Engineered muscle from micro-channeled PEG scaffold with magnetic Fe3O4 fixation towards accelerating esophageal muscle repair

Engineered scaffolds are used for repairing damaged esophagus to allow the precise alignment and movement of smooth muscle for peristalsis. However, most of these scaffolds focus solely on inducing cell alignment through directional apparatus, often overlooking the promotion of muscle tissue formation and causing reduced esophageal muscle repair effectiveness. To address this issue, we first introduced aligned nano-ferroferric oxide (Fe3O4) assemblies on a micropatterned poly(ethylene glycol) (PEG) hydrogel to form micro-/nano-stripes. Further modification using a gold coating was found to enhance cellular adhesion, orientation and organization within these micro-/nano-stripes, which consequently prevented excessive adhesion of smooth muscle cells (SMCs) to the thin PEG ridges, thereby effectively confining the cells to the Fe3O4-laid channels. This architectural design promotes the alignment of the cytoskeleton and elongation of actin filaments, leading to the organized formation of muscle bundles and a tendency for SMCs to adopt synthetic phenotypes. Muscle patches are harvested from the micro-/nano-stripes and transplanted into a rat esophageal defect model. In vivo experiments demonstrate the exceptional viability of these muscle patches and their ability to accelerate the regeneration of esophageal tissue. Overall, this study presents an efficient strategy for constructing muscle patches with directional alignment and muscle bundle formation of SMCs, holding significant promise for muscle tissue regeneration.

Research on essential performance of oxidized chitosan-crosslinked acellular porcine aorta modified with bioactive SCPP/DOPA for esophageal scaffold with enhanced mechanical strength, biocompatibility and anti-inflammatory

Acellular porcine aorta (APA) is an excellent candidate for an implanted scaffold but needs to be modified with appropriate cross-linking agent to increase its mechanical property and storage time in vitro as well as to give itself some bioactivities and eliminate its antigenicity for acting as a novel esophageal prosthesis. In this paper, a polysaccharide crosslinker (oxidized chitosan, OCS) was prepared by oxidizing chitosan using NaIO₄ and further used to fix APA to prepare a novel esophageal prosthesis (scaffold). And then the surface modification with dopamine (DOPA) and strontium-doped calcium polyphosphate (SCPP) were performed one after another to prepare DOPA/OCS-APA and SCPP-DOPA/OCS-APA to improve the biocompatibility and inhibit inflammation of the scaffolds. The results showed that the OCS with a feeding ratio of 1.5:1.0 and a reaction time of 24 h had a suitable molecular weight and oxidation degree, almost no cytotoxicity and good cross-linking effect. Compared with glutaraldehyde (GA) and genipin (GP), OCS-fixed APA could provide a more suitable microenvironment for cell proliferation. The vital cross-linking characteristics and cytocompatibility of SCPP-DOPA/OCS-APA were evaluated. Results suggested that SCPP-DOPA/OCS-APA exhibited suitable mechanical properties, excellent resistance to enzymatic degradation/acid degradation, suitable hydrophilicity, and the ability to promote the proliferation of Human normal esophageal epithelial cells (HEECs) and inhibit inflammation in vitro. In vivo tests also confirmed that SCPP-DOPA/OCS-APA could diminish the immunological response to samples and had a positive impact on bioactivity and anti-inflammatory. In conclusion, SCPP-DOPA/OCS-APA could act as an effective, bioactive artificial esophageal scaffold and be expected to be used for clinical in the future.

Esophageal wound healing by aligned smooth muscle cell-laden nanofibrous patch

The esophagus exhibits peristalsis via contraction of circularly and longitudinally aligned smooth muscles, and esophageal replacement is required if there is a critical-sized wound. In this study, we proposed to reconstruct esophageal tissues using cell electrospinning (CE), an advanced technique for encapsulating living cells into fibers that allows control of the direction of fiber deposition. After treatment with transforming growth factor-β, mesenchymal stem cell-derived smooth muscle cells (SMCs) were utilized for cell electrospinning or three-dimensional bioprinting to compare the effects of aligned micropatterns on cell morphology. CE resulted in SMCs with uniaxially arranged and elongated cell morphology with upregulated expression levels of SMC-specific markers, including connexin 43, smooth muscle protein 22 alpha (SM22α), desmin, and smoothelin. When SMC-laden nanofibrous patches were transplanted into a rat esophageal defect model, the SMC patch promoted regeneration of esophageal wounds with an increased number of newly formed blood vessels and enhanced the SMC-specific markers of SM22α and vimentin. Taken together, CE with its advantages, such as guidance of highly elongated, aligned cell morphology and accelerated SMC differentiation, can be an efficient strategy to reconstruct smooth muscle tissues and treat esophageal perforation.

