The mesothelium was traditionally thought to be a simple tissue with the sole function of providing a slippery, nonadhesive, and protective surface to allow easy movement of organs within their body cavities. However, our knowledge of mesothelial cell physiology is rapidly expanding, and the mesothelium is now recognized as a dynamic cellular membrane with many other important functions. When injured, mesothelial cells initiate a cascade of processes leading either to complete regeneration of the mesothelium or the development of pathologies such as adhesions. Normal mesothelial healing is unique in that, unlike with other epithelial-like surfaces, healing appears diffusely across the denuded surface, whereas for epithelium healing occurs solely at the wound edges. This is because of a free-floating population of mesothelial cells which attach to the injured serosa. Taking advantage of this phenomenon, intraperitoneal injections of mesothelial cells have been assessed for their ability to prevent adhesion formation. This review discusses some of the functions of mesothelial cells regarding maintenance of serosal integrity and outlines the mechanisms involved in mesothelial healing. In addition, the pathogenesis of adhesion formation is discussed with particular attention to the potential role of mesothelial cells in both preventing and inducing their development.

Intra-abdominal adhesions are the most frequently occurring postoperative complication following abdomino-pelvic surgery. Abdominal and pelvic surgery can lead to peritoneal adhesion formation causing infertility, chronic pelvic pain, and intestinal obstruction. Laparoscopy today is considered the gold standard of care in the treatment of several abdominal pathologies as well as in a wide range of vascular diseases. Laparoscopy has several advantages in comparison to open surgery. These include rapid recovery times, shorter hospitalisation, reduced postoperative pain, as well as cosmetic benefits. The technological improvements in this particular surgical field along with the development of modern techniques and the acquisition of specific laparoscopic skills have allowed for its wider utilization in operations with fully intracorporeal anastomoses. Postoperative adhesions are caused by aberrant peritoneal healing and are the leading cause of postoperative bowel obstruction. The use of anti-adherence barriers is currently being advocated for their prevention. The outcome of the investigation showed adhesion formation inhibition without direct detrimental effects on anastomotic healing. Poor anasto-motic healing can provoke adhesions even in the presence of anti-adhesion barriers. This review gives a short overview on the current evidence on the pathophysiology and prevention of peritoneal adhesions.

Postoperative peritoneal adhesions are common sequelae of abdominal surgery. Acute as well as chronic complications, including bowel obstruction, abdominal pain and infertility can arise from adhesion formation. So far, the only reliable treatment is surgical adhesiolysis, which in turn is accompanied by an increased risk of adhesion recurrence. Despite significant progress in modern perioperative medicine, only limited prophylactic approaches are available and atraumatic surgery is still the most important factor.Current research concepts focus on two major antiadhesion strategies: firstly, the intraoperative placement of mechanical barriers and secondly novel immunomodulation concepts. Clinical data about the use of antiadhesive barriers show a heterogeneous outcome. Promising data have arisen from the immunomodulatory approaches and now require a step-up development from experimental to clinical trial level.The present review gives a short overview about the current research on the pathophysiology and prevention of peritoneal adhesions. The promising data are encouraging and require realization of carefully designed prospective clinical trials.

Adhesions are the most frequent complication of abdominopelvic surgery, yet the extent of the problem, and its serious consequences, has not been adequately recognized. Adhesions evolved as a life-saving mechanism to limit the spread of intraperitoneal inflammatory conditions. Three different pathophysiological mechanisms can independently trigger adhesion formation. Mesothelial cell injury and loss during operations, tissue hypoxia and inflammation each promotes adhesion formation separately, and potentiate the effect of each other. Studies have repeatedly demonstrated that interruption of a single pathway does not completely prevent adhesion formation. This review summarizes the pathogenesis of adhesion formation and the results of single gene therapy interventions. It explores the promising role of combinatorial gene therapy and vector modifications for the prevention of adhesion formation in order to stimulate new ideas and encourage rapid advancements in this field.

Postoperative intra-abdominal adhesions represent a serious clinical problem. In this review, we have focused on recent progress in the cellular and humoral mechanisms underpinning adhesion formation, and have reviewed strategies that interfere with these pathways as a means to prevent their occurrence. Current and previous English-language literature on the pathogenesis of adhesion formation was identified. As the burden of surgical disease in the world population increases, and the frequency of reoperation increases, prevention of adhesion formation has become a pressing goal in surgical research.

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.

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.

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.

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

The objective of the study was to evaluate whether a peptide derived from human lactoferrin, PXL01 could act safely to reduce the formation of peritoneal adhesions in the rat model and to map the molecular mechanisms of its action.

Adhesion formation is a significant problem within every surgical discipline causing suffering for the patients and major cost for the society. For many decades, attempts have been made to reduce postsurgical adhesions by reducing surgical trauma. It is now believed that major improvements in adhesion prevention will only be reached by developing dedicated antiscarring products, which are administrated in connection to the surgical intervention.

Anti-inflammatory as well as fibrinolytic activities of PXL01 were studied in relevant human cell lines. Using the sidewall defect-cecum abrasion model in the rat, the adhesion prevention properties of PXL01 formulated in sodium hyaluronate were evaluated. Large bowel anastomosis healing model in the rat was applied to study if PXL01 would have any negative effects on intestine healing.

PXL01 exhibits an inhibitory effect on the most important hallmarks of scar formation by reducing infections, prohibiting inflammation, and promoting fibrinolysis. PXL01 formulated in sodium hyaluronate markedly reduced formation of peritoneal adhesions in rat without any adverse effects on wound healing.

