title: Transforming growth factor alpha controls the transition from hypertrophic cartilage to bone during endochondral bone growth.
abstract: We have recently identified transforming growth factor alpha (TGFα) as a novel growth factor involved in the joint disease osteoarthritis. The role of TGFα in normal cartilage and bone physiology however, has not been well defined.
  
  
  OBJECTIVE
  The objective of this study was to determine the role of TGFα in bone development through investigation of the Tgfa knockout mouse.
  
  
  METHODS
  The gross skeletons as well as the cartilage growth plates of Tgfa knockout mice and their control littermates were examined during several developmental stages ranging from newborn to ten weeks old.
  
  
  RESULTS
  Knockout mice experienced skeletal growth retardation and expansion of the hypertrophic zone of the growth plate. These phenotypes were transient and spontaneously resolved by ten weeks of age. Tgfa knockout growth plates also had fewer osteoclasts along the cartilage/bone interface. Furthermore, knockout mice expressed less RUNX2, RANKL, and MMP13 mRNA in their cartilage growth plates than controls did.
  
  
  CONCLUSIONS
  Tgfa knockout mice experience a delay in bone development, specifically the conversion of hypertrophic cartilage to true bone. The persistence of the hypertrophic zone of the growth plate appears to be mediated by a decrease in MMP13 and RANKL expression in hypertrophic chondrocytes and a resulting reduction in osteoclast recruitment. Overall, TGFα appears to be an important growth factor regulating the conversion of cartilage to bone during the process of endochondral ossification.
authors.affiliation: Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada. susmani@uwo.ca
authors.forename: Shirine E
authors.initials: SE
authors.lastname: Usmani
authors.forename: Michael A
authors.initials: MA
authors.lastname: Pest
authors.forename: Gunwoo
authors.initials: G
authors.lastname: Kim
authors.forename: Sara N
authors.initials: SN
authors.lastname: Ohora
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
authors.forename: Frank
authors.initials: F
authors.lastname: Beier
mesh_terms: D000818:Animals; D001846:Bone Development / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism*; D002356:Cartilage / Q000378:metabolism*; D019902:Chondrocytes / Q000378:metabolism; D005260:Female; D006984:Hypertrophy / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009924:Organ Culture Techniques; D013977:Tibia / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D016211:Transforming Growth Factor alpha / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D016211:Transforming Growth Factor alpha