Ruminal epithelium: a checkpoint for cattle health

Alginate Oligosaccharide Alleviates Lipopolysaccharide-Induced Apoptosis and Inflammatory Response of Rumen Epithelial Cells through NF-κB Signaling Pathway

AOS alleviates inflammatory responses; however, whether it exerts an effect on the rumen or regulates rumen inflammatory reaction remains unknown. In this study, firstly, the ovine ruminal epithelial cells (ORECs) were treated with 0, 200, 400, 600, and 800 µg/mL AOS, hoping to explore whether AOS hurt cell health. The results showed that compared with the AOS-0 group, the AOS-400 group could significantly increase (p < 0.05) cell viability, reduce (p < 0.05) reactive oxygen species (ROS) and interleukin (IL)-6 content, and have no adverse effect on cells. Secondly, we used LPS to construct an in vitro inflammatory model of rumen epithelial cells and then explored the protective role of AOS on rumen epithelial cells. The study was divided into three groups: the control group (CON), LPS, and LPS + AOS. The results demonstrated that the LPS + AOS group significantly increased the cell viability and reduced the ROS level in comparison with the LPS group (p < 0.05). Pretreatment with AOS also repressed (p < 0.05) the secretion of IL-1β, IL-6, IL-8, and immunoglobulin (Ig)A from ORECs in the culture medium following LPS. In terms of tight junction (TJ) proteins, AOS treatment also significantly increased (p < 0.05) the zonula occludens 1 (ZO-1) and Occludin expression. The apoptosis rate, Caspase3, Caspase9, BAD, and BCL-2/BAX were decreased (p < 0.05) after AOS treatment, and the expression of BCL-2 was increased (p < 0.05). In addition, the expressions of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor-κB (NF-κB) were inhibited (p < 0.05) with the addition of AOS. At the protein level, pretreatment of AOS decreased (p < 0.05) the expression of MyD88 and the phosphorylation level of inhibitor κB α (IκBα) after the LPS challenge. Taken together, our results indicated that AOS could alleviate the LPS-induced apoptosis and inflammatory response of rumen epithelial cells through the NF-κB signaling pathway, which may be a promising strategy for treating apoptosis and inflammation in sheep breeding.

Metabolomics and proteomics insights into subacute ruminal acidosis etiology and inhibition of proliferation of yak rumen epithelial cells in vitro

BACKGROUND

Untargeted metabolomics and proteomics were employed to investigate the intracellular response of yak rumen epithelial cells (YRECs) to conditions mimicking subacute rumen acidosis (SARA) etiology, including exposure to short-chain fatty acids (SCFA), low pH5.5 (Acid), and lipopolysaccharide (LPS) exposure for 24 h.

RESULTS

These treatments significantly altered the cellular morphology of YRECs. Metabolomic analysis identified significant perturbations with SCFA, Acid and LPS treatment affecting 259, 245 and 196 metabolites (VIP > 1, P < 0.05, and fold change (FC) ≥ 1.5 or FC ≤ 0.667). Proteomic analysis revealed that treatment with SCFA, Acid, and LPS resulted in differential expression of 1251, 1396, and 242 proteins, respectively (FC ≥ 1.2 or ≤ 0.83, P < 0.05, FDR < 1%). Treatment with SCFA induced elevated levels of metabolites involved in purine metabolism, glutathione metabolism, and arginine biosynthesis, and dysregulated proteins associated with actin cytoskeleton organization and ribosome pathways. Furthermore, SCFA reduced the number, morphology, and functionality of mitochondria, leading to oxidative damage and inhibition of cell survival. Gene expression analysis revealed a decrease the genes expression of the cytoskeleton and cell cycle, while the genes expression associated with inflammation and autophagy increased (P < 0.05). Acid exposure altered metabolites related to purine metabolism, and affected proteins associated with complement and coagulation cascades and RNA degradation. Acid also leads to mitochondrial dysfunction, alterations in mitochondrial integrity, and reduced ATP generation. It also causes actin filaments to change from filamentous to punctate, affecting cellular cytoskeletal function, and increases inflammation-related molecules, indicating the promotion of inflammatory responses and cellular damage (P < 0.05). LPS treatment induced differential expression of proteins involved in the TNF signaling pathway and cytokine-cytokine receptor interaction, accompanied by alterations in metabolites associated with arachidonic acid metabolism and MAPK signaling (P < 0.05). The inflammatory response and activation of signaling pathways induced by LPS treatment were also confirmed through protein interaction network analysis. The integrated analysis reveals co-enrichment of proteins and metabolites in cellular signaling and metabolic pathways.

