Use of adipose tissue-derived stromal cells for prevention of esophageal stricture after circumferential EMR in a canine model

PRP improves the outcomes of autologous skin graft transplantation on the esophagus by promoting angiogenesis and inhibiting fibrosis and inflammation

Background and Objectives

Autologous skin graft (ASG) transplantation is a challenging approach but a promising option for patients to prevent postoperative esophageal stricture. Nonetheless, the current strategies require improvement. We aimed to investigate the effectiveness of the injection of platelet-rich plasma (PRP) before skin graft transplantation for extensive esophageal defects after endoscopic resection.

Methods

Standardized complete circular endoscopic resection (5 cm in length) was performed in 27 pigs allocated into 3 groups. The artificial ulcers were treated with a fully covered esophageal stent (control group), ASG (ASG group), and submucosal injection of PRP with ASG (PRP-ASG group). Macroscopic evaluation and histological analysis of the remolded esophagus were performed 7, 14, and 28 days after surgery.

Results

The macroscopic evaluation indicated that submucosal injection of PRP before transplantation effectively promoted the survival rate of skin grafts and decreased the rate of mucosal contraction compared with those treated with ASG or stent alone. Histological analysis of submucosal tissue showed that this modified strategy significantly promoted wound healing of reconstructed tissues by enhancing angiogenesis, facilitating collagen deposition, and decreasing inflammation and fibrogenesis.

Conclusions

These findings suggested that PRP might be used as a biological supplement to increase the esophageal skin graft survival rate and improve submucosal tissue remolding in a clinically relevant porcine model. With extremely low mucosal contraction, this novel combination strategy showed the potential to effectively prevent stenosis in extensive esophageal ulcers.

A Novel Rat Model to Simulate the Benign Esophageal Stricture Induced by Endoscopic Submucosal Dissection

Objective

This study aimed to establish a rat model that simulates benign esophageal strictures induced by endoscopic submucosal dissection (ESD).

Materials and Methods

Sixteen male Sprague-Dawley rats were randomly divided into mucosal resection (n = 8) and sham-operated groups (n = 8). The rats in the mucosal resection group underwent a 5-mm three-fourths mucosal resection by way of a 3-mm incision in the distal esophagus under direct visualization via laparotomy. Rats in the sham-operated group underwent a 3-mm incision of the muscularis propria layer in the distal esophagus via laparotomy without mucosal resection. Dysphagia score, weight gain, mucosal constriction rate, and histology were evaluated 2 weeks after surgery.

Results

Technical success was achieved in all the animals. One rat in the mucosal resection group died of infection, and no other complications were observed. Weight gain (P < 0.001) and luminal diameter derived from the esophagograms (P < 0.001) were significantly lower in the mucosal resection group than those in the sham-operated group. Dysphagia score (P < 0.001) and mucosal constriction rate (P < 0.001) were significantly higher in the mucosal resection group than those in the sham-operated group. The inflammation grade (P = 0.002), damage to the muscularis propria (P < 0.001), number of nascent microvessels (P = 0.006), and degree of α-SMA positive deposition (P = 0.006) were significantly higher in the mucosal resection group.

Conclusion

A rat model of benign esophageal stricture induced by ESD was successfully and safely established by mucosal resection.

The occurrence and development mechanisms of esophageal stricture: state of the art review

BACKGROUND

Esophageal strictures significantly impair patient quality of life and present a therapeutic challenge, particularly due to the high recurrence post-ESD/EMR. Current treatments manage symptoms rather than addressing the disease's etiology. This review concentrates on the mechanisms of esophageal stricture formation and recurrence, seeking to highlight areas for potential therapeutic intervention.

METHODS

A literature search was conducted through PUBMED using search terms: esophageal stricture, mucosal resection, submucosal dissection. Relevant articles were identified through manual review with reference lists reviewed for additional articles.

RESULTS

Preclinical studies and data from animal studies suggest that the mechanisms that may lead to esophageal stricture include overdifferentiation of fibroblasts, inflammatory response that is not healed in time, impaired epithelial barrier function, and multimethod factors leading to it. Dysfunction of the epithelial barrier may be the initiating mechanism for esophageal stricture. Achieving perfect in-epithelialization by tissue-engineered fabrication of cell patches has been shown to be effective in the treatment and prevention of esophageal strictures.

CONCLUSION

The development of esophageal stricture involves three stages: structural damage to the esophageal epithelial barrier (EEB), chronic inflammation, and severe fibrosis, in which dysfunction or damage to the EEB is the initiating mechanism leading to esophageal stricture. Re-epithelialization is essential for the treatment and prevention of esophageal stricture. This information will help clinicians or scientists to develop effective techniques to treat esophageal stricture in the future.

Application of polyglycolic acid sheets and basic fibroblast growth factor to prevent esophageal stricture after endoscopic submucosal dissection in pigs

BACKGROUND

Endoscopic submucosal dissection (ESD) has been the first-line treatment for early-stage esophageal cancer. However, it often causes postoperative stricture in cases requiring wide dissection. Basic fibroblast growth factor (bFGF) reportedly has anti-scarring effects during cutaneous wound healing. We hypothesized that suppressing myofibroblast activation will prevent stricture after esophageal ESD.

METHODS

We resected a complete porcine esophagus circumference section by ESD. To investigate the preventive effect of bFGF on esophageal stricture formation after ESD, we endoscopically applied bFGF-soaked poly-glycolic acid (PGA) sheets onto the wound bed after ESD and fixed them by spraying fibrin glue (PGA + bFGF group), PGA sheets alone onto the wound bed and fixed them by spraying fibrin glue (PGA group), or nothing (control group). After removing the esophagus on day 22, we evaluated the mucosal constriction rate.

RESULTS

Compared with those in the control group, esophageal stricture was significantly reduced in the PGA + bFGF group, and the areas stained with α-SMA and calponin-1 antibodies were significantly inhibited in the PGA + bFGF and PGA groups. The thickness of the fibrous layer in the PGA + bFGF group was uniform compared to that of the other groups. Thus, PGA + bFGF inhibited the development of unregulated fibroblasts in the acute phase, leading to uniform wound healing.

CONCLUSIONS

Stenosis after esophageal ESD is related to fibrosis in the acute phase. Administration of PGA and bFGF suppresses myofibroblast activation in the acute phase, thereby preventing esophageal constriction in pigs.

Prevention of esophageal stenosis via in situ cross-linkable alginate/gelatin powder in a new submucosal exfoliation model in rats

Endoscopic submucosal dissection (ESD) for the treatment of esophageal mucosal lesions often leads to postoperative stenosis, causing difficulty in swallowing, known as dysphagia. In this study, we developed an in situ cross-linkable powder composed of alginate, gelatin, transglutaminase (TG), and calcium chloride ions (Ca2+), which can be administered through a 1.5 m-long and 3.2 mm-diameter endoscopic instrument channel. The powdered mixture of alginate and gelatin quickly formed a hydrogel by absorbing body fluids and was cross-linked by TG and Ca2+, which adhered ex vivo to porcine submucosal layers for over 2 weeks. In addition, we developed a new submucosal exfoliation model in rats that induced severe stenosis, similar to the ESD-induced stenosis models in clinical practice. When administered to the new rat model, the powder system effectively reduced the severity of esophageal stenosis based on body weight change monitoring, anatomical findings, and histological analysis. The body weight of the rats was maintained at the initial weight on postoperative day 14 (POD14), and epithelialization on POD7 and 14 improved to almost 100%. Additionally, collagen accumulation and the number of α-SMA-positive cells decreased due to powder administration. Therefore, these findings indicate that the in situ cross-linkable powder can prevent esophageal stenosis after ESD.

