Effect of basic fibroblast growth factor on gastric ulcer healing and its own mRNA expression

A Large Central Bronchopleural Fistula Closed by Bronchoscopic Administration of Recombinant Bovine Basic Fibroblast Growth Factor: A Case Report

A large central bronchopleural fistula (BPF) surrounded by mediastinal tissue was successfully closed by local administration of recombinant bovine basic fibroblast growth factor (rbFGF) using the bronchoscope. No complications were observed during and after this bronchoscopic treatment. This is the first report of the bronchoscopic treatment of a large central BPF by the local spray of rbFGF. The bronchoscopic treatment with rbFGF is a potentially cost-effective method for central BPF surrounded by mediastinal tissue.

Treatment Effects of Jinlingzi Powder and Its Extractive Components on Gastric Ulcer Induced by Acetic Acid in Rats

Jinlingzi powder comprises Melia toosendan Sieb. et Zucc. and Corydalis yanhusuo (Y.H. Chou & Chun C.Hsu) W.T. Wang ex Z.Y. Su & C.Y. Wu and is usually applied in clinic as traditional Chinese medicine for pain. The present study aims to investigate the therapeutic actions of Jinlingzi powder and its extracted components and theirs treatment mechanism on the acetic acid induced-gastric ulcer in rats. The gastric ulcer model was induced by the administration of acetic acid in rats (84 male). Jinlingzi powder water decoction, its polysaccharide, and nonalkaloid and alkaloid components were used to investigate the therapeutic actions on the acetic acid induced-gastric ulcer by measuring the related pharmacy and pharmacodynamic factors, including ulcer index, ulcer area, ulcer healing rate, interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α), neurotensin (NT), platelet activating factor (PAF), thromboxane B2 (TXB2), and vascular endothelial growth factor (VEGF) in rat serum, acetylcholinesterase (AChE) in brain tissue, prostaglandin E2 (PGE2), and basic fibroblast growth factor (bFGF) in gastric tissue. Among the various groups, Jinlingzi powder and the nonalkaloid components caused significant changes in IL-8, TNF-α, NT, PAF TXB2, and VEGF values in the serum. The AChE content in the rats' brain tissue was also reduced after using Jinlingzi powder and the nonalkaloid components. Additionally, Jinlingzi powder and the nonalkaloid components considerably affect the amount of PGE2 and bFGF in a rat's stomach tissue. Therefore, Jinlingzi powder and the nonalkaloid components can effectively inhibit neutral neutrophil activation, prevent capillaries thrombosis, and protect gastric mucosa. Thus, the nonalkaloid components of the Jinlingzi powder play a key role in the treatment of gastric ulcer.

Can serum progranulin levels be a biomarker following gastric ulcer therapy?

Introduction

Progranulin is a novel growth factor that has several physiological and pathological roles such as cell growth, tumourigenesis, embryogenesis, wound healing, and inflammation.

Aim

To compare the pre-treatment and post-treatment serum levels of the angiogenic factor vascular endothelial growth factor (VEGF), pro-inflammatory cytokine tumor necrosis factor α (TNF-α), and progranulin in peptic ulcer (PU) patients with a healthy control group.

Material and methods

Serum VEGF, TNF-α, and progranulin levels were studied with ELISA in 42 PU patients (antral ulcer (AU): 22, duodenal ulcer (DU): 20) and 15 healthy controls.

Results

The serum progranulin levels before treatment were 4237.35 ±1091.30 pg/ml in the patients with AU, 4682.64 ±1501.46 pg/ml in the patients with DU, 3055.66 ±626.88 pg/ml in the control group, and 4460 ±1315 pg/ml in the ulcer (AU and DU) group. The serum progranulin levels were 3607.7 ±869.4 pg/ml in the AU group, 4286.5 ±1208.78 pg/ml in the DU group, and 3947.1 ±1094.64 pg/ml in the ulcer group after the treatment. When comparing pre-treatment serum progranulin levels of the AU group, DU group, and ulcer group with the control group there were statistically significant differences (p < 0.001, p < 0.0001, p < 0.0001, respectively).

