Bowel stiffness associated with histopathologic scoring of stenosis in patients with Crohn's disease

Intestinal ultrasound in Crohn’s disease: A systematic review of its role in diagnosis, monitoring, and treatment response

BACKGROUND

Intestinal ultrasound (IUS) has gained prominence as a safe, non-invasive imaging technique for managing Crohn’s disease (CD), offering real-time evaluation without radiation exposure.

AIM

To systematically review the role of IUS in diagnosing, monitoring disease progression, assessing treatment response, and managing complications in CD.

METHODS

A literature search of PubMed and Embase databases was conducted, identifying 207 original research articles published between 1953 and June 2024. The review focused on diagnostic accuracy, disease monitoring, therapeutic utility, and advancements in IUS applications.

RESULTS

IUS has shown high diagnostic accuracy for detecting inflammation, particularly in the ileum and colon, with limitations in jejunal and rectal regions. It is effective in assessing disease activity using parameters like bowel wall thickness (BWT) and vascularity and correlates well with endoscopy and magnetic resonance enterography. IUS can predict early response to biologics, with reductions in BWT serving as an important marker. In known CD, IUS influences clinical decisions during remission, flares, and therapy evaluations. It reliably detects strictures, fistulas, and therapy-related complications. Small intestinal contrast ultrasound (SICUS) can improve the detection of strictures particularly proximal ones. Techniques such as CE-IUS and elastography enhance stricture characterization but require further validation. IUS is also useful in special scenarios like perianal fistulas, pregnancy, post-operative CD, and guiding endoscopic therapy.

CONCLUSION

IUS is a patient-friendly, cost-effective imaging tool that significantly impacts CD management across various stages. Its integration into clinical practice supports early diagnosis, disease monitoring, and therapeutic adjustments. Further studies are warranted to refine advanced techniques and standardize its application for broader use.

Advancements and Challenges in Modeling Mechanobiology in Intestinal Host-Microbiota Interaction

The gastrointestinal tract is a dynamic biomechanical environment where physical forces, cellular processes, and microbial interactions converge to shape the gut health and disease. In this review, we examine the unique mechanical properties of the gut, including peristalsis, viscoelasticity, shear stress, and tissue stiffness, and their roles in modulating host mechanosignaling and microbial behavior under physiological and pathological conditions. We discuss how these mechanical forces regulate gut epithelial integrity, immune responses, and microbial colonization, leading to distinct ecological niches across different intestinal segments. Furthermore, we highlight recent advancements in 3D culture systems and gut-on-a-chip models that accurately recapitulate the complex interplay between biomechanics and gut microbiota. By elucidating the intricate relationship between mechanobiology and gut function, this review underscores the potential for mechanotherapeutic strategies to modulate host-microbe interactions, offering promising avenues for the prevention and treatment of disorders such as inflammatory bowel disease, irritable bowel syndrome, and colorectal cancer.

Circulating and Magnetic Resonance Imaging Biomarkers of Intestinal Fibrosis in Small Bowel Crohn's Disease

BACKGROUND

We previously identified circulating and MRI biomarkers associated with the surgical management of Crohn's disease (CD). Here we tested associations between these biomarkers and ileal resection inflammation and collagen content.

METHODS

Fifty CD patients undergoing ileal resection were prospectively enrolled at 4 centers. Circulating CD64, extracellular matrix protein 1 (ECM1), GM-CSF autoantibodies (GM-CSF Ab), and fecal calprotectin were measured by ELISA. Ileal 3-dimensional magnetization transfer ratio (3D MTR), modified Look-Locker inversion recovery (MOLLI) T1 relaxation, diffusion-weighted intravoxel incoherent motion (IVIM), and the simplified magnetic resonance index of activity (sMaRIA) were measured by MRI. Ileal resection specimen acute inflammation was graded, and collagen content was measured quantitatively using second harmonic imaging microscopy. Associations between biomarkers and ileal collagen content were tested.

