Localization of plasminogen activator inhibitor-1 production in inflamed appendix by in situ mRNA hybridization

Post-Operative Adhesions: A Comprehensive Review of Mechanisms

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

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

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

Progress of tissue injury in appendicitis involves the serine proteases uPA and PAI-1

OBJECTIVE

Serine proteases and the matrix metalloproteinases (MMPs) are key factors in the proteolytic cascade and participate in extracellular matrix (ECM) degradation. Fibrinolytic activators and inhibitors may have an effect on inflammatory cells, thereby modulating the inflammatory response. It is reasonable to assume that they may be implicated in the tissue injury in acute appendicitis that subsequently leads to appendix perforation. The purpose of this study was to investigate the expression and distribution of urokinase-type plasminogen activator (uPA) and plasminogen-activator inhibitor type 1 (PAI-1) in appendicitis.

MATERIAL AND METHODS

Expression of uPA and expression of PAI-1 were measured in tissue specimens from patients with appendicitis (n=30) and in control specimens (n=9), using the quantitative ELISA technique. Distribution of enzymes was studied with immunohistochemistry. The uPA and PAI-1 levels in the subgroups of appendicitis and controls were compared.

RESULTS

The overall expressions of uPA and PAI-1 were greater in appendicitis than in control specimens (p <0.001 and p<0.0001, respectively). Expressions of uPA and PAI-1 in phlegmonous (n=15), gangrenous (n=6) and perforated appendicitis (n=9) were all higher than those in controls (n=9), (p<0.01). Moreover, the PAI-1 level was elevated in perforated appendicitis compared with phlegmonous appendicitis (p<0.01). uPA staining was observed in connection with vascular endothelial cells and the serosa stained intensely in specimens from perforated appendicitis.

CONCLUSIONS

The expression of uPA and especially the over-expression of PAI-1 seem to correlate to the progression of local inflammatory response in acute appendicitis.

Vascular development in endometriosis

Endometriosis, defined as the presence of endometrial tissue outside the uterus, is an estrogen-dependent disease which causes pelvic pain and subfertility in women of reproductive age. The condition has a dramatic impact on the professional, social and marital life of sufferers. Direct and indirect evidence suggests that angiogenesis is required for the development and persistence of endometriosis. In this review the state-of-the-art with regard to our understanding of the role of angiogenesis in the ectopic implantation and survival of menstrual endometrial tissue will be discussed.

An evaluation of low molecular weight heparin and hyperbaric oxygen treatment in the prevention of intra-abdominal adhesions and wound healing

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Immunohistochemical detection of plasminogen activator inhibitor-1 in polycystic ovaries

Anovulation in women with polycystic ovary syndrome (PCOS) is incompletely understood. The concentration of the glycoprotein plasminogen activator inhibitor-1 (PAI-1) is raised in insulin resistance. This has been described in the granulosa and theca cell layers of the animal but not the human ovary. This study was performed to investigate the location of PAI-1 in the human ovary and investigate whether it may contribute to anovulation in PCOS. PAI-1 was localized immunohistochemically and quantitated using computer image analysis in 17 ovarian follicles from five women with a diagnosis of PCOS and compared with 15 follicles from six normal ovaries. PAI-1 was predominantly found in the granulosa and theca cells in both polycystic and normal ovaries. Image analysis did not reveal a difference in the PAI-1 signal from polycystic compared with normal ovaries. This study shows that PAI-1 plays a role in human ovulation, but its role in PCOS requires further research.