Conclusions

The disappearance of the difference in terms of post-treatment serum levels of progranulin between the AU group and the control group suggests that serum levels of progranulin can be used as a biomarker of gastric ulcer healing.

Clopidogrel inhibits angiogenesis of gastric ulcer healing via downregulation of vascular endothelial growth factor receptor 2

BACKGROUND/PURPOSE

Although clopidogrel does not cause gastric mucosal injury, it does not prevent peptic ulcer recurrence in high-risk patients. We explored whether clopidogrel delays gastric ulcer healing via inhibiting angiogenesis and to elucidate the possible mechanisms.

METHODS

Gastric ulcers were induced in Sprague Dawley rats, and ulcer healing and angiogenesis of ulcer margin were compared between clopidogrel-treated rats and controls. The expressions of the proangiogenic growth factors and their receptors including basic fibroblast growth factor (bFGF), bFGF receptor (FGFR), vascular endothelial growth factor (VEGF), VEGFR1, VEGFR2, platelet-derived growth factor (PDGF)A, PDGFB, PDGFR A, PDGFR B, and phosphorylated form of mitogenic activated protein kinase pathways over the ulcer margin were compared via western blot and reverse transcription polymerase chain reaction. In vitro, human umbilical vein endothelial cells (HUVECs) were used to elucidate how clopidogrel inhibited growth factors-stimulated HUVEC proliferation.

RESULTS

The ulcer sizes were significantly larger and the angiogenesis of ulcer margin was significantly diminished in the clopidogrel (2 and 10 mg/kg/d) treated groups. Ulcer induction markedly increased the expression of phosphorylated form of extracellular signal-regulated kinase (pERK), FGFR2, VEGF, VEGFR2, and PDGFRA when compared with those of normal mucosa. Clopidogrel treatment significantly decreased pERK, FGFR2, VEGF, VEGFR2, and PDGFRA expression at the ulcer margin when compared with those of the respective control group. In vitro, clopidogrel (10(-6)M) inhibited VEGF-stimulated (20 ng/mL) HUVEC proliferation, at least, via downregulation of VEGFR2 and pERK.

CONCLUSION

Clopidogrel inhibits the angiogenesis of gastric ulcer healing at least partially by the inhibition of the VEGF-VEGFR2-ERK signal transduction pathway.

Clopidogrel delays gastric ulcer healing in rats

Clopidogrel is not safe enough for the gastric mucosa in patients with high risk of peptic ulcer. This study aimed to explore if clopidogrel delays gastric ulcer healing and elucidate the involved mechanisms. Gastric ulcer was induced in rats and the ulcer size, mucosal epithelial cell proliferation of the ulcer margin, expression of growth factors [epidermal growth factor (EGF), basic fibroblast growth factor] and their receptors, and signal transduction pathways for cell proliferation were measured and compared between the clopidogrel-treated group and untreated controls. For the in vitro part, rat gastric mucosal epithelial cell line (RGM-1 cells) was used to establish EGF receptor over-expressed cells. Cell proliferation and molecular change under EGF treatment (10ng/ml) with and without clopidogrel (10(-6)M) were demonstrated. Ulcer size was significantly larger in the clopidogrel-treated group compared to the control and mucosal epithelial cell proliferation of the ulcer margin was significantly decreased in the clopidogrel-treated group (P<0.05). Clopidogrel (2mg and 10mg/kg/day) significantly decreased ulcer-induced gastric epithelial cell proliferation and ulcer-stimulated expressions of EGF receptor and phosphorylated extracellular signal-regulated kinase (PERK) at the ulcer margin (P<0.05). Clopidogrel (10(-6)M) also inhibited EGF-stimulated EGF receptor, PERK expression, and cell proliferation in RGM-1 cells (P<0.05), and caused much less inhibition of EGF-stimulated cell proliferation in EGF receptor over-expressed RGM-1 cells than in RGM-1 cells (22% vs. 32% reduction). In conclusion, clopidogrel delays gastric ulcer healing in rats via inhibiting gastric epithelial cell proliferation, at least by inhibition of the EGF receptor-ERK signal transduction pathway.

