Bone growth was compared in six types of (beta-tricalcium phosphate) implants implanted in subcutaneous pouches or close to femoral head of male Wistar rats:
implants immersed in 0.9% sodium chloride solution (control implants), implants with the progenitor cells from femoral canal, implants immersed in inductive BMP-2 solution, implants with the progenitor cells from femoral canal + BMP-2 solution, implants immersed in inductive BMP-2 solution and implanted closed to the femoral head, implants immersed in inductive BMP-2 solution and implanted closed to the femoral head while leaving the femoral canal opened for better access of the femoral canal cells. Implants were removed 21 days after operation and dissected following principles of stereology. Presence of bone or cartilage or connective tissue was evaluated by hematoxylin eosin histochemistry. Results: Bone formation was only found in the implants where BMP-2 was introduced. However, no distinctive differences were found between the implants where cells and BMP-2 were introduced and between the implants where just BMP-2 was used. Percentages of the bone tissue out of all the implant were as follows: 0.0% in group 1, 1.2% in group 2, 32.4% in group 3, 42.4% in group 4, 44.4% in group 5 and, 54.9% in group 6. Differences in amount of bone tissue were statistically significant between groups 3 and 2, groups 3 and 1 and also between groups 1 and 2 (p=0.0013, p=0.0004 and p=0.0525 respectively). In the other cases, the differences between BMP-2 affected implants and implants without BMP-2 were even greater. We concluded that presence of osteoconductive matrix and introduction of an osteoinductive agent (e.g. BMP-2) are the main components of designing of bone tissue and introduction of exogenous bone cells is not as important as the first two in subcutaneous pouches or close to the hip joint.
