A role for the fibrinolytic system in postsurgical adhesion formation

Impact of Standard Versus Low Pneumoperitoneum Pressure on Peritoneal Environment in Laparoscopic Cholecystectomy. Randomized Clinical Trial

BACKGROUND

High CO 2 pneumoperitoneum pressure during laparoscopy adversely affects the peritoneal environment. This study hypothesized that low pneumoperitoneum pressure may be linked to less peritoneal damage and possibly to better clinical outcomes.

MATERIALS AND METHODS

One hundred patients undergoing scheduled laparoscopic cholecystectomy were randomized 1:1 to low or to standard pneumoperitoneum pressure. Peritoneal biopsies were performed at baseline time and 1 hour after peritoneum insufflation in all patients. The primary outcome was peritoneal remodeling biomarkers and apoptotic index. Secondary outcomes included biomarker differences at the studied times and some clinical variables such as length of hospital stay, and quality and safety issues related to the procedure.

RESULTS

Peritoneal IL6 after 1 hour of surgery was significantly higher in the standard than in the low-pressure group (4.26±1.34 vs. 3.24±1.21; P =0.001). On the contrary, levels of connective tissue growth factor and plasminogen activator inhibitor-I were higher in the low-pressure group (0.89±0.61 vs. 0.61±0.84; P =0.025, and 0.74±0.89 vs. 0.24±1.15; P =0.028, respectively). Regarding apoptotic index, similar levels were found in both groups and were 44.0±10.9 and 42.5±17.8 in low and standard pressure groups, respectively. None of the secondary outcomes showed differences between the 2 groups.

CONCLUSIONS

Peritoneal inflammation after laparoscopic cholecystectomy is higher when surgery is performed under standard pressure. Adhesion formation seems to be less in this group. The majority of patients undergoing surgery under low pressure were operated under optimal workspace conditions, regardless of the surgeon's expertise.

Prevention strategies of postoperative adhesion in soft tissues by applying biomaterials: Based on the mechanisms of occurrence and development of adhesions

Postoperative adhesion (POA) widely occurs in soft tissues and usually leads to chronic pain, dysfunction of adjacent organs and some acute complications, seriously reducing patients' quality of life and even being life-threatening. Except for adhesiolysis, there are few effective methods to release existing adhesion. However, it requires a second operation and inpatient care and usually triggers recurrent adhesion in a great incidence. Hence, preventing POA formation has been regarded as the most effective clinical strategy. Biomaterials have attracted great attention in preventing POA because they can act as both barriers and drug carriers. Nevertheless, even though much reported research has been demonstrated their efficacy on POA inhibition to a certain extent, thoroughly preventing POA formation is still challenging. Meanwhile, most biomaterials for POA prevention were designed based on limited experiences, not a solid theoretical basis, showing blindness. Hence, we aimed to provide guidance for designing anti-adhesion materials applied in different soft tissues based on the mechanisms of POA occurrence and development. We first classified the postoperative adhesions into four categories according to the different components of diverse adhesion tissues, and named them as "membranous adhesion", "vascular adhesion", "adhesive adhesion" and "scarred adhesion", respectively. Then, the process of the occurrence and development of POA were analyzed, and the main influencing factors in different stages were clarified. Further, we proposed seven strategies for POA prevention by using biomaterials according to these influencing factors. Meanwhile, the relevant practices were summarized according to the corresponding strategies and the future perspectives were analyzed.

An in vitro model that mimics the foreign body response in the peritoneum: Study of the bioadhesive properties of HA-based materials

A cascade of reactions known as the foreign body response (FBR) follows the implantation of biomaterials leading to the formation of a fibrotic capsule around the implant and subsequent health complications. The severity of the FBR is driven mostly by the physicochemical characteristics of implanted material, the method and place of implantation, and the degree of immune system activation. Here we present an in vitro model for assessing new materials with respect to their potential to induce a FBR in the peritoneum. The model is based on evaluating protein sorption and cell adhesion on the implanted material. We tested our model on the free-standing films prepared from hyaluronan derivatives with different hydrophobicity, swelling ratio, and rate of solubilization. The proteomic analysis of films incubated in the mouse peritoneum showed that the presence of fibrinogen was driving the cell adhesion. Neither the film surface hydrophobicity/hydrophilicity nor the quantity of adsorbed proteins were decisive for the induction of the long-term cell adhesion leading to the FBR, while the dissolution rate of the material proved to be a crucial factor. Our model thus helps determine the probability of a FBR to materials implanted in the peritoneum while limiting the need for in vivo animal testing.

Peritoneal Adhesions and their Prevention - Current Trends

The development of adhesions after gynecologic surgery is a severe problem with ramifications that go beyond the medical complications patients suffer (which most often include pain, obstruction and infertility), since they also impose a huge financial burden on the health care system and increase the workload of surgeons and all personnel involved in surgical follow-up care. Surgical techniques to avoid adhesion formation have not proven to be sufficient and pharmaceutical approaches for their prevention are even less effective, which means that the use of adhesion prevention devices is essential for achieving decent prophylaxis. This review explores the wide range of adhesion prevention products currently available on the market. Particular emphasis is put on prospective randomized controlled clinical trials that include second-look interventions, as these offer the most solid evidence of efficacy. We focused on adhesion scores, which are the most common way to quantify adhesion formation. This enables a direct comparison of the efficacies of different devices. While the greatest amount of data are available for oxidized regenerated cellulose, the outcomes with this adhesion barrier are mediocre and several studies have shown little efficacy. The best results have been achieved using adhesion barriers based on either modified starch, i.e., 4DryField® PH (PlantTec Medical GmbH, Lüneburg, Germany), or expanded polytetrafluoroethylene, i.e., GoreTex (W.L. Gore & Associates, Inc., Medical Products Division, Flagstaff, AZ), albeit the latter, as a non-resorbable barrier, has a huge disadvantage of having to be surgically removed again. Therefore, 4DryField® PH currently appears to be a promising approach and further studies are recommended.