Collagen matrix-bound clotting factors (CMBCF) promote healing-associated events independent of factor XIII in an in vitro model

We have previously explored in vitro as well as in vivo models of the biological effects of liquid fibrin glue (FG) containing factor XIII. The fixed combination of a collagen matrix and coagulation factors I and IIa (TachoSil(®) , Nycomed, Linz, Austria) is void of factor XIII. We aimed to determine whether (1) this preparation exerts similar effects to liquid FG on cells in an in vitro system, or (2) this effect is modulated by factor XIII. In an in vitro model, the effect of the fixed combination of collagen matrix and coagulation factors I and IIa (collagen matrix-bound clotting factor [CMBCF]) on the expression and secretion of growth factors (vascular endothelial growth factor, platelet-derived growth factor, fibroblast growth factor-2) by gastric epithelial (AGS) and mesenchymal cells (fibroblasts), as well as their proliferative response (WST-test), was compared in the presence and absence of factor XIII. The use of CMBCF compared with collagen type I matrix resulted in an increased proliferation rate of fibroblasts; there was an increased secretion of fibroblast growth factor-2. Gastric epithelial cells secreted more vascular endothelial growth factor and platelet-derived growth factor into the culture supernatant in the presence of CMBCF. All responses remained unaltered by the addition of factor XIII in different concentrations. In conclusion, CMBCF exerted effects similar to liquid FG in an in vitro model of healing. The addition of factor XIII did not alter the response of mesenchymal or epithelial cells, with respect to proliferation and growth factor secretion.

Acquired hyperplastic gastric polyps after treatment of ulcer

BACKGROUND/PURPOSE

Healing of gastric ulcers requires repair by epithelial migration and proliferation. We have found a small proportion of patients with acquired hyperplastic polyps at the healed ulcer site. The aim of this study was to identify clinical characteristics that might be associated with the development of hyper-plastic polyps at the site of healed gastric ulcers.

METHODS

This was a retrospective review of 86 patients with gastric ulcers from April 2006 to September 2008. After initial endoscopy, the patients were all treated with proton pomp inhibitors, after which a second endoscopy was performed. Demographic data, polyp characteristics (endoscopic and histological), Helicobacter pylori status, and duration of treatment were analyzed.

RESULTS

A total of 24 hyperplastic gastric polyps were found in 18 patients; all at the site of the healed ulcer (20 in the antrum and 4 in the corpus). The mean size of the ulcers prior to treatment was 14.5 +/- 9.1 mm. Hyperplastic gastric polyps were more likely to occur at the site of ulcers larger than 10 mm (odds ratio = 9.57, 95% confidence interval =2.50-36.65). Age, sex, H. pylori status, ulcer location and duration of treatment did not differ significantly between patients with and without polyps.

CONCLUSION

Hyperplastic polyps that develop after healing of gastric ulcers are likely to be extensive mucosal injury. A gastric ulcer larger than 10 mm is associated with a significantly increased risk of hyperplastic polyps.

Helicobacter pylori eradication therapy may facilitate gastric ulcer healing after endoscopic mucosal resection: a prospective randomized study

BACKGROUND AND AIM

It remains unclear whether Helicobacter pylori eradication therapy affects the healing rate of iatrogenic ulcers following endoscopic mucosal resection (EMR) for gastric tumors. The aim of our study was to prospectively evaluate the effect of H. pylori eradication therapy on gastric ulcer healing after EMR.

