Remodeling of peritoneal-like structures by mesothelial cells: its role in peritoneal healing

Ultrasound Changes of Postoperative Adhesion Types Over Time in Children

Postoperative fibrotic band formation is a common complication that causes bowel obstruction, chronic pain, and especially reoperation problems. We tried to evaluate the ultrasound signs of different adhesions over time in children. This descriptive study was performed in children hospital of Mashhad University of Medical Sciences. Sixty-five children aged 4 months to 15 years (mean age of 7.2 ± 6.5 years) were enrolled in the study. Complete abdominal sonography using 5 to 12 MHz multifrequency probes was performed by a pediatric radiologist. The sonographic findings and data analysis were performed. In first week after surgery, the fibrinous exudates are seen as hypoechoic shadows. It has uneven thickness and usually encases the bowel loops in a circular shape. In second week, they gradually become straighter with uniform thickness. In this period, in 68% of cases, a hyperechoic line is formed in the center of hypoechoic fibrinous exudates, which is usually placed between the bowel loops (interloop fibrosis). The omentum or mesentery entrapment in the fibrinous exudates was occurred in ∼50% and 25% of these cases, respectively. In this state, echogenic omentum or mesentery was seen simultaneously with the hypoechoic fibrinous exudates. After 1 month from surgical procedure, One of the following four sonographic patterns are seen: attachment hyperechoic omentum to retroperitoneum (50%), attachment hyperechoic mesentery to anterior abdominal wall (26%), interloop fibrosis (39%), and severe hypoechoic fibrotic band (30%). Absence of visceral sliding was seen in 65 to 80% of patients. Overall, there are five morphologic patterns of adhesion on ultrasound: fibrinous exudates, interloop fibrosis, fibrotic band, fixed omentum to retroperitoneum, and fixed mesentery to abdominal wall.

Role of microRNAs in myogenesis and their effects on meat quality in pig - A review

The demand for food is increasing day by day because of the increasing global population. Therefore, meat, the easiest and largely available source of protein, needs to be produced in large amounts with good quality. The pork industry is a significant shareholder in fulfilling the global meat demands. Notably, myogenesis- development of muscles during embryogenesis- is a complex mechanism which culminates in meat production. But the molecular mechanisms which govern the myogenesis are less known. The involvement of miRNAs in myogenesis and meat quality, which depends on factors such as myofiber composition and intramuscular fat contents which determine the meat color, flavor, juiciness, and water holding capacity, are being extrapolated to increase both the quantity and quality of pork. Various kinds of microRNAs (miRNAs), miR-1, miR-21, miR22, miR-27, miR-34, miR-127, miR-133, miR-143, miR-155, miR-199, miR-206, miR-208, miR-378, and miR-432 play important roles in pig skeletal muscle development. Further, the quality of meat also depends upon myofiber which is developed through the expression of different kinds of miRNAs at different stages. This review will focus on the mechanism of myogenesis, the role of miRNAs in myogenesis, and meat quality with a focus on the pig.

Inhibition of adhesion, proliferation, and invasion of primary endometriosis and endometrial stromal and ovarian carcinoma cells by a nonhyaluronan adhesion barrier gel

Endometriosis is a chronic disease of women in the reproductive age, defined as endometrial cells growing outside of the uterine cavity and associated with relapses. Relapses are hypothesized to correlate with incomplete surgical excision or result from nonrandom implantation of new endometrial implants in adjacent peritoneum. Thus, surgical excision could lead to free endometriotic cells or tissue residues, which readhere, grow, and invade into recurrent lesions. Barrier agents are frequently used to prevent postoperative adhesions. We tested if the absorbable cell adhesion barrier gel Intercoat consisting of polyethylene oxide and sodium carboxymethyl cellulose could inhibit cellular adhesion, proliferation, and invasion of primary endometriosis and endometrial cells. Due to an association of endometriosis with ovarian carcinoma, we tested two ovarian carcinoma cell lines. Prior to cell seeding, a drop of the barrier gel was placed in cell culture wells in order to test inhibition of adherence and proliferation or coated over a polymerized collagen gel to assay for prevention of invasion. Results showed that the barrier gel significantly inhibited cell adherence, proliferation, and invasion of endometriosis and endometrial stromal cells as well as ovarian carcinoma cells in culture. Our findings could help to prevent local cell growth/invasion and possible consequent recurrences.

