Masataka Majima (1), Masako Isono (1), Yasuhiro Ikeda (1), Izumi Hayashi
(1), Ko Hatanaka (1), Yoshiteru Harada (1), Osamu Katsumata (2), Shohei
Yamashina (2), Makoto Katori (1) and Shouzo Yamamoto (3)
(1) Department of Pharmacology and (2) Department of Anatomy, Kitasato University School of Medicine, Kanagawa 228, Japan
(3) Department of Biochemistry, Tokushima University School of Medicine, Tokushima 770, Japan
Abstract: Angiogenesis in rat sponge implants, as determined from the concentration of hemoglobin in the sponge granuloma tissues, was gradually increased over a 14-day experimental period. The inducible cyclooxygenase COX-2 was detected in the sponge granuloma tissues at day 4 by Western blot analysis using specific mouse COX-2 antibody. Angiogenesis in the sponge implants was enhanced by daily topical injections of human recombinant basic fibroblast growth factor (bFGF) or human recombinant epidermal growth factor (EGF) (100 or 1000 ng/sponge/day) for 4 days. These treatments clearly enhanced the expression of COX-2 in the sponge granuloma tissues. In immunohistochemical studies, COX-2-positive staining was mainly observed in the endothelial cells of the neovasculature and in the fibroblasts of the granuloma capsule. Administration of the selective COX-2 inhibitor NS-398 (p.o., 3 mg/kg, 3 times a day) for 14 days significantly inhibited the angiogenesis. The angiogenesis enhanced with bFGF or EGF (day 4) was inhibited by administration of indomethacin or NS-398, both in the above regimen, and fell to the level obtained without growth factor treatment. These results suggest that COX-2 induced in the sponge granuloma tissues may participate in neovascularization through prostaglandin formation.
Keywords: Angiogenesis, Cyclooxygenase (COX)-2, Sponge implant, Growth factor, Immunohistochemistry