Healing of colonic ischemic anastomoses in the rat: role of superoxide radicals

Application of laser speckle contrast imaging in laparoscopic surgery

Anastomotic leakage is a worldwide problem in gastrointestinal surgery which seems to be related to the state of microcirculation. Laser speckle contrast imaging (LSCI) could give surgeons insight in the state of microcirculation to attune the site of anastomosis. This work studies the feasibility of LSCI as a tool for this purpose. An experimental setup was developed using a commercially available laparoscopic video system. Laser speckle contrast imaging is capable of detecting ischemic areas on the large intestine. Further research and development are required before adaptation of this technique in the operating room.

Effect of Alprostadil on Colorectal Anastomoses Under Relative Ischemia

BACKGROUND

Anastomotic leak after colorectal surgery, which remains a serious clinical problem that causes augmented morbidity and mortality, is usually favored by ischemia. The aim of this study was to determine whether alprostadil may improve anastomotic wound healing under ischemic condition.

METHODS

Ninety-three adult Wistar rats were randomized into three groups: control, ischemia (by devascularization along the first 2 cm at each anastomotic end), and ischemia plus alprostadil. Resection of a colonic segment at the colorectal junction and an anastomosis was performed. Animals were euthanized at 8 d. Surgical site infection, anastomotic leak, and grade of intra-abdominal adhesions using a validated scale were determined. Bursting pressure and tension were calculated and histologic examination of the anastomosis was performed.

RESULTS

The ischemic group revealed an increased anastomotic leak rate (14/31 versus 3/31) and a lower bursting pressure and tension when compared to control group, validating therefore the experimental model. After intraperitoneal injection of alprostadil, anastomotic leak rate was significantly lower (5/31) and the bursting pressure and tension were significantly increased. Histologic examination revealed a lower presence of inflammatory cells, and a significantly higher neovascularization and a higher presence of fibroblasts in treated animals when compared with the ischemic group.

CONCLUSIONS

Alprostadil may have a positive effect on colonic anastomotic wound healing under relative ischemic condition. Alprostadil administration increases anastomotic bursting pressure, decreases leak rate, and reverses most of the histological changes caused by blood flow decrease. These protective effects could be caused by vasodilation, stimulation of neovascularization, and immunomodulatory properties.

Therapeutic improvement of colonic anastomotic healing under complicated conditions: A systematic review

AIM: To identify therapeutic agents for the prophylaxis of gastrointestinal anastomotic leakage (AL) under complicated conditions.

METHODS: The PubMed and EMBASE databases were searched for English articles published between January 1975 and September 2014. Studies with the primary purpose of improving anastomotic healing in the colon or rectum under complicated preoperative and/or intraoperative conditions were included. We excluded studies investigating the adverse effects or risk assessment of an active intervention. Furthermore, investigations of biophysical materials, sealants, electrical stimulation and nutrients were excluded. The primary study outcome was biomechanical anastomotic strength or AL. The meta-analysis focused on therapeutic agents that were investigated in one animal model using the same outcome by at least three independent research groups.

RESULTS: The 65 studies included were divided into 7 different complicated animal models: Bowel ischemia, ischemia/reperfusion, bowel obstruction, obstructive jaundice, peritonitis, chemotherapy and radiotherapy. In total, 48 different therapeutic compounds were examined. The majority of investigated agents (65%) were reported as beneficial for anastomotic healing. Twelve of the agents (25%) were tested more than once in the same model, whereas 13 (27%) of the agents were tested in two or more models of complicated healing. Two therapeutic agents met our inclusion criteria for the meta-analysis. Postoperative hyperbaric oxygen therapy significantly increased anastomotic bursting pressure in ischemic colon anastomoses by a mean of 28 mmHg (95%CI: 17 to 39 mmHg, P < 0.00001). Granulocyte macrophage-colony stimulating factor failed to show a significant increase in anastomotic bursting pressure (95%CI: -20 to 21 mmHg, P = 0.97) vs controls in experimental chemotherapeutic models.

CONCLUSION: This systematic review identified potential therapeutic agents, but more studies are needed before concluding that any of these are useful for AL prophylaxis.

Is combined therapy more effective than growth hormone or hyperbaric oxygen alone in the healing of left ischemic and non-ischemic colonic anastomoses?