Cell barrier function of resident peritoneal macrophages in post-operative adhesions

Post-operative adhesions are a leading cause of abdominal surgery-associated morbidity. Exposed fibrin clots on the damaged peritoneum, in which the mesothelial barrier is disrupted, readily adhere to surrounding tissues, resulting in adhesion formation. Here we show that resident F4/80^HighCD206⁻ peritoneal macrophages promptly accumulate on the lesion and form a ‘macrophage barrier’ to shield fibrin clots in place of the lost mesothelium in mice. Depletion of this macrophage subset or blockage of CD11b impairs the macrophage barrier and exacerbates adhesions. The macrophage barrier is usually insufficient to fully preclude the adhesion formation; however, it could be augmented by IL-4-based treatment or adoptive transfer of this macrophage subset, resulting in robust prevention of adhesions. By contrast, monocyte-derived recruited peritoneal macrophages are not involved in the macrophage barrier. These results highlight a previously unidentified cell barrier function of a specific macrophage subset, also proposing an innovative approach to prevent post-operative adhesions.

Peritoneal adhesions are a major cause of complications after abdominal surgery. Here the authors use a post-operative abdominal adhesion model in mice to show that resident F4/80^HighCD206⁻ macrophages form a protective barrier that can be enhanced by IL-4 administration or adoptive transfer of these cells.

Cellular Components Contributing to Fibrosis in Endometriosis: A Literature Review

Endometriosis-related fibrosis represents a complex phenomenon with underlying mechanisms yet to be clarified. Fibrosis is consistently present in all disease forms and contributes to classic endometriosis-related symptoms of pain and infertility. The purpose of this literature review was to examine the role of various cellular populations and biologic mechanisms and signaling pathways in inducing fibrogenesis of endometriotic lesions. A search was performed through PubMed and MEDLINE for animal and human studies published in English in the last 23 years that examined fibrosis in superficial, ovarian, and deep infiltrating endometriosis. The main cell types found to be involved in the development of fibrosis were platelets, macrophages, ectopic endometrial cells, and sensory nerve fibers. Interactions among each of the cell types contribute to the production of fibrosis through the production of soluble factors, mostly transforming growth factor-β but also other cytokines and neuropeptides. Cell types known to be critical to the pathophysiology of endometriosis also contribute to fibrogenesis, thus supporting the theory that fibrosis is an inherent part of endometriosis.

Novel oral transforming growth factor-β signaling inhibitor potently inhibits postsurgical adhesion band formation

Here, we have investigated the therapeutic potency of EW-7197, a transforming growth factor-β type I receptor kinase inhibitor, against postsurgical adhesion band formation. Our results showed that this pharmacological inhibitor prevented the frequency and the stability of adhesion bands in mice model. We have also shown that downregulation of proinflammatory cytokines, reduce submucosal edema, attenuation of proinflammatory cell infiltration, inhibition of oxidative stress, decrease in excessive collagen deposition, and suppression of profibrotic genes at the site of surgery are some of the mechanisms by which EW-7197 elicits its protective responses against adhesion band formation. These results clearly suggest that EW-7197 has novel therapeutic properties against postsurgical adhesion band formation with clinically translational potential of inhibiting key pathological responses of inflammation and fibrosis in postsurgery patients.

Chronic Niche Inflammation in Endometriosis-Associated Infertility: Current Understanding and Future Therapeutic Strategies

Endometriosis is an estrogen-dependent inflammatory disease that affects up to 10% of women of reproductive age and accounts for up to 50% of female infertility cases. It has been highly associated with poorer outcomes of assisted reproductive technology (ART), including decreased oocyte retrieval, lower implantation, and pregnancy rates. A better understanding of the pathogenesis of endometriosis-associated infertility is crucial for improving infertility treatment outcomes. Current theories regarding how endometriosis reduces fertility include anatomical distortion, ovulatory dysfunction, and niche inflammation-associated peritoneal or implantation defects. This review will survey the latest evidence on the role of inflammatory niche in the peritoneal cavity, ovaries, and uterus of endometriosis patients. Nonhormone treatment strategies that target these inflammation processes are also included. Furthermore, mesenchymal stem cell-based therapies are highlighted for potential endometriosis treatment because of their immunomodulatory effects and tropism toward inflamed lesion foci. Potential applications of stem cell therapy in treatment of endometriosis-associated infertility in particular for safety and efficacy are discussed.

AK03, a new recombinant fibrinogenase prevents abdominal adhesions in a rat model without systemic side effects

BACKGROUND

Abdominal adhesions are one of the most common complications after abdominal surgery, and fibrin is suspected to be a crucial component. The aim of the current study was an in vivo evaluation of a new recombinant fibrinogenase (AK03) in two animal models.

METHODS

Sixty-four rats were randomly divided into four groups (sodium chloride [NaCl], icodextrin, AK03 low dose, and AK03 high dose) and evaluated at two time endpoints. Adhesion model comprised both a visceral defect (terminal ileum) and parietal defect. Test (AK03) and control substances (NaCl and icodextrin) were administered intraperitoneally after setting the intraabdominal defects. A second dose was administered 24 h after surgery. Plasma fibrinogen values were taken at baseline and after 7 and 21 d, respectively. Rats were sacrificed after 7 or 21 d for macroscopic (Diamond score) and immunohistochemical investigations.

RESULTS

After 7 and 21 d, the Diamond score of postsurgical adhesions were significantly lower in both AK03-treated groups compared with NaCl control group (P = 0.02). There were no unspecific systemic side effects in both treatment groups and no decrease in plasma fibrinogen concentration. In none of the four groups was there any evidence for impaired wound repair. Microscopically in the area of the parietal defect, we saw less cluster of differentiation 3⁺ T-lymphocytes and cluster of differentiation 68⁺ macrophages in both groups receiving AK03 compared with the NaCl and icodextrin control groups.

CONCLUSIONS

The results of this study indicate that the new recombinant fibrinogenase AK03 effectively prevents peritoneal adhesions without causing side effects, notably systemic fibrinogen depletion, bleeding, or impaired wound repair. Due to these results, future clinical studies may be promising.

