Characterization of a recombinant porcine follistatin in a heat shock expression system

The role of follistatin in ovarian function has yet to be fully elucidated; it is present in low concentration in vivo and it is difficult to obtain suitable quantities of follistatin for characterization. We have cloned porcine follistatin cDNA in an expression system that uses the heat shock protein promoter BoHSP70. Recombinant follistatin with apparent molecular masses of 39, 46, 48, 50 kDa was expressed and secreted into culture medium at concentrations of 400–500 μg × 20 mL -1 × 150 cm -2 flask (4 × 10 7 cells). In ligand blots, the recombinant follistatin was shown to be immunologically similar to native follistatin and to bind to recombinant activin A. Porcine granulosa cells dissected from 1–3 mm follicles from immature gilts were cultured with recombinant follistatin or with a follistatin monoclonal antibody to examine the activity of the recombinant follistatin. At a physiologically relevant concentration of 1 μg mL -1 the recombinant porcine follistatin suppressed the accumulation of estradiol-17β (P < 0.05). There was a trend for estradiol-17β accumulation in the presence of 10 μg mL -1 of monoclonal anti-follistatin antibody (P = 0.1). This expression system consistently produced large quantities of recombinant porcine follistatin, which is immunologically and biologically similar to follistatin, and is capable of independently inhibiting estratiol-17βproduction in vitro. Key words: Porcine, follistatin, heat shock promoter, glycoprotein, ovary, estradiol