Exploring the effects of Hippo signaling pathway on rumen epithelial proliferation.

BACKGROUND: The current understanding to the mechanism of rumen development is limited. We hypothesized that the Hippo signaling pathway controlled the proliferation of rumen epithelium (RE) during postnatal development. In the present study, we firstly tested the changes of the Hippo signaling pathway in the RE during an early growing period from d5 to d25, and then we expanded the time range to the whole preweaning period (d10-38) and one week post weaning (d45). An in vitro experiment was also carried out to verify the function of Hippo signaling pathway during RE cell proliferation. RESULTS: In the RE of lambs from d5 to d25, the expression of baculoviral IAP repeat containing (BIRC3/5) was increased, while the expressions of large tumor suppressor kinase 2 (LATS2), TEA domain transcription factor 3 (TEAD3), axin 1 (AXIN1), and MYC proto-oncogene (MYC) were decreased with rumen growth. From d10 to d38, the RE expressions of BIRC3/5 were increased, while the expressions of LATS2 and MYC were decreased, which were similar with the changes in RE from d5 to d25. From d38 to d45, different changes were observed, with the expressions of LATS1/2, MOB kinase activator 1B (MOB1B), and TEAD1 increased, while the expressions of MST1 and BIRC5 decreased. Correlation analysis showed that during the preweaning period, the RE expressions of BIRC3/5 were positively correlated with rumen development variables, while LAST2 was negatively correlated with rumen development variables. The in vitro experiment validated the changes of LATS2 and BIRC3/5 in the proliferating RE cells, which supported their roles in RE proliferation during preweaning period. CONCLUSIONS: Our results suggest that the LATS2-YAP1-BIRC3/5 axis participates in the RE cell proliferation and promotes rumen growth during the preweaning period.

YAP1/TAZ Mediates Rumen Epithelial Cell Proliferation but Not Short-Chain Fatty Acid Metabolism In Vitro.

Promoting rumen development is closely related to the health and efficient growth of ruminants. The transcriptional co-activators Yes1-associated protein (YAP1) and WW domain-containing transcription regulator protein 1 (TAZ) are key regulators of the mammalian epithelium. In the present study, we assessed the impact of YAP1/TAZ on rumen epithelial (RE) cell proliferation using their activator GA-017 (GA) and inhibitor verteporfin (VP). We also investigated whether YAP1/TAZ-dependent alteration was involved in the RE developmental process induced by sodium butyrate (SB). The results indicated that GA promoted RE cell proliferation, while VP disrupted RE cell proliferation. The Hippo, Wnt, and calcium signaling pathways were altered following the regulation of YAP1/TAZ. Upon YAP1/TAZ activation, the expression of CCN1/2 increased. However, when YAP1/TAZ was inhibited, the expression of BIRC3 decreased. In the SB-treated cells, YAP1/TAZ-induced changes were not observed. SB increased the expressions of differentiated cell marker genes and genes involved in short-chain fatty acid (SCFA) metabolism, while YAP1/TAZ did not. Thus, YAP1/TAZ could be potential targets for regulating RE cell proliferation but not for SCFA metabolism. SB could not affect YAP1/TAZ. These findings broaden our understanding of the role of YAP1/TAZ and their regulators in RE development.

3D sheep rumen epithelial structures driven from single cells in vitro.

Ruminants play a vital economic role as livestock, providing high-quality protein for humans. At present, 3D-cultured ruminant abomasum and intestinal organoids have been successfully established to study host and pathogen interaction. The rumen is a unique digestive organ of ruminants that occupies 70% of the volume of the digestive tract and its microbiota can decompose lignocellulose to support animal growth. Here we report a method for culturing rumen epithelial organoids. We found that single rumen epithelial cells form self-organized 3D structures representative of typical stratified squamous epithelium, which is similar to rumen epithelium. EGF, Noggin, Wnt3a, IGF-1, and FGF-10 significantly enhanced the seeding efficiency of organoids. Moreover, the inclusion of CHIR-99021, A83-01, SB202190, and Y-27632 is crucial for organoid formation and maintenance. Importantly, we demonstrate that rumen epithelial cells retain their ability to form organoids after passage, cryopreservation, and resuscitation. The rumen epithelial organoids express rumen cell type-specific genes, uptake fatty acids, and generate 2D cultures. In summary, our data demonstrate that it is feasible to establish organoids from single rumen epithelial cells, which is a novel in vitro system that may reduce the use of experimental animals.

The early life immune dynamics and cellular drivers at single-cell resolution in lamb forestomachs and abomasum.

