Granulation Tissue Angiogenesis Research Articles

Cigarette smoking delays ulcer healing: role of constitutive nitric oxide synthase in rat stomach.

Epidemiological studies have shown that cigarette smoking is associated with peptic ulceration. This study aims to investigate the mechanisms by which cigarette smoking delays ulcer healing in rats. Gastric ulcers were induced by applying acetic acid to the luminal surfaces in rats. Twenty-four hours later, rats were exposed to different concentrations of cigarette smoke (0, 2, or 4%) for a 1-h period once daily for 3 or 6 days. Cigarette smoke exposure delayed ulcer healing and decreased gastric blood flow and angiogenesis at the ulcer margin. These changes were accompanied by a significant reduction of constitutive nitric oxide synthase (cNOS) activity but not PGE2 production and vascular endothelial growth factor levels. Administration of L-arginine (10 mg/kg iv) completely reversed the adverse actions on ulcer healing, gastric blood flow, and angiogenesis in the mucosa at the ulcer margin but partially restored angiogenesis in granulation tissues. In conclusion, cigarette smoke exposure delays ulcer healing through depression of gastric blood flow and angiogenesis at the ulcer margin. Reduction of cNOS expression and activity is suggested to be involved in these ulcerogenic processes.

Reduction of EGF is associated with the delay of gastric ulcer healing by cigarette smoke in rats

Epidemiological studies have shown that cigarette smoking is associated with peptic ulceration and also delays ulcer healing in man. This could be due to the disturbance of physiological feedback mechanisms in response to ulcer formation, especially those of growth factors in the body. Aim: To investigate whether reduction of epidermal growth factor (EGF) is responsible for the ulcerogenic mechanism by which cigarette smoking delays ulcer healing. Methods: Male Sprague-Dawley rats (180-200 g) were induced with kissing ulcers in the stomachs by applying 60% acetic acid to the luminal surfaces. Twenty-four hours after ulcer induction, rats were exposed to different concentrations of cigarette smoke (0, 2 or 4%) for l-hr period given once daily for 3 or 6 days. During these periods, ulcer sizes, gastric blood flow, mucosal and serum EGF levels were assessed. In addition, angiogenesis in the granulation tissue at the ulcer base and epithelial cell proliferation at the ulcer margin were also determined by immunohistochemical methods for yon WiUebrand Factor expression and 5-bromo-2'-deoxyuridine (BrdU) incorporation, respectively, in the formalin fixedand paraffin-embedded sections. Results: Cigarette smoke exposure delayed ulcer healing which was accompanied by a reduction of gastric blood flow and a decrease in both angiogenesis in granulation tissue at the ulcer base and epithelial cell proliferation at the ulcer margin. Further study showed that a marked upregulation of EGF was observed 1 day after ulcer induction in serum and 4 days after ulcer induction in the gastric mucosa. However, cigarette smoke exposure significantly depressed these beneficial responses 4 days after ulcer induction. Intravenous administration of EGF (10 or 20 tag/kg) before each cigarette smoke exposure completely reversed the delaying effect of cigarette smoke exposure on ulcer healing and also attenuated the adverse actions on gastric blood flow, angiogenesis and epithelial cell proliferation by cigarette smoke exposure. Conclusion: Reduction of EGF level is one of the mechanisms involved in the delay of ulcer healing induced by cigarette smoking. This study was supported in part by a grant from the Hong Kong Research Grant Council.

Epidermal Growth Factor in Gastric Ulcer Healing by Nocloprost, a Stable Prostaglandin E2 Derivative