METHODS

After EMR, patients were randomly assigned to either the H. pylori eradication group (Hp group) (lansoprazole 30 mg, amoxicillin 1000 mg, and clarithromycin 500 mg, twice a day for 7 days) or the noneradication group (proton pump inhibitor, PPI group) (lansoprazole 30 mg, twice a day for 7 days). Four weeks after EMR, the ulcer stages and size were compared between the two groups. Moreover, ulcer-related symptoms, bleeding rates, adverse effects, and drug compliance were compared.

RESULTS

A total of 64 patients were enrolled. Of these, 17 patients were excluded from the study. The two groups were comparable in terms of baseline clinicopathologic characteristics. Four weeks after EMR, the two groups did not differ with respect to ulcer stage (p = .475) or ulcer-related symptoms (p = .399). However, the ulcer reduction ratio was significantly higher in the Hp group (0.028 +/- 0.024 vs. 0.065 +/- 0.055, p < .05). No differences were observed between the two groups with regard to drug compliance, adverse drug event rates, or bleeding rates.

CONCLUSIONS

Our results suggest that H. pylori eradication therapy might improve the ulcer healing rate after EMR.

Identification and characterization of bioactive factors in bladder submucosa matrix

In spite of long term clinical use of decellularized bladder submucosa matrix (BSM), little is known about the active factors within this material. In this paper, we analyzed the biological factors from the decellularized BSM using ELISA, Western blotting, and immunohistochemistry for the purpose of effective utilization of this material in the field of regenerative medicine. At least 10 growth factors, including VEGF, BMP4, PDGF-BB, KGF, TGFbeta1, IGF, bFGF, EGF and TGFalpha were found to be preserved in the decellularized BSM. The existence of collagen (type 1, 2, 3, 4), laminin and elastin within the matrix was also demonstrated. The soluble BSM extracts showed a conspicuous effect on cell proliferation when added as a supplement in vitro. These findings demonstrate that growth factors and extracellular matrix in the BSM maintain valuable biological activity even after the decellularization and extraction processes, thus supporting the wide applicability of BSM in tissue regeneration. The identification and characterization of growth factors and extracellular matrix in the BSM is a prerequisite for understanding tissue regeneration using this scaffold.

Role of receptor tyrosine kinases in gastric cancer: New targets for a selective therapy

Receptor tyrosine kinases (RTKs) such as the epidermal growth factor receptor family participate in several steps of tumor formation including proliferation and metastatic spread. Several known RTKs are upregulated in gastric cancer being prime targets of a tailored therapy. Only preliminary data exist, however, on the use of the currently clinically available drugs such as trastuzumab, cetuximab, bevacizumab, gefitinib, erlotinib, and imatinib in the setting of gastric cancer. Preclinical data suggest a potential benefit of their use, especially in combination with “conventional” cytostatic therapy. This review summarizes the current knowledge about their use in cancer therapy as well as new approaches and drugs to optimize treatment success.

Angiogenesis, cell proliferation and apoptosis in gastric ulcer healing. Effect of a selective cox-2 inhibitor

To elucidate the role of cyclooxygenase-2, we compared the effects of rofecoxib, a selective cyclooxygenase-2 inhibitor, and ibuprofen, a nonselective cyclooxygenase inhibitor, on the evolution of acetic-acid-induced gastric ulcers in rats, evaluating growth factor expression, the angiogenic process, cell proliferation and cell apoptosis. Levels of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), angiogenesis and cell proliferation were analysed by immunohistochemical methods, and apoptosis was evaluated by an enzyme immunoassay. Both growth factors and microvessels appeared to be abundant in the granulation tissue of the ulcer bed. Rofecoxib (2.5 mg/kg/day) and ibuprofen (100 mg/kg/day) delayed ulcer healing, but only rofecoxib treatment provoked a reduction of bFGF expression and inhibition of the development of new microvessels. No changes in VEGF expression were detected. Results also showed that proliferation and apoptosis were increased in control ulcerated animals. Rofecoxib reduced significantly both processes. These findings demonstrate that a reduction of bFGF expression and an antiangiogenic action, as well as proliferation/apoptosis inhibition, are some of the mechanisms possibly implicated in the delay in ulcer healing seen after the administration of the highly selective COX-2 inhibitor rofecoxib.

