Stent-induced Tissue Hyperplasia Research Articles

3D-printed versatile biliary stents with nanoengineered surface for anti-hyperplasia and antibiofilm formation

Biliary strictures are characterized by the narrowing of the bile duct lumen, usually caused by surgical biliary injury, cancer, inflammation, and scarring from gallstones. Endoscopic stent placement is a well-established method for the management of biliary strictures. However, maintaining optimal mechanical properties of stents and designing surfaces that can prevent stent-induced tissue hyperplasia and biofilm formation are challenges in the fabrication of biodegradable biliary stents (BBSs) for customized treatment. This study proposes a novel approach to fabricating functionalized polymer BBSs with nanoengineered surfaces using 3D printing. The 3D printed stents, fabricated from bioactive silica poly(ε-carprolactone) (PCL) via a sol–gel method, exhibited tunable mechanical properties suitable for supporting the bile duct while ensuring biocompatibility. Furthermore, a nanoengineered surface layer was successfully created on a sirolimus (SRL)-coated functionalized PCL (fPCL) stent using Zn ion sputtering-based plasma immersion ion implantation (S-PIII) treatment to enhance the performance of the stent. The nanoengineered surface of the SRL-coated fPCL stent effectively reduced bacterial responses and remarkably inhibited fibroblast proliferation and initial burst release of SRL in vitro systems. The physicochemical properties and biological behaviors, including in vitro biocompatibility and in vivo therapeutic efficacy in the rabbit bile duct, of the Zn-SRL@fPCL stent demonstrated its potential as a versatile platform for clinical applications in bile duct tissue engineering.

Radiofrequency ablation via an implanted self-expandable metallic stent to treat in-stent restenosis in a rat gastric outlet obstruction model.

Background: In-stent restenosis caused by tissue hyperplasia and tumor growth through the wire meshes of an implanted self-expandable metallic stent (SEMS) remains an unresolved obstacle. This study aimed to investigate the safety and efficacy of SEMS-mediated radiofrequency ablation (RFA) for treating stent-induced tissue hyperplasia in a rat gastric outlet obstruction model. Methods: The ablation zone was investigated using extracted porcine liver according to the ablation time. The optimal RFA parameters were evaluated in the dissected rat gastric outlet. We allocated 40 male rats to four groups of 10 rats as follows: group A, SEMS placement only; group B, SEMS-mediated RFA at 4 weeks; group C, SEMS-mediated RFA at 4 weeks and housed until 8 weeks; and group D, SEMS-mediated RFA at 4 and 8 weeks. Endoscopy and fluoroscopy for in vivo imaging and histological and immunohistochemical analysis were performed to compare experimental groups. Results: Stent placement and SEMS-mediated RFA with an optimized RFA parameter were technically successful in all groups. Granulation tissue formation-related variables were significantly higher in group A than in groups B-D (all p < 0.05). Endoscopic and histological findings confirmed that the degrees of stent-induced tissue hyperplasia in group D were significantly lower than in groups B and C (all p < 0.05). Hsp70 and TUNEL expressions were significantly higher in groups B-D than in group A (all p < 0.001). Conclusion: The implanted SEMS-mediated RFA successfully managed stent-induced tissue hyperplasia, and repeated or periodic RFA seems to be more effective in treating in-stent restenosis in a rat gastric outlet obstruction model.

Infigratinib, a Selective Fibroblast Growth Factor Receptor Inhibitor, Suppresses Stent-Induced Tissue Hyperplasia in a Rat Esophageal Model.

Stent-induced tissue hyperplasia remains a challenge for the application of self-expanding metal stents in the management of esophageal stricture. This study aimed to evaluate the efficacy of infigratinib, which is a selective fibroblast growth factor receptor inhibitor, in the prevention of stent-induced tissue hyperplasia in a rat esophageal model. Twenty-four male Sprague-Dawley rats underwent esophageal stent placement and were randomized to receive 1ml of vehicle, 5mg/kg infigratinib in 1ml of vehicle, or 10mg/kg infigratinib in 1ml of vehicle via naso-gastric tube once daily for 28days. Follow-up fluoroscopy was performed on postoperative day 28, and the stented esophageal tissues were harvested for histological and immunofluorescence examinations. All rats survived until euthanasia on postoperative day 28 without procedure-related adverse events. The incidence of stent migration was 12.5%, 12.5% and 25% in the control group, the 5mg/kg infigratinib group and, the 10mg/kg infigratinib group, respectively. The percentage of granulation tissue area, the submucosal fibrosis thickness, the number of epithelial layers, the degree of inflammatory cell infiltration, the degree of collagen deposition, the number of fibroblast growth factor receptor 1 (FGFR1)-expressing myofibroblasts, and the number of proliferating myofibroblasts were all significantly lower in both infigratinib groups than in the control group (P < 0.05) but were not significantly different between the two infigratinib groups (P > 0.05). Infigratinib significantly suppresses stent-induced tissue hyperplasia by inhibiting FGFR1-mediated myofibroblast proliferation and profibrotic activities in a rat esophageal model.

