Generation of Human Stem Cell-Derived Pancreatic Organoids (POs) for Regenerative Medicine

Application and challenge of pancreatic organoids in therapeutic research

The in-vivo non-human primate animal and in-vitro cell disease models play a crucial part in the study of the mechanisms underlying the occurrence and development of pancreatic diseases, but with increasingly prominent limitations with in-depth research. Organoids derived from human pluripotent and adult stem cells resemble human in-vivo organs in their cellular composition, spatial tissue structure and physiological function, making them as an advantageous research tool. Up until now, numerous human organoids, including pancreas, have been effectively developed, demonstrating significant potential for research in organ development, disease modeling, drug screening, and regenerative medicine. However, different from intestine, liver and other organs, the pancreas is the only special organ in the human body, consisting of an exocrine gland and an endocrine gland. Thus, the development of pancreatic organoid technology faces greater challenges, and how to construct a composite pancreatic organoid with exocrine and endocrine gland is still difficult in current research. By reviewing the fundamental architecture and physiological role of the human pancreas, along with the swiftly developing domain of pancreatic organoids, we summarize the method and characteristics of human pancreatic organoids, and its application in modeling pancreatic diseases, as a platform for individualized drug screening and in regenerative medicine study. As the first comprehensive review that focus on the pharmacological study of human pancreatic organoid, the review hopes to help scholars to have a deeper understanding in the study of pancreatic organoid.

Advancement of Organoid Technology in Regenerative Medicine

Purpose

Organoids are three-dimensional cultures of stem cells in an environment similar to the body's extracellular matrix. This is also a novel development in the realm of regenerative medicine. Stem cells can begin to develop into 3D structures by modifying signaling pathways. To form organoids, stem cells are transplanted into the extracellular matrix. Organoids have provided the required technologies to reproduce human tissues. As a result, it might be used in place of animal models in scientific study. The key goals of these investigations are research into viral and genetic illnesses, malignancies, and extracellular vesicles, pharmaceutical discovery, and organ transplantation. Organoids can help pave the road for precision medicine through genetic editing, pharmaceutical development, and cell therapy.

Methods

PubMed, Google Scholar, and Scopus were used to search for all relevant papers written in English (1907-2021). The study abstracts were scrutinized. Studies on the use of stem-cell-derived organoids in regenerative medicine, organoids as 3D culture models for EVs analysis, and organoids for precision medicine were included. Articles with other irrelevant aims, meetings, letters, commentaries, congress and conference abstracts, and articles with no available full texts were excluded.

Results

According to the included studies, organoids have various origins, types, and applications in regenerative and precision medicine, as well as an important role in studying extracellular vesicles.

Conclusion

Organoids are considered a bridge that connects preclinical studies to clinical ones. However, the lack of a standardized protocol and other barriers addressed in this review, hinder the vast use of this technology.

Lay Summary

Organoids are 3D stem cell propagations in biological or synthetic scaffolds that mimic ECM to allow intercellular or matrix-cellular crosstalk. Because these structures are similar to organs in the body, they can be used as research models. Organoids are medicine's future hope for organ transplantation, tumor biobank formation, and the development of precision medicine. Organoid models can be used to study cell-to-cell interactions as well as effective factors like inflammation and aging. Bioengineering technologies are also used to define the size, shape, and composition of organoids before transforming them into precise structures. Finally, the importance of organoid applications in regenerative medicine has opened a new window for a better understanding of biological research, as discussed in this study.