OBJECTIVE

Our aim was to investigate the effects of growth hormone (GH), hyperbaric oxygen and combined therapy on normal and ischemic colonic anastomoses in rats.

METHODS

Eighty male Wistar rats were divided into eight groups (n = 10). In the first four groups, non-ischemic colonic anastomosis was performed, whereas in the remaining four groups, ischemic colonic anastomosis was performed. In groups 5, 6, 7, and 8, colonic ischemia was established by ligating 2 cm of the mesocolon on either side of the anastomosis. The control groups (1 and 5) received no treatment. Hyperbaric oxygen therapy was initiated immediately after surgery and continued for 4 days in groups 3 and 4. Groups 2 and 6 received recombinant human growth hormone, whereas groups 4 and 8 received GH and hyperbaric oxygen treatment. Relaparotomy was performed on postoperative day 4, and a perianastomotic colon segment 2 cm in length was excised for the detection of biochemical and mechanical parameters of anastomotic healing and histopathological evaluation.

RESULTS

Combined treatment with hyperbaric oxygen and GH increased the mean bursting pressure values in all of the groups, and a statistically significant increase was noted in the ischemic groups compared to the controls (p<0.05). This improvement was more evident in the ischemic and normal groups treated with combined therapy. In addition, a histopathological evaluation of anastomotic neovascularization and collagen deposition showed significant differences among the groups.

CONCLUSIONS

Combined treatment with recombinant human growth hormone and hyperbaric oxygen resulted in a favorable therapeutic effect on the healing of ischemic colonic anastomoses.

Influence of extremely low-frequency magnetic field on the activity of antioxidant enzymes during skin wound healing in rats

The aim of this study was to evaluate the activity of the antioxidant enzymes mitochondrial and cytosolic superoxide dismutase (EC 1.15.1.1), glutathione peroxidase (POX, EC 1.11.1.9) and glutathione S-transferase (EC 3.1.2.7), as well as the concentration of malone dialdehyde (MDA), as an indicator of lipid peroxidation rate in the liver tissue homogenates and blood serum of male rats exposed to extremely low-frequency magnetic field (ELF-MF) in order to improve the healing process of an experimental cut wound on the back of each animal. The exposure to ELF-MF with frequency 40 Hz and magnetic flux density 10 mT induced an increase in POX serum activity and a decrease in MDA contents in the liver tissue, which suggests the inhibition of phospholipid peroxidation and subsequent stabilization of cellular membranes, as a result of ELF-MF action. Based on the results obtained, it seems that ELF-MF could be a useful supplement in the complex treatment of prolonged wound healing, due to the activation of endogenous enzymatic antioxidant system.

VEGF-A and FGF gene therapy accelerate healing of ischemic colonic anastomoses (experimental study)

BACKGROUND

Reducing ischemic damage is one of the goals of surgery. The aim of this study was to apply human VEGF-A and FGF-2 DNA-mediated gene therapy in order to identify their effects in the healing of ischemic colon anastomoses and eliminating the negative effects of ischemia.

METHODS

Forty male Wistar albino rats weighing 250-280 g were divided into five equal groups (n = 8) as follows: group 1: control, ischemic left colonic anastomosis; group; 2: ischemic left colonic anastomosis with control plasmid delivery; group 3: ischemic left colonic anastomosis with VEGF plasmid delivery; group 4: ischemic left colonic anastomosis with FGF plasmid delivery; group 5: ischemic left colonic anastomosis with VEGF and FGF plasmid delivery. All rats were sacrificed on the 4th postoperative day. Anastomosis burst pressures were measured for mechanical examination of anastomosis. Tissue hydroxyprolin, VEGF and FGF levels were determined as biochemical parameters. Necrosis, epithelisation, inflammatory processes, fibroblastic activity, collagen deposition and neovascularisation at the anastomic site were studied.

RESULTS

VEGF, FGF and combined therapy significantly accelerated many of the histological parameters of healing, including fibroblast activation, collagen deposition, and angiogenesis, and augmented the levels of hydroxyproline and bursting pressure.

CONCLUSIONS

This is the first study to use gene therapy with growth factors for the healing of ischemic colonic anastomosis. This therapy can be effectively used in increasing ischemic anastomosis wound healing.