CONCLUSIONS

In summary, this study contributes to a comprehensive understanding of the detrimental effects of SARA-associated factors on YRECs, elucidating their molecular mechanisms and providing potential therapeutic targets for mitigating SARA.

Red propolis extract as a natural ionophore for confined sheep: performance and morphological and histopathological changes

This study aimed to evaluate the effect of increasing levels of red propolis extract (RPE) in the diet of confined sheep on performance and histomorphometric parameters of rumen and intestine and histopathological parameters of liver and kidney. Thirty-five male sheep (17.08 ± 2.36 kg) were used, distributed in a completely randomized design, with five treatments (0, 7, 14, 21, and 28 mL day-1 RPE) and seven replications, submitted to 68 days of experiment. At the end of the experimental period, the animals were euthanized, and samples of rumen, intestine, liver, and kidney were collected to histomorphometry and histopathology analyzes. Higher RPE inclusions (21 and 28 mL day-1) maintained dry matter intake and increased total weight (5.78 x 6.14 and 6.95 kg, respectively) gain up to 20.24%. In the rumen, the inclusion of RPE led to an increase in the thickness of the epithelium and the highest level also increased the thickness of the keratinized portion of this epithelium (21.71 x 32.15 μm). The level of 21 mL day-1 provided larger ruminal papillae (1620.68 x 1641.70 μm) and greater ruminal absorption area (561791.43 x 698288.50 μm2). In intestine 21 and 28 mL-1 of RPE provided greater mucosal thickness (468.54 x 556.20 and 534.64 μm), higher goblet cell index (23.32 x 25.82 and 25.64) and higher hepatic glycogen index (1.47 x 1.64 and 1.62), supporting higher nutrients absortion and glicogenolise and intestinal health, corroborating the weight gain indices. The inclusion of RPE did not cause renal histopathological lesions. Therefore, levels of 21 and 28 mL day-1 of RPE can be used in sheep diets, promoting greater final weight gain, causing positive histomorphological changes in the rumen, intestine and liver, without causing kidney or liver damage.

Transcriptome profiling in rumen, reticulum, omasum, and abomasum tissues during the developmental transition of pre-ruminant to the ruminant in yaks

The development of the four stomachs of yak is closely related to its health and performance, however the underlying molecular mechanisms are largely unknown. Here, we systematically analyzed mRNAs of four stomachs in five growth time points [0 day, 20 days, 60 days, 15 months and 3 years (adult)] of yaks. Overall, the expression patterns of DEmRNAs were unique at 0 d, similar at 20 d and 60 d, and similar at 15 m and adult in four stomachs. The expression pattern in abomasum was markedly different from that in rumen, reticulum and omasum. Short Time-series Expression Miner (STEM) analysis demonstrated that multi-model spectra are drastically enriched over time in four stomachs. All the identified mRNAs in rumen, reticulum, omasum and abomasum were classified into 6, 4, 7, and 5 cluster profiles, respectively. Modules 9, 38, and 41 were the most significant three colored modules. By weighted gene co-expression network analysis (WGCNA), a total of 5,486 genes were categorized into 10 modules. CCKBR, KCNQ1, FER1L6, and A4GNT were the hub genes of the turquoise module, and PAK6, TRIM29, ADGRF4, TGM1, and TMEM79 were the hub genes of the blue module. Furthermore, functional KEGG enrichment analysis suggested that the turquoise module was involved in gastric acid secretion, sphingolipid metabolism, ether lipid metabolism, etc., and the blue module was enriched in pancreatic secretion, pantothenate and CoA biosynthesis, and starch and sucrose metabolism, etc. Our study aims to lay a molecular basis for the study of the physiological functions of rumen, reticulum, omasum and abomasum in yaks. It can further elucidate the important roles of these mRNAs in regulation of growth, development and metabolism in yaks, and to provide a theoretical basis for age-appropriate weaning and supplementary feeding in yaks.

