An inhibitor of cell proliferation associated with adhesion formation is suppressed by N,O-carboxymethyl chitosan

Regulation and function of IL-22 in peritoneal adhesion formation after abdominal surgery

Peritoneal adhesion occurs frequently after gastrointestinal/gynecological surgery. Tissue repair and regeneration are very important during this process. IL-22 is an important cytokine that is secreted from immune cells but functions on mesenchymal cells, such as mesothelial cells. The objective of this study was to investigate the roles of IL-22 and its regulators during adhesion formation. Postsurgical peritoneal drainage fluid from patients and rodent models was examined by enzyme-linked immunosorbent assay and fluorescence-activated cell sorting. It was observed that IL-22 expression in the abdominal cavity was rapidly induced 12 hours after surgery and then slowly decreased to a lower, steady level for up to 7 days after surgery. However, neutralizing IL-22 at the time point at which the highest level of expression was observed failed to reduce adhesion, but neutralizing IL-22 at a later time point, i.e., 3 days after surgery, prevented adhesion significantly. The IL-22 receptor was induced on the mesothelial membrane, and IL-22BP, an inhibitor of IL-22, was reduced 3 days after surgery. Furthermore, IFN-γ was identified to have the ability to induce IL-22R, and IL-18, which was induced by the infiltrating macrophages, was found to inhibit IL-22BP expression both in vivo and in vitro. Together, these data suggest that IL-22 may promote adhesion formation and that the regulation of IL-22, IL-22R, and IL-22BP may have therapeutic potential to prevent adhesion formation after surgery without disturbing the normal immune process.

The Effect of Daikenchuto, Japanese Herbal Medicine, on Adhesion Formation Induced by Cecum Cauterization and Cecum Abrasion in Mice

Daikenchuto (DKT) has been widely used for the treatment of postsurgical ileus in Japan. However, its effect on postsurgical adhesion formation has been obscure. In this study, the effect of DKT on postsurgical adhesion formation induced by cecum cauterization or cecum abrasion in mice was investigated. First, the expression of adhesion-related molecules in damaged ceca was investigated by quantitative (q)RT-PCR. During 24 h after surgery, mRNA expressions of interferon-γ (IFN-γ), plasminogen activator inhibitor-1 (PAI-1), interleukin-17 (IL-17), and Substance P (SP) in cauterized ceca and those of PAI-1 and IL-17 in abraded ceca were significantly up-regulated. Next, the effect of DKT on adhesion formation macroscopically evaluated with adhesion scoring standards. DKT (22.5-67.5 mg/d) was administered orally for 7 d during the perioperative period, and DKT did not reduce adhesion scores in either the cauterization model (control : DKT 67.5 mg/d, 4.8 ± 0.2 : 4.8 ± 0.2) or in the abrasion model (control : DKT 67.5 mg/d, 4.9 ± 0.1 : 4.5 ± 0.3). Histologically, collagen deposition and leukocyte accumulation were found at the adhesion areas of control mice in both models, and DKT supplementation did not alleviate them. Last, effect of DKT on expression of proadhesion moleculs was evaluated. DKT also failed to down-regulate mRNA expression levels of them in damaged ceca of both models. In conclusion, PAI-1 and IL-17 may be key molecules of postsurgical adhesion formation. Collagen deposition and leukocytes accumulation are histological characteristic feature of post-surgical adhesion formation. DKT may not have any preventive effect on postsurgical adhesion formation in mice.

Osteogenic effectiveness of photo-immobilized bone morphogenetic protein-2 using different azidophenyl-natural polymer carriers in rat calvarial defect model

The osteogenetic potential of photo-immobilized azdiophenyl (Az)-natural polymers as a carrier of bone morphogenetic protein-2 (BMP-2) was assessed in 56 rats randomized to four groups. The control group comprised implanted collagen sheet with BMP-2. In the three experimental groups, the implant comprised collagen sheet with photo-immobilized BMP-2 on Az-gelatin (Az-Gel), Az-O-carboxymethyl chitosan (Az-OMC), or Az‑O‑carboxymethyl low molecular chitosan (Az-LMC). Micro-computed tomography analysis revealed more regenerated bone in Az-Gel at 8weeks. Immunohistochemical analysis at 4weeks revealed that the positively expressed cellular ratio in RUNX2-stained cells was significantly higher in Az-Gel and Az-OMC groups. At 8weeks, only the Az-Gel group showed higher positively expressed cellular ratio compared with the control group. These results demonstrate the superior osteogenetic potential of photo-immobilized BMP-2 using Az-Gel carrier in a rat calvarial defect model compared with control group. Photo-immobilization of BMP-2 using Az-gelatin could be a more effective carrier system of BMP-2 than a chitosan-based carrier system.

Effects of carbon dioxide pneumoperitoneum on postoperative adhesion formation and oxidative stress in a rat cecal abrasion model

INTRODUCTION

It is claimed that CO2 pneumoperitoneum (CP) is less adhesiogenic than laparotomy. Our aim in this study was to investigate the local oxidative stress responses and related adhesion formation resulting from exposure to CP.

