Rolvien T, Milovanovic P, Schmidt FN, et al. - Given that gradual bone loss occurs in correlation to immobilization as a result of long-term bed rest and that osteocytes represent the major mechanosensors in bone and translate mechanical into biochemical signals controlling bone remodeling, researchers here examined if immobilization modifies the characteristics of the osteocyte network in human cortical bone, via analyzing femoral diaphyseal bone specimens in immobilized female individuals. Further, they compared these with age-matched postmenopausal individuals with primary osteoporosis. Control groups comprised premenopausal and postmenopausal healthy individuals. They identified a declining rate of osteocyte density and canalicular density from premenopausal towards healthy postmenopausal and osteoporotic individuals with peculiar decreases in the immobilization group, while an inverse accumulation was observed in the number of hypermineralized lacunae. Findings thereby suggest that during immobilization, reduced osteocyte density and impaired connectivity are correlated with a specific bone loss pattern, exhibiting a phenotype clearly distinct from postmenopausal osteoporosis. Immobilization periods may result in a loss of survival signals for osteocytes, inducing bone loss that is even higher than in osteoporosis states, while osteocytic osteolysis remains absent.