Limb motility and ambulation as mechanical cues 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 for ambulation. In doing so, they resist high mechanical loads. Muscle contraction during embryonic development is required for continued tendon growth and differentiation. Defining the types and magnitudes of loads that act on tendons during the early postnatal periods is quite difficult. This study aimed to reveal whether limb motility and spontaneous physical behaviors in the postnatal phase work as mechanical cues for tendon development, leading to mechanobiological phenomena during postnatal phases in the murine model. Neonatal mice showed gradual limb motility, rollover function, and ambulation patterns during early postnatal phases. Tendons showed lengthening, decreasing the cell density and nuclear roundness concurrently. Scx and Tnmd gene expression showed a tendency to increase with time as well. This study presented a comprehensive time course of limb movement and ambulation with corresponding tendon growth during the postnatal phase. Our chronological analysis of the relationship between changing limb loading and tendon development provides a foundation for future work focused on mechanobiology in tendon development.