A new class of synthetically derived water soluble low molecular weight peptide compound, PXL01 showed marked reduction of peritoneal adhesion formation in an animal model without any negative effects on healing. On the basis of these data, a comprehensive adhesion prevention regimen in clinical situation is expected.

Plasma D-dimer concentration is a useful marker to assess systemic coagulation and fibrinolytic activities in humans, dogs, and horses. Peritoneal fibrinolytic activity increases in horses with colic, especially in horses with endotoxin in the peritoneal fluid.

Peritoneal D-dimer concentration can be used to assess peritoneal fibrinolytic activity in horses with severe gastrointestinal (GI) disorders and altered peritoneal fluid.

Two hundred and twenty-one colic horses and 15 control horses.

Prospective observational clinical study. Blood and peritoneal fluid were collected on admission. Horses were grouped according to diagnosis, peritoneal fluid analysis, and outcome. Peritoneal D-dimer concentration was determined, together with peritoneal tissue-plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1) activities. Plasma D-dimer concentration also was measured.

Peritoneal D-dimer concentration was significantly higher in all colic groups compared with controls, and in horses with enteritis, peritonitis, and ischemic disorders compared with horses with large intestinal obstructions. Peritoneal D-dimer concentration was significantly higher in horses with altered peritoneal fluid (modified transudate and exudate) compared with horses with normal peritoneal fluid analysis. Plasma D-dimer concentration also was significantly higher in the peritonitis group, and in horses with altered peritoneal fluid analysis. Peritoneal and plasma D-dimer concentrations also were significantly higher in nonsurvivors. Peritoneal d-dimer concentration was significantly correlated with decreased peritoneal t-PA activity and increased peritoneal PAI-1 activity.

Peritoneal D-dimer concentration is markedly higher in severe GI disorders, and it can be used to assess peritoneal fibrinolytic activity in horses with colic.

Formation of postoperative intra-abdominal adhesions is a severe problem in surgery. Apart from standard surgical procedures, a variety of different substances is available to prevent adhesions, but no universal method has been developed so far. A membrane consisting of polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC) has been demonstrated to be antiadhesive. Here, the in vitro testing and first in vivo results in a rabbit sidewall model are reported.

A-part membrane contains a PVA/CMC mixture in a thickness of 40 microm. The composition, dissolution, tensile strength, and elasticity were examined to characterize the membrane in vitro. Experiments in vivo were carried out using a 'rabbit sidewall model' in which a standardized peritoneal trauma was covered with a 5 x 6 cm A-part membrane. Adhesion formation in A-part-treated animals was compared with that in Adept (15 mL/kg body weight) and untreated controls.

An 80/20 PVA/CMC mixture forms a stable, elastic, transparent membrane, which can easily be placed intraoperatively. The dissolution shows a half-life of about 2 weeks [day 15: (45.1 +/- 4.9)% SD], which affords good adhesion protection during the initial critical phase of adhesion formation. In wet conditions, the membrane follows abdominal movements without tearing (tensile strength 5.0 +/- 4.2 N/cm SD; elasticity 29.5%). In a rabbit sidewall model, A-part membrane significantly reduced adhesion development by (83.1 +/- 31.5)% SD compared with the control and the Adept group (p < 0.001).

The properties of the A-part membrane suggest that it may be useful as an antiadhesive in surgery. A-part is effective in in vivo testing as determined in a rabbit sidewall model.

Forty adult female rats were randomly divided into four groups. Before the standard surgical procedure which consisted of creating a lesion with a lancet over the right uterine horn. Group I received no medication. Ringer's lactate (RL) solution was applied intraperitoneally to Group II at the end of the surgery. Sepracoat solution was applied intraperitoneally to Group III at the onset of the surgery. Group IV randomly received Seprafilm wrapped over the entire right uterine horn. Re-laparotomy was performed 3 weeks later to evaluate the adhesions. The mean adhesion scores were (mean+/-SD) 2.90+/-0.18, 1.00+/-0.36, 0.50+/-0.17 and 0.40+/-0.16 in Groups I, II, III, IV, respectively. The postsurgical adhesions were significantly less in the groups treated with Seprafilm and Sepracoat.

Peritonitis represents a procoagulant state because of activated coagulation and inhibited fibrinolysis. Intra-abdominal fibrin deposition-entrapping bacteria-prevents bacterial spread but impairs bacterial clearance. Activating intra-abdominal fibrinolysis by recombinant tissue-type plasminogen activator (r-tPA) early during peritonitis may enhance bacterial clearance and reduce inflammation. This study examines effects of abdominal r-tPA lavage on local and distant coagulation, fibrinolysis, and inflammatory responses in experimental polymicrobial peritonitis. Twenty-four hours after cecal ligation and puncture, mice were exposed to therapeutic abdominal lavage with varying doses of r-tPA or saline (controls). Coagulation, fibrinolysis, and inflammation were assessed in abdominal, systemic, and pulmonary compartments (n = 6 per group per time point). Survival was assessed during 96 h (n = 16 per group). Highest-dose (2 mg/mL) r-tPA lavage caused immediate death. High-dose (0.5 mg/mL) r-tPA lavage increased fibrinolysis, demonstrated by low abdominal plasminogen activator inhibitor 1 levels and elevated pulmonary tPA levels, resulting in reduced abdominal bacterial load, chemokine levels, leukocyte influx, and thrombin generation, along with less pulmonary fibrin depositions and organ damage on histological examination (P < 0.05 vs. saline lavage). Low-dose (0.05 mg/mL) r-tPA lavage showed hardly any effect compared with saline lavage. Adversely, abdominal and plasma interleukin (IL) 12 were elevated, whereas IL-10 levels were decreased after high-dose r-tPA lavage (P < 0.05 vs. saline). Survival rate was not affected by any dose of r-tPA lavage compared with saline lavage. Delayed local stimulation of fibrinolysis by peritoneal r-tPA lavage enhanced intra-abdominal bacterial clearance and reduced intra- and extra-abdominal coagulation responses in a dose-dependent manner. Survival rate was unaffected likely due to adverse changes in IL-12 and IL-10 levels.

