The control of bone induction in soft tissues.

The induction of bone at the boundary of parenchymal organs has been studied using acid demineralized rib implants in rabbits. The induction of bone is usually confined to that portion of an implant protruding from such an organ though both scant cartilage induction and the induction of bone within the territory of parenchymal organs were seen on a few occasions. Neonatal splenectomy does not influence the inductive properties of bone matrix in muscle or other soft tissues. The inclusion of composite autografts of liver and acid demineralized bone in muscle results in a reduction in the induction rate. It is postulated that the parenchymal organs exclude osteoprogenitor cells and possibly blood-bone bone-marrow-derived osteoinductor releasing cells by some mechanism that is diffusable, thus preventing the initial inductive event. Composite grafts of matrix and muscle produce bone in these tissue, demonstrating that once bone cell differentiation by induction is initiated bone tissue develops even in spleen, liver and kidney parenchyma.