Birth control for men? Scientists discover how to spot ‘winning’ sperm in breakthrough for non-hormonal male contraceptives

Researchers have discovered how to spot a winner among the millions of sperm racing to fertilize an egg – and it’s all down to minute characteristics that literally make the difference between life and death.

In their recently published report, the team of scientists at Yale University reveal that they’ve identified the key molecular characteristics that distinguish the eventual winners from the millions of losers in the seminal sprint.

Sperm tails are lined with pores that absorb calcium and help propel the microscopic swimmers through the female reproductive tract. Each pore is divided in four, and these subunits – named and numbered CatSper 1 through 4 – combine to control the mobility and navigation of the sperm. 

The Yale scientists, led by Jean-Ju Chung, describe the subunits as the sperm’s racing stripes, with one in particular found to be critical in deciding which sperm achieves the final goal of fertilization.

The team used 3D molecular imaging and artificial neural network modeling to visually track and quantify sperm as they travelled through the reproductive tracts of female mice shortly  after mating.

They found that CatSper1 yielded a clear competitive advantage – sperm that lost function in this subunit became immobile and were left in the oviduct dust, so to speak. 

However, this wasn’t the only means by which they could spot a winner. Champion sperm are apparently more streamlined, having shed a kind of cap known as an acrosome, affording them another leg-up on the competition. 

Research such as this may lead to breakthroughs in the fields of new treatments for infertility or, conversely, male birth control. For example, blocking the CatSper channel could lead to the development of non-hormonal contraceptives with few if any side effects for both men and women. 

“Better understanding how the fittest sperm cells are selected and how those left are eliminated after fertilization in the female reproductive tract can improve current strategies for assisted reproduction,” Chung said.

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