Development of a novel glucose polymer solution (icodextrin) for adhesion prevention: pre-clinical studies

Intra-abdominal adhesion formation causes significant post-operative morbidity. Controlled studies using animal models have been carried out to assess the tolerability and preventive efficacy of icodextrin solution (a biodegradable, biocompatible, glucose polymer). Reduction of adhesion formation was first evaluated in a rabbit double uterine horn model, applying 10-75 ml of 7.5 and 20%, or 50 ml of 2.5-20% icodextrin solution post-operatively. Significant increases in adhesion free sites (P < 0.005) were observed with volumes > or =25 ml, and at concentrations > or =4%. Efficacy of 50 ml 4 and 20% icodextrin was then evaluated both during and after surgery, demonstrating significant reductions in adhesion formation (P < 0. 002). In one study, intra- plus post-operative use of 4% icodextrin produced the greatest reduction of non-surgical site adhesions; in others, the post-operative effect was predominant. Post-surgical administration of 50 ml 4% icodextrin in a rabbit sidewall model also resulted in more adhesion-free animals, and a significant reduction (P < 0.001) in areas of adhesion formation and reformation. In a rat infection potentiation model, 4% icodextrin produced no difference in mortality, abscess formation or overall abscess score. These data suggest that 4% icodextrin offers a well-tolerated and effective means of reducing post-surgical adhesion formation.     

The effect of prostaglandins and aspirin--an inhibitor of prostaglandin synthesis--on adhesion formation in rats

The effect of intraperitoneal application of prostaglandins E2 and F2 alpha and of aspirin, a non-steroidal anti-inflammatory drug, on the formation of intraperitoneal adhesions was investigated in rats, in view of the main role of the body's reaction in adhesion formation. Intraperitoneal adhesions were induced by inflicting uniform trauma to the uterine serosa. It was demonstrated that prostaglandin E2 may increase adhesion formation and that intraperitoneal aspirin is able to inhibit its formation.     

Postoperative adhesion formation and reproductive outcome using Interceed after ovarian surgery: a randomized trial in the rabbit model

The efficacy of an oxidized regenerated cellulose barrier (Interceed) in reducing postoperative adhesion formation and improving reproductive outcome after ovarian surgery was evaluated in a prospective randomized trial. Twenty-nine New Zealand White female rabbits were submitted to a mid-line laparotomy and a standardized surgical incision was made on both ovaries. At random, one ovary was entirely wrapped in a sheet of Interceed, whereas the contralateral ovary was left uncovered. Four weeks following surgery, the rabbits were mated with a male of proven fertility. Two weeks later, a second-look laparotomy was performed by a blinded observer who evaluated the incidence and score of adhesions, the number of corpora lutea in each ovary, the number of embryos in the ipsilateral uterine horn and also calculated the nidation index for each side. Adhesions were observed in 66% of Interceed-covered and in 97% of control ovaries (P < 0.0001). The adhesion score on the Interceed side was significantly lower than on the control side. The nidation index for the Interceed side was significantly higher than for the control side. The authors conclude that, in the rabbit model, Interceed significantly reduces the incidence and score of postoperative ovarian adhesions and significantly improves reproductive outcome.      

The effect of training and duration of surgery on adhesion formation in the rabbit model

In order to evaluate the effect of training upon postoperative adhesions, standard bipolar and mechanical, nonopposing injuries were performed in the uterine horns and side walls of 52 mature female rabbits using a conventional three-puncture laparoscopy, by an endoscopic surgeon with limited experience. An additional injury, either bipolar or mechanical or both, was performed in the retro- uterine space. With experience, the duration of surgery decreased progressively from 12 +/- 2 to 8 +/- 1 min in the first and last 10 animals respectively. The amount of perioperative bleeding was not affected by experience. With experience the postoperative adhesions decreased in extent (P = 0.0001), tenacity (P = 0.004), type (P = 0.002) and inflammation (P = 0.003) and for total score (P = 0.0002). These changes were correlated with the briefer duration of surgery but not with the amount of perioperative bleeding. The strong correlations of adhesion scores in the pouch of Douglas, and around both uterine horns confirmed the importance of the inter-animal variability in making adhesions. By logistic regression, the adhesions in the pouch of Douglas were explained simultaneously by the adhesions on the uterine horns (P = 0.0004, thus correcting for inter-animal variability) by the amount of bleeding (P = 0.01) and the duration of surgery (P = 0.05). No major differences were found in adhesions following a mechanical or a bipolar injury or following such a lesion in the pouch of Douglas or at the uterine horns. In conclusion, experience, expressed by the duration of surgery and to a lesser extent perioperative bleeding, is a major co-factor in postoperative adhesions, suggesting that duration of surgery should be strictly standardized in endoscopic adhesion studies. The important inter-animal variability can be circumvented by using a standard control lesion, making each animal its own control.      

