Difference in size of bone islands formed by isolated bone cells transplanted intramuscularly under various...

Bone cells isolated from the whole calvaria (2 x 10(6)) from either central or peripheral parts of parietal bones (1 x 10(6)) and from scapulas (2 x 10(6)) were allowed to adhere to devitalized calvarial bones in the number indicated in brackets and transplanted intramuscularly (supported transplants). Whole calvaria bone cells (2.4 or 8 x 10(6) cells per transplant) were also injected intramuscularly as free transplants. Calvarial cells produced solid bone islands with small intraosseous cavities, while bone formed by scapular cells contained large medullary spaces. The size of bone islands formed in transplants and the shortest distance between the neighbor islands were measured. The results of these measurements were similar in all groups of free transplants. The size of bone islands formed in supported transplants of cells from the whole calvaria or from central and peripheral parts of parietal bones was also roughly similar, but the shortest distance between islands was larger than in the free transplants. Furthermore, in these groups of transplants bone islands considerably larger than the largest islands in free transplants were present. Scapular bone cells formed islands much larger than those produced by calvarial cells. Bone islands formed by calvarial cells in free transplants were separated by bands of fibrous tissue which was absent in supported transplants. It appears that this tissue could limit growth and/or fusion of neighbor bone islands and in this manner influence their size. The population of transplanted scapular cells contained numerous stromal elements which could form an exclusion area inaccessible to local cells from the site of transplantation and thus favour formation of large bone islands within this area.