Peripheral serotonin regulates postoperative intra-abdominal adhesion formation in mice

The aim of the present study is to investigate the role and potential mechanisms of peripheral serotonin in postoperative intra-abdominal adhesion formation in mice. The caecum-rubbing operations were conducted for intra-abdominal adhesion formation modelling in wild-type and Tph1−/− mice. The deficiency of serotonin significantly decreased the adhesion scores, weight loss, and adhesion thickness as well as levels of collagen fibres and hydroxyproline in the adhesive tissues. The Tph1−/− mice exhibited a milder inflammatory response and oxidative stress in the adhesive tissues than did the wild-type mice. Moreover, the deficiency of serotonin reduced the levels of PAI-1 and fibrinogen, and raised the t-PA and t-PA/PAI levels in the peritoneal fluids. Moreover, the expressions of CD34, VEGF, TGF-β and 5-HT_2B receptor in the adhesive tissues were significantly decreased in the Tph1−/− group mice. Furthermore, the Tph1−/− +5-HTP group showed more severe adhesions than did the Tph1−/− group mice, and the p-chlorophenylalanine (PCPA) could markedly alleviated the adhesion formation in the WT mice. In conclusion, the present study showed that peripheral serotonin regulated postoperative intra-abdominal adhesion formation by facilitating inflammation, oxidative stress, disorder of the fibrinolytic system, angiopoiesis and TGF-β1 expression via the 5-HT_2B receptor in the adhesive tissues.

Expression of CD68 positive macrophages in the use of different barrier materials to prevent peritoneal adhesions-an animal study

In preventing postoperative adhesion formation the optimal barrier material has still not been found. It is therefore imperative to assess the biocompatibility of potential barrier devices. Macrophages play a decisive role in the regulation of wound healing, tissue regeneration and foreign body reaction. Since the number of CD68-positive macrophages represents an important parameter within biomaterial testing, in the present study it was analysed whether a correlation exists between the total number of CD68-positive macrophages and the extent of fibrosis or inflammation in peritoneal adhesion prevention using biomaterials. After standardized peritoneal wounding, Wistar rats were treated with five adhesion barriers or remained untreated as a control. After 14 days, animals were sacrificed and the treated areas were evaluated histomorphologically and immunohistologically. A heterogeneous pattern of macrophage count in relation to fibrosis or inflammation was found. While some groups described a moderate macrophage infiltration without fibrosis, others showed similar numbers of macrophages, but accompanied by moderate fibrosis. Moreover, a minimal number of macrophages was associated with minimal fibrosis. Mild inflammation was seen both with minimal and moderate macrophage infiltration. Altogether, no correlation could be established between the tissue response and the count of CD68-positive macrophages. With a view to macrophage heterogeneity further studies are required to determine the different macrophage subpopulations and clarify the role of these in the tissue responses to barrier materials.

Combined intraoperative administration of a histone deacetylase inhibitor and a neurokinin-1 receptor antagonist synergistically reduces intra-abdominal adhesion formation in a rat model

BACKGROUND

Intra-abdominal adhesions are the most frequent postoperative complication after abdominopelvic surgery. Our laboratory has previously shown that an intraoperative peritoneal lavage containing either the histone deacetylase inhibitor valproic acid (VPA) or a neurokinin-1 receptor antagonist (NK-1RA) reduced adhesions by approximately 50% in a rat model. The objective of this study was to determine whether the combination of these 2 drugs was more effective in reducing adhesions than either alone.

METHODS

Rats underwent laparotomy with creation of peritoneal ischemic buttons to induce adhesions. A single dose of VPA (25 mg/kg), NK-1RA (50 mg/kg), a combination of both, or 0.9% saline was lavaged intraperitoneally just before wound closure. On postoperative day 7, adhesions were quantified. To investigate early mechanisms of adhesiogenesis, adhesions were created as described and adhesive button tissue was harvested at 30 minutes and 3 hours postoperatively and fibrinogen and vascular endothelial growth factor (VEGF) protein levels, both indices of peritoneal extravasations, were determined by Western blot analysis. Peritoneal fluid was collected in similar experiments at 30 minutes, and 3 and 6 hours to measure fibrinolytic activity, an index of the ability of the peritoneum to degrade fibrinous adhesions.

RESULTS

The coadministration of VPA plus NK-1RA reduces adhesions by 72.6% relative to saline (P < .001); this reduction was greater than either compound alone (P < .001). Peritoneal fibrinolytic activity was significantly increased at 3 and 6 hours postoperatively in animals administered the combination therapy versus saline (P = .01). VPA plus NK-1RA significantly decreased fibrinogen and VEGF protein levels at 3 and 6 hours compared with saline controls.

CONCLUSION

These results suggest that a combined pharmacologic approach targeting multiple adhesiogenic pathways provides optimal adhesion prevention.

Response to pathological processes in the peritoneal cavity--sepsis, tumours, adhesions, and ascites

The peritoneum is one of the commonest sites for pathological processes in pediatric surgery. Its response to pathological processes is characterized by an inflammatory reaction with specific pathways depending on the type of injury or peritoneal process involved. This review discusses the current understanding of peritoneal inflammation, adhesion formation, intra-abdominal sepsis, peritoneal metastasis, and ascites and briefly reviews new therapeutic strategies to treat or prevent these pathological entities. Recent studies have improved the understanding of peritoneal responses, resulting in possible new targets for prevention and therapy.

The neurokinin 1 receptor regulates peritoneal fibrinolytic activity and postoperative adhesion formation

BACKGROUND

Intra-abdominal adhesions are a common source of postoperative morbidity. Previous studies in our laboratory have shown that a neurokinin 1 receptor antagonist (NK-1RA) reduces abdominal adhesion formation and increases peritoneal fibrinolytic activity. However, the cellular pathway by which the antagonist exerts its effects is unclear, as cultured peritoneal mesothelial cells exposed to the NK-1RA show increases in fibrinolytic activity despite having very low expression of neurokinin 1 receptor (NK-1R) messenger RNA and protein. Our aim was to determine whether the NK-1R plays an essential role in the adhesion-reducing effects of the NK-1RA, or if the NK-1RA is acting independently of the receptor.

