Use of failed-fertilized oocytes for diagnostic zona binding purposes after sperm binding improvement with a modified medium
Purpose: Because the availability of prophase oocytes for zona binding testing is limited, we compared sperm binding to the zona of failed- fertilized intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF) oocytes after incubation in a standard IVF medium and a specially composed binding improvement medium. Methods: Semen samples from nine patients and nine fertile donors were separated in parallel by the standard swim-up method in both media. Subsequently, hemizona assays were performed with prophase, failed-fertilized ICSI and IVF oocytes. Results: Sperm separation resulted in a significantly higher sperm count (P < 0.01) and progressive motility (P = 0.018) in binding improvement medium. Moreover, spermatozoa coincubated with hemizonae (prophase, failed-fertilized ICSI and IVF oocytes) in binding improvement medium bound significantly more to hemizonae than in the controls (P < 0.01). However, the hemizona index did not differ. Conclusions: Thus, the limited number of human zonae can be increased by the use of oocytes that failed to fertilize during ICSI or IVF. This will lead to a qualitative improvement of the diagnostic spectrum in male-factor infertility.