Progesterone from the cumulus cells is the sperm chemoattractant 1 secreted by the rabbit oocyte cumulus complex

GUIDOBALDI HA; TEVES, ME; UÑATES, DR; ANASTASÍA, A; GIOJALAS, LC

PLOS ONE

PUBLIC LIBRARY SCIENCE

Año: 2008 vol. 3 p. 3040 - 3049

1932-6203

Sperm chemotaxis in mammals have been identified towards several femalesources as follicular fluid (FF), oviduct fluid, and conditioned medium from thecumulus oophorus (CU) and the oocyte (O). Though several substances wereconfirmed as sperm chemoattractant, Progesterone (P) seems to be the bestchemoattractant candidate, because: 1) spermatozoa express a cell surface Preceptor, 2) capacitated spermatozoa are chemotactically attracted in vitro bygradients of low quantities of P; 3) the CU cells produce and secrete P afterovulation; 4) a gradient of P may be kept stable along the CU; and 5) the mostprobable site for sperm chemotaxis in vivo could be near and/or inside the CU.The aim of this study was to verify whether P is the sperm chemoattractantsecreted by the rabbit oocyte-cumulus complex (OCC) in the rabbit, as amammalian animal model. By means of videomicroscopy and computer imageanalysis we observed that only the CU are a stable source of sperm attractants.The CU produce and secrete P since the hormone was localized inside thesecells by immunocytochemistry and in the conditioned medium by enzymeimmunoassay. In addition, rabbit spermatozoa express a cell surface P receptordetected by western blot and localized over the acrosomal region byimmunocytochemistry. To confirm that P is the sperm chemoattractant secretedby the CU, the sperm chemotactic response towards the OCC conditionedmedium was inhibited by three different approaches: P from the OCCconditioned medium was removed with an anti-P antibody, the attractantgradient of the OCC conditioned medium was disrupted by a P countergradient, and the sperm P receptor was blocked with a specific antibody. Weconcluded that only the CU but not the oocyte secrete P, and the latterchemoattract spermatozoa by means of a cell surface receptor. Our findingsmay be of interest in assisted reproduction procedures in humans, animals ofeconomic importance and endangered species.