Stem Cells Translational Medicine, 14/01/2026
Introduction
Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by persistent inflammation and damage to the colonic mucosa, significantly impacting patients’ quality of life.
Current research indicates a close relationship between endoplasmic reticulum (ER) stress and the pathogenesis of various intestinal disorders, including UC. ER stress, which arises from the accumulation of misfolded proteins in the ER, triggers the unfolded protein response (UPR) to restore homeostasis. However, prolonged or unresolved ER stress can lead to cellular apoptosis via CHOP-dependent or independent induction of Bcl2-like 11 (Bcl2L11), NADPH oxidase activator (NOXA), and p53 unregulated apoptosis modulator (PUMA), contributing to the exacerbation of inflammatory responses and tissue damage in UC.
In particular, the inositol-requiring enzyme 1 (IRE1)–X-box binding protein 1 (XBP1) axis of the UPR plays a pivotal role in mitigating ER stress by promoting XBP1 mRNA splicing. This spliced form of XBP1 enhances the production of ER chaperones and other proteins that help alleviate ER stress, thus protecting epithelial cells from stress-induced apoptosis. Genetic variants in XBP1, which lead to spontaneous enteritis, were identified to have link to increased risk of both Crohn’s disease and UC.
Recent studies have highlighted the promise of mesenchymal stem cells (MSCs), particularly those derived from umbilical cord tissues, in modulating inflammation and promoting tissue repair. In preclinical and clinical studies, MSCs and their derived exosomes have demonstrated beneficial effects in treating UC, primarily by reducing inflammation and enhancing mucosal healing. However, the specific impact of MSC therapy on ER stress in UC has not yet been fully elucidated.
Here, we hypothesize that human umbilical cord–derived MSCs (hUC-MSCs) alleviate UC by targeting the IRE1/XBP1 axis to resolve ER stress and inhibit epithelial apoptosis. Using a DSS-induced murine colitis model and TNF-α-stimulated colon epithelial cells, we investigate whether hUC-MSCs restore ER homeostasis through XBP1 splicing, thereby bridging the gap between MSC therapy and ER stress modulation in UC. This study not only elucidates a novel mechanistic pathway but also highlights the translational potential of hUC-MSCs for clinical UC management.
Methods
Human umbilical cord – derived mesenchymal stem cells (hUC-MSCs) were cultured in DMEM/F12 supplemented with 10% fetal bovine serum and 0.5% penicillin-streptomycin under standard conditions (37°C, 5% CO2). When cell confluence reached approximately 80%, the medium was replaced with serum-free medium to prepare hUC-MSC conditioned medium (hUC-MSC-CM), which was collected, filtered through 0.22 μm filters, and stored at −70°C.
Female SPF C57BL/6 mice (6-8 weeks old) were randomly assigned to control, DSS + PBS, or DSS + hUC-MSC groups. Experimental colitis was induced by administering 4% dextran sulfate sodium (DSS) in drinking water for 7 days. Control mice received regular water.
Mice in the DSS + hUC-MSC group received intraperitoneal injections of hUC-MSCs (1.0 × 10⁶ cells in 100 μL PBS) on days 3, 5, and 7, while control and DSS + PBS groups received PBS only. Body weight, disease activity index (DAI), and survival were monitored daily. Mice were euthanized on day 8 for tissue collection. Colons were harvested for length measurement, histological analysis, myeloperoxidase (MPO) activity assays, and RNA extraction.
Colon tissues were processed for histological analysis, myeloperoxidase (MPO) activity assays, RNA extraction, and protein analysis. Histological inflammation was evaluated on H&E-stained sections using standardized epithelial damage and inflammatory infiltration scores. Apoptosis and proliferation were assessed by immunohistochemistry for cleaved caspase-3 and Ki-67.
Total RNA was extracted using TRIzol and analyzed by quantitative real-time PCR (qRT-PCR). Protein expression was examined by Western blotting. Transcriptome sequencing was performed using the Illumina NovaSeq platform, followed by differential gene expression and functional enrichment analyses, including identification of endoplasmic reticulum (ER) stress–related genes.
In vitro, immortalized mouse colon epithelial cells were treated with TNF-α, with or without the IRE1 inhibitor 4μ8C. Apoptosis was assessed by Annexin V/PI staining followed by flow cytometry.
Results
- Intraperitoneal hUC-MSCs treatment alleviated the DSS-induced colitis in mice model
Upon DSS administration, DAI increased in all DSS-treated mice, peaking at days 7–8, then gradually declined. Following DSS withdrawal, DAI decreased more rapidly in the hUC-MSC-treated group. Body weight loss occurred between days 4 and 9 but recovered faster in the hUC-MSC group. Survival was significantly improved with hUC-MSC treatment.