Suppression of transient receptor potential melastatin 7 regulates pluripotency, proliferation, and differentiation of mouse embryonic stem cells via mechanistic target of rapamycin-extracellular signal-regulated kinase activation

Mouse embryonic stem cells (mESCs) are a widely used model for their diverse availability in studying early embryonic development and their application in regenerative treatment of various intractable diseases. Transient receptor potential melastatin 7 (Trpm7) regulates Ca²⁺ as a nonselective ion channel and is essential for early embryonic development; however, the precise role of Trpm7 in mESCs has not been clearly elucidated. In this study, we showed that the inhibition of Trpm7 affects the pluripotency and self-renewal of mESCs. We found that short hairpin RNA (shRNA)-mediated suppression of Trpm7 resulted in decreased expression of transcriptional regulators, Oct4 and Sox2, which maintain stemness in mESCs. In addition, Trpm7 knockdown led to alterations in the basic properties of mESCs, such as decreased proliferation, cell cycle arrest at the G0/G1 phase, and increased apoptosis. Furthermore, embryoid body (EB) formation and teratoma formation assays revealed abnormal regulation of differentiation due to Trpm7 knockdown, including the smaller size of EBs, elevated ectodermal differentiation, and diminished endodermal and mesodermal differentiation. We found that EB Day 7 samples displayed decreased intracellular Ca²⁺ levels compared to those of the scrambled group. Finally, we identified that these alterations induced by Trpm7 knockdown occurred due to decreased phosphorylation of mechanistic target of rapamycin (mTOR) and subsequent activation of extracellular signal-regulated kinase (ERK) in mESCs. Our findings suggest that Trpm7 could be a novel regulator for maintaining stemness and modulating the differentiation of mESCs.

Development of islet organoids from human induced pluripotent stem cells in a cross-linked collagen scaffold

Islets organoids would have value in the cell replacement therapy for diabetes apart from usual personalized drug screening routes. Generation of a large number of Islets like clusters, with ability to respond to glucose stimulation appears to be an ideal choice. In this study we have generated islet organoids with the ability to respond to glucose stimulation by insulin release. The source of the cells was an iPSC cell line differentiated into the pancreatic progenitors. These cells were assembled in matrigel or cross-linked collagen scaffold and compared for their efficacy to release insulin upon stimulation with glucose. The assembled organoids were examined by immunohistochemistry and expression of the relevant marker genes. The organoids showed expression of islet like markers in both - matrigel and crosslinked collagen scaffold. The islet organoids in both the cases showed release of insulin upon stimulation with glucose. The crosslinked collagen scaffold is quite stable and supports islet cells growth and function.

Xenogeneic stem cell transplantation: Research progress and clinical prospects

Organ transplantation is the ultimate treatment for end-stage diseases such as heart and liver failure. However, the severe shortage of donor organs has limited the organ transplantation progress. Xenogeneic stem cell transplantation provides a new strategy to solve this problem. Researchers have shown that xenogeneic stem cell transplantation has significant therapeutic effects and broad application prospects in treating liver failure, myocardial infarction, advanced type 1 diabetes mellitus, myelosuppression, and other end-stage diseases by replacing the dysfunctional cells directly or improving the endogenous regenerative milieu. In this review, the sources, problems and solutions, and potential clinical applications of xenogeneic stem cell transplantation will be discussed.

Evolution of organoid technology: Lessons learnt in Co-Culture systems from developmental biology

In recent years, the development of 3D organoids has opened new avenues of investigation into development, physiology, and regenerative medicine. Organoid formation and the process of organogenesis share common developmental pathways; thus, our knowledge of developmental biology can help model the complexity of different organs to refine organoids into a more sophisticated platform. The developmental process is strongly dependent on complex networks and communication of cell-cell and cell-matrix interactions among different cell populations and their microenvironment, during embryogenesis. These interactions affect cell behaviors such as proliferation, survival, migration, and differentiation. Co-culture systems within the organoid technology were recently developed and provided the highly physiologically relevant systems. Supportive cells including various types of endothelial and stromal cells provide the proper microenvironment, facilitate organoid assembly, and improve vascularization and maturation of organoids. This review discusses the role of the co-culture systems in organoid generation, with a focus on how knowledge of developmental biology has directed and continues to shape the development of more evolved 3D co-culture system-derived organoids.

