title: Differentiation of osteoprogenitor cells is affected by trauma-haemorrhage.
abstract: BACKGROUND
  In multiple trauma patients an increased incidence of delayed healing and non-union has been observed. The exact mechanisms underlying this delayed fracture healing are still not fully understood.
  
  
  METHODS
  40 male C57BL/6N-mice underwent standardized midline laparotomy and pressure-controlled haemorrhage (TH) or implantation of catheters without blood loss (sham procedure). Animals were sacrificed 24h or 72 h later. Osteoprogenitor cells derived from bone marrow were isolated and differentiated into osteoblasts for 20 days and osteoclasts for 7 days. Osteoblast mineralization and osteoclast numbers were determined, and gene expression of Alpl, Bglap, Opg, Rankl was measured in osteoblast cell culture, as well as gene expression of Rank, Ctsk and Nfatc1 was determined in osteoclast cell culture. Furthermore, plasma Opg, Rankl and TRAP were measured.
  
  
  RESULTS
  Mineralization capacity of osteoblasts was unchanged after TH, but Alpl gene expression after 23 days was significantly decreased compared to sham. Osteoclast number of group TH 8 days was significantly decreased compared to sham. Furthermore, gene expression of Ctsk and Nfatc1 were increased in group TH 10 days compared to group TH 8 days. Plasma Opg concentration was significantly elevated and Rankl concentrations were significantly declined in TH groups compared to sham groups after 24h and 72 h.
  
  
  CONCLUSIONS
  TH results in a diminished osteoclast number after 8 days, whereas differentiation of osteoblasts seems to be unaffected. The reduction of osteoclast number seems to be mediated through the Rankl-Opg-signalling pathway. However, further studies in models including a fractured extremity with a longer observation period are needed to identify the relevance of the Rankl-Opg- pathway in delayed fracture healing after TH and to focus on possible therapeutic interventions.
authors.affiliation: Trauma Department, Hannover Medical School, 30625 Hannover, Germany. Neunaber.Claudia@mh-hannover.de
authors.forename: Claudia
authors.initials: C
authors.lastname: Neunaber
authors.forename: Pinar
authors.initials: P
authors.lastname: Yesilkaya
authors.forename: Claudia
authors.initials: C
authors.lastname: Pütz
authors.forename: Christian
authors.initials: C
authors.lastname: Krettek
authors.forename: Frank
authors.initials: F
authors.lastname: Hildebrand
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D002454:Cell Differentiation / Q000502:physiology; D017102:Fracture Healing / Q000502:physiology*; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000235:genetics*; D006470:Hemorrhage; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000378:metabolism*; D010010:Osteoclasts / Q000378:metabolism*; D053244:Osteoprotegerin / Q000032:analysis / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D053245:RANK Ligand / Q000032:analysis / Q000097:blood / Q000235:genetics / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D006023:Glycoproteins; D053244:Osteoprotegerin; D053245:RANK Ligand; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse
keywords: Opg; Osteoblast; Osteoclast; Rankl; Trauma-haemorrhage