Growth of costochondral fragments transplanted from mature to young isogeneic rats.

Experiments were carried out to determine whether growth of costochondral grafts is associated with age-related humoral factors. Rib fragments containing either short (without germinative zone) or long (with proliferative and germinative zones) cartilaginous ends were excised from adult rats, and the sections transplanted across the interparietal suture in 10-day-old isogeneic rats. The animals with short cartilage transplants were killed 15 or 25 days later; those with long cartilage transplants 25 days postoperatively. Measurements on dry skulls with short transplants showed neurocranial width to be greater in the experimental rats than in the unoperated controls at 25 days, whereas 10 days later the difference was no longer significant. By the latter time, however, the neurocranium was significantly wider in the long cartilage group than in the other groups. It is suggested that the declining growth potential of the costal cartilages from the adult rats was reactivated when transplanted to younger animals, i.e., the growth of costochondral transplants is related to humoral factors.