Localized prevention of postsurgical adhesion formation and reformation with oxidized regenerated cellulose

We evaluated oxidized regenerated cellulose (ORC) in experimental rabbit and dog models to assess its potential for reducing or preventing adhesion formation and reformation. Evaluation was performed in the following anatomical sites: uterine horn trauma; small bowel resection and anastomosis; parietal peritoneum excision; and adhesion reformation in the uterine horn. Ten to 14 days after ORC treatment, adhesion formation was macroscopically and microscopically evaluated. Results demonstrate that ORC produced graded reduction in adhesion formation and significantly prevented adhesion reformation.     

Postoperative adhesion prevention with low-dose aspirin: effect through the selective inhibition of thromboxane production

The aim of the present study was to evaluate the efficacy of low-dose versus high-dose aspirin in the prevention of postoperative adhesion formation. Forty New Zealand White rabbits were randomized into three groups: low-dose aspirin (1.7 mg/kg per day for 5 days starting on the day of surgery), high-dose aspirin (28.0 mg/kg per day), and controls. The rabbits underwent a standardized surgical injury on the ovary, uterine horn and abdominal wall on one side at laparotomy. On postoperative day 21, a second-look laparotomy was performed for the evaluation of postoperative adhesions. In five animals in each group, peritoneal fluid samples were collected at initial surgery, then through an additional 2 cm incision performed on postoperative day 3, and at second-look laparotomy. The peritoneal concentrations of thromboxane B2 and 6-keto-prostaglandin F1alpha (the stable hydrolysis product of prostacyclin) were measured by radioimmunoassay. At second- look laparotomy, the adhesion formation rate was 46% in the low-dose aspirin group, 77% in the high-dose group, and 100% in the control group. The adhesion score in the low-dose group was significantly lower (P < 0.01) than in the high-dose and control groups. Peritoneal thromboxane decreased significantly during treatment in both low-dose and high-dose aspirin groups, whereas prostacyclin decreased only in the high-dose group. Postoperative adhesion reduction observed in this study with low-dose aspirin treatment could be due to the selective inhibition of thromboxane over prostacyclin production.      

The effect of rosiglitazone in the prevention of intra-abdominal adhesion formation in a rat uterine horn model

BACKGROUND: Effects of rosiglitazone in the prevention of adhesion formation were evaluated. METHODS: Eighty Wistar albino rats were randomly grouped into eight equally sized groups. A 2-cm segment of the antimesenteric surface of the right uterine horn was traumatized to form a standardized lesion, using bipolar cautery. A dose-response study was performed with 0.1, 0.3, 1 and 3 mg/kg/day rosiglitazone. Fifteen days later, adhesions were evaluated clinically and histopathologically. A time-response study was performed with 1 mg/kg/day rosiglitazone (the minimum dose found to significantly affect adhesion formation). Rosiglitazone was given for 7 days post-operatively and results were compared with those of control and the 15-day group (time-response). In all these studies, rosiglitazone was orally administered 3 days before the operation and continued post-operatively. In two further experimental groups, rosiglitazone was only administered pre-operatively or post-operatively. RESULTS: Approximately 1 mg/kg/day rosiglitazone was found to reduce adhesion scores both clinically and histopathologically. Duration of treatment was also found to affect the extent of adhesion formation. However, giving rosiglitazone either just pre-operatively or post-operatively did not significantly reduce adhesion formation. CONCLUSION: Rosiglitazone with peroxisome proliferator-activated receptor (PPAR)-gamma agonist activity reduced the formation of i.p. adhesion possibly by reducing the initial inflammatory response and the subsequent exudation in this study.     

