Transforming growth factor beta2 induced pleurodesis is not inhibited by corticosteroids

Pleurodesis with povidone iodine in patients with malignant pleural effusion in a tertiary center in Nigeria

INTRODUCTION

malignant pleural effusion occurs as a consequence of a primary or metastatic malignant process involving the pleura. The aim of pleurodesis is to prevent re-accumulation of the effusion and avoid the need for repeated hospitalization. Povidone iodine has been used in other climes for pleurodesis with good results. The aim of this study is to assess the efficacy and safety of povidone iodine in producing pleurodesis as compared to tetracycline.

METHODS

the study is a prospective experimental study. The patients are randomized into two groups A (tetracycline-control) and B (povidone iodine). All patients are assessed with chest X-ray after 1 week and 1 month. The responses were ascribed as complete, partial or failure.

RESULTS

thirty patients were recruited into this study, 15 patients in each group A (tetracycline) and B (povidone iodine). The mean age was 45.7±14.24 years. The commonest primary malignancy was Breast cancer (70%) followed by bronchogenic cancer (10%). Seventy three (73%) of the patients in this study had complete response and in 7% pleurodesis failed whilst 20% has partial response. In the povidone group the success rate was 93.4% and in the tetracycline group was 93.3% with a p-value of 0.716. There was no statistical difference in the responses based on the agents used.

CONCLUSION

malignant pleural effusion is a devastating condition as it heralds the end-of-life processes of a primary malignancy. Povidone iodine is a safe, cheap, effective, widely available and effective pleurodesing agent for use in patients with malignant pleural effusion.

Chemical pleurodesis - a review of mechanisms involved in pleural space obliteration

Chemical pleurodesis is a therapeutic procedure applied to create the symphysis between the parietal and visceral pleura by intrapleural administration of various chemical agents (e.g. talk, tetracycline, iodopovidone, etc.). The two major clinical conditions treated with chemical pleurodesis are recurrent pleural effusion (PE) and recurrent spontaneous pneumothorax. Although the history of chemical pleurodesis began over a century ago, detailed data on the mechanisms of action of sclerosing agents are highly incomplete. The following article aims to present the state of knowledge on this subject.It is believed that mesothelial cells are the main structural axis of pleurodesis. In response to sclerosing agents they secrete a variety of mediators including chemokines such as interleukin 8 (IL-8) and monocyte chemoattractant protein (MCP-1), as well as growth factors - vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF) and transforming growth factor- β (TGF-β). Numerous data suggest that intact mesothelial cells and the above cytokines play a crucial role in the initiation and maintenance of different pathways of pleural inflammation and pleural space obliteration.It seems that the process of pleurodesis is largely nonspecific to the sclerosant and involves the same ultimate pathways including activation of pleural cells, coagulation cascade, fibrin chain formation, fibroblast proliferation and production of collagen and extracellular matrix components. Of these processes, the coagulation cascade with decreased fibrinolytic activity and increased fibrinogenesis probably plays a pivotal role, at least during the early response to sclerosant administration.A better understanding of various pathways involved in pleurodesis may be a prerequisite for more effective and safe use of various sclerosants and for the development of new, perhaps more personalized therapeutic approaches.

Transforming growth factor beta1 (TGF-ß1) levels in a rat model of induced pleural empyema

PURPOSE

To evaluate the concentration of transforming growth factor beta 1 (TGFB1) levels in a rat pleural effusion obtained by inoculation of intrapleural bacteria or turpentine through thoracentesis.

METHODS

Thirty-Nine Wistar rats were divided into three groups: Staphylococcus aureus (SA, n = 17); Streptococcus pneumoniae (SP, n = 12); and turpentine (control, n = 10). Pleural fluid was collected through ultrasound-guided thoracentesis 12 h, 24 h, and 36 h after instillation of bacteria or turpentine. Levels of TGFB1 were measured in pleural fluid.