Fibrin glue, healing of gastric mucosal injury, and expression of growth factors: results from a human in vivo study

BACKGROUND

Fibrin glue is used in the endoscopic therapy of bleeding ulcerations. Accelerated closure of ulcers has been attributed to this treatment; the biologic reason, however, remains unclear.

METHODS

Two artificial gastric lesions were induced in healthy, Helicobacter pylori negative volunteers and were treated by injection of either saline solution or fibrin glue. After 72 hours, resulting ulcers were measured and biopsy specimens were taken for immunohistochemistry (to identify proliferating cells and small vessels) and assessment of growth factor messenger RNA (mRNA) expression (platelet derived growth factor, vascular endothelial growth factor, fibroblast growth factor 2 [FGF-2]) by real-time reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

After 72 hours, most lesions exposed to fibrin glue were smaller than the corresponding ones treated with saline solution. The ulcer rim was more pronounced; immunohistochemistry revealed more proliferating cells (p < 0.02 compared with saline solution). The number of microvessels also increased, though this difference did not reach statistical significance (p = 0.10). FGF-2 mRNA expression markedly increased (about 7-fold compared with the control [ p < 0.001], and about 5-fold compared with saline solution [ p < 0.015]); whereas, with respect to platelet derived growth factor and vascular endothelial growth factor mRNAs, only small changes occurred.

CONCLUSIONS

Fibrin glue positively modulates gastric ulcer healing by causing an increase in the number of proliferating cells in the ulcer margin and also possibly enhances the density of microvessels. These changes are accompanied by an enhanced expression of FGF-2, which is known to exert beneficial effects on ulcer healing.

Dexamethasone delays ulcer healing by inhibition of angiogenesis in rat stomachs

Using the non-ulcerogenic doses of dexamethasone, we explored the action of glucocorticoids on ulcer healing and its relationship with angiogenic factors in the gastric mucosa. We applied dexamethasone (0.1 or 0.2 mg/kg/day) intragastrically in rats with acetic acid-induced gastric ulcer. The mucosal prostaglandin E(2) level and protein expressions of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) at the ulcer margin were determined. Ulcer induction significantly increased protein expressions of bFGF, VEGF, and prostaglandin E(2) level at the ulcer margin together with angiogenesis at the ulcer margin and base. The non-ulcerogenic doses of dexamethasone inhibited angiogenesis at the ulcer margin and ulcer base and delayed ulcer healing. These were associated with a significant decrease of prostaglandin E(2) level and VEGF expression, but not the bFGF expression. Supplementation with prostaglandin E(2) attenuated the inhibitory action of dexamethasone on VEGF expression and reversed the adverse effects of dexamethasone on angiogenesis and ulcer healing, without influencing bFGF expression. We concluded that dexamethasone given at non-ulcerogenic doses could decrease angiogenesis and delay acetic acid-induced ulcer healing; these actions were at least, in part, due to depletion of prostaglandin E(2) level followed by down-regulation of VEGF at the ulcer margin of the stomach.

Mucosal concentration of basic fibroblast growth factor in the healing process in human giant gastric ulcers

OBJECTIVES

Basic fibroblast growth factor (bFGF) is a key factor in the healing of human and experimental peptic ulcers, but the behavior of bFGF in human giant gastric ulcer remains to be determined. We determined the bFGF content in the rim of giant ulcers (bFGF rim) and in non-ulcerated mucosa located opposite the ulcer (bFGF opposite) before and during treatment.

METHODS

Biopsy specimens were endoscopically obtained from 31 patients with giant gastric ulcers and 17 patients with small ulcers before and 2, 4 and 8 weeks after treatment. The bFGF concentrations in the specimens were measured using a sandwich enzyme immunoassay.

