Heterotopically induced osteogenesis in osteopetrotic rat mutants. A preliminary report.

Heterotopic osteogenesis was induced in three groups of Fatty Orl-op strain of rats, i.e., osteopetrotic (op/op) mutants, op/op mutants cured by previous transplants of normal bone marrow, and phenotypically normal littermates. Allogenic decalcified bone matrix was used as inductor. The osteopetrotic mutants from heterotopic ossicles containing bone and bone marrow under the influence of inductor. After four weeks the signs of remodelling processes of induced bone tissue are observed: osteoclasts are found in the Howship lacunae, and bone marrow is formed in the spaces adjacent to the bone trabeculae. The induced bone marrow contains megakaryocytes, cells of the erythropoietic and granulopoietic lines as well as some infiltrating lymphocytes. The important finding is that the amount and the histological structure of bone tissue and bone marrow induced heterotopically in the osteopetrotic animals were similar to that observed in both control groups. It is concluded that 1) osteopetrotic mutants have the same potency to form heterotopic bone tissue under the influence of inductor as the control animals, and 2) remodelling processes in four-week-old, induced ossicles are normal and differ in this respect from defective rebuilding of the orthotopic bones of op/op hosts.