Modulation of peritoneal re-epithelialization by postsurgical macrophages

Post-Operative Adhesions: A Comprehensive Review of Mechanisms

Post-surgical adhesions are common in almost all surgical areas and are associated with significant rates of morbidity, mortality, and increased healthcare costs, especially when a patient requires repeat operative interventions. Many groups have studied the mechanisms driving post-surgical adhesion formation. Despite continued advancements, we are yet to identify a prevailing mechanism. It is highly likely that post-operative adhesions have a multifactorial etiology. This complex pathophysiology, coupled with our incomplete understanding of the underlying pathways, has resulted in therapeutic options that have failed to demonstrate safety and efficacy on a consistent basis. The translation of findings from basic and preclinical research into robust clinical trials has also remained elusive. Herein, we present and contextualize the latest findings surrounding mechanisms that have been implicated in post-surgical adhesion formation.

Prevention of Post-Operative Adhesions: A Comprehensive Review of Present and Emerging Strategies

Post-operative adhesions affect patients undergoing all types of surgeries. They are associated with serious complications, including higher risk of morbidity and mortality. Given increased hospitalization, longer operative times, and longer length of hospital stay, post-surgical adhesions also pose a great financial burden. Although our knowledge of some of the underlying mechanisms driving adhesion formation has significantly improved over the past two decades, literature has yet to fully explain the pathogenesis and etiology of post-surgical adhesions. As a result, finding an ideal preventative strategy and leveraging appropriate tissue engineering strategies has proven to be difficult. Different products have been developed and enjoyed various levels of success along the translational tissue engineering research spectrum, but their clinical translation has been limited. Herein, we comprehensively review the agents and products that have been developed to mitigate post-operative adhesion formation. We also assess emerging strategies that aid in facilitating precision and personalized medicine to improve outcomes for patients and our healthcare system.

Peritoneal adhesions in human and veterinary medicine: from pathogenesis to therapy. A review

Any peritoneal inflammatory process consequent to infections or surgical injuries may induce abdominal adhesion formation. Peritoneal adhesions are connective laciniae that develop among abdomino-pelvic organs that limit physiologic visceral motion. Consequently, fertility may be impaired, and intestinal obstruction and pelvic pain may develop, mainly in subjects that had undergone gynaecological surgery. This review illustrates the pathogenic steps of adhesiogenesis and the therapeutic scenario that evolved over the years to tackle the threat of peritoneal adhesions, both in domestic animals and in women.

Intraperitoneal recombinant interleukin-2 activates leukocytes in rat endometriosis

The aim of this double-blinded study was to determine changes in leukocyte populations in blood, peritoneal lavage fluid, eutopic and ectopic endometrium after treatment with recombinant rat interleukin-2 (IL-2) using an in vivo experimental model of rat endometriosis. The in vivo model involved transplanting four square fragments of autologous endometrium onto the inner surface of the abdominal wall in 20 Wistar rats. The control group was constituted by 20 sham-operated rats. Both groups were randomly treated (1-month interval treatment) with 2 intraperitoneal doses of glucose solution (5%) that did or did not contain recombinant IL-2, and animals were sacrificed 4 weeks after the last dose of treatment. Blood and peritoneal lavage were obtained during the initial and final laparotomy, whereas eutopic and ectopic endometrium were collected at the end of the experiment. Endometriotic implants were measured in each laparotomy to determine any change in size. Leukocyte populations were analyzed by flow cytometry and immunofluorescence microscopy. Cytometric results were similar in blood and peritoneal lavage. CD25+ and natural killer (NK) cell levels in peripheral blood were lower in rats with endometriosis treated with IL-2, whereas NK cells increased in lavage compared to placebo group. The percentage of macrophages and dendritic cells in blood were higher in all rats treated with IL-2, as well as peritoneal dendritic cells. Implant size of these rats decreased significantly, showing a greater number of activated lymphocytes, macrophages, NK and dendritic cells inside them. In conclusion, recombinant IL-2 induced recruitment of activated leukocytes into endometriotic-like foci, and this was related to a reduction of the implant size, suggesting potential effectiveness of IL-2 as an immunomodulatory agent in this pathology.

Evidence for incorporation of free-floating mesothelial cells as a mechanism of serosal healing

Regeneration of the mesothelium is unlike that of other epithelial-like surfaces, as healing does not occur solely by centripetal migration of cells from the wound edge. The mechanism of repair of mesothelium is controversial,but it is widely accepted, without compelling evidence, that pluripotent cells beneath the mesothelium migrate to the surface and differentiate into mesothelial cells. In this study we examined an alternative hypothesis, using in vivo cell-tracking studies, that repair involves implantation,proliferation and incorporation of free-floating mesothelial cells into the regenerating mesothelium. Cultured mesothelial cells, fibroblasts and peritoneal lavage cells were DiI- or PKH26-PCL-labelled and injected into rats immediately following mesothelial injury. Implantation of labelled cells was assessed on mesothelial imprints using confocal microscopy, and cell proliferation was determined by proliferating cell nuclear antigen immunolabelling. Incorporation of labelled cells, assessed by the formation of apical junctional complexes, was shown by confocal imaging of zonula occludens-1 protein. Labelled cultured mesothelial and peritoneal lavage cells, but not cultured fibroblasts, implanted onto the wound surface 3, 5 and 8 days after injury. These cells proliferated and incorporated into the regenerated mesothelium, as demonstrated by nuclear proliferating cell nuclear antigen staining and membrane-localised zonula occludens-1 expression,respectively. Furthermore, immunolocalisation of the mesothelial cell marker HBME-1 demonstrated that the incorporated, labelled lavage-derived cells were mesothelial cells and not macrophages as it had previously been suggested. This study has clearly shown that serosal healing involves implantation,proliferation and incorporation of free-floating mesothelial cells into the regenerating mesothelium.