Preliminary results of absorbable magnesium stent for treating eustachian tube dysfunction in a porcine model.

Absorbable magnesium (Mg) stents have an attractive biocompatibility and rapid degradation rate, but their degradable behavior and efficacy in the Eustachian tube (ET) have not yet been investigated. In this study, the degradable behavior of the Mg stent in artificial nasal mucus was evaluated. The Mg stents in the porcine ET model were also investigated to evaluate their safety and efficacy. Four Mg stents were placed into the four ETs of two pigs. The mass loss rate of the Mg stents gradually decreased over time. The decrease rates were 30.96% at one week, 49.00% at two weeks, and 71.80% at four weeks. On the basis of histological findings, the thickness of submucosal tissue hyperplasia and the degree of inflammatory cell infiltration significantly decreased at four weeks compared with two weeks. Biodegradation of the Mg stent occurred before tissue proliferative reactions, and the ET patency was successfully maintained without stent-induced tissue hyperplasia at four weeks. The Mg stent that biodegrades rapidly seems to be effective and safe in porcine ET. Further investigation is required to verify the optimal stent shape and indwell period in the ET.

Tapered self-expandable metallic stent optimized for Eustachian tube morphology in a porcine ET model

Several investigations on the feasibility of stent placement into the Eustachian tube (ET) are being conducted. However, stents optimized for the anatomical structure of the ET have not yet been developed. In this study, the efficacy and safety of a self-expandable metallic stent (SEMS) optimized for porcine ET morphology was investigated. Silicone was injected into a cadaveric porcine ET to analyze the ET morphology. The three-dimensional-reconstructed porcine ET phantom images obtained after a computed tomography scan were measured to determine the dimensions of the porcine ET. The SEMS was designed as a tapered structure on the basis of the morphological findings of the porcine ET. The tapered SEMS (T-SEMS) and conventional SEMS (C-SEMS) were placed into the porcine ET to compare the safety and efficacy of the two types of SEMSs. Stent-induced tissue hyperplasia in the T-SEMS group was significantly lower than that in the C-SEMS group (p < 0.001). The T-SEMS optimized for the porcine ET was effective in maintaining stent patency. T-SEMS seems to be better than C-SEMS in suppressing stent-induced tissue hyperplasia, owing to the reduced stent-mediated mechanical injuries and maintaining ET patency.

Flexible 3D Nanonetworked Silica Film as a Polymer‐Free Drug‐Eluting Stent Platform to Effectively Suppress Tissue Hyperplasia in Rat Esophagus (Adv. Healthcare Mater. 14/2022)

Nanonetworked Films In article number 2200389 by Wooram Park, Jung-Hoon Park, Joonseok Lee, and co-workers, a large scale 3D nanonetworked silica film (NSF) is constructed on an entire metallic stent surface to function as a drug delivery platform, which shows excellent mechanical stability, flexibility, and adhesion. The NSF with an antiproliferative agent allows in vivo drastic suppression of stentinduced tissue hyperplasia and restenosis.

Flexible 3D Nanonetworked Silica Film as a Polymer-Free Drug-Eluting Stent Platform to Effectively Suppress Tissue Hyperplasia in Rat Esophagus.

Loading and eluting drugs on self-expandable metallic stents (SEMSs) can be challenging in terms of fabrication, mechanical stability, and therapeutic effects. In this study, a flexible 3D nanonetworked silica film (NSF) capable of withstanding mechanical stress during dynamic expansion is constructed to function as a drug delivery platform on an entire SEMS surface. Despite covering a broad curved area, the synthesized NSF is defect-free and thin enough to increase the stent strut diameter (110µm) by only 0.4 percent (110.45µm). The hydrophobic modification of the surface enables loading of 4.7 times the sirolimus (SRL) concentration in NSF than Cypher, polymer-coated commercial stent, which is based on the same thickness of coating layer. Furthermore, SRL-loaded NSF exhibits a twofold delay in release compared to the control group without NSF. The SRL-loaded NSF SEMS significantly suppresses stent-induced tissue hyperplasia than the control SEMS in the rat esophagus (all variables, p <0.05). Thus, the developed NSF is a promising polymer-free drug delivery platform to efficiently treat esophageal stricture.

