In mammals, fertilization begins when the sperm successfully meet the oocyte, and it naturally occurs in vivo in the female reproductive tract. In vitro fertilization (IVF) is a process of modifying the environment so that sperm and oocytes can fertilize and subsequently develop outside their physiologic environment. Culture media and environmental manipulation are thus essential to maintain the gamet quality and developmental competency during the process. Some oocytes from large animals such as cattle, pigs, sheep, etc. require in vitro maturation (IVM) before being able to be used for fertilization. However, small animals like mice can be used immediately after hormone stimulation.
A key preparatory step is sperm capacitation, where sperm undergo biochemical changes to become fertilization-competent. In IVF, this is induced by specific media components. The timing of coincubating capacitated sperm with oocytes is critical. Insufficient capacitation leads to fertilization failure, while prolonged exposure can result in post-ovulatory oocyte aging, which compromises oocyte morphology, increases genetic errors, and significantly reduces developmental competence.
Here, I use ICR female and male mice to perform IVF.
Photos are personal documentation.
