Maternal exercise rescues fetal akinesia-impaired joint and bone development.

Fetal movements exert mechanical forces that shape the developing skeleton. Conditions that impair fetal movements can cause skeletal defects, but interventions are limited. Here, we show that maternal wheel running exercise regulates fetal skeletal development in mice. In wild-type fetuses, maternal exercise stimulated joint and bone morphogenesis. We reasoned that these effects occurred through either indirect maternofetal communication or direct mechanical stimulation of the fetus. Maternal exercise did not alter placental measures of nutrient transport. However, in the Splotch-delayed (Sp(d)) mouse model of fetal akinesia, which features intact maternofetal communication but lacks fetal movements, maternal exercise substantially rescued fetal akinesia-impaired joint and bone development and prevented disuse-induced resorption of the deltoid tuberosity. Further, direct mechanical stimulation of Sp(d) limbs explanted from systemic factors similarly stimulated joint morphogenesis. Together, these findings identify maternal exercise as a regulator of fetal skeletal development, providing a platform for studying skeletal developmental mechanobiology and suggesting potential therapeutic applications for fetuses with impaired movement.