Evaluation of Reproductive Tract Cytokines in Post-partum Beef Cows Relating to Reproductive Microbiota and Fertility Outcomes

Abstract

The activity of the immune system in the reproductive tract has been proven to be crucial in the response to uterine diseases, normal reproductive functions, and tolerance to the allogeneic fetus during pregnancy. The objectives of the current study were to (1) evaluate uterine and vaginal cytokine concentrations in postpartum cows undergoing estrus synchronization followed by timed artificial insemination (TAI) and (2) correlate bacterial communities with cytokine concentrations. Postpartum Angus cows (n = 20) were subjected to a 7-Day Co-Synch protocol with pre-synchronization beginning 21 days prior (d −21) to TAI (d 0). Uterine and vaginal flushes were collected on d −21 and −2. Pregnancy was determined by transrectal ultrasound on d 30. Cytokines include interleukin (IL)-1b, IL-6, IL-10, transforming growth factor beta (TGF-β), and immunoglobin A (IgA) and concentrations were determined by commercial ELISA kits. No differences by day or pregnancy status in cytokine concentrations were detected in vaginal samples. No differences by day or pregnancy status in IgA, IL-10, or IL-1b concentrations were detected in uterine samples. Overall TGF-β concentrations in the uterus were greater in resulting pregnant than non-pregnant cows (44.0 ± 13.4 pg/mL vs. 14.7 ± 4.9 pg/mL; P = 0.047). Uterine TGF-β was correlated with the relative abundance of genera Treponema (r = −0.668; P = 0.049) in resulting non-pregnant cows on d −21 and with the relative abundance of genera Ureaplasma (r = 0.901; P = 0.0004) in resulting pregnant cows on d −2. In resulting pregnant animals, a tendency for a strong correlation was detected between d −2 progesterone concentrations and uterine TGF-β concentrations (r = 0.591, P = 0.07). Overall IL-6 concentrations in the uterus were greater in resulting non-pregnant than pregnant cows (198.7 ± 21.8 pg/mL vs. 144.3 ± 16.1 pg/mL; P = 0.045). A correlation was also detected between uterine IL-6 concentrations and the relative abundance of genera Butyrivibrio (r = 0.742; P = 0.022) in resulting non-pregnant cows on d −21. These results suggest possible relationships between different bacterial communities and cytokine concentrations within the uterus of beef cattle prior to TAI that may ultimately affect fertility outcomes.

Importance of the female reproductive tract microbiome and its relationship with the uterine environment for health and productivity in cattle: A review

“…Greater levels of gene expression related to inflammation was observed in heifers of lesser fertility (Killeen et al, 2014). Intra-uterine cytokine concentrations were different prior to TAI between cows that became pregnant and those that did not, including a greater concentration of anti-inflammatory cytokine TGF-b in those that became pregnant (Poole et al, 2021), indicating a potential influence of the cytokines in the uterine environment on pregnancy establishment. Additionally, uterine cytokines such as TGF-b, IL-1b, and IL-6 were correlated to the abundance of various bacteria genera, suggesting a potential influence by the uterine bacterial communities (Poole et al, 2021).…”

“…Intra-uterine cytokine concentrations were different prior to TAI between cows that became pregnant and those that did not, including a greater concentration of anti-inflammatory cytokine TGF-b in those that became pregnant (Poole et al, 2021), indicating a potential influence of the cytokines in the uterine environment on pregnancy establishment. Additionally, uterine cytokines such as TGF-b, IL-1b, and IL-6 were correlated to the abundance of various bacteria genera, suggesting a potential influence by the uterine bacterial communities (Poole et al, 2021). Therefore, imbalances in cytokine concentrations in the uterus at crucial timepoints of the estrous cycle and pregnancy establishment or increases of pro-inflammatory cytokines at the improper time may reduce reproductive efficiency.…”

“…The presence of the bacteria in this family, and many others throughout the reproductive tract, may be important for preventing the negative impacts of inflammation to maintain an environment suitable for optimal reproductive success. Similar to the reproductive tract microbiome, cytokines and chemokines can fluctuate overtime, including through the attainment of puberty (Ault-Seay et al, 2021), across the estrous cycle (Krakowski and Zdzisinska, 2007;Oliveira et al, 2013;Poole et al, 2021), and during pregnancy (Krakowski and Zdzisinska, 2007;Oliveira et al, 2013). In comparison, uterine cytokines were observed to fluctuate during estrous synchronization with minimal change in the vagina (Poole et al, 2021).…”

Endometrial gene expression in response to lipopolysaccharide between estrous cycle phases and uterine horns in cattle

“…Cytokines and chemokines are commonly known for regulating inflammation and immune cell recruitment (Dimberg, 2010), but are also involved in reproductive processes such as corpus luteum (CL) function, embryo development, placental attachment, and preventing rejection of the fetus (Zolti et al, 1991;Simoń et al, 1998;Penny et al, 1999;Ealy et al, 2021). The presence of cytokines and chemokines have shown to fluctuate across the estrous cycle and pregnancy, and throughout puberty attainment (Krakowski and Zdzisinska, 2007;Oliveira et al, 2013;Ault-Seay et al, 2021;Poole et al, 2021). Due to the importance of inflammatory balance in the uterus (Raghupathy, 2001), minor shifts in bacterial communities may disrupt this balance and negatively influence reproductive success.…”

Expression of Hormones, Cytokines, and Antioxidants in Heat-Stressed Subfertile Female Dromedaries

“…Inflammation of the genital tract elicits leukocytes’ entrance, which secretes various types of cytokines and leads to implantation failure [ 4 ]. Recently, Poole and his colleagues found a significant increase in IL6 in non-pregnant versus pregnant synchronized postpartum cows’ uterine flushing [ 5 ]. However, they found the opposite trend for TGFß, which revealed increases in pregnant versus non-pregnant cows.…”