T-Helper 2 Cytokines, Transforming Growth Factor β1, and Eosinophil Products Induce Fibrogenesis and Alter Muscle Motility in Patients With Eosinophilic Esophagitis

Abstract

BACKGROUND & AIMS Patients with eosinophilic esophagitis (EoE) often become dysphagic from the combination of organ fibrosis and motor abnormalities. We investigated mechanisms of dysphagia, assessing the response of human esophageal fibroblasts (HEF), muscle cells (HEMC), and esophageal muscle strips to eosinophil-derived products. METHODS Biopsies were collected via endoscopy from the upper, middle and lower thirds of the esophagus of 18 patients with EoE and 21 individuals undergoing endoscopy for other reasons (controls). Primary cultures of esophageal fibroblasts and muscle cells were derived from 12 freshly resected human esophagectomy specimens. Eosinophil distribution was investigated by histologic analyses of full-thickness esophageal tissue. Active secretion of EoE-related mediators was assessed from medium underlying mucosal biopsy cultures. We quantified production of fibronectin and collagen I by HEF and HEMC in response to eosinophil products. We also measured expression of ICAM1 and VCAM1 by, and adhesion of human eosinophils to, HEF and HEMC. Eosinophil products were tested in an esophageal muscle contraction assay. RESULTS Activated eosinophils were present in all esophageal layers. Significantly higher concentrations of eosinophil-related mediators were spontaneously secreted in mucosal biopsies from patients with EoE than controls. Exposure of HEF and HEMC to increasing concentrations of eosinophil products or co-culture with eosinophils caused HEF and HEMC to increase secretion of fibronectin and collagen I; this was inhibited by blocking transforming growth factor (TGF)β1 and p38 mitogen-activated protein kinase (MAKP) signaling. Eosinophil binding to HEF and HEMC increased following incubation of mesenchymal cells with eosinophil-derived products, and decreased following blockade of TGFβ1 and p38MAPK blockade. Eosinophil products reduced electrical field-induced contraction of esophageal muscle strips, but not acetylcholine-induced contraction. CONCLUSION In an analysis of tissues samples from patients with EoE, we linked the presence and activation state of eosinophils in EoE with altered fibrogenesis and motility of esophageal fibroblasts and muscle cells. This process might contribute to the development of dysphagia.

Isolation of Myofibroblasts from Mouse and Human Esophagus

“…Isolation and establishment of primary cultures via the methods outlined below generates stromal cells with a myofibroblast phenotype; α-SMA, vimentin positive, and weakly positive or negative for desmin, and cytokeratin negative. This phenotype is distinct from the phenotype of the esophageal fibroblast which is predominantly vimentin positive, α-SMA negative 3 or the α-SMA positive, vimentin negative phenotype of the muscularis mucosae…”

“…These methods provide investigators the ability to isolate and culture stromal cells from different clinical and experimental conditions, allowing comparisons between groups. Cultured myofibroblast-like stromal cells can also be potentially adapted for use in organotypic or co-culture models with other cells such as eosinophils 3 or in organotypic culture 8 .…”

“…These interactions have been best studied in the small intestine and colon and may similarly play a role in esophageal mucosal disorders 3 . A subpopulation of intestinal and colonic stromal cells termed myofibroblasts has been demonstrated to participate in mediating tissue injury, inflammation and repair 4,5 .…”

“…Our work in the murine esophagus has demonstrated α-SMA and vimentin cells in the esophageal stroma, occasionally subjacent to the squamous epithelium 6 . Epithelial-stromal interactions have been implicated in esophageal mucosal disorders such as gastro-esophageal mediated injury 6 and eosinophilic esophagitis 3 . Fibrotic strictures are also a known complication of esophageal injury and stromal cells have been implicated in the pathogenesis of gastrointestinal fibrosis.…”

Eosinophilic esophagitis: New insights in pathogenesis and therapy

“…Strictures are uncommon in children suggesting that over time the chronic infiltration with eosinophils leads to this complication in adults. This is particularly evident when there is a delay in the diagnosis that may lead to the remodeling of the esophagus and stricture formation [33] . In some cases, esophageal food impaction can be the initial presentation of the disease.…”