METHODS

Homozygous NK-1R knockout mice and age matched wild-type mice underwent laparotomy with cecal cautery to induce adhesions. At the time of surgery, mice received a single intraperitoneal dose of either NK-1RA (25 mg/kg) or saline alone. Adhesion severity at the site of cecal cautery was assessed on postoperative day 7. In a separate experiment, peritoneal fluid was collected from wild type and NK-1R knockout mice 24 h after laparotomy with cecal cautery and administration of either NK-1RA or saline. Tissue plasminogen activator levels, representative of total fibrinolytic activity, were then measured in peritoneal fluid.

RESULTS

In wild-type mice, NK-1RA administration significantly decreased adhesion formation compared with saline controls. Among the NK-1R knockout mice, there was no significant reduction in adhesion formation by the NK-1RA. Fibrinolytic activity increased 244% in wild-type mice administered NK-1RA compared with saline controls; however, the NK-1RA did not raise fibrinolytic activity above saline controls in NK-1R knockout mice.

CONCLUSIONS

These data indicate that the NK-1R mediates the adhesion-reducing effects of the NK-1RA, in part, by the upregulation of peritoneal fibrinolysis, and suggest that the NK-1R is a promising therapeutic target for adhesion prevention.

Practical implications of postoperative adhesions for preoperative consent and operative technique

Adhesions complicate most intra-peritoneal operations. Once adhesions have formed, patients are at life-long risk for complications that include small bowel obstruction, increased risks during subsequent operations and female infertility. This has two implications for the daily work of surgeons. On the one hand, surgeons need to include the risks from adhesions during pre-operative consent. On the other hand, surgeons need to use operative techniques that minimize adhesions. Therefore this review focuses on the practical implications of adhesions for preoperative consent and operative technique.

Current strategies and future perspectives for intraperitoneal adhesion prevention

INTRODUCTION

The formation of peritoneal adhesions still is a relevant clinical problem after abdominal surgery. Until today, the most important clinical strategies for adhesion prevention are accurate surgical technique and the physical separation of traumatized serosal areas. Despite a variety of barriers which are available in clinical use, the optimal material has not yet been found.

DISCUSSION

Mesothelial cells play a crucial physiological role in friction less gliding of the serosa and the maintenance of anantiadhesive surface. The formation of postoperative adhesions results from a cascade of events and is regulated by various cellular and humoral factors. Therefore, optimization or functionalization of barrier materials by developments interacting with this cascade on a structural or pharmacological level could give an innovative input for future strategies in peritoneal adhesion prevention. For this purpose, the proper understanding of the formal pathogenesis of adhesion formation is essential. Based on the physiology of the serosa and the pathophysiology of adhesion formation, the available barriers in current clinical practice as well as new innovations are discussed in the present review.

Pathogenesis of endometriosis: the role of genetics, inflammation and oxidative stress

INTRODUCTION

Endometriosis is defined as the presence of endometrial tissue outside the uterine cavity.

MATERIALS AND METHODS

The etiology of this multifactorial disease is still unresolved and an increasing number of studies suggest that genetic, hormonal, environmental, immunological and oxidative factors may all play an important role in the pathogenesis of this disorder.

CONCLUSIONS

In this literature review, inflammatory activity, oxidative stress as well as genetic abnormalities and mutations have been studied in an effort to identify factors predisposing to endometriosis.

Peritoneal cytokines and adhesion formation in endometriosis: an inverse association with vascular endothelial growth factor concentration

OBJECTIVE

To evaluate inflammatory/angiogenic cytokines-interleukin-1β (IL-1β), IL-6, IL-8, IL-12, interferon-γ (IFN-γ), tumor necrosis factor (TNF), and vascular endothelial growth factor A (VEGF-A)-in the peritoneal fluid of patients with endometriosis in relation to the occurrence and severity of pelvic adhesions and in control women without pelvic pathology.

DESIGN

Case-control study.

SETTING

University research institution and hospital.

PATIENT(S)

Sixty-five women with laparoscopically and histopathologically confirmed endometriosis, including 40 women with pelvic adhesions, and 37 control women without pelvic pathology.

INTERVENTION(S)

Peritoneal fluid aspirated during routine diagnostic laparoscopic examination.

MAIN OUTCOME MEASURE(S)

Cytokines evaluated in the peritoneal fluid via specific enzyme-linked immunosorbent assays.

RESULT(S)

Endometriosis and the revised American Fertility Society score of this disease were associated with statistically significantly increased levels of peritoneal IL-6 and IL-8 whereas the incidence and score of endometriosis-related pelvic adhesions were negatively associated with increased levels of VEGF-A. Notably, the concentration of VEGF-A predicted adhesion development and severity after adjustment for endometriosis severity. The adhesion score also correlated with increased levels of IL-6; however, after adjustment for endometriosis severity, the effect of this cytokine was no longer statistically significant.

CONCLUSION(S)

Increased levels of VEGF-A may be associated with a decreased rate of pelvic adhesion formation in the course of endometriosis.

Severe inflammatory reaction induced by peritoneal trauma is the key driving mechanism of postoperative adhesion formation

BACKGROUND

Many factors have been put forward as a driving mechanism of surgery-triggered adhesion formation (AF). In this study, we underline the key role of specific surgical trauma related with open surgery (OS) and laparoscopic (LS) conditions in postoperative AF and we aimed to study peritoneal tissue inflammatory reaction (TIR), remodelling specific complications of open surgery (OS) versus LS and subsequently evaluating AF induced by these conditions.

METHODS

A prospective randomized study was done in 80 anaesthetised female Wistar rats divided equally into 2 groups. Specific traumatic OS conditions were induced by midline incision line (MIL) extension and tissue drying and specific LS conditions were remodelled by intraperitoneal CO2 insufflation at the 10 cm of water. TIR was evaluated at the 24th, 72nd, 120th and 168th hour by scoring scale. Statistical analysis was performed by the non-parametric t test and two-way ANOVA using Bonferroni post-tests.