Sirolimus-eluting cobalt\u2013chrome alloy stent suppresses stent-induced tissue hyperplasia in a porcine Eustachian tube model

Various preclinical studies with developed Eustachian tube (ET) stents are in progress but have not yet been clinically applied. ET stent is limited by stent-induced tissue hyperplasia in preclinical studies. The effectiveness of sirolimus-eluting cobalt–chrome alloy stent (SES) in suppressing stent-induced tissue hyperplasia after stent placement in the porcine ET model was investigated. Six pigs were divided into two groups (i.e., the control and the SES groups) with three pigs for each group. The control group received an uncoated cobalt–chrome alloy stent (n = 6), and the SES group received a sirolimus-eluting cobalt–chrome alloy stent (n = 6). All groups were sacrificed 4 weeks after stent placement. Stent placement was successful in all ETs without procedure-related complications. None of the stents was able to keep its round shape as original, and mucus accumulation was observed inside and around the stent in both groups. On histologic analysis, the tissue hyperplasia area and the thickness of submucosal fibrosis were significantly lower in the SES group than in the control group. SES seems to be effective in suppressing stent-induced tissue hyperplasia in porcine ET. However, further investigation was required to verify the optimal stent materials and antiproliferative drugs.

Silver Nanofunctionalized Stent after Radiofrequency Ablation Suppresses Tissue Hyperplasia and Bacterial Growth.

Intraductal radiofrequency (RF) ablation combined with placement of a self-expandable metal stent (SEMS) for malignant biliary obstruction has risks such as stent- and heat-induced biliary sludge and restenosis. Here, we investigated the efficacy of a silver nanoparticles (AgNPs)-coated SEMS to inhibit tissue hyperplasia and bacterial growth caused by RF ablation with stent placement in the rabbit bile duct. The release behavior and antibacterial effects of AgNPs-coated SEMSs were evaluated. Then, SEMSs were successfully placed in all rabbits immediately after RF ablation. Ag ions were rapidly released at the beginning and then showed a gradual release behavior. The AgNPs-coated SEMS significantly inhibited bacterial activity compared to the uncoated SEMS (p < 0.05). Cholangiography and histological examination confirmed that the level of tissue hyperplasia was significantly lower in the AgNPs group than in the control group (all p < 0.05). Immunohistochemistry analyses revealed that TUNEL-, HSP 70-, and α-SMA-positive areas were significantly lower in the AgNPs group than in the control group (all p < 0.05). Intraductal RF ablation combined with nanofunctionalized stent placement represents a promising new approach for suppressing thermal damage as well as stent-induced tissue hyperplasia and bacterial growth.

Interwoven versus Knitted Self-Expandable Metallic Stents: A Comparison Study of Stent-Induced Tissue Hyperplasia in the Rat Esophagus

This study investigated whether interwoven self-expandable metallic stent (I-SEMS) placement suppresses stent-induced tissue hyperplasia compared with conventional knitted self-expandable metallic stent (K-SEMS) placement in a rat esophageal model. Twelve rats were randomly assigned to the I-SEMS (n = 6) and K-SEMS (n = 6) groups. All rats were sacrificed 4 weeks after the stent placement. The degree of stent-induced tissue hyperplasia on esophagography and histologic examination was compared between the groups. Stent placement was technically successful in all rats. Esophagography revealed significantly greater mean luminal diameter of the stented esophagus in the I-SEMS group than in the K-SEMS group (p &lt; 0.001). Histologic examination revealed a significantly lower percentage of tissue hyperplasia area and a significantly thinner submucosal fibrosis in the I-SEMS group than in the K-SEMS group (all p &lt; 0.001). There were no significant differences in the thickness of the epithelial layers (p = 0.290) and degree of inflammatory cell infiltration (p = 0.506). Formation of stent-induced tissue hyperplasia was evident with both I-SEMS and K-SEMS. Placement of I-SEMSs with a small cell size and high flexibility seems to be effective in suppressing stent-induced tissue hyperplasia compared with placement of K-SEMSs in rat esophageal models.

