title: A Combination of rhBMP-2 (Recombinant Human Bone Morphogenetic Protein-2) and MEK (MAP Kinase/ERK Kinase) Inhibitor PD0325901 Increases Bone Formation in a Murine Model of Neurofibromatosis Type I Pseudarthrosis.
abstract: BACKGROUND
  Congenital tibial dysplasia is a severe pediatric condition that classically results in a persistent pseudarthrosis. A majority of these cases are associated with neurofibromatosis type I (NF1), a genetic disorder in which inactivation of the NF1 gene leads to overactivity of the Ras-MEK-MAPK (mitogen-activated protein kinase) signaling pathway. We therefore hypothesized that pharmaceutical inhibition of MEK-MAPK may be a beneficial therapeutic strategy.
  
  
  METHODS
  In vitro methods were used to demonstrate a role for the MEK inhibitor PD0325901 in promoting osteogenic differentiation in Nf1-/-calvarial osteoblasts. Local applications of rhBMP-2 and/or PD0325901 were then tested in a mouse model of NF1 tibial pseudarthrosis featuring localized double inactivation of the Nf1 gene in a fracture. Mice received no treatment, PD0325901 (10 mg/kg/day from two days before fracture to ten days after fracture), rhBMP-2 (10 μg), or a combination of rhBMP-2 and PD0325901.
  
  
  RESULTS
  Animals treated with the delivery vehicle alone, PD0325901, rhBMP-2, or the PD0325901 + rhBMP-2 combination showed union rates of 0%, 8%, 69% (p < 0.01), or 80% (p < 0.01), respectively, at twenty-one days after fracture. Mice treated with the rhBMP-2 + PD0325901 combination displayed a callus volume sixfold greater than the vehicle controls and twofold greater than the group receiving rhBMP-2 alone. Although MEK inhibition combined with rhBMP-2 led to increases in bone formation and union, the proportion of fibrous tissue in the callus was not significantly reduced.
  
  
  CONCLUSIONS
  The data suggest that MEK inhibition can promote bone formation in combination with rhBMP-2 in the context of an NF1 pseudarthrosis. However, PD0325901 did not promote substantive bone anabolism in the absence of an exogenous anabolic stimulus and did not suppress fibrosis.
  