Cross-linked hyaluronate hydrogel prevents adhesion formation and reformation in mouse uterine horn model

The aim of this study was to evaluate the efficacy of cross-linked hyaluronate hydrogel (HA gel) as an adjuvant for postoperative adhesion prevention, in a mouse uterine horn model. In experiment 1 uterine horns were abrased with iodine. HA gel was applied to the injured surface before closure in the treatment group. In experiment 2, after injuring the uterine horns, three stitches were placed at equal distances around the uterine horns to appose the injured medial surfaces of the two horns during healing. HA gel was inserted between the uterine horns in the treatment group. In experiment 3 prevention of adhesion reformation was assessed. After lysis of adhesions that were induced as in experiment 2, HA gel was introduced between the serosal surfaces of apposing uterine horns. Untreated animals served as controls in each experiment. Statistical analysis was carried out using Student's t-test. The adhesion score was significantly lower in the HA gel group on the 14th day compared with controls in all the experiments: in experiment 1, 0.3 +/- 0.4 versus 1.7 +/- 1.2; in experiment 2, 0.9 +/- 1.0 versus 2.6 +/- 0.5; and in experiment 3, 1.5 +/- 0.9 versus 2.2 +/- 0.6 respectively. Cross-linked HA gel significantly reduced de-novo adhesions (P< 0.03) and adhesion reformation (P < 0.03).     

A systemic review of randomized controlled studies about prevention with pharmacologic agents of adhesion formation in the rat uterine horn model

Introduction

Evaluation of treatment attempts in postoperative adhesion formation is pivotal for the prevention of several morbidities including infertility, pelvic pain, bowel obstruction, and subsequent intraoperative complications. The purpose of this systemic review was to assess the literature on the rat uterine horn model for adhesion formation and treatment modalities to prevent adhesion in the most frequently used experimental animal model.

Material and methods

We performed a systemic review of publications from January 1^st 2000 to December 31^st 2013 via a PubMed search. A high number of agents were evaluated for the prevention of postoperative adhesion formation in the rat uterine horn model.

Results

According to most of the studies, adjuvants such as antiinflamatuars, antiestrogens, antioxidants were effective to prevent adhesion formation.

Conclusions

Prevention of adhesion formation is pivotal and numerous types of agents were described in the literature were summarized in this review.     

Comparison of hyaluronate/carboxymethylcellulose membrane and melatonin for prevention of adhesion formation in a rat model

BACKGROUND: To investigate the effectiveness of melatonin in preventing post-operative adhesion formation and to compare it with the efficacy of hyaluronate/carboxymethylcellulose membrane in a rat model. MATERIALS and METHODS: Following pilot studies, 35 rats were operated on in the full study. In 15 animals (group one), 10 standard lesions were inflicted in each uterine horn (total 30 horns) and melatonin was applied before closure of the abdomen. In the second group, 20 animals were operated on and one of the uterine horns (total 20 horns) with standard lesions was treated with hyaluronate/carboxymethylcellulose membrane and the other uterine horn served as a control. Second-look operations were performed 1 week later and adhesion scores were compared. RESULTS: The adhesion scores of uterine horns treated with melatonin and of uterine horns treated with hyaluronate/carboxymethylcellulose membrane were significantly lower than the scores of the controls (P < 0.001). There was no statistically significant difference between the adhesion scores of uterine horns treated with melatonin and of uterine horns treated with hyaluronate/carboxymethylcellulose membrane (P > 0.05). CONCLUSIONS: Both melatonin and hyaluronate/carboxymethylcellulose membrane were effective in prevention of adhesion formation in a rat uterine horn model.     

Prevention of abdominal adhesion formation by thermosensitive PECE-hydrogel in a rat uterine horn model

In this work, we investigated the efficacy of PECE-hydrogel in preventing postsurgical peritoneal adhesions in the rat uterine horn model. Standardized surgical traumas were applied to the peritoneum of the abdominal wall and the uterine horns. PECE hydrogel was applied to the two wound surfaces. Animals were euthanized at different times after surgery, and the gross necropsy findings were documented. Adhesion formation was assessed according to adhesion extent and adhesion severity, and the hydrogel degradation and healing of peritoneal wounds were observed. The remesothelialization was dynamically observed by scanning electron microscope. The results showed that none of the animals in the hydrogel-treated group (n = 12) developed adhesion. In contrast, all untreated animals (n = 12) had adhesions that could only be separated by sharp dissection (p < 0.001). The hydrogel could adhere to the peritoneal wounds and gradually disappear from the wounds within 7-9 days and transformed into viscous fluid being completely absorbed within 12 days. The injured parietal and visceral peritoneum was remesothelialized in about 7 and 9 days, respectively. This work confirmed that PECE hydrogel holds promise as a novel absorbable biomaterial for the reduction of postoperative adhesions after laparotomy.     