RESULTS

Before treatment, the bFGF rim and bFGF opposite concentrations were not associated with ulcer size. The bFGF rim concentration before treatment in the rapid healing group was higher than that in the slow healing group, but no significant difference in bFGF opposite concentrations were found between the two groups. The bFGF rim concentration in the rapid healing patients decreased during treatment, while the slow healing patients showed an inverse response. The bFGF opposite concentration did not change during treatment and bFGF rim concentrations in Helicobacter pylori-positive stomachs were significantly lower than those in H. pylori-negative stomachs.

CONCLUSIONS

The bFGF rim concentration is not involved in the formation of giant gastric ulcers in humans. However, the bFGF rim concentration does appear to promote healing. The bFGF opposite concentration is not related to either the formation or healing of giant gastric ulcers.

The healing effects of Centella extract and asiaticoside on acetic acid induced gastric ulcers in rats

In this study, the healing effects of Centella asiatica water extract (CE) and asiaticoside (AC), an active constituent of CE, on acetic acid induced gastric ulcers (kissing ulcers) in rats were examined. CE was prepared from Centella asiatica dry plant and the concentration of AC in CE was quantitatively determined with the use of high performance liquid chromatography analysis. Different concentrations of CE and AC were orally administered to rats with kissing ulcers. They were found to reduce the size of the ulcers at day 3 and 7 in a dose-dependent manner, with a concomitant attenuation of myeloperoxidase activity at the ulcer tissues. Epithelial cell proliferation and angiogenesis were on the other hand promoted. The expression of basic fibroblast growth factor, an important angiogenic factor, was also upregulated in the ulcer tissues in rats treated with CE or AC. These results further suggest the potential use of Centella asiatica and its active ingredient as anti-gastric ulcers drugs.

Dynamics and localization of activin A expression in rat gastric ulcers

BACKGROUND

Activin A, the homodimer of the activin/inhibin betaA subunit, has been shown to participate in cutaneous wound healing. In this study we intended to determine its part in gastric ulceration.

METHODS

Activin A expression was studied by immunohistochemistry and in situ hybridization in acetic-acid-induced chronic gastric ulcers in rat. The dynamics of this process were also assessed by quantitative real time RT-PCR and RNase protection assays (RPA). The effects of different doses of this cytokine on epithelial and mesenchymal cell proliferation were quantitated in vitro.

RESULTS

Low amounts of activin A and its mRNA were expressed by epithelia, endothelia and fibroblasts in intact gastric tissue. Granulation tissue of gastric ulcers and gastric glands adjacent to the ulcer rim expressed markedly increased amounts of activin protein as well as activin/inhibin betaA mRNA. RPA and RT-PCR studies revealed a more than 3-fold increase in the relative abundance of this mRNA. Activin A did not affect the proliferation rate of fibroblasts and epithelial cells in vitro.

CONCLUSIONS

Activin A participates in gastric ulcer healing in a similar fashion as in cutaneous wounding. Its expression on protein and mRNA level is markedly increased in ulcer base and rim.

Antiangiogenic effect of a highly selective cyclooxygenase-2 inhibitor on gastric ulcer healing in rats

Selective cyclooxygenase-2 (COX-2) inhibitors have been shown to produce fewer gastrointestinal adverse reactions when compared with conventional nonselective nonsteroidal anti-inflammatory drugs and they suppress angiogenesis in tumors. The purpose of the present study was to investigate the effects of highly selective COX-2 inhibitor on angiogenesis and protein expression of angiogenic factor during gastric ulcer healing. Gastric ulcers were induced in male Sprague-Dawley rats by a luminal application of acetic acid solution. Rofecoxib, a selective COX-2 inhibitor, was administered at a dose of 10 mg/kg/day by gastric intubation for 14 successive days. The ulcer size was measured at different time intervals after ulcer induction. The microvessels that were immunohistologically positive for von Willebrand factor within the ulcer bed were counted. The protein levels of basic fibroblast growth factor (bFGF) and concentration of prostaglandin E(2) (PGE(2)) in the ulcer tissues were analyzed with Western blotting and immunoassay methods, respectively. The results demonstrated that rofecoxib treatment significantly increased the ulcer size at days 6, 10, and 15. It decreased the number of microvessels, bFGF protein expression, and PGE(2) level in the ulcer base at day 6. The findings that highly selective COX-2 inhibitor delayed ulcer healing in rats and impaired angiogenesis in the ulcer base raise cautions regarding the use of COX-2 inhibitors in patients with gastric ulcers.

