title: Polyethylene particle-induced bone resorption in alpha-calcitonin gene-related peptide-deficient mice.
abstract: This study investigates the impact of alpha-CGRP on bone metabolism after implantation of polyethylene particles. alpha-CGRP knockout mice showed less osteolysis compared with wildtype mice. The local neurogenic microenvironment might be a crucial factor in particle-induced osteolysis.
  
  
  BACKGROUND
  Periprosthetic osteolysis is the major reason for aseptic loosening in joint arthroplasty. This study aimed to investigate the potential impact of alpha-calcitonin gene-related peptide (alpha-CGRP) deficiency on bone metabolism under conditions of polyethylene particle-induced osteolysis.
  
  
  METHODS
  We used the murine calvarial osteolysis model based on polyethylene particles in 14 C57BL 6 mice and 14 alpha-CGRP-deficient mice divided into four groups of 7 mice each. Groups 1 (C57BL/J 6) and 3 (alpha-CGRP knockout) received sham surgery, and groups 2 (C57BL/J 6) and 4 (alpha-CGRP knockout) were treated with polyethylene particles. Qualitative and quantitative 3D analyses were performed using microCT. In addition, bone resorption was measured within the midline suture by histological examination. The number of osteoclasts was determined by counting the TRACP(+) cells. Calvarial bone was tested for RANKL expression by RT-PCR and immunocytochemistry.
  
  
  RESULTS
  Bone resorption was significantly reduced in alpha-CGRP-deficient mice compared with their corresponding wildtype C57BL 6 mice as confirmed by histomorphometric data (p < 0.001) and microCT (p < 0.01). Osteoclast numbers were significantly reduced in group 3 and the particle subgroup compared with group 1 (p < 0.001). We observed a >3-fold increase of basal RANKL mRNA levels within group 1 compared with group 3. Additional low RANKL immunochemistry staining was noted in groups 3 and 4.
  
  
  CONCLUSIONS
  In conclusion, alpha-CGRP knockout mice did not show the expected extended osteolysis compared with wildtype mice expressing alpha-CGRP. One of the most reasonable explanations for the observed decrease in osteolysis could be linked to the osteoprotegerin (OPG)/RANK/RANKL system in alpha-CGRP-deficient animals. As a consequence, the fine tuning of osteoclasts mediating resorption in alpha-CGRP-null mice may be deregulated.
authors.affiliation: Department of Orthopaedics, University of Duisburg-Essen, Essen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wedemeyer
authors.forename: Carl
authors.initials: C
authors.lastname: Neuerburg
authors.forename: Anne
authors.initials: A
authors.lastname: Pfeiffer
authors.forename: Anja
authors.initials: A
authors.lastname: Heckelei
authors.forename: David
authors.initials: D
authors.lastname: Bylski
authors.forename: Fabian
authors.initials: F
authors.lastname: von Knoch
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schinke
authors.forename: Gero
authors.initials: G
authors.lastname: Hilken
authors.forename: Georg
authors.initials: G
authors.lastname: Gosheger
authors.forename: Marius
authors.initials: M
authors.lastname: von Knoch
authors.forename: Franz
authors.initials: F
authors.lastname: Löer
authors.forename: Guido
authors.initials: G
authors.lastname: Saxler
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D001862:Bone Resorption / Q000139:chemically induced / Q000473:pathology*; D015740:Calcitonin Gene-Related Peptide / Q000172:deficiency*; D002452:Cell Count; D007150:Immunohistochemistry; D020007:Implants, Experimental; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects; D020959:Polyethylene / Q000494:pharmacology*; D053245:RANK Ligand / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012886:Skull / Q000187:drug effects / Q000473:pathology; D000071681:Tartrate-Resistant Acid Phosphatase; D014057:Tomography, X-Ray Computed
chemical_list: D007527:Isoenzymes; D053245:RANK Ligand; D020959:Polyethylene; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D015740:Calcitonin Gene-Related Peptide