Gut microbial transcytosis induced by tumor necrosis factor-like 1A-dependent activation of a myosin light chain kinase splice variant contributes to IBD.

Inflammatory bowel disease (IBD) is characterized by abnormal host-microbe interactions. Proinflammatory cytokine IFNγ and a novel TNF superfamily member, TL1A, have been implicated in epithelial barrier dysfunction. The divergent regulatory mechanisms of transcellular versus paracellular hyperpermeability remain poorly understood. Intestinal epithelia express two splice variants of long myosin light chain kinase (MLCK), of which the full-length MLCK1 differ from the shorter isoform MLCK2 by a Src kinase phosphorylation site. The aim was to investigate the roles of MLCK splice variants in gut barrier defects under proinflammatory stress. Upregulated expression of TL1A, IFNγ, and two MLCK variants was observed in human IBD biopsy specimens. The presence of intraepithelial bacteria preceded tight junction (TJ) damage in dextran sodium sulfate-treated and TL1A-transgenic mouse models. Lack of barrier defects was observed in long MLCK(-/-) mice. TL1A induced MLCK-dependent terminal web (TW) contraction, brush border fanning, and transepithelial bacterial internalization. The bacterial taxa identified in the inflamed colonocytes included Escherichia, Enterococcus, Staphylococcus,and Lactobacillus. Recombinant TL1A and IFNγ at low doses induced PI3K/Akt/MLCK2-dependent bacterial endocytosis, whereas high-dose IFNγ caused TJ opening via the iNOS/Src/MLCK1 axis. Bacterial internalization was recapitulated in MLCK-knockout cells individually expressing MLCK2 but not MLCK1. Immunostaining showed different subcellular sites of phosphorylated MLC localized to the TJ and TW in the MLCK1- and MLCK2-expressing cells, respectively. In conclusion, proinflammatory cytokines induced bacterial influx through transcellular and paracellular routes via divergent pathways orchestrated by distinct MLCK isoforms. Bacterial transcytosis induced by TL1A may be an alternative route causing symptom flares in IBD.

Human Placenta-derived Cells (PDA-001) for the Treatment of Moderate-to-severe Crohn's Disease: A Phase 1b/2a Study.

BACKGROUND: PDA-001 (cenplacel-L), a preparation of placenta-derived mesenchymal-like adherent cells with immunomodulatory effects, previously demonstrated safety and tolerability in an open-label Crohn's disease (CD) study. The current phase 1b/2a study evaluated the safety and efficacy of PDA-001 in subjects with moderate-to-severe CD. METHODS: Subjects had active inflammation on colonoscopy or elevated fecal calprotectin and inadequate response to conventional therapy. Concomitant therapy with stable doses of immunomodulators and/or biologics was permitted. Subjects received 8 units of PDA-001 (1.5 × 10 cells per unit) in the phase 1b open-label study. In the phase 2a double-blind study, subjects were randomly assigned placebo, 1 unit, or 4 units of PDA-001 (2 infusions 1 wk apart). The primary endpoint was induction of clinical response (≥100 points and/or 25% decrease in Crohn's Disease Activity Index) at 4 and 6 weeks. RESULTS: Fifty subjects were enrolled (safety analysis, 50 subjects; efficacy analysis, 48 subjects). Four subjects received 8 units of PDA-001 (phase 1b study); 46 subjects were subsequently randomized to 1 or 4 units of PDA-001 or placebo (phase 2a study). The primary endpoint was achieved in 10/28 (36%) of PDA-001 subjects compared with placebo (0%, P = 0.026). Clinical remission was achieved in 4/28 (14%) of PDA-001 subjects compared with placebo (0%, P = 0.3). One treatment-related serious adverse event occurred (systemic hypersensitivity reaction at 8 units). In the phase 2a study, serious adverse events occurred in 9/28 (32%) of PDA-001 subjects and 1/16 (7%) of placebo subjects. CONCLUSIONS: A 2-infusion regimen of PDA-001 induced clinical response in subjects with moderate-to-severe CD. Additional studies are warranted.

The London Position Statement of the World Congress of Gastroenterology on Biological Therapy for IBD with the European Crohn's and Colitis Organization: when to start, when to stop, which drug to choose, and how to predict response?

The advent of biological therapy has revolutionized inflammatory bowel disease (IBD) care. Nonetheless, not all patients require biological therapy. Selection of patients depends on clinical characteristics, previous response to other medical therapy, and comorbid conditions. Availability, reimbursement guidelines, and patient preferences guide the choice of first-line biological therapy for luminal Crohn's disease (CD). Infliximab (IFX) has the most extensive clinical trial data, but other biological agents (adalimumab (ADA), certolizumab pegol (CZP), and natalizumab (NAT)) appear to have similar benefits in CD. Steroid-refractory, steroid-dependent, or complex fistulizing CD are indications for starting biological therapy, after surgical drainage of any sepsis. For fistulizing CD, the efficacy of IFX for inducing fistula closure is best documented. Unique risks of NAT account for its labeling as a second-line biological agent in some countries. Patients who respond to induction therapy benefit from systematic re-treatment. The combination of IFX with azathioprine is better than monotherapy for induction of remission and mucosal healing up to 1 year in patients who are naïve to both agents. Whether this applies to other agents remains unknown. IFX is also effective for treatment-refractory, moderate, or severely active ulcerative colitis. Patients who have a diminished or loss of response to anti-tumor necrosis factor (TNF) therapy may respond to dose adjustment of the same agent or switching to another agent. Careful consideration should be given to the reasons for loss of response. There are insufficient data to make recommendations on when to stop anti-TNF therapy. Preliminary evidence suggests that a substantial proportion of patients in clinical remission for >1 year, without signs of active inflammation can remain in remission after stopping treatment.