Transcriptomic profiles of the ruminal wall in Italian Mediterranean dairy buffaloes fed green forage

BACKGROUND

Green feed diet in ruminants exerts a beneficial effect on rumen metabolism and enhances the content of milk nutraceutical quality. At present, a comprehensive analysis focused on the identification of genes, and therefore, biological processes modulated by the green feed in buffalo rumen has never been reported. We performed RNA-sequencing in the rumen of buffaloes fed a total mixed ration (TMR) + the inclusion of 30% of ryegrass green feed (treated) or TMR (control), and identified differentially expressed genes (DEGs) using EdgeR and NOISeq tools.

RESULTS

We found 155 DEGs using EdgeR (p-values < 0.05) and 61 DEGs using NOISeq (prob ≥0.8), 30 of which are shared. The rt-qPCR validation suggested a higher reliability of EdgeR results as compared with NOISeq data, in our biological context. Gene Ontology analysis of DEGs identified using EdgeR revealed that green feed modulates biological processes relevant for the rumen physiology and, then, health and well-being of buffaloes, such as lipid metabolism, response to the oxidative stress, immune response, and muscle structure and function. Accordingly, we found: (i) up-regulation of HSD17B13, LOC102410803 (or PSAT1) and HYKK, and down-regulation of CDO1, SELENBP1 and PEMT, encoding factors involved in energy, lipid and amino acid metabolism; (ii) enhanced expression of SIM2 and TRIM14, whose products are implicated in the immune response and defense against infections, and reduced expression of LOC112585166 (or SAAL1), ROR2, SMOC2, and S100A11, encoding pro-inflammatory factors; (iii) up-regulation of NUDT18, DNAJA4 and HSF4, whose products counteract stressful conditions, and down-regulation of LOC102396388 (or UGT1A9) and LOC102413340 (or MRP4/ABCC4), encoding detoxifying factors; (iv) increased expression of KCNK10, CACNG4, and ATP2B4, encoding proteins modulating Ca²⁺ homeostasis, and reduced expression of the cytoskeleton-related MYH11 and DES.

CONCLUSION

Although statistically unpowered, this study suggests that green feed modulates the expression of genes involved in biological processes relevant for rumen functionality and physiology, and thus, for welfare and quality production in Italian Mediterranean dairy buffaloes. These findings, that need to be further confirmed through the validation of additional DEGs, allow to speculate a role of green feed in the production of nutraceutical molecules, whose levels might be enhanced also in milk.

The intraruminal redox potential is stabilised by opposing influences during fermentation

