Expression of endothelial protein C receptor and thrombomodulin in the intestinal tissue of patients with inflammatory bowel disease

Objective: Inflammatory bowel diseases are characterized by disorders of immunity, thrombosis of large vessels, and microthrombosis of mucosal vessels. The expression of endothelial protein C receptor (EPCR) and thrombomodulin-two receptors of the protein C pathway involved in thrombin scavenging and inflammation-was studied in intestinal resection specimens or mucosal biopsies from patients with inflammatory bowel disease and from controls. The soluble forms of the receptors in plasma were measured. Data Source. This study involved patients from two large university hospitals. After surgery or biopsy, tissue samples were either frozen or fixed in formalin and embedded in paraffin. Sections for immunohistochemistry examination were cut and tested with the specific antibodies to EPCR and thrombomodulin. RNA was extracted from frozen tissue for amplification via reverse-transcriptase polymerase chain reaction. Normal intestinal and diverticulitis tissue was used as a control. Resection samples from 36 patients with ulcerative colitis, 38 with Crohn's disease, 38 with colonic cancer, and 32 with diverticulitis were studied by immunohistochemistry, and frozen sections from the same patients were studied by immunofluorescence. Twelve biopsy specimens of adjacent intestinal areas from six patients with inflammatory bowel disease were included in the study for reverse-transcriptase polymerase chain reaction. Soluble receptors were measured in the plasma of 52 inflammatory bowel disease patients and 52 controls. Data Summary: EPCR and thrombomodulin were expressed on the mucosal endothelium of controls, and the intensity of the signal decreased in inflammatory bowel disease patients. EPCR was expressed by dendritic-like cells in controls, which also stained positive for CD21. The EPCR+/CD21(+) dendritic-like cells were not as commonly observed in sections from ulcerative colitis patients as they were in sections from control patients (12.0 +/- 3.6 cells per high-power field vs. 23.8 +/- 10.4 cells per high-power field, p =.03), and this decrease was less evident in sections from Crohn's disease patients. Levels of messenger RNA for EPCR paralleled protein expression. Soluble thrombomodulin and EPCR levels were both higher in patients than in controls: 41.5 vs. 26.0 ng/mL (p < .0001) and 141 vs. 130 ng/mL (p < .05), respectively. Conclusions. EPCR expression on dendritic-like cells that bear the key complement receptor CD21 suggests a role for EPCR in innate immunity. The reduced expression of thrombomodulin and EPCR in the mucosal vessels in inflammatory bowel disease impairs protein C activation, favoring microthrombosis.