Sperm-derived factors enhance the in vitro developmental potential of haploid parthenotes

Impacts of type 1 diabetes mellitus on male fertility and embryo quality in superovulated mice

OBJECTIVE

We aimed to compare embryo quality, sperm morphology, motility, and fertilization obtained from male mice with type 1 diabetes mellitus (T1DM) induced by streptozotocin (STZ) in control and diabetic mice undergoing in vitro fertilization (IVF).

METHODS

CD-1 male mice were divided into control and DM groups, with an i.p. injection of 100 mg/kg STZ to induce T1DM. One month later, the mice were euthanized to investigate the effects of STZ-induced T1DM on the reproductive system. Sperms were obtained from the epididymis and vas deferens. The morphology and motility of the cells were evaluated. Follicle development was stimulated by controlled ovarian stimulation, and oocytes were collected by extracting oviducts and ovaries from female mice housed under controlled environmental conditions with ad libitum access. Both groups underwent IVF with fertilized zygotes followed up until the third day before embryo quality was compared.

RESULTS

Female mice bred with diabetic males exhibited significantly lower fertilization rates than the controls (p < 0.05). Sperm from diabetic mice displayed abnormalities in shape and movement, with reduced motility and fertilization. Embryos from male diabetic mice exhibited a higher incidence of developmental arrest during early embryogenesis. Although no significant differences in oocyte quality were observed, embryos from diabetic mice exhibited higher growth rates. These findings highlighted the T1DM's detrimental effects on sperm morphology, motility, fertilization, and early embryonic development, thus contributing to our understanding of reproductive complications.

CONCLUSION

In conclusion, our findings demonstrated that T1DM significantly impaired sperm morphology, motility, and fertilization capacity, leading to reduced embryo quality and increased developmental arrest. These results highlight the detrimental impact of DM on male reproductive potential and underscore the importance of glycemic control in optimizing outcomes in assisted reproductive techniques such as IVF.

Bromodomain and extraterminal protein inhibitor JQ1 induces maturation arrest and disrupts the cytoplasmic organization in mouse oocytes under in vitro conditions

JQ1, a small cell-permeable molecule is known for its potent inhibitory action on bromodomain and extraterminal (BET) proteins. Although earlier studies have shown its inhibitory effect on male gametogenesis, limited information is available about its influence on oocyte development. Since BET genes are known to exhibit regulatory functions on oocyte development and maturation, the present study aimed to investigate the effect of JQ1 on oocyte developmental competence under in vitro conditions. Germinal vesicle (GV) stage oocytes were collected from adult Swiss albino mice and subjected to in vitro maturation (IVM) in the presence of various concentrations of JQ1 (25, 50, and 100 μM). The metaphase II (MII) stage oocytes were assessed for cytoplasmic organization and functional competence at 24 h after IVM. A significant decrease in nuclear maturation (at 50 and 100 μM), symmetric cytokinesis, altered distribution of mitochondria and cortical granules, poorly organized actin and meiotic spindle, misaligned chromosomes, and elevated endoplasmic reticulum (ER) stress and oxidative stress was observed in JQ1-exposed oocytes. Presence of N-acetyl cysteine (NAC), in IVM medium resulted in significant reduction in JQ1-induced oxidative stress and symmetric cytokinesis. Administration of JQ1 (50 mg/kg, intra peritoneal) to adult Swiss albino mice primed with pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG) did not affect the ovulation. However, a high degree of oocyte degeneration, elevated intracellular reactive oxygen species (ROS), and GRP78 expression was observed in JQ1-administered mice. In conclusion, our study reveals that BET inhibitor JQ1 has detrimental effects on oocyte function and development.

Haploid Parthenogenetic Embryos Exhibit Unique Stress Response to pH, Osmotic and Oxidative Stress

Preimplantation-stage embryos are susceptible to various types of stress when cultured in vitro. Parthenogenetic embryos that lack spermatozoa contribution exhibit aberrant developmental dynamics due to their uniparental origin. Herein, we assessed whether the absence of paternal genome affects the susceptibility of the embryos to pH, osmotic and oxidative stress. Haploid parthenogenetic embryos (HPE) (activated oocytes with 1 pronucleus and 2 polar bodies) were generated by incubating cumulus oocyte complexes of Swiss albino mice with 10 mM strontium chloride for 3 h. Normally fertilized embryos (NFE) (fertilized oocytes with 2 pronuclei and 2 polar bodies) were derived using in vitro fertilization. At 2-cell stage, both HPE and NFE were exposed to various stressors including pH (6.8 to 8.2), osmotic (isotonic, hypotonic, and hypertonic), and peroxidatic oxidative (H2O2, 25 µM) stress. Endoplasmic reticulum stress response, mitochondrial membrane potential, and the rate of blastocyst development were assessed. HPE were susceptible to alteration in the pH that was well tolerated by NFE. Similarly, HPE displayed remarkable difference in sensitivity to hypertonic stress and oxidative stress compared to NFE. The results clearly indicate that the oocytes that develop into embryos in the absence of paternal contribution are more vulnerable to environmental stressors, further highlighting the importance of spermatozoa contribution and/or the ploidy status in mitigating these stressors and towards healthy early embryo development.