Role of growth factors and their receptors in gastric ulcer healing

The repair of gastric ulcers requires the reconstitution of epithelial structures and the underlying connective tissue, including vessels and muscle layers. Several growth factors have been implicated in this process, since they are able to regulate important cell functions, such as cell proliferation, migration, differentiation, secretion, and degradation of extracellular matrix, all of which are essential during tissue healing. Epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), hepatocyte growth factor (HGF), and trefoil factors (TFFs) are mainly involved in the reconstitution of the epithelial structures. Platelet derived growth factor (PDGF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and transforming growth factor-beta (TGF-beta) play a major role in the reconstitution of connective tissue, including vessels and smooth muscle cells, and provide the extracellular matrix substrate for cell migration and differentiation. The expression of these growth factors and their receptors is increased during ulcer healing and, in some cases, intracellular signaling related to receptor binding and transduction has been demonstrated. EGF, TGF-alpha and TFFs are normally present either in the gastric juice or in the mucosa, and may exert their effects immediately after damage, before newly synthesized EGF and TFFs are released from the ulcer margin. The inhibition of their effects by neutralizing antibodies may result in delayed ulcer healing, while the administration of recombinant or natural analogues may improve ulcer repair. In this review, we will summarize the basic molecular characteristics of some of these growth factors, and will discuss available evidence supporting their role in the ulcer repair process.

Remodeling of extracellular matrix in gastric ulceration

The quality of ulcer repair remains crucial for the stability of the injured tissue and for preventing recurrence. Therefore, we studied the temporo-spatial expression of the fibrillar and basement membrane collagens (types I, III, and IV), the collagenase MMP-2 as well as its inhibitor TIMP-1 before and after oral administration of basic fibroblast growth factor (b-FGF) over 30 days in acetic acid-induced rat gastric ulcers. The alterations and the exact location of the mRNA transcripts and their precipitated proteins were visualized by means of radioactive in situ hybridization and immunohistochemistry. Our data show that hybridization signals of procollagen I could first be identified 2 hours after ulcer induction. After 12 hours the ulcer was established and the mRNA was enhanced at the ulcer margin. After 24-48 hours the other procollagen transcripts were detected and all were further upregulated over the mesenchymal cells of all gastric layers up to 21 days, then declined at 30 days. In contrast, MMP-2 became prominent after 48 hours and up to 21 days. TIMP-1 was enhanced at 72 hours. After oral administration of b-FGF the transcriptional activity of the procollagens and MMP-2 was not significantly altered, while ulcer diameter was significantly reduced. We conclude that the early onset and long duration of collagens' expression points to their central structural and functional role in gastric ulcer healing. MMP-2 seems to be involved in both active ulceration and ECM remodeling. The timing of TIMP/MMP expression may be critical for proper restoration of gastric wall integrity.