Comparison of three kinds of self-expandable metallic stents induced granulation tissue hyperplasia in the rabbit trachea

To compare stent-induced granulation tissue hyperplasia of bare (SEMS), polyurethane-covered (PU-SEMS) and electrospun nanofibre-covered (EN-SEMS) self-expandable metallic stents in the rabbit trachea. Twenty-seven rabbits were randomly assigned to 3 groups that received SEMS, PU-SEMS or EN-SEMS. Computed tomography and sacrifice were performed as scheduled. Haematoxylin–eosin and Masson’s trichrome staining protocols were performed for pathological analysis. The data for tracheal ventilation area ratio, qualitative histological scoring, number of epithelial layers, and thicknesses of papillary projection and submucosa were documented and statistically analysed. All stents were successfully placed under the guidance of fluoroscopy without complications. Post-stenting 3 and 7 days, computed tomography revealed that the fully expandable EN-SEMS was similar to the SEMS and PU-SEMS. The mean stented tissue score in the SEMS group was higher than those of both the PU-SEMS and EN-SEMS groups at 3 days post-stenting. The pathological findings suggested that there was no papillary projection formation 3 days after stent placement. The thickness of papillary projection in the SEMS group was significantly higher than those of the PU-SEMS and EN-SEMS groups at 7 days post-stenting. After stenting 4 weeks, the tracheal ventilation area ratio of SEMS, PU-SEMS and EN-SEMS was 0.214 ± 0.021, 0.453 ± 0.028 and 0.619 ± 0.033, respectively. There were significant between-group differences. In conclusion, the stent-induced granulation tissue formation in EN-SEMS is less severe than that of PU-SEMS and SEMS. EN-SEMS has smaller radial force, and the tracheal ventilation ratio after stent placement better than that of PU-SEMS.

Technical Feasibility and Histological Analysis of Balloon-Expandable Metallic Stent Placement in a Porcine Eustachian Tube

There is a clinical need to develop a stent to treat obstructive and refractory Eustachian tube dysfunction (ETD) after balloon Eustachian tuboplasty. An animal model for stent placement in the Eustachian tube (ET) is needed to develop optimal designs and materials, as stents for ETD have not been clinically applied. The purpose of this study was to evaluate the technical feasibility of stent placement and histological changes in a porcine ET model. Six ETs were evaluated in three pigs. Cobalt–chrome alloy stents with two different diameters were placed in the left and right ET of each animal (right, 3.5 mm; left, 2.5 mm). The outcomes were assessed by endoscopic and fluoroscopic imaging during the procedure, computed tomography after the procedure, and by histological examinations. Stent placement was technically successful in all specimens after metallic guiding sheaths were located in the nasopharyngeal end of the ET. The mean luminal diameters of the proximal, middle, and distal portions of the larger stents in the right ETs were 3.48 mm, 2.54 mm, and 2.15 mm, respectively. In the left ETs using smaller stents, these values were 2.49 mm, 1.73 mm, and 1.42 mm, respectively. The diameters of the inserted stents differed by stent location and the original diameter. Histological findings showed tissue hyperplasia with severe inflammatory cell infiltration at 4 weeks after stent placement. In conclusion, stent placement into the porcine ET was technically feasible, and stent-induced tissue hyperplasia was significantly evident. The luminal configuration of the placed ET stent changed according to its non-elastic nature and anatomical features of the porcine ET. Using this model, ET stents of various materials and designs with anti-inflammatory or anti-proliferative drugs can be optimized for future treatments of ET dysfunction.

A Mouse Colon Model to Investigate Stent-Induced Tissue Hyperplasia

A Mouse Colon Model to Investigate Stent-Induced Tissue Hyperplasia

Metallic Stent Mesh Coated with Silver Nanoparticles Suppresses Stent-Induced Tissue Hyperplasia and Biliary Sludge in the Rabbit Extrahepatic Bile Duct.

Recent therapeutic strategies to suppress restenosis after biliary stent placement are insufficient. Here, we demonstrate the usefulness of a self-expandable metal stent (SEMS), a stent mesh coated with silver nanoparticles (AgNPs), for suppression of both stent-induced tissue hyperplasia and biliary sludge formation in the rabbit bile duct. The AgNP-coated SEMSs were prepared using a simple bio-inspired surface modification process. Then, the prepared SEMSs were successfully placed in 22 of 24 rabbits. Sludge formation in the AgNP-coated SEMS groups was significantly decreased compared to the control group on gross findings. Cholangiographic and histologic examinations demonstrated significantly decreased tissue hyperplasia in the AgNP-coated SEMS groups compared with the control group (p < 0.05 for all). There were no differences between the AgNP-coated SEMS groups (p > 0.05 for all). However, in the group coated with the greatest concentration of AgNPs (Group D), submucosal fibrosis was thicker than in the other AgNP-coated groups (p < 0.05 for all). The AgNP-coated metallic stent mesh significantly suppressed stent-induced tissue hyperplasia and biliary sludge formation in the rabbit bile duct. Taken together, the AgNP coating strategy developed in this study could be widely utilized in non-vascular medical devices for anti-bacterial and anti-inflammatory responses.

