Pelvic adhesions contain sex steroid receptors and produce angiogenesis growth factors

Genetic and Epidemiological Similarities, and Differences Between Postoperative Intraperitoneal Adhesion Development and Other Benign Fibro-proliferative Disorders

Intraperitoneal adhesions complicate over half of abdominal-pelvic surgeries with immediate, short, and long-term sequelae of major healthcare concern. The pathogenesis of adhesion development is similar to the pathogenesis of wound healing in all tissues, which if unchecked result in production of fibrotic conditions. Given the similarities, we explore the published literature to highlight the similarities in the pathogenesis of intra-abdominal adhesion development (IPAD) and other fibrotic diseases such as keloids, endometriosis, uterine fibroids, bronchopulmonary dysplasia, and pulmonary, intraperitoneal, and retroperitoneal fibrosis. Following a literature search using PubMed database for all relevant English language articles up to November 2020, we reviewed relevant articles addressing the genetic and epidemiological similarities and differences in the pathogenesis and pathobiology of fibrotic diseases. We found genetic and epidemiological similarities and differences between the pathobiology of postoperative IPAD and other diseases that involve altered fibroblast-derived cells. We also found several genes and single nucleotide polymorphisms that are up- or downregulated and whose products directly or indirectly increase the propensity for postoperative adhesion development and other fibrotic diseases. An understanding of the similarities in pathophysiology of adhesion development and other fibrotic diseases contributes to a greater understanding of IPAD and these disease processes. At a very fundamental level, blocking changes in the expression or function of genes necessary for the transformation of normal to altered fibroblasts may curtail adhesion formation and other fibrotic disease since this is a prerequisite for their development. Similarly, applying measures to induce apoptosis of altered fibroblast may do the same; however, apoptosis should be at a desired level to simultaneously ameliorate development of fibrotic diseases while allowing for normal healing. Scientists may use such information to develop pharmacologic interventions for those most at risk for developing these fibrotic conditions.

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.

Humidification during laparoscopic surgery: overview of the clinical benefits of using humidified gas during laparoscopic surgery

PURPOSE

The peritoneum is the serous membrane that covers the abdominal cavity and most of the intra-abdominal organs. It is a very delicate layer highly susceptible to damage and it is not designed to cope with variable conditions such as the dry and cold carbon dioxide (CO2) during laparoscopic surgery. The aim of this review was to evaluate the effects caused by insufflating dry and cold gas into the abdominal cavity after laparoscopic surgery.

METHODS

A literature search using the Pubmed was carried out. Articles identified focused on the key issues of laparoscopy, peritoneum, morphology, pneumoperitoneum, humidity, body temperature, pain, recovery time, post-operative adhesions and lens fogging.

RESULTS

Insufflating dry and cold CO2 into the abdomen causes peritoneal damage, post-operative pain, hypothermia and post-operative adhesions. Using humidified and warm gas prevents pain after surgery. With regard to hypothermia due to desiccation, it can be fully prevented using humidified and warm gas. Results relating to the patient recovery are still controversial.

CONCLUSIONS

The use of humidified and warm insufflation gas offers a significant clinical benefit to the patient, creating a more physiologic peritoneal environment and reducing the post-operative pain and hypothermia. In animal models, although humidified and warm gas reduces post-operative adhesions, humidified gas at 32 °C reduced them even more. It is clear that humidified gas should be used during laparoscopic surgery; however, a question remains unanswered: to achieve even greater clinical benefit to the patient, at what temperature should the humidified gas be when insufflated into the abdomen? More clinical trials should be performed to resolve this query.

What is the evidence for the use of low-pressure pneumoperitoneum? A systematic review

Background

Laparoscopic surgery has several advantages when compared to open surgery, including faster postoperative recovery and lower pain scores. However, for laparoscopy, a pneumoperitoneum is required to create workspace between the abdominal wall and intraabdominal organs. Increased intraabdominal pressure may also have negative implications on cardiovascular, pulmonary, and intraabdominal organ functionings. To overcome these negative consequences, several trials have been performed comparing low- versus standard-pressure pneumoperitoneum.

Methods

A systematic review of all randomized controlled clinical trials and observational studies comparing low- versus standard-pressure pneumoperitoneum.

Results and conclusions

Quality assessment showed that the overall quality of evidence was moderate to low. Postoperative pain scores were reduced by the use of low-pressure pneumoperitoneum. With appropriate perioperative measures, the use of low-pressure pneumoperitoneum does not seem to have clinical advantages as compared to standard pressure on cardiac and pulmonary function. Although there are indications that low-pressure pneumoperitoneum is associated with less liver and kidney injury when compared to standard-pressure pneumoperitoneum, this does not seem to have clinical implications for healthy individuals. The influence of low-pressure pneumoperitoneum on adhesion formation, anastomosis healing, tumor metastasis, intraocular and intracerebral pressure, and thromboembolic complications remains uncertain, as no human clinical trials have been performed. The influence of pressure on surgical conditions and safety has not been established to date. In conclusion, the most important benefit of low-pressure pneumoperitoneum is lower postoperative pain scores, supported by a moderate quality of evidence. However, the quality of surgical conditions and safety of the use of low-pressure pneumoperitoneum need to be established, as are the values and preferences of physicians and patients regarding the potential benefits and risks. Therefore, the recommendation to use low-pressure pneumoperitoneum during laparoscopy is weak, and more studies are required.

