Fertilization and early embrology: A sequential analysis of the effect of progesterone on specific sperm functions crucial to fertilization in vitro in infertile patients

The objective of these studies was to evaluate the modulatoryeffect(s) of progesterone on sperm functions crucial to fertilizationin infertile men with abnormal sperm parameters. A prospective,controlled study applying a sequential diagnostic analysis capableof identifying specific dysfunctions of the male gamete wasperformed. Patients (n = 14) were allocated to the study groupif they had a history of infertility of >1 year durationand after semen evaluation showed teratozoospermia (< 14%normal sperm forms as diagnosed by strict criteria) or terato-asthenozoospermia(< 50% progressive motility). After swim-up separation ofthe motile sperm fraction, the following functions were assessedwith and without previous exposure to progesterone (1.0 µg/ml):acrosome reaction (using Pisum sativum agglutinin), hyperactivatedmotility (using a computerized semen analyser), sperm-zona pellucidabinding (in the hemizona assay), sperm-zona pellucida penetration(in a sperm-zona penetration assay), and sperm-oocyte penetration(using the hamster zona-free oocyte/sperm penetration assay).Progesterone did not affect the percentage of acrosome-reactedspermatozoa after 1 or 3 h of incubation. Hyperactivated motilitywas significantly enhanced by progesterone after 1 h (12 ±4 versus 6 ± 2% in controls; P < 0.02). Although progesteronedid not affect sperm-zona binding, it significantly enhancedboth sperm-zona pellucida penetration (27 versus 12% in controls;P = 0.03) and sperm-oocyte penetration (15 versus 8% in controls;P < 0.05). Because those sperm functions enhanced by progesteroneare crucial to fertilization, the steroid may have value inthe treatment of some male-factor patients undergoing assistedreproductive therapy.