Loading of the Condylar Cartilage Can Rescue the Effects of Botox on TMJ
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The purpose of this study is to evaluate whether the effects of botulinum neurotoxin (botox) injection into the masseter in the mandibular condylar cartilage (MCC) and subchondral bone could be rescued by compressive loading of the temporomandibular joint (TMJ). Twenty-four 6-week-old female mice (C57BL/6J) were used. Mice were divided in three groups: (1) Botox (n = 8); (2) Botox plus loading (n = 8); (3) Pure control (n = 8). Bone labels (3 and 1 day before sacrifice) and the proliferation marker EdU (2 and 1 day before sacrifice) were intraperitoneally injected into all groups of mice. Condyles were dissected and examined by micro-CT and histology. Sagittal sections of condyles were stained for TRAP, alkaline phosphatase, EdU, TUNEL, and toluidine blue. In addition, immunostaining for pSmad, VEGF, and Runx2 was performed. Bone volume fraction, tissue density, and trabecular thickness were significantly decreased on the subchondral bone of botox-injected side when compared to control side and control mice, 4 weeks after injection. Furthermore, histological analysis revealed decrease in mineralization, matrix deposition, TRAP activity, EdU, and TUNEL-positive cells in the MCC of the botox-injected side, 4 weeks after injection. However, compressive loading reversed the reduced bone volume and density and the cellular changes in the MCC caused by Botox injection. TMJ compressive loading rescues the negative effects of botox injection into the masseter in the MCC and subchondral bone.
KeywordsBotulinum toxin Extracellular matrix Cartilage Temporomandibular joint disorder
The authors have no affiliations with or involvement in any organization or entity with any financial interest in the subject matter or materials discussed in this manuscript. Research reported in this publication was supported by the National Institute of Dental and Craniofacial Research of the National Institute of Health under the Award Number KO8DE025914 and by the American Association of Orthodontic Foundation and startup funds provided to SY.
EHD—conceived and designed study, collected, assembled and interpreted data, drafted and approved article. MHO—conceived and designed study, collected, assembled and interpreted data, drafted and approved article. CL—assisted in processing and interpreting the histological images. AT—collected, assembled and interpreted data, revised and approved article. RN—collected, assembled and interpreted data, revised and approved article. SY—obtained funding, conceived and designed study, collected, assembled and interpreted data, drafted and approved article.
Compliance with Ethical Standards
Conflict of interest
Eliane H. Dutra, Mara H. O’Brien, Candice Logan, Aditya Tadinada, Ravindra Nanda, Sumit Yadav declare that they have no conflict of interest.
Human and Animal Rights and Informed Consent
All institutional and national guidelines for the care and use of laboratory animals were followed.
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