Benign esophageal stricture model construction and mechanism exploration

Esophageal stricture is a debilitating condition that negatively impacts patients' quality of life after undergoing endoscopic mucosal resection (EMR). Despite its significance, this disease remains underexplored due to the lack of a stable animal model. Under direct visualization with choledochoscopy, we retrogradely damaged the esophageal mucosal layer through the gastrostomy to create a rat model of esophageal stricture. The development of histological defects in the mucosal layer was assessed over a 2-week period after model induction. Then the models were evaluated using X-ray barium radiography, Hematoxylin-Eosin, Masson's trichrome, Sirius red, and Victoria blue staining, multiphoton microscopic imaging. Additionally, the molecular mechanisms of esophageal stricture were explored by conducting RNA transcriptome sequencing, PCR, immunohistochemistry, and immunofluorescence staining. We successfully established fifteen rat models of esophageal stricture by injuring the mucosal layer. In the model group, the mucosal defect initially occurs and subsequently repaired. The epithelium was absent and was plastically remodeled by collagen during the acute inflammatory phase (Day 1), proliferation phase (Day 7), anaphase of proliferation (Day 10), and plastic remodeling phase (Day 14). We observed increased expression of COL1A1, acta2, FGF, IL-1, and TGF-β1 pathway in the model group. We established a highly repeatable rat model of esophageal stricture, and our results suggest that the mucosal defect of the esophagus is a critical factor in esophageal stricture development, rather than damage to the muscularis layer. We identified Atp4b, cyp1a2, and gstk1 as potential targets for treating esophageal stricture, while the TGF-β pathway was found to play an important role in its development.

Endoscopically injectable and self-crosslinkable hydrogel-mediated stem cell transplantation for alleviating esophageal stricture after endoscopic submucosal dissection

Esophageal stricture after extensive endoscopic submucosal dissection impairs the quality of life of patients with superficial esophageal carcinoma. Beyond the limitations of conventional treatments including endoscopic balloon dilatation and the application of oral/topical corticosteroids, several cell therapies have been recently attempted. However, such methods are still limited in clinical situations and existing setups, and the efficacies are less in some cases since the transplanted cells hardly remain at the resection site for a long time due to swallowing and peristalsis of the esophagus. Thus, a cell transplantation platform directly applicable with clinically established equipment and enabling stable retention of transplanted cells can be a promising therapeutic option for better clinical outcomes. Inspired by ascidians that rapidly self-regenerate, this study demonstrates endoscopically injectable and self-crosslinkable hyaluronate that allows both endoscopic injection in a liquid state and self-crosslinking as an in situ-forming scaffold for stem cell therapy. The pre-gel solution may compatibly be applied with endoscopic tubes and needles of small diameters, based on the improved injectability compared to the previously reported endoscopically injectable hydrogel system. The hydrogel can be formed via self-crosslinking under in vivo oxidative environment, while also exhibiting superior biocompatibility. Finally, the mixture containing adipose-derived stem cells and the hydrogel can significantly alleviate esophageal stricture after endoscopic submucosal dissection (75% of circumference, 5 cm in length) in a porcine model through paracrine effects of the stem cell in the hydrogel, which modulate regenerative processes. The stricture rates on Day 21 were 79.5% ± 2.0%, 62.8% ± 1.7%, and 37.9% ± 2.9% in the control, stem cell only, and stem cell-hydrogel groups, respectively (p < 0.05). Therefore, this endoscopically injectable hydrogel-based therapeutic cell delivery system can serve as a promising platform for cell therapies in various clinically relevant situations.

A novel tetra-PEG based hydrogel for prevention of esophageal stricture after ESD in a porcine model

Endoscopic submucosal dissection (ESD) is an accepted treatment for early esophageal cancer and precancerous lesions, but resection of a large mucosal area often leads to postoperative esophageal stricture. Biomaterials provide a new option for the treatment of post-ESD ulcers. In this study, we developed a well-defined ammonolysis-based tetra-armed poly (ethylene glycol) (Tetra-PEG) hydrogel and investigated its efficacy and related mechanisms for preventing esophageal ESD-induced stricture in a porcine model. In terms of material properties, Tetra-PEG hydrogel present great biocompatibility，great capability to retain moisture, strong tissue adhesion and high mechanical strength. Then, six domestic female pigs were randomly divided into PEG (n = 3) and control groups (n = 3). A 3/4 of the esophageal circumference ESD was performed in all pigs. In PEG group, Tetra-PEG hydrogel was easily delivered via endoscopy and adhered to the ulcer bed tightly. Compared to control group, Tetra-PEG hydrogel accelerated esophageal ulcer healing at an early stage with enhanced epithelium regeneration, milder inflammation and lesser fibrosis by regulating TGF-β/Smad2 signaling. Taken together, our findings reveal Tetra-PEG hydrogel is a promising and attractive candidate for preventing the formation of fibrotic stricture in the process of esophageal ESD-induced ulcer repair.

Tissue Engineering for Gastrointestinal and Genitourinary Tracts

The gastrointestinal and genitourinary tracts share several similarities. Primarily, these tissues are composed of hollow structures lined by an epithelium through which materials need to flow with the help of peristalsis brought by muscle contraction. In the case of the gastrointestinal tract, solid or liquid food must circulate to be digested and absorbed and the waste products eliminated. In the case of the urinary tract, the urine produced by the kidneys must flow to the bladder, where it is stored until its elimination from the body. Finally, in the case of the vagina, it must allow the evacuation of blood during menstruation, accommodate the male sexual organ during coitus, and is the natural way to birth a child. The present review describes the anatomy, pathologies, and treatments of such organs, emphasizing tissue engineering strategies.

Allogeneic transplantation of epidermal cell sheets followed by endoscopic submucosal dissection to prevent severe esophageal stricture in a porcine model

Introduction

Endoscopic submucosal dissection (ESD) is a minimally invasive treatment for early esophageal cancer. However, large mucosal defects after esophageal ESD result in refractory strictures. In the present study, we histologically evaluated the endoscopic transplantation of allogeneic epidermal cell sheets (ECSs) as a feasible therapy for preventing esophageal stricture after circumferential ESD in a porcine model.

Methods

Epidermal cells were isolated from the skin tissue of allogeneic pigs and cultured on temperature-responsive cell culture inserts for 2 weeks. Transplantable ECSs were harvested by reducing the temperature and endoscopically transplanting the sheets to ulcer sites immediately after esophageal ESD. The engraftment of transplanted ECSs was then evaluated in two pigs at 7 days after transplantation. Next, ten pigs were divided into two groups to evaluate the endoscopic transplantation of allogeneic ECSs for the prevention of esophageal strictures after ESD. Allogeneic ECSs were transplanted immediately after esophageal ESD in the transplantation group (n = 5), whereas the control group (n = 5) did not undergo transplantation.

Results

Most of the transplanted allogeneic ECSs were successfully engrafted at the ulcer sites in the early phase. Fluorescence in situ hybridization analysis revealed that several allogeneic cells were present in the transplanted area at 7 days after ESD. At 14 days after ESD, significant differences in body weight loss, dysphagia scores, and mucosal strictures were observed between the control and transplantation groups. Transplanting allogeneic ECSs after esophageal ESD promotes mucosal healing and angiogenesis and prevents excessive inflammation and granulation tissue formation.

Conclusions

Endoscopic and histological analyses revealed that allogeneic ECSs promoted artificial ulcer healing after ESD, preventing esophageal strictures after ESD.

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Large mucosal defects of the esophagus cause severe strictures.

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Allogeneic epidermal cell sheets promote esophageal mucosal healing.

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Allogeneic epidermal cell sheets induce angiogenesis in esophageal ulcers.

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Allogeneic epidermal cell sheets prevent excessive inflammation in esophageal ulcers.

Clinical outcomes on weekly endoscopic dilations as the initial approach to manage patients with complex benign esophageal strictures: report on 488 dilations

BACKGROUND

Success rate of endoscopic dilation (ED) of complex benign esophageal strictures (CBES) can be as low as 65%. Since EDs are usually performed at 2-4-week intervals, the aim of this study was to evaluate the clinical outcomes of EDs done initially at weekly intervals.

METHODS

A cohort of patients with CBES (luminal diameter < 10 mm) underwent ED at weekly intervals and subsequent dilation intervals adjusted based on response. Weekly EDs were also re-initiated in those requiring additional interventions (electro-cautery/stents). Group A patients: Failed prior EDs done at ≥ 2-week intervals. Group B: CBES with no prior dilations. Success was defined as achieving and maintaining a luminal diameter of ≥ 14 mm and patient remaining dysphagia-free with minimal re-interventions.

RESULTS

488 EDs were performed on a cohort of 57 consecutive patients with CBES. Median follow-up was 4 years. Group A: 21 patients (mean age 65 ± 13 years; mean interval between prior failed dilations 17 ± 9 days). 57% of these patients achieved long-term success with weekly dilations (mean 8 ± 4.7 dilations/patient). Group B: 36 patients (mean age 61 ± 13 years, mean 6.5 ± 5.5 dilations/patient). Long-term success was 83.3% (P = 0.033). Despite weekly dilations, unable to achieve a diameter of 14 mm in 5 patients. AE: perforation 1 (0.2%), bleeding 1 (0.2%).

