Intestinal stroma guides monocyte differentiation to macrophages through GM-CSF.

Stromal cells support epithelial cell and immune cell homeostasis and play an important role in inflammatory bowel disease (IBD) pathogenesis. Here, we quantify the stromal response to inflammation in pediatric IBD and reveal subset-specific inflammatory responses across colon segments and intestinal layers. Using data from a murine dynamic gut injury model and human ex vivo transcriptomic, protein and spatial analyses, we report that PDGFRA+CD142-/low fibroblasts and monocytes/macrophages co-localize in the intestine. In primary human fibroblast-monocyte co-cultures, intestinal PDGFRA+CD142-/low fibroblasts foster monocyte transition to CCR2+CD206+ macrophages through granulocyte-macrophage colony-stimulating factor (GM-CSF). Monocyte-derived CCR2+CD206+ cells from co-cultures have a phenotype similar to intestinal CCR2+CD206+ macrophages from newly diagnosed pediatric IBD patients, with high levels of PD-L1 and low levels of GM-CSF receptor. The study describes subset-specific changes in stromal responses to inflammation and suggests that the intestinal stroma guides intestinal macrophage differentiation.

Notch-dependent cooperativity between myeloid lineages promotes Langerhans cell histiocytosis pathology.

Langerhans cell histiocytosis (LCH) is a potentially fatal neoplasm characterized by the aberrant differentiation of mononuclear phagocytes, driven by mitogen-activated protein kinase (MAPK) pathway activation. LCH cells may trigger destructive pathology yet remain in a precarious state finely balanced between apoptosis and survival, supported by a unique inflammatory milieu. The interactions that maintain this state are not well known and may offer targets for intervention. Here, we used single-cell RNA-seq and protein analysis to dissect LCH lesions, assessing LCH cell heterogeneity and comparing LCH cells with normal mononuclear phagocytes within lesions. We found LCH discriminatory signatures pointing to senescence and escape from tumor immune surveillance. We also uncovered two major lineages of LCH with DC2- and DC3/monocyte-like phenotypes and validated them in multiple pathological tissue sites by high-content imaging. Receptor-ligand analyses and lineage tracing in vitro revealed Notch-dependent cooperativity between DC2 and DC3/monocyte lineages during expression of the pathognomonic LCH program. Our results present a convergent dual origin model of LCH with MAPK pathway activation occurring before fate commitment to DC2 and DC3/monocyte lineages and Notch-dependent cooperativity between lineages driving the development of LCH cells.

Safety and Potential Efficacy of Escalating Dose of Ustekinumab in Pediatric Crohn Disease (the Speed-up Study): A Multicenter Study from the Pediatric IBD Porto Group of ESPGHAN.

OBJECTIVES: Escalation of the ustekinumab (UST) maintenance dosage was effective in adults with Crohn disease (CD), but no data are available for children. We evaluated the effectiveness and safety of dose escalation of UST in pediatric CD. METHODS: This was a retrospective multicenter study from 25 centers affiliated with the IBD Interest and Porto groups of ESPGHAN. We included children with CD who initiated UST at a standard dosing and underwent either dose escalation to intervals shorter than 8 weeks or re-induction of UST due to active disease. Demographic, clinical, laboratory, endoscopic, imaging, and safety data were collected up to 12 months of follow-up. RESULTS: Sixty-nine children were included (median age 15.8 years, interquartile range 13.8-16.9) with median disease duration of 4.3 years (2.9-6.3). Most children were biologic (98.6%)- and immunomodulator (86.8%)- experienced. Clinical response and remission were observed at 3 months after UST escalation in 46 (67%) and 29 (42%) children, respectively. The strongest predictor for clinical remission was lower weighted Pediatric Crohn Disease Activity Index (wPCDAI) at escalation ( P = 0.001). The median C-reactive protein level decreased from 14 (3-28.03) to 5 (1.1-20.5) mg/L ( P = 0.012), and the fecal calprotectin level from 1100 (500-2300) to 515 (250-1469) µg/g ( P = 0.012) 3 months post-escalation. Endoscopic and transmural healing were achieved in 3 of 19 (16%) and 2 of 15 (13%) patients, respectively. Thirteen patients (18.8%) discontinued therapy due to active disease. No serious adverse events were reported. CONCLUSIONS: Two-thirds of children with active CD responded to dose escalation of UST. Milder disease activity may predict a favorable outcome following UST dose escalation.

Identification of Childhood-Onset Inflammatory Bowel Disease in Swedish Healthcare Registers: A Validation Study.

