ULTRASTRUCTURE OF GAMETES AND INTRACYTOPLASMIC SPERM INJECTION - THE SIGNIFICANCE OF SPERM MORPHOLOGY

The aim of this study was to determine characteristic malformations of sperm ultrastructure in patients with severe subfertility undergoing intracytoplasmic sperm injection (ICSI), Although light microscopy (LM ) can reveal major abnormalities of the three parts of the spermatozoo n (head, mid-piece and flagellum), the various cell organelles of the spermatozoon and their fine structure remain unevaluated by LR;I, Insi ght into the submicroscopic organization of the spermatozoon and its c omplex organellar system may contribute to a better understanding of t he preconditions for success or failure of fertilization, An in-depth evaluation of semen quality by transmission electron microscopy (TEM) can improve the diagnosis of male subfertility and can give substantia l information about the fertilizing competence of spermatozoa, Thus, i n this study 56 ejaculated sperm samples from patients with severe mal e subfertility or previous failed attempts at in-vitro fertilization w ere assessed by LM and TEM prior to ICSI to evaluate the most importan t sperm defects causing extreme subfertility, LM analysis was performe d according to World Health Organization criteria, It could be confirm ed that severe head defects are mostly involved in long-term infertili ty and fertilizing failure in classical IVF treatments, The most frequ ent head defects are disorders of the nuclear membranes and the acroso mal cap and disorganization of the chromatin structure. These defects of sperm fine structure seem to be associated with dysfunctional sperm -oocyte recognition, binding and fusion with the oolemma, Chromatin al terations and signs of decondensation or karyolysis are frequently ass ociated with a deterioration of the nuclear membranes and may be due t o impaired spermiogenesis. However, our results and the success of ICS I proved that severe sperm defects have no predictive value and do not impair the fertilization process, and also that the maturity of sperm atozoa does not play an important role, Fine structure analysis reveal ed the pleiomorphology and heterogeneity of human spermatozoa.