METHODS

Forty-five rats were randomised into six groups. Group 1 underwent laparotomy only; in group 2, 6 mmHg CP was performed for 60 min; in group 3, the same procedure was carried out using 12 mmHg CP; in group 4, laparotomy and cecal-peritoneal abrasion were performed; in group 5, 6 mmHg CP was performed for 60 min, followed by laparotomy and cecal-peritoneal abrasion; in group 6, the same procedure was carried out using 12 mmHg CP. Groups 1, 2 and 3 were sacrificed immediately and used only for biochemical examination. The other groups were sacrificed on the 14th postoperative day.

RESULTS

The total adhesion scores, thickness, quantity, extent and type of adhesions decreased steadily in groups 4, 5 and 6 (p < 0.05). The median values for neutrophil and monocyte infiltration, and for capillary and fibroblast proliferation decreased steadily in groups 4, 5 and 6 (p < 0.05). CAT, SOD and GSHPx levels decreased significantly in line with increasing pressure in groups 1, 2 and 3. SOD and GSHPx levels were similar in groups 4, 5 and 6, while CAT levels decreased with increasing pressure in groups 4, 5 and 6.

CONCLUSION

It was found that CP is associated with less adhesion formation than laparotomy in the presence of similar antioxidant levels. The reduced adhesion formation is probably caused by a decreased inflammatory response.

Carboxymethylated chitosan stimulates proliferation of Schwann cells in vitro via the activation of the ERK and Akt signaling pathways

Proliferation of Schwann cell in the injured peripheral nerve supports axonal regeneration and also is critical for the regeneration of injured nerves. In this publication, carboxymethylated chitosan (CMCS) was studied to determine its capacity (i) to induce proliferation and synthesis of proliferating cell nuclear antigen (PCNA) and (ii) to activate mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) and phosphatidylinositil-3 kinase (PI3K)/Akt signaling pathways in rat Schwann cells. CMCS was found to induce proliferation and PCNA synthesis in Schwann cells in a dose and time dependent manner. CMCS was shown to phosphorylate ERK1/2 and Akt in Schwann cell proliferation. The phosphorylation of ERK1/2 and Akt in Schwann cells was blocked by the MEK inhibitor PD98059 and the PI3K inhibitor wortmannin. In addition, inhibition of the MEK/ERK or the PI3K/Akt signaling pathways significantly decreased the proliferative effects of CMCS in Schwann cells. Overall, the above results indicate that CMCS stimulates proliferation of Schwann cells by activating the intracellular signaling cascades of ERK1/2 and PI3K/Akt.

Carbondioxide pneumoperitoneum prevents postoperative adhesion formation in a rat cecal abrasion model

PURPOSE

We aimed to investigate the role of the carbon-dioxide (CO(2)) pneumoperitoneum on the prevention of postoperative adhesion formation.

METHODS

Thirty adult male Sprague-Dawley rats (250-350 g) were used for this study. The rats were randomly divided into three groups; in the sham group (n = 10) only, laparotomy was made, in group 2 (n = 10), a pneumoperitoneum was applied for a half-hour duration, followed by laparatomy, and in group 3 (n = 10), pneumoperitoenum time was 2 hours and after a pneumoperitoneum laparotomy was made. A cecal abrasion model was studied for making an adhesion formation. On day 14, all rats were sacrificed and adhesions were scored. Tissue samples from adhesions and peritonea and the cecum wall were examined, both pathologically and biochemically, for tissue hydroxyproline content.

RESULTS

There was a statistically significant difference between the control and pneumoperitoneum groups, regarding adhesion numbers and grades (P < 0.001). Cecal tissue hydroxypyroline content level was lower in group 1, and statistically significant differences were observed between groups 1, 2, and 3 regarding hydroxyproline content (P < 0.001). There was a statistically significant difference between the control and pneumoperitoneum groups regarding inflammation (P = 0.002).

CONCLUSIONS

Pretreatment with the CO(2) pneumoperitoneum had a prophylactic effect on postoperative adhesion formation in this study.

Synthesis and properties of O-carboxymethyl chitosan/methoxy poly(ethylene glycol) graft copolymers

O-carboxymethyl chitosan/methoxy poly(ethylene glycol) graft copolymers (OCMCS-g-MPEGs) with different degrees of substitution (DS) were synthesized by reductive N-alkylation of chitosan with poly(ethylene glycol) aldehyde. The properties of OCMCS-g-MPEGs, including the solubility, structure, hydrodynamic behaviors, isoelectric point (IEP) and interaction with water-soluble chitosan, were investigated. As a PEGylated polyampholyte, OCMCS-g-MPEGs can resolve in water over all pH range and the pH value at IEP (pH(IEP)) decreases when DS increases. The hydrodynamic behaviors of OCMCS-g-MPEGs in deionized H(2)O are markedly affected by DS and pH(IEP) in the experiment concentration range. The particle size of the complexes of OCMCS-g-MPEGs with water-soluble chitosan is strongly affected by the concentration of water-soluble chitosan and the pH value.