Purpose: The Swedish National Patient Register (NPR) is often used in observational studies of childhood-onset inflammatory bowel disease (IBD) (<18 years of age) and its subtypes, but the validity of previously used register-based algorithms for capturing childhood-onset IBD has never been examined. Methods: We identified a random sample of 233 individuals with at least two first ever diagnostic listings of IBD in the NPR between 2002 and 2014. We calculated the test characteristics for different register-based definitions of IBD and its subtypes using the Copenhagen criteria and the revised Porto criteria as gold standard, both based on medical chart review. We made assumptions of the occurrence of undiagnosed IBD in the general child population based on available literature. Results: Out of 233 individuals with at least two diagnostic listings of IBD, 216 had true IBD, resulting in a positive predictive value (PPV) = 93% (95% confidence interval (CI) 89-96), sensitivity = 88% (95% CI 83-92), specificity = 100% (95% CI 100-100), and negative predictive value (NPV) = 100% (95% CI 100-100). The PPV for the NPR-based definitions of IBD subtypes at time of first IBD diagnosis and at end of follow-up were 78% (95% CI 69-86) and 88% (95% CI 80-94), respectively, for Crohn's disease and 74% (95% CI 63-83) and 71% (95% CI 60-80), respectively, for ulcerative colitis. Conclusion: The validity of register-based definitions of childhood-onset IBD in the Swedish NPR is high and can be used to identify patients in observational research.

Patients with both Langerhans cell histiocytosis and Crohn's disease highlight a common role of interleukin-23.

AIM: To present the first case series of patients with Langerhans cell histiocytosis (LCH) also affected by Crohn's disease (CD), both of which are granulomatous diseases, and in LCH investigate the role of interleukin (IL)-23, which is a well-described disease mediator in CD. METHODS: A case series of three patients with LCH and CD were described; a cohort of LCH patients (n = 55) as well as controls (n = 55) were analysed for circulating IL-23 levels; and the relation between the percentage of LCH cells in lesions and circulating IL-23 levels was analysed in seven LCH patients. RESULTS: Differential diagnostic challenges for these two granulomatous diseases were highlighted in the case series, and it took up to 3 years to diagnose CD. Elevated IL-23 levels were found in LCH patients. The amount of lesional LCH cells correlated with the levels of circulating IL-23. CONCLUSION: Both CD and LCH should be considered in patients with inflammatory gastrointestinal involvement. The IL-23 pathway is a common immunological trait between these two granulomatous diseases.

Adult height in patients with childhood-onset inflammatory bowel disease: a nationwide population-based cohort study.

BACKGROUND: Growth retardation is well described in childhood-onset inflammatory bowel disease (IBD). AIMS: To study if childhood-onset IBD is associated with reduced final adult height. METHODS: We identified 4201 individuals diagnosed with childhood-onset IBD 1990-2014 (Crohn's disease: n = 1640; ulcerative colitis: n = 2201 and IBD-unclassified = 360) in the Swedish National Patient Register. RESULTS: Patients with IBD attained a lower adult height compared to reference individuals (adjusted mean height difference [AMHD] -0.9 cm [95% CI -1.1 to -0.7]) and to their healthy siblings (AMHD -0.8 cm [-1.0 to -0.6]). Patients with Crohn's disease (CD) were slightly shorter than patients with ulcerative colitis (UC; -1.3 cm vs -0.6 cm). Lower adult height was more often seen in patients with pre-pubertal disease onset (AMHD -1.6 cm [-2.0 to -1.2]), and in patients with a more severe disease course (AMHD -1.9 cm, [-2.4 to -1.4]). Some 5.0% of CD and 4.3% of UC patients were classified as growth retarded vs 2.5% of matched reference individuals (OR 2.42 [95% CI 1.85-3.17] and 1.74 [1.36-2.22] respectively). CONCLUSION: Patients with childhood-onset IBD on average attain a slightly lower adult height than their healthy peers. Adult height was more reduced in patients with pre-pubertal onset of disease and in those with a more severe disease course.

Effects of Childhood-onset Inflammatory Bowel Disease on School Performance: A Nationwide Population-based Cohort Study Using Swedish Health and Educational Registers.

BACKGROUND: Childhood-onset inflammatory bowel disease (IBD) might negatively impact academic school performance. We conducted a nationwide study to examine the association between childhood-onset IBD and school results. METHODS: Our study population was selected from Swedish health registers. In the National Patient Register (1990 to 2013), we identified 2827 children with IBD: Crohn's disease (CD), n = 1207, and ulcerative colitis (UC), n = 1370. Patients were matched with 10 reference individuals by age, sex, birth year, and place of residence (n = 28,235). Final compulsory school grades (0 to 320 grade points) and qualification for high school (yes or no) were obtained through the National School Register. Regression models controlling for socioeconomic factors were used to analyze the association of IBD with school performance. RESULTS: Children with IBD had a lower final grade point average (adjusted mean grade difference [AMGD] -4.9, 95% confidence interval [CI] -7.1 to -2.6) but not a significantly higher risk to not qualify for high school (odds ratio [OR] 1.14, CI 0.99-1.31). The results were similar in children with UC (AMGD -5.5, CI -8.7 to -2.3) and CD (AMGD -4.7, CI -8.2 to -1.2). Underperformance was more common in subsets of IBD children characterized by markers associated with long-standing active disease (eg, >30 inpatient days [AMGD-18.1, CI -25.8 to -10.4]). CONCLUSION: Most children with IBD achieve comparable results in the final year of compulsory school as their healthy peers. Care should be improved for the subgroup of children for which IBD has a stronger negative impact on school performance.