RESULTS

More pronounced residual TIR was registered after OS than after LS. There were no significant TIR interactions though highly significant differences were observed between the OS and LS groups (p < 0.0001) with regard to surgical and time factors. The TIR change differences between the OS and LS groups were pronounced with postoperative time p < 0.05 at the 24th and 72nd; p < 0.01--120th and p < 0.001--168th hrs. Adhesion free wounds were observed in 20.0 and 31.0% of cases after creation of OS and LS conditions respectively; with no significant differences between these values (p > 0.05). However larger adhesion size (41.67 ± 33.63) was observed after OS in comparison with LS (20.31 ± 16.38). The upper-lower 95% confidential limits ranged from 60.29 to 23.04 and from 29.04 to 11.59 respectively after OS and LS groups with significant differences (p = 0.03). Analogous changes were observed in adhesion severity values. Subsequently, severe TIR parameters were followed by larger sizes of severe postoperative adhesions in the OS group than those observed in the LS group.

CONCLUSIONS

MIL extension and tissue drying seem to be the key factors in the pathogenesis of adhesion formation, triggering severe inflammatory reactions of the peritoneal tissue surrounding the MIL resulting in local and systemic consequences. CO2 insufflation however, led to moderate inflammation and less adhesion formation.

Pathogenesis of postoperative adhesion formation

Background

Current views on the pathogenesis of adhesion formation are based on the ‘classical concept of adhesion formation’, namely that a reduction in peritoneal fibrinolytic activity following peritoneal trauma is of key importance in adhesion development.

Methods

A non-systematic literature search (1960–2010) was performed in PubMed to identify all original articles on the pathogenesis of adhesion formation. Information was sought on the role of the fibrinolytic, coagulatory and inflammatory systems in the disease process.

Results

One unifying concept emerged when assessing 50 years of studies in animals and humans on the pathogenesis of adhesion formation. Peritoneal damage inflicted by surgical trauma or other insults evokes an inflammatory response, thereby promoting procoagulatory and antifibrinolytic reactions, and a subsequent significant increase in fibrin formation. Importantly, peritoneal inflammatory status seems a crucial factor in determining the duration and extent of the imbalance between fibrin formation and fibrin dissolution, and therefore in the persistence of fibrin deposits, determining whether or not adhesions develop.

Conclusion

Suppression of inflammation, manipulation of coagulation as well as direct augmentation of fibrinolytic activity may be promising antiadhesion treatment strategies.

Intraperitoneal adhesions--an ongoing challenge between biomedical engineering and the life sciences

Peritoneal adhesions remain a relevant clinical problem despite the currently available prophylactic barrier materials. So far, the physical separation of traumatized serosa areas using barriers represents the most important clinical strategy for adhesion prevention. However, the optimal material has not yet been found. Further optimization or pharmacological functionalization of these barriers could give an innovative input for peritoneal adhesion prevention. Therefore, a more complete understanding of pathogenesis is required. On the basis of the pathophysiology of adhesion formation the main barriers currently in clinical practice as well as new innovations are discussed in the present review. Physiologically, mesothelial cells play a decisive role in providing a frictionless gliding surface on the serosa. Adhesion formation results from a cascade of events and is regulated by a variety of cellular and humoral factors. The main clinically applied strategy for adhesion prevention is based on the use of liquid or solid adhesion barriers to separate physically any denuded tissue. Both animal and human trials have not yet been able to identify the optimal barrier to prevent adhesion formation in a sustainable way. Therefore, further developments are required for effective prevention of postoperative adhesion formation. To reach this goal the combination of structural modification and pharmacological functionalization of barrier materials should be addressed. Achieving this aim requires the interaction between basic research, materials science and clinical expertise.

Impact of intraperitoneal pressure and duration of surgery on levels of tissue plasminogen activator and plasminogen activator inhibitor-1 mRNA in peritoneal tissues during laparoscopic surgery

BACKGROUND

Our objective was to evaluate the impact of intraperitoneal pressure (IPP) and duration of a CO(2) pneumoperitoneum on the peritoneal fibrinolytic system during laparoscopic surgery.

METHODS

Human study: Patients undergoing laparoscopic surgery were divided into two groups: low (8 mmHg, n= 32) or standard (12 mmHg, n= 36) IPP. Normal peritoneum was collected from the parietal wall at the beginning of surgery and every 60 min thereafter. Mouse study: Mice were divided into three groups: low (2 mmHg) or high (8 mmHg) IPP or laparotomy. Peritoneal tissue was collected at 0, 4, 8, 24, 48 and 72 h, and 5 and 7 days after surgery. Real-time RT-PCR was performed in humans and mice to measure the levels of tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) mRNA in peritoneal tissues.

RESULTS

Human study: The tPA/PAI-1 mRNA ratio was significantly decreased in the 12 mmHg group at 1 h [P < 0.0001 versus matched initial peritoneal biopsies (MI)]. The tPA/PAI-1 mRNA ratio decreased in both groups at 2 h (P < .0.01 versus MI). Mouse study: The tPA/PAI-1 ratio was decreased at 0 h, and the difference was significant at 4 h in both the laparotomy (P < 0.001 versus controls, 0 h, 5 and 7 days) and high-IPP (P < 0.0001 versus 0, 48 and 72 h, 5 and 7 days) groups. No changes in tPA/PAI-1 ratio were observed in the low-IPP group.

CONCLUSIONS

A low IPP and shorter duration of surgery appear to minimally impact the fibrinolytic system during a CO₂ pneumoperitoneum.

Adhesion formation after intracapsular myomectomy with or without adhesion barrier

OBJECTIVE

To show the prevention of adhesion formation by placing an absorbable adhesion barrier after intracapsular myomectomy.

DESIGN

Prospective blinded observational study.

SETTING

University-affiliated Hospitals.

PATIENT(S)

Patients ≥ 18 years old with single or multiple uterine fibroids removed by laparoscopic or abdominal intracapsular myomectomy.