Bovine ICSI: limiting factors, strategies to improve its efficiency and alternative approaches

Intracytoplasmic sperm injection (ICSI) is an assisted reproductive technique mainly used to overcome severe infertility problems associated with the male factor, but in cattle its efficiency is far from optimal. Artificial activation treatments combining ionomycin (Io) with 6-dimethylaminopurine after piezo-ICSI or anisomycin after conventional ICSI have recently increased the blastocyst rate obtained. Compounds to capacitate bovine spermatozoa, such as heparin and methyl-β-cyclodextrin and compounds to destabilize sperm membranes such as NaOH, lysolecithin and Triton X-100, have been assessed, although they have failed to substantially improve post-ICSI embryonic development. Disulfide bond reducing agents, such as dithiothreitol (DTT), dithiobutylamine and reduced glutathione, have been assessed to decondense the hypercondensed head of bovine spermatozoa, the two latter being more efficient than DTT and less harmful. Although piezo-directed ICSI without external activation has generated high fertilization rates and modest rates of early embryo development, other studies have required exogenous activation to improve the results. This manuscript thoroughly reviews the different strategies used in bovine ICSI to improve its efficiency and proposes some alternative approaches, such as the use of extracellular vesicles (EVs) as 'biological methods of oocyte activation' or the incorporation of EVs in the in vitro maturation and/or culture medium as antioxidant defence agents to improve the competence of the ooplasm, as well as a preincubation of the spermatozoa in estrous oviductal fluid to induce physiological capacitation and acrosome reaction before ICSI, and the use of hyaluronate in the sperm immobilization medium.

Calcium Ionophore (A23187) Rescues the Activation of Unfertilized Oocytes After Intracytoplasmic Sperm Injection and Chromosome Analysis of Blastocyst After Activation

Calcium is a crucial factor in regulating the biological behavior of cells. The imbalance of calcium homeostasis in cytoplasm will cause abnormal behavior of cells and the occurrence of diseases. In intracytoplasmic sperm injection (ICSI) cycle, the dysfunction of oocyte activation caused by insufficient release of Ca²⁺ from endoplasmic reticulum is one of the main reasons for repeated fertilization failure. Calcium ionophore (A23187) is a highly selective calcium ionophore, which can form stable complex with Ca²⁺ and pass through the cell membrane at will, effectively increasing intracellular Ca²⁺ levels. It has been reported that calcium ionophore (A23187) can activate oocytes and obtain normal embryos. However, there are few studies on unfertilized oocytes after calcium ionophore (A23187) rescue activation in ICSI cycle. The purpose of this study was to analyze the effects of calcium ionophore (A23187) rescue activation on the activation of unfertilized oocytes, embryonic development potential, embryonic development timing and chromosomal aneuploidy, and to compare and analyze the clinical data of patients with calcium ionophore (A23187) activation in clinical application. The results showed that a certain proportion of high-quality blastocysts with normal karyotype could be obtained after calcium ionophore (A23187) rescue activation of unfertilized oocytes, and it did not have a significant effect on the timing of embryo development. In clinical practice, direct activation with calcium ionophore (A23187) after ICSI was better than rescue activation the next day. In conclusions, the studies on the effectiveness and safety of calcium ionophore (A23187) rescue activation for oocytes with ICSI fertilization failure can enable some patients to obtain usable, high-quality embryos during the first ICSI cycle.

Effect of single and combined treatments with MPF or MAPK inhibitors on parthenogenetic haploid activation of bovine oocytes

In bovine, correct oocyte artificial activation is a key step in ICSI and other reproductive biotechnologies, and still needs to be improved. The current study was designed to compare the activating efficiency of ionomycin (Io) followed by: a 4 h time window and ethanol (4h-Et), roscovitine (Rosc), dehydroleucodine (DhL), cycloheximide (CHX) or PD0325901 (PD), each as a single treatment, and then combine them in novel protocols. Parthenogenetic haploid activation was evaluated in terms of pronuclear (PN) formation, second polar body (2PB) extrusion, ploidy of day 2 embryos and in vitro development. Combined treatments with Io-4h-Et-Rosc and Io-Rosc/CHX increased PN formation (92.2% and 96%, respectively) compared with Io-Rosc, Io-CHX or Io-4h-Et, which were equally efficient at inducing PN formation (82-84%) and 2PB extrusion (62.1-70.5%). Oocyte activation with Io-DhL and Io-Rosc/DhL resulted in higher 2PB extrusion rates (90% and 95.9%, respectively) but lower PN formation (49.4-58.8%) and cleavage rates (36-57.9%), as occurred with Io-CHX/DhL (76.4% and 70.4%, respectively). For the first time, results show that Io followed by the MAPK inhibitor PD induces PN formation and 2PB extrusion, but PD combined with Rosc or CHX resulted in low rates of haploid day 2 embryos. In conclusion, DhL strongly induces 2PB extrusion but leads to poor PN formation and embryo development. PD induces bovine oocyte activation but results in low rates of haploid embryos. In contrast, the improved PN formation rates after treatment with combined Io-4h-Et-Rosc and Io-Rosc/CHX suggest they should be further evaluated in ART, aiming to increase success rates in bovine.