Fertilization- Sperm Can Smell — And the Ability Differs From Man to Man

Fertilization- Sperm Can Smell — And the Ability Differs From Man to Man

Author Name:Dandelion Medical Animation

Youtube Channel Url:https://www.youtube.com/@DandelionMedicalAnimation

Youtube Video URL:https://www.youtube.com/watch?v=O5eQeCaA4VQ



Transcript:
(00:01) The idea that sperm can smell their way to the egg is one of the most fascinating discoveries in reproductive biology. Sperms actually use the exact same hardware that your tongue and nose use to scan its environment for survival and compatibility. The nose of a sperm cell is not just a metaphor.
(00:26) It is a molecular twin to the system in your head. Sperm cells actually have odorant receptors, the same type of protein receptors found in the nose. In the nose, receptors are located on the psyia of olfactory sensory neurons. These receptors detect sense in the air. The nose can detect certain smells even in tiny amounts. These signal goes to the olfactory bulb in the brain to create the perception of smell.
(00:55) on the sperm. These same receptors sit on the surface of the sperm, specifically in the midpiece and tail area, allowing the sperm to sense the direction of a scent while swimming. The scent they are picking up is primarily progesterone and other specialized molecules in the follicular fluid.
(01:15) They can detect a concentration gradient of progesterone or other attractants at incredibly low levels. They don't just hit a wall of scent. They can tell if the concentration is 1% higher on the left side of their tail than the right, allowing them to steer. The detected signals then triggering a calcium influx that changes the swimming pattern from a search mode to a power stroke. Hyperactivation.
(01:45) Just as some people are super tasters or have a very sensitive sense of smell, sperm sensitivity varies from man to man, research has found a fascinating link. In the early 1990s, scientists found DNA for nose receptors, O1D2, inside human testicles. They knew sperm had a nose, but didn't know which scent unlocked it.
(02:13) Researchers took the genetic code for the sperm's specific receptor and pasted it onto lab grown cells. The scientists then began a massive blind taste test for cells. A massive library of over 100 different chemical scents including fruit scents, citrus and apple musky scents, woody and earth scents.
(02:40) They then sprayed these cells with a library of hundreds of different scents to see which one caused a reaction. Most did nothing. But when they hit bourjenol, the chemical that gives lily of the valley its smell, the cells lit up with a massive reaction. It was the strongest match they had ever seen. Once they knew boronol was the key to that specific receptor, they went back to real human sperm.
(03:11) They put the sperm in a tiny tube and created a cloud of bourjel at one end. The result was incredible. The sperm didn't just swim faster. They actually reoriented their bodies directly toward the scent. The most surprising part of the experiment came when researchers compared the results to the men themselves. Men who had a high sensitivity to bourjonal, the chemical that smells like lily of the valley, had sperm that were expert navigators.
(03:44) Conversely, some men with unexplained infertility were found to have a very poor sense of smell specifically for boronal, a condition called anosmia for bourjginal. So the decreased perception for boronel is thought to be linked to male idiopathic infertility. If you have a genetic variation that makes your O1D2 receptor more sensitive, both your nose and your sperm will be high performance trackers for that specific scent.
(04:19) If a woman's follicular fluid smells attractive to a sperm, the sperm will sniff out the trail. It transforms our view of sperm from simple swimmers into sophisticated sensory cells. This process is scientifically known as chemotaxis, the movement of an organism or cell in response to a chemical stimulus. The smell is essentially a chemical encoded message about the woman's immune system genes MHC.
(04:52) And the sperm actually respond to chemical signals released by the egg and surrounding cells. Although scientists are still studying exactly how this process works,