Pamidronate Administration During Pregnancy and Lactation Induces Temporal Preservation of Maternal Bone Mass in a Mouse Model of Osteogenesis Imperfecta

During pregnancy and lactation, the maternal skeleton undergoes significant bone loss through increased resorption to provide the necessary calcium supply to the developing fetus and suckling neonate. This period of skeletal vulnerability has not been clearly associated with increased maternal fracture risk, but these physiological conditions can exacerbate an underlying metabolic bone condition like osteogenesis imperfecta. Although bisphosphonates (BPs) are commonly used in postmenopausal women, there are cases where premenopausal women taking BPs become pregnant. Given BPs' long half-life, there is a need to establish how BPs affect the maternal skeleton during periods of demanding metabolic bone changes that are critical for the skeletal development of their offspring. In the present study, pamidronate- (PAM-) amplified pregnancy-induced bone mass gains and lactation-induced bone loss were prevented. This preservation of bone mass was less robust when PAM was administered at late stages of lactation compared with early pregnancy and first day of lactation. Pregnancy-induced osteocyte osteolysis was also observed and was unaffected with PAM treatment. No negative skeletal effects were observed in offspring from PAM-treated dams despite lactation-induced bone loss prevention. These findings provide important insight into (1) a treatment window for when PAM is most effective in preserving maternal bone mass, and (2) the maternal changes in bone metabolism that maintain calcium homeostasis crucial for fetal and neonatal bone development. © 2019 American Society for Bone and Mineral Research.