Hyperbaric oxygen therapy and mechanical resistence of the colonics anastomosis in rats with peritonitis

PURPOSE

To analyze the effects of hyperbaric oxygen therapy (HBO) on the mechanical resistance of anastomosis performed in rats' distal colon presenting peritonitis induced by ligature and cecal punction using the Total Energy Rupture biomechanical test (ETR).

METHODS

It was used 45 rats divided into three groups of 15 animals each. In Control Group (CG), it was performed anastomosis in distal colon without peritonitis. In Peritonitis Group (PG), it was performed anastomosis six hours after the induction of peritonitis by ligature and cecal punction. In Hyperbaric Chamber Group (HCG), it was performed six hours after the induction of peritonitis by ligature and cecal punction. The animals on CG and PG were kept at place air while the animals on HCG were placed on an experimental hyperbaric chamber in order to inhale oxygen at 100%, two absolute atmospheres, for 120 minutes, for four consecutive days. Euthanasia took place on the fifth day of the experiment. All the animals underwent to Total Energy Rupture Biomechanical Resistance test (ETR). Total Energy Rupture was defined as the necessary internal energy stored up to promote the colon rupture after an external traction force imposition.

RESULTS

The Peritonitis Group presents smaller average ETR than Control Group. There was no statistical difference between Peritonitis Group and Hyberbaric Chamber Group.

CONCLUSION

Hyperbaric oxygen therapy did not alter the mechanical resistance of anastomosis performed in distal colon of rats under the presence of peritonitis induced by ligature and cecal puncture.

Adrenomedulline improves ischemic left colonic anastomotic healing in an experimental rodent model

BACKGROUND

Leakage from colonic anastomosis is a major complication causing increased mortality and morbidity. Ischemia is a well-known cause of this event. This study was designed to investigate the effects of adrenomedullin on the healing of ischemic colon anastomosis in a rat model.

METHODS

Standardized left colon resection 3 cm above the peritoneal reflection and colonic anastomosis were performed in 40 Wistar rats that were divided into four groups. To mimic ischemia, the mesocolon was ligated 2 cm from either side of the anastomosis in all of the groups. The control groups (1 and 2) received no further treatment. The experimental groups (3 and 4) received adrenomedullin treatment. Adrenomedullin therapy was started in the perioperative period in group 3 and 4 rats (the therapeutic groups). Group 1 and group 3 rats were sacrificed on postoperative day 3. Group 2 and group 4 rats were sacrificed on postoperative day 7. After careful relaparotomy, bursting pressure, hydroxyproline, malondialdehyde, interleukin 6, nitric oxide, vascular endothelial growth factor, and tumor necrosis factor alpha levels were measured. Histopathological characteristics of the anastomosis were analyzed.

RESULTS

The group 3 animals had a significantly higher bursting pressure than group 1 (p<0.05). Hydroxyproline levels in group 1 were significantly lower than in group 3 (p<0.05). The mean bursting pressure was significantly different between group 2 and group 4 (p<0.05). Hydroxyproline levels in groups 3 and 4 were significantly increased by adrenomedullin therapy relative to the control groups (p<0.05). When all groups were compared, malondialdehyde and nitric oxide were significantly lower in the control groups (p<0.05). When vascular endothelial growth factor levels were compared, no statistically significant difference between groups was observed. Interleukin 6 and tumor necrosis factor alpha were significantly decreased by adrenomedullin therapy (p<0.05). The healing parameters and inflammatory changes (e.g., granulocytic cell infiltration, necrosis, and exudate) were significantly different among all groups (p<0.05).

CONCLUSION

Adrenomedullin had positive effects on histopathologic anastomotic healing in this experimental model of ischemic colon anastomosis.

Mesenchymal stem cells improve the healing of ischemic colonic anastomoses (experimental study)

OBJECTIVE

The goal of this study is to examine if allogenic mesenchymal stem cell (MSC) transplantation is a useful therapy for left ischemic colon anastomosis in rats. Problems with anastomosis healing may lead to serious postoperative complications. Bone marrow-derived mesenchymal stem cells (BM-MSCs), which are also referred to as stromal progenitor cells, are self-renewing and expandable stem cells. Recent studies have suggested that BM-MSCs play a crucial role in the processes of intestinal repair and accelerate angiogenesis.

