A novel stromal cell source of RANKL during sustained osteoclast activation in disuse osteoporosis

Disuse osteoporosis is a condition characterized by rapid bone loss induced by reduced mechanical loading on bones due to physical inactivity. An increase in osteoclast number is associated with bone loss in disuse osteoporosis. However, the mechanism of osteoclast induction in response to the lack of mechanical loading is not fully understood. To identify potential osteoclast-inducing cells under mechanical unloading conditions, we performed single-cell RNA sequencing (scRNA-seq) of bone and bone marrow cells from immobilized RANKL fate-mapping mice. Overall design: 8-week-old RANKL-fate mapping mice (Tnfsf11tTA/+; LC1; Rosa26LSL-tdTomato), treated with doxycycline from E0 to birth to suppress labeling during the fetal period, were subjected to hindlimb immobilization for 2 weeks (Control: n=4, Immobilized: n=6). CD45.2-Ter119-tdTomato+ cells were isolated from bone and bone marrow and pooled according to sample group, and scRNA-seq was performed.