The skeletons of newborn mammals are soft and pliable because they are composed primarily of cartilage. During growth to adulthood, most cartilage is replaced by bone. The remaining cartilage, such as that found in the joints, does not readily regenerate, so joints deteriorate with age. By contrast, elasmobranch fish make cartilage throughout their lives. Marconi et al. studied the cartilaginous fish Leucoraja erinacea, or little skate, from embryo to adult and observed that progenitor cells that surround the cartilage skeleton are also present in the adult. These cells are induced to transform into chondrocytes after injury. Understanding cartilage repair in skates may offer inspiration for research into human joint repair.
eLife 9, e53414 (2020).