Novel anti-adhesive barrier Biobarrier reduces growth of colon cancer cells

BACKGROUND

Postoperative peritoneal carcinomatosis together with adhesion formation are considered as two major clinical complications after resection of malignant abdominal tumors, jeopardizing the beneficial effect of the curative surgery. Biobarrier is a novel anti-adhesive barrier fulfilling the criteria for a good adhesion preventive agent, possessing biochemical properties that may enable it to function as a dual efficient device, reducing both adhesion and tumor development. This study aims to evaluate the effect of novel anti-adhesive device Biobarrier on intra-abdominal tumor progression.

MATERIALS AND METHODS

Cells from cancer cell line BN7005H1D2 were treated with Biobarrier to determine the effect of Biobarrier on cell attachment and viability in vitro. For the in vivo experiments, bilateral peritoneal trauma was inflicted in a reproducible syngeneic rat model. To mimic the clinical situation, the animals received an intraperitoneal injection of BN7005H1D2 cancer cells at the end of surgery, resembling perioperative tumor spill after intraperitoneal instillation of Biobarrier. Animals without given anti-adhesive treatment were used as control.

RESULTS

Biobarrier applied in vitro hindered cells from attachment to the wells. In vivo treatment with Biobarrier significantly reduced tumor growth at both sites of surgical trauma (P = 0.001 and 0.015) and other non-traumatized intraperitoneal sites (P = 0.021).

CONCLUSIONS

Biobarrier maybe effective in reducing intra-abdominal tumor cell implantation with subsequent tumor development in conjunction with peritoneal trauma in a syngeneic rat model.

Mesothelial morphology and organisation after peritoneal treatment with solid and liquid adhesion barriers--a scanning electron microscopical study

Separation of traumatized tissue represents the only promising strategy in postoperative adhesion prevention, a relevant clinical problem after surgical intervention. In the present study scanning electron microscopy (SEM) and subsequent morphometry were used to analyse the tissue response to five commercial adhesion barriers. Standardised peritoneal lesions in Wistar rats were covered with solid and viscous barrier materials and semiquantitatively analysed 14 days postoperatively. Striking morphological differences in lesion surface organisation between the barrier groups became apparent with colonisation of the barrier by mesothelial cells to different degrees. Furthermore, the mesothelial cells showed either a normal or activated phenotype depending on the underlying biomaterial. These experiments demonstrate that the examination by SEM gives useful insights into the performance of barrier materials and the cellular processes of adhesion prevention, since mesothelial cells play an active role in the pathogenesis of adhesion formation.

Characterizing omental adhesions by culturing cells isolated from a novel in vivo adhesion model

Although it has been established that postoperative adhesions in the peritoneal cavity are the consequence of injury to the peritoneum, there is much controversy over the nature of the cells giving rise to this neotissue. Here, we establish a novel adhesiogenic model in the rabbit to analyze the phenotype and proliferation in vitro of cells comprising adhesion tissue seven days postsurgery. Adhesion-free omentum tissue was used as control. Cells derived from adhesions and from the control omentum were subcultured and characterized through immunofluorescence and Western blotting procedures to determine markers of cell differentiation and pluripotential, and viability and proliferation assays. Our findings indicate the existence of a mesenchymal population in the omentum revealed by markers of pluripotent cells with high angiogenic capacity. This population seems to be responsible for the adhesions formed in response to mesothelial damage. Depending on the local environment, mesenchymal cells are capable of in vivo differentiation towards at least two different cell phenotypes rendering two types of adhesions with clearly differentiated characteristics. One type of adhesion shows a highly vascularized adipose morphology containing cells differentiating into a vascular lineage. The other adhesions are fibrous with large amounts of collagen and comprised mainly of myofibroblasts conferring less compliance to this tissue.

Intercellular adhesion molecule-1 and gelatinase expression in human peritoneal mesothelial cells during propagation in culture