An optimal fermentation process in the forestomach is pivotal for the wellbeing and performance of ruminants. Complex carbohydrates are broken down into short-chain fatty acids (SCFA) which form the major energy source for the animal. A strong interrelationship of this process with intraruminal pH and redox potential (Eh) exists. These parameters can be measured with intraruminal sensors, but the interpretation of the measurements, especially of Eh, and their meaning for intraruminal homeostasis is not completely clear. In this study, factors influencing intraruminal Eh were elucidated. We hypothesised that intraruminal Eh is influenced by the fermentation process as such, but not by its end products SCFA. We measured Eh and pH in ruminal fluid from fasting cannulated sheep after the addition of 0.06 m Na-acetate, -propionate, -butyrate or glucose in vitro. Furthermore, we assessed the interrelation of pH and Eh. Basal Eh and pH values were -120 ± 41 mV and 7.0 ± 0.3, respectively, in native ruminal fluid in vitro. While the addition of SCFA did not induce any changes, glucose addition caused a significant decrease in both pH and Eh compared to the values before the addition (paired Student's t-test, p < 0.05). We attribute the decrease in Eh to an increased production of H₂ in the process of generating SCFA, predominantly acetate. By titrating both native and particle-free ruminal fluid to more acidic and basic pH values (4.5-8.5), we found a non-linear inverse correlation of pH and Eh, counteracting the H₂ -driven decrease of Eh during fermentation. Thus, the intraruminal Eh is influenced by pH and H₂ output during SCFA formation. The opposed character of these factors stabilises the intraruminal homeostasis which might help maintain symbiotic microbiota in the rumen. Understanding, monitoring, and supporting this system will be an essential part of modern cattle production.

Morusin Protected Ruminal Epithelial Cells against Lipopolysaccharide-Induced Inflammation through Inhibiting EGFR-AKT/NF-κB Signaling and Improving Barrier Functions

Using phytogenic extracts for preventing or treating rumen epithelial inflammatory injury is a potential alternative to antibiotic use due to their residue-free characteristics. In this study, the efficacy of Morus root bark extract Morusin on ruminal epithelial cells (RECs) against pathogenic stimulus was investigated for the first time. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and quantitative real-time polymerase chain reaction (qPCR) results showed that the Morusin did not affect the cell viability of RECs and exerted anti-inflammatory effects in a concentration-dependent manner. Transcriptome analysis further revealed that the Morusin significantly downregulated the inflammatory-response-related cell signaling, while it upregulated the cell-proliferation-inhibition- and barrier-function-related processes in RECs upon lipopolysaccharide (LPS) stimulation. The epidermal growth factor receptor (EGFR) blocking and immunoblotting analysis further confirmed that the Morusin suppressed LPS-induced inflammation in RECs by downregulating the phosphorylation of protein kinase B (AKT) and nuclear factor-kappaB (NF-κB) p65 protein via inhibiting the EGFR signaling. These findings demonstrate the protective roles of Morusin in LPS-induced inflammation in RECs.

Transmission of the gut microbiome in cohousing goats and pigs

Social interaction facilitates the horizontal transmission of the microbiota between different individuals. However, little is known about the level of microbiota transmission in different livestock animals and different digestive tracts. The Hainan black goat and Wuzhishan pig are typical tropical local breeds on Hainan Island in China. Thus, we sampled and analyzed the gut microbiome in Hainan black goats (cecum and rumen) and Wuzhishan pigs (cecum) to study horizontal transmission by rearing them in the same pen (six goats and six pigs) or separate pens (nine goats and nine pigs). De novo assembly and binning recovered 3,262 strain-level and 2,488 species-level metagenome-assembled genomes (MAGs) using ∼1.3 Tb sequencing data. Of these MAGs, 1,856 MAGs were identified as novel strain. Compared with goats living in separate pens, social interaction in the same pen promotes community homogeneity in the rumen microbiome (P < 0.05) and the cecum microbiome (P < 0.05), respectively. Notably, approximately 7.08% (231/3262) of the gut microbial population could transmit during cohousing, 12 strains only in inter-species transmission, versus 190 strains only in intra-species transmission, and 10 strains only in foregut and hindgut transmission. In addition, the social contact group has high transmitted strain abundance, which is correlated with community composition. This study provided a new insight into the influence of social interaction on the animal gut microbiota.

