Parathyroid-produced angiopoietin-2 modulates angiogenic response.
BACKGROUND
Upon explant, parathyroid tissue (PTH) upregulates vascular endothelial growth factor (VEGF), a potent endothelial cell mitogen, yet PTH induces a more robust angiogenic response than VEGF alone. This implies that other angiogenic factors are also produced. We tested PTH for production and function of angiopoietin-2 (Ang-2), a protein known to modulate VEGF response.


METHODS
With use of reverse transcriptase-polymerase chain reaction and SELDI (Surface Enhanced Laser Desorption/Ionization) (Ciphergen, Freemont, Calif) technology, we tested explanted PTH for Ang-2 production and determined the time sequence of Ang-2 upregulation. With use of an in vitro rat microvessel angiogenesis assay, we determined the angiogenic response to PTH-produced Ang-2.


RESULTS
Ang-2 messenger RNA was induced within 1 hour of parathyroid explant, with a maximum level detectable at 24 hours. Ang-2 protein production was maximal at 24 hours, with elimination by 48 hours. Ang-2 supplemented gels appeared to prompt earlier angiogenic induction, whereas sequestration of Ang-2 with soluble Tie2 receptor appeared to delay angiogenic induction. Soluble Tie2 treatment did not significantly decrease cumulative microvessel length, and no significant increase in neovessel length was seen with Ang-2 supplemented gels.


CONCLUSIONS
PTH upregulates Ang-2 upon explantation, with peak protein production by 24 hours. Ang-2 appears to functionally enhance initiation of PTH-induced angiogenesis, although the ultimate neovessel length appears to be dependent on other PTH-produced factors.
Carter
W B
WB
Division of Surgical Oncology, University of Maryland, Baltimore, MD 21201, USA.
Ward
M D
MD
D042702:Angiopoietin-2; D002478:Cells, Cultured; D016228:Endothelial Growth Factors / Q000494:pharmacology; D006801:Humans; D008222:Lymphokines / Q000494:pharmacology; D018919:Neovascularization, Physiologic; D010280:Parathyroid Glands / Q000378:metabolism*; D011506:Proteins / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D042702:Angiopoietin-2; D016228:Endothelial Growth Factors; D008222:Lymphokines; D011506:Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors