The study evaluated the modulation of matrix metalloproteinase-2 (MMP-2) and −9 (MMP-9) expression in newly formed bone tissue at the interface between implants derived from castor oil (Ricinus communis) polymer and the tibia medullary canal.
Results showed that the castor based polymers induces bone formation by the expression of MMPs. The MMPs play an important role in tissue remodeling associated with various physiological and pathological processes such as morphogenesis, angiogenesis, tissue repair, cirrhosis, arthritis, and metastasis.
Forty-four rabbits were assigned to either Group 1 (n = 12; control) or Group 2 (n = 30), which had the tibial medullary canals reamed bilaterally and filled with polymer. CT scans showed no space between the material surface and the bone at the implant/bone marrow interface, and the density of the tissues at this interface was similar to the density measured of other regions of the bone. At 90 days post implantation, the interface with the polymer presented a thick layer of newly formed bone tissue rich in osteocytes. This tissue exhibited ongoing maturation at 120 and 150 days post implantation.
Overall, bone remodeling process was accompanied by positive modulation of MMP-2 and low MMP-9 expression. Differently, in control group, the internal surface close to the medullary canal was lined by osteoblasts, followed by a bone tissue zone with few lacunae filled with osteocytes. Maturation of the tissue of the medullary internal surface occurred in the inner region, with the bone being nonlamellar.