the inflammatory phase or bone resorption occurs. Therefore, early genetic diagnosis and early treatment with anti-TNF-α antagonists may be able to prevent or ameliorate cherubism, especially in patients with a mutation in SH3BP2.