Colon shortening, a hallmark of colitis, was markedly attenuated by hUC-MSC treatment. MPO activity, reflecting neutrophil infiltration, decreased by ~45% in hUC-MSC–treated mice compared with PBS controls. TNF-α expression was also significantly reduced. Collectively, hUC-MSCs exerted both preventive and therapeutic effects in acute colitis.
- hUC-MSC treatment attenuated DSS-induced colon epithelial injury
DSS administration disrupted the intestinal epithelial barrier, causing crypt loss, inflammatory cell infiltration, and elevated histopathological scores. DSS also increased epithelial apoptosis and reduced proliferation, as evidenced by increased cleaved caspase-3 and decreased Ki67 expression.
Compared with DSS+PBS mice, hUC-MSC–treated mice showed preserved crypt architecture, reduced inflammation, lower histological scores, decreased epithelial apoptosis, and restored Ki67 expression. The tracking experiments revealed that Dil-labeled hUC-MSCs homed to inflamed colonic tissue within 24 h, preferentially accumulating in the epithelium.
- hUC-MSCs treatment reduced colon tissue gene expression profile change in DSS-induced colitis
RNA-seq analysis revealed extensive transcriptional dysregulation following DSS treatment. hUC-MSC therapy markedly reduced the number of differentially expressed genes and shifted the transcriptional profile toward that of normal controls, as shown by PCA and hierarchical clustering. Pro-inflammatory chemokines, cytokines, and inflammatory genes upregulated by DSS were downregulated by hUC-MSCs, whereas barrier- and anti-inflammatory – associated genes were restored. xCell analysis showed that DSS depleted intestinal epithelial cells (IECs), whereas hUC-MSCs treatment significantly restored IEC enrichment.
- hUC-MSC treatment suppressed pathological ER stress induced by DSS
DSS altered the expression of multiple ER stress–response genes, most of which were normalized by hUC-MSC treatment. GO analysis highlighted enrichment in ER stress response, unfolded protein response, autophagy, apoptosis, and IRE1-mediated signaling. Key ER stress markers (Casp12, Nupr1, IFN-γ) were reduced, whereas Agr2 expression was restored by hUC-MSCs. Bcl2l11 expression was normalized at both mRNA and protein levels.
Mechanistically, hUC-MSCs enhanced IRE1 phosphorylation, increased Xbp1-S, and reduced Xbp1-U, indicating activation of protective IRE1/XBP1 signaling.
- hUC-MSCs inhibited TNF-α-induced ER stress and IEC apoptosis via paracrine signaling
TNF-α induced ER stress–related genes overlapping with those altered in DSS colitis. In vitro, MSC-conditioned medium (MSC-CM) suppressed TNF-α–induced IEC apoptosis, inhibited BCL2L11 expression, and promoted IRE1 phosphorylation and Xbp1 splicing. Importantly, inhibition of Xbp1 splicing by 4μ8C abolished the protective effects of MSC-CM. These data indicate that hUC-MSCs protect IECs through paracrine activation of the IRE1/XBP1 pathway, thereby alleviating ER stress and epithelial apoptosis.
Conclusions
This study has several limitations that should be considered when interpreting the results. The dextran sulfate sodium (DSS)–induced colitis model, although widely used, does not fully recapitulate the chronic relapsing nature and multifactorial pathogenesis of human ulcerative colitis (UC). Therefore, the therapeutic effects observed in this model may not entirely reflect disease complexity in clinical settings.
In addition, the current findings are based exclusively on preclinical experiments. The therapeutic efficacy and safety of human umbilical cord–derived mesenchymal stem cells (hUC-MSCs) in patients with UC require further validation through well-designed clinical trials.
Collectively, our study demonstrates that intraperitoneal administration of hUC-MSCs effectively alleviates DSS-induced colitis in mice. Tracking experiments revealed that injected hUC-MSCs can home to both the epithelium and lamina propria of inflamed colonic tissue. these findings highlight the therapeutic potential of hUC-MSCs for the management of ulcerative colitis and support targeting ER stress as a promising strategy for the development of future treatments for UC.
References: Zhao, T., Hou, W., Wang, M., Feng, Z., Feng, X., Wang, H., Zhao, H., Li, X., Hou, S., Zheng, G., Zhang, X., & Xie, J. (2026). Human umbilical cord mesenchymal stem cells alleviate colon epithelial apoptosis in ulcerative colitis by activating inositol-requiring enzyme 1/X-box binding protein 1 signaling. Stem cells translational medicine, 15(1), szaf075.
https://doi.org/10.1093/stcltm/szaf075
Source: Stem Cells Translational Medicine
