Disruption of circadian rhythms predisposes shift workers to many chronic conditions, including osteoporosis. However, the effects of disrupted circadian rhythms on bone remodeling remain largely unknown. Here, we show that one of the core circadian regulators PER1 inhibits osteoclastogenesis by upregulating genes involved in inflammation. The conditional knockout ofin osteoclasts and related cells resulted in decreased bone mass in the femurs of mice, along with increased osteoclasts and decreased osteoblasts. Osteoclastogenesis was also promoted bydepletion in vitro with 17 downregulated inflammatory genes. Eight of these genes were known to promote or inhibit osteoclastogenesis depending on the stage of osteoclastogenesis and the presence or absence of infection. The knockdown of three of these genes, which were involved in the inflammasome pathway, promoted osteoclastogenesis, mirroring the effects ofknockout and offering a mechanistic explanation for the-mediated inhibition of osteoclastogenesis. These results were not observed following the depletion of a paralog.knockout mice maintain general circadian rhythms, unlike arrhythmic/double knockout mice. This gives credence toas a selective target for therapeutic interventions without disrupting the circadian rhythms. This study uncovered a link between a circadian regulator and osteoclastogenesis in the broader context of osteoimmunology. Our findings may be mechanistically relevant to inflammatory bone diseases influenced by circadian rhythms, such as rheumatoid arthritis and osteoarthritis, as well as other bone diseases predisposed by chronic circadian disruption. Per1Per1Per1Per1Per2Per1Per1Per2Per1
Circadian Biology