The effects of repeated freezing and thawing on bovine sperm morphometry and function.

Refreezing the remaining genetic resources after in vitro fertilization (IVF) can conserve genetic materials. However, the precise damage inflicted by repeated freezing and thawing on bovine sperm and its underlying mechanism remain largely unexplored. Thus, this study investigates the impact of repeated freeze-thaw cycles on sperm. Our findings indicate that such cycles significantly reduce sperm viability and motility. Furthermore, the integrity of the sperm plasma membrane and acrosome is compromised during this process, exacerbating the advanced apoptosis triggered by oxidative stress. Additionally, transmission electron microscopy exposed severe damage to the plasma membranes of both the sperm head and tail. Notably, the "9 + 2" structure of the tail was disrupted, along with a significant decrease in the level of the axonemal protein DNAH10, leading to reduced sperm motility. IVF outcomes revealed that repeated freeze-thaw cycles considerably impair sperm fertilization capability, ultimately reducing the blastocyst rate. In summary, our research demonstrates that repeated freeze-thaw cycles lead to a decline in sperm viability and motility, attributed to oxidative stress-induced apoptosis and DNAH10-related dynamic deficiency. As a result, the utility of semen is compromised after repeated freezing.

Comparison of microbiota structure in reproductive tract of Yanbian cattle and Yanhuang cattle.

Microbiota in the reproductive tract of cattle play a vital role in maintaining normal reproduction. However, the information on microbiota in different parts of reproductive tracts with different genetic background is few. The aim of the present study was to describe and compare the microbiota in vagina, cervix and uterus of Yanbian cattle and Yanhuang cattle. The results showed that microbial diversity increases from the vagina to the uterus. The top three bacterial phyla in bovine reproductive tract were Proteobacteria, Firmicutes and Bacteroidetes, accounting for more than 85%. From the vagina to the uterus, the relative abundance of Proteobacteria gradually decreased, while that of Firmicutes gradually increased. Phylum-level Firmicutes and genus-level UCG_010 were significantly enriched in the uterus of Yanbian cattle and Yanhuang cattle. Comparing the same parts of the two breeds, it was found that there was no significant difference in alpha diversity, but significant differences in beta diversity. In addition, microbiota with significant differences in the relative abundance of the reproductive tract were found. These findings lay a foundation for a comprehensive understanding of the structure of the genital tract microbiota of cows and its regulatory mechanisms.

Protective effects of engineered Lactobacillus johnsonii expressing bovine granulocyte-macrophage colony-stimulating factor on bovine postpartum endometritis.

Introduction: Postpartum endometritis is a prevalent reproductive disorder in bovines, leading to a prolonged open period, infertility, and other complications. While Lactobacillus strains can mitigate these conditions by reducing uterine inflammation, their effectiveness is limited due to a lack of direct anti microbial action and extended treatment duration. This study aimed to construct a recombinant Lactobacillus johnsonii strain expressing bovine Granulocyte-macrophage colony-stimulating factor (GM-CSF) to evaluate its potential in reducing postpartum uterine inflammation. Methods: The recombinant Lactobacillus johnsonii strain was engineered to express bovine GM-CSF and administered to pregnant mice via vaginal perfusion. Postpartum endometritis was induced using E. coli infection, and the protective effects of the engineered strain were assessed. Inflammatory markers (IL-6, IL-1ß, TNF-α), myeloperoxidase (MPO) activity, and nitric oxide (NO) concentration were measured. Histological examination was performed to evaluate uterine morphology and pathological damage. Results: The recombinant L. johnsonii strain expressing GM-CSF significantly reduced inflammation levels induced by E. coli infection in the uterus. This reduction was evidenced by decreased expression of IL-6, IL-1ß, TNF-α, as well as reduced MPO activity and NO concentration. Histological examination revealed improved uterine morphology and reduced pathological damage in mice treated with the recombinant GM-CSF strain. Crucially, the recombinant strain also exerts beneficial effects on bovine endometritis by reducing levels of inflammatory cytokines, suggesting a beneficial effect on clinical bovine endometritis. Conclusion: The recombinant Lactobacillus johnsonii expressing GM-CSF demonstrated protective effects against postpartum endometritis in bovines by reducing inflammatory cytokines. The findings indicate the potential clinical application of this engineered strain in preventing postpartum uterine inflammation, offering a novel and effective protective option for related disorders and improving bovine reproductive efficiency.

Recent selection and introgression facilitated high-altitude adaptation in cattle.

During the past 3000 years, cattle on the Qinghai-Xizang Plateau have developed adaptive phenotypes under the selective pressure of hypoxia, ultraviolet (UV) radiation, and extreme cold. The genetic mechanism underlying this rapid adaptation is not yet well understood. Here, we present whole-genome resequencing data for 258 cattle from 32 cattle breeds/populations, including 89 Tibetan cattle representing eight populations distributed at altitudes ranging from 3400 m to 4300 m. Our genomic analysis revealed that Tibetan cattle exhibited a continuous phylogeographic cline from the East Asian taurine to the South Asian indicine ancestries. We found that recently selected genes in Tibetan cattle were related to body size (HMGA2 and NCAPG) and energy expenditure (DUOXA2). We identified signals of sympatric introgression from yak into Tibetan cattle at different altitudes, covering 0.64%-3.26% of their genomes, which included introgressed genes responsible for hypoxia response (EGLN1), cold adaptation (LRP11), DNA damage repair (LATS1), and UV radiation resistance (GNPAT). We observed that introgressed yak alleles were associated with noncoding variants, including those in present EGLN1. In Tibetan cattle, three yak introgressed SNPs in the EGLN1 promoter region reduced the expression of EGLN1, suggesting that these genomic variants enhance hypoxia tolerance. Taken together, our results indicated complex adaptation processes in Tibetan cattle, where recently selected genes and introgressed yak alleles jointly facilitated rapid adaptation to high-altitude environments.