Acidic fibroblast growth factor mRNA is expressed by cardiac myocytes in culture and the protein is localized to the extracellular matrix.

Acidic and basic fibroblast growth factors are heparin-binding proteins that induce cellular proliferation, mesodermal development, and vascular growth. As such, they may be important in cardiac development and disease. To determine whether cardiac myocytes contain fibroblast growth factors, neonatal rat cardiac myocytes were studied in primary culture and compared to primary cultures of nonmyocyte cardiac cells. Northern blot analysis revealed a 4.0-kilobase mRNA in myocytes that hybridized to acidic fibroblast growth factor cDNA and was not detectable in nonmyocyte cultures. Western blot analysis demonstrated the accumulation of a 15-kDa peptide with immunological identity to acidic fibroblast growth factor in extracts of extracellular matrix from myocyte cultures that was not detectable in similar extracts of nonmyocyte extracellular matrix. No acidic fibroblast growth factor-like protein was detectable in cellular lysates from either myocyte or nonmyocyte cultures. These results demonstrate that neonatal cardiac myocytes express acidic fibroblast growth factor mRNA and deposit a protein with immunological identity to acidic fibroblast growth factor into the extracellular matrix. The results suggest that acidic fibroblast growth factor produced by cardiac myocytes may mediate, through both paracrine and autocrine mechanisms, such diverse processes as myocyte differentiation, cellular proliferation, and vascular growth in the heart.