Mesothelial cells are involved in a variety of biological processes, which include the formation of peritoneal adhesions. The cultures of human peritoneal mesothelial cells comprise an important tool to investigate the behavior and functions of mesothelial cells. Very little is known about the differences among mesothelial cells isolated from different sources and about the changes in specific functions as caused by cell propagation in vitro or that result from storage of cells at low temperatures. This study aims to characterize 2 particular cellular activities relevant for tissue repair, which include the expression of intercellular adhesion molecule-1 (ICAM-1) and the gelatinase activity; in addition, this study will assess the effect of hyaluronan, which is an antiadhesive agent, on these cellular activities. Viable cell lines were established from both omentum and peritoneal lavage fluid from 7 patients. Both ICAM-1 expression, which was measured by enzyme-linked immunosorbent assay (ELISA), and matrix metalloproteinase (MMP) bioactivity, which was measured by zymography, were measured in the 2nd and 4th passage; the latter also was measured after freezing and storing of cells in liquid nitrogen. The effects of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), phorbol myristate acetate (PMA), and hyaluronan were analyzed. ICAM-1 was constitutively expressed and stimulated by IL-1beta, TNF-alpha, and PMA. All cell lines produced both MMP-2 and MMP-9. Only the latter activity was affected by TNF-alpha and, especially so, PMA. Differences were found between the 2nd and 4th passage, as well as between cells of different lineage, mostly so if the relative stimulation by the various agents was compared. The addition of sodium hyaluronate either to control cultures or to cultures together with any of the 3 stimuli examined did not significantly change either ICAM-1 expression or gelatinase activity. The freezing and storage of cells did not affect their functions. Both the human omentum and peritoneal lavage fluid are good sources to establish mesothelial cell lines, which can be propagated also after freezing without qualitative changes in their ability to express ICAM-1 and produce the gelatinases. For omental cells, a differential effect of stimulation occurs depending on whether the cells have been passaged 2 or 4 times. The presence of hyaluronan did not affect the expression of ICAM-1 or the gelatinases.

Chondroitin sulphate decreases collagen synthesis in normal and scleroderma fibroblasts through a Smad-independent TGF-beta pathway--implication of C-Krox and Sp1

Despite several investigations, the transcriptional mechanisms which regulate the expression of both type I collagen genes (COL1A1 and COL1A2) in either physiological or pathological situations, such as scleroderma, are not completely known. In this study, we determined the effects of both native ichtyan chondroïtin sulphate (CS) and its derived hydrolytic fragments (CSf) on human normal (NF) and scleroderma (SF) fibroblasts. Here, we demonstrate for the first time that CS and CSf exert an inhibitory effect on type I collagen protein synthesis and decrease the corresponding mRNA steady-state levels of COL1A1 and COL1A2 in NF and SF. These glycosaminoglycan molecules repress COL1A1 gene transcription through a -112/-61 bp sequence upstream the start site of transcription and imply hc-Krox and Sp1 transcription factors. In addition, CS and CSf induced a down-regulation of TβRI expression. As a conclusion, our findings highlight a possible new role for CS and CSf as anti-fibrotic molecules and could help in elucidating the mechanisms of action by which CS and CSf exert their inhibitory effect on type I collagen synthesis.

Inhibition of CCL1-CCR8 interaction prevents aggregation of macrophages and development of peritoneal adhesions

Peritoneal adhesions are a significant complication of surgery and visceral inflammation; however, the mechanism has not been fully elucidated. The aim of this study was to clarify the mechanism of peritoneal adhesions by focusing on the cell trafficking and immune system in the peritoneal cavity. We investigated the specific recruitment of peritoneal macrophages (PMphi) and their expression of chemokine receptors in murine models of postoperative and postinflammatory peritoneal adhesions. PMphi aggregated at the site of injured peritoneum in these murine models of peritoneal adhesions. The chemokine receptor CCR8 was up-regulated in the aggregating PMphi when compared with naive PMphi. The up-regulation of CCR8 was also observed in PMphi, but not in bone marrow-derived Mphi, treated with inflammatory stimulants including bacterial components and cytokines. Importantly, CCL1, the ligand for CCR8, a product of both PMphi and peritoneal mesothelial cells (PMCs) following inflammatory stimulation, was a potent enhancer of CCR8 expression. Cell aggregation involving PMphi and PMCs was induced in vitro in the presence of CCL1. CCL1 also up-regulated mRNA levels of plasminogen activator inhibitor-1 in both PMphi and PMCs. CCR8 gene-deficient mice or mice treated with anti-CCL1-neutralizing Ab exhibited significantly reduced postoperational peritoneal adhesion. Our study now establishes a unique autocrine activation system in PMphi and the mechanism for recruitment of PMphi together with PMCs via CCL1/CCR8, as immune responses of peritoneal cavity, which triggers peritoneal adhesions.