Prevention of post-surgical adhesion formation using aspirin in a rodent model: a preliminary report

Pelvic adhesions are one of the major factors which significantlyand adversely affect surgery outcome due to intra-and postoperativemorbidity and reduce future female fertility. Using a rodentmodel, we evaluated the efficacy of aspirin, a non-steroidalanti-inflammatory drug, in the prevention of adhesion formation.A total of 72 female Wistar rats received a standardized primarytraumatic lesion to the right uterine horn. They were randomlydivided into eight groups: group I (control) had no treatmentand group II received a single pre-operative 0.70 mg aspirin.All the succeeding groups (III-VIII) received aspirin in dosesof 0.35, 0.70, or 1.40 mg every 6 h for either 48 or 96 h inaddition to the pre-operative aspirin (0.70 mg). All animalswere killed 4 weeks later and adhesions were assessed usinga modified adhesion scoring scale. The lowest adhesion scorewas found in the group treated with 0.35 mg of aspirin for 96h, and the highest was found among the groups treated with either0.70 or 1.40 mg for 48–96 h respectively (P < 0.05).These results are in line with the hypothesis that administrationof a low dose of aspirin selectively inhibits the productionof thromboxane A₂, whereas basal prostacyclin biosynthesis ispreserved. This phenomenon might contribute to reducing postoperativeadhesion formation in a rat model. Thus, future studies intothe prevention of adhesion formation may require the additionaluse of a non-steroidal anti-inflammatory drug, for which aspirindeserves further attention, before extrapolation into humantherapy.     

Biodegradable and injectable in situ cross-linking chitosan-hyaluronic acid based hydrogels for postoperative adhesion prevention

Postsurgical peritoneal adhesions are very common and serious complication after surgery. Biodegradable and injectable hydrogels derived from natural polysaccharides are ideal biomaterials for prevention of postoperative adhesion. In this work, we report a class of injectable, biodegradable, and non-toxic hydrogel derived from N, O-carboxymethyl chitosan (NOCC) and aldehyde hyaluronic acid (A-HA), without requirement of any chemical linkers or radiant light sources. NOCC was prepared by introducing carboxymethyl groups to the N-position and the O-position of chitosan, and A-HA was prepared using periodate oxidation method. The gelation is attributed to the Schiff base between the amino groups of NOCC and aldehyde groups in A-HA, and the hydrogel precursors cross-linked to form a flexible hydrogel. NOCC, A-HA, and NOCC/A-HA hydrogel extract exhibited very low cytotoxicity and hemolysis, and the acute toxicity tests showed that the hydrogel was non-toxic. Besides, the highly porous three-dimensional hydrogel can supported the growth and proliferation of the cells encapsulated in the hydrogels, but was not favorable for the attachment of fibroblasts to the surface, suggesting that the NOCC/A-HA hydrogel can be developed for adhesion prevention. The hydrogel was susceptible to the lysozyme and can be degraded within 2 weeks in vivo. Furthermore, we employed a rat model of sidewall defect-cecum abrasion to investigate the efficacy of NOCC/A-HA hydrogel in preventing post-operative peritoneal adhesions. A significant reduction of peritoneal adhesion formation was found in the NOCC/A-HA-treated group, compared with commercial hyaluronic acid (HA) hydrogel group and normal saline group. In addition, the potential anti-adhesion mechanism of NOCC/A-HA hydrogel was discussed, which may attribute to the combination of barrier function and bioactivity of NOCC and A-HA.     

