In vivo versus in vitro sperm selection

The separation of human spermatozoa is an important step in therapy of human infertility. Given that male fertility is decreasing and, as a result, fertilization techniques based on microinjection of sperm into the cytoplasm are being used more intensively, this question is becoming increasingly relevant. In recent years, microfluidic sperm processing techniques have been increasingly used. These methods are simple and easy to use, however, the question is to what extent they select the correct sperm. They are essentially based mainly on motility and do not reflect other navigational approaches such as chemotaxis, thermotaxis or rheotaxis. This review compares traditional, advances and novel in vitro methods of sperm separation which are commonly used during human infertility therapy in context of in vivo sperm separation in female reproductive system.