The evaluation of mineralized collagen as a carrier for the osteoinductive material COLLOSS(®)E, in vivo

In this study, the suitability of mineralized collagen, as a carrier for the native bone morphogenetic protein containing product COLLOSS(®)E, was evaluated in a rat subcutaneous implantation model. Tubular-shaped scaffolds were made from mineralized collagen and were left empty (controls), filled with 40 mg COLLOSS(®)E, or filled with a mixture of COLLOSS(®)E and osteoconductive β-tricalcium phosphate (β-TCP) granules. Six of all the samples were implanted in 18 animals. During the implantation period, macroscopic examination suggested inflammatory reaction. Histological evaluation after 12 weeks confirmed the presence of inflammatory cells. Although the mineralized scaffold and β-TCP granules could be clearly seen, no new bone formation was found. This is in contrast to previous reports in a similar set-up wherein a titanium mesh was used as scaffold material in combination with COLLOSS(®)E. It is concluded, therefore, that the osteoinductive capacity of bone morphogenetic proteins or, more specifically, COLLOSS(®)E is inhibited when the carrier gives rise to a significant inflammatory reaction. Additional studies are necessary to assess the effect of combining COLLOSS(®)E with a dimensionally stable and osteoconductive material like β-TCP.