The intestine-brain axis is the core two-way regulatory pathway that maintains the human digestion and nerve homeostasis, and is also the key direction in the intersection of natural digestion and nerve-endocrine-immunity. However, how psychological stress breaks its homeostasis, how key downstream cells respond, especially whether it directly acts on the core of intestinal homeostasis through specific pathways - intestinal stem cells (ISCs), is still a key scientific question to be solved.

　　Current studies have shown that psychological stress can activate the HPA axis to interfere with the stability of the intestinal-brain axis, causing gastrointestinal abnormalities, damage to the intestinal barrier, and increasing the risk of inflammatory bowel disease (IBD). However, as the key and sensitive cells to maintain intestinal epithelial renewal and repair damage, whether psychological stress directly destroys its function through intrinsic pathways has lacked systematic mechanism explanations before, which is also a research gap in the direction of "intestinal-brain axis regulation".

　　In 2025, Bai Rongpan's team from Run Run Shaw Hospital affiliated to Zhejiang University School of Medicine published a study in Cell Discovery's "Cell Discovery" (influence factor 12.8), providing answers to this question and giving a research paradigm. It uses the title "Psychological stress-induced systemic corticosterone directly sabotages intestinal stem cells and exacerbates colitis" "Psychological stress-induced systemic corticosterone directly damages intestinal stem cells and aggravates colitis". It follows the logic of "mechanism to disease" and uses transcriptome sequencing, immunofluorescence staining, intestinal organoid culture, mouse stress and colitis models and other experiments to reveal the new "stress signal-effector molecule-target cell" pathway that psychological stress affects intestinal health, becoming an innovative breakthrough in the research of intestinal-brain axis mechanisms.

　　The core of this study found that "new molecules, new pathways, and new mechanisms" in the country's natural requirements: First, for the first time, the systemic corticosterone induced by psychological stress (the key effector molecule of HPA axis activation) is a "bridge molecule" connecting stress and intestinal damage, filling the gap in the stress signal transmission chain; second, it is clear that corticosterone directly acts on ISCs through the specific receptor NR3C1, reducing its number and proliferative activity, resulting in functional dysfunction, and establishing a direct regulatory pathway for stress and ISCs damage for the first time.

　　The study also closely follows the national natural transformation orientation and verifies through mouse models that ISCs dysfunction will reduce the intestinal epithelial renewal and repair ability, destroy barrier integrity, aggravate the symptoms of colitis and prolong the course of the disease, clarify that ISCs dysfunction is a key intermediate link in the worsening of colitis by stress, and provides a transformation path for "mechanism-to-disease intervention".　

　　Judging from the value of national natural innovation, this study has clarified the new pathway for stress regulation of "corticone-NR3C1-ISCs" for the first time, answering cellular-level problems inducing psychological stress to aggravate intestinal diseases, and is in line with the "new mechanisms in the intersection field" and "key targets of diseases". Funding direction: It not only opens up new branches of nerve-endocrine signal regulation stem cell function, but also extends research directions such as NR3C1 regulatory network; it also provides a theoretical basis for targeted treatment of IBD (such as NR3C1 inhibitors and ISCs protectors), laying the foundation for subsequent intervention research.

　　In summary, this study analyzes the new intestinal-brain axis pathway and builds a complete chain of "stress-molecule-stem cells-intestinal diseases". Its design ideas, mechanism logic and transformation orientation provide reference for natural declarations of intestinal-brain axis-related countries and also points out the direction for subsequent research in the field.

　　

　　1. Chronic stress damages the function of small intestinal stem cells and destroys intestinal homeostasis

　　To explore the role of psychological stress on intestinal homeostasis, the research team constructed a chronic restrained stress (CRS) model using C57BL/6J mice. Histological tests showed that mice had mild shortening of small intestinal villi after CRS treatment and significantly reduced crypt proliferation cells, suggesting impaired epithelial regeneration capacity in the small intestine (Fig. 1a–f).