RESULTS

At 12 h, mean TGFB1concentrations were 5.3450 pg/mL in the SA group, 5.3449 pg/mL in the SP group, and 5.3450 pg/mL in controls. At 24 h, they were 4.6700 pg/mL in the SA group, 4.6700 pg/mL in the SP group, and 4.6700 pg/mL in controls. At 36 h, they were 4.6699 pg/mL in the SA group and in control. No difference was observed among the groups in mean TGFB1concentration (p = 0.12); however, a significant intragroup reduction in mean TGFB1 was observed between 12 and 24 h (p < 0.01).

CONCLUSION

The transforming growth factor beta 1 concentrations were not useful as a diagnostic tool or an early marker of infected pleural effusion.

Effectiveness and safety of iodopovidone in an experimental pleurodesis model

OBJECTIVES

Chemical pleurodesis is an important therapeutic tool to control recurrent malignant pleural effusion. Among the various sclerosing agents, iodopovidone is considered effective and safe. However, in a recent study, ocular changes were described after iodopovidone was used in recurrent pneumothorax. The aim of the study was to evaluate the efficacy and morbidity of iodopovidone pleurodesis in an experimental model.

METHODS

New Zealand rabbits were submitted to intrapleural injection of iodopovidone at concentrations of 2%, 4% and 10%. Biochemical (lactic dehydrogenase, proteins, triiodothyronine, free thyroxine, urea and creatinine) and immunological (Interleukin-8 [IL-8], VEGF and TGFβ) parameters were measured in the pleural fluid and blood. After 1, 3, 7, 14 and 28 days, groups of animals were euthanized, and macro- (pleura) and microscopic (pleura and retina) analyses were performed.

RESULTS

An early pleural inflammatory response with low systemic repercussion was observed without corresponding changes in thyroid or renal function. The higher concentrations (4% and 10%) correlated with greater initial exudation, and maximum pleural thickening was observed after 28 days. No changes were observed in the retinal pigment epithelium of the rabbits.

CONCLUSION

Iodopovidone is considered to be an effective and safe sclerosing agent in this animal model. However, its efficacy, tolerance and safety in humans should be further evaluated.

Iodopovidone is as effective as doxycycline in producing pleurodesis in rabbits

BACKGROUND AND OBJECTIVE

The mechanism by which iodopovidone achieves pleurodesis is unknown. This study investigated whether iodopovidone is as effective as doxycycline in producing pleurodesis and whether systemic corticosteroids diminish its efficacy.

METHODS

Four groups of seven New Zealand rabbits were assigned to the following intrapleural treatment groups: 2 mL of 2% iodopovidone, 2 mL of 4% iodopovidone, 2 mL of 4% iodopovidone plus 0.8 mg/kg triamcinolone intramuscularly weekly and 10 mL/kg doxycycline in 2 mL. Pleural fluid was collected 24, 48 and 72 h after intrapleural injections and analysed for WCC, protein and LDH levels. The rabbits were killed 2 weeks after the injections. Pleurodesis was graded macroscopically on a scale from 1 to 8. The degree of microscopic pleural fibrosis and pleural inflammation was graded from the HE stain slides.

RESULTS

The mean volume of pleural fluid as well as the mean total WCC was significantly lower in the steroid-treated group than in the other groups. The degree of the resulting pleurodesis was similar in the 2% iodopovidone (7.00 +/- 1.29), 4% iodopovidone (7.71 +/- 0.76) and doxycycline (7.14 +/- 0.90) groups (P > 0.05) whereas the pleurodesis score of the steroid group (3.71 +/- 1.98) was significantly lower than all other groups (P < 0.05). The degree of microscopic pleural fibrosis and pleural inflammation was significantly lower in the steroid group than in the 2% iodopovidone or 4% iodopovidone group.

