The angiogenic peptide vascular endothelial growth factor (VEGF) is expressed during the remodeling of free tendon grafts in sheep.
BACKGROUND
Angiogenesis is important for the remodeling of autologous tendon grafts. A sheep model was used to examine the expression of the angiogenic peptide vascular endothelial growth factor (VEGF) in autologous tendon grafts after anterior cruciate ligament (ACL) reconstruction.


METHODS
Merino sheep underwent ACL reconstruction with an autologous Achilles tendon split graft. VEGF and its receptors, the Fms-like tyrosine kinase receptor (FLT-1, VEGFR-1) and the kinase insert domain-containing receptor KDR (VEGFR-2/FLK-1) were detected immunohistochemically. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect which of the different VEGF splice forms are expressed during ACL remodeling.


RESULTS
At 6 weeks, light microscopy showed zones with hypocellular necrotic graft tissue in the central part surrounded by hypercellular and hypervascularized reparative tissue invading the former graft tissue from the periphery. In contrast to the necrotic tissue, all cell types of the reparative tissue labeled strongly positive for VEGF. The VEGF receptors FLT-1 and KDR could be detected on endothelial cells of blood vessels. At 12 weeks, the complete graft diameter showed an increased vascular density (anti-factor VIII immunoreactivity), but zones of non-remodeled former graft tissue could not be found. Fusiform fibroblasts labeled strongly for VEGF. At 24 weeks, VEGF immunostaining decreased, and at 52 and 104 weeks, the grafts were largely VEGF-negative. RT-PCR supported the immunohistochemical results regarding VEGF expression and showed further that the splice variants VEGF(120 )and VEGF(164) are expressed during angiogenesis during the remodeling of tendons.


CONCLUSIONS
We conclude that the angiogenic peptide VEGF plays a role in tendon graft remodeling.
Department of Orthopaedic Surgery, Christian Albrechts University, Kiel, Germany. wolfpetersen@hotmail.com
Wolf
W
Petersen
Frank
F
Unterhauser
Thomas
T
Pufe
Thore
T
Zantop
Norbert P
NP
Südkamp
Andreas
A
Weiler
D000125:Achilles Tendon / Q000637:transplantation*; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001182:Arthroscopy / Q000379:methods; D001483:Base Sequence; D015415:Biomarkers / Q000032:analysis; D004195:Disease Models, Animal; D016228:Endothelial Growth Factors / Q000032:analysis / Q000378:metabolism*; D005260:Female; D006085:Graft Survival; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000032:analysis / Q000378:metabolism*; D008222:Lymphokines / Q000032:analysis / Q000378:metabolism*; D008969:Molecular Sequence Data; D018919:Neovascularization, Physiologic / Q000502:physiology*; D011184:Postoperative Period; D012333:RNA, Messenger / Q000032:analysis; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D012756:Sheep; D014182:Transplantation, Autologous; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D014945:Wound Healing / Q000502:physiology
D015415:Biomarkers; D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D020794:Receptor Protein-Tyrosine Kinases