　　Further studies of Lgr5-EGFP reported mice found that both flow and immunofluorescence staining showed that CRS reduced the number of intestinal Lgr5⁺ intestinal stem cells by about 1.5 times, and there was no significant change in the proportion of EGFPlow progenitor cells downstream (Fig. 1g–h); Olfm4 staining not only verified the reduction in the number of Lgr5⁺ stem cells, but also found that its proliferation activity was significantly inhibited (Fig. 1i–l).

　　During functional verification, the ability of small intestinal crypts treated with CRS was greatly reduced in vitro culture of organoids, the organoid size became smaller and the number of budding decreased, indicating that the synchronous synchronization of small intestinal stem cells' self-renewal and differentiation function was impaired (Figure 1m–p).

　　In summary, studies have confirmed that chronic stress has weakened the number and proliferation activity of small intestinal stem cells and destroyed the epithelial homeostasis of small intestine, clarified the damage effect of chronic stress on intestinal stem cells, revealed the key position of psychological factors in the regulation of intestinal stem cells, and provided experimental support for subsequent research.

　　

　　2. Adrenalectomy eliminates the inhibitory effect of chronic stress on intestinal stem cells

　　Chronic stress often promotes the release of stress hormones or catecholamines by activating the hypothalamus-pituitary-adrenal axis (HPA) or sympathetic-adrenal medulla axes (SAM). To determine whether stress affects intestinal stem cell homeostasis with systemic hormones, the researchers first performed bilateral adrenectomy (ADX) on wild-type mice, and then received chronic restrained stress (CRS) intervention for one week after recovery.

　　Histological analysis showed that ADX could block CRS-induced shallowering crypts, shortening of villus and reduced Ki-67⁺ proliferating cells (Figure 2a–d), indicating that the damage to intestinal structure by stress depends on adrenal function.

　　In Lgr5-EGFP-reported mice, flow detection found that the significantly reduced proportion of Lgr5⁺ intestinal stem cells (ISCs) in CRS was restored in the ADX group (Fig. 2e–f); further combined with EdU and Ki-67 staining analysis showed that ADX could also restore the proliferative activity of ISCs under stress to the level of the non-stressed group (Fig. 2g–h). Furthermore, organoid culture experiments showed that ADX also significantly restored CRS-inhibited crypt regeneration ability of CRS-inhibited (Fig. 2i–l).

　　In summary, studies have confirmed that the adrenal gland mediates the inhibitory effect of chronic stress on small intestinal stem cells, suggesting that systemic stress hormones are a key factor in homeostasis imbalance of intestinal stem cells.

　　

　　3. Corticosterone is a key conduction factor that affects intestinal stem cells

　　Psychological stress activates the adrenal glands and releases hormones such as corticosterone and norepinephrine to mediate systemic reactions. This study found that mice treated with chronic tethering stress (CRS) had significantly increased corticosterone levels in the blood, and norepinephrine also showed an upward trend.

　　To verify whether these hormones mediate the effect of stress on intestinal homeostasis, wild-type (WT) mice were injected with corticosterone or norepinephrine intraperitoneal cavity (Figure 3a–b). The results showed that only the corticosterone treatment group showed small intestinal changes similar to CRS: the crypt depth became shallower, Ki-67⁺ cells decreased, and the number of Lgr5⁺ and Olfm4⁺ stem cells decreased significantly (Fig. 3c–j); at the same time, corticosterone also inhibited the proliferation ability of stem cells, causing the proportion of EdU⁺Olfm4⁺ and GFP⁺Ki-67⁺ cells to be significantly reduced (Fig. 3k–m).

　　In vitro organoid culture experiments further confirmed that corticosterone treatment will lead to a decrease in organoid formation efficiency, and the organoid volume will become smaller and the number of budding decreases (Figure 3n–q).

　　In summary, research reveals that corticosterone plays a core role in the damage of small intestinal stem cells due to psychological stress and is a key systemic factor that destroys intestinal homeostasis.

