Development of a standardized laparoscopic caecum resection model to simulate laparoscopic appendectomy in rats

Laparoscopic lavage in a purulent peritonitis model: impact on inflammatory proteins

BACKGROUND

Laparoscopic lavage is an effective, safe, and feasible treatment in patients with perforated diverticulitis with purulent peritonitis. Laparoscopic lavage was introduced without any detailed knowledge regarding the mechanisms of action. The aim of this study was to validate the reproducibility of an animal model of purulent peritonitis and to study the effect of laparoscopic lavage on inflammatory proteins in this model.

METHODS

Forty rats, divided into eight groups (n = 5) were operated. Six groups underwent cecal ligation and puncture (CLP) causing peritonitis and two groups underwent sham surgery. Three CLP and one sham group received laparoscopic lavage, while the remaining groups acted as time-matched controls. Samples of abdominal fluid and blood were collected after 1, 2 or 3 h and analyzed regarding 92 inflammatory proteins using Olink Target 96 Mouse exploratory panel.

RESULTS

Animals with peritonitis had higher levels of inflammatory proteins such as CCL3, IL17A and IL6 in abdominal fluid and serum compared to sham. The groups treated with laparoscopic lavage had lower levels of inflammatory proteins in both abdominal fluid and serum compared with untreated peritonitis groups, results were most distinct sampled after one hour.

CONCLUSION

Our animal model is reproducible, and mimics perforated diverticulitis with purulent peritonitis with increased levels of inflammatory proteins in abdominal fluid and serum. The levels of several inflammatory proteins were lower following laparoscopic lavage treatment perhaps indicating the physiological effect of laparoscopic lavage. This model can be used to further explore the mechanisms involved in peritonitis and laparoscopic lavage treatment.

The cecal appendix is correlated with greater maximal longevity in mammals

The cecal appendix had been considered as a useless vestige since Darwin's work, but recent research questioned this idea demonstrating that the cecal appendix appeared among the mammals at least 80 million years ago and has made multiple and independent appearances without any obvious correlation with diet, social life, ecology, or size of the cecum. However, functions and probable selective advantage conferred by this anatomical structure still remain enigmatic. We found, through analyses of data on 258 mammalian species, that cecal appendix presence is correlated with increased maximal observed longevity. This is the first demonstration of a correlation between cecal appendix presence and life history. Interestingly, the classical evolutionary theory of aging that predicts an increased longevity when the extrinsic mortality is reduced has been questioned several times, but recent comparative studies asserted its validity in the taxa, which experience age-dependent and density-dependent mortality, as in mammals. Thus, the cecal appendix may contribute to the increase in longevity through a reduction of extrinsic mortality. A lower risk of fatal infectious diarrhea is one of the most plausible hypotheses that could explain it. However, several hypotheses coexist about the possible functions of the cecal appendix, and our results provide new insights about this much-disputed question. In addition, we show that the cecal appendix arose at least 16 times and was lost only once during the evolutionary history of the considered mammals, an asymmetry that supports the existence of a positive selective of this structure.

Impact of sleeve gastrectomy and dietary change on metabolic and hepatic function in an obesity rat model - Experimental research

PURPOSE

Sleeve gastrectomy (SG) is an effective procedure to treat morbid obesity. SG induces remission of type 2 diabetes and metabolic syndrome and improves non-alcoholic fatty liver disease (NAFLD). However, it is imperative to clarify the extent to which these beneficial effects may be attributed to SG among other concomitant changes including postoperative diet. The current study addresses this question in a rodent model of obesity by subjecting it to SG, normal diet, or a combination of the two.

METHODS

Male Wistar-rats were fed with either high fat diet (HF, n = 32) or received chow diet (CD, n = 8). After 15 weeks, the HF-fed rats underwent either SG or sham operation, following which they were randomised to either continue HF or switched to CD for another 6 weeks. Body weight, fasting blood glucose level, blood pressure, and adipokine expression (leptin, adiponectin, MCP-1) in the adipose tissue along with triglycerides level in the blood serum were assessed to evaluate metabolic function. Hepatic function was assessed by histological evaluation of liver fibrosis (Hydroxyproline, Sirius Red) and reverse transcription polymerase chain reaction (RT-PCR) of the inflammation marker monocyte chemoattractant protein-1 (MCP-1).

RESULTS

Postoperative dietary change improved adipose tissue inflammation and arterial blood pressure regardless of the surgical intervention, while SG improved hyperglycaemia, blood triglyceride levels and, regardless of the postoperative diet, hepatic inflammation and fibrosis. However, combined administration of SG with post-operative normal diet was the most effective with regard to reducing the body weight.

CONCLUSION

HF for 15 weeks induced obesity with metabolic syndrome and NAFLD in rats. SG and dietary intervention improved metabolic state and NAFLD; however, their combination was significantly more effective.

Cecal Resection with Bipolar Sealing Devices in a Rat Model

Background: Bipolar sealing devices are routinely used to seal blood vessels. The aim of the study is to evaluate the feasibility and safety of colonic sealing with the use of the bipolar energy devices in rats as model for experimental appendectomy. Methods: Seventy-five male Wistar rats underwent a cecal resection with four different bipolar sealing devices or a linear stapler. The harvesting procedure was performed immediately or at postoperative day (POD) 7. The sealing front bursting pressure (BP) was measured in both groups. At POD7, the resection line was clinically examined and the hydroxyproline (HDP) levels were determined. Hematoxylin and Eosin (H&E) staining was used for histopathological evaluation of the sealing front as well. Results: There was no mortality and no insufficiency. The BPs between the bipolar sealing devices showed no statistical differences. The early phase of the seal (POD 0) provides a low BP with an 30.8% increase until POD 7. The BPs in the stapler group showed significant better values. The hydroxyproline levels did not differ statistically between the groups. Histopathologically, there were more signs of ischemic necrosis in the stapler group than in the sealing devices groups. Conclusion: The resection and sealing of the cecum as an experimental appendectomy model with the use of bipolar energy devices proved feasible and safe in rats. The different energy devices in this study produce comparable results. To justify clinical practice in humans, several studies on the underlying mechanisms of early stage wound healing are needed.

