The angiogenic peptide pleiotrophin (PTN/HB-GAM) is expressed in fracture healing: an immunohistochemical study in rats.
BACKGROUND
Formation of new blood vessels is essential for the process of fracture healing.


METHODS
We investigated the expression of the angiogenic factor pleiotrophin/HB-GAM in a closed fracture model in rats by immunohistochemical methods.


RESULTS
Histologically, 5 days after fracture the callus was predominantly composed of fibrous tissue. On day 10 a prominent chondral callus connected both ends of the fractured tibia. There was a continuous transition from the chondral callus to the newly formed bone adjacent to the corticalis of the tibia. On day 15 the amount of woven bone had increased, and in 3 of 5 animals the proximal and distal tibiae were connected by a bridge of woven bone. Pleiotrophin could be immunostained in fibroblasts and endothelial cells of the fibrous tissue between the fractured tibia ends. The chondral callus remained largely pleiotrophin-negative. Only single chondrocytes adjacent to the newly formed bone were pleiotrophin-positive. On days 10 and 15 strong immunoreactivity for pleiotrophin in the well vascularized, newly formed, woven bone was detectable. Osteoblasts, endothelial cells and fibroblasts were strongly pleiotrophin-positive.


CONCLUSIONS
These results show the presence of the angiogenic peptide pleiotrophin during fracture healing.
Petersen
Wolf
W
Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Germany. wolfpetersen@hotmail.com
Wildemann
Britt
B
Pufe
Thomas
T
Raschke
Michael
M
Schmidmaier
Gerhard
G
D043925:Angiogenesis Inducing Agents / Q000378:metabolism*; D000818:Animals; D002146:Bony Callus / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D017102:Fracture Healing / Q000502:physiology*; D006133:Growth Substances / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D051381:Rats; D017207:Rats, Sprague-Dawley
D043925:Angiogenesis Inducing Agents; D002352:Carrier Proteins; D016207:Cytokines; D006133:Growth Substances; C066845:pleiotrophin