Bone regeneration remains a clinical challenge with limited bone substitutes, urging for effective alternative strategies. Nanotubes, especially carbon nanotubes and titanium dioxide nanotubes, have been widely utilized for bone regeneration; however, their further applications were limited by the composition and degradability. As naturally occurring aluminosilicate nanoclay, halloysite nanotubes (HNTs), with good biocompatibility, functionality, and nanotubular structures, may be a promising platform for promoting bone regeneration. Herein, we presented a HNTs incorporated hydrogel and explored the potential bone tissue engineering applications of HNTs. The HNTs encapsulated hydrogel was simply fabricated by using the photopolymerization method with gelatin methacrylate (GelMA) and HNTs. The incorporation of HNTs led to an enhanced mechanical performance while maintaining a good cytocompatibility in vitro. The osteogenic activities of the HNTs incorporated platform have also been studied in vitro and in vivo. Remarkably, the addition of HNTs obviously upregulated the expression of osteogenic differentiation-related genes and concomitant protein of human dental pulp stem cells (hDPSCs) and therefore facilitated subsequent bone regeneration in calvarial defects of rats. Overall, the results obtained in this study highlight the bone regeneration capacity of HNTs, which may enhance current understanding of HNTs, and present a promising alternative strategy for bone regeneration.

Background As the global population continues to grow, competition for resources between humans and livestock has been intensifying. Increasing milk protein production and improving feed efficiency are becoming increasingly important to meet the demand for high-quality dairy protein. In a previous study, we found that milk protein yield in dairy cows was associated with the rumen microbiome. The objective of this study was to elucidate the potential microbial features that underpins feed efficiency in dairy cows using metagenomics, metatranscriptomics, and metabolomics. Results Comparison of metagenomic and metatranscriptomic data revealed that the latter was a better approach to uncover the associations between rumen microbial functions and host performance. Co-occurrence network analysis of the rumen microbiome revealed differential microbial interaction patterns between the animals with different feed efficiency, with high-efficiency animals having more and stronger associations than low-efficiency animals. In the rumen of high-efficiency animals, Selenomonas and members of the Succinivibrionaceae family positively interacted with each other, functioning as keystone members due to their essential ecological functions and active carbohydrate metabolic functions. At the metabolic level, analysis using random forest machine learning suggested that six ruminal metabolites (all derived from carbohydrates) could be used as metabolic markers that can potentially differentiate efficient and inefficient microbiomes, with an accuracy of prediction of 95.06%. Conclusions The results of the current study provided new insights into the new ruminal microbial features associated with feed efficiency in dairy cows, which may improve the ability to select animals for better performance in the dairy industry. The fundamental knowledge will also inform future interventions to improve feed efficiency in dairy cows.

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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.

Background Residual feed intake (RFI) is an inheritable measure of feed efficiency that is independent on level of production. However, physiological and metabolic mechanisms underlying divergent RFI are not fully elucidated. This study was conducted to investigate dietary nitrogen (N) partitioning and microbial protein synthesis in lactating dairy cows divergent in phenotypic RFI. Results Thirty Holstein dairy cows (milk yield = 35.3 ± 4.71 kg/d; milk protein yield = 1.18 ± 0.13 kg/d; mean ± standard deviation) were selected for the experiment to derive RFI. After the RFI measurement period of 50 d, the 10 lowest RFI cows and 8 highest RFI cows were selected. The low RFI cows had lower dry matter intake (DMI, P < 0.05) than the high RFI cows, but they produced similar energy-corrected milk. The ratios of milk to DMI (1.41 vs. 1.24, P < 0.01) and energy-corrected milk to DMI (1.48 vs. 1.36, P < 0.01) were greater in low RFI cows than those in the high RFI cows. The low RFI cows had lower milk urea nitrogen than that in the high RFI cows ( P = 0.05). Apparent digestibility of nutrients did not differ between two groups ( P > 0.10). Compared with high RFI animals, the low RFI cows had a lower retention of N (5.72 vs. 51.4 g/d, P < 0.05) and a higher partition of feed N to milk N (29.7% vs. 26.5%, P < 0.05). Conclusions The results suggest that differences in N partition, synthesis of microbial protein, and utilization of metabolizable protein could be part of the mechanisms associated with variance in the RFI. Electronic supplementary material The online version of this article (10.1186/s40104-019-0356-3) contains supplementary material, which is available to authorized users.

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Background: Mesenchymal stem cells (MSCs) have a limited self-renewal ability, impaired multi-differentiation potential, and undetermined cell senescence during in vitro series expansion. To address this concern, we investigated the effects of the microenvironment provided by stem cells from human exfoliated deciduous teeth (SHED) in maintaining the stemness of human bone marrow mesenchymal stem cells (hBMSCs) and identified the key factors and possible mechanisms responsible for maintaining the stemness of MSCs during long-term expansion in vitro. Methods: The passage 3 (P3) to passage 8 (P8) hBMSCs were cultured in the conditioned medium from SHED (SHED-CM). The percentage of senescent cells was evaluated by β-galactosidase staining. In addition, the osteogenic differentiation potential was analyzed by reverse transcription quantitative PCR (RT-qPCR), Western blot, alizarin red, and alkaline phosphatase (ALP) staining. Furthermore, RT-qPCR results identified hepatocyte growth factor (HGF) and stem cell factor (SCF) as key factors. Thus, the effects of HGF and SCF on mitochondrial function were assessed by measuring the ROS and mitochondrial membrane potential levels. Finally, selected mitochondrialrelated proteins associated with the PI3K/AKT, ERK1/2, and STAT3 signaling pathways were investigated to determine the effects of HGF and SCF in preserving the mitochondrial function of hBMSCs during long-term expansion.