A Novel Laparoscopic Surgery Model with a Device to Expand the Abdominal Working Space in Rats: The Influence of Pneumoperitoneum and Skin Incision Length on Postoperative Inflammatory Cytokines

PURPOSE

Experimental models of laparoscopic surgery generally use large animals owing to a sufficient abdominal working space. We developed a novel laparoscopic surgery model in rats. We performed intestinal anastomosis to demonstrate the feasibility and reliability of this model.

MATERIALS AND METHODS

We designed a device for rats that expanded the abdominal working space and allowed us to manipulate the intraperitoneal organs by hand under direct vision with pneumoperitoneum. We performed small bowel resection and intestinal anastomosis in rats using this model. To elucidate the effects of pneumoperitoneum and skin incision length, rats were randomly divided into four groups with differing surgical techniques: small incision group, large incision group, small incision + pneumoperitoneum group, and large incision + pneumoperitoneum group. Intraoperative abdominal pressure and postoperative cytokines were measured.

RESULTS

One experimenter completed small bowel resection and hand-sewn anastomosis under direct vision without any difficulties or assistance. Carbon dioxide pneumoperitoneum was maintained at 8-10 mmHg during surgery in both pneumoperitoneum groups. Necropsies revealed no evidence of anastomotic leakage at 24 h after surgery. The interleukin-6 and C-reactive protein concentrations were significantly greater in large incision group than in small incision group, but were not significantly different between small incision + pneumoperitoneum group and small incision group. These cytokines concentrations were the greatest in large incision + pneumoperitoneum group.

CONCLUSIONS

Our laparoscopic surgery model in rats is a simple and reliable experimental model. The length of skin incision might be a more influential determinant of surgical invasiveness than pneumoperitoneum.

Advantages of laparoscopic compared to conventional surgery are not related to an innate immune response of peritoneal immune activation: an animal study in rats

PURPOSE

Laparoscopic surgery (LS) has proved superior compared to conventional surgery (CS) regarding morbidity, length of hospital stay, rate of wound infection and time until recovery. An improved preservation of the postoperative immune function is assumed to contribute to these benefits though the role of the local peritoneal immune response is still poorly understood. Our study investigates the peritoneal immune response subsequent to abdominal surgery and compares it between laparoscopic and conventional surgery to find an immunological explanation for the clinically proven benefits of LS.

METHODS

Wistar rats (N = 140) underwent laparoscopic cecum resection (LCR; N = 28), conventional cecum resection (CCR; N = 28), laparoscopic sham operation (LSO; N = 28), conventional sham operation (CSO; N = 28), or no surgical treatment (CTRL; N = 28). Postoperatively, peritoneal lavages were performed, leukocytes isolated and analyzed regarding immune function and phagocytosis activity.

RESULTS

Immune function was inhibited postoperatively in animals undergoing LCR or CCR compared to CTRL reflected by a lower TNF-α (CTRL 3956.65 pg/ml, LCR 2018.48 pg/ml (p = 0.023), CCR 2793.78 pg/ml (n.s.)) and IL-6 secretion (CTRL 625.84 pg/ml, LCR 142.84 pg/ml (p = 0.009), CCR 169.53 pg/ml (p = 0.01)). Phagocytosis was not affected in rats undergoing any kind of surgery compared to CTRL. Neither cytokine secretion nor phagocytosis activity differed significantly between laparoscopic and conventional surgery.

CONCLUSIONS

According to our findings the benefits associated with LS compared to CS cannot be explained by differences in the postoperative peritoneal innate immune response. Further studies are needed to elucidate the causes for a more favorable postoperative outcome in patients after LS compared to CS.

Cytokine expression in the visceral adipose tissue after laparoscopic and conventional surgery in a rodent model

Background

Laparoscopic Surgery has become a worldwide standard procedure for a variety of indications. This has been attributed to a milder postoperative inflammatory response by the innate immune system potentially mediated through immune mediators released by the visceral adipose tissue (VAT). However, an in vivo experimental evidence is lacking and is the issue of our present study.

Methods

Male Wistar rats (N = 24) underwent standardized surgical procedures of conventional cecum resection (CCR), conventional sham operation, laparoscopic cecum resection (LCR), or laparoscopic sham operation. Cytokine expression of leptin, resistin, and IL-6 was analyzed in VAT before and after resection by quantitative RT-PCR.

Results

Postoperative leptin gene expression was reduced in the CCR and LCR groups, while expression was not significantly affected in both sham groups compared to the preoperative levels. In contrast, IL-6 expression was not affected in the LCR group, but was significantly elevated in the CCR cohort. The IL-6 expression was significantly higher in CCR compared to LCR. Resistin expression levels did not differ between all groups.

Conclusions

Our study underlines the role of immunological involvement of VAT in the postoperative phase. Low leptin levels seem to act as a stimulator for energy uptake in order to cope with postoperative stress. A lower IL-6 expression in the LCR compared to the CCR group may indicate a weaker inflammatory activity potentially adding to the clinical benefits observed in patients undergoing LS.