Celecoxib effectively inhibits the formation of joint adhesions

The present study investigated the effectiveness of celecoxib in preventing the formation of joint adhesions. Rabbit models of joint adhesion were created and the rabbits in two treatment groups were orally administered celecoxib or ibuprofen (as a positive control) for 30 days. Rabbits in the control group did not receive any treatment. Following the 30-day experimental period, the inhibitory effects of celecoxib and ibuprofen on the formation of joint adhesion were assessed using a number of methods, including the study of macroscopic appearance, histology and contracture angle. Thick fibrous adhesions developed in the knees of the rabbits in the control group. By contrast, few adhesions were observed in the two treatment groups, and those observed were soft, weak and easily stretched. Fewer adhesions were observed in the rabbits treated with celecoxib than in the rabbits in the other groups. The adhesion scores and contracture angles in the celecoxib (P<0.001) and ibuprofen (0.001<P<0.0025) groups were significantly lower than those of the control group. Moreover, the adhesion scores and contracture angles were significantly lower in the celecoxib group than in the ibuprofen group (0.025<P<0.05). Histologically, the adhesion tissues in the two treatment groups, particularly in the celecoxib group, were loose and thin with sparse fiber formation. The cell densities in the two treatment groups, of which the ibuprofen group had higher cell densities (0.025<P<0.05), were significantly lower than those in the control group (celecoxib group, P<0.001; ibuprofen group, 0.001<P<0.0025). These results indicated that celecoxib effectively inhibited the formation of joint adhesions and therefore may provide a novel and potent approach for their prevention.

The aromatase inhibitor letrozole reduces adhesion formation after intraperitoneal surgery in a rat uterine horn model

OBJECTIVE

To investigate, in an experimental animal study, the effects of letrozole and tamoxifen in the reduction of adhesion formation following abdominopelvic surgery.

STUDY DESIGN

Thirty female Wistar albino rats were included and divided into three groups. One group received 500 μg/d tamoxifen and a second group received 1 mg/kg/d letrozole through an enteric tube. A third group did not receive any drugs and served as the control group. On the fifth day, a laparotomy was performed and the right uterine horn was injured by monopolar cautery. The left uterine horn was incised with a scalpel and sutured. The preventive therapy protocols were continued for 7 days after surgery. On the 14th day after first surgery the animals were sacrificed, and the intraperitoneal macroscopic adhesion formation and microscopic adhesion features were evaluated. The Kruskal-Wallis test was used to compare the scores of the macroscopic adhesion scores and histologic features among the three groups, followed by a post hoc Mann-Whitney test. The total histological score was analyzed with a one-way ANOVA, followed by post hoc Bonferroni correction tests. p values ≤0.05 were considered statistically significant. The level of significance was set at p≤0.016 for the post hoc tests.

RESULTS

The letrozole and tamoxifen groups had significantly lower adhesion scores for the right uterine horn than the control group (p=0.005 and p=0.013, respectively). For the left horn, however, only the letrozole group had a lower macroscopic adhesion score than the controls (p=0.011). The total histological score was significantly lower in the letrozole group than in the control group (p=0.014), but no differences were found between the tamoxifen group and the control group (p=0.954). Inflammation, fibroblastic activity, collagen formation and vascular proliferation were significantly lower in the letrozole group compared with the control group (p<0.05). The foreign body reactions were similar among the three groups (p>0.05). Tamoxifen administration did not result in any significant effects on the histological scores (p>0.05).

CONCLUSION

Letrozole resulted in a significant decrease in postoperative macroscopic adhesion formation and the total histological scores, but tamoxifen did not demonstrate a similar effect on the histological scores.

Prevention of arthrofibrosis by monoclonal antibody against vascular endothelial growth factor: a novel use of bevacizumab in rabbits

BACKGROUND

Prevention of arthrofibrosis by different drugs and surgical techniques is an essential issue in modern orthopedics.

HYPOTHESIS

Intra-articular injection of bevacizumab can reduce arthrofibrosis on the rabbit's stifle joint model.

MATERIALS AND METHODS

Arthrofibrosis was induced in the right stifle joint of thirty male New Zealand white rabbits by removing the cortical bone of the medial femoral condyle under general anesthesia. The rabbits were randomly divided into three equal groups. The control group received intra-articular injection of saline; the one-injection group received a single dose of bevacizumab (2.5mg/kg), and the two-injection group received two intra-articular injections; the operation day and 14 days later. Forty-five days after surgery, animals were sacrificed. The severity of fibrosis was assessed based on the range of motion of the joint, a macroscopic adhesion score, and histopathologic variables such as the number of fibroblasts and of inflammatory cells, collagenous matrix deposition, synovial hyperplasia, granulation tissue formation, vascular proliferation, and presence of giant cells.

RESULTS

Although no statistically significant differences were found between the range of motion (P=0.222) and the macroscopic evaluation (P=0.067) of the control group and the one-injection group, all microscopic variables regarding the prevention of arthrofibrosis were significantly superior in the one-injection group except granulation tissue (P=0.347). Compared to the one-injection group, the two-injection group had better results not only in terms of macroscopic evaluation (P=0.001 for range of motion and 0.012 for visual adhesion score) but also in most of the histopathologic variables especially the number of fibroblasts (P=0.002), vascularity (P=0.028) and collagenous matrix deposition (P=0.039).

CONCLUSION

A single intra-articular injection of bevacizumab was effective for prevention of microscopically detected arthrofibrosis in the rabbit. Compared to single injection, two injections of bevacizumab improved the clinical outcome.

LEVEL OF EVIDENCE

Level II.

Prevention of peritoneal adhesions: a promising role for gene therapy

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.

Intra-abdominal adhesions: cellular mechanisms and strategies for prevention

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.

