Spermatozoa telomeres determine telomere length in early embryos and offspring

Offspring telomere length (TL) has been correlated with paternal TL, but the mechanism for this parent of origin-specific inheritance remains unclear. The objective of this study has been to determine the role of spermatozoa TL in embryonic telomere lengthening by using two mouse models showing dimorphism in their spermatozoa TL: Mus musculus vs Mus spretus and old vs young Mus musculus. Mus spretus spermatozoa displayed a shorter TL than Mus musculus. Hybrid offspring exhibited lower TL compared with Mus musculus starting at the two-cell stage, before the onset of telomerase expression. To analyze the role of spermatozoa telomeres in early telomere lengthening, we compared the TL in oocytes, zygotes, two-cell embryos and blastocysts produced by parthenogenesis or by fertilization with Mus musculus or Mus spretus spermatozoa. TL was significantly higher in spermatozoa compared with oocytes, and it increased significantly from the oocyte to the zygote stage in those embryos fertilized with Mus musculus spermatozoa, but not in those fertilized with Mus spretus spermatozoa or produced by parthenogenesis. A further increase was noted from the zygote to the two-cell stage in fertilized Mus musculus embryos, whereas hybrid embryos maintained the oocyte TL. Spermatozoa TL shortened with age in Mus musculus and the offspring from young males showed a significantly higher TL compared with that fathered by old males. These significant differences were already noticeable at the two-cell stage. These results suggest that spermatozoa telomeres act as a guide for telomerase-independent telomere lengthening resulting in differences in TL that persist after birth.

CB1 cannabinoid receptor drives oocyte maturation and embryo development via PI3K/Akt and MAPK pathways

Endocannabinoids have been recognized as mediators of practically all reproductive events in mammals. However, little is known about the role of this system in oocyte maturation. In a mouse model, we observed that activation of cannabinoid receptor 1 (CB₁) during in vitro oocyte maturation modulated the phosphorylation status of Akt and ERK1/2 and enhanced the subsequent embryo production. In the absence of CB₁, in vivo oocyte maturation was impaired and embryo development delayed. Cannabinoid receptor 2 (CB₂) was unable to rescue these effects. Finally, we confirmed abnormal oocyte maturation rather than impaired embryonic transport through the oviduct in CB₁ knockouts. Our data suggest that cannabinoid agonists may be useful in vitro maturation supplements. For in vitro fertilization patients intolerant to gonadotropins, this could be a promising and only option.-López-Cardona, A. P., Pérez-Cerezales, S., Fernández-González, R., Laguna-Barraza, R., Pericuesta, E., Agirregoitia, N., Gutiérrez-Adán, A., Agirregoitia, E. CB₁ cannabinoid receptor drives oocyte maturation and embryo development via PI3K/Akt and MAPK pathways.

Impaired Spermatogenesis, Muscle, and Erythrocyte Function in U12 Intron Splicing-Defective Zrsr1 Mutant Mice

The U2AF35-like ZRSR1 has been implicated in the recognition of 3' splice site during spliceosome assembly, but ZRSR1 knockout mice do not show abnormal phenotypes. To analyze ZRSR1 function and its precise role in RNA splicing, we generated ZRSR1 mutant mice containing truncating mutations within its RNA-recognition motif. Homozygous mutant mice exhibited severe defects in erythrocytes, muscle stretch, and spermatogenesis, along with germ cell sloughing and apoptosis, ultimately leading to azoospermia and male sterility. Testis RNA sequencing (RNA-seq) analyses revealed increased intron retention of both U2- and U12-type introns, including U12-type intron events in genes with key functions in spermatogenesis and spermatid development. Affected U2 introns were commonly found flanking U12 introns, suggesting functional cross-talk between the two spliceosomes. The splicing and tissue defects observed in mutant mice attributed to ZRSR1 loss of function suggest a physiological role for this factor in U12 intron splicing.

Exocannabinoids effect on in vitro bovine oocyte maturation via activation of AKT and ERK1/2

Endocannabinoids are known to mediate practically all reproductive events in mammals; however, little is known about their role in oocyte maturation. Through RT-PCR and immunocytochemistry, this study confirms the presence of CB1 and CB2 cannabinoid receptors in bovine oocytes and shows how exposure to the exogenous cannabinoids HU-210 and THC during their in vitro maturation (IVM) activates the phosphorylation of AKT and ERK1/2 proteins associated with the resumption of meiosis. Although supplementation with HU-210 or THC during IVM did not increase blastocyst yields, the expression of interferon tau (IFNτ) and gap junction alpha-1 protein (GJA1) was enhanced at the blastocyst stage. Our data suggest that cannabinoid agonists may be useful IVM supplements as their presence during oocyte maturation upregulates the expression in blastocysts of key genes for embryo quality.

