Esophagus and regenerative medicine

The vascular niche in next generation microphysiological systems

In recent years, microphysiological system (MPS, also known as, organ-on-a-chip or tissue chip) platforms have emerged with great promise to improve the predictive capacity of preclinical modeling thereby reducing the high attrition rates when drugs move into trials. While their designs can vary quite significantly, in general MPS are bioengineered in vitro microenvironments that recapitulate key functional units of human organs, and that have broad applications in human physiology, pathophysiology, and clinical pharmacology. A critical next step in the evolution of MPS devices is the widespread incorporation of functional vasculature within tissues. The vasculature itself is a major organ that carries nutrients, immune cells, signaling molecules and therapeutics to all other organs. It also plays critical roles in inducing and maintaining tissue identity through expression of angiocrine factors, and in providing tissue-specific milieus (i.e., the vascular niche) that can support the survival and function of stem cells. Thus, organs are patterned, maintained and supported by the vasculature, which in turn receives signals that drive tissue specific gene expression. In this review, we will discuss published vascularized MPS platforms and present considerations for next-generation devices looking to incorporate this critical constituent. Finally, we will highlight the organ-patterning processes governed by the vasculature, and how the incorporation of a vascular niche within MPS platforms will establish a unique opportunity to study stem cell development.

Identification of four genes and biological characteristics of esophageal squamous cell carcinoma by integrated bioinformatics analysis

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) has become one of the most serious diseases affecting populations worldwide and is the primary subtype of esophageal cancer (EC). However, the molecular mechanisms governing the development of ESCC have not been fully elucidated.

METHODS

The robust rank aggregation method was performed to identify the differentially expressed genes (DEGs) in six datasets (GSE17351, GSE20347, GSE23400, GSE26886, GSE38129 and GSE77861) from the Gene Expression Omnibus (GEO). The Search Tool for the Retrieval of Interacting Genes (STRING) database was utilized to extract four hub genes from the protein-protein interaction (PPI) network. Module analysis and disease free survival analysis of the four hub genes were performed by Cytoscape and GEPIA. The expression of hub genes was analyzed by GEPIA and the Oncomine database and verified by real-time quantitative PCR (qRT-PCR).

RESULTS

In total, 720 DEGs were identified in the present study; these genes consisted of 302 upregulated genes and 418 downregulated genes that were significantly enriched in the cellular component of the extracellular matrix part followed by the biological process of the cell cycle phase and nuclear division. The primary enriched pathways were hsa04110:Cell cycle and hsa03030:DNA replication. Four hub genes were screened out, namely, SPP1, MMP12, COL10A1 and COL5A2. These hub genes all exhibited notably increased expression in ESCC samples compared with normal samples, and ESCC patients with upregulation of all four hub genes exhibited worse disease free survival.

CONCLUSIONS

SPP1, MMP12, COL10A1 and COL5A2 may participate in the tumorigenesis of ESCC and demonstrate the potential to serve as molecular biomarkers in the early diagnosis of ESCC. This study may help to elucidate the molecular mechanisms governing ESCC and facilitate the selection of targets for early treatment and diagnosis.

Trends in 3D bioprinting for esophageal tissue repair and reconstruction

In esophageal pathologies, such as esophageal atresia, cancers, caustic burns, or post-operative stenosis, esophageal replacement is performed by using parts of the gastrointestinal tract to restore nutritional autonomy. However, this surgical procedure most often does not lead to complete functional recovery and is instead associated with many complications resulting in a decrease in the quality of life and survival rate. Esophageal tissue engineering (ETE) aims at repairing the defective esophagus and is considered as a promising therapeutic alternative. Noteworthy progress has recently been made in the ETE research area but strong challenges remain to replicate the structural and functional integrity of the esophagus with the approaches currently being developed. Within this context, 3D bioprinting is emerging as a new technology to facilitate the patterning of both cellular and acellular bioinks into well-organized 3D functional structures. Here, we present a comprehensive overview of the recent advances in tissue engineering for esophageal reconstruction with a specific focus on 3D bioprinting approaches in ETE. Current biofabrication techniques and bioink features are highlighted, and these are discussed in view of the complexity of the native esophagus that the designed substitute needs to replace. Finally, perspectives on recent strategies for fabricating other tubular organ substitutes via 3D bioprinting are discussed briefly for their potential in ETE applications.

Extracellular Matrix Bioscaffolds for Building Gastrointestinal Tissue

Regenerative medicine is a rapidly advancing field that uses principles of tissue engineering, developmental biology, stem cell biology, immunology, and bioengineering to reconstruct diseased or damaged tissues. Biologic scaffolds composed of extracellular matrix have shown great promise as an inductive substrate to facilitate the constructive remodeling of gastrointestinal (GI) tissue damaged by neoplasia, inflammatory bowel disease, and congenital or acquired defects. The present review summarizes the preparation and use of extracellular matrix scaffolds for bioengineering of the GI tract, identifies significant advances made in regenerative medicine for the reconstruction of functional GI tissue, and describes an emerging therapeutic approach.