BACKGROUND: Four-chambered stomach including the forestomachs (rumen, reticulum, and omasum) and abomasum allows ruminants convert plant fiber into high-quality animal products. The early development of this four-chambered stomach is crucial for the health and well-being of young ruminants, especially the immune development. However, the dynamics of immune development are poorly understood. RESULTS: We investigated the early gene expression patterns across the four-chambered stomach in Hu sheep, at 5, 10, 15, and 25 days of age. We found that forestomachs share similar gene expression patterns, all four stomachs underwent widespread activation of both innate and adaptive immune responses from d 5 to 25, whereas the metabolic function were significantly downregulated with age. We constructed a cell landscape of the four-chambered stomach using single-cell sequencing. Integrating transcriptomic and single-cell transcriptomic analyses revealed that the immune-associated module hub genes were highly expressed in T cells, monocytes and macrophages, as well as the defense-associated module hub genes were highly expressed in endothelial cells in the four-stomach tissues. Moreover, the non-immune cells such as epithelial cells play key roles in immune maturation. Cell communication analysis predicted that in addition to immune cells, non-immune cells recruit immune cells through macrophage migration inhibitory factor signaling in the forestomachs. CONCLUSIONS: Our results demonstrate that the immune and defense responses of four stomachs are quickly developing with age in lamb's early life. We also identified the gene expression patterns and functional cells associated with immune development. Additionally, we identified some key receptors and signaling involved in immune regulation. These results help to understand the early life immune development at single-cell resolution, which has implications to develop nutritional manipulation and health management strategies based on specific targets including key receptors and signaling pathways.

Assessing the Effects of Dietary Cadmium Exposure on the Gastrointestinal Tract of Beef Cattle via Microbiota and Transcriptome Profile.

Cadmium (Cd) is an environmental pollutant, widely existing in soil, and can be absorbed and accumulated by plants. Hunan Province exhibits the worst cadmium contamination of farmland in China. Ruminants possess an abundant microbial population in the rumen, which enables them to tolerate various poisonous plants. To investigate whether the rumen microbiota could respond to Cd and mitigate the toxicity of Cd-accumulated maize to ruminants, 6-month-old cattle were fed with 85.82% (fresh basis) normal whole-plant maize silage diet (CON, n = 10) or Cd-accumulated whole-plant maize silage diet (CAM, n = 10) for 107 days. When compared to the CON cattle, CAM cattle showed significantly higher gain-to-feed ratio and an increased total bacterial population in the rumen, but a decreased total bacterial population in the colon. CAM cattle had higher relative abundance of Prevotella and Lachnospiraceae ND3007 group in the rumen, and Lachnospiraceae NK4A136 group and Clostridia vadinBB60 group in the colon. Notably, microbial correlations were enhanced in all segments of CAM cattle, especially Peptostreptococcaceae in the jejunum. Transcriptome analysis revealed down-regulation of several immune-related genes in the rumen of CAM cattle, and differentially expressed genes in the rumen were mostly involved in immune regulation. These findings indicated that feeding Cd-accumulated maize diet with a Cd concentration of 6.74 mg/kg dry matter (DM) could stimulate SCFA-related bacteria in the rumen, induce hormesis to promote weight gain, and improve energy utilization of cattle.

Feasibility of feeding cadmium accumulator maize (Zea mays L.) to beef cattle: Discovering a strategy for eliminating phytoremediation residues.

Eco-friendly and efficient strategies for eliminating cadmium (Cd) phytoremediation plant residues are needed. The present study investigated the feasibility of feeding Cd accumulator maize to beef cattle. In total, 20 cattle at 6 months of age were selected and randomly allocated into two groups fed with 85.82% (fresh basis) Cd accumulator maize (CAM) or normal maize (control [Con]) silage diets for 107 d. Feeding CAM did not affect the body weight (P = 0.24), while it decreased feed intake and increased feed efficiency of beef cattle (P < 0.01). Feeding CAM increased serum concentrations of immunoglobulin A and G, complement 3 and 4, blood urea nitrogen, and low-density lipoprotein cholesterol, decreased serum concentrations of interleukin-6 and lipopolysaccharide (P < 0.05), and caused wider lumens in the renal tubules. The Cd residue in meat was 7 µg/kg beyond the restriction for human food. In the muscle, the unsaturated fatty acids (t11C18:1 and C20:4), Lys, Arg, Pro, and Cys were decreased, while the saturated fatty acids (C10:0, C12:0, and C17:0) and Leu were increased (P < 0.05). Therefore, at the current feeding level, phytoremediation maize increased the feed efficiency of beef cattle, but did present risks to cattle health and production safety, and decreased the meat nutrition and flavor. Further research must be performed to determine whether a lower proper dose of phytoremediation maize and an appropriate feeding period may be possible to ensure no risk to cattle health and the supply of safe meat for humans.