Therapeutic applications of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have attracted considerable attention because of their immunomodulatory properties against immune-mediated, inflammatory diseases. Here, we demonstrated enhanced immunomodulatory properties of EVs secreted from endoplasmic reticulum (ER) stress inducer thapsigargin (TSG)-primed human Wharton’s jelly-derived MSCs (WJ-MSCs). EVs from TSG-primed WJ-MSCs (TSG-EV) showed increased yield and expression of immunomodulatory factors, such as transforming growth factor-β1 (TGFβ), cyclooxygenase-2 (COX2), and especially indoleamine 2,3-dioxygenase (IDO), compared to control EVs. TSG-EV showed a significantly enhanced immunosuppressive effect on human peripheral blood-derived T cell proliferation and Th1 and Th17 differentiation, whereas Treg and M2-type macrophage were enriched compared to a control EV-treated group. Furthermore, TSG-EV substantially mitigated mouse experimental colitis by reducing the inflammatory response and maintaining intestinal barrier integrity. A significant increase of Tregs and M2-type macrophages in colitic colons of a TSG-EV-treated mouse suggests an anti-inflammatory effect of TSG-EV in colitis model, possibly mediated by Treg and macrophage polarization. These data indicate that TSG treatment promoted immunomodulatory properties of EVs from WJ-MSCs, and TSG-EV may provide a new therapeutic approach for treatment of colitis.

The therapeutic applications of mesenchymal stem cells (MSCs) have been actively explored due to their broad anti-inflammatory and immunomodulatory properties. However, the use of xenogeneic components, including fetal bovine serum (FBS), in the expansion media might pose a risk of xenoimmunization and zoonotic transmission to post-transplanted patients. Here, we extensively compared the physiological functions of human Wharton’s jelly-derived MSCs (WJ-MSCs) in a xeno-free medium (XF-MSCs) and a medium containing 10% FBS (10%-MSCs). Both groups showed similar proliferation potential; however, the 10%-MSCs showed prolonged expression of CD146, with higher colony-forming unit-fibroblast (CFU-F) ability than the XF-MSCs. The XF-MSCs showed enhanced adipogenic differentiation potential and sufficient hematopoietic stem cell (HSC) niche activity, with elevated niche-related markers including CXCL12. Furthermore, we demonstrated that the XF-MSCs had a significantly higher suppressive effect on human peripheral blood-derived T cell proliferation, Th1 and Th17 differentiation, as well as naïve macrophage polarization toward an M1 phenotype. Among the anti-inflammatory molecules, the production of indoleamine 2,3-dioxygenase (IDO) and nitric oxide synthase 2 (NOS2) was profoundly increased, whereas cyclooxygenase-2 (COX-2) was decreased in the XF-MSCs. Finally, the XF-MSCs had an enhanced therapeutic effect against mouse experimental colitis. These findings indicate that xeno-free culture conditions improved the immunomodulatory properties of WJ-MSCs and ex vivo-expanded XF-MSCs might be an effective strategy for preventing the progression of colitis.

Targeting the aryl hydrocarbon receptor (AhR) is an emerging therapeutic strategy for multiple diseases (e.g., inflammatory bowel disease). Thermosporothrix hazakensis microbial metabolite 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) is a putative AhR endogenous ligand. To improve the chemical stability, we synthesized a series of ITE chemical mimics. Using a series of in vitro assays, we identified 2-(1H-indole-3-carbonyl)-N-methyl thiazole-4-carboxamide (ITE-CONHCH3) as a highly potent (EC50 = 1.6 nM) AhR agonist with high affinity (K i = 88 nM). ITE-CONHCH3 triggered AhR nuclear translocation and dimerization of AhR-ARNT, enhanced AhR binding in the CYP1A1 promoter, and induced AhR-regulated genes in an AhR-dependent manner. The metabolic stability of ITE-CONHCH3 in a cell culture was 10 times higher than that of ITE. Finally, we observed protective effects of ITE-CONHCH3 in mice with DSS-induced colitis. Overall, we demonstrate and validate a concept of microbial metabolite mimicry in the therapeutic targeting of AhR.

Circadian dysfunction is closely associated with an increased risk of various diseases. Considering that molecular clock machinery serves as an intrinsic time-keeping system underlying the circadian rhythm of biological processes, the modulation of the molecular clock machinery is an attractive therapeutic target with novel mechanisms of action. Based on the previous structure–activity relationship study of small molecule cryptochrome (CRY) inhibitors possessing an ethoxypropanoic acid moiety, non-ethoxypropanoic acid-type inhibitors have been developed by bioisosteric replacement. They were evaluated as potent and effective enhancers of E-box-mediated transcription, and, in particular, ester 5d and its hydrolysis product 2d exhibited desirable metabolic and pharmacokinetic profiles as promising drug candidates. Compound 2d directly bound to both CRY1 and 2 in surface plasmon resonance analyses, suggesting that the molecular target is CRY. Effects of compound 5d and 2d on suppressive action of CRY1 on CLOCK:BMAL1-activated E-box-LUC reporter activity revealed that both compounds inhibited the negative feedback actions of CRY on CLOCK:BMAL1. Most importantly, compounds 5d and 2d exhibited significant effects on molecular circadian rhythmicity to be considered circadian clock-enhancers, distinct from the previously developed CRY inhibitors possessing an ethoxypropanoic acid moiety.

Background and Objectives: Epidemiological investigations have shown positive correlations between increased diesel exhaust particles (DEP) in ambient air and adverse health outcomes. DEP are the major constituent of particulate atmospheric pollution and have been shown to induce proinflammatory responses both in the lung and systemically. Here, we report the effects of DEP exposure on the properties of human Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs), including stemness, regeneration, and immunomodulation. Methods and Results: Non-apoptotic concentrations of DEP (10 μg/ml) inhibited the migration and osteogenic differentiation capacity of WJ-MSCs. Gene expression profiling showed that DEP increased intracellular reactive oxygen species (ROS) and expression of pro-inflammatory and metabolic-process-related genes including cFos. Furthermore, WJ-MSCs cultured with DEP showed impaired suppression of T cell proliferation that was reversed by inhibition of ROS or knockdown of cFos. ERK inhibition assay revealed that DEP-induced ROS regulated cFos through activation of ERK but not NF-κB signaling. Overall, low concentrations of DEP (10 μg/ml) significantly suppressed the stemness and immunomodulatory properties of WJ-MSCs through ROS/ERK/cFos signaling pathways. Furthermore, WJ-MSCs cultured with DEP impaired the therapeutic effect of WJ-MSCs in experimental colitis mice, but was partly reversed by inhibition of ROS. Conclusions: Taken together, these results indicate that exposure to DEP enhances the expression of pro-inflammatory cytokines and immune responses through a mechanism involving the ROS/ERK/cFos pathway in WJ-MSCs, and that DEP-induced ROS damage impairs the therapeutic effect of WJ-MSCs in colitis. Our results suggest that modulation of ROS/ERK/cFos signaling pathways in WJ-MSCs might be a novel therapeutic strategy for DEP-induced diseases.