Potential Health Risks Associated to ICSI: Insights from Animal Models and Strategies for a Safe Procedure

Artificial reproductive techniques are currently responsible for 1.7–4% of the births in developed countries and intracytoplasmatic sperm injection (ICSI) is the most commonly used, accounting for 70–80% of the cycles performed. Despite being an invaluable tool for infertile couples, the technique bypasses several biological barriers that naturally select the gametes to achieve an optimal embryonic and fetal development. In this perspective, ICSI has been associated with an increased risk for diverse health problems, ranging from premature births and diverse metabolic disorders in the offspring to more severe complications such as abortions, congenital malformations, and imprinting disorders. In this review, we discuss the possible implications of the technique per se on these adverse outcomes and highlight the importance of several experiments using mammalian models to truthfully test these implications and to uncover the molecular base that origins these health problems. We also dissect the specific hazards associated to ICSI and describe some strategies that have been developed to mimic the gamete selection occurring in natural conception in order to improve the safety of the procedure.

Progesterone effects on mouse sperm kinetics in conditions of viscosity

The spermatozoa delivered to the female genital tract need to swim towards the oocyte through viscous secretions. Once close to the oocyte, the spermatozoa are guided by a gradient of progesterone (P4) and other unknown chemoattractants via a process known as chemotaxis. Using polyvinylpyrrolidone to establish the conditions of viscosity, we examined the response of mouse spermatozoa to P4. Herein, we show that in low-viscous media, P4 induces hyperactive-like motility whereby sperm show erratic trajectories and non-progressive movement. However, an opposite response is produced in viscous medium in that trajectories are linear and motility is more progressive and less erratic. Our observations provide a behavioural explanation for the chemotaxis of spermatozoa swimming under viscous conditions in a spatial gradient of the chemoattractant P4. They also highlight the importance of using viscous solutions to mimic in vivo conditions when analysing sperm behaviour in response to any stimulus.

Reproduction (2016) 151 501–507

Effect of chronic THC administration in the reproductive organs of male mice, spermatozoa and in vitro fertilization

The increased use of cannabis as a therapeutic drug in recent years has raised some concerns due to its potential effects on reproductive health. With regards to the male, the endocannabinoid system is involved in the spermatogenesis and in the sperm function. The chronic use of tetrahidrocannabinol (THC) has been associated with sperm anomalies, decreased sperm motility and structural changes in the testis. However, whether THC affects sperms ability to fertilize and to generate embryos remains unclear. The aim of this study was to evaluate this effect using a mice model of THC chronic treatment. For this purpose, a chronic treatment with THC was carried out. Mice were randomly allocated into two groups: an experimental group treated with a daily dose of 10 mg/kg-body weight THC for a period of 30 days and a control group treated with a vehicle. The THC-mice cortex showed a significant decrease of mRNA of Cnr1 compared to control-mice while, in the testis, the expression of Cnr1 was not affected. The weight of testis and epididymis and the histological analysis did not show any change between groups. On the other hand, no changes were observed in the sperm motility or the sperm concentration. The chronic use of THC did not generate any methylation change in the three CpG regions of Cnn1 analysed, neither in the brain nor in the embryos generated by in vitro fertilization (IVF). Finally, the embryo production by IVF was no different using spermatozoa from both THC and control mice. This work contradicts the belief that THC consumption has a negative effect on male reproductive processes.

Tetrahydrocannabinol Modulates in Vitro Maturation of Oocytes and Improves the Blastocyst Rates after in Vitro Fertilization

BACKGROUND/AIMS

Among the assisted reproductive techniques, the in vitro maturation of oocytes (IVM) is less developed than other techniques, but its implementation would entail a qualitative advance. This technique consists in the extraction of immature oocytes from antral ovarian follicles with the patient under low hormone stimulation or without hormone to mature exogenously in culture media supplemented with different molecules to promote maturation. In this sense, we are interested in the role that cannabinoids could have as IVM promoters because cannabinoid's molecular pathway is similar to the one by which oocyte's meiosis resumption is activated. With the intention of advancing in the possible use of cannabinoids as supplements for the media for in vitro maturation of oocytes, we intend to deepen the study of the function of the phytocannabinoid Δ-9-tetrahydrocannabinol (THC) in the IVM process.

METHODS

By immunocytochemistry, we detected the location pattern of cannabinoid receptor type 1 (CB1) and type 2 (CB2) during oocyte maturation in presence or absence of THC, as well as, the staining pattern of p-AKT and p-ERK. We used a genetic/ pharmacological approach generating knockout oocytes for CB1 and/or CB2 and they were incubated with THC during the oocyte maturation to visualize the physiological effects of THC, observing the rate of blastocyst achieved by oocyte.

RESULTS

This study confirms that the incubation of oocytes with THC during IVM accelerated some events of that process like the phosphorylation pattern of ERK and AKT and was able to increase the blastocyst rate in response to IVF. Moreover, it seems that both CB1 and CB2 are necessary to maintain a healthy oocyte maturation.

CONCLUSION

Our data suggest that THC may be useful IVM supplements in clinic as is more feasible and reliable than any synthetic cannabinoid.