gms | German Medical Science

German Congress of Orthopaedics and Traumatology (DKOU 2016)

25.10. - 28.10.2016, Berlin

G-CSF Induced Mobilization of CD34+ Progenitor Cells Promotes Healing of Critical Size Bone Defects

Meeting Abstract

  • presenting/speaker Marietta Herrmann - AO Research Institute Davos, Davos Platz, Switzerland
  • Vincent Stadelmann - AO Research Institute Davos, Davos Platz, Switzerland
  • Stephan Zeiter - AO Research Institute Davos, Davos Platz, Switzerland
  • Ursula Eberli - AO Research Institute Davos, Davos Platz, Switzerland
  • Maria Hildebrand - AO Research Institute Davos, Davos Platz, Switzerland
  • Ursula Menzel - AO Research Institute Davos, Davos Platz, Switzerland
  • Mauro Alini - AO Research Institute Davos, Davos Platz, Switzerland
  • Sophie Verrier - AO Research Institute Davos, Davos Platz, Switzerland

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2016). Berlin, 25.-28.10.2016. Düsseldorf: German Medical Science GMS Publishing House; 2016. DocGR14-512

doi: 10.3205/16dkou424, urn:nbn:de:0183-16dkou4249

Published: October 10, 2016

© 2016 Herrmann et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at



Objectives: Stem- and progenitor cell mobilization is a critical event in bone regeneration. This includes mesenchymal stem cells (MSCs) as well as endothelial progenitor cells (EPCs). Transplantation of CD34+ EPCs has been variously applied to promote neovascularization of bone defects. These therapies include extensive ex vivo manipulation of cells. Granulocyte colony-stimulating factor (G-CSF) mediated mobilization of CD34+ progenitor cells (including EPCs) into the circulation is widely applied for peripheral stem cell donations and a positive effect of G-CSF administration on bone healing has been suggested. The aim of this study was to characterize the different cell populations mobilized by G-CSF and investigate the influence of cell mobilization before and after surgery on the healing of a critical size femoral defect in rats.

Methods: In a pilot experiment cell mobilization after subcutaneous injections of G-CSF for 5 consecutive days was investigated at day 1, day 5 and day 11 after the last injection and compared to untreated Fisher rats. Measurements included the total leukocyte count and flow cytometry analysis of different cell populations. In the main study, bone healing was compared in a saline-treated control group, a group receiving G-CSF injections at 5 consecutive days before surgery and a group receiving G-CSF injections after surgery. A 4.5 mm critically-sized femoral defect was created in female adult Fisher rats and fixed internally. Bone healing was monitored by in vivo micro CT and histology. One-way ANOVA was applied to test for significant differences between experimental groups.

Results and Conclusion: Our data revealed that leukocyte counts show a peak increase at the first day after the last G-CSF injection with 7340±598 leukocytes/ul blood which was significantly higher compared to the values of untreated animals (4437±374 leukocytes/ul blood, p<0.001). Analysis of different cell populations by flow cytometry revealed a cell-specific mobilization kinetic. We found that CD34+ progenitor cells were significantly enriched at day 1 (p<0.05), and further increased at day 5 (p<0.001) and day 11 (p<0.001). Upregulation of monocytes, granulocytes and macrophages peaked at day 1. In the main study, we found that both G-CSF treatment protocols increased the bone volume in the fracture gap, which was also confirmed by histology. Although continuous bone formation was observed, none of the fracture gaps reached bridging until the end of the experiment.

Our data shows that different cell populations are upregulated by G-CSF treatment in a cell specific pattern. Although in this study no bridging of the critically-sized defect was reached, an improved healing was clearly shown. These results identify cell mobilization by G-CSF as a potential treatment option to facilitate the healing of large bone defects in combination with other treatment methods such as bone grafts.