Mast cells are augmented in deep vein thrombosis and express a profibrinolytic phenotype

A number of recent data suggest that mast cells (MC) and their products are involved in the pathophysiology of thrombosis. In the current study, we have evaluated the number, distribution, and phenotype of MC in patients with deep vein thrombosis of the lower limb (DVT) (n = 15). Contralateral nonthrombosed limb veins served as control (CO). MC were examined by Giemsa staining and by immunohistochemistry using antibodies against tryptase, chymase, tissue-type plasminogen activator (tPA), urokinase (uPA), urokinase receptor (uPAR), and plasminogen activator inhibitors (PAI-1, PAI-2). We found an increase in the number of tryptase-positive MC in DVT compared with CO (DVT: 9.1+/-1.0 v CO: 4.7+/-0.6 MC/mm2, P < .05). Most of these MC appeared to accumulate in the adventitia of the thrombosed veins, in vicinity of the vasa vasorum. In both DVT and CO, MC reacted with monoclonal antibodies to c-kit, tryptase, and chymase. MC also stained positive for tPA and urokinase receptor, but did not express detectable PAI-1 or PAI-2. As compared with CO, a decreased proportion of MC in DVT was found to stain positive for chymase and tPA. Together, our results show that MC increase in number in DVT and express a profibrinolytic phenotype. We hypothesize that MC and MC-derived profibrinolytic molecules play a role in the pathophysiology of DVT.

An experimental study of the effect of aprotinin on intestinal adhesion formation

BACKGROUND

Depression of fibrinolysis is known to be a major mechanism for postoperative adhesion formation. Because aprotinin inhibits fibrinolysis it may lead to an increase in adhesion formation whereas its anti-inflammatory effects may lead to a decrease in adhesion formation. Our aim is to clarify conflicting results in previous literature.

METHODS

Basal levels of intestinal hydroxyproline (OHP) content and local fibrinolytic activity (LFA) were determined using naive groups. In the experiment groups, adhesions were created by scraping and creating a transient ischemia of a segment of terminal ileum. Group I and II rats were injected subcutaneous (s.c.) normal saline (NS) for 3 days and single dose intraperitoneal (i.p.) NS, respectively. Group III and IV rats were injected s.c. aprotinin for 3 days and single dose i.p. aprotinin, respectively. Group V rats were injected intramuscular methylprednisolone (MP) for 3 days. LFA and OHP levels were determined on the second and fifth postoperative days. The severity of adhesion formation was graded on the fifth day.

RESULTS

Aprotinin decreased both the severity of adhesions and OHP levels whereas MP decreased only the severity of adhesions. There was an early depression of LFA at the second day in both NS and MP groups increasing to basal levels at the fifth day. OHP levels showed significant correlation with adhesion severity.

CONCLUSION

Results showed that aprotinin decreased intra-abdominal adhesion formation probably by preventing early depression of LFA.

Plasminogen activators and inhibitors in peritoneal tissue

Serosal trauma elicits an inflammatory response which leads to the deposition of fibrin at injured sites, the residuals of which appear to be essential in excessive tissue repair and formation of intraabdominal adhesions. Local plasminogen activity may modulate this early phase of tissue repair. The present study was undertaken to investigate the distribution and cellular expression of plasminogen activators and their inhibitors in human peritoneal normal and inflamed tissue. Tissue-type plasminogen activator (t-PA) was expressed in subserosal capillary walls, and in normal mesothelium, but not in inflammation. Immunoreactivity for the plasminogen activator inhibitor type 1 (PAI-1) was present in normal mesothelium, and substantially increased in inflammation, where, in addition, immunoreactivity was found throughout the submesothelial tissue. This PAI-1 was partly co-localized with macrophages, as was the urokinase plasminogen activator (u-PA), suggesting an involvement of these cells in peritoneal tissue fibrinolysis. Inflammation or abrasion of the mesothelium during surgery is likely to cause a depletion of the local t-PA source and expose the potentially PAI-1-containing submesothelial tissue, thus promoting persistence of fibrin and formation of adhesions.

Macrophage-colony forming cells (M-CFC), with different sensitivities to colony stimulating factors, from peritoneal exudates and tissues of chronically inflamed mice

OBJECTIVE AND DESIGN

To determine whether nonadherent macrophage precursors are present within the inflamed peritoneal cavity in mice, we analysed the mononuclear cell populations from different peritoneal tissues.

