INHIBITION OF PRECARDIAC MESODERM CELL-PROLIFERATION BY ANTISENSE OLIGODEOXYNUCLEOTIDE COMPLEMENTARY TO FIBROBLAST GROWTH FACTOR-II (FGF-2)

This laboratory recently reported the occurrence of concentrated deposits of fibroblast growth factor-2 (FGF-2; basic FGF)-like proteins in the sarcoplasm of embryonic cardiac myocytes from the earliest stage of avian heart development (M. H. Parlow, D. L. Holender, N. P. KokanMoore, and J. Lough, Dev. Biol. 146, 139, 1991). To determine the role, if any, of FGF-2 during embryonic cardiogenesis, the proliferative and functional effects of treating cultured anterior lateral plate mesoderm from Hamburger-Hamilton stage 6 embryos with antisense oligodeoxynucleotide (ODN) complementary to FGF-2 mRNA were determined. Within 2 days of culture in defined medium, the explanted monolayer normally differentiates into a multilayer of proliferative cells that express sarcomeric α-actin and exhibit rhythmic contractions. The inclusion of 25 μM ODN that is complementary to the second exon of chicken FGF-2 mRNA caused a 50% inhibition in these cells' proliferative ability as judged by incorporation of 5′-bromodeoxyuridine; contractility was similarly inhibited. These effects were prevented by including recombinant human FGF-2 protein in the medium. Treatment with sense ODN did not cause inhibition. Inhibition of FGF-2 protein synthesis in the explanted tissue by antisense ODN was verified by immunoprecipitation analysis. These results point to a critical role for FGF-2 in the autocrine regulation of proliferation, and perhaps differentiative function, of embryonic cardiac myocytes. © 1993 Academic Press, inc.