Low oxygen concentration improves yak oocyte maturation and inhibits apoptosis through HIF-1 and VEGF

Transcriptomic Profiling of Hypoxia-Adaptive Responses in Tibetan Goat Fibroblasts

The Tibetan goat (Capra hircus) exhibits remarkable adaptations to high-altitude hypoxia, yet the molecular mechanisms remain unclear. This study integrates RNA-seq, WGCNA, and machine learning to explore gene-environment interactions (G × E) in hypoxia adaptation. Fibroblasts from the Tibetan goat and Yunling goat were cultured under hypoxic (1% O2) and normoxic (21% O2) conditions, respectively. This identified 68 breed-specific (G), 100 oxygen-responsive (E), and 620 interaction-driven (I) Differentially Expressed Genes (DEGs). The notably higher number of interaction-driven DEGs compared to other effects highlights transcriptional plasticity. We defined two gene sets: Environmental Stress Genes (n = 632, E ∪ I) and Genetic Adaptation Genes (n = 659, G ∪ I). The former were significantly enriched in pathways related to oxidative stress defense and metabolic adaptation, while the latter showed prominent enrichment in pathways associated with vascular remodeling and transcriptional regulation. CTNNB1 emerged as a key regulatory factor in both gene sets, interacting with CASP3 and MMP2 to form the core of the protein-protein interaction (PPI) network. Machine learning identified MAP3K5, TGFBR2, RSPO1 and ITGB5 as critical genes. WGCNA identified key modules in hypoxia adaptation, where FOXO3, HEXIM1, and PPARD promote the stabilization of HIF-1α and metabolic adaptation through the HIF-1 signaling pathway and glycolysis. These findings underscore the pivotal role of gene-environment interactions in hypoxic adaptation, offering novel perspectives for both livestock breeding programs and biomedical research initiatives.

The glucose metabolism reprogramming of yak Sertoli cells under hypoxia is regulated by autophagy

Hypoxia often has negative effects on testis development and spermatogenesis of mammals. Plateau yaks have lived in the hypoxia environment for generations, but have ensured testicular function, which is closely related to their unique hypoxia response mechanism. Glucose metabolic reprogramming is an important way for cells to respond to stressful environments, especially the metabolite lactate, which is the energy basis for the development and differentiation of germ cells. In this study, hypoxia (5% O2) effectively promoted yak Sertoli cell proliferation and decreased autophagy and apoptosis. It was found that the cells showed good hypoxic adaptation. Metabolomics results showed that glucose metabolism was enhanced in yak Sertoli cells in response to hypoxia, and 13 glucose metabolites were increased, including the production and transport level of lactic acid (LA), which may have changed the pentose phosphate metabolic pathway of cells, these changes are conducive to support the glucose metabolism balance of cells under hypoxia. Crucially, when autophagy is activated under hypoxia, GLUT3, GLUT8, and MCT4 proteins are degraded, while GLUT1 and MCT1 are not affected, suggesting that autophagy may achieve glucose metabolic reprogramming by selectively regulating the expression of functional factors of glucose metabolism, which is conducive to energy intake and spermatogenesis in testis of yaks.

Rapamycin Increases the Development Competence of Yak (Bos grunniens) Oocytes by Promoting Autophagy via Upregulating 17β-Estradiol and HIF-1α During In Vitro Maturation

