Acrosome size and kinematics of human spermatozoa
For spermatozoa to gain access to the oocyte for fertilization, lytic enzymes need to be released during the acrosome reaction. These enzymes, which are stored and transported within an organelle termed the acrosome, make it possible for spermatozoa to collectively penetrate the layers of cells and glycoproteins that surround and protect an oocyte. Acrosomes may thus be viewed as essential for fertilization and their shape, size and volume were examined morphometrically by utilizing automated morphometric analysis equipment. In addition to the acrosome being necessary for normal unassisted fertilization, spermatozoa also need the ability to migrate to the oocyte. Following zona pellucida binding, sperm tail thrust movement initiates zona penetration into the space created by the digestive action of the acrosomal enzymes. Therefore the motion characteristics of spermatozoa were also quantified in terms of kinematic properties. In the treatment of male sub fertility, assisted reproductive techniques are applied. In the application of such techniques, a motile sub-population of spermatozoa was obtained by employing a procedure (swim-up selection) that selects cells on the basis of their kinematic ability. This study presents an analysis of the morphometric and kinematic qualities of spermatozoa populations that are subjected to swim-up selection and investigates the relationship of these morphometrical and kinematic qualities. Computer-assisted semen analysis, swim-up selection and automated sperm morphology analysis tests were all used to evaluate spermatozoa populations. Results indicated that, irrespective of acrosome size, higher kinematic parameter measurements were observed post-swim-up. A significant inverse relationship between the population’s average acrosome size and a number of kinematic parameters was observed. Our results indicated that for a post-swim-up population of spermatozoa an increase in the average acrosome size was significantly related to a decrease in the kinematic parameters VAP, VCL and the VSL within the same population.