CONCLUSIONS

Both 2% and 4% iodopovidone can induce pleurodesis as efficaciously as doxycycline in rabbits. Systemic corticosteroids significantly decrease the efficacy of iodopovidone in producing pleurodesis.

AP-1 overexpression impairs corticosteroid inhibition of collagen production by fibroblasts isolated from asthmatic subjects

Asthma is characterized by airway remodeling associated with an increase in the deposition of ECM proteins such as type I collagen. These components are mainly produced by fibroblasts. Inhaled corticosteroids are considered the cornerstone of asthma therapy. Despite substantial evidence as to the anti-inflammatory action of corticosteroids, their effect on controlling ECM protein deposition in the airways is not completely understood. This study determined the effect of dexamethasone (Dex) on collagen production by bronchial fibroblasts derived from asthmatic and healthy subjects. Expression of procollagen mRNA in fibroblasts from asthmatics and normal controls was determined by quantitative PCR. Regulation of the procollagen-alpha(1)I promoter was evaluated by transient transfections. Transforming growth factor-beta (TGF-beta) protein expression was determined by ELISA. Protein expression of glucocorticoid receptor (GR) and interaction with activator protein-1 (AP-1), a collagen regulatory transcription factor, was assessed by Western blots, coimmunoprecipitations, and EMSA. AP-1 overexpression was performed by transient transfection using c-Fos/c-Jun expression plasmids. Dex significantly downregulated procollagen production and promoter activity in normal fibroblasts but had no effect on asthmatic fibroblasts. AP-1 and GR interaction increased after Dex stimulation in asthmatic fibroblasts. AP-1 overexpression in control fibroblasts abrogated collagen gene response to Dex. These results show that Dex failed to reduce collagen production in fibroblasts from asthmatic subjects. This impaired response may be related to AP-1 overexpression in these cells.

Influence of parecoxib (cox-2 inhibitor) in experimental pleurodesis

BACKGROUND

The intrapleural instillation of a sclerosing agent produces an inflammatory process frequently followed by pain. The treatment can include the use of analgesics or anti-inflammatory drugs. Previously, it was demonstrated (experimental studies) that corticoids and nonsteroidal anti-inflammatory drugs (diclofenac) reduce the inflammation and fibrosis produced by talc but not by transforming growth factor-beta or silver nitrate. The objective of this study was to determine whether parecoxib (COX-2 inhibitor) affects pleurodesis induced by talc or silver nitrate.

METHODS

140 rabbits received intrapleural injection (2mL) of 400mg/kg of talc or 0.5% silver nitrate. A subgroup of 70 animals received additional daily intramuscular parecoxib (1mg/kg). They were sacrificed at 4, 24, 48, 72h or 7, 14, or 28 days after the procedure. The pleural fluid was quantified; biochemical examinations (glucose, lactic dehydrogenase, and proteins) and immunologic dosages (interleukin-8, vascular endothelial growth factor, and transforming growth factor-beta(1)) were analyzed in pleural fluid and blood. Finally, macro- and microscopic pleura and lung studies were performed.

RESULTS

Evaluation after 28 days demonstrated that parecoxib reduced pleural and pulmonary inflammation but not pleural adhesions. The changes were observed precociously (congruent with 72h) and were more evident after silver nitrate injection.

CONCLUSION

Systemic parecoxib injection does not interfere with talc or silver nitrate pleurodesis. These results suggest that use of COX-2 inhibitors can be considered and depending of the results of other studies, recommended in human pleurodesis.