Different feeding strategies can affect growth performance and rumen functions in Gangba sheep as revealed by integrated transcriptome and microbiome analyses

Due to the harsh environment in the Tibetan Plateau, traditional grazing greatly limits the growth potential of local animals and causes severe ecosystem degradation. This is an urgent issue to be solved, which requires alternative strategies for grazing animals in the Tibetan alpine pastoral livestock systems. This study aimed to investigate the effects of different feeding strategies on growth performance and ruminal microbiota-host interactions in the local breed of sheep (Gangba sheep). Thirty 9-month old Gangba sheep (n = 10 per group) were assigned to natural grazing (G), semi-grazing with supplementation (T), and barn feeding (F) groups (supplementation of concentrate and oat hay) based on body weight. At the end of the experiment (75 d), all sheep were weighed, rumen fluid was obtained from six sheep per group, and ruminal epithelium was obtained from 3 sheep per group. The results showed that: (1) Compared with the G and T groups, the F group significantly increased dry matter intake, average daily gain, and feed conversion ratio of animals. Additionally, Gangba sheep in the F group had higher concentrations of ruminal short-chain volatile fatty acids (VFAs), especially propionate and butyrate (P <0.05) than sheep in the G and T groups. (2) The principal coordinates analysis indicated a significant difference in bacterial composition among different feed strategies. More specifically, the relative abundance of propionate (unidentified F082 and Succiniclasticum) and butyrate-producing (Eubacterium_coprostanoligenes_group) genera were also observed to be increased in the F group, in which unidentified F082 was identified as a differential biomarker among the three groups according to linear discriminant analysis effect size analysis. (3) The dynamics of the rumen epithelial transcriptome revealed that ECM-receptor interactions, focal adhesion, and PI3K-Akt signaling pathways, which are critical in mediating many aspects of cellular functions such as cell proliferation and motility, were upregulated in the F group. In conclusion, under harsh conditions in the Tibetan alpine meadow, barn feeding increased ruminal VFAs concentrations (especially propionate and butyrate), which stimulated gene expression related to cell proliferation in rumen epithelium, appearing to be superior to natural grazing and semi-grazing in gaining body weight of the local Gangba sheep.

Nutritional Modulation, Gut, and Omics Crosstalk in Ruminants

Simple Summary

Over the last decade, animal nutrition science has been significantly developed, supported by the great advancements in molecular technologies. For scientists, the present "feedomics and nutrigenomics" era continues to evolve and shape how research is designed, performed, and understood. The new omics interpretations have established a new point of view for the nutrition–gene interaction, integrating more comprehensive findings from animal physiology, molecular genetics, and biochemistry. In the ruminant model, this modern approach addresses rumen microbes as a critical intermediate that can deepen the studies of diet–gut interaction with host genomics. The present review discusses nutrigenomics’ and feedomics’ potential contribution to diminishing the knowledge gap about the DNA cellular activities of different nutrients. It also presents how nutritional management can influence the epigenetic pathway, considering the production type, life stage, and species for more sustainable ruminant nutrition strategies.

Abstract

Ruminant nutrition has significantly revolutionized a new and prodigious molecular approach in livestock sciences over the last decade. Wide-spectrum advances in DNA and RNA technologies and analysis have produced a wealth of data that have shifted the research threshold scheme to a more affluent level. Recently, the published literature has pointed out the nutrient roles in different cellular genomic alterations among different ruminant species, besides the interactions with other factors, such as age, type, and breed. Additionally, it has addressed rumen microbes within the gut health and productivity context, which has made interpreting homogenous evidence more complicated. As a more systematic approach, nutrigenomics can identify how genomics interacts with nutrition and other variables linked to animal performance. Such findings should contribute to crystallizing powerful interpretations correlating feeding management with ruminant production and health through genomics. This review will present a road-mapping discussion of promising trends in ruminant nutrigenomics as a reference for phenotype expression through multi-level omics changes.