Local Heat Treatment for Suppressing Gastroduodenal Stent-Induced Tissue Hyperplasia Using Nanofunctionalized Self-Expandable Metallic Stent in Rat Gastric Outlet Model.

Despite the promising results from the placement of covered or uncovered self-expandable metallic stent (SEMS) as a nonsurgical therapeutic option for the malignant gastric outlet obstruction (GOO), the long patency of the stent is still limited because of stent-induced tissue hyperplasia. Here, a local heat treatment using a nanofunctionalized SEMS is proposed for suppressing stent-induced tissue hyperplasia during GOO treatment. Highly efficient photothermal gold nanoparticle (GNP) transducer-coated SEMSs (GNP-SEMSs) were prepared for local heat treatment in rat gastric outlet. The in vivo heating temperature in rat gastric outlet model was evaluated and compared with in vitro heating temperature. Three groups of our developed 45 rat gastric outlet models were used: group A, noncoated SEMS only; group B, GNP-SEMS plus local heating; and group C, GNP-SEMS only to investigate in vivo efficacy of GNP-SEMS mediated local heating. Ten rats per group were sacrificed for 4 weeks, and five rats per group were sacrificed immediately after local heat treatment. The in vivo heating temperature was found to be 10.8% lower than the in vitro heating temperatures. GNP-SEMSs were successfully placed through a percutaneous approach into the rat gastric outlet (n = 45). The therapeutic effects of GNP-SEMS were assessed by histologic examination including hematoxylin-eosin, Masson trichrome, immunohistochemistry (TUNEL and CD31), and immunofluorescence (Ki67), and the results showed significant prevention of tissue hyperplasia following stent placement without adjacent gastrointestinal tissue damage. GNP-SEMS-mediated local heating could be an alternative therapeutic option for the suppression of tissue hyperplasia following stent placement in benign and malignant GOOs.

Abstract No. 578 Ag nano-functionalized self-expandable metallic stent suppresses biliary sludge and stent-induced tissue hyperplasia in rabbit extrahepatic bile duct

Abstract No. 578 Ag nano-functionalized self-expandable metallic stent suppresses biliary sludge and stent-induced tissue hyperplasia in rabbit extrahepatic bile duct

Balloon-Expandable Biodegradable Stents Versus Self-Expandable Metallic Stents: A Comparison Study of Stent-Induced Tissue Hyperplasia in the Rat Urethra

To compare the degrees of stent-induced tissue hyperplasia of balloon-expandable, biodegradable stents (BEBSs) with those of self-expandable metallic stents (SEMSs) in a rat urethral model. A total of 20 rats were randomized into two groups. The BEBS group (n = 10) received a poly-l-lactic acid (PLLA) biodegradable stent. The SEMS group (n = 10) received a nitinol bare stent. All rats were killed eight weeks after stent placement. The degree of stent-induced tissue hyperplasia was assessed by comparing the results of retrograde urethrography and histologic examination between the two groups. Stent placement was technically successful in all rats. Two rats in the BEBS group were excluded due to procedure-related death. The mean luminal diameter of stented urethra on urethrograms was not significantly different at 4 and 8 weeks between the two groups. On histologic analysis, the percentage of granulation tissue area (p < 0.001) and the thickness of papillary projection (p < 0.001) were significantly higher in the BEBS group compared with the SEMS group. The inflammatory cell infiltration showed a clear tendency to significance (p = 0.050). There were no statistical differences in the number of epithelial layers and the thickness of submucosal fibrosis between the two groups. Formation of stent-induced tissue hyperplasia was significantly evident in the rat urethra with similar degrees between the BEBS and the SEMS. The BEBS was associated with a thicker papillary projection and larger granulation tissue area resulting from higher inflammation compared with the SEMS.

