title: Cellular and Matrix Response of the Mandibular Condylar Cartilage to Botulinum Toxin.
abstract: OBJECTIVE
  To evaluate the cellular and matrix effects of botulinum toxin type A (Botox) on mandibular condylar cartilage (MCC) and subchondral bone.
  
  
  METHODS
  Botox (0.3 unit) was injected into the right masseter of 5-week-old transgenic mice (Col10a1-RFPcherry) at day 1. Left side masseter was used as intra-animal control. The following bone labels were intraperitoneally injected: calcein at day 7, alizarin red at day 14 and calcein at day 21. In addition, EdU was injected 48 and 24 hours before sacrifice. Mice were sacrificed 30 days after Botox injection. Experimental and control side mandibles were dissected and examined by x-ray imaging and micro-CT. Subsequently, MCC along with the subchondral bone was sectioned and stained with tartrate resistant acid phosphatase (TRAP), EdU, TUNEL, alkaline phosphatase, toluidine blue and safranin O. In addition, we performed immunohistochemistry for pSMAD and VEGF.
  
  
  RESULTS
  Bone volume fraction, tissue density and trabecular thickness were significantly decreased on the right side of the subchondral bone and mineralized cartilage (Botox was injected) when compared to the left side. There was no significant difference in the mandibular length and condylar head length; however, the condylar width was significantly decreased after Botox injection. Our histology showed decreased numbers of Col10a1 expressing cells, decreased cell proliferation and increased cell apoptosis in the subchondral bone and mandibular condylar cartilage, decreased TRAP activity and mineralization of Botox injected side cartilage and subchondral bone. Furthermore, we observed reduced proteoglycan and glycosaminoglycan distribution and decreased expression of pSMAD 1/5/8 and VEGF in the MCC of the Botox injected side in comparison to control side.
  
  
  CONCLUSIONS
  Injection of Botox in masseter muscle leads to decreased mineralization and matrix deposition, reduced chondrocyte proliferation and differentiation and increased cell apoptosis in the MCC and subchondral bone.
authors.affiliation: Department of Orthodontics, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Eliane H
authors.initials: EH
authors.lastname: Dutra
authors.affiliation: Department of Orthodontics, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Mara H
authors.initials: MH
authors.lastname: O' Brien
authors.affiliation: Department of Orthodontics, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Alexandro
authors.initials: A
authors.lastname: Lima
authors.affiliation: Department of Oral and Maxillofacial Diagnostic Sciences, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Zana
authors.initials: Z
authors.lastname: Kalajzic
authors.affiliation: Department of Oral and Maxillofacial Radiology, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Aditya
authors.initials: A
authors.lastname: Tadinada
authors.affiliation: Department of Orthodontics, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Ravindra
authors.initials: R
authors.lastname: Nanda
authors.affiliation: Department of Orthodontics, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Sumit
authors.initials: S
authors.lastname: Yadav
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D019274:Botulinum Toxins, Type A / Q000009:adverse effects* / Q000494:pharmacology; D002113:Calcification, Physiologic / Q000187:drug effects; D002356:Cartilage / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects*; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology; D024121:Collagen Type X / Q000096:biosynthesis / Q000235:genetics; D005109:Extracellular Matrix / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D008335:Mandibular Condyle / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D008406:Masseter Muscle / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics; D055114:X-Ray Microtomography
chemical_list: C570620:Col10a1 protein, mouse; D024121:Collagen Type X; D051785:Smad Proteins; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D019274:Botulinum Toxins, Type A