Characterization of Accessible Chromatin Regions in Cattle Rumen Epithelial Tissue during Weaning

Weaning in ruminants is characterized by the transition from a milk-based diet to a solid diet, which drives a critical gastrointestinal tract transformation. Understanding the regulatory control of this transformation during weaning can help to identify strategies to improve rumen health. This study aimed to identify regions of accessible chromatin in rumen epithelial tissue in pre- and post-weaning calves and investigate differentially accessible regions (DARs) to uncover regulatory elements in cattle rumen development using the ATAC-seq approach. A total of 126,071 peaks were identified, covering 1.15% of the cattle genome. From these accessible regions, 2766 DARs were discovered. Gene ontology enrichment resulted in GO terms related to the cell adhesion, anchoring junction, growth, cell migration, motility, and morphogenesis. In addition, putative regulatory canonical pathways were identified (TGFβ, integrin-linked kinase, integrin signaling, and regulation of the epithelial–mesenchymal transition). Canonical pathways integrated with co-expression results showed that TGFβ and ILK signaling pathways play essential roles in rumen development through the regulation of cellular adhesions. In this study, DARs during weaning were identified, revealing enhancers, transcription factors, and candidate target genes that represent potential biomarkers for the bovine rumen development, which will serve as a molecular tool for rumen development studies.

Effects of butyrate− on ruminal Ca2+ transport: evidence for the involvement of apically expressed TRPV3 and TRPV4 channels

The ruminal epithelium absorbs large quantities of NH₄⁺ and Ca²⁺. A role for TRPV3 has emerged, but data on TRPV4 are lacking. Furthermore, short-chain fatty acids (SCFA) stimulate ruminal Ca²⁺ and NH₄⁺ uptake in vivo and in vitro, but the pathway is unclear. Sequencing of the bovine homologue (bTRPV4) revealed 96.79% homology to human TRPV4. Two commercial antibodies were tested using HEK-293 cells overexpressing bTRPV4, which in ruminal protein detected a weak band at the expected ~ 100 kDa and several bands ≤ 60 kDa. Immunofluorescence imaging revealed staining of the apical membrane of the stratum granulosum for bTRPV3 and bTRPV4, with cytosolic staining in other layers of the ruminal epithelium. A similar expression pattern was observed in a multilayered ruminal cell culture which developed resistances of > 700 Ω · cm² with expression of zonula occludens-1 and claudin-4. In Ussing chambers, 2-APB and the TRPV4 agonist GSK1016790A stimulated the short-circuit current across native bovine ruminal epithelia. In whole-cell patch-clamp recordings on HEK-293 cells, bTRPV4 was shown to be permeable to NH₄⁺, K⁺, and Na⁺ and highly sensitive to GSK1016790A, while effects of butyrate⁻ were insignificant. Conversely, bTRPV3 was strongly stimulated by 2-APB and by butyrate⁻ (pH 6.4 > pH 7.4), but not by GSK1016790A. Fluorescence calcium imaging experiments suggest that butyrate⁻ stimulates both bTRPV3 and bTRPV4. While expression of bTRPV4 appears to be weaker, both channels are candidates for the ruminal transport of NH₄⁺ and Ca²⁺. Stimulation by SCFA may involve cytosolic acidification (bTRPV3) and cell swelling (bTRPV4).

Investigation of fiber utilization in the rumen of dairy cows based on metagenome-assembled genomes and single-cell RNA sequencing

BACKGROUND

Dairy cows utilize human-inedible, low-value plant biomass to produce milk, a low-cost product with rich nutrients and high proteins. This process largely relies on rumen microbes that ferment lignocellulose and cellulose to produce volatile fatty acids (VFAs). The VFAs are absorbed and partly metabolized by the stratified squamous rumen epithelium, which is mediated by diverse cell types. Here, we applied a metagenomic binning approach to explore the individual microbes involved in fiber digestion and performed single-cell RNA sequencing on rumen epithelial cells to investigate the cell subtypes contributing to VFA absorption and metabolism.

