Mechanical Force Works as a Biological Cue in Postnatal Murine Tendon Development

The musculoskeletal system provides structural stability and coordination to enable movement. Tendons have the essential role of efficiently transmitting force generated from muscle contraction to bone to enable ambulation. In doing so, they resist high external forces. In fact, muscle contraction during embryonic development is required to maintain tendon growth and differentiation. Nonetheless, defining the types and magnitudes of loads that act on tendons during embryonic and early postnatal periods is quite difficult. In this study, we aimed to define the physiologic limb movement and forces experienced during these stages in the murine model. We found that late-stage embryos had limited amniotic space, which attenuated limb movement. In the neonatal phase, physical ability, as measured by rollover function and locomotion, increased. These changes, which likely corresponded to increased forces applied to the tendons, corresponded with the expression of tenogenic markers during the embryo to postnatal phase. In particular, we found that the upregulation of Scx and Tnmd correlated with increased movement during the two weeks after birth. Our results help define the spatiotemporal role of mechanical force, including internal and external factors, in tendon growth and development. Highlights Assessed limb movement in amnion. Space limitation attenuated limb movement in the late-stage embryos. Defined the mechanical force from the limb’s physiological environment. Scx and Tnmd were upregulated synchronically with rollover function and locomotion. Mechanical forces may work as the cue of tendon development