CONCLUSION

Significant proportion of patients with CBES who failed prior dilations done at ≥ 2-week intervals achieved dysphagia-free status by initiating weekly dilations. Hence, before considering other options (electro-cautery/stents), one can consider using this approach. This approach can also be used upfront in patients with newly diagnosed CBES.

Recent Advances of Biomedical Materials for Prevention of Post-ESD Esophageal Stricture

Esophageal stricture commonly occurs in patients that have suffered from endoscopic submucosal dissection (ESD), and it makes swallowing difficult for patients, significantly reducing their life qualities. So far, the prevention strategies applied in clinical practice for post-ESD esophageal stricture usually bring various inevitable complications, which drastically counteract their effectiveness. Nowadays, with the widespread investigation and application of biomedical materials, lots of novel approaches have been devised in terms of the prevention of esophageal stricture. Biomedical polymers and biomedical-derived materials are the most used biomedical materials to prevent esophageal stricture after ESD. Both of biomedical polymers and biomedical-derived materials possess great physicochemical properties such as biocompatibility and biodegradability. Moreover, some biomedical polymers can be used as scaffolds to promote cell growth, and biomedical-derived materials have biological functions similar to natural organisms, so they are important in tissue engineering. In this review, we have summarized the current approaches for preventing esophageal stricture and put emphasis on the discussion of the roles biomedical polymers and biomedical-derived materials acted in esophageal stricture prevention. Meanwhile, we proposed several potential methods that may be highly rational and feasible in esophageal stricture prevention based on other researches associated with biomedical materials. This review is expected to offer a significant inspiration from biomedical materials to explore more effective, safer, and more economical strategies to manage post-ESD esophageal stricture.

Extracellular vesicles from adipose stromal cells combined with a thermoresponsive hydrogel prevent esophageal stricture after extensive endoscopic submucosal dissection in a porcine model

In this study, we investigated the combination of extracellular (nano) vesicles (EVs) from pig adipose tissue-derived stromal cells (ADSCs) and a thermoresponsive gel, Pluronic® F-127 (PF-127), to prevent stricture formation after endoscopic resection in a porcine model. ADSC EVs were produced at a liter scale by a high-yielding turbulence approach from ADSCs 3D cultured in bioreactors and characterized in terms of size, morphology and membrane markers. The thermoresponsive property of the PF-127 gel was assessed by rheology. The pro-regenerative potency of ADSC EVs was investigated ex vivo in esophageal biopsies under starvation. In vivo tests were performed in a porcine model after extended esophageal endoscopic mucosal dissection (ESD). Pigs were randomized into 3 groups: control (n = 6), gel (n = 6) or a combination of 1.45 × 1012 EVs + gel (n = 6). Application of gel ± EVs was performed just after ESD with a follow-up finalized on day 21 post-ESD. There was a trend towards less feeding disorder in the EV + gel group in comparison with the gel and the control groups (16.67% vs. 66.7% vs. 83.33%, respectively) but without reaching a statistically significant difference. A significant decrease in the esophageal stricture rate was confirmed by endoscopic, radiological and histological examination for the EV + gel group. A decrease in the mean fibrosis area and larger regenerated muscularis mucosae were observed for the EV + gel group. In summary, the application of EVs + gel after extended esophageal endoscopic resection succeeded in preventing stricture formation with an anti-fibrotic effect. This nano-therapy may be of interest to tackle an unmet medical need considering that esophageal stricture is the most challenging delayed complication after extended superficial cancer resection by endoscopy.

Covering Post-Endoscopic Submucosal Dissection Ulcers in Miniature Swine with Hexanoyl (Hx:C6) Group-Modified Alkaline-Treated Gelatin Porous Film (HAG) Induces Proper Healing by Decreasing Inflammation and Fibrosis

BACKGROUND AND AIMS

Hexanoyl (Hx:C6) group-modified alkaline-treated gelatin porous film (HAG) is a newly developed degradable hydrogel characterized by strong adhesiveness and high affinity for vascular endothelial growth factor (VEGF). The aim of this study was to clarify the effect of HAG sheets on the healing process of post-endoscopic submucosal dissection (ESD) porcine gastric artificial ulcers.

METHODS

(1) To evaluate the adhesiveness of HAG sheets over time, we performed ESD to create 1 artificial ulcer and covered the lesion with 1 HAG sheet using 1 miniature swine. We observed 2 ulcers by endoscopic and microscopic examinations. (2) To examine the effect of HAG sheets on post-ESD ulcer healing, we performed ESD using 5 miniature swine. The artificial ulcers were covered with HAG sheets, or left uncovered after ESD (day 0), followed by macroscopic and microscopic examinations. On days 7 and 14, we observed 2 ulcers by endoscopic examinations. On day 14, the animals were sacrificed, and histological examination was performed on the 3 stomachs that could be extirpated.

RESULTS

(1) On day 7, adhesion of HAG sheets was observed. (2) Gastric ulcer area on day 7 was significantly larger in the covered ulcers than in the non-covered ulcers (p = 0.046). On day 14, although there was no significant difference in ulcer area irrespective of covering (p = 0.357), the covered ulcers tended to repair less fold convergence than non-covered ulcers. The covered ulcer sheets significantly decreased inflammatory cell infiltration (p = 0.011), but significantly increased the abundance of macrophages (p = 0.033), in submucosal layers. Also, the abundance of alpha-smooth muscle actin-positive cells in submucosal layers of the covered ulcers was significantly reduced (p = 0.044), leading to a decrease in collagen accumulation. In addition, fibrosis and atrophy of the muscularis propria were significantly lower for covered ulcers than for non-covered ulcers. Furthermore, microvessels and VEGF-positive cells were significantly more abundant in the submucosal layers of the covered ulcers (p < 0.001 and p = 0.024, respectively).

CONCLUSIONS

HAG sheets induced post-ESD ulcer healing with less submucosal inflammation and muscularis propria injury and have the potential to decrease excess scarring.

Allogeneic epithelial cell sheet transplantation for preventing esophageal stricture after circumferential ESD in a porcine model: preliminary results

OBJECTIVES

Circumferential endoscopic submucosal dissection (ESD) for large lesions induces severe stricture, requiring subsequent treatment. We aimed to evaluate the efficacy of allogeneic epithelial cell sheet transplantation in preventing esophageal stricture after circumferential ESD in a porcine model.

MATERIALS AND METHODS

A total of 15 conventional pigs underwent a 4 cm long circumferential ESD in the mid-esophagus. Out of these animals, 11 were immediately subjected to allogeneic oral mucosal cell sheet transplantation at the resection site, whereas four pigs underwent circumferential ESD only. We performed upper endoscopy 1 and 2 weeks after ESD and assessed the degree of esophageal stricture and histologic characteristics.

RESULTS

Dysphagia scores and weight change ratios recorded 1 and 2 weeks after ESD did not differ between the two groups. The stricture rate 2 weeks after ESD was 100% in the control group and 90.9% in the cell sheet group (p = 1.000). The median mucosal constriction rates of the control and cell sheet groups were 73.5% (range 63.0-80.0%) and 53.8% (37.5-73.3%, p = .018), respectively. With regard to microscopic measurements, the length of re-epithelialization was greater in the cell sheet group than in the control group (2,495 µm vs. 369 µm, p = .008). Median fibrosis thickness and degree of muscle damage were not significantly different between groups.

CONCLUSIONS

Although allogeneic epithelial cell sheet transplantation showed greater re-epithelialization and less mucosal constriction of post-ESD ulcers, it was not sufficiently effective in preventing post-ESD stricture.

Progress of esophageal stricture prevention after endoscopic submucosal dissection by regenerative medicine and tissue engineering

Endoscopic submucosal dissection (ESD) has been widely accepted as an effective treatment for early esophageal cancer. However, post-ESD esophageal stricture remains a thorny issue. We herein review many strategies for preventing post-ESD esophageal stricture, as well as discuss their strengths and weaknesses. These strategies include pharmacological prophylaxis, esophageal stent and tissue engineering and regenerative medicine treatment. In this review, we summarize these studies and discuss the underlying progress and future directions of tissue engineering and regenerative medicine treatment.