RESULTS

Median (interquartile range [IQR]) age was 19.5 (16-33) years. We observed an inverse relationship between ileal acute inflammation and collagen content (r = -0.39 [95% confidence interval {CI}: -0.61, -0.10], P = .008). Most patients (33 [66%]) received biologics, with no variation in collagen content with treatment exposures. In the univariate analysis, CD64, GM-CSF Ab, fecal calprotectin, and sMaRIA were positively associated with acute inflammation and negatively associated with collagen content (P < .1). The multivariable model for ileal collagen content (R2 = 0.31 [95% CI: 0.11, 0.52]) included log CD64 (β = -.27; P = .19), log ECM1 (β = .47; P = .06), log GM-CSF Ab (β = -.15; P = .01), IVIM f (β = .29, P = .10), and IVIM D* (β = 1.69, P = .13).

CONCLUSIONS

Clinically available and exploratory circulating and MRI biomarkers are associated with the degree of inflammation versus fibrosis in CD ileal resections. With further validation, these biomarkers may be used to guide medical and surgical decision-making for refractory CD.

Piezo1-specific Deletion in Macrophage Protects the Progression of Chronic Inflammatory Bowel Disease in Mice

BACKGROUND & AIMS

Piezo1, a recently identified mechanically activated nonselective cation channel protein, demonstrates sensitivity to various mechanical stimuli, such as matrix stiffness and shear stress. Although accumulating evidence implicates Piezo1 channels in numerous physiologic and pathophysiologic processes, its involvement in dextran sulfate sodium (DSS)-induced acute and chronic inflammatory bowel disease (IBD) remains incompletely understood. This study aimed to investigate the effect of Piezo1 channels in macrophage polarization and its associated functions in IBD.

METHODS

DSS-induced inflammatory bowel disease model was established in Piezo1td/Tdt or Piezo1fl/fl and Piezo1△LysM male mice. Additionally, bone marrow-derived macrophages from Piezo1fl/fl and Piezo1△LysM male mice were isolated to elucidate the downstream targets of Piezo1 and the associated underlying molecular mechanisms.

RESULTS

Our findings revealed that Piezo1 deficiency in macrophages could protect mice from DSS-induced chronic IBD, as evidenced by improved colon length and the preservation of colon structure. The mitigation of inflammation during chronic IBD progression was observed with Piezo1 deficiency in macrophages, characterized by reduced macrophage accumulation, M1 macrophage polarization, T helper 1 infiltration, and decreased inflammatory cytokine secretion. Further investigations unveiled that Piezo1-deficient macrophages inhibit the expression and activity of Nod-like receptor protein 3 and nuclear factor kappa B in colon tissues and bone marrow-derived macrophages while regulating the nuclear translocation of p65. Conversely, macrophage Piezo1 activation enhanced inflammatory cytokine secretion by activating Nod-like receptor protein 3/nuclear factor kappa B pathways.

CONCLUSIONS

Myeloid Piezo1 mediates colonic immune response, and disrupting Piezo1 inhibits the progression of chronic IBD. This study provides hitherto undocumented evidence of the pivotal role of macrophage Piezo1 channels in regulating the progression of chronic IBD. Targeting macrophage Piezo1 may offer a promising therapeutic strategy against chronic IBD.

Curcumin-loaded polysaccharide microparticles alleviated DSS-induced ulcerative colitis by improving intestinal microecology and regulating MAPK/NF-κB/Nrf2/NLRP3 pathways

