Stress during the transition period shortens telomere length in dairy cows

Abstract

Extracellular vesicles (EVs) in the uterine fluid (UF) are known to regulate early embryo development. Moreover, the changes in UF-EV proteome during the bovine oestrous cycle and the effects of these proteins on embryo development are yet to be discovered. We used mass-spectrometry based shotgun quantitative proteomics to compare UF-EV proteomes at day 0, 7 and 16 of the oestrous cycle (n = 4 per group). Also, we supplemented follicular and luteal phase UF-EVs to group embryo cultures to evaluate their impact on embryo development. Proteomics data was analysed using LFQ-analyst platform , while the differences of blastocyst rates were evaluated with logistic regression analysis. Proteomic analysis revealed pathways which are important for early embryo development and its nutritional needs, such as antioxidant activity, cell morphology and cycle, cellular homeostasis, cell adhesion and carbohydrate metabolic process. Furthermore, 159 UF-EV proteins differentially enriched at different timepoints. These proteins were involved in pathways related to antioxidant activity, actin cytoskeleton organization, immune processes, gene expression regulation and metabolic functions. The luteal phase UF-EVs supplementation to the embryo culture media increased blastocyst rates from 25.0 ± 5.9% to 41.0 ± 4.0% (p = .03). Overall, our findings suggest that there are significant differences in bovine UF-EV proteome throughout the oestrous cycle and UF-EVs improve in vitro embryo production, however further studies are required to identify the exact UF-EV cargo for optimal embryo development. YSC 4 | Effect of equilibration temperature and time on feline ovarian tissue vitrification The entire members of Felidae are currently classified as endangered except for the domestic cat (Felis catus) making it an excellent model for conservation studies. Vitrification of feline ovarian tissue is an emerging conservation technique suitable in field conditions however, not yet standardized. Thus, the aim was to establish a suitable vitrification protocol for feline ovarian tissue in field conditions. Feline ovarian tissue fragments were punched with a biopsy punch (1.5 mm diameter) and divided into 4 groups. Group 1 was directly placed in culture (Fresh control-FC), while the other three were placed on 30G needles (4 fragments/needle) and vitrified using 3 protocols (A, B, C). Protocol A involved two step equilibrations for 10 min each at 4°C and then vitrification [1]. Protocol B involved three step equilibrations for 14 min in total at room temperature [2], while protocol C was the same with protocol B except the equilibra-tion timings which were reduced by half. Fragments were warmed and placed in culture [1] for 6 days. Follicular morphology, cellular proliferation (expression of Ki-67, MCM-7) and apoptosis (expression of caspase 3) were evaluated. Data were analysed using Chi square test. Proportions of morphological intact follicles were higher in FC (p = .0001) and protocol C (p = .0383) in comparison to the other protocols at the sixth day of culture. Generally, most follicles remained at primordial state which was confirmed by the low expression of ki-67, MCM-7 markers. In conclusion, protocol C, which has lower equilibration time at room temperature, can be used for vitrification of feline ovarian tissue. [1] Mouttham, Cryobiology 2016;73:187; [2] Amorim, Human Reproduction, 2013;28: 2146. YSC 5 | Stress during the transition period shortens telomere length in dairy cows Telomere length (TL) has long been recognized as a biomarker of ageing. In humans, physiological stress is known to impact health and longevity, manifested by an accelerated shortening of TL. In cattle, the transition period from pregnancy to lactation is considered a crucial stage, during which cows undergo significant metabolic and physiological changes. We hypothesize that telomeres shorten during this critical period, due to oxidative and metabolic stress. Seventy-one Holstein Friesian cows, on one farm, were followed up during the transition period and blood and milk samples were collected at regular time points. Average relative leukocyte TL was measured by a modified quantitative real-time PCR (qPCR) protocol at 7 days before and 21 days after parturition. Oxidative, inflammatory, and metabolic parameters were also determined. From 7 days prior to 21 days after parturition, a paired t-test showed a significant decrease in TL of 0.08 ± 0.243 (p = .022). Multiple linear models, built in R, were used to assess factors influencing TL shortening. Both oxidized glutathione in blood (GSSG, oxidative