Similar collagen distribution in full-thickness skin grafts in intraperitoneal and onlay positions, an experimental mice-study.

PURPOSE: Autologous full-thickness skin grafting (FTSG) has the potential to become an option in abdominal wall repair. An understanding of tissue remodelling in the extracellular matrix (ECM) is crucial as this interplay determines such parameters as tissue strength and flexibility. This cross-sectional preclinical laboratory study in mice provides information on the distribution of collagen types and matrix metalloproteinases (MMPs) in the ECM of FTSGs in the intraperitoneal and onlay positions compared with internal controls. The aim was to evaluate morphologic changes after tissue remodelling and repair in FTSGs applied in the two positions and to detect any adverse host response. METHODS: ECM components were evaluated as follows: qualitative examination of collagen bundle thickness using Picrosirius Red staining (collagen types I, III and IV); and evaluation of collagen types IV and V, as well as MMPs 1, 8 and 9 using immunohistochemical staining. Full-thickness grafts transplanted between female twin mice were examined as this best mimics autologous transplantation. RESULTS: At 8 weeks, FTSGs in the intraperitoneal position did not show any noticeable differences in morphologic appearance to those in the onlay position. Both intraperitoneal and onlay FTSGs showed increases in the amount of thick collagen bundles compared to internal controls. No correlation was seen between distribution of MMPs 1, 8 or 9 and distribution of collagen types I, III, IV or V. CONCLUSION: This preclinical study shows that FTSGs in both intraperitoneal and onlay positions are possible application site options and, by extension, promising application site options for abdominal wall reinforcement in hernia surgery. Clinical studies in humans are required to confirm these findings.

Results at 3-year follow-up of totally extraperitoneal (TEP) hernia surgery with long-term resorbable mesh.

INTRODUCTION: Synthetic non-resorbable mesh is almost standard in hernia surgery. However, several studies have showed negative effects of permanent implants such as chronic inflammation and complications involving different organs bordering the mesh. Such complications can raise the risk of chronic post-operative pain (CPP). Recently promising results regarding CPP have been published in patients with Lateral Inguinal Hernia (LIH) using a slowly resorbable mesh in Lichtenstein technique. For this reason the aim of the present study was to find the effect of a slowly resorbable implant on the long-term rate of hernia recurrence and chronic post-operative pain in patients with LIH repaired with TEP procedure. METHODS: Prospective pilot study of TEP repair using TIGR® Matrix Surgical Mesh in 35 primary LIH. At 3-year follow-up the Visual Analogue Scale (VAS) and the Inguinal Pain Questionnaire were employed to assess pain. Recurrence was determined by ultrasound and clinical examination. RESULTS: All patients completed the pain questionnaires but one patient did not attend the planned clinical examination for the 3-year follow-up. No patients had CPP, as defined in the World Guidelines for Groin Hernia Management. Almost all patients had lower VAS score in any activity 3 years following surgery in comparison to the preoperative period. Three patients (8.8%) suffered symptomatic recurrence during the 3-year follow-up. CONCLUSION: TEP repair in patients with LIH using a synthetic long-term resorbable mesh was found to be encouraging respecting chronic post-operative pain at 3-year follow-up but at the cost of an increased risk of recurrence.

Inguinal hernia repair using a synthetic long-term resorbable mesh: results from a 3-year prospective safety and performance study.