INTERVENTION(S)

A total of 694 women undergoing laparoscopic or abdominal myomectomy were randomized for placement of oxidized regenerated cellulose absorbable adhesion barrier to the uterine incision or for control subjects without barriers. The presence of adhesions was assessed in 546 patients who underwent subsequent surgery.

MAIN OUTCOME MEASURE(S)

The primary and secondary outcomes of the analysis were the presence and severity of adhesions for four groups: laparotomy with barrier, laparotomy without barrier, laparoscopy with barrier, and laparoscopy without barrier.

RESULT(S)

There was a higher rate of adhesions in laparotomy without barrier (28.1%) compared with laparoscopy with no barrier (22.6%), followed by laparotomy with barrier (22%) and laparoscopy with barrier (15.9%). Additionally, the type of adhesions were different, filmy and organized were predominant with an adhesion barrier, and cohesive adhesions were more common without an adhesion barrier.

CONCLUSION(S)

Oxidized regenerated cellulose reduces postsurgical adhesions. Cohesive adhesions reduction was noted in laparoscopy.

Addition of nimesulide to small intestinal submucosa biomaterial inhibits postsurgical adhesiogenesis in rats

Adhesion formation is a common complication in abdominal surgery with incidence as high as 93% and small bowel obstruction a common complication. Because the extracellular matrix material, small intestinal submucosa (SIS), is commonly used in various surgical procedures, methods to inhibit adhesiogenesis are of great interest. This study was undertaken to determine if incorporation of nimesulide (NM), a selective cyclooxygenase (COX)-2 inhibitor, could reduce the extent and tenacity of intraabdominal adhesion formation associated with SIS implantation. Female Sprague-Dawley rats underwent a cecal abrasion surgical procedure to induce adhesiogenesis. Rats were either left untreated or treated by direct application over the injured cecum with polypropylene mesh (PPM); SIS; SIS containing a low dose of NM; or SIS containing a high dose of NM. Rats were euthanized 21 days later, and adhesion extent and tenacity were evaluated using standard scales (0 = minimal adhesiogenesis; 4 = severe adhesiogenesis). Addition of NM to SIS resulted in a significant (p < 0.05) reduction in adhesion extent and in a similar reduction in adhesion tenacity for SIS containing a low dose of NM. Adhesions typically extended from the abraded cecal surface to the body wall and were characterized histologically by fibrous tissue adherent to the cecal wall. In conclusion, addition of the nonsteroidal anti-inflammatory, COX-2 selective drug, NM, to SIS attenuates adhesion extent and tenacity when compared with surgical placement of SIS or PPM alone.

The peritoneal fibrinolytic response to conventional and laparoscopic colonic surgery

BACKGROUND

Laparoscopic surgery is considered to induce less peritoneal trauma than conventional surgery. The peritoneal plasmin system is important in the processes of peritoneal healing and adhesion formation. The present study assessed the peritoneal fibrinolytic response to laparoscopic and conventional colonic surgery.

METHODS

Twenty-four patients scheduled for a right colonic resection were enrolled in the trial. Twelve underwent conventional surgery and 12 were operated laparoscopically. Biopsies of the parietal peritoneum were taken at standardized moments during the procedure. Tissue concentrations of tissue-type plasminogen activator (tPA) and its specific activity (tPA-activity), urokinase-type plasminogen activator (uPA), and plasminogen activator inhibitor type 1 (PAI-1) were measured, using commercial assays.

RESULTS

After mobilization of the colon, peritoneal levels of tPA antigen and activity were significantly higher in the laparoscopic group (p < 0.005) due to a decrease in the conventional group (p < 0.05). At the end of the procedure, the concentrations of tPA antigen and activity significantly (p < 0.05) decreased in the laparoscopic group to levels comparable with the conventional group. Neither uPA antigen nor PAI-1 antigen changed throughout the procedures.

CONCLUSIONS

Both conventional and laparoscopic surgery inflict a decrease in tPA antigen and its specific activity. Peritoneal hypofibrinolysis initiates more rapidly during conventional, compared to laparoscopic, surgery, but at the conclusion of the surgery, the effect was the same.

Adenovirus-mediated overexpression of human tissue plasminogen activator prevents peritoneal adhesion formation/reformation in rats

BACKGROUND

Tissue-plasminogen activator (tPA) demonstrated beneficial effects on peritoneal adhesion formation; however, its short half-life limits its continual fibrinolytic effect. Therefore, we delivered adenovirus encoding tPA to prevent adhesions.

METHODS

Rats were subjected to peritoneal injury and assigned to two protocols. In de novo adhesion protocol, adenovirus encoding human tPA gene (Ad-htPA) was instilled after peritoneal injury in group 1 (n = 22), whereas group 2 received phosphate-buffered saline (PBS) (n = 24). In recurrent adhesion protocol, group 1 (n = 15) received the same Ad-htPA dose after adhesiolysis and group 2 (n = 13) received PBS. Adhesion severity was scored 1 week after ad-htPA instillation. Adhesions were analyzed for htPA mRNA by reverse transcription-polymerase chain reaction and levels of htPA, and fibrinolytic inhibitors PAI-1, TIMP-1, and TGF-beta1 were measured using enzyme-linked immunosorbent assay.

RESULTS

htPA mRNA and protein were only expressed in adhesions from treated groups. A reduction in adhesion scores (P < .01) and in fibrinolytic inhibitors (P < .001) occurred in the treatment groups. Also, negative correlation was found (r = -.69, P < .01) between adhesion scores and htPA protein, but a positive correlation was found (r = .90, P < .01) between adhesion score and fibrinolytic inhibitors. No bleeding or wound complications were encountered.

CONCLUSION

Administration of adenovector encoding htPA is safe and decreased de novo and recurrent peritoneal adhesions.

Preoperative predictors of postsurgical adhesion formation and the Prevention of Adhesions with Plasminogen Activator (PAPA-study): results of a clinical pilot study

OBJECTIVE

To identify predictors of postsurgical adhesion formation in peritoneal fluid and plasma, and assess efficacy and safety of reteplase (recombinant plasminogen activator [r-PA]).

DESIGN

Prospective randomized study.

SETTING

University Medical Center.

