Ear pinna growth and differentiation is conserved in murids and requires BMP signaling for chondrocyte proliferation.

Despite being a major target of reconstructive surgery, development of the ear pinna remains poorly studied. Here we provide a cellular characterization of late gestational and postnatal ear pinna development in two rodents and investigate the role of BMP5 in expansion and differentiation of auricular elastic cartilage. We find that ear pinna development is largely conserved between Mus musculus and the highly regenerative Acomys dimidiatus. The pattern of pre-cartilaginous cells is established early in development. These cells are specified into chondroblasts prior to ear unfolding and then undergo extensive proliferation prior to maturation. The elastic cartilage, connective tissue fibroblasts, dermal papilla and sheath cells, and adipocytes in the adult pinna are derived from cranial neural crest. Cellular analysis using the naturally occurring short ear mouse mutant shows that loss of BMP5 does not prevent specification of chondroblasts but impairs their proliferation. Finally, chondroblast proliferation remains impaired in the adult mid-distal ear pinna of these mutants. Together these data establish the developmental basis for differentiation of ear pinna tissues.