Andrology: Analysis of the oocyte activating capacity and chromosomal complement of round-headed human spermatozoa by their injection into mouse oocytes

Abstract

Intracytoplasmic sperm injection (ICSI) in the human is a very effective procedure which allows the fertilization of the majority of oocytes even in cases of extreme oligoasthenoteratozoospermia. Round-headed acrosomeless human spermatozoa, however, form an exception to this rule, because in about half of the couples with globozoospermia all oocytes remain unfertilized after injection. The incapacity of the spermatozoon to activate the oocyte following injection of round-headed spermatozoa could be the underlying mechanism. To investigate this hypothesis, activation rates of mouse oocytes injected with spermatozoa from a patient with globozoospermia were compared with those obtained after injection with normal spermatozoa. Of mouse oocytes surviving the injection with donor spermatozoa, 95% underwent activation, compared to none of the 88 mouse oocytes surviving the injection with round-headed spermatozoa. After fixation, prematurely condensed sperm chromosomes were found in these oocytes. Parthenogenetic activation of mouse oocytes (8% ethanol at 40 min after injection) injected with round-headed spermatozoa led to the activation of 96% of oocytes. These oocytes developed normally to the first mitosis and were fixed for analysis of the sperm karyotypes. The incidence of chromosomal abnormalities of round-headed spermatozoa (6%) was similar to that in spermatozoa from a fertile donor (9%). These data provide further information on the basic defect in cases of globozoospermia and demonstrate that globozoospermia is not associated with sperm karyotype abnormalities.

Genetic aspects of monomorphic teratozoospermia: a review

“…Lack of acrosome, which production is a postmeiotic event in spermatogenesis, and round sperm head are its main characteristics [27]. The acrosomeless spermatozoon is unable to go through the zona pellucida and fuse with the oolemma of the oocyte and fertilization failures have been attributed to a deficiency in oocyte activation capacity, even when ICSI is attempted [28][29][30]. Table 2).…”

Analysis of clinical outcomes with respect to spermatozoan origin after artificial oocyte activation with a calcium ionophore

“…The initial ooplasm calcium concentration increases within a few minutes of sperm-oocyte fusion, after which a sperm-derived factor (the oscillator) maintains this oocyte calcium level during normal fertilization [6]. Indeed, a lack of oocyte activation can lead to fertilization failure, as oocyte activation is triggered by the interaction between the oocyte and spermatozoa under normal conditions [7].…”

Pronuclear formation of freeze-dried canine spermatozoa microinjected into mouse oocytes

“…It is well known that the fertilizing capacity of mammalian sperm can be assessed using rodent oocytes [34][35][36]. Moreover, the spermatazoan chromosomes in a variety species can be easily visualized using these oocytes in combination with ICSI techniques [25][26][27][28].…”