RESULTS

The 52 mid-lactating dairy cows in our study (parity = 2.62 ± 0.91) had milk yield of 33.10 ± 6.72 kg. We determined the fiber digestion and fermentation capacities of 186 bacterial genomes using metagenomic binning and identified specific bacterial genomes with strong cellulose/xylan/pectin degradation capabilities that were highly associated with the biosynthesis of VFAs. Furthermore, we constructed a rumen epithelial single-cell map consisting of 18 rumen epithelial cell subtypes based on the transcriptome of 20,728 individual epithelial cells. A systematic survey of the expression profiles of genes encoding candidates for VFA transporters revealed that IGFBP5+ cg-like spinous cells uniquely highly expressed SLC16A1 and SLC4A9, suggesting that this cell type may play important roles in VFA absorption. Potential cross-talk between the microbiome and host cells and their roles in modulating the expression of key genes in the key rumen epithelial cell subtypes were also identified.

CONCLUSIONS

We discovered the key individual microbial genomes and epithelial cell subtypes involved in fiber digestion, VFA uptake and metabolism, respectively, in the rumen. The integration of these data enables us to link microbial genomes and epithelial single cells to the trophic system. Video abstract.

Cross-tissue single-cell transcriptomic landscape reveals the key cell subtypes and their potential roles in the nutrient absorption and metabolism in dairy cattle

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Discover 55 cell types and their specific markers in the first single-cell atlas of cattle;

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Identify and verify 3 epithelial progenitor-like cell subtypes in the forestomach

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Reveal vital but nonimmune functions of neutrophils in the mammary gland;

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Uncover key cell subtypes with preferential nutrient uptake;

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Find Th17 cells regulate epithelial cells responding to nutrient transport in the forestomach.

Introduction

Dairy cattle are a vitally important ruminant in meeting the demands for high-quality animal protein production worldwide. The complicated biological process of converting human indigestible biomass into highly digestible and nutritious milk is orchestrated by various tissues. However, poorly understanding of the cellular composition and function of the key metabolic tissues hinders the improvement of health and performance of domestic ruminants.

Objectives

The cellular heterogeneity, metabolic features, interactions across ten tissue types of lactating dairy cattle were studied at single-cell resolution in the current study.

Methods

Unbiased single-cell RNA-sequencing and analysis were performed on the rumen, reticulum, omasum, abomasum, ileum, rectum, liver, salivary gland, mammary gland, and peripheral blood of lactating dairy cattle. Immunofluorescences and fluorescence in situ hybridization were performed to verify cell identity.

Results

In this study, we constructed a single-cell landscape covering 88,013 high-quality (500 < genes < 4,000, UMI < 50, 000, and mitochondrial gene ratio < 40% or 15%) single cells and identified 55 major cell types in lactating dairy cattle. Our systematic survey of the gene expression profiles and metabolic features of epithelial cells related to nutrient transport revealed cell subtypes that have preferential absorption of different nutrients. Importantly, we found that T helper type 17 (Th17) cells (highly expressing CD4 and IL17A) were specifically enriched in the forestomach tissues and predominantly interacted with the epithelial cell subtypes with high potential uptake capacities of short-chain fatty acids through IL-17 signaling. Furthermore, the comparison between IL17RA^highIL17RC^high cells (epithelial cells with IL17RA and IL17RC expression levels both greater than 0.25) and other cells explained the importance of Th17 cells in regulating the epithelial cellular transcriptional response to nutrient transport in the forestomach.

Conclusion

The findings enhance our understanding of the cellular biology of ruminants and open new avenues for improved animal production of dairy cattle.

