title: Stimulation with bone morphogenetic protein-2 (BMP-2) enhances bone-tendon integration in vitro.
abstract: OBJECTIVE
  Preclinical studies have reported that bone morphogenetic protein (BMP)-2 promotes bone-tendon healing following anterior cruciate ligament reconstruction. We examined the region-specific effects of BMP-2 on osteoblast and fibroblast differentiation in a highly standardized murine in vitro co-culture model of bone-tendon integration.
  
  
  METHODS
  We used quantitative PCR to measure the dose- and time-dependent influence of BMP-2 on the expression of alkaline phosphatase, osteocalcin, collagen type 1 (alpha 1 chain), runt-related transcription factor 2, osteopontin, collagen type 1 (alpha 2 chain), collagen type 5 (alpha 1 chain), decorin, fibromodulin, mohawk homeobox, bone morphogenetic protein receptor, type 1A, bone morphogenetic protein receptor, type 2, and Noggin in the osteoblast, interface, and fibroblast regions of a co-culture model of the murine preosteoblast cell line MC3T3-E1 and the fibroblast cell line 3T6.
  
  
  RESULTS
  Stimulation with BMP-2 resulted in a significant upregulation of alkaline phosphatase (p < 0.001), osteocalcin (p < 0.001), collagens (p < 0.001), runt-related transcription factor 2 (p < 0.05), and osteopontin (p < 0.001) expression in the osteoblast region. In the interface region, BMP-2 exposure led to dose- and time-dependent upregulation of alkaline phosphatase (p < 0.001), osteocalcin (p < 0.001), osteopontin (p < 0.001), runt-related transcription factor 2 (p < 0.001), and markers of extracellular matrix production (p < 0.001). Both BMP receptors showed a significant BMP-2-dependent upregulation at the interface region, and Noggin was downregulated at the osteoblast and interface region following BMP-2 exposure.
  
  
  CONCLUSIONS
  Exposure to BMP-2 upregulated the expression of genes associated with bone-tendon integration in vitro, suggesting the stimulation of transdifferentiation processes at the interface and fibroblast regions as well as the induction of positive feedback mechanisms. Further studies will be needed to establish BMP-2 dose and treatment algorithms following tendon reinsertion and reconstruction.
authors.affiliation: a Center for Orthopaedics and Trauma Surgery , University of Giessen and Marburg , Marburg , Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Schwarting
authors.affiliation: a Center for Orthopaedics and Trauma Surgery , University of Giessen and Marburg , Marburg , Germany.
authors.forename: Dano
authors.initials: D
authors.lastname: Schenk
authors.affiliation: a Center for Orthopaedics and Trauma Surgery , University of Giessen and Marburg , Marburg , Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Frink
authors.affiliation: a Center for Orthopaedics and Trauma Surgery , University of Giessen and Marburg , Marburg , Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Benölken
authors.affiliation: a Center for Orthopaedics and Trauma Surgery , University of Giessen and Marburg , Marburg , Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Steindor
authors.affiliation: a Center for Orthopaedics and Trauma Surgery , University of Giessen and Marburg , Marburg , Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Oswald
authors.affiliation: a Center for Orthopaedics and Trauma Surgery , University of Giessen and Marburg , Marburg , Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Ruchholtz
authors.affiliation: a Center for Orthopaedics and Trauma Surgery , University of Giessen and Marburg , Marburg , Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Lechler
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology*; D001842:Bone and Bones / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D018920:Coculture Techniques; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D025461:Feedback, Physiological / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D051379:Mice; D016348:Osseointegration / Q000187:drug effects*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects; D013710:Tendons / Q000187:drug effects / Q000502:physiology*; D014945:Wound Healing / Q000187:drug effects
chemical_list: D055396:Bone Morphogenetic Protein 2
keywords: ACL (anterior cruciate ligament) reconstruction; BMP signaling; BMP-2; bone–tendon integration; ligament injury; transdifferentiation