This project seeks to understand the mechanisms responsible for mammalian sperm transport through the female reproductive tract to the site of fertilization, and for subsequent sperm penetration through the ovum vestments. We have approached these objectives by focusing directly on the motions of the spermatozoa, and by seeking to determine the forces which push the sperm forward and the resistances which must be overcome. Using high-speed videomicrography, we will obtain detailed data on sperm movement characteristics which will serve as input to hydrodynamic computations of how hard sperm thrust through cervical mucus, the cumulus, and zona pellucida. Such computations require new hydrodynamic theory, which we will develop. At the level of the cervix, we will study the extent to which pressure forces created by the female viscera assist spermatozoa in passage through the mucus. We will study the details of the sperm-cervix interaction in vivo by surgically removing the cervix after insemination and analyzing the local properties of the mucus, and the behavior of sperm in the lumen and epithelial crypts. We will study whether the products of ovulation influence sperm motility during final approach to the cumulus. We will build and apply a mechanical microprobe that mimics the microscale forces applied by sperm against the mucus and ovum vestments. Use of the probe will enable us to measure the resistances which sperm experience, and whether they are altered by sperm enzymes. Our goal is to understand details of factors which control sperm transport and fertilization, and thereby to provide new insights into their analysis and alteration for contraceptive and fertility-enhancing purposes.
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