Mesenchymal regulation of mineralization and bone mineral density in the jaw skeleton

Proper bone mineral density (BMD) is crucial for skeletal function. Loss of BMD can lead to osteoporosis and fractures. From an evolutionary perspective, BMD helps couple morphology to the environment. For example, in aquatic mammals a higher BMD enables negative buoyancy during diving. BMD is governed by systemic and local factors throughout the life of an organism. On a cellular level, BMD is affected by osteoblasts, which secrete bone matrix that then mineralizes. During craniofacial development, osteoblasts are derived from neural crest mesenchyme (NCM). We use an avian chimeric system that exploits differences in morphology and maturation rates between quail and duck to investigate the role of NCM in establishing BMD. We unilaterally transplant quail NCM into duck, which maintains the host side as an internal control, and we analyze mineralization at the molecular and histological levels. We assess mineral deposition rates in quail, duck, and chimeric embryos by injecting fluorescent labels and by whole‐mount staining. We also measure BMD using DEXA. We find that duck have a slower rate and longer period of mineralization correlated with higher BMD, which is significant since duck use their bills for filter feeding and for diving. In chimeras, quail donor NCM alters the rate of mineral deposition. Thus, species‐specific differences in BMD have likely evolved through NCM‐mediated changes in mineralization. Grant Funding Source Departmental Startup