Response of human peritoneal mesothelial cells to inflammatory injury is regulated by interleukin-1beta and tumor necrosis factor-alpha

Peritoneal injury is often associated with alterations of the mesothelium, resulting in peritoneal healing and adhesion formation. We analyzed the effects of pro-inflammatory cytokines on cell morphology and proliferation of human peritoneal mesothelial cells (HPMC). After 48 hours, HPMC formed a confluent layer with cell volumes of 2,662+/-111 fL. Treatment of HPMC with interleukin-1beta and tumor necrosis factor-alpha (TNF-alpha) induced mesothelial disintegration and alterations in mesothelial cell morphology, which were associated with an interleukin-1beta-triggered increase in cell volume (3,028+/-118 fL; p<0.05) and exfoliation of cells into the supernatants of cell cultures (p<0.05). Whereas TNF-alpha arrested HPMC in the G0/G1 phase (p<0.05), interleukin-1beta caused an increase of cells into the S phase of the cell cycle. In addition, interleukin-1beta and interferon-gamma exerted a proliferative effect on HPMC. These changes were independent from mesothelial Na+/H+ antiporter-1 expression. Our data indicate that the response of HPMC to inflammatory injury is regulated by interleukin-1beta and TNF-alpha reflecting their putative role in peritoneal wound healing and adhesion formation.

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.

Effect of a matrix metalloproteinase activity and TNF-alpha converting enzyme inhibitor on intra-abdominal adhesions

BACKGROUND

Formation of intra-abdominal adhesions depends, in part, on the activity of serine proteinases. Matrix metalloproteinases (MMP) are required for epithelialization of skin wounds but their involvement in mesothelialization of peritoneal wounds and in adhesion pathogenesis is not known. Early tumor necrosis factor-alpha (TNF-alpha) levels have been proposed to reflect propensity to adhesion formation.

OBJECTIVE

The impact of MMP activity and secreted TNF-alpha on peritoneal adhesion formation and healing was investigated through systemic administration of the synthetic broad-spectrum MMP and TNF-alpha-converting enzyme (TACE) inhibitor GM 6001.

METHODS

Female Sprague-Dawley rats of 4-6 weeks of age were injected subcutaneously daily with GM 6001 100 mg/kg (n = 12) or vehicle (n = 10) starting two days before surgery. In each rat, two standardized peritoneal wounds, 20 mm x 5 mm, were made. One peritoneal wound was sutured whereas the contralateral wound healed by secondary intention. Adhesion formation and peritoneal healing, cell proliferation, and hydroxyproline concentrations were evaluated on postoperative day 7.

RESULTS

Total serum TNF-alpha levels increased in vehicle-treated rats (p = 0.019) while GM 6001 treatment effectively prevented the rise in the postoperative phase (p < 0.001). No significant differences were observed in the extent of adhesion formation (p = 0.67) between control (65.0%) and GM 6001-treated (61.5%) animals, or peritoneal wound healing or cell proliferation. Hydroxyproline levels increased in the wounds (p = 0.014) but were not different between the two groups (p = 0.14).

CONCLUSIONS

Lack of a striking effect of the MMP and TACE antagonist GM 6001 on postoperative adhesions suggests that MMP activity and TNF-alpha might not be major adhesiogenic factors.

Molecular characterization of tumour heterogeneity and malignant mesothelioma cell differentiation by gene profiling

Malignant mesothelioma is an aggressive tumour, characterized by a variable differentiation pattern and poor prognosis. At present, the clinical outcome in patients with malignant mesothelioma is mainly predicted by the morphological phenotype of the tumour. However, this conventional clinicopathological parameter is of limited value, partly because of the biological heterogeneity of this tumour and poor understanding of the regulatory mechanisms underlying the various patterns of growth. To elucidate the intrinsic molecular programmes that determine tumour differentiation, oligonucleotide arrays were used in an in vitro model of mesothelioma differentiation. The analysis of 2059 genes detected 102 genes that were significantly deregulated. Clustering of these genes into functional categories showed distinctive patterns for the two phenotypes, namely epithelioid and sarcomatoid. The molecular fingerprint of the sarcomatoid tumour component indicates overrepresentation of growth factor receptors and growth factor binding proteins, whereas epithelioid mesothelioma cells express other tumour-promoting factors involved in differentiation, metabolism, and regulation of apoptosis. These differences in the molecular phenotype may give a better basis for diagnosis and for designing novel therapies.