Efficacy of oral steroid gel in preventing esophageal stricture after extensive endoscopic submucosal dissection: a randomized controlled trial

BACKGROUND AND AIMS

Esophageal stricture is a distressing issue for patients with early esophageal cancer following extensive endoscopic submucosal dissection (ESD), and the current steroid-based approaches are unsatisfactory for stricture prophylaxis. We evaluated the efficacy of oral hydrocortisone sodium succinate and aluminum phosphate gel (OHA) for stricture prophylaxis after extensive ESD.

METHODS

Patients undergoing > 3/4 circumferential ESD were randomized to either the endoscopic loco-regional triamcinolone acetonide injection (ETI) plus oral prednisone group or the OHA group. The primary endpoint was incidence of esophageal stricture, and the secondary endpoints included adverse events (AEs) and endoscopic balloon dilations (EBDs).

RESULTS

The incidence of esophageal stricture in OHA group (per-protocol analysis, 9.4%, 3/32; intention-to-treat analysis, 12.1%, 4/33) was significantly less than that of control group (per-protocol analysis, 35.5%, 11/31, P = 0.013; intention-to-treat analysis, 39.4%, 13/33, P = 0.011). Two sessions of EBD were necessary to release all strictures in the OHA group, while the similar EBDs (median 2, range 1-4) for 11 of the control. Operation-related AEs included infection (control vs. OHA group = 9.7% vs. 31.3%, P = 0.034), operation-related hypokalemia (19.4% vs. 31.3%, P = 0.278), perforation (3.2% vs. 3.1%), post-ESD hemorrhage (6.5% vs. 0%), and cardiac arrhythmia (0% vs. 6.3%). Steroid-related AEs included steroid-related hypokalemia (16.1% vs. 25%) and bone fracture (3.2% vs. 0%). Multivariate logistic regression analysis demonstrated that OHA was an independent protective factor for stricture (OR 0.079; 95%CI 0.011, 0.544; P = 0.01) and mucosal defect > 11/12 circumference was an independent risk factor (OR 49.91; 95%CI 6.7, 371.83; P < 0.001).

CONCLUSIONS

OHA showed significantly better efficacy in preventing esophageal stricture after > 3/4 circumferential ESD compared to ETI plus oral prednisone.

Prevention of Stricture after Endoscopic Submucosal Dissection for Superficial Esophageal Cancer: A Review of the Literature

Endoscopic resection has been the standard treatment for intramucosal esophageal cancers (ECs) because of the low risk of lymph node metastases in the lesions. In recent years, endoscopic submucosal dissection (ESD), which can resect large ECs, has been performed. However, the risk of esophageal stricture after ESD is high when the mucosal defect caused by the treatment exceeds 3/4 of the circumference of the lumen. Despite the subsequent high risk of luminal stricture, ESD has been performed even in cases of circumferential EC. In such cases, it is necessary to take measures to prevent stricture. Therefore, in this review, we aimed to clarify the current status of stricture prevention methods after esophageal ESD based on previous literature. Although various prophylactic methods have been reported to have stricture-preventing effects, steroid injection therapy and oral steroid administration are mainstream. However, in cases of circumferential EC, both steroid injection therapy and oral steroid administration cannot effectively prevent luminal stricture. To solve this issue, clinical applications, such as tissue shielding methods with polyglycolic acid sheet, autologous oral mucosal epithelial sheet transplantation, and stent placement, have been developed. However, effective prophylaxis of post-ESD mucosal defects of the esophagus is still unclear. Therefore, further studies in this research field are needed.

Regenerative medicine for the upper gastrointestinal tract

The main surgical strategy for gastrointestinal tract malignancy is en bloc resection, which consists of not only resection of the involved organs but also simultaneous resection of the surrounding or adjacent mesenteries that contain lymph vessels and nodes. After resection of the diseased organs, the defect of the gastrointestinal conduit is replaced with organs located downstream, such as the stomach and jejunum. However, esophageal and gastric reconstruction using these natural substitutes is associated with a diminished quality of life due to the loss of the reserve function, damage to the antireflux barrier, and dumping syndrome. Thus, replacement of the deficit after resection with the patient's own regenerated tissue to compensate for the lost function and tissue using regenerative medicine will be an ideal treatment. Many researchers have been trying to construct artificial organs through tissue engineering techniques; however, none have yet succeeded in growing a whole organ because of the complicated functions these organs perform, such as the processing and absorption of nutrients. While exciting results have been reported with regard to tissue engineering techniques concerning the upper gastrointestinal tract, such as the esophagus and stomach, most of these achievements have been observed in animal models, and few successful approaches in the clinical setting have been reported for the replacement of mucosal defects. We review the recent progress in regenerative medicine in relation to the upper gastrointestinal tract, such as the esophagus and stomach. We also focus on the functional capacity of regenerated tissue and its role as a culture system to recapitulate the mechanisms underlying infectious disease. With the emergence of technology such as the fabrication of decellularized constructs, organoids and cell sheet medicine, collaboration between gastrointestinal surgery and regenerative medicine is expected to help establish novel therapeutic modalities in the future.

Advances in the Prevention and Treatment of Esophageal Stricture after Endoscopic Submucosal Dissection of Early Esophageal Cancer

Endoscopic submucosal dissection (ESD) has become the main treatment for early esophageal cancer. While treating the disease, ESD may also cause postoperative esophageal stricture, which is a global issue that needs resolution. Various methods have been applied to resolve the problem, such as mechanical dilatation, glucocorticoids, anti-scarring drugs, and regenerative medicine; however, no standard treatment regimen exists. This article describes and evaluates the strengths and limitations of new and promising potential strategies for the treatment and prevention of esophageal strictures.

Esophageal regenerative therapy using cell sheet technology

We have been conducting research on esophageal regenerative therapy using cell sheet technology. In particular, in the endoscopic field, we have pushed forward clinical research on endoscopic transplantation of cultured autologous oral mucosal epithelial cell sheets to esophageal ulcer after endoscopic submucosal dissection (ESD). We started research in this direction using animal models in 2004 and performed clinical research in 2012 in collaboration with Nagasaki University and Karolinska Institute. Although in full-circumferential cases it was difficult to prevent esophageal stricture after ESD, there were no complications and stricture could be suppressed. The cell sheet technology is still in its infancy. However, we are convinced that it has a high potential for application in various areas of gastrointestinal science. In this review, we focus on the pre-clinical and clinical trial results obtained and on the theoretical aspects of (1) stricture prevention, (2) esophageal tissue engineering research, and (3) endoscopic transplantation, and review the esophageal regenerative therapy by cell sheet technology.

A novel technique of endoscopic submucosal dissection for circumferential ileocecal valve adenomas with terminal ileum involvement: the "doughnut resection" (with videos)

BACKGROUND

Ileocecal valve (ICV) lesions are difficult to resect endoscopically and patients are often referred for laparoscopic colectomy. ICV involvement has been shown to be related to technical failure and tumor recurrence after endoscopic mucosal resection (EMR) and represents a challenge for endoscopic submucosal dissection (ESD). Few publications have focused specifically on endoscopic management of ICV lesions.

METHODS

We developed a novel ESD technique, the "doughnut resection," for circumferential ICV adenomas with terminal ileum involvement. Two circumferential mucosal incisions are performed, one in the ileum and the other in the cecum, followed by submucosal dissection of the disk of tissue between the two incisions around a guiding stent placed across the valve that helps guide the dissection as it crosses the valve orifice. The lesion is removed en bloc in the shape of a "doughnut" with two concentric assessable lateral margins. The underwater ESD technique and a gastroscope were used to facilitate the resection.

RESULTS

Seven patients received the doughnut resection. The median patient age was 67 years. All patients had prior biopsy and three had prior endoscopic resection (1-6 times). The median specimen diameter was 4.5 cm (range 3-8). All resections were en bloc and R0. There was no perforation, delayed bleeding, or other clinically significant adverse events. After a median follow-up of 21 months (range 12-32), there was no tumor recurrence.

CONCLUSION

The "doughnut resection" is a feasible, safe, and effective method to remove circumferential ICV lesions endoscopically even for patients with multiple prior tumor manipulations.