Stimulation of mesothelial cell proliferation by exudate macrophages enhances serosal wound healing in a murine model

Examination of thermally induced serosal lesions in mice displayed collections of inflammatory cells, predominantly macrophages, on and surrounding the wound within 48 hours of injury. Furthermore, by 2 days a large number of uninjured mesothelial cells adjacent to the wound were synthesizing DNA. From these findings, it was hypothesized that macrophages play a major role in serosal repair by stimulating mesothelial cell proliferation. Again, using a murine model of mesothelial regeneration, depletion of circulating monocytes significantly delayed serosal healing whereas addition of peritoneal exudate cells to the wound site 36 hours before injury increased the healing rate. In vivo assessment of mesothelial cell proliferation using tritiated thymidine incorporation and autoradiography demonstrated that peritoneal exudate cells stimulated mesothelial cell proliferation (12.44 +/- 1.63% labeling index, compared with controls in which medium only was used 4.48 +/- 0.71%). The mesothelial proliferation was predominantly because of macrophage-secreted products with molecular weights of 36 to 53 kd or 67 to 100 kd. These data support the hypothesis that macrophages play an important role in serosal healing by stimulating mesothelial cell proliferation.

Prevention of experimental postoperative peritoneal adhesions by N,O-carboxymethyl chitosan

BACKGROUND

Postsurgical adhesion formation can result in significant morbidity and, to a lesser extent, death. The purpose of this experiment was to assess the ability of N,O-carboxymethyl chitosan (NOCC) to prevent postsurgical adhesion formation in vivo.

METHODS

Randomized groups of Sprague-Dawley rats were studied under two abdominal surgery models, the uterine horn model and the small bowel laceration model, for the ability of NOCC to reduce the incidence and severity of adhesion formation. Adhesions in animals were assessed after death by a blinded observer 10 to 14 days after surgical manipulation.

RESULTS

NOCC consistently reduced the size, strength, and number of adhesions in both rat models. NOCC was also found to be more effective than hyaluronic acid at inhibiting adhesion formation.

CONCLUSIONS

NOCC is a more effective antiadhesion agent than is the more expensive hyaluronic acid. Although the exact mechanism of NOCC's antiadhesion activity is as yet unclear, the novel chemical is of particular interest for clinical use.

Prevention of postoperative adhesions by an antibody to vascular permeability factor/vascular endothelial growth factor in a murine model

OBJECTIVE

Our purpose was to test the ability of an antiserum to vascular permeability factor/vascular endothelial growth factor to inhibit postoperative adhesion formation in a murine model.

STUDY DESIGN

After a standardized peritoneal injury, 28 Balb/c mice were randomized and treated intraperitoneally with either vascular permeability factor antiserum (n = 14) or preimmune serum (n = 14) at the time of abdominal closure. Mice were killed on postoperative day 14, and the development of intraabdominal adhesions was determined. Adhesion scoring was based on an overall assessment of the extent, location, and type of adhesions present. Statistical analyses were performed with the Mann-Whitney and Fisher's exact tests.

RESULTS

The mice treated with the vascular permeability factor antiserum had significantly lower adhesion scores than did the control group (mean +/- SD 1.5 +/- 0.9, median 1.0, vs control 2.5 +/- 0.7, median 3.0). When the groups were analyzed for the presence of grade 2 or 3 adhesions, the group treated with vascular permeability factor antiserum had a significantly lower incidence of advanced adhesions (38%, vs control 92%).

CONCLUSION

This study demonstrates that the intraperitoneal administration of a neutralizing antiserum to vascular permeability factor/vascular endothelial growth factor limits postoperative adhesion formation. These observations, to the best of our knowledge, are the first to suggest a role for vascular permeability factor in the pathogenesis of adhesion formation.

Contemporary adhesion prevention

OBJECTIVE

To (1) review the events leading to peritoneal adhesion formation; (2) review traditional adhesion prevention adjuvants; (3) overview studies for adhesion prevention barriers including a perspective for their use; and (4) look toward the future of adhesion prevention.

RESULTS

A great deal of effort has been dedicated to reduce adhesion formation because of the morbidity associated with adhesions and the associated economic burden, which considering only hospital costs and surgeons' fees, was $1,180 million in the United States. To understand the role of adhesion barriers in gynecological surgery, an appreciation of the cellular cascade and temporal nature of peritoneal repair is necessary. Evidence indicates that areas denuded of peritoneum will heal satisfactorily and that suturing of the peritoneum may increase adhesion formation. Physical barriers, including both mechanical and viscous solutions, are widely used to prevent adhesion formation by limiting tissue apposition during the critical stages of mesothelial repair. Clinical studies do not support the use of intraperitoneal, dextran for adhesion prevention. Theoretical considerations of peritoneal fluid dynamics indicate that crystalloid instillates should not prevent adhesion formation because of their short intraperitoneal residence. This prediction is consistent with clinical observation. The availability of Interceed (Johnson and Johnson Medical, Inc., Arlington, TX) and Gore-Tex Surgical Membrane (W.L. Gore, Flagstaff, Arizona) barriers provides substantial progress in postsurgical adhesion prevention.

CONCLUSIONS

Although many investigators are incorporating adhesion prevention barriers into their routine clinical situations, physician acceptance is constrained by technical difficulties.