　　

　　4. Stress-induced corticosterone directly inhibits intestinal stem cell function through NR3C1

　　Corticosterone can combine glucocorticoid receptor (GR, namely NR3C1) to regulate various physiological and pathological processes. Immunofluorescence results show that NR3C1 is highly expressed in small intestinal epithelial cells, especially in intestinal stem cells (ISCs), suggesting that corticosterone may act directly on ISCs.

　　To verify this hypothesis, the researchers specifically knocked out Nr3c1 in ISCs through Lgr5-creERT2 and then treated with chronic restraint stress (CRS). The results showed that, similar to adrenectomy (ADX) mice, Nr3c1 deletion significantly blocked CRS-induced shallowness of crypts and Ki-67⁺ cell reduction (Fig. 4a–d), while restoring the number and proliferation activity of Lgr5⁺ stem cells under stress (Fig. 4e–h); in vitro organoid culture also confirmed that stem cells deleting NR3C1 maintained normal regeneration capacity under stress conditions (Fig. 4i–l).

　　Corticosterone was further supplemented directly in the in vitro organoid system and found that it could inhibit organoid growth dose-dependently; and after the addition of the NR3C1 antagonist RU486 (mifepristone), organoid growth significantly recovered (Fig. 4m–o).

　　In summary, the study has made it clear that stress-induced corticosterone acts directly on ISCs through NR3C1, inhibiting its proliferation and function. This pathway is a key molecular mechanism by which psychological stress interferes with intestinal homeostasis.

　　

　　5. Corticone remodels the transcriptome characteristics of intestinal stem cells

　　In order to deeply explore the molecular mechanism by which corticosterone mediates stress to inhibit the function of intestinal stem cells (ISCs), the research team collected Lgr5-EGFPhi ISCs in mice treated with single-time binding stress or corticosterone injections, and conducted RNA sequencing analysis (Figure 5a). Cell subtype characteristic gene expression analysis confirmed that the selected cell population was high-purity ISCs.

　　Differential analysis showed that stress treatment and corticosterone injection significantly downregulated the expression of stem cell marker genes, classic Wnt target genes and various cell proliferation regulation-related genes (Fig. 5b), suggesting that the stemness and proliferation ability of ISCs are suppressed. A further comparison of the differential genes revealed that there were significantly overlapping altered genes in the two groups; GSEA analysis confirmed that the FoxO and adipose factor signaling pathway gene sets were significantly upregulated in both groups (Fig. 5c).

　　In summary, studies have shown that stress and its key mediator corticosterone can inhibit the activation of stem cell function-related pathways by regulating the ISCs transcriptome, and the FoxO signaling pathway may be one of the core downstream mechanisms mediating this effect.

　　

　　6. Corticone inhibits intestinal stem cell function through FKBP5-AKT-FoxO signaling pathway

　　The FoxO signaling pathway is crucial in regulating physiological processes such as cell cycle and proliferation. To explore its upstream regulatory factors, researchers conducted an intersection analysis of differentially expressed genes in the chronic bondage stress (CRS) and corticosterone treatment group, and found that a total of 53 genes were up-regulated and 11 genes were down-regulated in the two groups (Fig. 5d). Among them, Fkbp5 was significantly upregulated and it was known to forwardly regulate the FoxO pathway (Fig. 5e–f); independent sample experiments further confirmed that Fkbp5 expression was significantly elevated in the small intestine and colon crypts of stress or corticosterone-treated mice (Fig. 5g–h).

　　Mechanism investigation shows that in vitro organoid culture experiments show that corticosterone can upregulate Fkbp5 expression by binding to NR3C1 (Fig. 5i); ChIP-qPCR further confirmed that corticosterone can promote the binding of NR3C1 to the Fkbp5 promoter region (Fig. 5j). To verify whether FKBP5 mediates the adverse effects of corticosterone on intestinal stem cells (ISCs), the investigators added a highly selective FKBP5 inhibitor SAFit2 to the organoid system, and the results showed that the inhibition of organoid growth caused by corticosterone was significantly reversed (Fig. 6a–c).

