AbstractNutritional intervention can greatly benefit people who suffer from side effects of medical treatments by improving intestinal post‐damage recovery. The recovery process is dependent on the regeneration of intestinal epithelial cells, which is driven by Lgr5+ intestinal stem cells (ISCs). Lactoferrin (LF) is a natural milk‐abundant protein with several gut health‐related functions such as antibacterial and immunoregulation activities, thus protecting intestine from damage. However, it is unclear whether LF also plays a role in the repair of the injured intestine, despite limited clues on its ability to modulate intestinal epithelial cell growth in vitro. Here, we show that LF accelerates intestinal epithelial recovery after both dextran sulfate sodium challenge on mice and TNF‐α treatment on intestinal organoids. Furthermore, we find LF gives rise to ISC‐mediated epithelial regeneration by directly activating the Lgr5+ stem cells. Finally, we identify Lrp5/Wnt signaling as the key pathway for LF‐enhancing ISC stemness and function. Overall, our study reveals the potential of LF as a nutrient that can be applied to promote intestinal healing.

Intestinal stem cells (ISCs) initiate intestinal epithelial regeneration and tumorigenesis, and they experience rapid refilling upon various injuries for epithelial repair as well as tumor reoccurrence. It is crucial to reveal the mechanism underlying such plasticity for intestinal health. Recent studies have found that metabolic pathways control stem cell fate in homeostasis, but the role of metabolism in the regeneration of ISCs after damage has not been clarified. Here, we find that in a human colorectal cancer dataset, miR-29a and b (miR-29a/b) are metabolic regulators highly associated with intestinal tumorigenesis and worse prognostic value of radiotherapy. We also show that these two microRNAs are required for intestinal stemness maintenance in mice, and their expression is induced in regenerated ISCs after irradiation injury, resulting in skewed ISC fate from differentiation towards self-renewal. This upregulation of miR-29a/b expression in ISCs leads to suppression of fatty acid oxidation (FAO) and depression of oxidative phosphorylation, which in turn controls the balance between self-renewal and differentiation of ISCs. Deletion of miR-29a/b prevents these effects and thus impairs ISC-mediated epithelial recovery. Finally, we filter the potential targets of miR-29a/b and identify Hnf4g, a transcription factor, that drives this metabolic reprogramming through regulating FAO-related enzymes. Our work discovers an important metabolic mechanism of ISC-mediated regeneration and potentially pave the way for more targeted and effective therapeutic strategies for intestinal repair as well as tumor treatment.

Milk-derived small extracellular vesicles (M-sEVs), a critical bioactive component in breast milk, are believed to have an essential role in health, especially in infant development. In early life, bifidobacteria are a dominant genera in the gastrointestinal tract, which can be regulated by specific compounds such as human milk oligosaccharides. However, little is known about the effects of M-sEVs on bifidobacteria. Here, a novel method to generate high-yield M-sEVs was developed and then representative bifidobacteria species were exposed to those M-sEVs. We found that M-sEVs stimulated the growth of bifidobacteria and were absorbed by the bifidobacteria. Different bifidobacteria species responded variously to the M-sEVs. Next, we demonstrated that M-sEVs altered the mRNA profile of B. longum subsp. infantis, and regulated some genes related to carbohydrate metabolism of B. longum subsp. infantis and other bifidobacteria species to accelerate bifidobacteria growth. Overall, the study revealed the supportive effects of M-sEVs on bifidobacteria, and the mechanisms involved.

SCOPE:Milk-derived small extracellular vesicles (M-sEVs) are critical bioactive components in milk. They are considered to be regulators in milk that may have promising applications. Understanding their biological effects would be important in nutrition. Intestinal organoids and mice are used to explore the effects of M-sEVs on intestinal regeneration.METHODS AND RESULTS:M-sEVs could be absorbed by intestinal epithelia and upregulate expression of the microRNAs (miRNAs) expressed in milk: miR-148a, miR-22, miR-30, and miR-29a. Interestingly, M-sEVs promote proliferation of intestinal epithelia and repairs the epithelial damage that is caused by tumor necrosis factor-α in intestinal organoids. M-sEVs ameliorate intestinal mucosa damage in mice caused by treatment with dextran sulfate sodium, as well as increasing expression of the intestinal stem cells (ISC) markers leucine-rich repeat containing G-protein-coupled receptor 5 (Lgr5), olfactomedin 4 (Olfm4), and Achaete-Scute Family BHLH Transcription Factor 2 (Ascl2) and stimulating intestinal epithelial proliferation to repair epithelial damage. Furthermore, miR-29 is more abundant in M-sEVs-treated mice, and miR-29 could upregulate expression of ISC marker genes and accelerates intestinal regeneration to recover damaged intestinal epithelia.CONCLUSIONS:We reveal that M-sEVs and miR-29 can accelerate intestinal stem cell-mediated epithelial regeneration and repair epithelial damage.

It is urgent to seek new potential targets for the prevention or relief of gastrointestinal syndrome in clinical radiation therapy for cancers. Vitamin D, mediated through the vitamin D receptor (VDR), has been identified as a protective nutrient against ionizing radiation (IR)-induced damage. This study investigated whether VDR could inhibit IR-induced intestinal injury and explored underlying mechanism. We first found that vitamin D induced VDR expression and inhibited IR-induced DNA damage and apoptosis in vitro. VDR was highly expressed in intestinal crypts and was critical for crypt stem/progenitor cell proliferation under physiological conditions. Next, VDR-deficient mice exposed to IR significantly increased DNA damage and crypt stem/progenitor cell apoptosis, leading to impaired intestinal regeneration as well as shorter survival time. Furthermore, VDR deficiency activated the Pmaip1-mediated apoptotic pathway of intestinal crypt stem/progenitor cells in IR-treated mice, whereas inhibition of Pmaip1 expression by siRNA transfection protected against IR-induced cell apoptosis. Therefore, VDR protects against IR-induced intestinal injury through inhibition of crypt stem/progenitor cell apoptosis via the Pmaip1-mediated pathway. Our results reveal the importance of VDR level in clinical radiation therapy, and targeting VDR may be a useful strategy for treatment of gastrointestinal syndrome.