Aspirin effects on gastric epithelial cell proliferation and cytokine expression

Aspirin is known to cause gastric injury and to delay ulcer healing. The effects of aspirin on gastric epithelial cell function are heterogeneous; in contrast to injuring the mucosa, aspirin may also act beneficially by inducing adaptation; a mechanism that is poorly understood. We aimed to document the effects of different doses of aspirin on gastric epithelial cell function defined as proliferation, and secretion as well as mRNA expression of cytokines. Furthermore, we studied the effects of aspirin pretreatment on cytokine secretion as a potential element of gastric adaptation. The proliferative activity of three different gastric epithelial cell lines (AGS, KATO III, RGM-1) was assessed by (3)H-thymidine incorporation; secretion of growth factors PDGF-AB and VEGF into culture supernatant was documented by ELISA. mRNA transcripts of both cytokines were quantified by real time RT-PCR. Low doses of aspirin did not alter the proliferative dynamics in two of the three studied cell lines; high doses abolished proliferation. Secretion of PDGF-AB and VEGF increased during the first days of low dose aspirin exposition; higher concentrations led to a depletion of cytokines after an initial liberation in the case of VEGF, mRNA of which was also dose-dependently increased by aspirin. Seven-day pretreatment with low amounts of aspirin did not alter the secretory response of the epithelia caused by higher doses of this drug. The secretion of cytokines and proliferation of gastric epithelial cells are adversely effected by aspirin in a similarly dose-dependent fashion as the intended effects of this drug on platelet function and pain relief.

Role of leptin in ulcer healing

Leptin was shown to exhibit similar to cholecystokinin (CCK) cytoprotective activity against acute gastric lesions, but its role in ulcer healing has not been examined. The aims of this study were: (1) to compare the effects of exogenous leptin to those of CCK on the course of healing of chronic gastric ulcers; (2) to study the gene and protein expression of leptin at the ulcer margin during ulcer healing; and (3) to assess the effects of leptin administration on the mucosal gene expression of main growth factor such as transforming growth factor alpha (TGFalpha). Gastric ulcers were produced in rats by the acetic acid method. Rats with ulcers were divided in following treatment groups: (1) vehicle; (2) leptin (10 microg/kg i.p.); (3) CCK (10 microg/kg s.c.); and (4) leptin or CCK with or without tyrphostin A46 (200 microg/kg i.p.), an inhibitor of epidermal growth factor (EGF)-receptor tyrosine kinase or NG-nitro-L-arginine (20 mg/kg i.g.), a blocker of nitric oxide synthase. Animals were euthanized 9 days after ulcer induction. The area of gastric ulcers and the gastric blood flow at the ulcer area were determined. In addition, mucosal biopsy samples were taken from the ulcer area for histological evaluation as well as for the determination of mRNA and protein expression for leptin and constitutive nitric oxide synthase (cNOS) and inducibile nitric oxide synthase (iNOS) by reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blot, respectively. In addition, the gene expression for TGFalpha was analyzed by RT-PCR. Both leptin and CCK reduced significantly the ulcer area as compared to vehicle-treated group by approximately 50%. The treatment with tyrphostin or N(G)-nitro-L-arginine reversed in part the acceleration of ulcer healing by leptin and CCK. The expression of leptin mRNA and protein was significantly increased at the ulcer edge. The leptin-induced acceleration of ulcer healing was associated with increased expression of transcripts for TGFalpha as well as increased mRNA and protein expression for cNOS and iNOS at the ulcer margin. We conclude that leptin accelerates ulcer healing by mechanisms involving the up-regulation of TGFalpha and increased production of nitric oxide due to up-regulation of cNOS and iNOS in the ulcer area.

Gastroduodenal mucosal defense

The gastroduodenal mucosa is a model system of defense with several structural levels and biologic strategies that are closely interrelated with each other to cope with the harmful ingredients of ingested food and the potentially deleterious effects of gastric acid and pepsin. Experimental and clinical research carried out during the review period added to the understanding of each component of the multiple mechanisms of gastroduodenal mucosal protection. In the first place, mucosal integrity is defended by the mucus gel barrier, the epithelial cell barrier, and the immune barrier. The properties of these barriers are maintained by adequate regulation of mucus production, bicarbonate secretion, mucosal microcirculation, and motor activity. These regulatory systems are alarmed by nociceptive neurons and the mucosal immune system which includes chemokine-secreting epithelial cells. The ultimate defense system is rapid repair of the injured mucosa under the control of several growth factors. Progressing insight into the network of mucosal defense not only will improve existing therapies of inflammation and ulceration but also will provide new leads for the management of functional diseases in the gastroduodenal region.