Sodium butyrate converts Caco-2 monolayers into a leaky but healthy intestinal barrier resembling that of a newborn infant

A simple and reliable in vitro model of the infant intestinal barrier is needed to study nutrient absorption and drug permeability specifically for this life stage. This study investigated the treatment of 20 day old differentiated Caco-2 monolayers with sodium butyrate at various concentrations (0-250 mM). Monolayer integrity, cytotoxicity, permeability and inflammatory response were tracked. An intestinal barrier model, with infant gut characteristics, was developed based on the treatment of mature monolayers with 125 mM sodium butyrate for 24 h. Such treatment was not cytotoxic but caused a stable transepithelial electrical resistance value of 408 ± 52 Ω cm2. The ratio of lactulose to mannitol transport across the intestinal barrier increased 1.79-fold. Redistribution of the tight junction proteins, occludin and ZO-1, in response to sodium butyrate treatment was visualized with immunofluorescence. Levels of the cytokines, TNF-α and IL-6, although modestly increased did not indicate an inflammatory response by Caco-2 to sodium butyrate. This intestinal barrier demonstrated physiologically relevant transport rates for dairy protein of 0.01-0.06%, suggesting it may be used to track permeability of proteins in infant nutritional products.

Butyrate Permeation across the Isolated Ovine Reticulum Epithelium

Simple Summary

Short-chain fatty acids are the main source of energy for ruminants. The effective uptake of these substrates from the forestomach is a prerequisite for the health and performance of these animals. Thus far, the mechanisms of uptake have been investigated almost exclusively in the epithelium of the largest forestomach section, the rumen. Previous research suggests that the reticulum is also involved in the uptake of short-chain fatty acids, but the mechanisms involved have not been studied and may differ from those known from the rumen epithelium due to the different milieu in this compartment. To investigate this, ovine reticulum epithelium was mounted in Ussing chambers, and the transport of radiolabeled butyrate (as a representative of short-chain fatty acids) across the tissue was measured with and without the addition of inhibitors of particular transport proteins. Our results show that butyrate can be taken up effectively across the reticulum epithelium via pathways that are energized by the Na⁺/K⁺-ATPase and may involve monocarboxylate transporters, sodium-proton exchangers, and anion channels. However, our results are not completely congruent to those obtained in the rumen epithelium. These modifications could assure the effective uptake of short-chain fatty acids from the reticulum lumen under the particular conditions (p. e. high pH) of this forestomach compartment.

Abstract

We hypothesized that, due to the high pH of this compartment, the reticulum epithelium displays particular features in the transport of short-chain fatty acids (SCFA). Ovine reticulum epithelium was incubated in Ussing chambers using a bicarbonate-free buffer solution containing butyrate (20 mmol L⁻¹). p-hydroxymercuribenzoic acid (pHMB), 5-(N-Ethyl-N-isopropyl)amiloride (EIPA), or ouabain were added to the buffer solution as inhibitors of monocarboxylate transporters, sodium-proton-exchangers, or the Na⁺/K⁺-ATPase, respectively. The short-circuit current (I_sc) and transepithelial conductance (G_t) were monitored continuously while the flux rates of ¹⁴C-labelled butyrate were measured in the mucosal-to-serosal (J_ms^but) or serosal-to-mucosal direction (J_sm^but). Under control conditions, the mean values of I_sc and G_t amounted to 2.54 ± 0.46 µEq cm⁻² h⁻¹ and 6.02 ± 3.3 mS cm⁻², respectively. J_ms^but was 2.1 ± 1.01 µmol cm⁻² h⁻¹ on average and about twice as high as J_sm^but. Incubation with ouabain reduced J_ms^but, while J_sm^but was not affected. The serosal addition of EIPA did not affect J_ms^but but reduced J_sm^but by about 10%. The addition of pHMB to the mucosal or serosal solution reduced J_ms^but but had no effect on J_sm^but. Mucosally applied pHMB provoked a transient increase in the I_sc. The serosal pHMB sharply reduced I_sc. Our results demonstrate that butyrate can be effectively transported across the reticulum epithelium. The mechanisms involved in this absorption differ from those known from the rumen epithelium.