TGF-beta1 induces progressive pleural scarring and subpleural fibrosis

Pleural fibrosis is a misunderstood disorder which can cause severe restrictive lung disease with high morbidity and even mortality. The condition can develop in response to a large variety of diseases and tissue injury, among them infectious disease, asbestos, drugs, and radiation therapy. There is no efficient treatment to reverse established pleural fibrosis. TGF-beta1 is suspected, even if not proven, as a key cytokine in this process. In this study, we used adenoviral gene transfer of TGF-beta1 to the pleural mesothelium in rats. We show that local and transient TGF-beta1 overexpression induces homogenous, prolonged, and progressive pleural fibrosis without pleurodesis, associated with severe impairment of pulmonary function. We further demonstrate that pleural fibrosis can expand into the lung parenchyma from the visceral layer, but not into the muscle from the parietal layer. We provide evidence that matrix accumulation and fibrosis within the parenchyma evolved through a process involving "mesothelial-fibroblastoid transformation" and suggest that the pleural mesothelial cell may be an important player involved in the development of the subpleural distribution pattern known to be a hallmark of pulmonary fibrosis. This new model of pleural fibrosis will allow us to better understand the mechanisms of progressive fibrogenesis, and to explore novel antifibrotic therapies in the pleural cavity.

The short-term administration of Ketoprofen does not decrease the effect of Pleurodesis induced by talc or Doxycycline in rabbits

OBJECTIVE

To determine whether the concomitant administration of ketoprofen, a non-steroidal anti-inflammatory drug (NSAID) has any effect on the pleurodesis induced by talc or doxycycline in rabbits.

METHODS

Four groups of seven New Zealand rabbits were assigned to receive the following treatments: 400mg/kg of talc intrapleurally only (group 1), 400mg/kg of talc plus 1mg/kg of ketoprofen intramuscularly (group 2), 10mg/kg of doxycycline intrapleurally only (group 3) and 10mg/kg of doxycycline plus 1mg/kg of ketoprofen intramuscularly (group 4). Intramuscular administration of ketoprofen began 4h before the intrapleural administration of the sclerosing agents, followed by twice daily administrations for 1 week. Pleural fluid was collected 24, 48 and 72h after intrapleural injections. Pleurodesis was evaluated macroscopically and microscopically after 14 days.

RESULTS

The concomitant use of ketoprofen at 1mg/kg does not decrease the WBC, LDH, and protein in pleural fluid at 24h following intrapleural injection of talc or doxycycline. There were no significant differences in the macroscopic pleurodesis scores, the degree of microscopic pleural fibrosis, the thickness of the pleura or the percent of the pleura occupied with angiogenesis.

CONCLUSIONS

The study shows that the short-term systemic administration of NSAIDs does not affect the efficacy of pleurodesis induced by talc or doxycycline in rabbits.

The Spectrum of Pleural Effusions After Coronary Artery Bypass Grafting Surgery

Pleural effusions are common after coronary artery bypass grafting (CABG) surgery and can be categorized by time intervals: perioperative (within the first week), early (within 1 month), late (2-12 months), or persistent (after 6 months). The perioperative effusions are usually attributable to diaphragm dysfunction or internal mammary artery harvesting and are typically self-limited. Early effusions are usually attributable to postcardiac injury syndrome and may require corticosteroid treatment. Although late effusions can have multiple causes, persistent effusions are attributable to trapped lung and often require decortication. Diagnostic thoracentesis should be performed for patients with large symptomatic pleural effusions or fever after CABG surgery. The range of management includes observation, therapeutic thoracentesis, corticosteroids, or decortication depending on the cause and course of the effusion.

Influence of antiinflammatory drugs (methylprednisolone and diclofenac sodium) on experimental pleurodesis induced by silver nitrate or talc

STUDY OBJECTIVE

To determine whether the administration of antiinflammatory drugs interferes with experimental pleurodesis induced by silver nitrate or talc.

STUDY DESIGN

Two groups of 30 white New Zealand rabbits were scheduled to receive an intrapleural injection of 0.5% silver nitrate or 400 mg/kg of talc. Each group was further classified into three subgroups (10 animals each), which received the following: (subgroup 1) the sclerosing agent only, (subgroup 2) the sclerosing agent plus 1 mg/kg of methylprednisolone, and (subgroup 3) the sclerosing agent plus 1.1 mg/kg of diclofenac sodium. The antiinflammatory agents were administered IM 24 h before the sclerosing agent and daily during the first week, followed by once-weekly injections until death at 28 days. At this time, the pleural cavity was macroscopically evaluated, and samples of pleura and lungs were collected for further microscopic examination.