Molecular Characterization of Postoperative Adhesions: The Adhesion Phenotype

Postoperative adhesion development remains a very frequent occurrence, which is often unrecognized by surgeons because of limited ability to conduct early second-look laparoscopies. The consequences include infertility, pelvic pain, bowel obstruction, and difficult reoperative procedures. To date, approaches to limit adhesions primarily have involved barriers to separate tissue during reepithelization. Future progress in regulating adhesion development and tissue fibrosis likely will require an improved understanding of the molecular processes involved in normal peritoneal repair and its aberrations leading to adhesion development. We hypothesize that tissue hypoxia (in part resulting from tissue incision, fulguration, suture ligation, etc.) is the major inciting event, which leads to a coordinated series of molecular events that promote an inflammatory response leading to enhanced tissue fibrosis. These events are reduced plasminogen activator activity, extracellular matrix deposition, increased cytokine production, increased angiogenesis, and reduced apoptosis (programmed cell death). Improved understanding of these events and their regulation will provide the opportunity to regulate better postoperative adhesion development and tissue fibrosis, thereby reducing the morbidity and mortality they cause.

Mesothelial Differentiation as Reflected by Differential Gene Expression

Human mesothelial cells obtained from benign effusions retain their proliferative capacity and grow uniformly either with a fibroblastic or epithelioid morphology in vitro. These cultures therefore provide a model for the process of mesothelial differentiation in vivo. To study this differentiation, we isolated differentially expressed genes obtained by suppression subtractive hybridization. Of the nine genes found to be overexpressed in fibroblastic mesothelial cells, three are matrix-associated (integrin alpha5, collagen binding protein 2, human cartilage glycoprotein 39), whereas the others are associated with a proliferative cell type (14-3-3 epsilon, plexin B2, N33, and three genes encoding ribosomal elements). Seven of the eight genes upregulated in the epithelioid phenotype are related rather to specialized functions, such as metabolism (aldose reductase, lecithin:cholesterol acyltransferase, ATPase 6), cytoskeletal composition (cytokeratins 7 and 8), and regulation of differentiation (granulin, annexin II). Immunohistochemistry with available antibodies to six of the differentially expressed gene products confirmed the differences also in pleural tissues, where submesothelial cells displayed the fibroblastic markers, whereas surface cells displayed the epithelioid markers. In summary, this approach revealed a pattern of genes coordinately regulated during mesothelial differentiation and suggests that mesothelium may regenerate also by recruiting cells from the submesothelial layer. Some of the gene products may also be useful markers for differentiation and activation in serosal tissues.

Role of peritoneal mesothelial cells in peritonitis

Background

Peritoneal mesothelial cells have a remarkable capacity to respond to peritoneal insults. They generate an intense biological response and play an important role in the formation of adhesions. This review describes these activities and comments on their relationship to surgical drainage, peritoneal lavage and laparostomy in the management of patients with peritonitis.

Methods and results

Material was identified from previous review articles, references cited in original papers and a Medline search of the literature. The peritoneal mesothelium adapts to peritonitis by facilitating the clearance of contaminated fluid from the peritoneal cavity and inducing the formation of fibrinous adhesions that support the localization of contaminants. In addition, the fluid within the peritoneal cavity is a battleground in which effector mechanisms generated with the involvement of peritoneal mesothelial cells meet the contaminants. The result is a complex mix of cascading processes that have evolved to protect life in the absence of surgery.

Conclusion

Future advances in the management of patients with severe peritonitis may depend upon molecular strategies that modify the activity of peritoneal mesothelial cells.

Effect of glucose on the expression of type I collagen and transforming growth factor-beta1 in cultured human peritoneal fibroblasts

OBJECTIVE

To determine the effect of high glucose levels on the expression of type I collagen, and whether this effect is regulated by transforming growth factor (TGF)-beta1 in human peritoneal fibroblasts in culture.

DESIGN

Prospective experimental study.

SETTING

University medical center.

PATIENT(S)

Primary cultures of fibroblasts established from peritoneal tissues of five patients. High glucose treatment of the primary cultured fibroblasts.

MAIN OUTCOME MEASURE(S)

Primary cultures of human peritoneal fibroblasts were incubated with varying amounts of glucose (1-5 g/L) for 24 hours. Total RNA was extracted from human peritoneal fibroblasts and converted to cDNA by reverse transcriptase. Multiplex reverse transcriptase/polymerase chain reaction (PCR) simultaneously co-amplifying beta-actin with TGF-beta1 or type I collagen mRNAs was used to quantitate type I collagen and TGF-beta1 mRNA levels in response to increasing glucose concentrations with and without TGF-beta1 antibody treatment.