Postsurgical adhesions severely affect the quality of life of millions of people worldwide. Numerous attempts have been made to prevent or reduce the incidence of peritoneal adhesions, but with limited success.

An extensive Medline search, textbooks, scientific reports and scientific journals are the data sources. We also reviewed reference lists in all articles retrieved in the search as well as those of major texts regarding postsurgical intraperitoneal adhesion formation.

A multifactorial approach including minimizing tissue injury, prophylactic antibiotic usage to reduce infectious morbidity, and biochemical agents with or without biomechanical barriers will reduce the amount and severity of adhesions. However, further research is needed to establish the safety, effectiveness and also the cost/benefit ratio of these substances in human subjects.

We investigated the effects of intraperitoneal tenoxicam on the development of postoperative intra-abdominal adhesions and oxidative stress in a model of bacterial peritonitis.

Bacterial peritonitis was induced in 24 rats by cecal ligation and puncture. The rats were randomly assigned to one of three groups. Group 1 (n = 8) received 2 ml saline intraperitoneally, group 2 (n = 8) received 2 ml (0.5 mg/kg) tenoxicam (Oksamen) intraperitoneally, and group 3 (n = 8) was a control, which did not receive any injection. All animals were killed 14 days later so we could assess the adhesion score and measure anastomotic bursting pressures. Tissue antioxidant levels were measured in 1-g tissue samples taken from the abdominal wall.

The adhesion score was significantly lower in the tenoxicam group than in the saline and control groups. The anastomotic bursting pressures were higher in the saline and tenoxicam groups than in the control group. The catalase (CAT) levels were higher in the saline and tenoxicam groups than in the control group. The malondialdehyde (MDH) levels were higher in the saline group than in the tenoxicam and control groups.

Intraperitoneal tenoxicam inhibited the formation of postoperative intra-abdominal adhesions without compromising wound healing in this bacterial peritonitis rat model. Tenoxicam also decreased the oxidative stress during peritonitis.

Abdominal surgery can lead to intra-abdominal adhesions with significant morbidity and mortality. To prevent adhesions, an experimental study was planned to designate the effects of low molecular weight (LMW) heparins and hyperbaric oxygen (HBO) therapy both on the formation of adhesions and wound healing.

Thirty-eight Wistar albino rats underwent laparotomy to cause intra-abdominal adhesions by mechanical abrasion of the cecum and ethanol application. The rats were divided into 4 groups. In the control group (group 1) no further management was undertaken. Group 2 was treated by Enoxaparine Na, group 3 received HBO therapy, and group 4 was given both enoxaparine Na and HBO treatment.

There was a statistically significant difference between the control and enoxaparine Na groups regarding adhesions. Statistically significant differences were observed between groups 1 and 4 and between groups 1 and 3 regarding the hydroxyproline content of the abdominal wounds. In the pathologic analysis of the abdominal wounds, there was no statistically significant difference between any of the groups, including the control group, regarding inflammation. Statistically significant differences were observed regarding angiogenesis between the control group and groups 3 and 4. There was also a statistically significant difference regarding fibrosis between groups 1 and 4.

Enoxaparine Na decreased intra-abdominal adhesions, and HBO therapy had no beneficial effect on adhesions. Enoxaparine Na had no harmful effects on wound healing, and HBO therapy increased the process of wound healing.

Failure of fibrinolysis of the inflammatory fibrin exudate which appears following peritoneal trauma allows fibroblast in-growth and neovascularization of the fibrinous adhesion to develop a fibrous adhesion.

To describe the sonographic features of peritoneal pseudocysts (PPCs) in order to determine the particular aspects that distinguish them from true ovarian cysts.

Thirty-one women with PPCs were investigated using transvaginal sonography immediately before surgery. The diameters of the cysts were measured, and the shape, margins, content, location, presence of septa and echogenic portions were analyzed.

The PPCs were monolateral in 20 (65%) and bilateral in 11 (35%) women. A well-defined cystic structure was found in only six (19%) women, while in the other 25 (81%) women the PPCs showed blurred, undefined margins and a bizarre morphology, giving them a star-like tubular or lumpy shape. The ipsilateral ovary was identified in 26 (84%) cases either external to the cyst or entrapped within it like a 'spider in a web'. Septa were present in 25 (81%) cases and were often mobile, resembling a 'flapping sail' when touched by the endovaginal probe.

Despite having a gross morphology resembling that of a true ovarian cyst, PPCs present some characteristic sonographic findings that allow a correct differential diagnosis in the vast majority of cases.

To establish the influence of the peritoneal sampling technique on the measurement of fibrinolytic capacity.

Clinical study.

University hospital, Germany.

40 peritoneal biopsy specimens were taken from 10 patients who were having elective colorectal resections.

Peritoneal biopsy specimens were taken either with a biopsy punch (n = 20) or manually with forceps and scissors (n = 20).

Extent of agreement in fibrinolytic activities between specimens taken with biopsy punch and manually. Major endpoint-peritoneal tissue plasminogen activator (t-PA) activity. Minor endpoints-peritoneal tissue plasminogen activator concentration, and concentration and activity of plasminogen activator inhibitior type 1 (PAT-1).

