In vivo ultrasound-assisted tissue-engineered mandibular condyle: A pilot study in rabbits

Context: Tissue engineering of mandibular articular condyles encounters many challenges, especially restoring adequate mechanical strength that is correlated to matrix production by the tissue-engineered mandibular condyles (TEMCs). Low-intensity pulsed ultrasound (LIPUS) has been shown to enhance cell expansion, differentiation, and matrix production by different cells. Objective: This study evaluated effect of daily LIPUS treatment (in vitro and in a pilot in vivo study) for 4 weeks on matrix production and functional integration of the TEMCs in rabbits. Methods: Bone marrow stromal cells were isolated from the femoral bones of skeletally mature New Zealand rabbits, expanded, and differentiated into chondrogenic and osteogenic lineages. Animals employed in the in vivo study were divided into four groups: (1) TEMCs and LIPUS treatment; (2) TEMCs without LIPUS treatment; (3) empty scaffold and LIPUS treatment, and (4) empty scaffolds without LIPUS treatment. Results: In vitro results showed that LIPUS enhanced chondrogenic and osteogenic differentiation of bone marrow stromal cells. The in vivo study showed that LIPUS led to better structural formation (namely, new osteogenic and chondrogenic tissue formation) and integration of the newly formed tissues and original condylar bone than those without LIPUS treatment. LIPUS resulted in a small amount of tissue regeneration in the empty scaffolds, whereas empty scaffolds without LIPUS treatment showed no signs of repair. Conclusions: The preliminary results of this pilot study suggest that LIPUS can enhance TEMCs both in vitro and in vivo.