Expression of gene for EIIIA- and EIIIB- fibronectin, fetal types of fibronectin, during gastric ulcer healing in rats

Plasma and cellular fibronectin: distinct and independent functions during tissue repair

Fibronectin (FN) is a ubiquitous extracellular matrix (ECM) glycoprotein that plays vital roles during tissue repair. The plasma form of FN circulates in the blood, and upon tissue injury, is incorporated into fibrin clots to exert effects on platelet function and to mediate hemostasis. Cellular FN is then synthesized and assembled by cells as they migrate into the clot to reconstitute damaged tissue. The assembly of FN into a complex three-dimensional matrix during physiological repair plays a key role not only as a structural scaffold, but also as a regulator of cell function during this stage of tissue repair. FN fibrillogenesis is a complex, stepwise process that is strictly regulated by a multitude of factors. During fibrosis, there is excessive deposition of ECM, of which FN is one of the major components. Aberrant FN-matrix assembly is a major contributing factor to the switch from normal tissue repair to misregulated fibrosis. Understanding the mechanisms involved in FN assembly and how these interplay with cellular, fibrotic and immune responses may reveal targets for the future development of therapies to regulate aberrant tissue-repair processes.

Strain matrix-dependently dissociates gut epithelial spreading and motility

BACKGROUND

Repetitive deformation enhances intestinal epithelial migration across tissue fibronectin (tFN) via Src but inhibits migration across collagen. Since cell spreading generally precedes motility, we compared the effects of cyclic strain on Caco-2 spreading and migration on tFN, collagen-I, and plasma fibronectin (pFN), and investigated the role of Src in deformation-influenced spreading and migration.

MATERIALS AND METHODS

Human Caco-2 intestinal epithelial cells on tFN, collagen-I or pFN were subjected to an average 10% strain at 10 cycles/min for 2 h. Src was inhibited with 10muM PP2 or Src was reduced with siRNA. Parallel studies assessed deformation effects on monolayer wound closure.

RESULTS

Deformation, Src-inhibition or reduction each inhibited spreading on tFN but Src-inhibition or reduction prevented further inhibition of spreading by deformation without preventing further inhibition of motility. Deformation did not alter spreading on collagen-I or pFN, but inhibited wound closure.

CONCLUSIONS

Although cell spreading generally precedes and parallels motility, repetitive deformation regulates motility independently of spreading. Since deformation activates Src, the ability of Src blockade to mimic strain-associated inhibition of spreading on tFN suggests that this effect occurs by a separate mechanism that may also require basal Src activity. Further delineation of the mechanisms by which strain disparately modulates spreading and motility may permit acceleration of mucosal healing by targeted interventions to separately promote spreading and epithelial motility.

Fibronectin EIIIA splicing variant: A useful contribution to forensic wounding interval estimation

A fibronectin splicing variant, Fn containing an extra type III domain (EIIIA in rat, ED1 or EDA in human) has recently attracted more attention because of its sensitive response in injury of adult tissue. The characteristic that this form is absent in adult tissue while it is commonly expressed in fetal tissues and injured adult tissue is useful in estimation of injury interval in forensic science. The regulation of fibronectin splicing was studied by immunohistochemistry by using monoclonal antibody to EIIIA on sections from paraffin embedded rat skin sample after contusion. The results indicated that epidermic cells and hair follicle epithelium of rat skin were found positive staining at 6h after injury, and the color became darker with prolonged wounding time. Based on the above result, we invented a type of test paper assayed for EIIIA-Fn splicing variant by using immune colloidal gold technique. After dipping one end of test paper in the supernatant fluid of tissue homogenates of injury skin for few minutes, detecting line could be found. It showed that all experimental injured samples revealed positive staining; the darkness of positive staining was dependent on the injury time, while control normal skin cannot found positive staining. It is concluded that there is a close relationship between the expression of EIIIA-Fn splicing variant and wounding interval, and that the gold-labeled test paper can be useful in distinguishing ante- and post-mortem injury, and in estimation of wounding interval in forensic science.

An overview of acetic acid ulcer models--the history and state of the art of peptic ulcer research

Four types of experimental chronic ulcer models, named acetic acid ulcer models, have been developed to examine the healing process of peptic ulcers, screen anti-ulcer drugs, and better evaluate the adverse effects of various anti-inflammatory drugs on the gastrointestinal mucosa. The model easily and reliably produces round, deep ulcers in the stomach and duodenum, allowing acetic acid ulcer production in mice, rats, Mongolian gerbils, guinea pigs, cats, dogs, miniature pigs, and monkeys. These ulcer models highly resemble human ulcers in terms of both pathological features and healing process. The models have been established over the past 35 years and are now used throughout the world by basic and clinical scientists. One of the characteristic features of acetic acid ulcers in rats is the spontaneous relapse of healed ulcers >100 d after ulceration, an endoscopically confirmed phenomenon. Indomethacin significantly delays the healing of acetic acid ulcers, probably by reducing endogenous prostaglandins and inhibiting angiogenesis in ulcerated tissue. Helicobacter pylori significantly delays healing of acetic acid ulcers and causes relapse of healed ulcers at a high incidence in Mongolian gerbils. Anti-secretory drugs (e.g. omeprazole), prostaglandin analogs, mucosal defense agents (e.g. sucralfate), and various growth factors all significantly enhance healing of acetic acid ulcers. Gene therapy with epidermal growth factor and vascular endothelial growth factor applied to the base of acetic acid ulcers in rats is effective in enhancing ulcer healing. Since an inhibitor of nitric oxide syntase prevents ulcer healing, nitric oxide might be involved in the mechanism underlying ulcer healing. We conclude that acetic acid ulcer models are quite useful for various studies related to peptic ulcers.

Gastroduodenal mucosal defense: coordination by a network of messengers and mediators

Gastroduodenal mucosal defense is composed of structural features of the mucosa, cellular monitors of pending or actual injury, and a web of effector cells that protect the mucosa from damage and govern its recovery from injury. By virtue of these systems, the gastroduodenal mucosa can cope with the harmful ingredients of ingested food and the potentially deleterious effects of gastric acid and pepsin. It is increasingly appreciated that a network of chemical messengers coordinates the alarm, defensive, and healing mechanisms. This article highlights some of the advances from the past year that have furthered our understanding of the regulatory systems that govern gastroduodenal mucosal homeostasis. Particular emphasis is given to control of the mucous and epithelial phospholipid barriers, the mucosal microcirculation, and the epithelial, neural, immune, and inflammatory mediators of the mucosal repair mechanisms.