MECHANICAL AND HISTOLOGICAL EVALUATION OF A TISSUE ENGINEERED BIOACTIVE SCAFFOLD IN VIVO

In this study the incorporation of resorbable, porous surface modified bioactive ceramics (pSMC) was investigated in a long bone defect. In order to promote osteogenic activity, two tissue engineered constructs were examined: 1) rat bone marrow stromal cells were seeded on pSMC two hours prior to implantation (primary) or 2) cells were expanded on pSMC for 2 weeks to synthesize bone prior to implantation (hybrid). A unicortical window defect was created bilaterally in the femoral diaphysis of 96 adult, male Fisher rats (350-400g). Defects were treated randomly with pSMC, primary, hybrid, or left untreated (sham) to compare healing rates at 2,4, and 12 weeks. Femora were tested in torsion and examined by histomorphometry.

At 2 weeks, long bones treated with the hybrid and primary constructs had 40% higher % bone in the defect than pSMC and the hybrid had the highest stiffness, which was comparable to intact bone. Primary and hybrid had comparable stiffness and strength to intact bone by 4 weeks. At 12 weeks, there was 40% bony ingrowth and 40% reduction in % scaffold for all treatment groups. PSMC achieved similar mechanical properties of intact bone by 12 weeks. Both tissue engineered constructs achieved early and similar rates of repair.