METHODS

MSCs were isolated from rats before analysis by light and scanning electron microscopy. Forty male Wistar albino rats weighing 250-280 g were divided into four equal groups (n = 10) as follows: group 1: control, ischemic left colonic anastomoses (fourth day); group 2: control, ischemic left colonic anastomoses (seventh day); group 3: ischemic left colonic anastomoses + locally transplanted BM-MSCs (fourth day); group 4: ischemic left colonic anastomoses + locally transplanted BM-MSCs (seventh day). Histopathological features and anastomotic strength were evaluated.

RESULTS

BM-MSCs therapy significantly accelerated all of the healing parameters for ischemic colonic anastomosis except for inflammation on the fourth day. On the seventh day, BM-MSCs augmented the levels of the hydroxyproline and bursting pressure. Histological parameters, especially angiogenesis, were also found to be important for healing of ischemic colonic anastomoses.

CONCLUSIONS

This is the first study to use locally transplanted cell therapy for the healing of ischemic colonic anastomosis. BM-MSCs therapy significantly accelerated all of the healing parameters for ischemic colonic anastomosis.

Influence of omentoplasty on colonic anastomosis in animals submitted to hemorrhagic shock in rats

PURPOSE: To analyze influence of omentoplasty on anastomosis in descending colon of rats. Rats were submitted to the hypovolemic shock of the hemorrhagic type by the Biomechanical Test of Pressure of Rupture by Liquid Distension (BTPRLD). In addition, establish a type of acute anemia in rats that are provided to the study. METHODS: Comparative study between two groups of animals with ten rats in each one, all submitted to hemorrhagic shock for 30% volemic removal by the carotid artery. An anastomosis was performed in left colon. An anastomosis was performed in the left colon. Group 1 took place anastomosis with Polyvinyl Chloride (P.V.C) film to prevent the adhesions formation on sature line. Group 2 placed the great omentum around the anastomosis. Euthanasia occurred on the fifth day, when the anastomoses were submitted to the biomechanical test of pressure of rupture by liquid distension (BTPRLD). RESULTS: High rupture pressure was gained with omentoplasty group in relation to the group in which anastomosis was protected from adhesions formation. A statistical significance was noted. CONCLUSION: Protection by great omentum has increased the anastomosis resistance of the shocked animals. Also, the proposed hemorrhagic shock type has proven to be useful for this study.

Transient profound mesenteric ischemia strongly affects the strength of intestinal anastomoses in the rat

PURPOSE

Experimental data suggest that transient preoperative ischemia and reperfusion may compromise anastomotic strength. However, data on this subject are equivocal, in particular as to the onset and duration of this effect. This study was designed to comprehensively characterize the effects of profound transient intestinal ischemia on anastomotic healing during the first postoperative week.

METHODS

Ischemia was induced in rats by clamping both the superior mesenteric artery and ileal branches for 30 minutes. Immediately after declamping, anastomoses were constructed in both terminal ileum and descending colon. After three, five, or seven days, both bursting pressure and breaking strength were measured. Anastomotic collagen content, gelatinase activity, and histology were analyzed.

RESULTS

Anastomotic leakage rate was 13 percent in ischemia-reperfusion group and 0 percent (P=0.02) in controls. The breaking strength in ileum remained significantly (P<0.05) lower in the ischemic groups than in the control groups at all time points. Bursting pressure in the ileum was not significantly different between ischemic and control groups at either of the time points measured. However, at Day 7 the bursting site was significantly more frequent within the suture line in the ischemic groups. In the colon, at Day 3 the bursting pressure was 35 percent lower in the ischemic group than in the control group (P<0.05). Anastomotic collagen content and gelatinase activity were similar in ischemic and control groups.

CONCLUSIONS

Transient profound splanchnic ischemia compromises anastomotic strength throughout the entire first postoperative week. This effect does not seem to be caused by impaired accumulation of wound collagen.