PURPOSE: Conventional meshes for hernia repair and abdominal wall reinforcement are usually made from polypropylene, polyester or other synthetic plastic materials known to promote foreign body reactions and a state of chronic inflammation that may lead to long-term complications. A novel approach is to use long-term resorbable implants like TIGR(®) Matrix Surgical Mesh. Preclinical studies have shown that this mesh maintains mechanical integrity beyond the point in time where newly formed tissue is capable of carrying the abdominal loads. METHODS: This was a first-in-man, prospective, pilot study performed during 2009, at two sites in Sweden. Forty patients with primary inguinal hernias were enrolled for Lichtenstein repair using TIGR(®) Matrix Surgical Mesh. The primary endpoint was safety as assessed by monitoring the incidence of adverse events and serious adverse events (SAEs) both related and unrelated to the mesh. The secondary endpoint was pain or discomfort. Visual Analogue Scale (VAS) 0-10 and Inguinal Pain Questionnaire were used for scoring pain and discomfort. Included patients have been followed for 36 months using ultrasound in combination with clinical examination. RESULTS: All patients followed a normal early postoperative course. After 12 months no SAEs were reported. None of the patients with an isolated lateral inguinal hernia (LIH) had developed a recurrence but 4 (44 %) with medial and 4 (33 %) with combined hernias had recurred at 36-month follow-up. After 3-year follow-up none of the patients with LIH reported pain in the VAS-form and none of those patients could feel the sensation of a mesh in their groin. In the total study population 5 (16 %) patients experienced chronic pain in the form of mild sporadic pain and 3 (9.7 %) patients could feel the sensation of a mesh in their groin. CONCLUSION: The use of a synthetic long-term resorbable mesh (TIGR(®) Matrix Surgical Mesh) in Lichtenstein repair was found to be safe, without recurrences, and promising regarding pain/discomfort at 3-year follow-up in patients with LIH. However, patients with medial and combined inguinal hernias had high recurrence rates.

Effect of a DACC dressing on the growth properties and proliferation rate of cultured fibroblasts.

OBJECTIVE: To study the morphology and proliferation of cultured fibroblasts in combination with an experimental wound-healing model using cultured fibroblasts, with and without the presence of a hydrophobic, dialkyl carbamoyl chloride (DACC) dressing (Sorbact; Abigo Medical AB). METHOD: Human dermal fibroblasts were cultured and cell morphology and viability were investigated. Proliferation was investigated using an XTT assay. An experimental wound-healing model was employed, whereby mechanical damage was inflicted to the surface of cultured fibroblasts. The healing and closure of the wound was then monitored with and without the presence of the DACC dressing. RESULTS: Fibroblasts did not adhere easily to the dressing material. The presence of the DACC dressing increased the average proliferation rate of cultured fibroblasts by 50% compared with the untreated control medium (p<0.05). The DACC dressing significantly increased the healing rate by more than 100% after 72 hours (p<0.05) in the experimental model of wound healing, compared with the medium only. CONCLUSION: The enhanced wound healing observed in different types of wounds using the DACC dressing might be explained by an increase in cell growth and proliferation rate of cells in the wound area.

Local and systemic expressions of MMP-9, TIMP-1 and PAI-1 in patients undergoing surgery for clinically suspected appendicitis.

BACKGROUND/AIMS: To examine, compare and correlate the expressions of matrix metalloproteinase 9 (MMP-9), tissue inhibitor of metalloproteinase 1 (TIMP-1) and plasminogen activator inhibitor type 1 (PAI-1) in appendiceal tissue and pre- and postoperative blood samples in patients undergoing surgery for clinically suspected appendicitis. METHODS: Fifty-seven patients with complete tissue and blood samples were included and divided into groups of noninflamed appendix/lymphadenitis (n = 7), phlegmonous appendicitis (n = 30), gangrenous appendicitis (n = 11) and perforated appendicitis (n = 9). The protein expressions were assessed with ELISAs. The local expressions of MMP-9, TIMP-1 and PAI-1 were correlated with the systemic expressions at the time of surgery while the systemic individual differences between surgery and recovery were compared. RESULTS: There was a positive correlation between tissue and plasma PAI-1 (p < 0.05). The individual differences for plasma MMP-9 and PAI-1 were statistically nonsignificant, while they were higher for TIMP-1 in patients with perforated appendicitis compared with phlegmonous (p < 0.0001) and gangrenous appendicitis (p < 0.01). CONCLUSIONS: Plasma PAI-1 reflected the levels in appendiceal tissue at the time of surgery. Systemic TIMP-1 could have the potential of distinguishing perforated from nonperforated appendicitis.

Antifibrinolytic proCPU is present in the peritoneal cavity during surgery.