MEASUREMENTS AND RESULTS

The degree of pleural adhesions was higher after silver nitrate administration (p = 0.019). No reduction in the adhesions was observed after administering antiinflammatory drugs to this group (p > 0.05). Conversely, the adhesion score was significantly reduced after administration of both prednisolone (p = 0.028) and diclofenac (p = 0.032) to the animals that received talc. Administration of the antiinflammatory agents did not influence microscopic pleural or lung changes induced by silver nitrate or talc.

CONCLUSION

These results show that the sustained systemic administration of antiinflammatory agents (steroidal or nonsteroidal) reduces the degree of pleural adhesions in animals with talc-induced pleurodesis but does not affect silver nitrate-induced pleurodesis. Extrapolation of these results to humans suggests that the use of antiinflammatory drugs should be avoided in patients with talc-induced pleurodesis and that appropriate clinical studies with silver nitrate should be conducted in patients chronically treated with these antiinflammatory agents.

Combination therapy with intrapleural doxycycline and talc in reduced doses is effective in producing pleurodesis in rabbits

BACKGROUND

It has been suggested that talc and doxycycline might be acting through different pathways in creating pleurodesis. We hypothesized that combining doxycycline and talc in half the usual doses would be synergistic in inducing pleurodesis.

METHODS

Thirty-two rabbits were equally allocated into four groups: group 1, half-dose combination (5 mg/kg of doxycycline and 200 mg/kg of talc slurry); group 2, quarter-dose combination (2.5 mg/kg of doxycycline and 100 mg/kg of talc slurry); group 3, half-dose doxycycline (5 mg/kg of doxycycline); and group 4, half-dose talc (100 mg/kg of talc slurry). The pleurodesis scores from historical groups that received a full dose of talc (400 mg/kg) or doxycycline (10 mg/kg) were also compared to those obtained in the current study. Pleural fluid lactate dehydrogenase and protein levels were measured 24 h after the injection. Pleurodesis was graded from 1 (none) to 8 (> 50% symphysis) by two observers blinded to treatment groups. All rabbits underwent an ultrasonic examination on each side of their chest for the evaluation of pleurodesis.

RESULTS

The mean pleurodesis score in the half-dose combination group was significantly higher than that in the half-dose talc group, half-dose doxycycline group, and the historical full-dose talc group (p = 0.009, p = 0.01, and p < 0.05, respectively). The quarter-dose combination group also had a significantly higher mean pleurodesis score compared to the half-dose talc group (p = 0.013). The difference between the historical full-dose doxycycline and the half-dose combination or quarter-dose combination groups was not significant (p > 0.05). A significantly positive correlation existed between the pleurodesis score and the ultrasound scores (r = 0.876, p = 0.000000005).

CONCLUSIONS

This study demonstrates that the combination of half doses of talc and doxycycline is more effective than the half dose of either drug alone or the full dose of talc in producing pleurodesis in rabbits. In addition, ultrasound is an accurate imaging modality for the evaluation of pleurodesis, in that the absence of pleural gliding on ultrasound correlates well with the presence of a pleurodesis in rabbits.

Pleurodesis is inhibited by anti-vascular endothelial growth factor antibody

STUDY OBJECTIVES

The intrapleural injection of transforming growth factor (TGF)-beta2 produces pleurodesis in rabbits associated with large pleural effusions. This study investigated whether anti-vascular endothelial growth factor (VEGF) antibody has any effect on the fluid production or the pleurodesis induced by TGF-beta2.