High-quality oocyte production strategies play an important role in animal-assisted reproductive biotechnologies, and rapamycin (Rap) has been commonly used to increase the development potential of mammalian oocytes. The purpose of this study is to evaluate the effects and possible molecular mechanisms of rap on the maturation of yak oocytes. Different concentrations of Rap were supplemented during in vitro maturation (IVM) of yak oocytes. The maturation rates of oocytes and development rates of parthenogenetically activated embryos were assessed. The levels of 17β-estradiol (E2) were detected via ELISA, and the expression of autophagy-related factors, steroidogenic enzymes, and HIF-1α was detected via qRT-PCR, western blotting, and fluorescence microscopy, respectively. In addition, the impacts of E2 and HIF-1α on Rap-mediated oocyte autophagy were investigated by investigating the activities of E2 and HIF-1α. Our results showed that 0.1 nM Rap substantially enhanced the developmental ability of yak oocytes. In this group, the levels of E2, CYP19A1, CYP17A1, and autophagy-related factors were also significantly increased, and the expression of ATG5 and BECN1 in subsequent embryos was also increased. Further analysis revealed that Rap tends to enhance the development competence of yak oocytes and that the levels of autophagy-related factors are reduced when the activity of E2 or HIF-1α is inhibited. Furthermore, the levels of E2, CYP19A1, and CYP17A1 were downregulated when the activity of HIF-1α was inhibited, and the levels of HIF-1α were also significantly reduced by the estrogen receptor antagonist G15. Nevertheless, the levels of CYP11A1 mRNA in mature yak COCs were not significantly different among these groups, a phenomenon which implies that the levels of E2 were not correlated with the CYP11A1 content in yak COCs. There was an increasing tendency for the development competence of yak oocytes at the optimum concentration of Rap during IVM. The potential underlying mechanism is that Rap can activate autophagy and upregulate the levels of E2 and HIF-1α in mature oocytes. Additionally, the levels of both E2 and HIF-1α are regulated by each other and involve Rap-regulated autophagy in oocytes.

Lactate Promotes Hypoxic Granulosa Cells' Autophagy by Activating the HIF-1α/BNIP3/Beclin-1 Signaling Axis

BACKGROUND/OBJECTIVES

The avascular nature of the follicle creates a hypoxic microenvironment, establishing a niche where granulosa cells (GCs) rely on glycolysis to produce energy in the form of lactate (L-lactate). Autophagy, an evolutionarily conserved stress-response process, involves the formation of autophagosomes to encapsulate intracellular components, delivering them to lysosomes for degradation. This process plays a critical role in maintaining optimal follicular development. However, whether hypoxia regulates autophagy in GCs via lactate remains unclear.

METHODS

In this study, we investigated lactate-induced autophagy under hypoxia by utilizing glycolysis inhibitors or silencing related genes.

RESULTS

We observed a significant increase in autophagy in ovarian GCs under hypoxic conditions, indicated by elevated LC3II levels and reduced P62 levels. Suppressing lactate production through glycolytic inhibitors (2-DG and oxamate) or silencing lactate dehydrogenase (LDHA/LDHB) effectively reduced hypoxia-induced autophagy. Further investigation revealed that the HIF1-α/BNIP3/Beclin-1 axis is essential for lactate-induced autophagy under hypoxic conditions. Inhibiting HIF-1α activity using siRNAs or PX-478 downregulated BNIP3 expression and subsequently suppressed autophagy. Similarly, BNIP3 silencing with siRNAs repressed lactate-induced autophagy in hypoxic conditions. Mechanistically, immunoprecipitation experiments showed that BNIP3 disrupted pre-existing Bcl-2/Beclin-1 complexes by competing with Bcl-2 to form Bcl-2/BNIP3 complexes. This interaction released Beclin-1, which subsequently triggered lactate-induced autophagy under hypoxic conditions.

CONCLUSIONS

These findings unveil a novel mechanism by which hypoxia regulates GC autophagy through lactate production, highlighting its potential role in sustaining follicular development under hypoxic conditions.

Molecular Markers in Embryo Non-Development: Analysis of Gene Expressions (Ki-67, hTERT, HIF-1α) in Spent Embryo Culture Medium

An embryo culture medium is a specialized set of ambient conditions, technological equipment, and nutrients that embryos require to grow properly. We aimed to investigate the Ki-67, hTERT, and HIF-1α gene expression differences between developing and non-developing embryos in spent embryo culture medium. Ki-67, hTERT, and HIF-1α gene expressions were determined from the spent embryo culture medium containing developing and non-developing embryos of 20 normoresponder patients admitted to the Bahçeci Umut IVF Center. An increase in hTERT gene expression (p < 0.05) and a decrease in HIF-1α gene expression (p < 0.001) were observed in mediums of developing compared to the non-developing embryos. No difference was observed in Ki-67 gene expression (p > 0.05). While there was a correlation between Ki-67 and HIF-1α genes in the non-growing group (r < 0.01); no correlation was observed in the developing group (r > 0.05). Both normoresponder groups will be similar in terms of proliferation rate. The low HIF-1α expression that observed high telomerase activity in embryo development maintains continuity and avoids mechanisms that result in cell death. A molecular study of the embryo development in patients with similar characteristics may help to understand the pathogenesis of the disease and establish a diagnosis and specific treatment.