Gelatin-grafted tubular asymmetric scaffolds promote ureteral regeneration via activation of the integrin/Erk signaling pathway

Introduction: The repair of a diseased ureter is an urgent clinical issue that needs to be solved. A tissue-engineered scaffold for ureteral replacement is currently insufficient due to its incompetent bioactivity, especially in long-segment abnormalities. The primary reason is the failure of urothelialization on scaffolds. Methods: In this work, we investigated the ability of gelatin-grafted tubular scaffold in ureteral repairment and its related biological mechanism. We designed various porous asymmetric poly (L-lactic acid) (PLLA)/poly (L-lactide-co-e-caprolactone) (PLCL) tubes with a thermally induced phase separation (TIPS) method via a change in the ratio of solvents (named PP). To regulate the phenotype of urothelial cells and ureteral reconstruction, gelatin was grafted onto the tubular scaffold using ammonolysis and glutaraldehyde crosslinking (named PP-gel). The in vitro and in vivo experiments were performed to test the biological function and the mechanism of the scaffolds. Results and Discussion: The hydrophilicity of the scaffold significantly increased after gelatin grafting, which promoted the adhesion and proliferation of urothelial cells. Through subcutaneous implantation in rats, PP-gel scaffolds demonstrated good biocompatibility. The in vivo replacement showed that PP-gel could improve urothelium regeneration and maintain renal function after the ureter was replaced with an ∼4 cm-long PP-gel tube using New Zealand rabbits as the experimental animals. The related biologic mechanism of ureteral reconstruction was detected in detail. The gelatin-grafted scaffold upgraded the integrin α6/β4 on the urothelial cell membrane, which phosphorylates the focal adhesion kinase (FAK) and enhances urothelialization via the MAPK/Erk signaling pathway. Conclusion: All these results confirmed that the PP46-gel scaffold is a promising candidate for the constitution of an engineered ureter and to repair long-segment ureteral defects.

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.

Development of Bio-artificial Esophageal Tissue Engineering Utilization for Circumferential Lesion Transplantation: A Narrative Review

The esophagus is the gastrointestinal tract's primary organ that transfers bolus into the stomach with peristaltic motion. Therefore, its lesions cause a significant disturbance in the nutrition and digestive system. Esophageal disease treatment sometimes requires surgical procedures that involve removal and circumferential full-thickness replacement. Unlike other organs, the esophagus has a limited regeneration ability and cannot be transplanted from donors. There are various methods of restoring the esophageal continuity; however, they are associated with certain flaws that lead to a non-functional recovery. As an exponentially growing science, tissue engineering has become a leading technique for the development of tissue replacement to repair damaged esophageal segments. Scaffold plays a significant role in the process of tissue engineering, as it acts as a template for the regeneration of growing tissue. A variety of scaffolds have been studied to replace the esophagus. Due to the many tissue quality challenges, the results are still inadequate and need to be improved. The success of esophageal tissue regeneration will finally depend on the scaffold's capability to mimic natural tissue properties and provide a qualified environment for regeneration. Thereby, scaffold fabrication techniques are fundamental. This article reviews the recent developments in esophageal tissue engineering for the treatment of circumferential lesions based on scaffold biomaterial engineering approaches.

Development and Prospect of Esophageal Tissue Engineering

Currently, patients with esophageal cancer, especially advanced patients, usually use autologous tissue for esophageal alternative therapy. However, an alternative therapy is often accompanied by serious complications such as ischemia and leakage, which seriously affect the prognosis of patients. Tissue engineering has been widely studied as one of the ideal methods for the treatment of esophageal cancer. In view of the complex multi-layer structure of the natural esophagus, how to use the tissue engineering method to design the scaffold with structure and function matching with the natural tissue is the principle that the tissue engineering method must follow. This article will analyze and summarize the construction methods, with or without cells, and repair effects of single-layer scaffold and multi-layer scaffold. Especially in the repair of full-thickness and circumferential esophageal defects, the flexible design method and the binding force between the layers of the scaffold are very important. In short, esophageal tissue engineering technology has broad prospects and plays a more and more important role in the treatment of esophageal diseases.