Curcumin (Cur) exerts many benefits on the host, but its application is limited by its poor bioavailability. In this study, composite polysaccharide microparticles loading Cur (Cur-CPM) was prepared by food-grade materials and gel technology. Its properties were analyzed via the in vitro and in vivo models, and then its benefit on gut health was assessed in DSS-treated mice. Compared to free Cur, CPM extended the residence time and absorption efficiency of Cur in the intestine, effectively ameliorating the symptoms of colitis. Cur-CPM alleviated colonic inflammation by inhibiting the activation of the MAPK and NF-κB pathways and suppressing NLRP3 inflammasome activity, affecting the expression of inflammation-related cytokines and mediators. In addition, Cur-CPM regulated the levels of antioxidants and oxidants in the colon tissues via Nrf2 activation, alleviating oxidative stress. Cur-CPM protected gut barrier function by maintaining the integrity of colonic mucosal layer and tight junction. The underlying mechanism can be attributed not only to the anti-inflammatory and antioxidant activities of Cur but also to modulation of Cur and CPM on the gut microbiota and metabolites. It suggests that Cur-CPM holds the potential to be developed as a functional component to enhance gut health.

Resistance to apoptosis in complicated Crohn's disease: Relevance in ileal fibrosis

BACKGROUND AND AIMS

The stiffening of the extracellular matrix, and changes in its cellular and molecular composition, have been reported in the pathogenesis of fibrosis. We analyze the mechanisms that perpetuate ileal fibrosis in surgical resections of complicated Crohn's disease patients.

METHODS

Ileal resections were obtained from affected and non-affected tissue of stenotic or penetrating Crohn's disease behavior. Ilea from non-IBD patients were used as control tissue. All samples underwent RNA sequencing. Human small intestinal fibroblasts were treated for 48 h with IL-1β, TFGβ1, PDGFB or TNF-α. Resistance to apoptosis was analysed by RT-PCR, western blot and immunohistochemistry in ileal tissue and by RT-PCR and FACS in cultured cells.

RESULTS

Growth factor-driven signaling pathways and increased RAS GTPase activity were up-regulated in affected ilea in which we found expression of both the antiapoptotic molecule MCL1 and the transcription factor ETS1 in submucosal fibroblasts, and a senescence-associated secretory phenotype. In cultured intestinal fibroblasts, PDGFB induced an ETS1-mediated resistance to apoptosis that was associated with the induction of both of TGFB1 and IL1B, a cytokine that replicated the expression of SASP detected in ileal tissue. ETS1 drove fibroblast polarization between inflammatory and fibrogenic phenotypes in IL1β-treated cells.

CONCLUSIONS

Our data show resistance to apoptosis in complicated ileal CD, and demonstrate that PDGFB induce an ETS1-mediated resistance to apoptosis associated with an inflammatory and fibrogenic pattern of expression in intestinal fibroblasts. Results point to PDGFRB, IL1R1 or MCL1 as potential targets against ileal fibrosis.

Ultrasound in Pediatric Inflammatory Bowel Disease-A Review of the State of the Art and Future Perspectives

Inflammatory bowel disease (IBD) comprises a group of relapsing, chronic diseases of the gastrointestinal tract that, in addition to adults, can affect children and adolescents. To detect relapses of inflammation, these patients require close observation, frequent follow-up, and therapeutic adjustments. While reference standard diagnostics include anamnestic factors, laboratory and stool sample assessment, performing specific imaging in children and adolescents is much more challenging than in adults. Endoscopic and classic cross-sectional imaging modalities may be invasive and often require sedation for younger patients. For this reason, intestinal ultrasound (IUS) is becoming increasingly important for the non-invasive assessment of the intestine and its inflammatory affection. In this review, we would like to shed light on the current state of the art and provide an outlook on developments in this field that could potentially spare these patients more invasive follow-up procedures.