Strategies to prevent stricture after esophageal endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) has been widely applied as a less invasive and more effective method for treating early esophageal cancers such as squamous cell carcinoma and dysplasia of Barrett's esophagus. However, post-ESD esophageal stricture often occurs if patients suffer circumferential mucosal defects of more than three-quarters of the circumference of the esophagus, which makes it difficult for patients to swallow and greatly reduces their quality of life. Moreover, there is currently no standard method to treat post-ESD esophageal stricture, even though it is extraordinarily important to prevent its formation. In recent years, several strategies to prevent esophageal stricture have emerged. These strategies can be classified into pharmacological, mechanical, tissue engineering, and other novel strategies, with each strategy having its own strengths and weaknesses. Although the pharmacological prophylaxis and mechanical strategies are relatively mature, they still have their drawbacks like high time-consumption, the occurrence of re-stricture, and significant side effects. Tissue engineering strategies and other novel strategies have shown promising preliminary results, but more clinical trials are needed. In this review, we discuss these strategies, with a particular focus on tissue engineering strategies and other novel strategies. It is hoped that this discussion will aid in finding more effective and safer strategies to prevent esophageal stricture.

Evaluating the effect of injecting triamcinolone acetonide in two sessions for preventing esophageal stricture after endoscopic submucosal dissection

Background and study aims  Several previous reports indicate that endoscopic injection of triamcinolone acetonide (TA) after widespread endoscopic submucosal dissection (ESD) is effective for preventing esophageal stricture. We investigated the efficacy of injecting TA in two sessions for preventing stricture formation post-ESD. Patients and methods  Sixty-six consecutive patients with widespread mucosal defects that affected more than three-fourths of the circumference of the esophagus were included. The study group (n = 40) received TA injections over two sessions: immediately after and 14 days after ESD. The control group (n = 26) did not receive a TA injection. This study was performed retrospectively against historical controls. The primary endpoint of this study was frequency of stricture after TA injection. The secondary endpoint was number of required endoscopic balloon dilations (EBDs) after TA injection. Results  The post-ESD stricture rate among patients who had subcircumferential mucosal defects was 45.7 % in the study group (16/35 patients), which was significantly lower than the rate of 73.9 % in the control group (17/23 patients; P  = 0.031). The number of EBD procedures required was significantly lower in the study group (median 0, range 0 - 7) than in the control group (median 4, range 0 - 20; P  < 0.001). There was no significant difference between the study and control groups among the patients who had full circumferential mucosal defects. Conclusion  This study showed that performing two sessions of TA injection is an effective and safe treatment for prevention of esophageal stricture following subcircumferential ESD.

Prevention of esophageal stricture after endoscopic resection

Stricture formation after esophageal endoscopic resection has a negative impact on patients' quality of life because it causes dysphagia and requires multiple endoscopic dilations. Various methods by which to prevent stricture have recently been developed and reported. Among these methods, local steroid injection is the most commonly used and is currently considered the standard method for noncircumferential resection. However, local steroid injection has a limited effect on circumferential resection. Thus, oral steroid administration is used for such cases because it may have a stronger effect than local injection. Steroid treatment, both by local injection and oral administration, is effective and low-cost; however, it may cause fragility of the esophageal wall, resulting in adverse events such as perforation during balloon dilatation. Many innovative approaches have been developed, such as tissue-shielding methods with polyglycolic acid, tissue engineering approaches with autologous oral mucosal epithelial cell sheet transplantation, and stent insertion. These methods may be promising, but they are limited by a scarcity of data. Further investigations are needed to confirm the efficacy of these methods.

Comparison of two porcine benign esophageal stricture models using radiofrequency ablation and endoscopic submucosal tunnel dissection

BACKGROUND/AIMS

Large-animal benign esophageal stricture (BES) models are needed for the development of new endoscopic therapies and related devices. This study was undertaken to develop and compare swine BES models produced by radiofrequency ablation (RFA) or endoscopic submucosal tunnel dissection (ESTD).

MATERIALS AND METHODS

RFA and ESTD were each performed on three pigs. Follow-up endoscopy and esophagography were performed immediately after the procedures and then 2, 3, and 4 weeks later. Four weeks after the procedures, all animals were sacrificed, and gross and histologic examinations were performed.

RESULTS

BES was successfully achieved in both the RFA and ESTD groups, and all animals survived without any serious adverse events during the 4-week follow-up period. Mean procedural times were 9.3 min for RFA and 89.3 min for ESTD. ESTD caused long segment strictures whose average length was 4.5 cm, whereas RFA produced short strictures whose average length was 1.4 cm. BES began to form 2 weeks after both procedures. Degrees of strictures were similar at 3 and 4 weeks in the ESTD group; however, it started deteriorating over time in the RFA group. Histologic examinations showed that ESTD caused inflammation and fibrosis in the submucosal layer, whereas RFA induced extensive inflammation in the submucosal and muscularis propria layers.

CONCLUSION

BES was successfully achieved using RFA or ESTD in swine without serious complications. The methods have different characteristics; therefore, researchers should choose the method more appropriate for their purposes.

Deployment of carboxymethyl cellulose sheets to prevent esophageal stricture after full circumferential endoscopic submucosal dissection: A porcine model

BACKGROUND AND AIM

Esophageal stricture is a serious adverse event secondary to extensive endoscopic submucosal dissection (ESD). The present study aimed to investigate the efficacy of carboxymethyl cellulose (CMC) sheets for the prevention of esophageal stricture after full circumferential ESD in an animal model.

METHODS

Fourteen porcine models were randomized into a control group (n = 7) and a CMC group (n = 7). Five-centimeter-long circumferential esophageal ESD was carried out at a distance of 40 to 45 cm from the incisors in all models. In the CMC group, CMC sheets were placed over the mucosal defect completely after ESD, whereas the control group underwent routine ESD only. Endoscopic examination was conducted after the first and second week post-ESD. Esophageal specimens were harvested during post-mortem and were evaluated for macroscopic and histological appearance. Blood serum levels of four pro-inflammatory or profibrotic cytokines were measured quantitatively.

RESULTS

The CMC group had better food tolerability during the second week post-ESD. The CMC group showed a significantly lower esophageal mucosal stricture rate compared to the control group. Histological assessments showed less fibrosis in the submucosal layer, milder damage to the muscularis propria, and enhanced re-epithelization in the CMC group. Serum transforming growth factor beta 1 levels were significantly lower in the CMC group post-ESD.

CONCLUSION

Deployment of CMC sheets on the mucosal defect appears to be a promising method for preventing esophageal strictures after extensive ESD.

Progress on the Prevention of Esophageal Stricture after Endoscopic Submucosal Dissection

Endoscopic submucosal dissection (ESD) has been widely accepted as an effective, minimally invasive treatment for superficial esophageal cancers. However, esophageal stricture often occurs in patients with large mucosal defects after ESD. In this review, we discuss various approaches recently researched to prevent esophageal strictures after ESD. These approaches can be classified as pharmacological treatments, esophageal stent treatments, and tissue engineering approaches. Most of the preventive approaches still have their limitations and require further research. With the improvement of current therapies, ESD can be more widely utilized as a minimally invasive treatment with minimal complications.

Oral administration of conditioned medium obtained from mesenchymal stem cell culture prevents subsequent stricture formation after esophageal submucosal dissection in pigs

BACKGROUND AND AIMS

Endoscopic submucosal dissection (ESD) for esophageal cancer often causes postoperative stricture when more than three fourths of the circumference of the esophagus is dissected. Mesenchymal stem cells are a valuable cell source in regenerative medicine, and conditioned medium (CM) obtained from mesenchymal stem cells reportedly inhibits inflammation. In this study we evaluated whether CM could prevent esophageal stricture after ESD.

METHODS

We resected a semi-circumference of pig esophagus by ESD. We prepared CM gel by mixing with 5% carboxymethyl cellulose and endoscopically applied it onto the wound bed immediately after ESD and on days 8 and 15 (weekly CM group) or administered it orally from days 1 to 4 (daily CM group). We also injected triamcinolone acetonide into the remaining submucosa immediately after ESD (steroid group). We killed the pigs on day 8 or day 22 to measure the stricture rate and to perform histologic analysis.

RESULTS

Stricture rate in weekly and daily CM groups and steroid groups were significantly lower than in the control group on day 22. Moreover, CM significantly attenuated the number of activated myofibroblasts and fiber thickness on day 22. CM also significantly decreased the infiltration of neutrophils and macrophages compared with the control group on day 8.