OBJECTS

A group of 90 female mice BDF1 (C57BL/ 6 x DBA/2) was used for the study. Mononuclear cells were harvested from the peripheral blood, bone marrow, peritoneal exudate, omentum, mesentery, parietal peritoneum and diaphragm.

TREATMENT

Mice were injected intraperitoneally with 0.2 ml of Freund's incomplete adjuvant. Animals were sacrificed at 6, 13, 16, 21 and 30 days. Three to six animals were examined for each time period.

METHODS

Progenitor cell assay was performed in 1 ml of semi-solid agarose (0.3% Seakem GTG) DMEM which was supplied either with recombinant colony stimulating factors or with mesothelial cell-conditioned medium.

RESULTS

Nonadherent macrophage-colony forming cells were present in all peritoneal compartments (35-140 precursor cells/5 x 10(4) mononuclear cells). Granulocyte/ macrophage-colony forming cells were found in the inflamed omentum. Combined simultaneous treatment with GM-CSF and M-CSF blocked the proliferation of the exudate and mesentery-derived macrophage precursors, but not other peritoneal tissue-derived macrophage precursors. Sequential stimulation with GM-CSF and M-CSF did not inhibit macrophage colony formation.

CONCLUSIONS

GM-CSF can possibly influence the proliferative response induced by M-CSF. Nonadherent macrophage precursors recovered from different tissue compartments seem to differ in their sensitivity to growth regulation.

Plasminogen activator inhibitor-2 expression in inflamed appendix

Plasminogen activator inhibitors are thought to be responsible for the abolition of fibrinolytic activity in inflamed peritoneum. This reduction in the fibrin clearing capacity of the peritoneum promotes the formation of intra-abdominal adhesions. High concentrations of plasminogen activator inhibitor-2 (PAI-2) have been previously found in inflamed peritoneal tissue using immunoassays, but it is undetectable in normal peritoneum. The aim of this study was to localize plasminogen activator inhibitor-2 production in tissue by in situ mRNA hybridisation. Sections of normal and inflamed human appendix were hybridised with a digoxigenin labelled cDNA probe. In normal appendix staining was confined to macrophages in the mucosa. Macrophage staining was also seen in inflamed tissue but with a wider distribution throughout the appendix wall. PAI-2 was also localized to mesothelial cells of inflamed but not normal appendix. Cell identities were confirmed using immunohistochemistry directed against cell specific markers. Staining was absent from control slides incubated with plasmid DNA or PAI-2 probe following ribonuclease digestion. The identification of the cells expressing the PAI-2 gene in peritoneum increases our understanding of the pathophysiological process leading to fibrin deposition within the abdomen during peritonitis.

Human intraperitoneal fibrinolytic response to elective surgery

Intra-abdominal adhesions develop in over 90 per cent of patients undergoing laparotomy. Peritoneal fibrinolysis is believed to be important in the pathophysiology of adhesion formation. This study investigated the fibrinolytic response of postoperative peritoneal fluid in 12 patients undergoing elective laparotomy. There was a significant reduction in the plasminogen activating activity to undetectable levels at 24 h, which was sustained at 48 h (P < 0.05). While there was an early reduction in the concentration of tissue plasminogen activator (median 40.0, 28.2, 16.3 and 31.9 ng/ml at 2, 6, 24 and 48 h respectively; P < 0.05), the abolition of functional fibrinolytic activity appeared to be secondary to a marked increase in the concentration of plasminogen activator inhibitor (PAI) 1 (median 86, 196, 800 and 730 ng/ml at 2, 6, 24 and 48 h respectively; P < 0.05) and PAI-2 (median less than 6, 12, 155 and 245 ng/ml at 2, 6, 24 and 48 h respectively; P < 0.05). This reduction in the plasminogen activating activity of peritoneal fluid may favour the formation of permanent fibrous adhesions following surgery.

