Sperm Chemorepulsion, a supplementary mechanism to regulate fertilization. Human reproduction

CUBILLA MARISA A; GUIDOBALDI HÉCTOR ALEJANDRO; MORENO AYELÉN; MOLINO MV; BAHAMONDES L; GIOJALAS LAURA CECILIA

HUMAN REPRODUCTION

OXFORD UNIV PRESS

Año: 2017

0268-1161

STUDY QUESTION: Are human spermatozoa able of chemorepulsive behaviour?SUMMARY ANSWER: Capacitated human spermatozoa are able to be chemorepelled by synthetic Progesterone Receptor Ligands(sPRL, known as contraceptives) and zinc (a cation released by the oocyte upon fertilization).WHAT IS KNOWN ALREADY: Moving cells can be oriented towards or against a molecular gradient, processes called chemoattractionand chemorepulsion, respectively, which have been described in unicellular organisms such as amoebas and bacteria, to organismic cells suchmacrophages and developmental cells. In the case of spermatozoa, chemoattraction may help the finding of an oocyte and has been widelystudied in various invertebrate and mammalian species; however, chemorepulsion has not yet been verified in spermatozoa.STUDY DESIGN, SIZE, DURATION: This is an in vitro study involving human, rabbit and mouse spermatozoa which were used to perform3?30 experiments per treatment.PARTICIPANTS/MATERIALS, SETTING, METHODS: Human sperm samples were obtained by masturbation from healthy donorswho gave written consent. Only those samples exhibiting normal semen parameters according to current WHO criteria were included in thestudy. Rabbit spermatozoa were obtained by artificial vagina whereas mice spermatozoa were obtained from epididymis. The sperm selectionassay (SSA), originally designed to evaluate sperm chemoattraction towards progesterone (P), and a video-microscopy and computer motionanalysis system were used to test sperm chemorepulsion. Additional kinetic parameters were also determined by video-microscopy andcomputer motion analysis. In some experiments, the level of induced acrosome-reacted spermatozoa was determined. Rabbit matingmanipulation was achieved to perform the sperm?oocyte co-incubation assay.MAIN RESULTS AND THE ROLE OF CHANCE: Sperm accumulation in the well containing 100 pg/ml of sPRL was lower than the culturemedium negative control (P < 0.05). The percentage of sperm persistence against the well containing 100 pg/ml ulipristal acetate (UPA)(P = 0.001), and the percentage of sperm showing a repulsive pattern of movement (a linear trajectory followed by a transitional one afterturning against the UPA), were higher than the culture medium negative control (P = 0.049). Sperm accumulation was diminished whenspermatozoa where exposed to a homogeneous distribution of 100 pg/ml sPRL combined with a chemotactic gradient of progesterone (P),with respect to the culture medium negative control (P < 0.05). These results were reverted when non-capacitated spermatozoa were usedto perform the same experimental settings. The accumulation of spermatozoa against 100 pg/ml sPRL was lower than the culture mediumnegative control also in rabbits and mice (P < 0.05). The relative number of rabbit spermatozoa arriving to the vicinity of the oocyte wasdiminished under the presence of 100 pg/ml UPA (P = 0.004). Sperm accumulation in the well containing zinc was decreased compared tothe culture medium negative control (P < 0.05). A homogeneous distribution of zinc combined with a gradient of 10 pM P, was lower thanthe culture medium negative control (P = 0.016). The results were quite reproducible with two different methodologies (accumulation assayand video-microscopy combined with computer motion analysis), in three mammalian species.