Establishment of universal human embryonic stem cell lines

The potential application of human embryonic stem cells in regenerative medicine using cell, tissue or organ transplantation has aroused great interest. However, HLA incompatibility between donor cells or tissues and the recipient is a primary obstacle to the use of unmatched human embryonic stem cells and their derivatives as donor 'grafts' for patient treatment without some form of immunosuppressive therapy. This is because, for most tissues, which express HLA Class I antigens, the recipient patient's immune system will recognize the difference between their and the donor's HLA types, leading to graft rejection in the absence of immunosuppressive therapy. One approach to overcoming this obstacle and enabling the use of a single or limited range of suitably selected human embryonic stem cells and their derivatives without needing extensive HLA matching is to use gene-editing technology to establish a universally or widely HLA compatible human embryonic stem cell line, thereby providing a potentially unlimited source of cells for future cell, tissue or organ transplantation. This article reviews current strategies and methods for establishing such universal or near universally HLA compatible human embryonic stem cell lines.

Longitudinal proteomics analysis in the immediate microenvironment of islet allografts during progression of rejection

The applicability and benefits of pancreatic islet transplantation are limited due to various issues including the need to avoid immune-mediated rejection. Here, we used our experimental platform of allogeneic islet transplant in the anterior chamber of the eye (ACE-platform) to longitudinally monitor the progress of rejection in mice and obtain aqueous humor samples representative of the microenvironment of the graft for accurately-timed proteomic analyses. LC-MS/MS-based proteomics performed on such mass-limited samples (~5 μL) identified a total of 1296 proteins. Various analyses revealed distinct protein patterns associated with the mounting of the inflammatory and immune responses and their evolution with the progression of the rejection. Pathway analyses indicated predominant changes in cytotoxic functions, cell movement, and innate and adaptive immune responses. Network prediction analyses revealed transition from humoral to cellular immune response and exacerbation of pro-inflammatory signaling. One of the proteins identified by this localized proteomics as a candidate biomarker of islet rejection, Cystatin 3, was further validated by ELISA in the aqueous humor. This study provides (1) experimental evidence demonstrating the feasibility of longitudinal localized proteomics using small aqueous humor samples and (2) proof-of-concept for the discovery of biomarkers of impending immune attack from the immediate local microenvironment of ACE-transplanted islets. SIGNIFICANCE: The combination of the ACE-platform and longitudinal localized proteomics offers a powerful approach to biomarker discovery during the various stages of immune reactions mounted against transplanted tissues including pancreatic islets. It also supports proteomics-assisted drug discovery and development efforts aimed at preventing rejection through efficacy assessment of new agents by noninvasive and longitudinal graft monitoring.

Cell therapy for type 1 diabetes

INTRODUCTION

Type 1 diabetes (T1D) is a lifelong condition resulting from autoimmune destruction of insulin-producing β-cells. Islet or whole-pancreas transplantation is limited by the shortage of donors and need for chronic immune suppression. Novel strategies are needed to prevent β-cell loss and to rescue production of endogenous insulin.

AREAS COVERED

This review covers the latest advances in cell-based therapies for the treatment and prevention of T1D. Topics include adoptive transfer of cells with increased immunoregulatory potential for β-cell protection, and β-cell replacement strategies such as generation of insulin-producing β-like cells from unlimited sources.

EXPERT OPINION

Cell therapy provides an opportunity to prevent or reverse T1D. Adoptive transfer of autologous cells having enhanced immunomodulatory properties can suppress autoimmunity and preserve β-cells. Such therapies have been made possible by a combination of genome-editing techniques and transplantation of tolerogenic cells. In-vitro modified autologous hematopoietic stem cells and tolerogenic dendritic cells may protect endogenous and newly generated β-cells from a patient's autoimmune response without hampering immune surveillance for infectious agents and malignant cellular transformations. However, methods to generate cells that meet quality and safety standards for clinical applications require further refinement.