Infertility, despite its high incidence and long history in human society, is still somewhat of a mysterious health condition. Naturally, semen defects like low sperm concentration, low sperm motility, and poor sperm morphology are associated with reduced fertility. However, normal semen parameters are not a guarantee for normal fertility. Among semen defects, azoospermia (absence of germ cells in the semen) and Sertoli cell only syndrome (SCOS, absence of germ cells in the semen and testis, also known as Spermatogenic Failure) are the most serious pathological conditions. Currently, genetic factors are considered to play an important role in male factor infertility (1). However, for many years the medical and general public perception was that chromosomal aberrations and Y-chromosome microdeletions were mainly responsible for azoospermia and oligozoospermia (2, 3).
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