In vitro elastic fiber formation by aggregated arotic cells of newborn rabbits

Cells isolated enzymatically from the aortas of newborn rabbits were aggregated and grown in organ culture. Bundles of microfibrils, some of them with an amouphous core (elastin), were evident in 3-day-old aggregates. Furthermore, droplets of elastin surrounded by darker dots and short filaments, corresponding to the elastic units were observed. In 6-day-old aggregates the number of elastic fibers composed of bundles of microfibrils with deposited elastin increased. Elastic elements which probably resulted from a coalescence of elastic units were also present. These two ways of elastic fiber formation in aggregates are compared with those described in papers on aortic development.