Sunitinib inhibits postoperative adhesions in a rabbit model

BACKGROUND

Postoperative abdominal adhesions are a major cause of morbidity and mortality. We previously demonstrated the inhibitory effect of sunitinib, a receptor tyrosine kinase inhibitor, on adhesion formation in a murine model, and now investigate its effects in a rabbit model.

METHODS

Forty New Zealand White rabbits underwent a standard adhesion procedure. Preoperatively, animals were randomized to treatment with sunitinib or saline (control). Animals were treated with a total of 11 daily doses, 1 preoperative and 10 postoperative. One group of 20 animals (group 1) was humanely killed on postoperative day 10, and the other (group 2) on postoperative day 30. After killing, adhesions were scored and abdominal wounds were collected for tensile strength and microvessel density measurements.

RESULTS

Sunitinib-treated animals in group 1 had a mean tenacity score of 1.67 ± 0.29 compared with 3.60 ± 0.16 in control animals (P < .01). Similarly, the mean tenacity scores for sunitinib-treated and control animals in group 2 were 0.20 ± 0.20 and 2.70 ± 0.37, respectively (P < .01). The mean uterine involvement scores for sunitinib-treated and control animals in group 1 were 1.44 ± 0.29 and 3.70 ± 0.15, respectively (P < .01), and in group 2 were 0.10 ± 0.10 and 2.70 ± 0.45, respectively (P < .01). There were no differences in ultimate or modular wound tensile strength between sunitinib-treated and control animals.

CONCLUSION

Sunitinib significantly reduces postoperative adhesions in a rabbit model. This therapy may improve postoperative adhesion-related morbidity and mortality.

GnRH receptor and peritoneal plasmin activity

Most surgical procedures performed by obstetrician-gynecologists are associated with pelvic adhesions that cause subsequent serious sequelae, including small bowel obstruction, infertility, chronic pelvic pain, and difficulty in postoperative treatment, including complexity during subsequent surgical procedures. This study was conducted to determine if gonadotropin-releasing hormone analogues (GnRHa) affect the expressing tissue-type plasminogen activator (t-PA) and its inhibitor-1 (PAI-1) in peritoneal cells in culture. Human peritoneal Met5A cells were used to examine the effects of GnRHa leuprolide, buserelin and goserelin on the levels of t-PA and PA-1. Antigen concentrations were measured in conditioned media and cell lysates by real-time PCR and ELISA. GnRH receptor (GnRHR) mRNA was determined by RT-PCR. GnRHR mRNA was detected in Met5A cells. Exposure of Met5A cells to GnRHa induced a rapid decrease of PAI-1 level in cultured medium but not in cell lysate (protein and mRNA). These effects of GnRHa on PAI-1 were not associated with any changes in t-PA level. These results suggest that GnRHa may be an effective stimulator of local peritoneal fibrinolytic activity, as it decreases PAI-1 secretion in peritoneal Met5A cells by a mechanism linked to GnRHR.

Nerve fibres in ovarian endometriotic lesions in women with ovarian endometriosis

BACKGROUND

Although nerve fibres are present in eutopic and ectopic endometrium, it is unclear whether they appear in ovarian endometriotic lesions. We investigated the presence of nerve fibres in ovarian endometriotic lesions and its correlation with clinical parameters in women with ovarian endometriosis.

METHODS

Histological sections of ovarian endometriotic lesions from 61 women with ovarian endometriosis (Stages II-IV) who underwent laparoscopic endometrioma cystectomy were stained immunohistochemically using a specific polyclonal rabbit anti-protein gene product 9.5 (PGP9.5) antibody to demonstrate myelinated and unmyelinated nerve fibres.

RESULTS

Nerve fibres stained with PGP9.5 were detected in ovarian endometriotic lesions in 31.1% of women, and most appeared in fibrotic interstitium of ovarian endometriotic lesions. The density of PGP9.5-immunoactive fibres in ovarian endometriotic lesions in women with pain symptoms (n = 35) was higher than in women with no pain symptoms (n = 26, P = 0.039), although the percentage (positive cases/total) of PGP9.5-positive fibres did not differ. In women with pain symptoms, PGP9.5-positive fibres appeared in 40.0% of cases and the density of PGP9.5-immunoactive fibres in ovarian endometriotic lesions was correlated with severity of pain symptoms (r = 0.466, P = 0.005). In women with no pain, PGP9.5-positive fibres were detected in only 5 (19.2%) women. Both the percentage and the density of PGP9.5-positive fibres in ovarian endometriotic lesions were associated with pelvic adhesions (chi2 = 6.833, P = 0.009; Z = 2.442, P = 0.015, respectively) but not with disease severity.

CONCLUSIONS

PGP9.5-immunoactive nerve fibres in ovarian endometriotic lesions may be involved in the pathophysiology of pain generation and pelvic adhesion formation in women with ovarian endometriosis.

Cytokine orchestration in post-operative peritoneal adhesion formation

Peritoneal adhesions are a near inevitable occurrence after laparotomy and a major cause of both patient and physician misery. To date, clinical attempts at their amelioration have concentrated on manipulating the physical factors that affect their development despite a wealth of experimental data elucidating the molecular mechanisms that underlie their initiation, development and maturation. However, the advent of targeted, specific anti-cytokine agents as directed therapy for inflammatory and neoplastic conditions raises the prospect of a new era for anti-adhesion strategies. To harness this potential will require considerable cross-disciplinary collaboration and that surgeon-scientists propel themselves to the forefront of this emerging field.

The effect of estradiol on the expression of estrogen, progesterone, androgen, and prolactin receptors in human peritoneal fibroblasts

PURPOSE

To assess the ability of fibroblasts isolated from normal peritoneum and adhesion tissues to express various hormone receptors when cultured with exogenous estradiol.

