Generation and localisation of monoclonal antibodies against fibroblast growth factors in ischaemic collateralised porcine myocardium.

Abstract

The collateral circulation plays a critical role in the prognosis of ischaemic heart disease, with a clear correlation between neovascularisation, infarction, and tissue recovery. The aim of the study was to address the question of whether endogenous acidic and basic fibroblast growth factors (FGF) participate in ischaemia induced collateral enlargement and development in the myocardium, and also which cells may represent the source of these growth factors. Eight pigs received an ameroid constrictor around the left circumflex coronary artery which, by slow coronary occlusion, induces ischaemia and collateral growth in the left ventricle. The degree of stenosis and development of collaterals were determined angiographically. About 14 d after constrictor implantation pigs were killed and hearts were excised and prepared for western blot analysis and immunohistochemistry. Monoclonal antibodies were raised against acidic and basic FGF, characterised for their specificity, and used for the localisation of growth factors in sections of ischaemic and normal pig heart. The eight pigs included in this study showed a gradual 70-100% left circumflex coronary stenosis about 14 d after implantation of the constrictor. Out of four pigs with a complete occlusion, three developed visible collaterals. Antibody staining to acidic FGF was detected only in hearts from pigs with complete occlusion of the coronary artery. The growth factor was localised in cardiomyocytes close to small necrotic tissue patches. In control tissue no acidic FGF staining was evident. Basic FGF could not be detected in ischaemic or in normal perfused pig hearts. These data show that (1) complete occlusion of the left circumflex coronary artery in pig hearts induces collateral growth; (2) cardiomyocytes are able to produce acidic FGF in response to ischaemia, thus providing a mitogen for endothelial cells; (3) endogenous basic FGF, which was not detected in normal or ischaemic pig hearts, appears not to play an important role in ischaemia induced collateral growth at the chosen time point of investigation.