RESULT(S)

There was a significant increase in the mRNA for type I collagen and TGF-beta1 in response to increasing glucose concentrations in a dose response-dependent manner. The TGF-beta1 antibody treatment resulted in an 83% and 68% decrease in type I collagen and TGF-beta1 mRNA levels, respectively.

CONCLUSION(S)

Increasing glucose concentrations stimulated type I collagen expression in human peritoneal fibroblasts in culture. A potential mediator for this effect is TGF-beta1. These results have implications not only for individuals with diabetes mellitus who may be predisposed to greater postoperative adhesion development, but also for individuals with surgical stress responses after surgery.

Transforming growth factors beta1, beta2 and beta3 and their receptors are differentially expressed in human peritoneal fibroblasts in response to hypoxia

PROBLEM

Little is known about the role of peritoneal fibroblasts in adhesion formation. This study determines the effect of hypoxia and transforming growth factor (TGF)-beta1 treatment on the expression of TGF-beta1-3 and TGF-betaI and betaII receptors in human peritoneal fibroblasts (HPF). TGF-beta isoforms and their receptors have been implicated as mediators of the healing process and adhesion development.

METHODS

HPF were cultured under normal and hypoxic condition, and treated with and without (1 ng/mL) TGF-beta1 for 24 hr. Total RNA from each group was subjected to multiplex reverse transcriptase-polymerase chain reaction (RT/PCR) to quantitate TGF-beta1-3 and TGF-betaI and betaII receptors messenger RNA (mRNA) levels.

RESULTS

Hypoxia resulted in a significant increase in TGF-beta1 (26%; P < 0.05), TGF-betaIR (34%; P < 0.05) and TGF-betaIIR (29%; P < 0.05) mRNA levels, with no effect on TGF-beta2 or beta3. TGF-beta1 treatment resulted in a significant increase in TGF-beta1 (35%; P < 0.05), but a decrease in TGF-beta2 (22%; P < 0.05) and no effect on TGF-beta3, TGF-betaIR or TGF-betaIIR. Combined treatment of hypoxia and TGF-beta1 caused a significant increase in TGF-beta1 (37%; P < 0.05), TGF-beta2 (12%; P < 0.05), TGF-betaIR (32%; P < 0.05) and TGF-betaIIR (34%; P < 0.05). There is no significant change in the mRNA levels of TGF-beta3 in any of the treatments.

CONCLUSION

Hypoxia and TGF-beta1 treatments of cultured HPF modulate the expression of TGF-beta1, beta2 and beta3 and their receptors betaIR and betaIIR by increasing the ratio of TGF-beta1 and beta2 to beta3, thus favoring the development of peritoneal adhesion.

Hypoxia-induced irreversible up-regulation of type I collagen and transforming growth factor-beta1 in human peritoneal fibroblasts

OBJECTIVE

To determine whether restoration of normoxia after a hypoxic insult returns the molecular expression of type I collagen and TGF-beta1 to baseline levels.

DESIGN

Prospective experimental study.

SETTING

University medical center.

PATIENT(S)

Primary cultures of fibroblasts established from peritoneal tissues of five patients.

INTERVENTION(S)

Hypoxia treatment of the primary cultured fibroblasts.

MAIN OUTCOME MEASURE(S)

Cultured human peritoneal fibroblasts (HPF) were maintained under hypoxic conditions (2% oxygen) for 24 hours and then transferred into normal culture conditions (normoxia) for another 24 hours. Total cellular RNA from cells was collected and subjected to multiplex reverse transcription polymerase chain reaction to quantitate type I collagen and transforming growth factor (TGF)-beta1 mRNA levels in response to these treatments.

RESULT(S)

Hypoxia treatment resulted in 30% and 50% increases in type I collagen and TGF-beta1 expression, respectively. Restoration of normoxia after hypoxia treatment failed to restore type I collagen and TGF-beta1 expression to their baseline levels.

CONCLUSION(S)

These data support the hypothesis that hypoxia induces irreversible molecular changes in peritoneal fibroblasts that produce a phenotype that increases extracellular matrix expression and thereby would promote adhesion development. Thus once a phenotype consistent with increased adhesion development is manifested, restoration of oxygen supply does not reverse the stimulation of HPF type I collagen and TGF-beta1 expression. This observation may in part explain the clinical observation that adhesion reformation is more difficult to prevent than de novo adhesion formation.