Comparative study of the hyperbaric hyperoxygenation in ischemic colonic loops in rats

PURPOSE: To analyze and to evaluate the effect of the hyperbaric hyperoxygenation in the mechanical resistance of ischemic colon of rats. METHODS: Eighty rats, distributed in four groups of 20 animals in each one, were used. In group 1 (G1), the control group, ischemia was not caused. Group 2 was submitted to the lesser degree of ischemia. Group 3 was submitted to the intermediate degree of ischemia. In group 4, a bigger degree of intestinal ischemia was provoked. Each group was divided in two sub-groups of ten animals each: with hyperbaric chamber (CC) and without hyperbaric chamber (SC). The animals of the four CC subgroups were placed in an experimental hyperbaric chamber in order to inhale oxygen at 100%, at two Absolute Atmospheres, for 120 minutes, for a four-day consecutive period. The animals of the four SC subgroups were kept in environment air during the five days of the experiment. All animals have been submitted to the mechanical study of the intestinal loop by the pressure test of the rupture by liquid distension. The euthanasia occurred in the fifth post-operative day. RESULTS: Considering the ischemia factor, the four groups were different among them (p=0.0001). There was no statistical difference between subgroups CC and SC (p=0.3461). CONCLUSION: The hyperbaric oxygen-therapy did not present improvement on the induced ischemia in rats upright colic loop.

Ischemia and prolonged reperfusion before anastomotic construction do not reduce wound strength in the rat intestine

BACKGROUND

Under certain conditions, transient intestinal ischemia can reduce anastomotic strength. Preliminary findings suggest that prolonged reperfusion time, before anastomotic construction, results in reduced wound strength. The purpose of this study is to determine if wound strength indeed decreases with increasing duration of the interval between an ischemic period and construction of an anastomosis.

METHODS

In male Wistar rats, ischemia was induced by crossclamping the superior mesenteric artery (SMA) for 40 minutes. In control groups, the SMA was exposed but not clamped. Resection and anastomosis in both ileum and colon were performed immediately after release of the clamp or after 90 minutes or 24 hours. Both the anastomotic bursting pressure and breaking strength were measured after 3 or 5 days, together with hydroxyproline levels.

RESULTS

Neither bursting pressure nor breaking strength, either in ileum or in colon, changed significantly when the time between the end of ischemia and anastomotic construction increased. Similar values were obtained in all experimental and corresponding control groups. In the group in which anastomoses were constructed after 24-hour reperfusion, mechanical strength increased significantly from day 3 to day 5 and at the same rate as in the control group. No differences in anastomotic hydroxyproline levels were found between experimental and control groups analyzed at day 5.

CONCLUSIONS

A prolonged interval between intestinal ischemia and anastomotic construction does not affect development of early wound strength. Therefore, delayed anastomosis after transient ischemia is not likely to increase the risk of anastomotic complications.

Estudo comparativo da hiperoxigenação hiperbárica em alças cólicas isquêmicas em ratos

OBJETIVO: Analisar e avaliar os efeitos da hiperoxigenação hiperbárica na resistência mecânica do cólon isquêmico de ratos. MÉTODOS: Foram utilizados 80 ratos distribuídos em quatro grupos de 20 animais. No grupo 1, grupo controle, não se provocou isquemia. O grupo 2 foi submetido ao grau menor de isquemia. O grupo 3 foi submetido ao grau intermediário de isquemia. No grupo 4, provocou-se grau maior de isquemia intestinal. Cada grupo foi dividido em dois subgrupos de dez animais cada: com câmara hiperbárica (CC) e sem câmara hiperbárica (SC). Os animais dos quatro subgrupos CC foram colocados em uma câmara hiperbárica experimental para inalarem oxigênio a 100%, a duas atmosferas absolutas, durante 120 minutos, por quatro dias consecutivos. Os animais dos quatro subgrupos SC foram mantidos somente em ar ambiente. Todos animais foram submetidos ao estudo mecânico da alça intestinal pelo teste de pressão de ruptura pela distensão por líquido. A eutanásia ocorreu no quinto dia pós-operatório. RESULTADOS: Os quatro grupos são diferentes entre si considerando o fator isquemia (p= 0,0001). Não houve diferença estatística entre os subgrupos CC e SC (p= 0,3461). CONCLUSÃO: A oxigenoterapia hiperbárica não apresentou melhora sobre a isquemia induzida em alça cólica íntegra de ratos.