INTERVENTIONS AND MEASUREMENTS

Three groups of seven New Zealand white rabbits were administered TGF-beta2 5.0 microg intrapleurally. Two groups received anti-VEGF antibody (10 mg/kg and 25 mg/kg) IV 24 h before TGF-beta2 injection, and the third group received no antibody. The rabbits were killed at 2 weeks, and the macroscopic pleurodesis score was determined. The degree of pleural angiogenesis was assessed by immunohistochemical staining for factor VIII.

RESULTS

The administration of anti-VEGF antibodies had no significant effect on the pleural fluid volume or the characteristics of the fluid. The mean pleurodesis score of the seven rabbits in the control group (7.71 +/- 0.76) was significantly (p < 0.05) higher than that for seven rabbits in the low-dose treatment group (4.43 +/- 2.37) and the seven rabbits in the high-dose treatment group (4.57 +/- 2.36) [+/- ]. The percentage of pleural tissue demonstrating angiogenesis in the control group (4.87 +/- 0.43%) was significantly (p < 0.05) higher than that for the low-dose (2.94 +/- 0.68%) or high-dose (2.67 +/- 0.64%) antibody groups. When all rabbits were considered, there was a highly significant correlation between the pleural vascular density scores and the pleurodesis scores (r = 0.84, p < 0.01).

CONCLUSION

VEGF and angiogenesis appear to play a pivotal role in the production of a pleurodesis.

Pathogenesis of pleural fibrosis

Pleural fibrosis resembles fibrosis in other tissues and can be defined as an excessive deposition of matrix components that results in the destruction of normal pleural tissue architecture and compromised function. Pleural fibrosis may be the consequence of an organised haemorrhagic effusion, tuberculous effusion, empyema or asbestos-related pleurisy and can manifest itself as discrete localised lesions (pleural plaques) or diffuse pleural thickening and fibrosis. Although the pathogenesis is unknown, it is likely that the complex interactions between resident and inflammatory cells, profibrotic mediators and coagulation, and fibrinolytic pathways are integral to pleural remodelling and fibrosis. It is generally considered that the primary target cell for pleural fibrosis is the subpleural fibroblast. However, increasing evidence suggests that mesothelial cells may also play a significant role in the pathogenesis of this condition, both by initiating inflammatory responses and producing matrix components. A greater understanding of the interactions between pleural and inflammatory cells, cytokines and growth factors, and blood derived proteins is required before adequate therapies can be developed to prevent pleural fibrosis from occurring.

Chemotherapeutic management of malignant pleural effusion

The management of malignant pleural effusions are a common, and sometimes difficult, therapeutic problem. This article reviews the currently available sclerosing agents and discusses novel agents that show promise for the future. Talc, tetracycline and bleomycin are currently the most widely used agents but none is an ideal sclerosant and certain adverse effects are of concern. Novel agents, particularly transforming growth factor (TGF)-beta(2) and metalloproteinase inhibitors, are being investigated, and the increase in knowledge into the mechanisms of pleural fluid formation and pleurodesis will hopefully lead to the development of targeted therapy in the future.

Effect of neutralizing transforming growth factor beta1 on the immune response against Mycobacterium tuberculosis in guinea pigs