PATIENT(S)

Twenty-six abdominal myomectomy patients with early second-look laparoscopy (ESL).

INTERVENTION(S)

Randomization to IP treatment with 1 mg reteplase in 300 mL Ringer's lactate or 300 mL Ringer's lactate only. Scoring of adhesions and collecting peritoneal fluid during both surgical procedures and collecting plasma samples at ten time points.

MAIN OUTCOME MEASURE(S)

Incidence, severity, and extent of adhesions at ESL. Concentrations of C-reactive protein (CRP), tissue-type plasminogen activator (tPA), plasminogen activator inhibitor 1 (PAI-1), and fibrin degradation products (FbDPs).

RESULT(S)

Significant correlation between the extent of uterine adhesion formation and preoperative plasma levels of CRP (r(s) = 0.558), PAI-1 (r(s) = 0.413), and the change in tPA concentration in peritoneal fluid from initial surgery to ESL (Delta+PA: r(s) = -0.636). No significant differences in adhesion scores between treatment and control groups.

CONCLUSION(S)

Our finding that preoperative plasma CRP and PAI-1-levels are significantly correlated with extent of adhesion formation points to a role of chronic inflammation in the disease process. Results are highly indicative for the paradigm that adhesions are caused by an insufficiency in peritoneal fibrinolytic capacity. For successful adhesion prevention therapy relatively high amounts of r-PA are required.

Fibrinolytic responses of human peritoneal fluid in laparoscopic cholecystectomy: a prospective clinical study

BACKGROUND

The reduction in peritoneal fibrinolysis is believed to be the pathogenetic mechanism of adhesion formation. The general conclusion based on previous clinical and experimental studies is that laparoscopic procedures produce less adhesion formation. The association between this beneficial effect of laparoscopic cholecystectomy and peritoneal fibrinolytic changes is not clear. Therefore, the authors aimed to compare the effects of open and laparoscopic cholecystectomy on peritoneal fibrinolysis. For this purpose, fibrinolytic parameters in peritoneal fluid were investigated 24 h after laparoscopic and open cholecystectomies.

METHODS

In a prospective clinical study, peritoneal fluid was sampled via a drain 24 h after laparoscopic (n = 10) and open (n = 9) cholecystectomies. Activities and concentrations of tissue plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI-1), and tPA/PAI-1 complex were determined by enzyme-linked immunosorbent assay (ELISA) kits.

RESULTS

In peritoneal fluids, tPA and tPA/PAI-1 complex concentrations were higher in the open cholecystectomy group (p = 0.009 and p < 0.001, respectively), but tPA activity and PAI-1 concentrations did not differ between the groups (p = 0.514 and p = 0.716, respectively).

CONCLUSIONS

Fibrinolytic changes in peritoneal fluid have several similarities in open and laparoscopic cholecystectomies with regard to tPA activity and PAI-1 levels. However, higher tPA levels after the open procedure probably are secondary to more intense tissue handling leading to mesothelial release of tPA.

The difficult patient in gastroenterology: chronic pelvic pain, adhesions, and sub occlusive episodes

Chronic pelvic pain (CPP) with or without adhesions and symptoms of intestinal occlusion is a complex but relatively common complaint. The etiology and pathophysiology of CPP and adhesions are unclear, as is their possible relation. However, it is evident that continuous abdominal pain leads to evident suffering and disability. Unfortunately, there is little proof or evidence of success for many of the currently used diagnostic and therapeutic interventions. Laparoscopy is neither the ultimate evaluation nor the panacea for CPP or intra abdominal adhesions. An integral approach to CPP has shown beneficial results. In this multidisciplinary approach dealing with the pain is far more important than finding an organic cause and cure for the pain. Equal and simultaneous attention is paid to psychosocial, sexual and somatic aspects. The treatment of adhesions depends on the extent of symptoms and complaints. Because of the questionable relation between adhesions and pain, and the probability of reformation and de novo adhesion formation after surgery, adhesiolysis should be avoided. Even for patients with signs and symptoms of small bowel obstruction a conservative treatment is often justified. These patients require careful evaluation and management. Frequent reassessment is important to rule out impending strangulation, complete obstruction or perforation. Water soluble contrast can be useful to justify prolongation of conservative treatment and by that postpone unnecessary surgery. Most adhesive small bowel obstructions resolve following conservative treatment. The unsolved questions about etiology, diagnosis, treatment and prevention, and the great individual and community burden of CPP and adhesions clearly show that further research is needed.

Prevention of adhesions in gynaecological endoscopy

Adhesions resulting from gynaecological endoscopic procedures are a major clinical, social and economic concern, as they may result in pelvic pain, infertility, bowel obstruction and additional surgery to resolve such adhesion-related complications. Although the minimally invasive endoscopic approach has been shown to be less adhesiogenic than traditional surgery, at least with regard to selected procedures, it does not totally eliminate the problem. Consequently, many attempts have been made to further reduce adhesion formation and reformation following endoscopic procedures, and a wide variety of strategies, including surgical techniques, pharmacological agents and mechanical barriers have been advocated to address this issue. The present review clearly indicates that there is no single modality proven to be unequivocally effective in preventing post-operative adhesion formation either for laparoscopic or for hysteroscopic surgery. Furthermore, the available adhesion-reducing substances are rather expensive. Since excellent surgical technique alone seems insufficient, further research is needed on an adjunctive therapy for the prevention and/or reduction of adhesion formation following gynaecological endoscopic procedures.

