Removal of sperm tail using trypsin and pre-activation of oocyte facilitates intracytoplasmic sperm injection in mice and rats

We examined various methods to enhance the accessibility of intracytoplasmic sperm injection (ICSI) technology to more users by making the technique easier, more efficient, and practical. First, the methods for artificially removing the mouse sperm tail were evaluated. Trypsin treatment was found to efficiently remove the sperm tails. The resultant sperm cells had a lower oocyte activation capacity; however, the use of activated oocytes resulted in the same fecundity as that of fresh, untreated sperm. Pre-activated oocytes were more resistant to physical damage, showed higher survival rates, and required less time per injection. Testing this method in rats yielded similar results, although the oocyte activation method was different. Remarkably, this method resulted in higher birth rates of rat progeny than with conventional methods of rat ICSI. Our method thereby streamlines mouse and rat ICSI, making it more accessible to laboratories across many disciplines.