Morphological effects of mesenchymal stem cells and pulsed ultrasound on condylar growth in rats: a pilot study

The aim of this study was to assess and describe the morphological effects of an intra-articular iniection of Mesenchymal Stem Cells (MSCs) and/or Low Intensity Pulsed Ultrasound (LIPUS) stimulation on the mandibular condyles of growing rats, using cone beam computed tomography (CBCT) and histology.

Twenty-six young (23-day-old) rats were divided into 5 groups identified as LIPUS-stimulated (20 minutes daily using 50 mW/cm2, 1MHz, 0.2 millisecond pulses), MSCs injected (1 x 10(5) cells/kg), LIPUS + MSCs, medium inlected, and untreated controls. All treatments were performed in the left temporomandibular joint of each rat (TMJs). At day 21, CBCTs were obtained for cephalometric analysis and 3D reconstructions. After animal sacrifice, left and right TMJ sections were histologically prepared and examined. The Wilcoxon sign rank test and the Kruskal-Wallis 2 test were applied for statistical comparison.

Imaging results showed that left condyles were wider in all LIPUS-treated groups (p < 0.05), while the LIPUS-only group had a greater left sagittal condylar length. LIPUS-treated groups displayed a lower midline shift to the right (p < 0.02). No significant differences were observed in the MSC group. Bone marrow morphology and vascularity differed between the groups as LIPUS-treated groups exhibited increased vascularity in the erosive cartilage zone.

It was established that LIPUS and MSC application to the TMJ region of growing rats favoured transverse condylar growth, while LIPUS application alone may enhance sagittal condylar development.The MSC injection model had little effect on sagittal condylar growth.