We all know that after the sperm contacts the zona pellucida, an acrosome reaction occurs and penetrates the zona pellucida. However, many studies have found that all sperm in the ampulla have already had AR reactions, and when the sperm reaches the isthmus, most of the sperm have also had AR reactions. What puzzles me now is that the egg is surrounded by granular cells. How can the sperm that undergo the acrosome reaction be able to fertilize the egg? Did I miss any important information? Can experts in related fields provide me with relevant information or literature? Thank you very much!
Hi Rui,
Your information is true, but I want to add some extra. Yes, sperm cells must complete capasitation process (CP) and ready for acrosome reaction(AR). Of course and high probably, sperm cells complete CP and ready for AR. However, they must attach and contact with zona pelicuda (ZP) receptors, which is specific for species. I mean (for instead) sperm cells of ram can only attach ovine oocytes and cant attach and start AR for other species...
And also oocytes surrounded by some cells (cumulus oophorus and corona radiata) generally denued oocytes reach the fertilization area "ampulla section of oviduct"... Even if zona pellucida surronded by corona raidata cells only do sperm cells attach and carry out AR if touch ZP3 receptors.
I hope my information is beneficial for you...
Dont hesitate for discussion... Go on...
Umut
I have always had a bold conjecture that a fraction of spermatozoa entering the isthmus of the oviduct undergo an acrosome reaction and that the acrosomal enzymes released would disperse the cumulus layer. Eventually, the remaining capacitated sperm can bind to the denuded egg and initiate the acrosome reaction. Umut Cagin Ari
@ Rui Chen ,
In my opinion and experience, I have seen that one sperm cell is not enough acrosome enzymes and alot of sperm cells work together however, only one sperm cell physically pass to zona pelicuda and start poly spermic block with cortical granules relasing.
If there are remaining cumulus cells, hyarulinidase can be effective for this aim. However, generally denuded oocyte reach the isthmus-ampullar region. In IVF, we use COCs with expanded cumulus layers after IVM and therefore we obtain expanded cumulus cells and this stiuation is very difficult for sperm cells to pass even if they have hyarulinidase enzyme. So removing of cumulus cells with chemical (trypsine) and phsical (pipetting) processes are powerfully advaced. Otherwise, fertilization rates decrease...
Hi again Rui CHEN,
I think there is no one explain of a problem or physiological process. We can produce a lot of solves or develop alot approach to problem. Therefore imagination is more important than knowledge... If A. Einstein said that... He should have know something...
Fertilization is a complex process and especially capacitation and acrosome reaction and also sperm penetration could not exactly explain for all species including mammalians.
Could you explain why bilion and trilion sperm cells produce and release for fertilization. This is bad usage of limited sources in evolution, isn't it.
Why this way has been expected during evalution? Because the best and working way is this. Others can not live today.
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