Transforming growth factor beta (TGF-beta) is a cytokine which has been shown to suppress the antimycobacterial immune responses of humans and experimental animals. In this study, the contributions of TGF-beta to cytokine production in vivo were investigated by using the established guinea pig model of tuberculous pleurisy. Mycobacterium bovis BCG-vaccinated guinea pigs were injected intrapleurally with heat-killed virulent Mycobacterium tuberculosis. Eight days following induction of an antigen-specific pleural effusion, guinea pigs were injected intrapleurally with anti-TGF-beta1 or isotype control antibody. The following day, pleural exudates were removed, and the fluid volume and characteristics of the infiltrating cells were determined. Pleural fluid was analyzed for total interferon (IFN) and tumor necrosis factor (TNF) protein levels by using appropriate bioassays. RNA from pleural effusion cells was examined to determine TGF-beta1, TNF-alpha, IFN-gamma, and interleukin-8 mRNA levels by using real-time PCR. Proliferative responses of pleural effusion lymphocytes were examined in response to concanavalin A and purified protein derivative (PPD) in vitro. Treatment with anti-TGF-beta1 resulted in decreased pleural fluid volume and decreased cell numbers in the pleural space along with an increased percentage of lymphocytes and a decreased percentage of neutrophils. The bioactive TNF protein levels in pleural fluid were increased in guinea pigs treated with anti-TGF-beta1, while the bioactive IFN protein concentrations were not altered. Expression of TGF-beta1 and TNF-alpha mRNA was significantly increased following TGF-beta1 neutralization. Finally, PPD-induced proliferative responses of pleural cells from anti-TGF-beta1-treated animals were significantly enhanced. Thus, TGF-beta1 may be involved in the resolution of this local, mycobacterial antigen-specific inflammatory response.

Mesothelial cells: their structure, function and role in serosal repair

The mesothelium is composed of an extensive monolayer of specialized cells (mesothelial cells) that line the body's serous cavities and internal organs. Traditionally, this layer was thought to be a simple tissue with the sole function of providing a slippery, non-adhesive and protective surface to facilitate intracoelomic movement. However, with the gradual accumulation of information about serosal tissues over the years, the mesothelium is now recognized as a dynamic cellular membrane with many important functions. These include transport and movement of fluid and particulate matter across the serosal cavities, leucocyte migration in response to inflammatory mediators, synthesis of pro-inflammatory cytokines, growth factors and extracellular matrix proteins to aid in serosal repair, release of factors to promote both the deposition and clearance of fibrin, and antigen presentation. Furthermore, the secretion of molecules, such as glycosaminoglycans and lubricants, not only protects tissues from abrasion, but also from infection and possibly tumour dissemination. Mesothelium is also unlike other epithelial-like surfaces because healing appears diffusely across the denuded surface, whereas in true epithelia, healing occurs solely at the wound edges as sheets of cells. Although controversial, recent studies have begun to shed light on the mechanisms involved in mesothelial regeneration. In the present review, the current understanding of the structure and function of the mesothelium and the biology of mesothelial cells is discussed, together with recent insights into the mechanisms regulating its repair.

Comparing transforming growth factor-beta2, talc and bleomycin as pleurodesing agents in sheep

BACKGROUND

Transforming growth factor (TGF)-beta2 can produce effective pleurodesis in animals, but its efficacy has not been compared with commonly used pleurodesing agents in sheep, which have a thick pleura resembling that of humans. The acute physiological effects and the level of systemic TGF-beta absorption after its intrapleural administration have not been studied. The aims of the present study were to compare: (i) the effectiveness of TGF-beta2, talc and bleomycin in producing pleurodesis in sheep; (ii) the acute side-effects and systemic TGF-beta levels following the intrapleural administration of these agents; and (iii) histological changes after intrapleural injections of these agents.

METHODOLOGY

Twelve sheep were divided into three groups and were given a single intrapleural dose of TGF-beta2 (0.25 microg/kg), talc slurry (5 g) or bleomycin (60 IU) via a chest tube. Saline or buffer was injected into the contralateral side, which served as the control. Arterial blood gases and respiratory and heart rates were monitored for the first 24 h. Plasma levels of TGF-beta1 and TGF-beta2 were measured. Pleurodesis was graded macroscopically from 1 (none) to 8 (symphysis > 50% of hemithorax) at day 14.

RESULTS

At day 14, the pleurodesis score of the TGF-beta2 group (7.7+/-0.6) was similar to that of the talc (7.0+/-1.7) group and significantly higher than that of the bleomycin group (3.3+/-2.3; P < 0.05). No significant differences were seen in arterial blood gas analysis, vital signs and plasma TGF-beta1 and TGF-beta2 concentrations among the three groups.

