Epithelial restitution and wound healing in inflammatory bowel disease

Abstract

disorders including inflammatory bowel diseases and require constant repair of the epithelium. Enhancement of intestinal repair mechanisms by regulatory peptides or other modulatory factors may provide future approaches for the treatment of diseases that are characterized by injuries of the epithelial surface. THE MUCOSAL DEFENSE SYSTEMThe surface of the digestive tract is covered by epithelial cells that constitute an efficient physical barrier between the dietary and enteric flora pathogens found in the intestinal lumen and the individuum, but also allows an exchange between nutrients and the systemic circulation [1] . The epithelial defense mechanism can be categorized into three key components: pre-epithelial, epithelial and post-epithelial, the latter is represented by the lamina propria [2] . The pre-epithelial mucus barrier is composed of mucin associated with other proteins and lipids and forms a continuous gel into which a bicarbonate-rich fluid is secreted, maintaining a neutralizing pH at the epithelial surface. Phosphatidylcholine is the predominant surface bioactive phospholipid found within the gastrointestinal tract [3] . Intestinal epithelial cells secrete mucins and glycocalyx, which contain membrane-anchored negatively charged mucin-like glycoproteins and hydrophobic phospholipids [4] . The tight adherence of mucin to the apical surfaces of epithelia is owed to the existence of the specific complex between mucin oligosaccharides and the mucin binding protein of the apical mucosal membrane [5] . AbstractInflammatory bowel disease is characterized by a chronic inflammation of the intestinal mucosa. The mucosal epithelium of the alimentary tract constitutes a key element of the mucosal barrier to a broad spectrum of deleterious substances present within the intestinal lumen including bacterial microorganisms, various dietary factors, gastrointestinal secretory products and drugs. In addition, this mucosal barrier can be disturbed in the course of various intestinal disorders including inflammatory bowel diseases. Fortunately, the integrity of the gastrointestinal surface epithelium is rapidly reestablished even after extensive destruction. Rapid resealing of the epithelial barrier following injuries is accomplished by a process termed epithelial restitution, followed by more delayed mechanisms of epithelial wound healing including increased epithelial cell proliferation and epithelial cell differentiation. Restitution of the intestinal surface epithelium is modulated by a range of highly divergent factors among them a broad spectrum of structurally distinct regulatory peptides, variously described as growth factors or cytokines. S e ve ra l re g u l a t or y pe pt ide fac t or s ac t from t he basolateral site of the epithelial surface and enhance epithelial cell restitution through TGF-β-dependent pathways. In contrast, members of the trefoil factor family (TFF peptides) appear to stimulate epithelial restitution in conjunction with mucin glycoproteins through a TGF-β-independent mechanism from...

Mu Opioid Signaling Protects Against Acute Murine Intestinal Injury in a Manner Involving Stat3 Signaling

“…6 In this response, cells at the edge of the wound undergo a dedifferentiation process and migrate into the wounded area. They then undergo cytoskeletal rearrangement, 7 re-differentiate, and finally re-establish tight junction barriers with their neighboring cells. 6 This process does not require epithelial proliferation, but renewal of cells are needed to replenish the decreased enterocyte pool after injury.…”

“…6 This process does not require epithelial proliferation, but renewal of cells are needed to replenish the decreased enterocyte pool after injury. 7 Numerous proliferative signals such as epidermal growth factor, 7 transforming growth factor ␤, 8,9 and cytokines such as IL-22 10 are implicated in the maintenance of the mucosal barrier. At the molecular level, these proliferative signals use various pathways, including NF-B, mitogen-activated protein kinase, Stat3, and PI3K/Akt 6 pathways.…”

Cell-based models to test the effects of milk-derived bioactives

“…The distance migrated by the cells was increased when colostrum was acid-activated compared with non-acid-activated colostrum. TGF-b1 plays a role in the re-epithelialisation process (Barrientos et al, 2008;Sturm and Dignass, 2008), and therefore, this growth factor was included as a treatment. However, the concentration of TGF-b1 (5 ng/ml), corresponding to the concentration found in colostrum at post-partum day 1 and higher than the concentration found in mature milk (Purup et al, 2007), could not alone explain the migration caused by the mature milk sample or the acid-activated colostrum sample assayed ( Figure 5).…”

Early Epithelial Restitution by Nonsteroidal Anti-Inflammatory Drug–Activated Gene 1 Counteracts Intestinal Ulcerative Injuries

“…However, if epithelial integrity is disrupted by the mucosal insults, it can be rapidly reestablished by epithelial cell proliferation and differentiation (1,2). In response to mucosal injuries, intestinal epithelial cells migrate and spread rapidly prior to cell division in a process known as restitution.…”