CONCLUSIONS

CM gel prevents esophageal stricture formation by suppressing myofibroblast activation and fibrosis after the infiltration of neutrophils and macrophages. Oral administration of CM gel is a promising treatment for the prevention of post-ESD stricture.

ADSC-sheet Transplantation to Prevent Stricture after Extended Esophageal Endoscopic Submucosal Dissection

In past years, the cell-sheet construct has spurred wide interest in regenerative medicine, especially for reconstructive surgery procedures. The development of diversified technologies combining adipose tissue-derived stromal cells (ADSCs) with various biomaterials has led to the construction of numerous types of tissue-engineered substitutes, such as bone, cartilage, and adipose tissues from rodent, porcine, or human ADSCs. Extended esophageal endoscopic submucosal dissection (ESD) is responsible for esophageal stricture formation. Stricture prevention remains challenging, with no efficient treatments available. Previous studies reported the effectiveness of mucosal cell-sheet transplantation in a canine model and in humans. ADSCs are attributed anti-inflammatory properties, local immune modulating effects, neovascularization induction, and differentiation abilities into mesenchymal and non-mesenchymal lineages. This original study describes the endoscopic transplantation of an ADSC tissue-engineered construct to prevent esophageal stricture in a swine model. The ADSC construct was composed of two allogenic ADSC sheets layered upon each other on a paper support membrane. The ADSCs were labeled with the PKH67 fluorophore to allow probe-based confocal laser endomicroscopy (pCLE) monitoring. On the day of transplantation, a 5-cm and hemi-circumferential ESD known to induce esophageal stricture was performed. Animals were immediately endoscopically transplanted with 4 ADSC constructs. The complete adhesion of the ADSC constructs was obtained after 10 min of gentle application. Animals were sacrificed on day 28. All animals were successfully transplanted. Transplantation was confirmed on day 3 with a positive pCLE evaluation. Compared to transplanted animals, control animals developed severe strictures, with major fibrotic tissue development, more frequent alimentary trouble, and reduced weight gain. In our model, the transplantation of allogenic ADSCs, organized in double cell sheets, after extended ESD was successful and strongly associated with a lower esophageal stricture rate.

Transplantation of epidermal cell sheets by endoscopic balloon dilatation to avoid esophageal re-strictures: initial experience in a porcine model

Background and study aims: Epidermal cell sheet (ECS) transplantation immediately after aggressive endoscopic submucosal dissection (ESD) has been shown to be safe and effective in the prevention of esophageal strictures. This study evaluated the feasibility of ECS transplantation after endoscopic balloon dilation (EBD) in a porcine model. Methods: Six pigs underwent circumferential esophageal ESD under general anesthesia. Two weeks later, two pigs underwent EBD and transplantation of an autologous ECS, two underwent EBD alone, and two underwent endoscopic observation only (control). Results: The two pigs in the transplantation group underwent six ECS transplants after EBD with five of the six (83 %) being successful, as shown by engraftment of transplanted ECSs after 7 days. No adverse events were observed. Stricture rates were lower in the two transplanted pigs (55 % and 60 %) than in the control (92.2 % and 87.7 %) and EBD-treated (71.7 % and 78.2 %) pigs. Infiltration of inflammatory cells was significantly lower in the transplanted pigs than in the control and EBD-treated pigs. Conclusion: Preliminary results indicate the stability of the ECS transplantation procedure and the engraftment of transplanted ECS in the tears after EBD. This proof-of-concept study suggests that covering tears with ECSs after EBD may avoid re-strictures.

In-vivo oesophageal regeneration in a human being by use of a non-biological scaffold and extracellular matrix

BACKGROUND

Tissue-engineered extracellular matrix populated with autologous pluripotent cells can result in de-novo organogenesis, but the technique is complex, not widely available, and has not yet been used to repair large oesophageal defects in human beings. We aimed to use readily available stents and extracellular matrix to regenerate the oesophagus in vivo in a human being to re-establish swallowing function.

METHODS

In a patient aged 24 years, we endoscopically placed a readily available, fully covered, self-expanding, metal stent (diameter 18 mm, length 120 mm) to bridge a 5 cm full-thickness oesophageal segment destroyed by a mediastinal abscess and leading to direct communication between the hypopharynx and the mediastinum. A commercially available extracellular matrix was used to cover the stent and was sprayed with autologous platelet-rich plasma adhesive gel. The sternocleidomastoid muscle was placed over the matrix. After 4 weeks, stent removal was needed due to stent migration, and was replaced with three stents telescopically aligned to improve anchoring. The stents were removed after 3·5 years and the oesophagus was assessed by endoscopy, biopsy, endoscopic ultrasonography, and high-resolution impedance manometry.

FINDINGS

After stent removal we saw full-thickness regeneration of the oesophagus with stratified squamous epithelium, a normal five-layer wall, and peristaltic motility with bolus transit. 4 years after stent removal, the patient was eating a normal diet and maintaining a steady weight.

INTERPRETATION

Maintenance of the structural morphology of the oesophagus with off-the-shelf non-biological scaffold and stimulation of regeneration with commercially available extracellular matrix led to de-novo structural and functional regeneration of the oesophagus.

FUNDING

None.

Cell Sheet Transplantation for Esophageal Stricture Prevention after Endoscopic Submucosal Dissection in a Porcine Model

Background & Aims

Extended esophageal endoscopic submucosal dissection (ESD) is highly responsible for esophageal stricture. We conducted a comparative study in a porcine model to evaluate the effectiveness of adipose tissue-derived stromal cell (ADSC) double cell sheet transplantation.

Methods

Twelve female pigs were treated with 5 cm long hemi-circumferential ESD and randomized in two groups. ADSC group (n = 6) received 4 double cell sheets of allogenic ADSC on a paper support membrane and control group (n = 6) received 4 paper support membranes. ADSC were labelled with PKH-67 fluorophore to allow probe-based confocal laser endomicroscopie (pCLE) monitoring. After 28 days follow-up, animals were sacrificed. At days 3, 14 and 28, endoscopic evaluation with pCLE and esophagography were performed.

Results

One animal from the control group was excluded (anesthetic complication). Animals from ADSC group showed less frequent alimentary trouble (17% vs 80%; P = 0.08) and higher gain weight on day 28. pCLE demonstrated a compatible cell signal in 4 animals of the ADSC group at day 3. In ADSC group, endoscopy showed that 1 out of 6(17%) animals developed a severe esophageal stricture comparatively to 100% (5/5) in the control group; P = 0.015. Esophagography demonstrated a decreased degree of stricture in the ADSC group on day 14 (44% vs 81%; P = 0.017) and day 28 (46% vs 90%; P = 0.035). Histological analysis showed a decreased fibrosis development in the ADSC group, in terms of surface (9.7 vs 26.1 mm²; P = 0.017) and maximal depth (1.6 vs 3.2 mm; P = 0.052).

Conclusion

In this model, transplantation of allogenic ADSC organized in double cell sheets after extended esophegeal ESD is strongly associated with a lower esophageal stricture’s rate.

Systematic review: the prevention of oesophageal stricture after endoscopic resection

BACKGROUND

Extensive endoscopic resections for the treatment of early oesophageal neoplasia can result in fibro-inflammatory strictures that require repeated interventions, which significantly alter the patients' quality of life.

AIMS

To review current evidence about the prevention of oesophageal strictures following endoscopic resections.

METHODS

Systematic search of PubMed and Embase from inception to March 2015 using appropriate keywords. All original publications in English were included, and articles on the treatment of oesophageal stricture were excluded.

RESULTS

Of the 461 hits, 62 studies were included in the analysis. Among the wound-protective strategies, polyglycolic acid sheets showed the most convincing evidence with a 37.5% stricture rate and excellent safety. Regenerative medicine, using cell sheets of autologous keratinocytes, resulted in a 25% stricture rate, although with cost and availability concerns. Among anti-proliferative treatment modalities, steroid treatment, either endoscopically injected triamcinolone in the resection wound or orally administered prednisolone, proved effective with an overall stricture rate of 13.5%, with safety concerns regarding late oesophageal perforations and infectious morbidity. Among mechanical treatment options, poorly effective and high-risk preventive balloon dilation tend to be replaced by prophylactic covered stent, with 18-28% stricture rates.