Inhibition of Piezo1 Ameliorates Intestinal Inflammation and Limits the Activation of Group 3 Innate Lymphoid Cells in Experimental Colitis

Piezo1, the mechanosensory ion channel, has attracted increasing attention for its essential roles in various inflammatory responses and immune-related diseases. Although most of the key immune cells in inflammatory bowel disease (IBD) have been reported to be regulated by Piezo1, the specific role of Piezo1 in colitis has yet to be intensively studied. The present study investigated the impact of pharmacological inhibition of Piezo1 on dextran sulfate sodium (DSS)-induced colitis and explored the role of Piezo1 in intestinal immune cells in the context of colitis. We observed upregulated expression of Piezo1 in the colon tissue of mice with DSS-induced colitis. Pharmacological inhibition of Piezo1 by GsMTx4 diminished the severity of colitis. Piezo1 inhibition downregulated the expression of pro-inflammatory mediators Il1b, Il6, and Ptgs2 in colonic tissue and suppressed the production of IL-6 from macrophages and dendritic cells without altering the balance of T helper (Th) cells. In particular, Piezo1 did not affect cell viability but regulated cell proliferation and production of IL-17A in group 3 innate lymphoid cells (ILC3s), which is dependent on the PI3K-Akt-mTOR signaling pathway. Our findings uncover Piezo1 as an effective regulator of gut inflammation. Targeting Piezo1 could be a promising strategy to modulate intestinal immunity in IBD.

Intestinal Ultrasound for Differentiating Fibrotic or Inflammatory Stenosis in Crohn's Disease: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

Intestinal ultrasound [IUS] has been increasingly reported to distinguish inflammatory or fibrotic intestinal stenosis in Crohn's disease [CD] patients. However, the diagnostic value is unclear. This systematic review and meta-analysis aimed to assess the diagnostic role of different modes of IUS parameters.

METHODS

We searched PubMed, Embase, Web of Science, and Cochrane Library from inception to August 2021. Regarding effect sizes, weighted mean differences [WMDs] or standardised mean differences [SMDs] were used. We pooled data using a random-effects or fixed-effects model according to heterogeneity. The diagnostic accuracy of IUS for distinguishing fibrosis was pooled.

RESULTS

A total of 19 studies were retained for qualitative analysis, and 14 were included in the meta-analysis [with 511 total subjects and 635 bowel segments]. In patients with fibrotic stenosis, the pooled WMDs for bowel wall thickness were 1.30 mm (95% confidence interval [CI]: 0.69-1.91) thicker than in patients with inflammatory stenosis, and the pooled SMDs for strain value and strain ratio were 0.80 [95% CI: 0.41-1.20] and 1.08 [95% CI: 0.55-1.60] harder than in patients with inflammatory stenosis, respectively. The percentage of maximal enhancement of fibrotic stenosis was lower than that of inflammatory stenosis [WMD -10.03; 95% CI: -17.91- -2.16]. The diagnostic accuracy of IUS was not performed because only a few studies provided relevant diagnostic indicators, and these studies used different modes and parameters.

CONCLUSIONS

IUS currently is inaccurate to differentiate fibrotic or inflammatory stenosis in CD patients, and more studies assessing the significance of each parameter and its cut-off value in different modes of IUS are needed to be conducted in the future.

Ion channel Piezo1 activation promotes aerobic glycolysis in macrophages

Altered microenvironmental stiffness is a hallmark of inflammation. It is sensed by the mechanically activated cation channel Piezo1 in macrophages to induce subsequent immune responses. However, the mechanism by which the mechanosensitive signals shape the metabolic status of macrophages and tune immune responses remains unclear. We revealed that Piezo1-deficient macrophages exhibit reduced aerobic glycolysis in resting or liposaccharide (LPS)-stimulated macrophages with impaired LPS-induced secretion of inflammatory cytokines in vitro. Additionally, pretreatment with the Piezo1 agonist, Yoda1, or cyclical hydrostatic pressure (CHP) upregulated glycolytic activity and enhanced LPS-induced secretion of inflammatory cytokines. Piezo1-deficient mice were less susceptible to dextran sulfate sodium (DSS)-induced colitis, whereas Yoda1 treatment aggravated colitis. Mechanistically, we found that Piezo1 activation promotes aerobic glycolysis through the Ca²⁺-induced CaMKII-HIF1α axis. Therefore, our study revealed that Piezo1-mediated mechanosensitive signals Piezo1 can enhance aerobic glycolysis and promote the LPS-induced immune response in macrophages.

