The angiogenic peptide vascular endothelial growth factor is expressed in foetal and ruptured tendons

The Achilles tendon is one of the most common sites of injury and rupture. Evidence suggests that local vascularisation is involved in this aetiology. We investigated the expression of one important angiogenic factor, the vas cular endothelial growth factor (VEGF), in normal and pathologic human Achi lles tendons using immunohistochemical, biochemical, molecular and cell bio logy methods. VEGF could be immunostained in tenocytes of ruptured and foet al Achilles tendons, but not in normal adult ones. In microvessels, the VEG F receptor VEGFR-1 (flt-1) could be visualised as well. High VEGF levels we re measured in homogenates from ruptured adult, lower ones in foetal and ne gligible concentrations in normal adult Achilles tendons using enzyme-linke d immunoassay (ELISA) and Western blot experiments. Reverse transcriptase-p olymerase chain reaction (RT-PCR) showed that the splice variants VEGF(121) and VEGF(165) are exclusively expressed. In tenocytes cultivated from newb orn rat Achilles tendons, hypoxia or epidermal growth factor (EGF) raised V EGF production moderately whereas their combination resulted in a strong, s ynergistic induction. These results prove the presence of an angiogenic pep tide and vascularisation in ruptured and foetal tendons and support the vie w that microtrauma or degeneration in the Achilles tendon precedes its rupt ure.