CONCLUSIONS

Although oral or locally injected steroids are promising options, no currently available technique is sufficiently efficient and devoid of significant safety concerns to recommend its routine use for the prevention of strictures after extensive endoscopic resection. Improving our knowledge in the mechanisms of oesophageal wound healing will guide the development of novel methods for stricture prevention.

Useful strategies to prevent severe stricture after endoscopic submucosal dissection for superficial esophageal neoplasm

The minimal invasiveness of endoscopic submucosal dissection (ESD) prompted us to apply this technique to large-size early esophageal squamous cell carcinoma and Barrett’s adenocarcinoma, despite the limitations in the study population and surveillance duration. A post-ESD ulceration of greater than three-fourths of esophageal circumference was advocated as an important risk factor for refractory strictures that require several sessions of dilation therapy. Most of the preoperative conditions are asymptomatic, but dilatation treatment for dysphagia associated with the stricture has potential risks of severe complications and a worsening of quality of life. Possible mechanisms of dysphasia were demonstrated based on dysmotility and pathological abnormalities at the site: (1) delayed mucosal healing; (2) severe inflammation and disorganized fibrosis with abundant extracellular matrices in the submucosa; and (3) atrophy in the muscularis proper. However, reports on the administration of anti-scarring agents, preventive dilation therapies, and regenerative medicine demonstrated limited success in stricture prevention, and there were discrepancies in the study designs and protocols of these reports. The development and consequent long-term assessments of new prophylactic technologies on the promotion of wound healing and control of the inflammatory/tumor microenvironment will require collaboration among various research fields because of the limited accuracy of preoperative staging and high-risk of local recurrence.

Bio-sheet graft therapy for artificial gastric ulcer after endoscopic submucosal dissection: an animal feasibility study

BACKGROUND

Various bio-sheet grafts have been attempted either to accelerate healing of artificial ulcers or to prevent adverse events after endoscopic submucosal dissection (ESD), but neither prospective nor mechanistic studies were available.

OBJECTIVE

To evaluate the substantial effect of a bio-sheet graft on artificial ulcer healing and its feasibility as an endoscopic treatment modality.

DESIGN

Preclinical, in vivo animal experiment and proof-of-concept study.

SETTING

Animal laboratory.

SUBJECTS

Three mini-pigs, Sus scrofa, mean age 14 months.

INTERVENTION

Multiple ulcers sized 2.5 cm in diameter were generated by ESD in 3 mini-pigs and were assigned randomly into the following 3 groups; control group, bio-sheet group, or combination (bio-sheet plus drug) group. Bio-sheet grafts or bio-sheet plus drug combinations were applied on the artificial ulcers immediately after the ESD.

MAIN OUTCOME MEASUREMENTS

Feasibility and efficacy of endoscopic bio-sheet graft therapy for the management of artificial ulcers and the evaluation of healing conditions based on histology changes in the remaining gastric bed tissues harvested from the stomachs.

RESULTS

Thirty-three ESD specimens were obtained. On an image analysis of the ratio of healed area in the remaining gastric bed tissue compared with the matched dissected gastric mucosa, the control group showed the most significant improvement in healing activity among the 3 groups (P < .05), whereas the severity of inflammation in the remaining ulcer tissue was significantly attenuated in bio-sheet and combination groups (P < .05).

LIMITATIONS

Animal model.

CONCLUSION

Although the bio-sheet grafts provided physical protection from gastric acid attack as reflected in the attenuated inflammation on the ulcer beds, unexpected delayed ulcer healing was noted in the bio-sheet graft group because of its physical hindrance of the healing process.

Prevention of esophageal strictures after endoscopic submucosal dissection

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have recently been accepted as less invasive methods for treating patients with early esophageal cancers such as squamous cell carcinoma and dysplasia of Barrett’s esophagus. However, the large defects in the esophageal mucosa often cause severe esophageal strictures, which dramatically reduce the patient’s quality of life. Although preventive endoscopic balloon dilatation can reduce dysphagia and the frequency of dilatation, other approaches are necessary to prevent esophageal strictures after ESD. This review describes several strategies for preventing esophageal strictures after ESD, with a particular focus on anti-inflammatory and tissue engineering approaches. The local injection of triamcinolone acetonide and other systemic steroid therapies are frequently used to prevent esophageal strictures after ESD. Tissue engineering approaches for preventing esophageal strictures have recently been applied in basic research studies. Scaffolds with temporary stents have been applied in five cases, and this technique has been shown to be safe and is anticipated to prevent esophageal strictures. Fabricated autologous oral mucosal epithelial cell sheets to cover the defective mucosa similarly to how commercially available skin products fabricated from epidermal cells are used for skin defects or in cases of intractable ulcers. Fabricated autologous oral-mucosal-epithelial cell sheets have already been shown to be safe.

Prevention and treatment of esophageal stenosis after endoscopic submucosal dissection for early esophageal cancer

Endoscopic submucosal dissection (ESD) for the treatment of esophageal mucosal lesions is associated with a risk of esophageal stenosis, especially for near-circumferential or circumferential esophageal mucosal defects. Here, we review historic and modern studies on the prevention and treatment of esophageal stenosis after ESD. These methods include prevention via pharmacological treatment, endoscopic autologous cell transplantation, endoscopic esophageal dilatation, and stent placement. This short review will focus on direct prevention and treatment, which may help guide the way forward.

Regenerative medicine: tissue-engineered cell sheet for the prevention of post-esophageal ESD stricture

Induced pluripotent stem (iPS) cells have captured the world's attention and directed an unprecedented focus on regenerative medicine. The potential of iPS cells to aid in the development of new treatments for various diseases is exciting, and researchers are only beginning to discover their potential benefits for humans. iPS cells are more effective if they are interconnected with tissues; however, new technologies are needed to create and transplant these tissues. This study introduces a new connection between endoscopy and regenerative medicine in gastroenterology through specifically addressing how cell sheet technology can be a viable method of tissue creation and transplantation.

Esophageal stricture induced by an ultraslim upper endoscope in a novel rabbit model of corrosive injury

OBJECTIVE

Benign esophageal strictures are regularly encountered problems in clinical practice. The management of refractory benign esophageal stricture, which fails to establish adequate food passage despite multiple dilatation sessions, has been considered challenging. Experimental animal models are essential for the development of effective treatment methods. The aim of this study was to establish a new animal model of benign esophageal stricture using rabbits.

MATERIAL AND METHODS

Corrosive injury of the esophagus was induced by administration of 1 ml of 1.5% sodium hydroxide in eight rabbits using an ultraslim upper endoscope equipped with a 5-Fr polytetrafluoroethylene tube and 5-Fr balloon catheter. Two weeks after corrosive injury, endoscopic examination was performed to confirm the state of the injury site. Four weeks after corrosive injury, the esophageal stricture was assessed by endoscopy and esophagography. All animals were then euthanized.

RESULTS

Two weeks after corrosive injury, endoscopic examination showed that ulceration had been induced. Four weeks after corrosive injury, endoscopic, radiologic and gross examinations showed that esophageal stricture had been induced without complications in all animals. The esophageal lumen diameter was reduced by an average of 51.8% (range, 48.3%-57.2%), and the mean stricture length was 25.7 mm (range, 20.1-29.3 mm). Microscopic examination revealed focal ulceration and submucosal thickening secondary to fibrosis.

CONCLUSIONS

Rabbit esophageal stricture induced by endoscopic delivery of a small amount of low-concentration sodium hydroxide is a relatively simple, safe, and reproducible animal model. This model may be useful in the development of new treatment methods for esophageal stricture.

Different healing process of esophageal large mucosal defects by endoscopic mucosal dissection between with and without steroid injection in an animal model

Background

Stricture formation is one of the major complications after endoscopic removal of large superficial squamous cell neoplasms of the esophagus, and local steroid injections have been adopted to prevent it. However, fundamental pathological alterations related to them have not been well analyzed so far. The aim of this study was to analyze the time course of the healing process of esophageal large mucosal defects resulting in stricture formation and its modification by local steroid injection, using an animal model.

Methods

Esophageal circumferential mucosal defects were created by endoscopic mucosal dissection (ESD) for four pigs. One pig was sacrificed five minutes after the ESD, and other two pigs were followed-up on endoscopy and sacrificed at the time of one week and three weeks after the ESD, respectively. The remaining one pig was followed-up on endoscopy with five times of local steroid injection and sacrificed at the time of eight weeks after the ESD. The esophageal tissues of all pigs were subjected to pathological analyses.