Fibrinolytic characteristics and their significance in malignant, tuberculous and cirrhotic pleural and ascitic fluids

The fibrinolytic characteristics and clinical pathological significance of pleural and ascitic fluid were studied in patients with malignant tumour, tuberculosis or liver cirrhosis. Urokinase plasminogen activator (uPA) and urokinase plaminogen activator receptor (uPAR) levels were measured by enzyme-linked immunoadsorbent assay and tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), plasminogen (Plg), plasmin (Pl) and alpha(2) plasmin inhibitor (alpha(2)PI) by colorimetric assay. uPA and uPAR levels were higher in malignant tumour and tuberculosis compared with liver cirrhosis, whereas tPA levels were significantly higher in liver cirrhosis and malignant tumour than in tuberculosis patients. Tuberculosis patients showed statistically higher PAI-1, Plg and Pl concentrations than malignant tumour patients, which, in turn, were higher than those in liver cirrhosis patients. alpha(2)PI levels were markedly higher in malignant tumour and liver cirrhosis than in tuberculosis. In the malignant tumour group, only uPA level was significantly different between the samples that contained cancer cells and those that did not. We found significant differences between the fibrinolytic characteristics in pleural and ascitic fluid in patients with malignant tumour, tuberculosis and liver cirrhosis. The analysis of several fibrinolytic parameters could help to determine the quality of pleural and ascitic fluid, and also to further understand the pathological processes of these diseases.

Effect of oxidized regenerated cellulose (Interceed) on the expression of tissue plasminogen activator and plasminogen activator inhibitor-1 in human peritoneal fibroblasts and mesothelial cells

OBJECTIVE

To characterize the molecular changes that occur in normal fibroblasts, adhesion fibroblasts, and mesothelial cells as a result of exposure to oxidized regenerated cellulose (Interceed; Johnson & Johnson Medical, Inc., New Brunswick, NJ).

DESIGN

Control and Interceed-treated normal peritoneal fibroblasts, adhesion fibroblasts, and mesothelial cells in culture were assessed for messenger RNA levels of molecules known to be associated with adhesion development, using multiplex reverse transcriptase polymerase chain reaction (n = 4).

SETTING

University research laboratory.

PATIENT(S)

Normal and adhesion fibroblasts and mesothelial cells.

INTERVENTION(S)

Exposure of cells, normal fibroblasts, adhesion fibroblasts, and mesothelial cells to oxidized regenerated cellulose.

MAIN OUTCOME MEASURE(S)

Real-time reverse transcriptase polymerase chain reaction expression of messenger RNA tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), and tPA-PAI-1 ratio, an indicator of overall fibrinolytic activity.

RESULT(S)

Interceed treatment of normal peritoneal fibroblasts, adhesion fibroblasts, and mesothelial cells results in an increased expression of tPA in mesothelial cells and an increase in the tPA-PAI-1 ratio, signifying an overall increase in fibrinolytic activity.

CONCLUSION(S)

Interceed, which has been shown in multiple human in vivo studies to decrease postoperative adhesion development, increases the expression of tPA and the tPA-PAI-1 ratio (an indicator of overall fibrinolytic activity), thereby promoting dissolution of fibrin and healing without adhesion development. Thus, the ability of Interceed to reduce postoperative adhesion development may be derived from both a barrier and biologic effect.

Genetic polymorphism in the fibrinolytic system and endometriosis

OBJECTIVE

Although most women experience retrograde menses during their reproductive life, endometriosis develops only in a small percentage. We hypothesized that persistence of a fibrin matrix in peritoneal pockets, as a result of hypofibrinolysis, could allow menstrually deposited endometrial fragments to initiate endometriosis. Fibrinolysis is modulated by several factors, and polymorphisms in the plasminogen activator inhibitor-1 (PAI-1) gene are considered to be one of the important determinants. The objective of this study was to evaluate PAI-1 genotypes in a group of women with or without endometriosis.

METHODS

In 118 women (75 with laparoscopically confirmed endometriosis and 43 controls), genomic DNA was extracted from blood and the PAI-1 promoter genotype was determined by polymerase chain reaction amplification of DNA using specific primers for the 4G or 5G allele followed by gel electrophoresis. A portion of the polymerase chain reaction product was purified and sequenced to confirm the gel electrophoresis results.

RESULTS

Endometriosis was more likely in patients with 4G/5G (odds ratio 38; 95% confidence interval [CI] 6-229) or 4G/4G (odds ratio 441; 95% CI 53-3,694) compared with 5G/5G PAI-1 genotype. Fifty-two of 75 women with endometriosis (69 %, 95% CI 58-79%) had the 4G/4G genotype compared with only 5 of 43 (12%; 95% CI 4-25%) controls. In contrast, the 5G/5G genotype associated with normal fibrinolysis was found in 2 of 75 (3%; 95% CI 0-9%) women with endometriosis compared with 24 of 43 (56%; 95% CI 40-71%) controls.

CONCLUSION

Hypofibrinolysis, associated with the 4G allele of the PAI-1 gene, was found significantly more often in women with endometriosis compared with controls. Persistence of fibrin matrix could support the initiation of endometriotic lesions in the peritoneal cavity, explaining why some women with retrograde menstruation develop endometriosis while others do not.

LEVEL OF EVIDENCE

II-2.

Adenoviral-mediated gene expression of hepatocyte growth factor prevents postoperative peritoneal adhesion in a rat model

BACKGROUND

Mesothelial cell proliferation and migration play important roles in reducing formation of postoperative peritoneal adhesions. Hepatocyte growth factor (HGF) is a multifunctional cytokine that stimulates proliferation and migration of various cell types, including mesothelial cells.

METHODS

We investigated the effect of adenovirus-mediated HGF gene expression on the proliferation and migration of mesothelial cells and evaluated its preventive effects on postoperative formation of peritoneal adhesions. Rat mesothelial cells were isolated and characterized by expression of cytokeratin and vimentin.

RESULTS

Immunohistochemical staining showed that these cells expressed c-Met, the receptor for HGF. Adenoviral-mediated HGF gene transfer into mesothelial cells resulted in high expression of HGF and enhanced migration. To evaluate the preventive effects of adenoviral-mediated HGF gene transfer on the formation of postoperative peritoneal adhesion, we employed a rat model of cecum abrasion-induced adhesion formation in which 80% of the rats developed postoperative peritoneal adhesions. Local application of recombinant adenovirus carrying the HGF gene reduced adhesion formation in 16 of 20 control rats compared with 7 of 20 treated rats in this model.

CONCLUSIONS

These results suggest that adenoviral-mediated HGF gene transfer may be a novel strategy for preventing postoperative peritoneal adhesions.