Tissue-type plasminogen activator and its inhibitor in rat aorta. Effect of endotoxin

Plasminogen activator (PA) and PA inhibitor (PAI) antigen, activity, and mRNA were analyzed in the three layers of rat aorta, and the effect of endotoxin on PA and PAI was studied. All PA activity in aorta was identified as tissue-type PA (TPA) activity; no urokinase-type PA was detected. In the tunica adventitia TPA activity, TPA antigen, and TPA mRNA were detected, whereas in the tunica media TPA antigen and TPA mRNA, but no TPA activity, were found. PAI activity was detected in the tunica media, explaining the absence of TPA activity in this layer. Removal of the endothelial cells had no effect on TPA antigen and PAI activity in intima-media preparations. Also, similar amounts of PAI-1 mRNA were found in intima-media preparations, irrespective of the presence or absence of the intima. Immunohistochemical staining showed that TPA immunoreactivity was present in all three layers of the aorta, whereas PAI-1 immunoreactivity was found in medial smooth muscle cells but not in endothelial cells. After endotoxin treatment, TPA activity was decreased in extracts of the total aorta and of the adventitia, although TPA antigen and TPA mRNA were unchanged. PAI-1 mRNA was strongly increased in the tunica adventitia and in the tunica media, as was PAI activity in the tunica media. Thus, endotoxin decreased TPA activity by increasing the synthesis of PAI-1; TPA was unaffected. Our observations in rat aorta differ from observations in mouse aorta and in rat carotid artery, and they caution against extrapolation from one tissue (or species) to another.

Fibrinolytic activity in the abdominal cavity of rats with faecal peritonitis

Generalized peritonitis causes a reduction in abdominal fibrinolytic activity, resulting in persistence of intraabdominal fibrin with subsequent adhesion and abscess formation. The activities of tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI) were measured in the peritoneal fluid of rats with faecal peritonitis and correlated with the extent of peritoneal damage to determine the cause of decreased fibrinolysis. Activity of tPA was low during the study period of 8 days, but higher in rats with peritonitis than in controls. The activity of PAI in rats with peritonitis was significantly increased compared with that of controls during the whole study period (P < 0.001). Histological signs of damage to the peritoneum were similar in rats with peritonitis and controls. There was no correlation between the extent of peritoneal damage and tPA or PAI activity. The increased activity of PAI in the peritoneal fluid of rats with faecal peritonitis may be the main cause of reduced fibrinolysis in the abdominal cavity. Activities of tPA and PAI may originate not only from the mesothelium but from other sources.

Tumour necrosis factor-mediated release of plasminogen activator inhibitor 1 by human peritoneal mesothelial cells

Human mesothelial cells synthesize plasminogen activator inhibitor (PAI) 1 in inflamed peritoneal tissue. The role of tumour necrosis factor (TNF) in the mediation of this response was studied. Postoperative peritoneal drain fluid contained both TNF and PAI-1. Peak levels of TNF at 4 h (median 271 pg/ml) preceded a rise in PAI-1 concentration, which peaked at 18 h (median 943.1 ng/ml). Thus TNF may mediate increased PAI-1 release in inflamed peritoneum. TNF significantly increased the mean(s.e.m.) release of PAI-1 by human peritoneal mesothelial cells in vitro at 4 h (control 1.84(0.17) ng/micrograms versus TNF 2.37(0.17) ng/micrograms, P < 0.05), 6 h (2.53(0.09) versus 3.88(0.46) ng/micrograms, P < 0.05), 18 h (0.50(0.02) versus 1.04(0.11) ng/micrograms, P < 0.05) and 24 h (0.87(0.05) versus 1.35(0.11) ng/micrograms, P < 0.05). TNF may be an important mediator of PAI-1 production by human mesothelial cells during peritoneal inflammation.