Results

For the pigs without steroid injection, the esophageal stricture was completed around three weeks after the ESD on both endoscopy and esophagography. Histopathological examination of the esophageal tissues revealed that spindle-shaped α-smooth muscle actin (SMA)-positive myofibroblasts arranged in a parallel fashion and extending horizontally were identified at the ulcer bed one week after the ESD, and increased contributing to formation of the stenotic luminal ridge covered with the regenerated epithelium three weeks after the ESD. The proper muscle layer of the stricture site was thinned with some myocytes which seemingly showed transition to the myofibroblast layer. By contrast, for the pig with steroid injection, esophageal stricture formation was not evident with limited appearance of the spindle-shaped myofibroblasts, instead, appearance of stellate or polygocal SMA-positive stromal cells arranged haphazardly in the persistent granulation tissue of the ulcer site.

Conclusions

Proliferation of spindle-shaped myofibroblasts arranged in a parallel fashion is likely to play an important role in stricture formation after circumferential mucosal defects by esophageal ESD, which may be related to the thinning of the proper muscle layer in the healing course of the defects. Local steroid injection seems to be effective to prevent the stricture through the modification of this process.

Management of complications associated with endoscopic submucosal dissection/ endoscopic mucosal resection for esophageal cancer

Endoscopic resection of early esophageal cancer (EEC) is an established therapy in Japan and is increasingly becoming accepted and used regularly in other countries. Endoscopic submucosal dissection (ESD), an application of conventional endoscopic mucosal resection (EMR), has been developed to allow the resection of larger lesions in an en bloc manner; the earliest results so far have been promising even in EEC. ESD allows precise assessment of the histopathological curability of resected specimens, reducing local recurrence. However, ESD has relatively high complication rates; notification of perforation risk is essential especially in the esophagus. Bleeding during ESD can be managed by endoscopic closure with endoclips, and delayed bleeding is rare. Esophageal stricture following semicircular or complete circular esophageal ESD was relatively frequent even when treated by multiple pre-emptive endoscopic balloon dilation. Endoscopic triamcinolone injection, temporal stenting and innovative transplantation of autologous tissue-engineered epithelial cell sheets have shown promising results for the prevention of luminal stricture following semicircular esophageal ESD. In cases of circumferential ESD, however, giving oral prednisolone can offer a unique treatment option for the prevention of intractable post-procedural stricture of the esophagus.

Cell sheet technology for regeneration of esophageal mucosa

The progress of tissue-engineering technology has realized development of new therapies to treat various disorders by using cultured cells. Cell- and tissue-based therapies have been successfully applied to human patients, and several tissue-engineered products have been approved by the regulatory agencies and are commercially available. In the review article, we describe our experience of development and clinical application of cell sheet-based regenerative medicine. Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have been shown to be useful for removal of gastrointestinal neoplasms with less invasiveness compared with open surgery, especially in esophageal surgery. However, postoperative inflammation and stenosis are major complications observed after intensive mucosal resection. Therefore, we have developed novel regenerative medicine to prevent such complications and promote wound healing of esophageal mucosa after EMR or ESD. Transplantable oral mucosal epithelial cell sheets were fabricated from patients’ own oral mucosa. Immediately after EMR or ESD, fabricated autologous cell sheets were endoscopically transplanted to the ulcer sites. We performed a preclinical study with a canine model. In human clinical settings, cell culture and cell sheet fabrication were performed in clean rooms according to good manufacturing practice guidelines, and pharmaceutical drugs were used as supplements to culture medium in place of research regents used in animal study. We believe that cell-based regenerative medicine would be useful to improve quality of life of patients after EMR or ESD.

Fabricated autologous epidermal cell sheets for the prevention of esophageal stricture after circumferential ESD in a porcine model

BACKGROUND

Endoscopic submucosal dissection (ESD) is an accepted treatment for early esophageal carcinoma. However, resection of a large mucosal area, as with circumferential ESD, induces severe stricture formation.

OBJECTIVE

To evaluate the efficacy of cultured autologous epidermal cell sheets to prevent severe esophageal constriction after circumferential ESD.

DESIGN

Animal study.

SETTING

University institute.

INTERVENTION

Eight pigs underwent circumferential esophageal ESD while under general anesthesia. In 4 pigs, fabricated autologous epidermal cell sheets were endoscopically transplanted to the central ESD sites immediately after the ESD. The other 4 pigs underwent circumferential ESD only. Necropsy and histological assessment were performed at 1 and 2 weeks post-ESD.

MAIN OUTCOME MEASUREMENTS

Weight gain, degree of mucosal constriction, and histological assessments.

RESULTS

All pigs in the control group showed severe esophageal constriction after 2 weeks. The control and transplanted groups had weight gains of -10.3% and 0.3% (P = .03), respectively, and the mean degrees of constriction were 88% and 56% (P < .01), respectively. Early re-epithelialization and mild fibrosis in the muscularis were observed in the transplanted group.

LIMITATIONS

Animal study, small sample size.

CONCLUSIONS

Fabricated autologous skin epidermal cell sheets would be useful in preventing severe esophageal constriction after circumferential ESD.

Stricture prevention after extended circumferential endoscopic mucosal resection by injecting autologous keratinocytes in the sheep esophagus

BACKGROUND

During the past decades, endoscopic mucosal resection (EMR) has been developed to treat early intramucosal esophageal cancers and dysplastic Barrett's esophagus. The primary drawback of this method is severe postsurgical esophageal stricture formation. The purpose of this preclinical study was to assess strategies for prevention of this major complication by injecting autologous keratinocytes in the EMR mucosal defect in the sheep model.

METHODS

Circumferential, 6-cm-long EMRs were performed in the esophagus of nine sheep. Autologous keratinocytes were harvested 2 weeks before EMR and cultured. Circumferential resection consisted of two opposite hemicircumferential mucosectomies allowing a widespread resection of 24 cm(2). Immediately after EMR, autologous keratinocytes were endoscopically injected in the mucosal defect. Animals were sacrificed after 6 months.

RESULTS

Circumferential EMRs were successfully performed in all animals. There were no intra- or postoperative complications. None of the animals developed strictures. All animals were sacrificed at 6 months as planned. Histological examinations showed fibrotic changes in 10 % (range 0-25 %) of the circumferential muscularis propria interna layer and 7.2 % (range 0-25 %) in the muscularis propria externa layer at the midportion of the EMR. No circumferential transmural fibrosis was identified.

CONCLUSIONS

Prevention of stricture formation after extensive (6-cm long) circumferential EMR of the sheep esophagus can be achieved by injecting autologous keratinocytes into the wound of the resected mucosal segment.

Prevention of esophageal stricture after endoscopic submucosal dissection using tissue-engineered cell sheets

BACKGROUND & AIMS

The use of esophageal endoscopic submucosal dissection (ESD) to remove superficial esophageal neoplasms is gradually becoming more common in Japan. However, large-scale esophageal ESD often requires subsequent multiple balloon dilations to prevent postoperative esophageal stricture. We investigated the safety and efficacy of endoscopic transplantation of tissue-engineered autologous oral mucosal epithelial cell sheets in preventing formation of strictures after ESD.

METHODS

We performed an open-label, single-arm, single-institute study. We collected specimens of oral mucosal tissue from 9 patients with superficial esophageal neoplasms. Epithelial cell sheets were fabricated ex vivo by culturing isolated cells for 16 days on temperature-responsive cell culture surfaces. After a reduction in temperature, these sheets were endoscopically transplanted directly to the ulcer surfaces of patients who had just undergone ESD. All patients were monitored by endoscopy once a week until epithelialization was complete.

RESULTS

Autologous cell sheets were successfully transplanted to ulcer surfaces using an endoscope. Complete re-epithelialization occurred within a median time of 3.5 weeks. No patients experienced dysphagia, stricture, or other complications following the procedure, except for one patient who had a full circumferential ulceration that expanded to the esophagogastric junction.

CONCLUSIONS

Sutureless, endoscopic transplantation of carrier-free cell sheets composed of autologous oral mucosal epithelial cells safely and effectively promotes re-epithelialization of the esophagus after ESD. Patients in this study did not experience any serious complications. This procedure might be used to prevent stricture formation following ESD and improve patients' quality of life. Further study will be needed to show that stricture formation can be prevented.