Influence of nicotine and caffeine on skeletal development in the rat

The effects of nicotine and caffeine at dose levels approximating human consumption on skeletal development was investigated in Sprague-Dawley rats. One group of animals received nicotine administered subcutaneously by an Alzet miniosmotic pump from gestational d 6 through 12 (25 mg over 7 d; rate 149 micrograms/h). Control animals received physiological saline in a similar manner. A2. group received a single intravenous injection of caffeine (25 mg/kg) on gestational d 6. Control animals were treated with physiological saline. A further group received both nicotine and caffeine on gestational d 6 as described for the 2 previous groups. Evaluation of the fetal skeletal system on gestational d 20 revealed a significant decrease in the number of complete sternal ossification centers, as well as delays in the ossification of the skull and face, following combined nicotine and caffeine treatment. Other skeletal anomalies and variations were frequently observed, but their incidences were not significantly increased in any of the treatment groups, compared to the corresponding controls. A coteratogenic effect is evident between nicotine and caffeine on account of the increased incidence of delayed and abnormal skeletal development.     

Adhesion preventive effect of hyaluronic acid after intraperitoneal surgery in mice.

Prevention of intraperitoneal adhesion after gynaecological surgery is essential for maintaining postoperative fertility. In this study, the adhesion prevention effect was examined of a hyaluronic acid (HA) solution obtained from the fermentation method and having a molecular weight of 1.9x10(6) with high viscosity. Laparotomy was conducted on female mice 7 weeks old, whose menstrual periods were synchronized by pregnant mare serum gonadotrophin (PMSG) to injure the uterine horn surface. Intraperitoneal adhesions were favourably formed in 91.7% of cases induced with iodine abrasion, compared with 50% induced by electrosurgery. Intraperitoneal administration of HA was evaluated for its effect on the prevention of adhesions made by iodine abrasion. Adhesion prevention effects of HA were observed at concentrations of 0.3, 0.5, 0.75 and 1.0%, among which the most pronounced effect was with the use of a 0.3% solution (92.3% of cases). Compared with the control group adhesion score of 2.0 +/- 0. 8, significant decreases in adhesion scores were observed at all concentrations. HA with a molecular weight of 1.9x10(6) was recognized to have a definitive prevention effect on postoperative adhesions in mice after laparotomy and is considered to be a prospective material for future clinical use.     

Adhesion formation to hemostatic agents and its reduction with a sodium hyaluronate/carboxymethylcellulose adhesion barrier

The impact of hemostatic agents on postoperative adhesion formation has not been well studied. We hypothesized that hemostatic agents would be a significant nidus for adhesion formation and that a resorbable barrier would effectively reduce adhesions to hemostatic agents. Four commercial hemostatic agents, each composed of a different biomaterial matrix, were implanted in female Sprague-Dawley rats, and adhesion formation was examined 7 days after surgery. In separate studies, the effects of serosal trauma (via cecal abrasion), added blood, and the presence of chemically modified sodium hyaluronate/carboxymethylcellulose (HA/CMC) barrier on adhesion formation to hemostatic agents were studied. Significant adhesions formed to hemostatic agents even in the absence of traumatized tissue. When applied after cecal abrasion, the incidence of adhesions to the hemostatic agents increased. Addition of blood to this model increased adhesion formation even further, causing adhesions in every animal in the study. An HA/CMC adhesion barrier reduced adhesions to hemostatic agents in the presence of serosal trauma and maintained effectiveness even in the presence of blood. In conclusion, hemostatic agents potentiated adhesion formation at the site of application in a model without trauma. In more challenging models, their adhesiogenic contribution was overwhelmed by trauma and blood. HA/CMC adhesion barrier applied over hemostatic agents at the time of surgery provided significant protection against postoperative adhesions in these preclinical models.     

Prevention of postoperative adhesion formation in rat uterine horn model by nimesulide: a selective COX-2 inhibitor