  
  CONCLUSIONS
  This study examines a signaling pathway-based approach to treating poor bone healing in a model of NF1 pseudarthrosis.
authors.affiliation: Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia. E-mail address for J. El-Hoss: jel-hoss@ccia.unsw.edu.au. E-mail address for T. Cheng: tegan.cheng@sydney.edu.au. E-mail address for E.C. Carpenter: carpie@doctors.org.uk. E-mail address for K. Sullivan: kates3@live.com. E-mail address for N. Deo: nikita.deo@sydney.edu.au. E-mail address for K. Mikulec: kathy.mikulec@health.nsw.gov.au. E-mail address for D.G. Little: david.little@health.nsw.gov.au. E-mail address for A. Schindeler: aaron.schindeler@sydney.edu.au.
authors.forename: J
authors.initials: J
authors.lastname: El-Hoss
authors.affiliation: Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia. E-mail address for J. El-Hoss: jel-hoss@ccia.unsw.edu.au. E-mail address for T. Cheng: tegan.cheng@sydney.edu.au. E-mail address for E.C. Carpenter: carpie@doctors.org.uk. E-mail address for K. Sullivan: kates3@live.com. E-mail address for N. Deo: nikita.deo@sydney.edu.au. E-mail address for K. Mikulec: kathy.mikulec@health.nsw.gov.au. E-mail address for D.G. Little: david.little@health.nsw.gov.au. E-mail address for A. Schindeler: aaron.schindeler@sydney.edu.au.
authors.forename: T
authors.initials: T
authors.lastname: Cheng
authors.affiliation: Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia. E-mail address for J. El-Hoss: jel-hoss@ccia.unsw.edu.au. E-mail address for T. Cheng: tegan.cheng@sydney.edu.au. E-mail address for E.C. Carpenter: carpie@doctors.org.uk. E-mail address for K. Sullivan: kates3@live.com. E-mail address for N. Deo: nikita.deo@sydney.edu.au. E-mail address for K. Mikulec: kathy.mikulec@health.nsw.gov.au. E-mail address for D.G. Little: david.little@health.nsw.gov.au. E-mail address for A. Schindeler: aaron.schindeler@sydney.edu.au.
authors.forename: E C
authors.initials: EC
authors.lastname: Carpenter
authors.affiliation: Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia. E-mail address for J. El-Hoss: jel-hoss@ccia.unsw.edu.au. E-mail address for T. Cheng: tegan.cheng@sydney.edu.au. E-mail address for E.C. Carpenter: carpie@doctors.org.uk. E-mail address for K. Sullivan: kates3@live.com. E-mail address for N. Deo: nikita.deo@sydney.edu.au. E-mail address for K. Mikulec: kathy.mikulec@health.nsw.gov.au. E-mail address for D.G. Little: david.little@health.nsw.gov.au. E-mail address for A. Schindeler: aaron.schindeler@sydney.edu.au.
authors.forename: K
authors.initials: K
authors.lastname: Sullivan
authors.affiliation: Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia. E-mail address for J. El-Hoss: jel-hoss@ccia.unsw.edu.au. E-mail address for T. Cheng: tegan.cheng@sydney.edu.au. E-mail address for E.C. Carpenter: carpie@doctors.org.uk. E-mail address for K. Sullivan: kates3@live.com. E-mail address for N. Deo: nikita.deo@sydney.edu.au. E-mail address for K. Mikulec: kathy.mikulec@health.nsw.gov.au. E-mail address for D.G. Little: david.little@health.nsw.gov.au. E-mail address for A. Schindeler: aaron.schindeler@sydney.edu.au.
authors.forename: N
authors.initials: N
authors.lastname: Deo
authors.affiliation: Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia. E-mail address for J. El-Hoss: jel-hoss@ccia.unsw.edu.au. E-mail address for T. Cheng: tegan.cheng@sydney.edu.au. E-mail address for E.C. Carpenter: carpie@doctors.org.uk. E-mail address for K. Sullivan: kates3@live.com. E-mail address for N. Deo: nikita.deo@sydney.edu.au. E-mail address for K. Mikulec: kathy.mikulec@health.nsw.gov.au. E-mail address for D.G. Little: david.little@health.nsw.gov.au. E-mail address for A. Schindeler: aaron.schindeler@sydney.edu.au.
authors.forename: K
authors.initials: K
authors.lastname: Mikulec
authors.affiliation: Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia. E-mail address for J. El-Hoss: jel-hoss@ccia.unsw.edu.au. E-mail address for T. Cheng: tegan.cheng@sydney.edu.au. E-mail address for E.C. Carpenter: carpie@doctors.org.uk. E-mail address for K. Sullivan: kates3@live.com. E-mail address for N. Deo: nikita.deo@sydney.edu.au. E-mail address for K. Mikulec: kathy.mikulec@health.nsw.gov.au. E-mail address for D.G. Little: david.little@health.nsw.gov.au. E-mail address for A. Schindeler: aaron.schindeler@sydney.edu.au.
authors.forename: D G
authors.initials: DG
authors.lastname: Little
authors.affiliation: Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia. E-mail address for J. El-Hoss: jel-hoss@ccia.unsw.edu.au. E-mail address for T. Cheng: tegan.cheng@sydney.edu.au. E-mail address for E.C. Carpenter: carpie@doctors.org.uk. E-mail address for K. Sullivan: kates3@live.com. E-mail address for N. Deo: nikita.deo@sydney.edu.au. E-mail address for K. Mikulec: kathy.mikulec@health.nsw.gov.au. E-mail address for D.G. Little: david.little@health.nsw.gov.au. E-mail address for A. Schindeler: aaron.schindeler@sydney.edu.au.
authors.forename: A
authors.initials: A
authors.lastname: Schindeler
mesh_terms: D000818:Animals; D001549:Benzamides / Q000008:administration & dosage* / Q000494:pharmacology; D055396:Bone Morphogenetic Protein 2 / Q000008:administration & dosage* / Q000494:pharmacology; D004159:Diphenylamine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination; D005260:Female; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors*; D009456:Neurofibromatosis 1 / Q000150:complications*; D010012:Osteogenesis / Q000187:drug effects*; D011542:Pseudarthrosis / Q000188:drug therapy* / Q000209:etiology*; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D001549:Benzamides; D055396:Bone Morphogenetic Protein 2; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; C506614:mirdametinib; D004159:Diphenylamine; D020929:Mitogen-Activated Protein Kinase Kinases