Mechanoscopy: A Novel Device and Procedure for in vivo Detection of Chronic Colitis in Mice

BACKGROUND

Gut stiffening caused by fibrosis plays a critical role in the progression of inflammatory bowel disease (IBD) and colon cancer. Previous studies have characterized the biomechanical response of healthy and pathological gut, with most measurements obtained ex vivo.

METHODS

Here, we developed a device and accompanying procedure for in vivo quantification of gut stiffness, termed mechanoscopy. Mechanoscopy includes a flexible balloon catheter, pressure sensor, syringe pump, and control system. The control system activates the balloon catheter and performs automated measurements of the gut stress-strain biomechanical response.

RESULTS

A gut stiffness index (GSI) is identified based on the slope of the obtained stress-strain response. Using a colitis mouse model, we demonstrated that GSI positively correlates with the extent of gut fibrosis, the severity of mucosal damage, and the infiltration of immune cells. Furthermore, a critical strain value is suggested, and GSI efficiently detects pathological gut fibrotic stiffening when the strain exceeds this value.

CONCLUSIONS

Based on these results, we envision that mechanoscopy and GSI will facilitate the clinical diagnosis of IBD.

Intestinal strictures in Crohn's disease: a 2021 update

Intestinal strictures remain one of the most intractable and common complications of Crohn's disease (CD). Approximately 70% of CD patients will develop fibrotic strictures after 10 years of CD diagnosis. Since specific antifibrotic therapies are unavailable, endoscopic balloon dilation and surgery remain the mainstay treatments despite a high recurrence rate. Besides, there are no reliable methods for accurately evaluating intestinal fibrosis. This is largely due to the fact that the mechanisms of initiation and propagation of intestinal fibrosis are poorly understood. There is growing evidence implying that the pathogenesis of stricturing CD involves the intricate interplay of factors including aberrant immune and nonimmune responses, host-microbiome dysbiosis, and genetic susceptibility. Currently, the progress on intestinal strictures has been fueled by the advent of novel techniques, such as single-cell sequencing, multi-omics, and artificial intelligence. Here, we perform a timely and comprehensive review of the substantial advances in intestinal strictures in 2021, aiming to provide prompt information regarding fibrosis and set the stage for the improvement of diagnosis, treatment, and prognosis of intestinal strictures.

Biomechanical Properties of Strictures in Crohn’s Disease: Can Dynamic Contrast-Enhanced Ultrasonography and Magnetic Resonance Enterography Predict Stiffness?

Strictures and abdominal pain often complicate Crohn’s disease (CD). The primary aim was to explore whether parameters obtained by preoperative contrast-enhanced (CE) ultrasonography (US) and dynamic CE MR Enterography (DCE-MRE) of strictures associates with biomechanical properties. CD patients undergoing elective small intestinal surgery were preoperatively examined with DCE-MRE and CEUS. The excised intestine was distended utilizing a pressure bag. Luminal and outer bowel wall cross-sectional areas were measured with US. The circumferential stricture stiffness (Young’s modulus E) was computed. Stiffness was associated with the initial slope of enhancement on DCE-MRE (ρ = 0.63, p = 0.007), reflecting active disease, but lacked association with CEUS parameters. For structural imaging parameters, inflammation and stricture stiffness were associated with prestenotic dilatation on US (τ_b = 0.43, p = 0.02) but not with MRE (τ_b = 0.01, p = 1.0). Strictures identified by US were stiffer, 16.8 (14.0–20.1) kPa, than those graded as no or uncertain strictures, 12.6 (10.5–15.1) kPa, p = 0.02. MRE global score (activity) was associated with E (ρ = 0.55, p = 0.018). Elastography did not correlate with circumferential stiffness. We conclude that increasing activity defined by the initial slope of enhancement on DCE-MRE and MRE global score were associated with stricture stiffness. Prestenotic dilatation on US could be a potential biomarker of CD small intestinal stricture stiffness.