MSOME and Sperm Chromatin Status

Abstract

Motile sperm organelle morphology examination (MSOME) involves the use of differential interference contrast microscopy (also called Nomarski contrast microscopy) to observe motile human spermatozoa at high magnification (at least 6,300×). Hence, this technique can evidence sperm head vacuoles that are not necessarily seen at lower magnifications—particularly if the vacuole is small (i.e., if it occupies <4 % of the sperm head’s area). However, a decade after the introduction of MSOME, the nature of sperm head vacuoles is still unclear. Are the vacuoles physiological or pathological? Are they linked to specific nuclear characteristics? And is the presence of one or more vacuoles a sign of a low-quality nucleus? Here, we discuss the links between vacuoles and the chromatin status of human spermatozoa. Our own research and the literature data prompt us to conclude that sperm-head vacuoles are nuclear in nature and are closely linked to chromatin condensation failure.