METHODS

Primary cultures of fibroblasts from normal human peritoneum and adhesion tissue were treated with zero (control), 10(-10), 10(-8), and 10(-6) M concentrations of 17beta-estradiol. We performed real time reverse transcriptase polymerase chain reaction to determine mRNA levels of estradiol-alpha receptor (ER-alpha) and estradiol-beta receptor (ER-beta), progesterone receptor (P-R), androgen receptor (A-R), and prolactin receptor (PRL-R) in the two types of fibroblast cultures.

RESULTS

In the control groups, P-R and A-R were higher in normal than in adhesion fibroblasts. In adhesion cells, ER-alpha were higher at 10(-8) estradiol; ER-beta were higher at 10(-6) M estradiol; P-R remained constant; A-R showed a higher expression at 10(-10) and 10(-8) M estradiol; and PRL-R showed an exponential increase at 10(-10) M estradiol.

CONCLUSIONS

The inflammatory-like changes manifested by adhesion fibroblasts enhance the anabolic hormones receptor expression (ER-alpha, ER-beta, PRL, and A-R), when exposed to estradiol.

Gonadotropin-releasing hormone agonist pretreatment did not decrease postoperative adhesion formation after abdominal myomectomy in a randomized control trial

OBJECTIVE

To determine if 3 months of preoperative gonadotropin-releasing hormone agonist (GnRH-a) treatment decreases postoperative uterine adhesions after open abdominal surgery for the removal of uterine fibroids.

DESIGN

Prospective, randomized, clinical study.

SETTING

A tertiary care medical center.

PATIENT(S)

Women of reproductive age with symptomatic uterine fibroids not amenable to hysteroscopic removal.

INTERVENTION(S)

Twenty patients underwent an initial abdominal myomectomy followed by a second-look laparoscopy for evaluating uterine adhesions after random allocation to groups receiving either GnRH analog or placebo for 3 months before the initial surgery.

MAIN OUTCOME MEASURE(S)

Adhesion formation between treatment groups and by incision number and aggregate length.

RESULT(S)

Presurgical GnRH-a treatment did not decrease adhesion formation compared with placebo. For every additional centimeter of incision length, the total adhesion area over the uterine serosal surface increased by 0.55 cm(2). The number of myomas removed and the number of incisions were positively correlated with total adhesion area.

CONCLUSION(S)

Preoperative treatment with GnRH-a for 3 months before open abdominal myomectomy did not decrease postoperative uterine adhesions. Following the standards of good surgical technique, adhesions are minimized with fewer and smaller incisions.

Evaluation of postoperative peritoneal adhesion formation following perioperative nicotine administration

PURPOSE

The primary step in postoperative peritoneal adhesion formation involves the exudation of fibrin through permeable mesenteric capillaries. Nicotine, the most potent constituent of cigarette smoke, augments the release of vascular endothelial growth factor (VEGF), which increases vascular permeability. The objective of this study was to evaluate the effect of nicotine on postlaparotomy abdominal adhesions.

METHODS

CD-1 mice were randomized to receive, ad libitum, either water alone (as 2% sucrose solution) or water mixed with 100 microg/mL nicotine (to obtain blood levels equivalent to a 1 pack/day smoker) (n = 32 mice per group). After 1 wk, all mice underwent laparotomy to induce adhesion formation using the same experimental method (consisting of laparotomy with cecal abrasion to achieve serosal punctuate hemorrhage). Fourteen days later, all animals were sacrificed for adhesion grading (0 to 3) by a blinded observer. Additionally, peritoneal lavage fluid from separate mice receiving either water or nicotine water before their surgery or else undergoing sham laparotomy was retrieved at 2, 6, and 24 h postoperatively (4 mice per group/time point) and assessed for VEGF concentrations.

RESULTS

The nicotine treated group had a mean +/- SEM adhesion score of 2.4 +/- 0.2, which was significantly greater than that of the control group (1.2 +/- 0.2) (P < 0.05, Mann Whitney U test.). This correlated with a significant increase in peritoneal VEGF levels occurring at 6 and 24 h in the nicotine group.

CONCLUSION

Peritoneal adhesion formation after surgery is increased in mice receiving nicotine perioperatively. This effect may be mediated through a direct augmentation of peritoneal VEGF release by nicotine with a subsequent increase in mesenteric endothelial permeability. These findings could have significant implications for smokers undergoing intra-abdominal surgical procedures.

Impact of aromatase inhibitors on adhesion formation in a rat model

OBJECTIVE

To investigate the antiadhesion potential of tamoxifen and anastrozole in a rat uterine horn model.

DESIGN

Experimental animal study.

SETTING

University animal laboratory.

ANIMAL(S)

Forty-five female Wistar albino rats.

INTERVENTION(S)

We examined the effects of tamoxifen and anastrozole to reduce the extent and severity of postoperative adhesions in a rat uterine horn model: the control group received no therapy while the second and third groups received 500 mug/day tamoxifen and 0.2 mg/kg/day anastrazole, respectively, through an enteric tube, starting 5 days before surgery. These protocols were continued for 14 days after the surgery until the rats were killed.

MAIN OUTCOME MEASURE(S)

Adhesions were scored according to their extent and severity, and specimens were also evaluated and scored histologically according to the following features: inflammation, fibroblastic activities, foreign body reaction, collagen formation, and vascular proliferation.

RESULT(S)

Anastrozole had the lowest mean adhesion scores, and these scores were significantly different from those of the controls. However, there were no statistically significant differences between control and tamoxifen groups and between tamoxifen and anastrozole groups. Histologic scores were lowest in the anastrozole group, which were statistically different from those of the tamoxifen and anastrozole groups, whereas scores of the control group were not statistically different from those of the tamoxifen group.