Intra-assay agreement and the extent of agreement between the groups were evaluated by the method of Bland and Altman. Correlation of repeated measurements of t-PA and PAI-1 concentrations and activities from the same sample using the same ELISA kit was high (r = 0.93-0.99, p < 0.01). t-PA activities and concentrations between the groups correlated poorly (r= 0.60 and 0.66, p < 0.01) while no correlation at all was seen for PAI-1 concentration and activity between the groups (r = 0.6 and 0.1, p = 0.2 and 0.9). The mean differences between the groups ranged from -27% to -4.8%.

The sampling technique considerably affects the measurement of peritoneal fibrinolytic activity.

To evaluate the role of plasminogen activator inhibitor-1 (PAI-1), urokinase plasminogen activator (uPA), and tissue-type plasminogen activator (tPA) in adhesion formation after laparoscopic surgery.

Prospective, randomized study.

Academic research center.

Seventy female wild-type and transgenic knockout mice for PAI-1 (PAI-1(-/-)), uPA (uPA(-/-)) or tPA (tPA(-/-)).

Standardized lesions to induce peritoneal adhesions were performed during laparoscopy. To evaluate basal adhesions and pneumoperitoneum-enhanced adhesions, the pneumoperitoneum was maintained for 10 minutes or 60 minutes, respectively. Peritoneal biopsy samples were obtained during and after 60 minutes of carbon dioxide pneumoperitoneum.

Adhesions were blindly scored after 7 days. Concentrations of PAI-1 and tPA were measured by using enzyme-linked immunosorbent assay.

In PAI-1, uPA, and tPA wild-type mice, pneumoperitoneum enhanced adhesions. Compared with wild-type mice, basal adhesions were fewer in PAI-1(-/-) mice and more in uPA(-/-) and tPA(-/-) mice. Pneumoperitoneum did not enhance adhesions in these transgenic mice. PAI-1 concentration increased after 60 minutes of pneumoperitoneum whereas tPA concentration did not change.

Impaired fibrinolysis increases basal adhesions. The absence of pneumoperitoneum-enhanced adhesions in PAI-1(-/-), uPA(-/-), and tPA(-/-) mice and the increase in PAI-1 expression indicate that PAI-1 up-regulation by carbon dioxide pneumoperitoneum is a mechanism of pneumoperitoneum-enhanced adhesion formation.

Peritonitis may cause a reduction in abdominal fibrinolytic activity. The reduced local fibrinolysis seems to be an important process in the subsequent development of adhesion formation. The aim of the study was to evaluate peritoneal fibrinolytic capacity in inflamed and normal peritoneum.

Peritoneal biopsy specimens were taken at the beginning of operation from 15 patients with peritonitis and 10 patients who underwent elective operation. Levels of tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA), plasminogen activator inhibitor (PAI) type 1 (PAI-1) and type 2 (PAI-2), and tPA/PAI complex in tissue extracts were determinated by commercially available enzyme-linked immunosorbent assay kits.

tPA was significantly reduced in peritonitis compared with normal peritoneum (P <0.001), whereas it was found that the levels of PAI-1, PAI-2, uPA, and tPA/PAI complex in peritonitis were significantly higher than those in normal controls.

Plasminogen activator activity was significantly reduced in peritoneal biopsy samples from patients with peritonitis compared with those from patients without peritonitis.

Reduction in the thrombogenicity of small-caliber synthetic vascular grafts by lining them with mesothelial cell has been suggested as a method to reduce thrombosis. The purpose of this research is to determine whether creation of a mesothelial lining on the inner surface of a synthetic vascular graft would improve the patency rate of a small-caliber vascular grafts. Carotid interposition grafting was performed using mesothelial-lined grafts (MLG) in 30 New Zealand rabbits and compared with similar carotid interposition grafts using non-mesothelial-lined grafts (NLG) on the contralateral side. The mesothelial lining was created by suturing a piece of harvested peritoneum with the visceral surface toward the lumen onto a 2-mm polytetraflouroethylene (PTFE) graft. Graft patency was studied by in vivo Dopler. In vitro evaluations were done with hematoxylin-eosin stains, broadband cytokeratin staining, and monoclonal antibodies for macrophages. Explanation of the grafts was done in terminal operation at 7, 14, and 21 days. The MLG showed progressive fibroblastic proliferation in direct proportion to the age of the graft, but this did not lead to graft occlusion. However, a significant number of NLG were not patent at each time period studied. We concluded that mesothelial cell lining of smallcaliber PTFE grafts could enhance the short-term patency more than using the PTFE without the mesothelial lining. The use of such hybrid small-caliber grafts has a potential for improving the patency of these artificial vascular graft substitutes.

Cesarean section (CS) is the commonest major operation carried out in many low income countries. A new technique for CS, called the Misgav Ladach procedure, was evaluated in a randomized trial in Nazareth Hospital (Kiambu District, Kenya). A total of 160 patients were assigned to the Misgav Ladach procedure (n = 80) or to the traditional CS as performed in most rural hospitals in low income countries (n = 80). The two groups were analyzed by operating time, presence of infection and febrile morbidity, grade of postoperative pain, starting of fluid and solid alimentation, and development of incisional hernia and hypertrophic scar. The operating time of the Misgav Ladach procedure was significantly shorter. 20.4 (SD 6.1) minutes versus 30.4 (SD 6.1) minutes (p < 0.001). A total of 5 wound infections (6.2%) were seen with the Misgav Ladach procedure versus 16 (20.0%) in the control group (p = 0.01). The number of analgesic doses required during the postoperative period were significantly less in the Misgav Ladach group: 1.3 (SD 0.6) versus 1.9 (SD 0.7) ampuls of pethidine (p < 0.001) and 15.1 (SD 2.0) versus 16.4 (SD 1.8) tablets of ibuprofen (p < 0.001). Incisional pain was significantly less in the Misgav Ladach group: Visual Analogue Scale score 3.0 (SD 1.5) versus 4.9 (SD 2.0), p < 0.01. The patients in the Misgav Ladach group began drinking fluids voluntarily [19.1 (SD 4.5) hours versus 20.6 (SD 4.0) hours; p = 0.01] and eating solid food [41.2 (SD 9.3) hours versus 46.1 (SD 9.0) hours; p < 0.01] significantly before than those in the control group. At the 6-week follow-up, the presence of hypertrophic scar was significantly associated with the traditional procedure (2.1% vs. 48.8%; p < 0.001). We conclude that the Misgav Ladach operation should become the standard method for performing CS in low income countries, particularly in rural hospitals.