Therapeutic effect of a temporary transpyloric stent in refractory post-surgical gastroparesis: a case report

BackgroundGastroparesis is a syndrome characterized by delayed gastric emptying with associated symptoms. It was reported that the symptoms of diabetic gastroparesis had been greatly improved by transpyloric stent placement. However, the use of stents in benign conditions is considered to be contraindicated because of the increasing risk of complications, such as stent migration, reflux, perforation, bleeding, and, most importantly, new strictures caused by stent-induced tissue hyperplasia. While temporary placement of a self-expanding metallic stent (SEMC) can drastically reduce the risk of complications, few reports are available on the treatment of refractory PSG by temporary transpyloric stent. Does it have a long-term clinical effect after the stent being retrieved?Case presentationAfter accepting partial resection of the lesser curvature in another hospital, a patient developed refractory gastroparesis. The symptoms hadn’t been improved after long-term drug therapy and balloon dilation therapy. Four months after surgery, a fully covered SEMC was placed by endoscopy in our hospital. Gastroparesis had been greatly improved. Two weeks later, the transpyloric stent was retrieved and the patient didn’t show recurrent symptoms. Follow-ups were arranged at 3 months, 6 months and 1 year respectively, and there was no evidence of recurrence was found.ConclusionsThis case indicates that temporary transpyloric SEMC is a safe, effective and less invasive alternative for post-surgical gastroparesis patients.

Nanofunctionalized Stent-Mediated Local Heat Treatment for the Suppression of Stent-Induced Tissue Hyperplasia.

Current therapeutic strategies are insufficient for suppressing stent-induced restenosis. Here, branched gold nanoparticles (BGNP)-coated self-expandable metallic stents (SEMSs) were developed for a local heat-induced suppression of stent-related tissue hyperplasia. Our polydopamine (PDA) coating on SEMS allowed BGNP crystal growth on the surface of SEMSs. The prepared BGNP-coated SEMS showed effective local heating under near-infrared laser irradiation. The effectiveness of BGNP-coated SEMSs for suppressing stent-related tissue hyperplasia was demonstrated in a rat esophageal model ( n = 52). BGNP-coated SEMS placement under fluoroscopic guidance was technically successful in all rats. The placed BGNP-coated SEMS in rat esophagus achieved three different local heat dose ranges (50, 65, and 80 °C) under fluoroscopic image-guided local irradiation. Follow-up endoscopic examination readily monitored the local heating and observed significantly decreased tissue hyperplasia at 4 weeks of local heat treatments (50 and 65 °C). Finally, Western blot, histology, immunohistochemistry (HSP70, αSMA, and TUNEL), and immunofluorescence (Ki67 and BrdU) analyses along with the statistical analysis confirmed that optimized BGNP-coated SEMS-mediated local heat treatments inducing the expression of anti-inflammatory HSP70 effectively suppresses tissue hyperplasia after stent placement in the esophagus. Our local heating with nanofunctionalized stents represents a promising new approach for suppressing stent-related tissue hyperplasia.

MMP-9 Expression after Metallic Stent Placement in Patients with Colorectal Cancer: Association with In-Stent Restenosis

To verify the expression of matrix metalloproteinase (MMP)-9 in stent-induced hyperplastic tissue from patients with colorectal cancer who received colorectal stents as a bridge to surgery. This prospective study was institutional review board-approved, and informed consent was obtained from all patients. Eleven patients (nine men, two women; mean age, 67 years; age range, 53-82 years) with malignant colorectal obstructions who received a colorectal stent between May and December 2010 were included. Tissue specimens were analyzed for MMP-9 and MMP-2 expression. After resection, the tissue was segmented into three parts: tumor tissue, stent-induced tissue hyperplasia, and normal colon tissue. MMP-9 and MMP-2 expression were determined by using zymography, Western blot analysis, and real-time reverse-transcription (qRT) polymerase chain reaction (PCR). Significance of differences between groups was evaluated with Friedman analysis of variance test. Signed-rank test was used to determine differences between malignant tumor tissue and stent-induced hyperplastic tissue groups. Stent placement was technically successful in all 11 patients. Stent-induced hyperplastic tissues were found in all patients. Zymography (P = .003) and Western blot analysis (P = .008) showed that expression of MMP-9 was higher in malignant tumor tissue and stent-induced hyperplastic tissue groups compared with normal colorectal tissue group, demonstrating significant differences between groups but no significant differences between malignant tumor and stent-induced hyperplastic tissues. As for results of qRT PCR analysis, the stent-induced hyperplastic tissue group showed increases in messenger RNA expression level of MMP-9 compared with the malignant tumor tissue group (50.42-fold ± 66.30 higher). High expression of MMP-9 is closely associated with stent-induced colorectal tissue hyperplasia in patients with colorectal cancer.