|
Comment |
Implication of mu opioid receptor in the in vitro maturation of oocytes and its effects on subsequent fertilization and embryo development in mice. Olabarrieta E et al. (2019) Oocyte maturation is the process by which immature oocytes acquire all the necessary characteristics for successful fertilization. The endogenous opioid peptides have been suggested to have a role modulating this process. However, little is known about its implication and the effect of exposing oocyte maturation to opioids on the subsequent fertilization and embryo development. Hence, in the present work, we focused on elucidating the function of the mu opioid receptor (OPRM1) in the modulation of the oocyte maturation. We analyzed the expression and localization of OPRM1 in mice oocytes and granulosa cells by reverse-transcription polymerase chain reaction (RT-PCR) and immunocytochemistry. To observe the activity of the OPRM1, immature oocytes were incubated with morphine agonist and/or naloxone antagonist and we evaluated the PI3K/Akt and MAPK pathways, as well as the effect on the subsequent fertilization and embryo development. OPRM1 was present in mice oocytes and granulosa cells, changing its expression pattern depending on the maturation stage. Moreover, morphine, modulating PI3K/Akt and MAPK pathways, helped oocytes to reach blastocyst stage, which was reverted by naloxone. These results propose the OPRM1 as a possible therapeutic target for in vitro maturation culture medium, as it could improve the blastocyst rates obtained in the actual reproduction assisted techniques.//////////////////Expression and localization of opioid receptors during the maturation of human oocytes. Agirregoitia E et al. The endogenous opioid system has been characterized in some female reproductive organs, but little is known about the expression of these receptors in human oocytes. This study investigated the presence and differential distribution of the opioid receptors during the maturation of human oocytes. A total of 821 human oocytes from an intracytoplasmic sperm injection (ICSI) programme were studied including 213 at germinal-vesicle (GV) stage and 164 at metaphase-I (MI) stage and 444 failed fertilization metaphase-II (MII) oocytes. Additionally 31 MII oocytes corresponding to cases where ICSI was not attempted and 50 failed fertilization MII oocytes from the IVF programme were included. Western blot analysis revealed the presence of the delta (OPRD1), kappa (OPRK1) and mu (OPRM1) opioid receptors in human oocytes. The OPRK1 and OPRM1 immunostaining patterns changed during the maturation of the oocyte, while the OPRD1 pattern was the same throughout. In particular, OPRD1 were detected in peripheral tissue from the GV to the MII stage. OPRK1 were found peripherally at the GV stage, more internally at MI and homogeneously at MII. Finally, OPRM1 were located peripherally at the GV stage and homogeneously in MI and MII oocytes. Opioids may have a role in oocyte maturation, acting via receptors. The opioid system has been well characterized in the central nervous system, but it is now known that opioids also act in reproductive organs. However, little is known about the presence and function of this system in human oocytes and its role in their maturation. In this study, we investigated the presence and differential distribution of three (delta, kappa and mu) opioid receptors (proteins which bind the opioids) during the maturation of human oocytes. A total of 821 human oocytes (from 253 patients) not suitable for intracytoplasmic sperm injection (ICSI) or which did not develop into an embryo after ICSI were studied. Thus, we have verified the presence of the delta, kappa and mu opioid receptors in human oocytes. The kappa and mu localization changed during the maturation of the oocyte, while the Delta localization was the same throughout. In particular, the delta receptor was detected in the periphery of the oocyte. On the other hand, the kappa receptor was found peripherally at the beginning, more internally during maturation and homogeneously at the end of maturation. Finally, the Mu receptor was located peripherally at the beginning of maturation and homogeneously in the rest of the maturation stages. This finding suggests a possible role for opioids, acting via receptors, in the maturation of the oocyte.
|