Preparation of carboxymethyl chitosan in aqueous solution under microwave irradiation

Carboxymethyl chitosan was prepared by reacting chitosan with chloroacetic acid in water under microwave irradiation. The effect of the reaction conditions was investigated and optimal conditions were identified. The influence of mass ratio of chloroacetic acid to chitosan, microwave power and pH on the degree of substitution or intrinsic viscosity were further studied. The degree of substitution of the carboxymethyl chitosan synthesized exceeded 0.85.

Reduction of Postoperative Adhesions by N,O-Carboxymethylchitosan and Spermine NONOate in Rats

BACKGROUND

Postsurgical adhesions can occur following virtually all types of surgery, resulting in serious clinical complications. Therefore, prevention of adhesions is an important goal of surgical practice. A rat uterine horn model was used to investigate the efficacy of N,O-carboxymethylchitosan (NOCC) and spermine NONOate (SPER/NO) alone and in combination in preventing adhesion formation.

METHODS

Sixty Wistar albino rats underwent bilateral uterine horn injury with a unipolar cautery. Study groups were as follows: (i) control group, no adjuvant therapy; and those with adjuvant applied, (ii) normal saline group, 2 ml of normal saline was given; (iii) NOCC group, 2 ml of 2% NOCC gel was given; (iv) SPER/NO group, 2 ml of SPER/NO (0.5 mg/ml) was given, and (v) NOCC plus SPER/NO group, 2 ml of 2% NOCC gel including SPER/NO (0.5 mg/ml) was given. After 14 days, all animals were euthanatized, and a standard adhesion scoring system including extent and severity scores was applied by a blinded examiner.

RESULTS

The extent score in NOCC plus SPER/NO group was significantly lower than those of control and normal saline groups (p < 0.05). The extent score in NOCC group was significantly lower than that of normal saline group (p < 0.05). The extent score in NOCC plus SPER/NO group was significantly lower than that of SPER/NO group (p < 0.05). The severity score was significantly lower in NOCC plus SPER/NO and NOCC groups than that of control group (p < 0.05). The severity score was significantly lower in NOCC plus SPER/NO group than that of SPER/NO group (p < 0.05).

CONCLUSIONS

Postoperative administration of NOCC gel and SPER/NO alone and especially in combination to the site of peritoneal injury reduces the formation of adhesions in the rat uterine horn model.

Chitosan and D-glucosamine induce expression of Th1 cytokine genes in porcine spleen cells

Chitosan, a polymer of D-glucosamine, is a polysaccharide derived from the chitin found in the exoskeleton of shellfish, such as shrimp or crabs. The effects of chitosan has been recognized that chitosan-fed farm animals demonstrated higher weight gains but less incidence of diseases than the unfed ones. However, these beneficial effects has not been elucidated clearly. In this study, we examined the modulatory effect of chitosan and D-glucosamine on the expression of porcine cytokines in vitro. Porcine spleen cells were cultured in the presence of chitosan and D-glucosamine, and the effects of chitosan on the cytokine mRNA expression were evaluated. Expressions of IL-2 and IFN-gamma were increased in the chitosan-treated porcine spleen cells. Expressed cytokines in the D-glucosamine-treated cells were IL-2, IFN-gamma, and IL-12 p40 subunit. In particular, IFN-gamma was expressed more efficiently, and D-glucosamine was more effective for expressing the cytokine gene. These results suggest chitosan as well as D-glucosamine could induce the expression of cytokines as Th1 subset such as IL-2, IFN-gamma.

CD4+ T cells regulate surgical and postinfectious adhesion formation

The development of adhesions in the peritoneal and pelvic cavities, which commonly form after surgery or infection, cause significant morbidity and mortality. However, the pathogenesis of adhesion formation is still poorly understood. Because T cells are important in orchestrating fibrinogenic tissue disorders, we hypothesized that they play a critical role in the pathogenesis of peritoneal adhesion formation. Using a cecal abrasion surgical model in rodents, T cell depletion and adoptive transfer experiments demonstrated that this host response is dependent on CD4+ alphabeta T cells. These cells were also critical to adhesion formation associated with experimental intraabdominal sepsis. T cell transfer studies with mice deficient in signal transducer and activator of transcription (Stat)4 and Stat6 revealed that adhesion formation was dependent on a T helper 1 response. Activated T cells homed to the peritoneal cavity 6 hours after cecal abrasion surgery and predominated at this site during adhesiogenesis. Increased levels of the T cell-derived proinflammatory cytokine interleukin (IL)-17 and of neutrophil chemoattractant CXC chemokines macrophage inflammatory protein-2/CXCL8 and cytokine-induced neutrophil chemoattractant/CXCL1 were associated with adhesion formation. The production of these chemokines was dependent on T cells. Furthermore, the administration of neutralizing antibodies specific for IL-17 or the receptor that binds these CXC chemokines, CXC chemokine receptor 2, significantly reduced the degree of adhesion formation. These results demonstrate for the first time that the immunopathogenesis of adhesion formation is under the control of T cells and that T cell-derived cytokines and chemokines play important roles in the development of this deleterious host response.