Oocytectomy does not influence synthesis of hyaluronic acid by pig cumuluscells: Retention of hyaluronic acid after insulin-like growth factor-I treatment in serum-free medium

Mouse oocytes secrete a factor that enables cumulus cells to undergo expans ion in response to FSH (1 mu g/ml), whereas expansion of the porcine cumulu s oophorus has been shown to be independent of the oocyte. The aim of this study was to assess FSH-induced synthesis of hyaluronic acid (HA) by porcin e cumulus cells before and after oocytectomy. In addition, we studied the e ffect of insulin-like growth factor-I (IGF-I) on the ability of cumulus cel ls to synthesize and retain HA in response to FSH in serum-free medium. Por cine oocyte-cumulus complexes and complexes from which the oocytes had been removed by oocytectomy were cultured for 24 h in the presence of 2.5 mu Ci of D-[6-H-3]glucosamine hydrochloride, fetal calf serum (FCS, 5%), and FSH . After 24 h, incorporation of [H-3]glucosamine into HA was measured either in complexes alone (retained HA) or in medium plus complexes (total HA). S pecificity of incorporation of radioactivity into HA was confirmed by the s ensitivity to highly specific Streptomyces hyaluronidase. Our results sugge st that 1) the synthesis of HA by pig cumulus cells in vitro is stimulated by FSH and that oocytectomy does not change this synthesis; 2) oocytes do n ot influence retention of HA within the complex; 3) FSH-induced synthesis o f HA by cumulus cells is decreased in medium with polyvinylpyrrolidone (PVP )-supplemented (total and retained HA) compared to FCS-supplemented medium; 4) IGF-I enabled cumulus cells to synthesize HA in response to FSH in PVP- supplemented medium in a manner similar to that observed when serum is pres ent in the medium.