Esophageal defect repair by artificial scaffolds: a systematic review of experimental studies and proportional meta-analysis

BACKGROUND

The traditional technique of gastrointestinal reconstruction of the esophagus after esophagectomy presents plenty of complications. Hence, tissue engineering has been introduced as an effective artificial alternative with potentially fewer complications. Three types of esophageal scaffolds have been used in experimental studies so far. The aim of our meta-analysis is to present the postoperative outcomes after esophageal replacement with artificial scaffolds and the investigation of possible factors that affect these outcomes.

METHODS

The present proportional meta-analysis was designed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and A MeaSurement Tool to Assess systematic Reviews guidelines. We searched Medline, Scopus, Clinicaltrials.gov, EMBASE, Cochrane Central Register of Controlled Trials CENTRAL, and Google Scholar databases from inception until February 2020.

RESULTS

Overall, 32 studies were included that recruited 587 animals. The pooled morbidity after esophageal scaffold implantation was 53.4% (95% CI = 36.6-70.0%). The pooled survival interval was 111.1 days (95% CI = 65.5-156.8 days). Graft stenosis (46%), postoperative dysphagia (15%), and anastomotic leak (12%) were the most common complications after esophageal scaffold implantation. Animals that underwent an implantation of an artificial scaffold in the thoracic part of their esophagus presented higher survival rates than animals that underwent scaffold implantation in the cervical or abdominal part of their esophagus (P < 0.001 and P = 0.011, respectively).

CONCLUSION

Tissue engineering seems to offer an effective alternative for the repair of esophageal defects in animal models. Nevertheless, issues like graft stenosis and lack of motility of the esophageal scaffolds need to be addressed in future experimental studies before scaffolds can be tested in human trials.

Graft alignment impacts the regenerative response of skeletal muscle after volumetric muscle loss in a rat model

A key event in the etiology of volumetric muscle loss (VML) injury is the bulk loss of structural cues provided by the underlying extracellular matrix (ECM). To re-establish the lost cues, there is broad consensus within the literature supporting the utilization of implantable scaffolding. However, while scaffold based regenerative medicine strategies have shown potential, there remains a significant amount of outcome variability observed across the field. We suggest that an overlooked source of outcome variability is differences in scaffolding architecture. The goal of this study was to test the hypothesis that implant alignment has a significant impact on genotypic and phenotypic outcomes following the repair of VML injuries. Using a rat VML model, outcomes across three autograft implant treatment groups (aligned implants, 45° misaligned, and 90° misaligned) and two recovery time points (2 weeks and 12 weeks) were examined (n = 6-8/group). At 2 weeks post-repair there were no significant differences in muscle mass and torque recovery between the treatment groups, however we did observe a significant upregulation of MyoD (2.5 fold increase) and Pax7 (2 fold increase) gene expression as well as the presence of immature myofibers at the implant site for those animals repaired with aligned autografts. By 12 weeks post-repair, functional and structural differences between the treatment groups could be detected. Aligned autografts had significantly greater mass and torque recovery (77 ± 10% of normal) when compared to 45° and 90° misaligned autografts (64 ± 10% and 61 ± 11%, respectively). Examination of tissue structure revealed extensive fibrosis and a significant increase in non-contractile tissue area fraction for only those animals treated using misaligned autografts. When taken together, the results suggest that implant graft orientation has a significant impact on in-vivo outcomes and indicate that the effect of graft alignment on muscle phenotype may be mediated through genotypic changes to myogenesis and fibrosis at the site of injury and repair. STATEMENT OF SIGNIFICANCE: A key event in the etiology of volumetric muscle loss injury is the bulk loss of architectural cues provided by the underlying extracellular matrix. To re-establish the lost cues, there is broad consensus within the literature supporting the utilization of implantable scaffolding. Yet, although native muscle is a highly organized tissue with network and cellular alignment in the direction of contraction, there is little evidence within the field concerning the importance of re-establishing native architectural alignment. The results of this study suggest that critical interactions exist between implant and native muscle alignment cues during healing, which influence the balance between myogenesis and fibrosis. Specifically, it appears that alignment of implant architectural cues with native muscle cues is necessary to create a pro-myogenic environment and contractile force recovery. The results also suggest that misaligned cues may be pathological, leading to fibrosis and poor contractile force recovery.