CONCLUSION(S)

Anastrazole decreased postsurgical adhesion scores by both visual scores and histologic analyses in a rat model. Further experimental and clinical trials are required to confirm these results.

Human peritoneal adhesions show evidence of tissue remodeling and markers of angiogenesis

PURPOSE

This study was designed to investigate the vascular structure and angiogenic activity of human peritoneal adhesions.

METHODS

Adhesions were collected from patients undergoing laparotomy (n=32). Histologic features were documented and the distribution of mature and immature vascular markers were determined by immunolocalization and quantified by image analysis. The three-dimensional organization of blood vessels was investigated by confocal microscopy. Expression of vascular endothelial growth factor A, its receptor flk-1, and proliferating cell nuclear antigen were assessed by immunohistochemistry as indicators of angiogenic activity.

RESULTS

Adhesions were found to be vascularized structures comprising bundles of collagen, interspersed with varying amounts of adipose tissue. Functional blood vessels expressed recognized vascular markers (vWF, CD34, alpha-SMA, and CD105) and formed a branching network similar to that of the peritoneum. Those adhesions expressing vascular endothelial growth factor A and its receptor showed significantly higher numbers of immature vessels as defined by expression of CD105. Omental adhesions (n=16) contained significantly more adipose tissue (P<0.05) and displayed a higher microvessel density (P<0.01) but lower cellularity (P<0.05) compared with nonomental adhesions (n=16).

CONCLUSIONS

All adhesions contained functional blood vessels and most showed evidence of cell proliferation. The presence of vascular endothelial growth factor A and its receptor in human adhesions suggests ongoing angiogenic activity. This study demonstrates that adhesions are vascular structures with evidence of tissue remodeling and suggests potential for new prevention strategies involving antiangiogenic therapies.

Mast cells facilitate local VEGF release as an early event in the pathogenesis of postoperative peritoneal adhesions

BACKGROUND

Peritoneal injury sustained at laparotomy may evoke local inflammatory responses that result in adhesion formation. Peritoneal mast cells are likely to initiate this process, whereas vascular permeability/endothelial growth factor (VEGF) may facilitate the degree to which subsequent adhesion formation occurs.

METHODS

Mast cell deficient mice (WBB6F1-/-), along with their mast cell sufficient counterparts (WBB6F1+/+), underwent a standardized adhesion-inducing operation (AIS) with subsequent sacrifice and adhesion assessment 14 days later in a blinded fashion. Additional CD-1 and WBB6F1+/+, and WBB6F1-/- mice were killed 2, 6, 12, and 24 hours after operation for measurement of VEGF by ELISA in systemic serum and peritoneal lavage fluid. Two further groups of CD-1 mice underwent AIS and received either a single perioperative dose of anti-VEGF monoclonal antibody (10 mug/mouse) or a similar volume of IgG isotypic antibody and adhesion formation 2 weeks later was evaluated.

RESULTS

WBB6F1-/- mice had less adhesions then did their WBB6F1+/+ counterparts (median [interquartile range] adhesion score 3[3-3] vs 1.5[1-2] respectively; P < .003). Local VEGF release peaked 6 hours after AIS in both WBB6F1+/+ and CD-1 mice whereas levels remained at baseline in WBB6F1-/- mice. CD-1 mice treated with a single dose of anti-VEGF therapy during operation had less adhesions than controls (2[1.25-2] vs 3[2.25-3], P = .0002).

CONCLUSIONS

Mast cells and VEGF are central to the formation of postoperative intra-abdominal adhesions with mast cells being responsible, either directly or indirectly, for VEGF release into the peritoneal cavity after operation. In tandem with the recent clinical success of anti-VEGF monoclonal antibodies in oncologic practice, our observations suggest an intriguing avenue for research and development of anti-adhesion strategy.

Coincidence of connective tissue growth factor expression with fibrosis and angiogenesis in postoperative peritoneal adhesion formation

PURPOSE

To investigate the relationship between connective tissue growth factor (CTGF) and fibrosis and angiogenesis in postoperative peritoneal adhesion formation.

METHODS

Adhesions were performed in 35 rats by creation of a peritoneal patch. Animals were sacrificed at 7 different time-points over 3 weeks. Adhesions and uninjured peritoneum from all animals were assessed by Northern blotting for CTGF and collagen-I mRNA and by immunohistochemistry for CTGF localization, degree of fibrosis and angiogenesis.

RESULTS

Persistent adhesions formed in all animals. CTGF and collagen-I mRNA were increased in adhesions compared to uninjured peritoneum (p < 0.05 for both). The temporal expression pattern depicted delayed peak levels of collagen-I mRNA with increasing tendency for both transcripts at the end of the observation period. Fibrosis within adhesions correlated positively with time after surgery (r = 0.85; p < 0.001) and showed typical signs of chronic tissue fibrosis at later time points. Angiogenesis was detected in adhesions but not in uninjured peritoneum (p = 0.001) and coincided with the spatial and temporal expression of CTGF protein in fibroblasts and vascular endothelial cells.

CONCLUSIONS

The co-expression of CTGF with increasing fibrosis and angiogenesis in postoperative peritoneal adhesions suggests a role for CTGF as critical molecule in fibrous adhesive disease and target for future adhesion prevention.

Prevention of intra-abdominal adhesions using the antiangiogenic COX-2 inhibitor celecoxib

OBJECTIVE

To determine the effects of COX-2 specific inhibitors on postoperative adhesion formation.

