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Direct effect of macrophage migration inhibitory factor on sperm function: possible involvement in endometriosis-associated infertility.

Carli C, Leclerc P, Metz CN, Akoum A

Endocrinologie de la Reproduction, Centre de Recherche, Hôpital Saint-François d'Assise, Centre Hospitalier Universitaire de Québec (CHUQ), Faculté de Médecine, Université Laval, Québec, Canada.

OBJECTIVE: To evaluate the effect of macrophage migration inhibitory factor (MIF) on sperm capacitation, a maturational process that occurs in the female reproductive tract and enables spermatozoa to become fully competent at fertilizing the oocyte. DESIGN: Incubation of Percoll-washed spermatozoa with varying concentrations of human recombinant MIF or fetal cord serum (positive control). SETTING: Human reproduction research laboratories. INTERVENTION(S): Fresh semen samples obtained from healthy volunteers after a minimum of 2 days of sexual abstinence. MAIN OUTCOME MEASURE(S): Protein tyrosine phosphorylation by Western blotting, the acrosomal status upon binding to the Pisum sativum agglutinin conjugated to fluorescein isothiocyanate, and sperm motility by computer-assisted sperm analysis. RESULTS: MIF displayed a dose-dependent effect on the phosphotyrosine content of p105 and p81, the two major tyrosine-phosphorylated proteins associated with human sperm capacitation. A significant induction of tyrosine phosphorylation was seen at 2 ng/mL of MIF for both p105 and p81, but a trend for a down-regulation of the basal tyrosine phosphorylation level was noted at elevated concentrations (12-24 ng/mL). MIF pretreatment of spermatozoa resulted in a dose-dependent change in the acrosome reaction induced by the Ca(2+) ionophore A23187. After being increased at 1-4 ng/mL MIF with a statistically significant effect observed at 4 ng/mL, the acrosome reaction gradually decreased and fell below the control levels at higher concentrations. Furthermore, a significant decrease in the motility of spermatozoa was observed after exposure to an elevated concentration of MIF (12 ng/mL). CONCLUSION(S): The present data indicate that MIF may play a physiological role in sperm capacitation but may have deleterious effects on sperm function at abnormal pathophysiological levels, which suggests a role in endometriosis-associated infertility.

Published 9 October 2007 in Fertil Steril, 88(4): 1240-7.
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