FAM20C restrains Caspase-1-dependent osteoblast pyroptosis in periodontal inflammation.

FAM20C is a secretory-pathway kinase required for mineralized-tissue homeostasis, and FAM20C-associated disease is accompanied by early periodontal inflammation. We investigated whether FAM20C limits Caspase-1-dependent osteoblast pyroptosis during periodontal inflammatory challenge. FAM20C/Fam20c expression was assessed by immunohistochemistry in ligature-induced mouse periodontitis and human gingiva and by RT-qPCR after lipopolysaccharide (LPS) exposure in four cell models. Stable Fam20c-deficient and Fam20c-overexpressing osteoblasts were analysed by transcriptomics, untargeted metabolomics, microscopy, immunofluorescence, RT-qPCR, Western blotting, ELISA and pharmacological Caspase-1 inhibition. FAM20C/Fam20c protein and mRNA increased in inflamed tissues, and LPS induced Fam20c expression. Fam20c deficiency increased ER-stress/Ca2+-homeostasis and inflammasome/pyroptosis module scores, reduced osteogenic gene expression and altered purine- and antioxidant-related metabolites. Fam20c loss enhanced LPS-induced cleaved Caspase-1, N-GSDMD and IL-1β/IL-18 release, whereas Fam20c overexpression attenuated these responses. Ac-YVAD-CMK reduced Caspase-1/GSDMD activation and cytokine release in Fam20c-deficient cells. These findings identify Fam20c as a determinant of osteoblast susceptibility to Caspase-1-dependent pyroptosis.