The mesothelium has an important role in maintaining an adequate fibrinolytic capacity in the peritoneal cavity and thus in preventing the formation of fibrinous peritoneal adhesions by secreting the fibrinolytic enzyme tissue-type plasminogen activator (t-PA). The fibrinolytic activity of human mesothelial cells (HMCs) is counteracted by rapid uptake of t-PA via the low-density lipoprotein receptor-related protein (LRP). The 39 kD receptor-associated protein (RAP) is an inhibitor of binding of t-PA to LRP, but RAP itself is also rapidly degraded via LRP.

Adenovirus-mediated RAP gene transfer technology was used to evaluate the effect of prolonged overexpression of RAP on t-PA accumulation in conditioned medium of HMCs under basal and inflammatory conditions.

Infection of HMCs with a recombinant adenovirus carrying the RAP cDNA resulted within one day in t-PA levels that were maximally twofold to threefold increased as compared with noninfected or adenovirus-beta-galactosidase-infected cells. Whereas upon prolonged incubation, t-PA levels in the conditioned medium of uninfected cells leveled off because of rapid uptake and degradation via LRP, t-PA concentrations in the medium of adenovirus-RAP-infected cells continued to increase, reaching fivefold control levels after 72 hours. The increased t-PA accumulation persisted for seven days and then slowly returned to control values over the next few weeks. In contrast, the production of a specific inhibitor of t-PA, plasminogen activator inhibitor-1 (PAI-1), was not affected by adenoviral RAP gene transfer. Northern blotting analysis showed that t-PA, PAI-1, and LRP mRNA concentrations were not changed after adenoviral infection, underlining that the elevated t-PA levels are the result of RAP-blocked uptake and degradation of t-PA rather than increased t-PA synthesis. RAP gene transfer also restored diminished fibrinolytic activity of cytokine-treated mesothelial cells.

Adenovirus-mediated transfer of the RAP gene provides an efficient way of transiently increasing the fibrinolytic capacity of mesothelial cells.

Reduction in peritoneal fibrinolytic capacity and increased transforming growth factor-beta1 (TGF-beta1) production are associated with adhesion development. This study investigated the expression of TGF-beta1 in peritoneal tissue, and possible correlation with components of the fibrinolytic system locally in peritoneal tissue.

Peritoneal samples were taken from 22 patients at relaparotomy. Samples of adhesions were collected from 10 patients. The patients were categorized into different groups depending on the quantity and the quality of adhesions. TGF-beta1 and components of the fibrinolytic system in tissue extracts were assayed using enzyme-linked immunosorbent assays.

The concentration of active TGF-beta1 in peritoneal samples from patients with extensive adhesions was double (P <.01) that of healthy subjects, but the total levels of TGF-beta1 were similar (P =.63). In adhesion tissue, both active (P <.003) and total (P <.008) TGF-beta1 concentrations were more than twice as high as unaffected peritoneum. There was a significant correlation between the concentration of plasminogen activator inhibitor type 1 in peritoneal samples with active TGF-beta1 (P <.03, r = 0.693) and adhesion tissue with total TGF-beta1 (P =.001, r = 0.872). The other components of the fibrinolytic system did not correlate significantly with TGF-beta1.

These data indicate that an overexpression of TGF-beta1 is associated with adhesion formation, possibly through a mechanism involving local regulation of plasminogen activator inhibitor type 1.

Intra-abdominal adhesions are an important surgical problem. Colorectal operations are a major cause of adhesive obstruction. Radiation therapy (RT) is frequently used as an adjuvant therapy to surgery for rectal cancer, though its value for colon carcinoma remains unclear. Peritoneal injuries including the surgical trauma, tissue ischaemia as well as RT are associated with peritoneal fibrinolytic activity. A sodium hyaluronate and carboxymethylcellulose bioresorbable membrane (Seprafilm) has been used to reduce intra-abdominal adhesion formation. We have investigated the effect of Seprafilm on intra-abdominal adhesion in rats receiving RT after the resection of the left colon.

Thirty-two male Wistar rats were divided into two groups: group 1 (n=16), control (colon resection, no Seprafilm); group 2 (n=16), study group (colon resection and Seprafilm). All the rats received 50 Gy RT after left colon resection. Intra-abdominal adhesions were evaluated by grading and measurement of tissue-type plasminogen activator (tPA) as a tissue adhesion marker in peritoneal samples from the rats. tPA was determined using a commercially available ELISA kit.

The levels of tPA were significantly increased in group 2 rats compared with those in the control group (P=0.0276). It was also seen that adhesions in the rats receiving Seprafilm were significantly less severe than those in the control group.

Our findings suggest that the intraperitoneal administration of Seprafilm reduced the frequency and strength of adhesions.