　　Studies have shown that FKBP5 can form a complex with AKT and PHLPP through the domain, enhance PHLPP-mediated AKT dephosphorylation, thereby promoting FOXO1 dephosphorylation and nuclear translocation, and inhibiting the cell cycle. The immunoblotting results of this study showed that corticosterone or stress treatment significantly reduced p-AKT (S473) levels in the small intestine and colon crypts, while SAFit2 restored AKT activity and reduced FOXO1 nuclear translocation (Fig. 6d–g), thereby downregulating the expression of cell cycle inhibitors p130 and p21 (Fig. 6h).

　　In summary, the study has made it clear that stress-induced corticosterone can activate NR3C1, promote Fkbp5 expression, and then inhibit AKT phosphorylation, promote FOXO1 nuclear localization, and ultimately lead to the hindered proliferation of ISCs; this FKBP5-AKT-FOXO1 axis is the core mechanism by which stress-corticosterone damages intestinal stem cells.

　　

　　7. Stem cell dysfunction mediates stress and aggravate colitis

　　Several epidemiological studies have confirmed that psychological stress is closely related to inflammatory bowel disease (IBD). Studies have found in the DSS-induced colitis model that chronic stress can aggravate the inflammatory response by regulating intestinal flora and activating intestinal glial cells. Given the core role of intestinal stem cells (ISCs) in intestinal epithelial repair, researchers have proposed hypothesis that dysfunction of ISCs caused by stress may be an important mechanism for the hindrance of intestinal barrier repair and aggravation of inflammation.

　　To test this hypothesis, the investigators induce DSS colitis in Lgr5-creERT2; NR3C1fl/fl mice treated with chronic tethering stress (CRS). The results showed that ISCs-specific Nr3c1 deletion can restore p-AKT (S473) levels, reduce FOXO1 nuclear translocation, and thus reverse the reduction in the number and decreased proliferation capacity of ISCs caused by CRS (Fig. 4e–h).

　　More importantly, compared with wild-type mice treated with CRS, ISCs-specific Nr3c1 deletion can significantly alleviate stress-severe colitis: mice have partial weight recovery, disease activity index (DAI) decreased, and colon length prolonged (Fig. 7a–e); histological tests showed that intestinal epithelial injury and inflammatory cell infiltration were significantly reduced (Fig. 7f–h), and Lgr5⁺ stem cells and their proliferation ability were also effectively restored (Fig. 7i–k).

　　In summary, studies have shown that although the ISCs-specific Nr3c1 deficiency cannot completely eliminate inflammation, it can significantly resist the aggravation of stress-induced colitis, suggesting that intestinal stem cell dysfunction is one of the key mechanisms for chronic stress to aggravate intestinal inflammation.

　　

　　Summarize

　　This study systematically reveals that chronic stress releases corticosterone by activating the hypothalamus-pituitary-adrenal axis (HPA axis). Corticosterone acts on the NR3C1 receptor of intestinal stem cells (ISCs), activates the FKBP5-AKT-FOXO1 signaling pathway, thereby inhibiting the proliferation and function of ISCs and destroying the intestinal epithelial homeostasis. Among them, adrenalectomy or Nr3c1 deletion in ISCs can block the damage to ISCs by stress; transcriptome analysis further clarifies that FoxO pathway activation and Fkbp5 upregulation are key mediating mechanisms. Furthermore, ISCs dysfunction plays an important role in stress-increasing DSS-induced colitis, while ISCs-specific Nr3c1 deletion significantly alleviates inflammation. This study not only elucidates the molecular mechanism of psychological stress damage intestinal stem cells, but also provides a potential intervention target for the prevention and treatment of inflammatory bowel disease (IBD).