The fibrinolytic capacity of the peritoneum plays a pivotal role in peritoneal wound healing. During surgery the balance between fibrin deposition and degradation is tilted towards deposition, leading to the formation of adhesions. In blood, carboxypeptidase U (CPU) stabilizes clots by retarding fibrinolysis. The purpose of this study was to investigate whether the more stable zymogen, proCPU, is also present in the peritoneal cavity and, if so, to examine its origin. Levels of proCPU were measured in plasma and serosal peritoneal fluid collected during surgery. Peritoneal biopsies were stained for proCPU. Two-dimensional gel electrophoresis was performed to study the protein composition of the serosal fluid compared to plasma and Western blotting to identify differences in glycosylation of proCPU, indicating possible different cellular origin. Cultured human mesothelial cells were examined for proCPU production under normal conditions and conditions mimicking surgery. We found comparable and correlating levels of proCPU in serosal fluid and plasma. ProCPU was also found where fibrin covered the injured peritoneal surface. A protein composition very similar in serosal fluid and plasma was shown by two-dimensional gel electrophoresis, and the proCPU pattern did not indicate a different origin. No proCPU production was found in cultured mesothelial cells. This is the first study to report on the presence of proCPU in the peritoneal cavity, which seems to be the result of plasma oozing out during the inflammatory reaction to the surgical trauma. This is likely to be important for the balance between fibrin deposition and degradation and thereby in the formation of postoperative adhesions.

Peritoneal response to pneumoperitoneum and laparoscopic surgery.

BACKGROUND: It is generally believed that laparoscopic surgery inflicts less trauma to the peritoneum than open surgery. Local peritoneal fibrinolysis is a critical factor in adhesion development. The objective was to investigate fibrinolytic changes in the peritoneum during laparoscopic and open surgery. METHODS: At laparotomy (n = 10) peritoneal biopsies were taken at opening of the abdomen and just before closure. At laparoscopy (n = 12) opening peritoneal biopsies were taken after carbon dioxide insufflation, and closure biopsies just before exsufflation. Tissue concentrations of tissue-type plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI-1) and the resulting tPA activity were assayed. RESULTS: Concentrations of tPA in peritoneal tissue declined during operation in both groups, but significantly so only in the laparotomy group (- 53 per cent; P = 0.01). PAI-1 levels were higher in opening biopsies from the laparoscopy group (P = 0.004). There was an increase in PAI-1 concentration during laparotomy, but not during laparoscopy. At the end of the operation, there was no difference between the groups. The resulting tPA activity did not differ between groups at opening or closure. In both groups there was a significant decline during operation (laparotomy: - 59 per cent, P = 0.02; laparoscopy: - 63 per cent, P = 0.01). CONCLUSION: These findings indicate that the peritoneal response to open and laparoscopic surgery is similar. The initial rise in peritoneal PAI-1 concentration during laparoscopy suggests an adverse effect of carbon dioxide insufflation, which might affect peritoneal repair.

Overproduction of transforming growth factor-beta1 (TGF-beta1) is associated with adhesion formation and peritoneal fibrinolytic impairment.

BACKGROUND: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Response of visceral peritoneum to abdominal surgery.

BACKGROUND: Postoperative adhesion formation has been associated with a reduced capacity to degrade fibrin within the peritoneal cavity. Peritoneal fibrinolytic capacity has been shown to decrease during the course of a surgical operation. The aim of this study was to investigate whether tissue-type plasminogen activator (tPA), a key fibrinolytic enzyme, is released into the peritoneal cavity during operation. METHODS: Fluid released from the serosal surface of the small bowel was collected in a plastic bag from 16 patients undergoing surgery. Intraoperative blood samples were also taken from seven patients. Concentrations of the fibrinolytic components tPA and urokinase plasminogen activator (uPA), tPA activity and plasminogen activator inhibitor type 1 (PAI-1) concentration were measured by enzyme-linked immunoabsorbent assay. RESULTS: Intraoperative tPA concentrations were significantly raised in the peritoneal fluid collected compared with peripheral blood levels (P = 0.008). This resulted in a significantly higher tPA activity in the fluid compared with blood (P = 0.001). However, neither uPA (P = 0.29) nor PAI-1 (P = 0.84) concentrations differed significantly in fluid compared with blood. CONCLUSION: These data suggest that tPA is rapidly released by the visceral peritoneum during abdominal surgery. The different concentrations in peripheral blood and peritoneum suggest that tPA is released from the peritoneum by an active process, and does not solely derive from leakage of plasma.

