Gastroesophageal Junction Fat Pad Tissue from Obese Patients Impairs Esophageal Epithelial Barrier Function and Disrupts Cell‐to‐Cell Connections

Abstract

Introduction Visceral obesity is associated with GERD and, traditionally, it has been assumed that visceral fat predisposes to GERD primarily by increasing intra-abdominal pressure. However, transmission electron microscopy (TEM) of esophageal biopsies from obese individuals without GERD exhibit dilated intercellular spaces (DIS) and, in earlier studies, we found that substances secreted by mature adipocytes in visceral fat from obese patients impair esophageal epithelial barrier function, induce DIS and reduce transepithelial resistance (TER). There is a fat pad at the gastroesophageal junction (GEJ) that is in intimate contact with the distal esophagus. We now explore whether whole GEJ fat tissue of obese individuals secretes substances that impair esophageal barrier function. Methods We obtained GEJ fat from 3 obese (BMI 46, 60, 74) and 3 non-obese (BMI 24, 26, 27) patients having foregut surgery. Human esophageal squamous cells were seeded into transwells and grown to confluence for 3 days. On day 4, cells were raised to an air-liquid interface (ALI) to allow for differentiation, stratification, and esophageal barrier formation. ALI cultures were exposed to conditioned media (CM) from GEJ fat or to control medium beginning at day 4. TER was measured on days 4, 6, and 8 using the EVOM2 Epithelial Volt/Ohm Meter. On day 8, ALI cultures were stained with H&E and Ki-67 and imaged; barrier permeability was assessed by a biotinylation reagent applied to the ALI surface. TEM of ALIs and of esophageal biopsies from 2 non-obese and 2 obese patients without GERD were assessed. Results CM from all 3 obese patients significantly reduced TER on days 6 and 8; CM from 2 non-obese patients did not reduce TER whereas CM from 1 non-obese patient induced a slight reduction in TER at day 8 (Table 1). Marked DIS were found only in ALI cultures grown with CM from obese patients. In ALIs grown with CM from non-obese patients, the biotinylation reagent stopped at the superficial layers of esophageal cells. In contrast, the biotinylation reagent diffused through all cell layers in ALIs grown with obese patient CM. Increases in basaloid cells and in Ki-67 were found in ALIs grown with obese patient CM. TEMs of ALIs grown with non-obese patient CM demonstrated well-oriented cell-cell junctions similar to TEMs of non-obese patient esophageal biopsies. In contrast, ALIs grown with obese patient CM demonstrated cell-cell junctional structures that were disorganized, aggregated, and floating within the DIS, similar in appearance to TEMs of the obese patients’ esophageal biopsies. Conclusion Substances produced by GEJ fat of obese patients impair esophageal epithelial barrier integrity, cause basal cell hyperplasia and DIS, and disrupt intercellular connections. These findings in ALI cultures recapitulate abnormalities seen by TEM in esophageal biopsies of obese patients.