The formation of postoperative adhesions is an inevitable sequel to surgical intervention, and, as part of the healing process, they are often beneficial. Nevertheless, the presence of adhesions may impose postoperative and reoperative surgical problems. An overview of some of the attempts to overcome such problems is presented, and the research surrounding them is discussed.

To review the events leading to the formation of adhesions, to describe the development of fibrinolytic agents, to review more than a century of research on the use of fibrinolytic agents in adhesion prevention, and to look at future aspects of adhesion prevention.

A better understanding of the pathogenesis of adhesion formation has resulted in the use of fibrinolytic agents in their prevention. Fibrinolytic agents promote fibrinolytic activity during the early period after peritoneal trauma during which an increased formation of fibrin is seen in combination with a deficiency of endogenous fibrinolytic activity. Initially, chemical attacks on fibrin (fibrolysin and hypertonic glucose), foreign digestive ferments (pepsin, trypsin, and papain), and stimulation of intraperitoneal leukocytosis (amniotic fluid) were used. Development of new thrombolytic agents was soon followed by experiments in animal adhesion models and clinical studies to examine their antiadhesion properties. Plasmin preparations (plasmin, actase, and fibrinolysin) and plasmin activators (streptokinase, urokinase, and tissue-type plasminogen activator) were found to be efficacious in preventing adhesion formation in the greater part of reviewed animal and clinical studies.

From the current literature, it can be concluded that postoperative intraperitoneal administration of thrombolytic agents can significantly decrease adhesion formation. Given the large number of experimental studies in animals, future studies should focus on the clinical use of fibrinolytic agents in the prevention of postsurgical adhesion formation.

The objective of this study was to establish a technique to isolate porcine mesothelial cells (PMCs) from omental tissue and to compare them to human mesothelial cells (HMCs). The PMCs were dispersed by collagenase digestion and isolated on a Ficoll layer. Their morphologic and ultrastructural features were assessed at confluence by light and electronic microscopy, and they were characterized by immunohistochemistry using specific HMC markers. PMC proliferation was studied in the presence of growth factors platelet-derived growth factor (PDGF), epidermal growth factor (EGF) or transforming growth factors beta1, beta2, or beta3 (TGF). Fibrinolytic PMC activity was detected by zymography for tissue plasminogen activator (tPA) and by reverse zymography for plasminogen activator inhibitor-1 (PAI-1). The recalcification time of cell lysates was used to define PMC procoagulant activity, and gelatinase zymography was used to detect metalloproteinase production. At confluence, PMCs formed typical cobblestone monolayers and exhibited structural features characteristic of HMCs. Weibel Palade bodies were never seen. Specific HMC markers (HBME1, ME1, WT1) cross-reacted with PMCs. As HMCs and PMCs coexpressed cytokeratin and vimentin, and also expressed vinculin and alpha-actin. Addition of PDGF or EGF to the culture medium stimulated PMC proliferation. PMCs constitutively expressed fibrinolytic and procoagulant activity and secreted MMP9 and MMP2. The technique described in this study allows isolation of mesothelial cells from porcine omental tissue. These porcine cells exhibit a mesothelial phenotype and functional properties similar to those of HMCs. Our data warrant an evaluation of mesothelial cells as targets in several therapeutic strategies with porcine models.

To examine the effectiveness of a cross-linked hyaluronan solution (auto-cross-linked polysaccharide [ACP] gel) for the prevention of postsurgical adhesions.

A randomized blinded study using a rat model of laparotomy.

Surgical Research Laboratory in a university medical school.

Sixty-seven sexually mature rats.

Standardized surgical trauma was induced in the rat uterine horn to induce adhesion formation. After trauma, group-1 animals (n = 23) received no treatment, group 2 (n = 21) received noncross-linked hyaluronic acid (HA), and group 3 (n = 23) received cross-linked HA applied on the lesion.

Six weeks after laparotomy, repeat laparotomy was performed and the adhesions were scored according to Blauer's scoring system.

Overall, 84% of the untreated animals and 65% of the animals treated with noncross-linked HA presented with severe adhesions. The mean (+/-SEM) increase in the adhesion score was 2.46+/-0.23 in the untreated group, 2.23+/-0.29 in the group receiving noncross-linked HA, and 1.27+/-0.12 in the ACP gel group.

ACP gel holds promise as a novel resorbable biomaterial for the reduction of postoperative adhesions after laparotomy.

Intraabdominal adhesions are a common complication following laparotomy. Since the exact mechanisms involved in this processes are unknown we have analyzed in vitro the role of mesothelial cells in peritoneal healing.

Human mesothelial cells from omental tissue were cultivated for 2 weeks in a three-dimensional culture either on or in a collagen type I matrix. The effects of blood and collagen matrix were analyzed by exposing mesothelial cells to an overlying blood clot, simulating intraperitoneal bleeding, or a second collagen layer. The production of collagen types III and IV, fibronectin, and laminin was analyzed with immunohistochemical methods.

Mesothelial cells grown on a collagen matrix formed a monolayer of flat or cobblestone-like cells whereas those cultivated in a collagen matrix exhibited spindle-like morphology. Mesothelial cells failed to grow into an overlying collagen matrix, but did grow into a blood clot, emphasizing a potential role of blood clots in peritoneal adhesion formation. Independent of the culture systems mesothelial cells produced collagen type III, fibronectin, and laminin but not collagen type IV.

Our experiments demonstrate remodeling of peritoneal-like structures by mesothelial cells in a three-dimensional culture reflecting their putative role in the reepithelialization after serosal defects, and also in the formation of peritoneal adhesions.

