title: A preliminary investigation of the effect of relaxin on bone remodelling in suture expansion.
abstract: Relaxin (RLN) is an insulin-like hormone associated with extracellular matrix degradation, osteoclastogenesis, and osteoblast differentiation. This study aimed to assess the effect of RLN during and after lateral expansion of murine calvarial sagittal sutures.
  
  
  
  RLN was injected topically using a nano-sized liposome carrier into the sagittal sutures of 8- to 10-week-old wild type mice just before lateral expansion. Suture morphology, bone mineral density (BMD), and bone volume were analysed by micro-computed tomography. Collagen deposition and osteoclast differentiation were observed by Verhoeff-Van Gieson (VVG) and tartrate-resistant acid phosphatase (TRAP) staining, respectively.
  
  
  
  Less collagen staining and higher tissue-specific relaxin/insulin-like family peptide receptor (Rxfp)-1 and -2 expression were observed in the RLN-treated samples after 48 hours. Increased BMD and volume, and thick well-organised osteoid tissue, with multinucleated TRAP-positive cells, were observed in RLN-treated samples after 1 week. Increased Rxfp-1 expression was observed in the sagittal sutures in the mid-suture fibrous tissue following RLN treatment. Rxfp-2 was only expressed in the calvarial bone under tensile stimulation and RLN treatment further increased its expression.
  
  
  
  RLN-liposomes were not detected at any instance under the current experimental conditions. This is a preliminary study and the sample number limits the power of its results. VVG staining cannot quantify collagen contents but can provide preliminary information on the presence of collagen fibres.
  
  
  
  RLN treatment may modify bone remodelling and collagen metabolism during and after suture expansion.
authors.affiliation: Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Carolina
authors.initials: C
authors.lastname: Duarte
authors.affiliation: Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Yukiho
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.|Division of Orofacial Functions and Orthodontics, Department of Health Promotion, Faculty of Dentistry, Kyushu Dental University, 2-6-1, Manazuru, Kokura-kita, Kitakyushu, Fukuoka 803-8580, Japan.
authors.forename: Jumpei
authors.initials: J
authors.lastname: Morita
authors.affiliation: Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.|Division of Orofacial Functions and Orthodontics, Department of Health Promotion, Faculty of Dentistry, Kyushu Dental University, 2-6-1, Manazuru, Kokura-kita, Kitakyushu, Fukuoka 803-8580, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Kawamoto
authors.affiliation: Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Moriyama
mesh_terms: D000818:Animals; D015519:Bone Density / Q000187:drug effects; D016723:Bone Remodeling / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D003094:Collagen / Q000378:metabolism; D003393:Cranial Sutures / Q000187:drug effects* / Q000378:metabolism / Q000601:surgery; D004353:Drug Evaluation, Preclinical / Q000379:methods; D008081:Liposomes; D008297:Male; D008810:Mice, Inbred C57BL; D010012:Osteogenesis / Q000187:drug effects; D010155:Palatal Expansion Technique; D012065:Relaxin / Q000008:administration & dosage / Q000494:pharmacology*; D055114:X-Ray Microtomography
chemical_list: D008081:Liposomes; C095067:RLN1 protein, human; D012065:Relaxin; D003094:Collagen