Background: The gastroprotective and ulcer-healing properties of prostaglandins, especially in gastric ulcers induced by non-steroidal anti-inflammatory drugs, are well established. Ulcer healing is an active process of filling the mucosal defect with migrating and proliferating epithelial cells combined with angiogenesis in granulation tissue at the ulcer bed. Growth factors, especially epidermal growth factor (EGF) and transforming growth factor alpha (TGFa) are crucial in the regulation of the reconstruction of damaged mucosal structures. Methods: In this double-blind, randomized, prospective study 40 patients with gastric ulcer were treated with nocloprost, a stable prostaglandin E2 derivative, or with ranitidine. All subjects underwent endoscopy before and after 4 and 8 weeks of anti-ulcer therapy. During endoscopy mucosal biopsies were performed for determination of EGF content in gastric mucosa at the ulcer margin and in the intact mucosa. Additionally, EGF output in saliva and its plasma concentrations were determined in all subjects before and during the treatment. Results: The gastric ulcer healing rate after 4 weeks was significantly higher in patients treated with nocloprost than in those treated with ranitidine (63% versus 39%, respectively). At initial examination the EGF content in the gastric mucosa obtained from the ulcer edge was significantly higher than that in the intact mucosa. There was a significant increase in the EGF content in both the ulcer margin and the intact mucosa in subjects treated with nocloprost but not in patients under treatment with ranitidine. Similarly, patients treated with nocloprost had significantly higher EGF output in saliva and higher EGF concentration in plasma throughout the anti-ulcer therapy. Conclusion: Nocloprost is superior to ranitidine in the treatment of chronic gastric ulcers, and these effects could be due, at least in part, to higher expression and mucosal content of EGF in the ulcer area.

Healing of Chronic Gastric Ulcerations by <i>L</i>-Arginine

This study was designed to determine the efficacy of L-arginine in healing of gastric ulcers induced by acetic acid and to assess the role of nitric oxide (NO), prostaglandins, gastrin and polyamines in the healing process. Intragastric administration of L-arginine (32.5-300 mg/kg/day) enhanced the healing rate of these ulcers in a dose-dependent manner, while D-arginine (300 mg/kg/day) was not effective. The acceleration of healing by L-arginine was accompanied by a marked increase in gastric blood flow (GBF) at the ulcer margin, and an enhancement of serum gastrin level, mucosal DNA synthesis, and DNA and RNA contents and angiogenesis in the granulation tissue in the ulcer bed. A similar increase in ulcer healing associated with hyperemia at the ulcer margin and enhanced angiogenesis but without alteration in serum gastrin were observed after treatment with glyceryl trinitrate, an NO exogenous supplier. Treatment with NG-nitro-L-arginine (L-NNA), an inhibitor of NO synthase, delayed ulcer healing and this was accompanied by a reduction of GBF at the ulcer margin and in angiogenesis in granulation tissue and by a decrease in serum gastrin level and mucosal growth. Addition of L-arginine to L-NNA restored ulcer healing, hyperemia at the ulcer margin and angiogenesis and prevented the fall in serum gastrin and mucosal growth caused by L-NNA. Pretreatment with indomethacin also delayed ulcer healing and this was reversed by the coadministration of L-arginine. Inhibition of polyamine biosynthesis by difluoro-methyl-ornithine completely abolished the acceleration of the healing and the increase in mucosal growth induced by L-arginine. Our findings indicate that L-arginine accelerates ulcer healing due to its hyperemic, angiogenic and growth-promoting actions, possibly involving NO, gastrin and polyamines.

Short report: effect of sucralfate on angiogenesis in granulation tissue of acetic acid-induced gastric ulcers in rats.

We investigated the effect of sucralfate on angiogenesis in granulation tissue of gastric ulcers induced by acetic acid in rats using the carmine dye method. Intragastric administration of sucralfate at a dose of 500 mg/kg twice daily for 9 days significantly accelerated ulcer healing and significantly increased the extent of angiogenesis in the ulcer base on the tenth day after ulcer induction. As we reported previously, intragastric administration of cimetidine at a dose of 100 mg/kg once daily for 9 days decreased the extent of angiogenesis on the tenth day. However, combination treatment using sucralfate and cimetidine accelerated ulcer healing significantly, without altering the extent of angiogenesis. It is concluded, therefore, that the treatment with sucralfate may be effective in peptic ulcer disease from the standpoint of angiogenesis in the ulcer base.

Effects of Cimetidine and Omeprazole on Angiogenesis in Granulation Tissue of Acetic Acid-Induced Gastric Ulcers in Rats

We investigated the effects of cimetidine and omeprazole on angiogenesis in granulation tissue and on the healing of gastric ulcers induced by acetic acid in rats. Either cimetidine (50 or 100 mg/kg) or omeprazole (10 or 20 mg/kg) was orally administered once daily for 9 consecutive days from the day following ulcer production. The ulcer index on the 10th and 30th days after ulcer production, and the extent of angiogenesis on the 10th day were examined. Cimetidine dose-dependently decreased the extent of angiogenesis on the 10th day, whereas the ulcer index on the 10th days was not significantly different between cimetidine-treated and control rats. The ulcer index of the groups treated with cimetidine during the initial 9-day period was increased compared with the control group on the 30th day. In contrast, oral omeprazole did not affect angiogenesis on the 10th day and decreased the ulcer index on both the 10th and 30th days. These results suggest that oral cimetidine may inhibit angiogenesis in ulcer granulation tissue possibly via the blocking of histamine H2 receptors and this may be one cause of delayed ulcer healing.