In vitro production of viable eggs from undeveloped oocytes in mouse preantral follicles by reconstructing granulosa cell-oocyte complexes†

In vitro culture of ungrown oocytes in preantral follicles is one of the intriguing subjects being pursued to produce viable eggs in assisted reproductive technology. Previous studies have succeeded in obtaining mature eggs after in vitro culture of preantral follicles, while denuded undeveloped oocytes, which are obtained occasionally when collecting preantral follicles, seem to be almost useless. Moreover, methods to culture them efficiently to produce viable eggs have not been established yet. The present study was conducted to demonstrate in vitro culture of mouse denuded undeveloped oocytes by reconstructing granulosa cell-oocyte complexes, and to analyze cellular communication in reconstructed granulosa cell-oocyte complexes. Single denuded undeveloped oocytes were aggregated with 1 × 104 granulosa cells in wells with U-shaped bottoms in a low-binding cell culture plate for 8 days under either 20% or 5% O2, and then the reconstructed granulosa cell-oocyte complexes formed were cultured on a collagen-coated culture membrane insert for 4 days under 5% O2. At day 8 of culture, the rates of reconstructed granulosa cell-oocyte complexes formation were significantly higher in the culture group under 5% O2 (64.9%) than that under 20% O2 (42.3%; P < 0.001); furthermore, the formation of transzonal projections was observed. After maturation and fertilization, we produced matured eggs and blastocysts at higher rates (>90% and 61.9%, respectively) in the group cultured under 5% O2. After transferring 126 two- to four-cell stage embryos, six live pups were obtained. This is the first report that demonstrates production of viable eggs after in vitro culture of denuded undeveloped oocytes from preantral follicles by reconstruction of granulosa cell-oocyte complexes.

Temperature-sensitive nanogels combined with polyphosphate and cisplatin for the enhancement of tumor artery embolization by coagulation activation

Transcatheter arterial chemoembolization (TACE) is the first-line therapy for hepatocellular carcinoma (HCC). However, the exacerbated hypoxia microenvironment induces tumor relapse and metastasis post-TACE. Here, temperature-sensitive block polymer complexed with polyphosphate-cisplatin (Pt-P@PND) was prepared for the enhancement of tumor artery embolization by coagulation activation. After supra-selective infusion into the tumor vessels, Pt-P@PND nanogels performed efficient embolization of tumor arteries by sol-gel transition at body temperature. Meanwhile, coagulation cascade was evoked to form blood clots in the peripheral arteries inaccessible to the nanogels by released PolyP. The blood clots-filled hydrogel networks composed of gel and clots showed a denser structure and higher modulus, thereby achieving long-term embolization of all levels of tumor arteries. Pt-P@PND nanogels efficiently inhibited tumor growth and reduced the expression of HIF-1α, VEGF, CD31, and MMP-9 on VX2 tumor-bearing rabbit model. The released Nitro-Pt stimulated the immunogenic cell death of tumor cells, thus enhancing the antitumor immune response to suppress tumor relapse and metastasis post-TACE. It is hoped that Pt-P@PND nanogels can be developed as a promising embolic agent with procoagulant activity for enhancing the antitumor immune response through a combination of embolism, coagulation, and chemotherapy. STATEMENT OF SIGNIFICANCE: Clinical embolic agents, such as Lipiodol and polyvinyl alcohol (PVA) microspheres, are limited by their rapid elimination or larger size, thus lead to incomplete embolization of trans-catheter arterial chemoembolization (TACE). Herein, temperature-sensitive Pt-P@PND nanogels were developed to achieve long-term embolization of all levels of tumor arteries by gel/clot generation. The released Nitro-Pt induced immunogenic cell death in tumor cells, which improved the antitumor immune microenvironment by the maturation of DCs and lymphocytic infiltration. Pt-P@PND nanogels successfully inhibited tumor growth and activated an antitumor immune response to curb the recurrence and metastasis of residual tumor cells both in VX2 tumor-bearing rabbit model and 4T1 tumor-bearing mouse model. These findings suggested that Pt-P@PND could be developed as an ideal embolic agent for clinical TACE treatment.