SUMMARY AND BACKGROUND DATA

Intra-abdominal adhesions are the major cause of intestinal obstruction and secondary infertility after surgical procedures. Because adhesion synthesis requires angiogenesis, and cyclooxygenase-2 enzyme (COX-2) inhibitors have antiendothelial activity, we tested COX-2 inhibitors in a murine model of intra-abdominal adhesion formation.

METHODS

A silicone patch was secured to the lateral abdominal wall of groups of C57BL/6 mice, followed by cecal abrasion to promote adhesion formation. Beginning on the day of surgery, mice were treated with the selective COX-2 agents, celecoxib or rofecoxib, and the nonspecific COX inhibitors, aspirin, naproxen, ibuprofen, or indomethacin. Animals were treated for 10 days and killed. A second group (celecoxib, rofecoxib, aspirin) was treated for 10 days and observed for an additional 25 days. After treatment, intra-abdominal adhesions were scored using a standard method. The patch was subjected to immunohistochemistry with the endothelial-specific marker, CD31.

RESULTS

Animals treated with selective and nonselective COX-2 inhibitors, except aspirin, had significantly fewer adhesions than control animals. Celecoxib produced a maximal reduction in adhesion formation compared with rofecoxib and the nonselective COX-2 inhibitors at 10 days. After 25 days, celecoxib and rofecoxib, but not aspirin, had fewer adhesions than control mice. Adhesions from mice treated with celecoxib had reduced microvessel density compared with rofecoxib, the nonselective COX inhibitors, and control animals.

CONCLUSIONS

Selective COX-2 inhibitors, in particular celecoxib, provide durable inhibition of intra-abdominal adhesions through an antiangiogenic mechanism.

Modulation of the expression of vascular endothelial growth factor in human fibroblasts

OBJECTIVE

To examine the up-regulation of vascular endothelial growth factor (VEGF) expression by hypoxia, a crucial event leading to neovascularization, as the reduction in VEGF expression may facilitate minimization of adhesion development.

DESIGN

Prospective experimental study.

SETTING

University medical center.

PATIENT(S)

Five patients with adhesions undergoing laparotomy with excision of adhesions and normal peritoneum.

INTERVENTION(S)

Adhesion and normal peritoneal fibroblasts were treated with dichloroacetic acid (DCA) or NS-398 (a cyclooxygenase-2 [COX-2] inhibitor) for 24 to 48 hours.

MAIN OUTCOME MEASURE(S)

A real-time reverse transcriptase polymerase chain reaction (RT-PCR) to quantify relative changes in mRNA levels of VEGF from each treatment.

RESULT(S)

In both normal peritoneal and adhesion fibroblasts, VEGF mRNA was present with statistically significantly higher levels in adhesion fibroblasts (32%). The DCA treatment resulted in a statistically significant decrease in VEGF mRNA levels in adhesion (20%) and normal peritoneal (18%) fibroblasts. The NS-398 treatment resulted in a statistically significant decrease in VEGF mRNA levels in adhesion (25%) and normal peritoneal (16%) fibroblasts.

CONCLUSION(S)

Stimulation of aerobic metabolism by DCA or inhibition of COX-2 by NS-398 reduces VEGF expression. Angiogenesis, which is an integral component in the development of dense vascular adhesions, may be reduced by either COX-2 inhibitors or stimulation of aerobic metabolism by DCA.

Expression pattern and regulation of genes differ between fibroblasts of adhesion and normal human peritoneum

BACKGROUND

Injury to the peritoneum during surgery is followed by a healing process that frequently results in the attachment of adjacent organs by a fibrous mass, referred commonly as adhesions. Because injuries to the peritoneum during surgery are inevitable, it is imperative that we understand the mechanisms of adhesion formation to prevent its occurrence. This requires thorough understanding of the molecular sequence that results in the attachment of injured peritoneum and the development of fibrous tissue. Recent data show that fibroblasts from the injured peritoneum may play a critical role in the formation of adhesion tissues. Therefore, identifying changes in gene expression pattern in the peritoneal fibroblasts during the process may provide clues to the mechanisms by which adhesion develop.

METHODS

In this study, we compared expression patterns of larger number of genes in the fibroblasts isolated from adhesion and normal human peritoneum using gene filters. Contributions of TGF-beta1 and hypoxia in the altered expression of specific genes were also examined using a semiquantitative RT-PCR technique.

RESULTS

Results show that several genes are differentially expressed between fibroblasts of normal and adhesion peritoneum and that the peritoneal fibroblast may acquire a different phenotype during adhesion formation. Genes that are differentially expressed between normal and adhesion fibroblasts encode molecules involved in cell adhesion, proliferation, differentiation, migration and factors regulating cytokines, transcription, translation and protein/vesicle trafficking.

CONCLUSIONS

Our data substantiate that adhesion formation is a multigenic phenomenon and not all changes in gene expression pattern between normal and adhesion fibroblasts are the function of TGF-beta1 and hypoxia that are known to influence adhesion formation. Analysis of the gene expression data in the perspective of known functions of genes connote to additional targets that may be manipulated to inhibit adhesion development.

Role of vascular endothelial growth factor receptor 1 in basal adhesion formation and in carbon dioxide pneumoperitoneum-enhanced adhesion formation after laparoscopic surgery in mice

OBJECTIVE

To evaluate the role of vascular endothelial growth factor receptor-1 (VEGFR-1) in adhesion formation after laparoscopic surgery.

DESIGN

Prospective, randomized study.

SETTING

Academic research center.

ANIMAL(S)

Forty female Swiss mice.

INTERVENTION(S)

Adhesions were induced by standardized lesions during laparoscopy. The CO2 pneumoperitoneum was maintained for the minimum time needed to perform the lesions (10 minutes) or for a longer period (60 minutes) to evaluate basal adhesions and pneumoperitoneum-enhanced adhesions, respectively. Mice were treated either with IgG or with antibodies against VEGFR-1.

