Is the bone mineral bioactive?

Regeneration of bone is the challenge faced by current technologies in tissue engineering, depending very much on bioactive scaffolds and on osteoprogenitors. The objective: of this study was to compare the bioactivity of decalcified bone matrix (DBM), non-decalcified bone matrix (MBM) or bone mineral (HABM) scaffolds for bone regeneration, using fresh bone marrow. Experimental methods: Scaffolds were prepared from femur diaphysis of DA rats by filing out all the cancelous bone including marrow, leaving a cortical bone cylinder. Each bone matrix cylinder was cut in half. Three types of cylinder bone matrices were prepared as following: (a) demineralized by 0.6N HCL (DBM), (b) deproteinization by hypochloride solution (HABM), (c) no treatment (MBM). After thorough washing with cold PBS, the scaffolds were placed in 70% alcohol and stored in cold. 18 two month old DA rats were donors for bone marrow transplantion into each scaffold. Another 18 DA rats were the hosts for subcutaneous implantation of scaffold cylinders filled with fresh marrow into the thoracic region, two scaffolds in each rat. 4 weeks after surgery the host rats were sacrificed and the scaffolds removed and put in formalin. Microradiography and histology was then performed to evaluate bone regeneration in the DBM,MBM and HABM scaffolds. Results: Micoradiography and histologic findings revealed that in the DBM and MBM scaffolds, trabecular bone filled most of the inner scaffold volume in more than 90% of these scaffolds, while no bone was found in the HABM scaffolds. In the HABM scaffolds granulation tissue was dominant. In conclusion: Our results showed that bone mineral is a poor scaffold to host osteoprogenitors and regenerate bone. Most probably the need for organic matrix componens in the scaffolds is essential for the bone regeneration cascade.