title: Nell-1 enhances bone regeneration in a rat critical-sized femoral segmental defect model.
abstract: BACKGROUND
  Effective regeneration of bone is critical for fracture repair and incorporation and healing of bone grafts used during orthopedic, dental, and craniofacial reconstructions. Nel-like molecule-1 (Nell-1) is a secreted protein identified from prematurely fused cranial sutures of craniosynostosis patients that has been found to specifically stimulate osteogenic cell differentiation and bone formation. To test the in vivo osteoinductive capacity of Nell-1, a critical-sized femoral segmental defect model in athymic rats was used.
  
  
  METHODS
  A 6-mm defect, which predictably leads to nonunion if left untreated, was created in the left femur of each rat. Three treatment groups (n = 8 each) were created consisting of rats treated with (1) 1.5 mg/ml Nell-1, (2) 0.6 mg/ml Nell-1, and (3) phosphate-buffered saline only as a Nell-free control. Phosphate-buffered saline or Nell-1 was mixed with demineralized bone matrix as a carrier before implantation. All animals were euthanized 12 weeks after surgery, and bone regeneration was evaluated using radiographic, three-dimensional micro-computed tomographic, and histologic analysis.
  
  
  RESULTS
  Both Nell-1-treated groups had significantly greater bone formation compared with the Nell-free group, with bone volume increasing with increasing Nell-1 concentration.
  
  
  CONCLUSIONS
  Nell-1 in a demineralized bone matrix carrier can significantly improve bone regeneration in a critical-sized femoral segmental defect in a dose-dependent manner. The results of this study demonstrate that Nell-1 is a potent osteospecific growth factor that warrants further investigation. Results also support the potential application of Nell-1 as a bone graft substitute in multiple clinical scenarios involving repair of critical bone loss when autograft bone is limited or unavailable.
authors.affiliation: Los Angeles, Calif.; Harbin, China; and Edison, N.J. From the Dental and Craniofacial Research Institute, the Department of Bioengineering, the Division of Advanced Prosthodontics, Biomaterials, and Hospital Dentistry, and the Department of Orthopedic Surgery, University of California, Los Angeles; the Department of Orthopedics, First Clinical Hospital, Harbin Medical University; and the Musculoskeletal Transplant Foundation.
authors.forename: Weiming
authors.initials: W
authors.lastname: Li
authors.forename: Janette N
authors.initials: JN
authors.lastname: Zara
authors.forename: Ronald K
authors.initials: RK
authors.lastname: Siu
authors.forename: Min
authors.initials: M
authors.lastname: Lee
authors.forename: Tara
authors.initials: T
authors.lastname: Aghaloo
authors.forename: Xinli
authors.initials: X
authors.lastname: Zhang
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Wu
authors.forename: Arthur A
authors.initials: AA
authors.lastname: Gertzman
authors.forename: Kang
authors.initials: K
authors.lastname: Ting
authors.forename: Chia
authors.initials: C
authors.lastname: Soo
mesh_terms: D000818:Animals; D016723:Bone Remodeling / Q000187:drug effects / Q000502:physiology*; D005264:Femoral Fractures / Q000503:physiopathology; D005269:Femur / Q000293:injuries*; D017102:Fracture Healing / Q000187:drug effects / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000494:pharmacology / Q000502:physiology*; D016348:Osseointegration / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011923:Rats, Nude; D014057:Tomography, X-Ray Computed
chemical_list: C484480:Nell1 protein, rat; D009419:Nerve Tissue Proteins