The extracellular matrix of the gastrointestinal tract: a regenerative medicine platform

The synthesis and secretion of components that constitute the extracellular matrix (ECM) by resident cell types occur at the earliest stages of embryonic development, and continue throughout life in both healthy and diseased physiological states. The ECM consists of a complex mixture of insoluble and soluble functional components that are arranged in a tissue-specific 3D ultrastructure, and it regulates numerous biological processes, including angiogenesis, innervation and stem cell differentiation. Owing to its composition and influence on embryonic development, as well as cellular and organ homeostasis, the ECM is an ideal therapeutic substrate for the repair of damaged or diseased tissues. Biologic scaffold materials that are composed of ECM have been used in various surgical and tissue-engineering applications. The gastrointestinal (GI) tract presents distinct challenges, such as diverse pH conditions and the requirement for motility and nutrient absorption. Despite these challenges, the use of homologous and heterologous ECM bioscaffolds for the focal or segmental reconstruction and regeneration of GI tissue has shown promise in early preclinical and clinical studies. This Review discusses the importance of tissue-specific ECM bioscaffolds and highlights the major advances that have been made in regenerative medicine strategies for the reconstruction of functional GI tissues.

Emerging Implications for Extracellular Matrix-Based Technologies in Vascularized Composite Allotransplantation

Despite recent progress in vascularized composite allotransplantation (VCA), limitations including complex, high dose immunosuppression regimens, lifelong risk of toxicity from immunosuppressants, acute and most critically chronic graft rejection, and suboptimal nerve regeneration remain particularly challenging obstacles restricting clinical progress. When properly configured, customized, and implemented, biomaterials derived from the extracellular matrix (ECM) retain bioactive molecules and immunomodulatory properties that can promote stem cell migration, proliferation and differentiation, and constructive functional tissue remodeling. The present paper reviews the emerging implications of ECM-based technologies in VCA, including local immunomodulation, tissue repair, nerve regeneration, minimally invasive graft targeted drug delivery, stem cell transplantation, and other donor graft manipulation.

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.

Regenerative Medicine Strategies for Esophageal Repair

Pathologies that involve the structure and/or function of the esophagus can be life-threatening. The esophagus is a complex organ comprising nonredundant tissue that does not have the ability to regenerate. Currently available interventions for esophageal pathology have limited success and are typically associated with significant morbidity. Hence, there is currently an unmet clinical need for effective methods of esophageal repair. The present article presents a review of esophageal disease along with the anatomic and functional consequences of each pathologic process, the shortcomings associated with currently available therapies, and the latest advancements in the field of regenerative medicine with respect to strategies for esophageal repair from benchtop to bedside.

Decellularization and cell seeding of whole liver biologic scaffolds composed of extracellular matrix

The definitive treatment for patients with end-stage liver disease is orthotropic transplantation. However, this option is limited by the disparity between the number of patients needing transplantation and the number of available livers. This issue is becoming more severe as the population ages and as the number of new cases of end-stage liver failure increases. Patients fortunate enough to receive a transplant are required to receive immunosuppressive therapy and must live with the associated morbidity. Whole organ engineering of the liver may offer a solution to this liver donor shortfall. It has been shown that perfusion decellularization of a whole allogeneic or xenogeneic liver generates a three-dimensional ECM scaffold with intact macro and micro architecture of the native liver. A decellularized liver provides an ideal transplantable scaffold with all the necessary ultrastructure and signaling cues for cell attachment, differentiation, vascularization, and function. In this review, an overview of complementary strategies for creating functional liver grafts suitable for transplantation is provided. Early milestones have been met by combining stem and progenitor cells with increasingly complex scaffold materials and culture conditions.

Seamless vascularized large-diameter tubular collagen scaffolds reinforced with polymer knittings for esophageal regenerative medicine

A clinical demand exists for alternatives to repair the esophagus in case of congenital defects, cancer, or trauma. A seamless biocompatible off-the-shelf large-diameter tubular scaffold, which is accessible for vascularization, could set the stage for regenerative medicine of the esophagus. The use of seamless scaffolds eliminates the error-prone tubularization step, which is necessary when emanating from flat scaffolds. In this study, we developed and characterized three different types of seamless tubular scaffolds, and evaluated in vivo tissue compatibility, including vascularization by omental wrapping. Scaffolds (luminal Ø ∼ 1.5 cm) were constructed using freezing, lyophilizing, and cross-linking techniques and included (1) single-layered porous collagen scaffold, (2) dual-layered (porous+dense) collagen scaffold, and (3) hybrid scaffold (collagen+incorporated polycaprolacton knitting). The latter had an ultimate tensile strength comparable to a porcine esophagus. To induce rapid vascularization, scaffolds were implanted in the omentum of sheep using a wrapping technique. After 6 weeks of biocompatibility, vascularization, calcification, and hypoxia were evaluated using immunohistochemistry. Scaffolds were biocompatible, and cellular influx and ingrowth of blood vessels were observed throughout the whole scaffold. No calcification was observed, and slight hypoxic conditions were detected only in the direct vicinity of the polymer knitting. It is concluded that seamless large-diameter tubular collagen-based scaffolds can be constructed and vascularized in vivo. Such scaffolds provide novel tools for esophageal reconstruction.

Regenerative medicine technology applied to gastroenterology: Current status and future perspectives

This special issue of World Journal of Gastroenterology has been conceived to illustrate to gastroenterology operators the role that regenerative medicine (RM) will have in the progress of gastrointestinal (GI) medicine. RM is a multidisciplinary field aiming to replace, regenerate or repair diseased tissues or organs. The past decade has been marked by numerous ground-breaking achievements that led experts in the field to manufacture functional substitutes of relatively simple organs. This progress is paving the ground for investigations that aims to the bioengineering and regeneration of more complex organs like livers, pancreas and intestine. In this special issue, the reader will be introduced, hand-in-hand, to explore the field of RM and will be educated on the progress, pitfalls and promise of RM technologies as applied to GI medicine.