Picomolar gradients of progesterone select functional human sperm even in subfertile samples

Abstract

More than 1 million infertility treatments are practiced around the world per year, but only 30% of the couples succeed in taking a baby home. Reproductive technology depends in part on sperm quality, which influences not only fertilization but also embryo development and implantation. In order to provide a better quality sperm subpopulation, innovative sperm selection techniques based on physiological sperm features are needed. Spermatozoa at an optimum state may be selected by following an increasing concentration gradient of picomolar progesterone, a steroid secreted by the cumulus cells at the time of ovulation. In this study we developed a method to recruit spermatozoa at the best functional state, based on sperm guidance toward progesterone. The sperm selection assay (SSA) consists of a device with two wells connected by a tube. One well was filled with the sperm suspension and the other with picomolar progesterone, which diffused inside the connecting tube as a gradient. The sperm quality after the SSA was analyzed in normal and subfertile semen samples. Several sperm parameters indicative of sperm physiological state were determined before and after the SSA: capacitation, DNA integrity and oxidative stress. After the SSA, the mean level of capacitated spermatozoa increased three times in normal and in subfertile samples. The level of sperm with intact DNA was significantly increased, while sperm oxidative stress was decreased after sperm selection. Interestingly, the exposure to a progesterone gradient stimulated the completion of capacitation in some spermatozoa that could not do it by themselves. Thus, the SSA supplies a sperm population enriched with spermatozoa at an optimum physiological state that may improve the assisted reproductive technology outcome.

Natriuretic peptide type C induces sperm attraction for fertilization in mouse

“…It promoted a stable attractant gradient in the oviduct, which is consistent with previous studies showing that spermatozoa exhibit an attractive response and swim from the storage area to the fertilization site of ampulla during ovulation1314. Progesterone has been a candidate as the attractant the mammalian follicular fluid515253. However, sperm attraction is not correlated with progesterone levels in the follicular fluid1824.…”

Microfluidics for Sperm Selection

“…Cumulus cells secrete progesterone after ovulation, and human sperm respond to picomolar concentrations of this hormone [ 45 ]. These responses include redirection of sperm movement in vitro if the progesterone source is repositioned in the culture dish [ 46 ], and migration through microchannels towards the source of progesterone and accumulation in the vessels containing progesterone [ 47 ].…”

Infertility treatment, a matter of a lovely sperm?

“…6,7 By combining the ability of chemotaxis to select good spermatozoa with the use of progesterone as an attractant molecule, a new sperm selection assay (SSA) was recently developed. 8 …”