Biological properties of a bionic scaffold for esophageal tissue engineering research

Polyurethane is a good matrix material with wide application prospects in tissue engineering because of its adjustable and mechanical properties. A novel biodegradable crosslinked poly(ester urethane) (CPU) with flexible poly(caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) components has been synthesized using a ferric iron catalyst in our laboratory. In the present study, to promote the interaction between the CPU material and cells, the material was superficially modified by silk fibroin (SF) grafting using an aminolysis and glutaraldehyde crosslinking method to achieve a biocompatible material, CPU-SF. Considering the esophageal-specific architecture, three types of scaffolds were fabricated. S1 was a CPU-SF channel (200 μm in diameter and 30 μm in depth with 30 μm of wall thickness) to support muscle regeneration; S2 was the decellularized matrix of the esophageal mucosa/submucosa obtained by enzyme treatment; and S3 was a combination of S1 and S2, aiming to promote esophageal regeneration with histological structure and function. The biological properties and functions of the materials and scaffolds were investigated by qualitative and quantitative analyses using scanning electron microscopy, immunofluorescence staining, cell adhesion and proliferation measurements, and western blotting technology. The results showed that esophageal smooth muscle cells (SMCs) and epithelial cells (ECs) were very well supported by the scaffolds. In particular, SMCs exhibited guided directional growth and ECs infiltrated the acellular mucosa with retained biological functions when co-cultured on the composite scaffold S3. These findings suggest that the composite bionic scaffold will be a good alternative for esophageal replacement.

Decellularized material as scaffolds for tissue engineering studies in long gap esophageal atresia

INTRODUCTION

Esophageal atresia refers to an anomaly in foetal development in which the esophagus terminates in a blind end. Whilst surgical correction is achievable in most patients, when a long gap is present it still represents a major challenge associated with higher morbidity and mortality. In this context, tissue engineering could represent a successful alternative to restore oesophageal function and structure. Naturally derived biomaterials made of decellularized tissues retain native extracellular matrix architecture and composition, providing a suitable bed for the anchorage and growth of relevant cell types. Areas covered: This review outlines the various strategies and challenges in esophageal tissue engineering, highlighting the evolution of ideas in the development of decellularized scaffolds for clinical use. It explores the interplay between clinical needs, ethical dilemmas, and manufacturing challenges in the development of a tissue engineered decellularized scaffold for oesophageal atresia. Expert opinion: Current progress on oesophageal tissue engineering has enabled effective repair of patch defects, whilst the development of a full circumferential construct remains a challenge. Despite the different approaches available and the improvements achieved, a gold standard for fully functional tissue engineered oesophageal constructs has not been defined yet.

Recovery from volumetric muscle loss injury: A comparison between young and aged rats

Termed volumetric muscle loss (VML), the bulk loss of skeletal muscle tissue either through trauma or surgery overwhelms the capacity for repair, leading to the formation of non-contractile scar tissue. The myogenic potential, along with other factors that influence wound repair are known to decline with age. In order to develop effective treatment strategies for VML injuries that are effective across a broad range of patient populations, it is necessary to understand how the response to VML injury is affected by aging. Towards this end, this study was conducted to compare the response of young and aged animal groups to a lower extremity VML injury. Young (3months, n=12) and aged (18months, n=8) male Fischer 344 rats underwent surgical VML injury of the tibialis anterior muscle. Three months after VML injury it was found that young TA muscle was on average 16% heavier than aged muscle when no VML injury was performed and 25% heavier when comparing VML treated young and aged animals (p<0.0001, p<0.0001). Peak contractile force for both the young and aged groups was found to decrease significantly following VML injury, producing 65% and 59% of the contralateral limbs' peak force, respectively (p<0.0001). However, there were no differences found for peak contractile force based on age, suggesting that VML affects muscle's ability to repair, regardless of age. In this study, we used the ratio of collagen I to MyoD expression as a metric for fibrosis vs. myogenesis. Decreasing fiber cross-sectional area with advancing age (p<0.005) coupled with the ratio of collagen I to MyoD expression, which increased with age, supports the thought that regeneration is impaired in the aged population in favor of fibrosis (p=0.0241). This impairment is also exacerbated by the contribution of VML injury, where a 77-fold increase in the ratio of collagen I to MyoD was observed in the aged group (p<0.0002). The aged animal model described in this study provides a tool for investigators exploring not only the development of VML injury strategies but also the effect of aging on muscle regeneration.