Chromosomal alterations and male infertility.

Reduced male fertility can be caused by genetic factors affecting gamete formation or function; in particular, chromosome abnormalities are a possible cause of male subfertility as shown by their higher frequency in infertile men than in the general male population. Meiotic studies in a number of these males have shown spermatogenesis breakdown, often related to alterations in the process of chromosome synapsis. Indeed, any condition that can interfere with X-Y bivalent formation and X-chromosome inactivation is critical to the meiotic process; furthermore, asynapsed regions may themselves represent a signal for the meiotic checkpoint that eliminates spermatocytes with synaptic errors. We performed cytogenetic, hormonal and seminal studies in 333 infertile patients selected because azoospermic, severely oligozoospermic or normozoospermic with failure to fertilize the partner's oocytes in an in vitro fertilization (IVF) program. Our findings: 1) confirm the high incidence of chromosomal anomalies among infertile males; 2) highlight the relevance in male infertility of quantitative/positional modifications of the constitutive heterochromatin; and 3) underline the relevance of cooperation between andrologists and cytogenetists prior to every kind of assisted reproduction, above all prior to intracytoplasmic sperm injection, in which selective hurdles eliminating abnormal germ cells are bypassed.