Fibroblast growth factor 2 isoforms and cardiac hypertrophy.

Fibroblast growth factor 2 (FGF-2), a multifunctional polypeptide that affects cell growth and differentiation and becomes upregulated by stress, is expressed as AUG-initiated 18 kDa FGF-2 or CUG-initiated 21-34 kDa (hi-FGF-2) isoforms. Animal models have provided strong evidence that FGF-2 is essential for the manifestation of overload- and angiotensin-induced cardiac hypertrophy. Nevertheless, studies to-date have not discriminated between the activities of 18 kDa FGF-2 and hi-FGF-2. Our recent work has pointed to a potent pro-hypertrophic effect of added hi-FGF-2, and a pro-apoptotic effect of sustained intracrine hi-FGF-2 signaling. In the future, it will be important to differentiate between the activities of the different FGF-2 isoforms in the context of adaptive and maladaptive myocardial hypertrophy and heart failure. Based on all available evidence, we propose that while the 18-kDa FGF-2 is a component of an adaptive trophic response, a switch to hi-FGF-2 accumulation would exacerbate hypertrophy and contribute to cell death, thus driving the myocardium towards a maladaptive phenotype.