The role of cytokines, coagulation, and fibrinolysis in peritoneal tissue repair.

Peritoneal tissue repair is a distinct entity. Regardless of the type of injury, a common series of events follows, culminating in inflammation and restoration. Molecular actors interact in a series of events in which the balance of fibrin deposition and degradation is vital. Although the complexity of the repair is illustrated by the multitude of effects and the overlap of molecular mediators involved, a framework is emerging. In this context, the overall role of cytokines is to shift the balance of fibrin deposition and degradation in favour of fibrin residues. Coagulation, as well as generating fibrin, is probably of importance in stimulating remesothelialisation, and fibrinolysis is instrumental in the degradation of fibrin deposits. As far as wound healing in concerned, we propose that the ultimate goal may not be to prevent adhesions, but rather to control their formation. To attain this, site-specific modulation of the repair process is essential. The new insights in mediators and modulators reviewed in this paper may provide means for site-specific modulation of peritoneal tissue repair as well as constituting molecular markers of the repair process.

Tissue markers as predictors of postoperative adhesions.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Characterization and fibrinolytic properties of mesothelial cells isolated from peritoneal lavage.

Human peritoneal mesothelial cells were harvested from patients undergoing open or laparoscopic surgery for non-septic conditions using three different approaches: (1) from a peritoneal biopsy, (2) from peritoneal fluid, and (3) from lavage fluid collected from peritoneal cavity. When these different methods were compared, cells derived from peritoneal fluid or lavage were more likely to result in established cultures than those obtained from biopsies. The cells displayed morphological, immunohistochemical and ultrastructural characteristics of mesothelial cells. The cultured mesothelial cells produced tissue type plasminogen activator (t-PA), urokinase plasminogen activator (uPA), and plasminogen activator inhibitor type-1 and type-2 (PAI-1 and PAI-2) during unstimulated conditions. Treatment with the proinflammatory mediators LPS and TNF-alpha resulted in an overall decreased fibrinolytic capacity with a decrease in the release of t-PA and an increase in plasminogen activator inhibitors PAI-1 and PAI-2. TNF-alpha had a more profound effect than LPS, especially on the release of t-PA. This may be an important mechanism by which inflammatory mediators disrupt the fibrin degradation. In conclusion, peritoneal lavage is a convenient and reproducible source of mesothelial cells for culture.

Cost of bowel obstruction resulting from adhesions.

OBJECTIVE: To assess the direct costs associated with bowel obstruction resulting from adhesions. DESIGN: Prospective study. SETTING: University Hospital, Sweden. SUBJECTS: 57 patients aged 16 years or older who fulfilled the clinical and radiological criteria of bowel obstruction. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Course of, and direct costs associated with, the illness. RESULTS: In 34 of the 57 patients (60%) bowel obstruction was caused by adhesions, and in all 34 the small bowel was obstructed (85% of all cases of small bowel obstruction). 22 of the 42 patients who required a hospital stay of more than 24 hours (52%) had adhesive obstruction, and 10 of these (45%) had to be operated on, 2 of them twice. Major complications occurred in 6 (60%) and one died. In a national perspective, adhesive bowel obstruction may cause 2330 hospital admissions annually, which is associated with an estimated direct cost of about US$13 million. CONCLUSIONS: Adhesions are a serious, common, and costly complication of surgery. Efforts have to be undertaken to control their formation.

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.

Vertical field MR imaging of upper thorax and spine in small children. Evaluation of a new surface coil.

To improve image quality in a vertical field MR imaging unit, operating at low field strength (0.3 T), we have designed a half-elliptical coil for use in the upper thoracic region of small children. Our intention was also to shorten the examination time, which until now has been long, because several scans with different coils have been necessary to cover the thoracic region. The experimental coil is designed so that a child's shoulders fit into the central region. The coil consists of 2 serially connected cable-loops, mounted on a foam rubber vest. The coil performance was tested in a phantom and improvements relative to standard coils were demonstrated in in vivo studies. The results indicate that by using the half-elliptical coil, the signal-to-noise (S/N) ratio can be improved by a factor of 2 to 3 in the thoracic region of a child.