Apoptosis and proliferation of human peritoneal fibroblasts in response to hypoxia

OBJECTIVE

To determine the effect of hypoxia on apoptosis and proliferation of fibroblasts cultured from normal peritoneum or adhesions.

DESIGN

Prospective experimental study.

SETTING

University medical center.

PATIENT(S)

Primary cultures of fibroblasts established from peritoneal and adhesion tissues of the same patients.

INTERVENTION(S)

Hypoxia treatment of the primary cultured fibroblasts.

MAIN OUTCOME MEASURE(S)

Apoptosis was assessed by the TUNEL assay and by the BCL-2-BAX expression ratio, as determined using multiplex reverse transcription polymerase chain reaction. The proliferation rate of these cells was determined by measuring the proliferative fraction using the flow cytometry in adhesion and peritoneal fibroblasts under normal and hypoxic conditions.

RESULT(S)

Compared with fibroblasts from normal peritoneum, fibroblasts from adhesions had significant complementary decreases in apoptosis and an increase in proliferation. In response to hypoxia, the Bcl-2-bax mRNA ratio was significantly higher in fibroblasts from adhesions as compared with fibroblasts from normal peritoneum. The degree of apoptosis induced by hypoxia correlated with the increase in the bcl-2-bax ratio in fibroblasts derived from both normal peritoneum and adhesions.

CONCLUSION(S)

Hypoxia induces proliferation while inhibiting apoptosis in fibroblasts from adhesion, thereby creating a phenotype that would favor adhesion development.

Molecular characterization of fibroblasts isolated from human peritoneum and adhesions

OBJECTIVE

To determine the response of adhesion and peritoneal fibroblasts to hypoxia.

DESIGN

Prospective experimental study.

SETTING

University medical center.

PATIENT(S)

Primary cultures of fibroblasts established from the peritoneal and adhesion tissues of the same patients (n = 2) to minimize genetic variations.

INTERVENTION(S)

Hypoxia treatment of the primary cultured fibroblast.

MAIN OUTCOME MEASURE(S)

Analyze the expression of extracellular matrix (ECM) components, metalloproteinases and their tissue inhibitors, growth factors, and cytokines in adhesion and peritoneal fibroblasts under normal and hypoxic conditions by reverse transcriptase/polymerase chain reaction analysis.

RESULT(S)

Compared to peritoneal fibroblasts, adhesion fibroblasts had a significant increase in the basal mRNA levels for collagen I, fibronectin, MMP-1, TIMP-1, TGF-beta 1, TGF-beta 2, and IL-10. Hypoxia resulted in a further increase in collagen 1, fibronectin, TIMP-1, TGF-beta 1, TGF-beta 2, IL-10, and IFN-gamma mRNA levels in both peritoneal and adhesion fibroblasts. The increase was more profound in adhesion fibroblasts.

CONCLUSION(S)

Hypoxia induces molecular changes in both peritoneal and adhesion fibroblasts, creating a milieu that favors adhesion development. The effect of hypoxia was more profound on adhesion fibroblasts.

Induction of hyaluronan metabolism after mechanical injury of human peritoneal mesothelial cells in vitro

BACKGROUND

Hyaluronan (HA) is an important extracellular matrix component that is involved in cell movement and tissue repair. In vertebrates, HA synthase genes (HAS 1, HAS 2, and HAS 3) that control the synthesis of HA have been identified. In this article, we investigated HA synthesis in the response of human peritoneal mesothelial cells (HPMCs) to injury.

METHODS

The expression of HAS 1, HAS 2, and HAS 3 mRNA and the synthesis of [(3)H]-labeled HA were examined in an in vitro model of peritoneal mesothelial cell damage. The staining for uridine diphosphoglucose dehydrogenase, a key enzyme in the synthesis of HA, and biotinylated HA-binding protein was used to determine the cellular location of HA synthesis and its site of deposition.

RESULTS

Growth-arrested human HPMCs expressed low levels of mRNA for HAS 2 and HAS 3 but not HAS 1. Following injury to the monolayer, HAS 2 was up-regulated by 6 hours, reaching maximal expression between 12 and 24 hours. In contrast, the expression of HAS 3 was down-regulated. During the same time period, synthesis of HA was increased in the injured monolayer. This synthetic activity appeared to be restricted to cells at the edge of the wound and to cells entering the wound. In a separate series of experiments, the addition of HA to the injured monolayer at a concentration range found in peritoneal fluid (50 to 3300 ng/mL) increased the migration of cells into the wound in a dose-dependent manner.