MAIN OUTCOME MEASUREMENT(S)

Adhesions were quantitatively and qualitatively scored after 7 days during laparotomy.

RESULT(S)

In IgG-treated mice, 60 minutes of CO2 pneumoperitoneum increased basal adhesions. In VEGFR-1 antibody-treated mice, basal adhesions were similar to the control group and 60 minutes of CO2 pneumoperitoneum did not increase adhesions. Therefore, in these mice, pneumoperitoneum-enhanced adhesions were lower than in IgG-treated mice.

CONCLUSION(S)

The data confirm that CO2 pneumoperitoneum is a cofactor in adhesion formation and demonstrate that VEGFR-1 plays a role in pneumoperitoneum-enhanced adhesions, which is consistent with a role of placental growth factor, VEGF-A, and VEGF-B in pneumoperitoneum-enhanced adhesions. These observations give new insight into the pathogenesis of adhesion formation.

Gonadotropin-releasing hormone agonists for prevention of postoperative adhesions: an overview

Adhesion formation is of major concern to the pelvic surgeon. Most patients develop postoperative adhesions regardless of whether the mode of access to the abdominal cavity is by laparoscopy or laparotomy. Infertility is related to adhesions in the pelvis in 15-20% of cases. Peritoneal adhesions are the main cause of mechanical bowel obstruction in 65-80% of cases and contribute to a large extent to health-care expenditures. To prevent the formation of postoperative adhesions, a variety of medications have been studied such as glucocorticoids, heparin, dextran 70, saline solution, antibiotics, promethazine, antihistamines, prostaglandin synthesis inhibitors, Ringer's lactate solution, calcium-channel blockers and barriers such as Interseed and Gore-Tex. Such adhesions can be induced when operating on myomas and endometriosis. Experimental and clinical studies have demonstrated various mechanisms of action to be involved in adhesion prevention when gonadotropin-releasing hormone agonists (GnRH-a) are used for treatment. The following have been demonstrated and suggested: (1) Hypoestrogenic condition was found in rats to be associated with decreased adhesion formation. This could be related to the influence on estrogen-dependent growth factors and growth modulators by reliable and constant inhibition of ovarian estradiol biosynthesis and secretion, but also non-competitive estrogen antagonism seems to play a role. (2) Treatment with GnRH-a reduces the growth hormone release stimulated by growth hormone-releasing hormone. (3) GnRH-a treatment influences neoangiogenesis by affecting vascular endothelial growth factor and basic fibroblastic growth factor. (4) GnRH-a reduce the basal rate of coagulatory processes. The frequency and extent of fibrin-generating and degrading processes are reduced. Activity of the plasminogen activating inhibitor is reduced, suggesting an improvement infibrinolytic reactivity. (5) GnRH-a use alters the vascular resistance index, pulsatility index and vascular peak velocity, and possible immune response. (6) Avoidance of bleeding can reduce fibrin and therefore decreases the matrix for invasion by fibroblasts. (7) GnRH-a reduce the degree of inflammation postoperatively. Adhesion prevention seems to be at its best when pre- and postoperative GnRH-a treatment is administered. At present, there are trends to operate without prior treatment with GnRH-a. Based upon the data available, it seems worthwhile to consider preoperative and also postoperative treatment with GnRH-a: pretreatment for at least 2-3 months seems to be indicated, and a similar time after operation, to block the events associated with adhesion formation.

Role of CO2 pneumoperitoneum-induced acidosis in CO2 pneumoperitoneum-enhanced adhesion formation in mice

The effect of assisted ventilation and CO(2) pneumoperitoneum during laparoscopic surgery upon blood gases and adhesion formation were evaluated in mice. We confirmed that the CO(2) pneumoperitoneum induces acidosis and enhances adhesion formation, and an association between both effects was demonstrated, together with its modulation by the assisted ventilation.

Role of vascular endothelial growth factor and placental growth factor in basal adhesion formation and in carbon dioxide pneumoperitoneum-enhanced adhesion formation after laparoscopic surgery in transgenic mice

OBJECTIVE

To evaluate the role of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) in adhesion formation after laparoscopic surgery.

DESIGN

Prospective, randomized study.

SETTING

Academic research center.

ANIMAL(S)

Female wild-type mice and transgenic mice (n = 110), expressing exclusively VEGF-A(164) (VEGF-A(164/164)) or deficient for VEGF-B (VEGF-B(-/-)) or for PlGF (PlGF(-/-)).

INTERVENTION(S)

Adhesions were induced during laparoscopy. To evaluate "basal adhesions" and "CO(2) pneumoperitoneum-enhanced adhesions," the pneumoperitoneum was maintained for a minimum (10 minutes) or prolonged (60 minutes) period. The role of PlGF was also evaluated by administration of antibodies.

MAIN OUTCOME MEASURE(S)

Adhesions were blindly scored after 7 days.

RESULT(S)

In all wild-type mice, CO(2) pneumoperitoneum enhanced adhesion formation. In comparison with wild-type mice, basal adhesions were higher in VEGF-A(164/164) mice and similar in VEGF-B(-/-) and PlGF(-/-) mice. Pneumoperitoneum did not enhance adhesions in any of these transgenic mice. The effects observed in PlGF(-/-) mice were confirmed in PlGF antibody-treated mice.

