[Ossification after transplantation of model cartilage in the rat patella]

The cartilage model of the rat's patella constitutes a formation susceptible of inducing ossification, following its transplantation in a variety of sites (muscle, thyroïd, testis, ovary, anterior chamber of the eye, etc.), including those considered inappropriate in other experiments of induced ossification (liver, kidney). So we have an experimental model allowing the influence on the osteogenesis of various factors, local or general, natural or experimental, to be studied. Ossification occurs in this model only in cases of histocompatibility between donor and recipient. It is constant after autotransplantation or isotransplantation. It is never seen after heterotransplantation. In cases of homotransplantation its frequency varies: this is not influenced by the technical conditions of implantation but by tissue compatibility and the age of the animals giving and receiving. A private perichondrium cartilage retains its osteogenic potency. A cartilage killed by alcohol or cold no longer demonstrates its osteoformative capacities, even when put into contact with a living cartilage. Our findings are difficult to reconcile with the hypotheses invoking the osteogenic potency of the periosteum, or the intervention of substances either inducing osteoformation or inhibiting vascular invasion, for the explanation of endochondral ossification. However, they lead one to the opinion that chondrocytes play an active role in its release.