FROM THE SPERMATID TO THE SPERMATOZOON - ARE THE CHANGES NECESSARY FOR EMBRYO DEVELOPMENT

The male gamete modifications during spermiogenesis were summarized in view to answer the question : ''Is if a risk for a baby conceived by fertilization with a spermatid to be different of a baby conceived wit h a spermatozoon?'' Cytoplasmic changes in spermiogenesis mainly conce rn the Golgi apparatus (acrosome vesicle), centrosomal material (flage llum), mitochondria (periaxonemal ring) and ooplasm volume (drastic re duction). These changes are not necessary in case of microfertilizatio n (ICSI) and their absence could be without consequences on post ferti lization development. Nuclear changes affect chromatin with the substi tution of histones by protamines to insure sperm ADN stability across male and female genital tracts. Spermatid gene traduction brings new p roteins which are related to fertilization (acrosomal enzymes, flagell um proteins, protamines...) and seem no longer useful after gametes fu sion. There is no report of genomic imprinting occuring during spermio genesis in mammals. Moreover, the important sperm changes during epidi dymal maturation (formation of disulfure bonds, acquisition of motilit y and of molecules for oocyte recognition, methylation of certain gene s...) were found not necessary for embryo development in case of ICSI with epididymal or testicular spermatozoa. Normal and fertile animals (mice and rabbits) were born from ICSI with spermatids originated from normal males; an animal model with sterile males delivering apparentl y normal spermatids is lacking. Although the risk for defectuous babie s from fertilization with spermatids is highly subjective, caution is needed and requires team competence, complete informed consent by the patients and exhaustive analysis of the methods used and results obtai ned Moreover the evident risk to ''reproduce'' the father infertility must be compared with the psychosocial injury induced by using the alt ernative option of donor insemination.