Abstract
Testicular angiotensin converting enzyme (ACE) is known to play an essential role in the male reproduction and fertility. Data about tACE in cases of male infertility are quite scarce, and in this respect we aimed to study localization and distribution of tACE protein in the neck and mid-piece of spermatozoa from pathological samples in relation to sperm motility. The enzyme expression during capacitation and acrosome reaction was quantitatively assessed. In human ejaculated spermatozoa tACE is localized on sperm plasma membrane of the head, the neck and mid-piece of the tail. The immunoreactivity becomes stronger in capacitated spermatozoa followed by a decrease in acrosome reacted sperm. In different cases of semen pathology (oligozoospermia, asthenozoospermia and teratozoospermia) fluorescent signals in the neck and mid-piece are in punctate manner whereas in normozoospermia they were uniformly distributed. The expression area of tACE the neck and mid-piece was decreased in ejaculated and capacitated sperm from pathological semen samples compared to normospermia. Significant positive correlation was established between tACE area and progressive sperm motility, whereas with immotile sperm the correlation was negative. Our data suggest that proper distribution of tACE in the neck and mid-piece is required for normal sperm motility that could be used as a novel biomarker for male infertility.
Highlights
Infertility affects an estimated 15% of couples globally, amounting to 48.5 million couples
The sperm concentration in pathological samples was lower compared to normospermia and in oligozoospermia the parameter was quite lower than asthenozoospermia and teratozoospermia (Table 1)
Progressive sperm motility of pathological samples was significantly lower than normospermic men and the lowest value is found in asthenozoospermic men
Summary
Infertility affects an estimated 15% of couples globally, amounting to 48.5 million couples. Diagnosis in men consists of semen analysis, but in a large percentage of cases it is not sufficient to determine the complex etiological causes leading to idiopathic infertility [2]. In these patients, the use of assisted reproductive techniques such as ICSI (intracytoplasmic sperm injection) is suggested as a solution, but the choice of sperm with good quality remains a problem. A huge number of enzymes are found on the sperm membrane, involved in complex signaling pathways, ensuring the ability of sperm to go the long way from testicular differentiation, maturation and capacitation, hyper-activation to fusion with the egg and embryo development. One of the enzymes that has been shown to be important in male reproduction and fertility is angiotensin I—converting enzyme (ACE)—an important component of reninangiotensin system (RAS) ACE is a membrane bound Zn2+ metalloproteinase dipeptidyl carboxypeptidase that removes two residues from C terminus of certain peptides [3]
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