CONCLUSIONS

These studies provide evidence that HA is an important component of peritoneal mesothelial cell migration. The results also suggest that in this process, there is differential regulation of HAS gene expression and that the synthesis of HA is limited to cells located at the leading edge of the wound.

An in vivo evaluation of a chondroitin sulfate solution to prevent postoperative intraperitoneal adhesion formation

PURPOSE

The goal of this study was to determine the efficacy of a single intraperitoneal administration of a chondroitin sulfate solution in preventing postoperative adhesion formation. METHODS. Twenty-five Sprague-Dawley rats had a 1-cm(2) area of cecal serosa abraded. Controls (CON, n = 5) received no treatment, the chondroitin sulfate group (CS, n = 10) received chondroitin sulfate (0.013 g/kg) in 0.9% NaCl intraperitoneally (ip), and vehicle controls (VC, n = 10) received an equal volume of 0.9% NaCl solution ip before the abdomen was closed. All animals were sacrificed on postoperative day 10. The extent of adhesion was quantified according to Mazuji's adhesion grade (0 to 4: 0 = no adhesion and 4 = very dense adhesion) and quantitated after H&E, trichome, and immunohistochemical staining for fibrin and collagen type I and type III using digital image analysis.

RESULTS

The mean Mazuji's adhesion grade in the CON was 4.0 +/- 0.0, in the VC 2.60 +/- 0.37, and in the CS 1.3 +/- 0.42 (P < 0.01 for CS vs CON and P < 0.05 for CS vs VC comparisons). The mean gray-scale intensity (0-255: 0 = dense amount and 255 = none) of adhesion density in the CON was 105. 5 +/- 5.5, in the VC 125 +/- 15.0, and in the CS 178.3 +/- 21.0 (P < 0.01 for CS vs CON and P < 0.05 for CS vs VC comparisons). The mean adjusted intensity stain indices (AISI) for fibrin and collagen type I in the CON were 59 +/- 17 and 53 +/- 19, in the VC 27 +/- 3 and 25 +/- 7, and in the CS 16 +/- 5 and 6 +/- 3, respectively (P < 0.05 between CS and CON comparisons). The AISI of collagen type III was not significant among all the groups (P > 0.1).

CONCLUSIONS

The extent of early postoperative intra-abdominal adhesion formation as determined by gross assessment and from quantitation of fibrin and collagen type I deposition was significantly reduced by a single intraperitoneal administration of a chondroitin sulfate solution.

Alteration of type I and III collagen expression in human peritoneal mesothelial cells in response to hypoxia and transforming growth factor-beta1

Overexpression and accumulation of extracellular matrix is central to peritoneal adhesion formation following surgically induced tissue trauma. Transforming growth factor-beta1 and hypoxia have been implicated in tissue fibrosis and postoperative adhesion formation. To extend this observation we examined whether transforming growth factor-beta1 and/or hypoxia regulate the expression of type I and III collagen in human peritoneal mesothelial cells. Cultured human mesothelial cells were maintained under hypoxia (2% oxygen), or treated with transforming growth factor-beta1 (1 ng/ml) or a combination of hypoxia and transforming growth factor-beta1. Total cellular RNA from treated and untreated cells were collected and subjected to multiplex reverse transcription/polymerase chain reaction to quantitate collagen I and III mRNA levels in response to these treatments. The results indicate that 6 hours of hypoxia increased collagen III mRNA by 7.2 fold which was further increased to 9.4 fold following transforming growth factor-beta1 treatment; in contrast collagen I mRNA decreased by 0.42 fold which was further decreased by 0.3 fold following transforming growth factor-beta1 treatment. Transforming growth factor-beta1 treatment under normal conditions resulted in an 8.4-fold increase and a 0.3-fold decrease in collagen III and I mRNA levels, respectively. Hypoxia treatment also resulted in a 1.9-fold increase in transforming growth factor-beta1 mRNA level compared with control. The ratio of type III/I collagen was increased in response to transforming growth factor-beta1 treatment under hypoxic condition. In conclusion, the data suggest that hypoxia may modulate extracellular matrix production by human mesothelial cells via a transforming growth factor-beta1 dependent mechanism.