CONCLUSIONS

Transforming growth factor-beta2 was as effective as talc and more so than bleomycin in inducing pleurodesis in sheep. Intrapleural administration of TGF-beta2 appeared safe. No acute changes in gaseous exchange or macroscopic abnormalities were seen following intrapleural TGF-beta2. Importantly, there was no evidence of an increase in systemic TGF-beta levels following its intrapleural administration.

Transforming growth factor beta induces vascular endothelial growth factor elaboration from pleural mesothelial cells in vivo and in vitro

Vascular endothelial growth factor (VEGF) increases vascular permeability and is important in pleural effusion formation. In studies using transforming growth factor beta (TGF-beta) to produce pleurodesis, we observed that although TGF-beta was more effective than talc or doxycycline, it induced transient production of large pleural effusions. We hypothesized that TGF-beta stimulates VEGF production in pleural tissues in vivo, and by mesothelial cells in vitro. New Zealand White rabbits (n = 33) were given TGF-beta(2) (1.7 or 5.0 microg), talc (400 mg/kg), doxycycline (10 mg/kg), or buffer intrapleurally. Pleural fluid was collected at 24 h. Intrapleural injection of TGF-beta(2) induced a dose-dependent increase in VEGF production. The pleural fluid VEGF level was 2-fold higher in rabbits given 5.0 microg of TGF-beta(2) than in those given 1.7 microg of TGF-beta(2) and 3-fold higher than in those given buffer. VEGF levels were higher after the injection of TGF-beta(2) than after administration of talc or doxycycline. The pleural fluid VEGF correlated significantly with the volume of pleural effusions (r = 0.79, p < 0.00001). In vitro, TGF-beta(2) stimulated a dose-dependent increase in VEGF production from murine pleural mesothelial cells. At 4 and 24 h, TGF-beta(2), but not talc or doxycycline, induced a significant increase in VEGF, when compared with controls. The mesothelial cell VEGF production was significantly reduced by anti-TGF-beta antibody in the TGF-beta(2), talc, and control (buffer and medium) groups. In conclusion, mesothelial cells are an important source of VEGF. TGF-beta increases the VEGF production by mesothelial cells in vivo and in vitro.

Comparing transforming growth factor beta-2 and fibronectin as pleurodesing agents

BACKGROUND

We have recently demonstrated that transforming growth factor beta-2 (TGF-beta2) can produce effective pleurodesis. Whether this effect can be reproduced by the use of its downstream proteins is not known. This study compared the effectiveness of TGF-beta2 and fibronectin in inducing pleurodesis in rabbits.

METHODOLOGY

New Zealand white rabbits (1.5-2.0 kg) were given 1.7 microg of TGF-beta2 (n=5) or 2.0 mg of cellular fibronectin (n=4) intrapleurally via a chest tube. The induced pleural fluid was collected and analyzed. The rabbits were sacrificed after 14 days. The pleurodesis was graded macroscopically from 1 (none) to 8 (symphysis > 50%).

RESULTS

All rabbits in the TGF-beta2 group developed effective pleurodesis while none in the fibronectin group had scores > 2 (pleurodesis scores 7.0 +/- 0.6 vs 1.3 +/- 0.3, P < 0.001). Rabbits that received TGF-beta2 produced large amounts of pleural fluid initially (< 4 days). Microscopically, the pleura of rabbits in the TGF-beta2 group showed prominent spindle cell proliferation and collagen deposition, but no significant inflammation or mesothelial proliferation. Pleural tissues of rabbits in the fibronectin group had occasional thin collagen deposits only. The intrapleural administration of 2.0 mg of fibronectin, a downstream product of TGF-beta, did not induce effective pleurodesis, as did the intrapleural administration of TGF-beta2.

CONCLUSIONS

The present study suggests that the mechanism by which TGF-beta2 induces pleurodesis is not predominantly dependent on the production of fibronectin.