The development of postoperative intraperitoneal adhesions continues to be a major concern for surgeons. The purpose of this study was to establish a postoperative adhesion model in rats, and to assess the effectiveness of tranilast (N-(3',4'-dimethoxycinnamoyl)anthranilic acid) in preventing postoperative adhesion formation. The adhesion model was established in 12 male Donryu rats. This involved two essential factors, drying and bleeding. Another 22 male Donryu rats were used to study the prevention of intraperitoneal adhesions. Tranilast was administered orally pre- and postoperatively. Adhesion strength was evaluated by grading, and basic fibroblast growth factor (bFGF) and transforming growth factor-beta-1 (TGF-beta1) concentration were measured. Postoperative intraperitoneal adhesions were seen in all rats, but the adhesions in the tranilast group were significantly less severe than those in the control group. Serum bFGF and TGF-beta1 levels in the tranilast group were lower at the time of surgery than those in the control group, and bFGF levels were lower at the endpoint of this study in the tranilast group than in the control group. The TGF-beta1 levels at the end-point did not differ between the two groups. These findings demonstrated that tranilast significantly reduced postoperative intraperitoneal adhesion formation.

Human mesothelial cells (HMCs) have an important role in maintaining an adequately functioning fibrinolytic system in the peritoneal cavity by secreting the fibrinolytic enzymes tissue-type and urokinase-type plasminogen activator (t-PA and u-PA), as well as a specific PA inhibitor, PA inhibitor type 1 (PAI-1). In this study, we investigated whether the fibrinolytic capacity of HMCs is further counterbalanced by rapid uptake of t-PA and u-PA from the medium.

Cultured HMCs were used to study the uptake and degradation of radiolabeled t-PA and u-PA in the absence or presence of an inhibitor of cellular protein degradation, chloroquine, and of specific receptor antagonists. Northern blotting and ligand-blotting techniques were applied to demonstrate the presence of specific receptors for binding of t-PA and u-PA.

At 37 degreesC, HMCs rapidly internalized and degraded 125I-t-PA and 125I-u-PA, which could be inhibited by an excess of unlabeled t-PA and u-PA, respectively, and by the lysosomotropic agent chloroquine. Northern blot analysis showed the expression of low-density lipoprotein (LDL) receptor-related protein (LRP), very low density lipoprotein (VLDL) receptor, and u-PA receptor. The addition of recombinant 39 kDa receptor-associated protein (RAP; an inhibitor of LRP and VLDL receptor) almost completely blocked the degradation of t-PA and partly that of u-PA. RAP ligand blotting demonstrated predominantly the presence of LRP, suggesting a major role for the LRP in mediating uptake and degradation of t-PA in HMCs. Endocytosis of u-PA occurs via two different pathways. After binding to u-PA receptor, a RAP-inhibitable and a non-RAP-inhibitable route for u-PA degradation was demonstrated. Tumor necrosis factor alpha (TNFalpha) diminished the fibrinolytic activity of HMCs by decreasing t-PA and increasing PAI-1 synthesis. The fall in t-PA levels could be counteracted by inhibiting t-PA degradation by either RAP or chloroquine. Interestingly, chloroquine also quenched the TNFalpha-induced changes in t-PA and PAI-1 mRNA levels. Using TNFalpha mutants and agonistic or blocking monoclonal antibodies specific for the TNF receptors p55 and p75, we found evidence that chloroquine interfered with the activation of the TNF receptor p55 and/or its intracellular signaling route.

Receptor-mediated endocytosis plays a crucial role in regulating the fibrinolytic capacity of HMCs by its participation in the degradation of t-PA and u-PA, and in the TNFalpha-induced decrease in t-PA and the increase in PAI-1 expression.

Small-diameter vascular grafts tend to have an early and high occlusion rate. Cell seeding on the luminal surfaces of small-diameter vascular prostheses may provide an antithrombotic lining and improve both the short-term and the long-term patency rates. We studied the net results of procoagulant and anticoagulant properties of seeded grafts under blood-flow conditions, and we compared the different available types of donor cells.

Monolayers of liposuction-derived cultured human microvascular endothelial cells (MVECs), human adult endothelial cells (HAECs), human umbilical vein endothelial cells (HUVECs), and human mesothelial cells (MCs) that had been seeded on expanded polytetrafluoroethylene (ePTFE) grafts were perfused with marginally anticoagulated blood (20 U/mL low molecular weight heparin; shear rate, 400/s, 10 minutes) or with non-anticoagulated blood (shear rate, 100/s, 5 minutes). The thrombin and fibrin generation in time was studied with the measurement of the plasma levels of prothrombin fragment 1 and 2 (F 1+2) and of fibrinopeptide A (FPA). The plain ePTFE graft was taken as a control.

When the seeded MCs were perfused with recirculating anticoagulated blood, a linear generation of F 1+2 in time was seen, with high levels of F 1+2 and FPA after 10 minutes (4.38 nmol/L and 362 ng/mL, respectively). Allopurinol was added, and the MCs generated less F 1+2 than the HAECs (0.7 nmol/L vs 1.86 nmol/L; P <.05). No fibrin formation was seen. The MVECs generated low amounts of F 1+2 (0.7 nmol/L; 10 minutes), and the HUVECs and the plain ePTFE graft generated the lowest amounts of F 1+2 (0.26 and 0.25 nmol/L, respectively). When the MCs were perfused with non-anticoagulated blood, high amounts of thrombin and fibrin were generated immediately and constantly and could not be decreased with allopurinol. The perfusion of the plain ePTFE graft showed a dramatic increase in F 1+2 and FPA levels towards the end of the experiments. The seeded HAECs, HUVECs, and MVECs inhibited this increase. These results were confirmed by means of scanning electron microscopy.