CONCLUSION(S)

The data demonstrate that the VEGF family plays a role in adhesion formation and confirm that CO(2) pneumoperitoneum enhances adhesions. VEGF-A(164) has a direct role in basal adhesions. Absence of pneumoperitoneum-enhanced adhesions in VEGF-A(164/164), VEGF-B(-/-), and PlGF(-/-) mice indicates up-regulation of VEGF-A(164), VEGF-B, and PlGF by CO(2) pneumoperitoneum as a mechanism for pneumoperitoneum-enhanced adhesion formation.

Thalidomide given intraperitoneally reduces the number of postoperative adhesions after large bowel resection in rabbits

OBJECTIVE

To investigate the effect of thalidomide given intraperitoneally on the formation of adhesions after colonic resection in rabbits.

DESIGN

Controlled, randomised prospective study.

SETTING

University hospital, Germany.

ANIMALS

40 female New Zealand White rabbits.

INTERVENTIONS

After an end-to-end colonic anastomosis the animals were given thalidomide 200 mg/kg in 1% carboxymethylcellulose intraperitoneally or carboxymethylcellulose alone (n = 20 in each group).

OUTCOME MEASURES

The adhesion score according to Tyrell on day 3 (n = 20) and day 7 (n = 20) postoperatively, weight, behaviour, and white cell count (WCC).

RESULTS

There was no difference in behaviour or weight. On the third postoperative day WCCs and on the seventh postoperative day WCCs and adhesion scores, were lower in the thalidomide group (p < 0.01).

CONCLUSION

The number of postoperative adhesions was reduced in the group given thalidomide intraperitoneally. Our results suggest that thalidomide may be helpful in the prevention of postoperative adhesions.

Peritoneal mesothelial hypoxia during pneumoperitoneum is a cofactor in adhesion formation in a laparoscopic mouse model

OBJECTIVE

To develop a laparoscopic mouse model to evaluate the hypothesis that mesothelial hypoxia during pneumoperitoneum is a cofactor in adhesion formation.

DESIGN

Prospective randomized trials.

SETTING

Academic research center.

ANIMAL(S)

One hundred thirty female Naval Medical Research Institute (NMRI) mice.

INTERVENTION(S)

Adhesions were induced by opposing monopolar lesions in uterine horns and pelvic side walls during laparoscopy and evaluated after 7 or 28 days under microscopic vision during laparotomy. The following pneumoperitoneum variables were assessed: duration (10 or 60 minutes), insufflation pressure (5 or 15 cm of water), insufflation gas (CO(2) or helium), and addition of oxygen (0-12%).

MAIN OUTCOME MEASURE(S)

Adhesions were scored quantitatively and qualitatively for extent, type, and tenacity.

RESULT(S)

Scoring of adhesions 7 or 28 days after laparoscopic surgery was comparable. Adhesions increased with duration of pneumoperitoneum and with insufflation pressure and decreased with the addition of oxygen. Half-maximal reduction of adhesions was obtained at 1.5% oxygen, whereas a maximal reduction required only 2%-3%. The effect of CO(2) and helium was similar.

CONCLUSION(S)

These data demonstrate the feasibility of the intubated laparoscopic mouse model and confirm previous observations in rabbits, indicating that mesothelial hypoxia plays a key role in adhesion formation.

Neutralization of fibroblast growth factor-2 reduces intraarticular adhesions

Adhesion is a serious complication after trauma or surgery. Because adhesion formation is essentially a fibrogenetic process, a series of growth factors are assumed to be involved in its development. If this is true, it may be possible that inhibition of the growth factor activity suppresses adhesion formation. The current study was conducted to verify this hypothesis on fibroblast growth factor-2 using an intraarticular adhesion model in the rabbit knee. Forty Japanese White rabbits were used. They were divided randomly into five groups of eight animals, and in three of them, activity of endogenous fibroblast growth factor-2 was suppressed locally by a neutralizing antibody. The remaining two groups served as controls, and formation of adhesions was evaluated 4 weeks after surgery. The results showed that the administration of the antibody reduced the extent of adhesions macroscopically, whereas histologic observation and collagen content measurement suggested the adhesion tissue was not affected significantly. Corresponding to the macroscopic findings, contraction of the knee was improved in the antibody groups. The findings showed that suppression of fibroblast growth factor-2 activity reduces adhesions. It is expected that control of the cytokine activity may become a novel method for reducing adhesions.

Adhesion formation in intubated rabbits increases with high insufflation pressure during endoscopic surgery

The aim of the study was to test the hypothesis that the increase in adhesion formation by CO(2) pneumoperitoneum is caused by mesothelial hypoxaemia. Therefore the effect of the intra-abdominal pressure together with the flow rate upon adhesion formation was evaluated in rabbits following laser and bipolar lesions during endoscopic surgery using humidified CO(2) at 35 +/- 1 degrees C. The intra-abdominal pressure and flow rate were 5 mmHg and 1 l/min in group 1 (n = 5), 5 mmHg and 10 l/min in group 2 (n = 4), 20 mmHg and 1 l/min in group 3 (n = 5) and 20 mmHg and 10 l/min in group 4 (n = 4) respectively. A rapid and reliable intubation method for rabbits was developed to permit high insufflation pressure. By two-way analysis of variance, total adhesion scores following a laser lesion increased with flow rate (P = 0.0003) and insufflation pressure (P = 0.002). Total adhesion scores of bipolar lesions increased with pressure (P = 0.02) but not with flow rate (P = 0.1). The total adhesion scores of laser and bipolar lesions together increased with flow rate (P = 0.005) and with insufflation pressure (P = 0.004). There was no statistical interaction between flow rate and insufflation pressure. In conclusion, the insufflation pressure in endoscopic surgery with CO(2) pneumoperitoneum is a co-factor in adhesion formation, together with desiccation.