Mechanical and Mesenchymal Mechanisms of Secondary Chondrogenesis

Strategies for treatment of skeletal malformation and injury benefit from an understanding of the molecular and biomechanical mechanisms of secondary cartilage development. We conduct a series of experiments using two species of quail and duck, which exhibit considerably different musculoskeletal morphologies. In duck, mandibular elevator muscles attach to a pronounced secondary cartilage on the jaw. An equivalent cartilage is absent in quail. We hypothesize that species‐specific differences in jaw morphology related to the mode of feeding, and a concomitant dissimilarity in the local mechanical environment promote formation of secondary cartilage in duck versus quail. We test our hypothesis by employing two experimental approaches. First, we alter the mechanical environment in embryonic duck by paralyzing skeletal muscles, or by inhibiting stretch‐activated Ca +2 channels. Second, we re‐pattern the duck jaw complex to resemble that found in quail by transplanting neural crest mesenchyme destined to form skeletal and connective tissues of the jaw. This mesenchyme is known to generate species‐specific pattern. Both experimental approaches inhibit secondary cartilage development, as evidenced by genetic and immunohistochemical data. We conclude that mesenchyme‐dependent changes in gene expression, musculoskeletal pattern, and mechanical forces control secondary cartilage induction. Grant Funding Source None