Hypoxia-Inducible Factor 1α Affects Yak Oocyte Maturation and Early Embryonic Development by Regulating Autophagy

In animal assisted reproductive technology, the production of high-quality oocytes is crucial. The yak, having lived in the Qinghai-Tibet Plateau for an extended period, has reproductive cells that are regulated by hypoxia-inducible factor 1α (HIF-1α). This study aimed to investigate the impact of HIF-1α on yak oocyte maturation and early embryonic development in vitro through the regulation of autophagy. The in vitro maturation process of yak oocytes involved the addition of the HIF-1α inducer DFOM and the inhibitor LW6 to examine their effects on yak oocyte maturation, early embryonic development, cell autophagy, cytochrome P450s (CYP450s) enzyme expression, and cumulus diffusion factors. The findings revealed that DFOM significantly upregulated the expression of HIF-1α, resulting in increased the cumulus diffusion area, elevated first polar body expulsion rate of oocytes, enhanced mitochondrial and actin levels, decreased ROS production, and reduced early apoptosis levels of oocytes. Moreover, DFOM promoted the expression of autophagy-related proteins, CYP450s enzymes, and cumulus diffusion factors, thereby enhancing oocyte maturation and early embryonic development. Conversely, LW6 exhibited opposite effects. The inhibition of autophagy levels with 3-MA during DFOM treatment yielded similar outcomes. Furthermore, reducing autophagy led to increased apoptosis levels at all stages of early embryonic development, as well as a significant decrease in total cell number and ICM/TE ratio of blastocysts. Studies have shown that during the in vitro maturation of yak oocytes, HIF-1α can affect the cumulus expansion area of oocytes by regulating autophagy, the first polar body excretion rate, mitochondrial level, actin level, ROS and early apoptosis level, the CYP450s enzyme, and the expression of cumulus expansion factors, thereby improving the in vitro maturation and early embryonic development of yak oocytes. These findings offer valuable insights into the reproductive regulation mechanism of yaks in hypoxic environments and suggest potential strategies for the advancement of yak assisted reproductive technology.

Expression and correlation of the Pi3k/Akt pathway and VEGF in oral submucous fibrosis

Oral submucous fibrosis (OSF) has a high incidence in Asia countries, but its underlying molecular mechanism was not exploited completely. In this research, we investigated the expression of the phosphatidyl inositol 3-kinase (Pi3k)/protein kinase B (Akt) pathway and vascular endothelial growth factor (VEGF) in oral submucosal fibrosis, explore the correlation between the Pi3k/Akt pathway and VEGF, and identify the mechanisms involved in OSF. The pathological changes and fibrosis stages of OSF tissues (n = 30, 10 each of early, moderate and advanced OSF) were determined using Haematoxylin-eosin staining (HE) and Masson staining, respectively. Collagen type I (Col-I), Pi3k, Akt, VEGF, TGF-β and p-Akt expression was detected using immunohistochemistry, qPCR and WB. The correlation between Pi3k, Akt and VEGF was analysed. Col-I expression increased as OSF progressed. However, their expression was downregulated in normal and moderate to advanced OSF tissues. VEGF expression positively correlated with Pi3k and Akt expression. VEGF expression correlated positively and negatively with the Pi3k inhibitor, LY294002 below and above a concentration of 10 μM, respectively. VEGF expression correlated positively with the Pi3k/Ak activator, IGF-1. Due to the synergistic effect between Pi3k/Akt pathway and VEGF on OSF lesions and fibrosis process, targeted Pi3k/Akt pathway regulation can induce VEGF expression and improve ischemia, ultimately treating OSF.

