Currently, I am working on infertility issues among men. I want to study the expression level of a few genes that have a biased expression in human testis. But, it seems almost impossible to collect testis tissue from fertile men as they don't have any physiological problems. I have got several tissues from Azoospermic men because they have to pass through an ART procedure called PESA (percutaneous epididymal sperm aspiration) and seminiferous tubule tissues can be obtained from that. Unfortunately, this is not possible for the control/Fertile men. In this regard, how I will overcome this situation? Can normal sperm cells be used as a control?