(Pro)renin Receptor Is Present in Human Sperm and It Adversely Affects Sperm Fertility Ability

Abstract

Sperm fertility ability may be modulated by different molecular systems, such as the renin-angiotensin system (RAS). Although renin is one of its most relevant peptides, the presence and role of the (pro)renin receptor (PRR) is completely unknown. We have proved for the first time the existence of PRR and its transcript in human sperm by western blot and RT-PCR. Immunofluorescence studies showed that this receptor is mainly located in the apical region over the acrosome and in the postacrosomal region of the sperm head and along the sperm tail. In addition, this prospective cohort study also proves that semen samples with higher percentages of PRR-positive spermatozoa are associated with poor sperm motility, worse blastocyst development and no-viable blastocysts. Our results provide insight into how PRR play a negative role in sperm physiology that it may condition human embryo quality and development. An in-depth understanding of the role of PRR in sperm fertility can help elucidate its role in male infertility, as well as establish biomarkers for the diagnosis or selection of sperm to use during assisted reproductive techniques.

Keywords: assisted; embryonic development; human; prorenin receptor; reproductive techniques; semen analysis.

Figure 1

Expression and localization of PRR in human sperm cells. (A) A representative of midori-green-stained gels of the RT-PCR products for ATP6AP2 and ACTB in human sperm from a pool of five normozoospermic semen samples (Spz) and kidney (Kd). Primers without cDNA were used as negative control. (B) A representative immmunoblot of PRR in human sperm from a pool of five normozoospermic samples (Spz) and kidney (kd). (C) A representative plot of PRR-positive sperm population analyzed by flow cytometry. Plots of blank control (purple) without both primary and secondary antibodies, negative primary antibody control (light blue) as the same concentration as the primary antibody and with secondary antibody, negative secondary antibody control (deep blue) with secondary antibody alone, and plot of PRR-positive sperm population (green). Nucleuses were stained with Hoescht 33258, n = 2. (D) Immunofluorescence analysis of the PRR in human sperm cells. (D1) PRR Positive sperm cells (green). (D2) Negative secondary antibody control (red). (D3) Phase-contrast image of the human sperm cells. Nucleuses were stained with Hoescht 33258. Representative photomicrographs are shown; n = 3. Scale bar: 1 µm.

Figure 2

Graphic representation of the scoring and viability of the embryo on day 5 and day 6 and the association with the percentage of PRR-positive spermatozoa. Percentage of PRR-positive spermatozoa in association with the degree of development of the embryos on days 5 (A) and day 6 (B). Statistical differences among all groups were evaluated by using the Kruskall–Wallis test, followed by the Mann–Whitney U-test between two groups. MC: compact morula stage; BT: early blastocyst; BC: expanding blastocyst; BE: expanded blastocyst; BHi: hatching/hatched blastocyst; BD: blocked and degenerated. Blastocyst viability of embryos on day 5 (C) and day 6 (D). Statistical differences were examined between both groups by using the Mann–Whitney U-test. * Significant difference between groups (p < 0.05); ** high significant difference between groups (p < 0.01).