BACKGROUND: Pelvic surgery is one of the main causes of intraperitoneal (i.p.) adhesions that create various medical problems including pelvic pain, bowel obstructions and female infertility. A rat model was used to investigate the efficacy of nimesulide, a selective cyclooxygenase-2 inhibitor, in the prevention of adhesion formation. METHODS: Fifty Wistar-Albino rats underwent bilateral uterine horn injury with a unipolar cautery. Study groups were as follows: (i) control group, no adjuvant therapy; (ii) i.p. Ringer's lactate group, 2 ml Ringer's lactate solution was instilled i.p.; (iii) i.p. Ringer's lactate plus nimesulide group, 1 ml Ringer's lactate plus 1 ml nimesulide (0.5 mg/ml) were given i.p.; (iv) intramuscular (i.m.) nimesulide group, 1 ml i.m. nimesulide (0.5 mg/ml) was given preoperatively for 5 days; and (v) i.p. nimesulide group, 1 ml nimesulide (0.5 mg/ml) was instilled i.p. At the end of the study all animals were killed, and a standard adhesion scoring system was applied by a blinded examiner. RESULTS: The mean adhesion extent in study groups was as follows: 1.33 +/- 0.76 in control group, 1.40 +/- 0.90 in i.p. Ringer's lactate group, 0.75 +/- 0.70 in i.p. Ringer's lactate plus nimesulide group, 0.25 +/- 0.44 in i.m. nimesulide group and 0.31 +/- 0.70 in i.p. nimesulide group. The mean +/- SD adhesion severities of control, i.p. Ringer's lactate, i.p. Ringer's lactate plus nimesulide, i.m. nimesulide, and i.p. nimesulide groups were 0.58 +/- 0.35, 0.30 +/- 0.41, 0.27 +/- 0.3, 0.12 +/- 0.28 and 0.15 +/- 0.35 respectively. The lowest adhesions were found in the groups treated with nimesulide i.m. and nimesulide i.p. ( P < 0.05). CONCLUSIONS: This study showed that preoperative i.m. or postoperative i.p. administration of nimesulide to the site of injury reduced the formation of postoperative adhesions in a rat uterine horn model.     

Prevention of Pleural Adhesions by Bioactive Polypeptides - A Pilot Study

Objective: Postoperative pleural adhesions lead to major problems in repeated thoracic surgery. To date, no antiadhesive product has been proven clinically effective. Previous studies of differently charged polypeptides, poly-L-lysine (PL) and poly-L-glutamate (PG) have shown promising results reducing postoperative abdominal adhesions in experimental settings. This pilot study examined the possible pleural adhesion prevention by using the PL+PG concept after pleural surgery and its possible effect on key parameters; plasmin activator inhibitor-1 (PAI-1) and tissue growth factor beta 1 (TGFb) in the fibrinolytic process.Methods: A total of 22 male rats were used in the study, one control group (n=10) and one experimental group (n=12). All animals underwent primary pleural surgery, the controls receiving saline in the pleural cavity and the experimental group the PL+PG solution administered by spray. The animals were evaluated on day 7. Macroscopic appearance of adhesions was evaluated by a scoring system. Histology slides of the adhesions and pleural biopsies for evaluation of PAI-1 and TGFb1 were taken on day 7.Results: A significant reduction of adhesions in the PL+PG group (p<0.05) was noted at day 7 both regarding the length and severity of adhesions. There were no significant differences in the concentration of PAI-1 and TGFb1 when comparing the two groups.Conclusions: PL+PG may be used to prevent pleural adhesions. The process of fibrinolysis, and fibrosis was though not affected after PLPG administration.     

Early alterations of lung injury following acute smoke exposure and 21-aminosteroid treatment.

In a simulated fire-related smoke exposure protocol, New Zealand white rabbits were utilized to investigate the potential effects of the 21-aminosteroid (lazaroid) analog U75412E on the early events of acute lung injury. Inhalation of a total of 1.6 mg/kg U75412E aerosolized at a rate of 1.53 mg/min at 0.5 hr after smoke exposure significantly attenuated the extent of lung injury at 1 hr, as evidenced by decreased bronchoalveolar lavage (BAL) concentration of total protein, 6-keto-prostaglandin F1-alpha, and blood gas defect. Histopathologic examination demonstrated that the lazaroid significantly attenuated smoke-induced lung injury as evidenced by a decrease in wet lung/body weight ratio, necrosis, and sloughing of airway epithelial cells. Electron microscopy showed that the lazaroid decreased smoke-induced interstitial edema and the vacuolization of alveolar type II epithelium (21.6 +/- 9.7 vs 8.5 +/- 3.6 vacuoled blebs/cell, smoke only vs smoke + lazaroid). However, U75412E did not attenuate smoke-induced changes in BAL concentration of tumor necrosis factor-alpha, total cell count, and granulocyte percentage. These observations suggest that U75412E may exert its action through cooperative mechanisms, such as the modulation of arachidonic acid metabolism, in addition to its characterized antioxidative effects.