Factors Influencing the Maturation and Developmental Competence of Yak (Bos grunniens) Oocytes In Vitro

The yak (Bos grunniens) is a unique breed living on the Qinghai-Tibet Plateau and its surrounding areas, providing locals with a variety of vital means of living and production. However, the yak has poor sexual maturity and low fertility. High-quality mature oocytes are the basis of animal breeding technology. Recently, in vitro culturing of oocytes and embryo engineering technology have been applied to yak breeding. However, compared to those observed in vivo, the maturation rate and developmental capacity of in vitro oocytes are still low, which severely limits the application of in vitro fertilization and embryo production in yaks. This review summarizes the endogenous and exogenous factors affecting the in vitro maturation (IVM) and developmental ability of yak oocytes reported in recent years and provides a theoretical basis for obtaining high-quality oocytes for in vitro fertilization and embryo production in yaks.

Expression and Clinical Significance of HIF-1α in Follicular Fluid and Granulosa Cells in Infertile PCOS Patients

The present study aimed to determine the clinical predictive significance of HIF-1α in follicular development and assisted reproductive technology (ART). We collected follicular fluid (FF) and granulosa cells (GCs) from PCOS (polycystic ovary syndrome) patients (experimental group) and other patients who were infertile due to tubal factors or male factors (control group) with IVF/ICSI-ET. The localization and expression of HIF-1α in GCs were determined by immunofluorescence staining. HIF-1α protein and mRNA expression were detected by enzyme-linked immunosorbent assay and quantitative real-time PCR, respectively. To clarify the regulation of HIF-1α by TGF-β1, we added the HIF-1α-specific blocker YC-1 to GCs. The serum AMH, LH, LH/FSH, testosterone, BMI and the number of oocytes retrieved in the PCOS group were significantly higher, while the cleavage rate was significantly lower, than those in the control group. HIF-1α protein was expressed in the cytoplasm of GCs. The expression of HIF-1α protein in the FF of the PCOS group was significantly lower than that in the control group. However, the expression of HIF-1α protein in GCs between the two groups was not significantly different. HIF-1α protein was highly expressed in large FF (follicular diameter ≥ 14 mm). Compared with the control group, the expression of HIF-1α mRNA in GCs of the PCOS group was significantly lower. The results showed a significant positive correlation between HIF-1α and TGF-β1 expression. We found that both HIF-1α and TGF-β1 were involved in the development of PCOS follicular development. The mutual regulation of HIF-1α and TGF-β1 may be one of the important mechanisms of the occurrence and development of PCOS.

Effects of vascular endothelial growth factor (VEGF) on the viability, apoptosis and steroidogenesis of yak (Bos grunniens) granulosa cells

Vascular endothelial growth factor (VEGF) is crucial for follicle development through the regulation of granulosa cell (GC) function in some mammals, but its mechanism is unclear in yak (Bos grunniens). Therefore, the objectives of this study were to investigate the effects of VEGF on the viability, apoptosis and steroidogenesis of yak GCs. First, we investigated the localization of VEGF and its receptor (VEGFR2) in yak ovaries by immunohistochemistry analysis and evaluated the effect of culture medium containing different VEGF concentrations and culture times on the viability of yak GCs by Cell Counting Kit-8. Then, optimal treatment with 20 ng/mL VEGF for 24 h was selected to analyze the effects of this compound on intracellular reactive oxygen species levels by DCFH-DA kit, cell cycle and apoptosis by flow cytometry, steroidogenesis by ELISA kit and the expression of the related genes by RT‒qPCR. The results showed that VEGF and VEGFR2 were highly coexpressed in GCs and theca cells. GCs cultured in medium containing 20 ng/mL VEGF for 24 h significantly improved cell viability, decreased ROS production, promoted the transition from G1 phase to S phase (P < 0.05), increased the expression of the CCND1 (P < 0.05), CCNE1, CDK2, CDK4, and PCNA genes (P < 0.01) and decreased the expression of the P53 gene (P < 0.05). This treatment significantly reduced GC apoptosis (P < 0.05) by promoting the expression of BCL2 and GDF9 (P < 0.01) and inhibiting the expression of BAX and CASPASE3 (P < 0.05). VEGF promoted progesterone secretion (P < 0.05) accompanied by increased expression of HSD3B, StAR and CYP11A1 (P < 0.05). Taken together, our findings highlight the beneficial influence exerted by VEGF in improving GC viability and reducing ROS production and the apoptosis rate through the modulation of related gene expression.