Effects of Prednisolone and Human Epidermal Growth Factor on Angiogenesis in Granulation Tissue of Gastric Ulcer Induced by Acetic Acid

In an attempt to elucidate the role of granulation vessels in the healing of gastric ulcer, healing and angiogenesis in granulation tissue of acetic acid ulcers were studied in rats. In addition, the effects of prednisolone and synthetic human epidermal growth factor (EGF) on angiogenesis and ulcer healing were investigated. The newly formed granulation vessels in the ulcer base were measured by means of a carmine dye infusion method. Prednisolone, administered subcutaneously at 40 mg/kg/day, significantly decreased angiogenesis in the ulcer base on the 10th day after ulcer production, and on the 30th day ulcer healing was found to be significantly delayed. In contrast, angiogenesis was significantly increased, and ulcer healing was enhanced by intragastric administration of 100 micrograms/kg/day of EGF. With combined administration of prednisolone and EGF, angiogenesis was significantly increased compared to that observed with prednisolone treatment alone. The authors conclude that suppression of angiogenesis by prednisolone is a delaying factor in gastric ulcer healing and that exogenous EGF promotes ulcer healing, partly through restoration of angiogenesis.

The Response of the Microvascular System to Radiation: A Review

The microvasculature is a ubiquitous organ system having a major role in the pathogenesis of radiation damage to normal tissues. Although the kinetics of radiation damage to endothelial cells is similar to other tissues (as reflected by Do and Dq) the late effect is a manifestation of injury, not only to the endothelial cell population, but also to the basement membrane. Tissue damage is progressive. The initial expression of radiation injury is an increased permeability leading to changes in the extracellular milieu. There is an irregular proliferation of endothelial cells leading to capillaries of irregular diameter and shape. Fibrous proliferation increases the histohematic barrier and is ultimately reflected in a loss of parenchymal cells. Replacement fibrosis progresses until a steady state is reached where the surviving parenchymal cells can be sustained by the microvasculature. The clinical significance depends on the role of the organ system involved. For patients who have medical conditions which adversely effect the stability of the vascular system (hypertension, diabetes, etc.), the expressions of radiation injury may be more severe and increase the morbidity associated with these diseases. Angiogenesis in granulation tissue is less radiosensitive than in steady-state parenchymal tissues. Wound healing is not significantly affected by commonly used therapeutic doses of irradiation, 40-50 Gy delivered 4-6 weeks preoperatively or postoperatively early in the development of the granulation tissue, but may be complicated where a significant degree of fibrosis has developed. The vascular responses leading to telangiectasia were discussed.

The effect of inhibition of angiogenesis in granulation tissue on wound healing and the fibroblast.

Protamine sulfate given in high doses can inhibit angiogenesis in the granulation tissue generated in an open wound. This is reflected by changes consistent with delayed vascular maturation in the morphology of the regenerating vessels seen at the gross, microscopic, and ultrastructural levels. A coincidental delay in wound healing as evidenced by impaired wound contraction occurs, although fibroblast duplication and myofibroblast differentiation appear intact. However, the fibroblasts contain little endoplasmic reticulum, the site of synthetic activity, and the surrounding collagen appears loose and disorganized. To unite these observations into a coherent pattern, we review the proposal that the endothelial cell, the fibroblast, and the extracellular stroma are interdependent and that maturation of each is necessary to maintain the momentum of wound healing. Our findings fit this mechanistic hypothesis but do not prove it. The abnormal vasoformation that may be initiated by protamine's anticoagulant properties could set the stage for impaired fibroblast synthetic activity. If collagenous stroma is deficient, both endothelial maturation and wound contraction wound fail. Although we saw these final events, to prove a series of cause and effect changes would require further study of the oxygen tension and the fibrin and collagen levels in granulation tissue.