Vascular prostheses that are seeded with cultured MCs are highly procoagulant. Standard ePTFE graft prostheses also initiate coagulation, which supports the idea of cell seeding. The endothelial cells, of which the MVECs are the most readily available, seem to preserve their anticoagulant properties after being seeded on vascular grafts.

Postoperative adhesion formation has been associated with a decreased capacity to degrade intra-abdominally deposited fibrin. Adhesions, once lysed, have a high propensity for reformation. This study tested the hypothesis that patients with a high propensity for adhesion formation as well as adhesion tissue had a reduced fibrinolytic capacity.

Peritoneal biopsies were taken during abdominal surgery from 21 patients who had previously undergone operation; previously formed adhesion tissue was sampled from ten of these patients. Adhesion formation was scored. The fibrinolytic capacity of peritoneum was determined in tissue extracts.

At the time of opening of the abdominal cavity, levels of plasminogen activator inhibitor (PAI) type 1 (P = 0.009) and tissue-type plasminogen activator (tPA)/PAI complex (P = 0.008) were increased in peritoneal samples from patients with severe adhesions compared with those in samples from patients with less severe adhesions. Adhesion tissue similarly had reduced fibrinolytic capacity as judged by a decrease in tPA activity (P = 0.005) and an increase in PAI-1 level (P = 0.01), reflected in an increased level of tPA/PAI complex (P = 0.008) compared with unaffected peritoneum.

These observations demonstrate reduced fibrinolytic capacity in peritoneal tissue in patients with a greater propensity for development of adhesions and likewise in adhesion tissue. This suggests that components of the fibrinolytic system may be used as markers of an increased risk of adhesion development.

The aim of this retrospective study was to determine the cumulative incidence of adhesive small bowel obstruction (SBO) after total or subtotal colectomy and to investigate the site of the obstructive adhesions in the abdominal cavity.

The records of 234 patients who underwent colectomy from 1985 to 1994 were reviewed for SBO, potential risk factors for SBO, and the site of adhesions causing obstruction. Mean follow-up, which was complete in 215 patients, was 63 months.

SBO occurred in 56 patients (24 per cent) of whom 42 (18 per cent) had adhesive obstruction. The risk of SBO due to adhesions within 1 year was 11 per cent, increasing to 30 per cent 10 years after colectomy. With univariate analysis no risk factor for adhesive SBO, including previous laparotomies, septic complications and omental resection, was identified. The most common site of obstructing adhesions was the pelvis (ten of 28 patients).

The incidence of SBO after colectomy is high. Colectomy may be a suitable model for studies of adhesion prevention.

To evaluate the effects of a gonadotropin-releasing hormone agonist (GnRH-a) on plasminogen activator (PA), matrix metalloproteinase (MMP), plasminogen activator inhibitor (PAI) and matrix metalloproteinase inhibitor (MMPI) activities in peritoneal fluid relative to GnRH-a-induced reduction of adhesion formation.

Continuation of prospective randomized study using surgical models for adhesion formation.

Department of Obstetrics and Gynecology research laboratory at the University of Missouri School of Medicine.

Forty reproductively cycling female Sprague-Dawley rats.

Female rats were injected with depot GnRH-a or diluent and randomly assigned to adhesion and endometriosis surgeries. Peritoneal fluid was collected prior to (time 1) and 7 weeks from (time 2) initial surgery.

Peritoneal fluid was analyzed for PA, PAI, MMP, and MMPI activities.

At time 1, MMP and MMPI activities were similar in all rats; however, PA and PAI activities were less in rats pretreated with GnRH-a than with diluent. Between time 1 and time 2, GnRH-a-treated rats showed an increase in PAI and MMPI activities without significant changes in PA or MMP activities, whereas rats receiving diluent showed a significant increase in PAI and MMP activities but no significant changes in PA or MMPI activities. At time 2, rats receiving GnRH-a had less PA and MMP activities than those receiving diluent. Adhesion scores showed a positive correlation with MMP activity.

In the absence of GnRH-a therapy, surgical tissue manipulation increased peritoneal fluid MMP and PAI activity. Gonadotropin-releasing hormone agonist therapy decreased PA and MMP activities and also increased PAI and MMPI activities. This GnRH-a-induced shift to a less invasive phenotype may alter fibrinolysis and extracellular matrix remodeling and thereby play a role in the mechanism of GnRH-a-induced reduction in adhesion formation.

Peritoneal fibrinolytic capacity decreases during abdominal operation. This may be a local effect or a part of a generalized response to the procedure.

Plasma and paired peritoneal biopsy specimens were taken at intervals during abdominal operation, and fibrinolytic components were assayed in plasma and tissue extracts. Values are given as median [interquartile range].

In peritoneal tissue there was a gradual decrease of tissue-type plasminogen activator (tPA) activity, and at 90 minutes of the operation differed significantly from that of the initial sample (1.0 [1.0] ng/mg protein, and 5.1 [6.5] ng/mg protein, respectively, p < 0.05). The tPA activity levels at the wound were significantly lower (1.0 [1.0] ng/mg protein) at 90 minutes compared with a remote peritoneal site (1.8 [1.9] ng/mg protein, p < 0.05). At the wound, the tPA activity correlated significantly with time (r = -0.48, n = 26, p < 0.01). tPA activity and antigen peaked in plasma at 30 minutes (p < 0.05) and 60 minutes (p < 0.05), respectively. Plasminogen activator inhibitor type 1 activity increased in plasma during operation (p < 0.05), but was not detectable in peritoneal samples.

The intraoperative changes in tissue tPA activity were not consistently reflected in plasma samples. These findings suggest that the reduction in peritoneal fibrinolysis during abdominal operation is a local response to trauma.