Microencapsulated Pig Islet Xenotransplantation as an Alternative Treatment of Diabetes

Research Progress on the Construction and Application of a Diabetic Zebrafish Model

Diabetes is a metabolic disease characterized by high blood glucose levels. With economic development and lifestyle changes, the prevalence of diabetes is increasing yearly. Thus, it has become an increasingly serious public health problem in countries around the world. The etiology of diabetes is complex, and its pathogenic mechanisms are not completely clear. The use of diabetic animal models is helpful in the study of the pathogenesis of diabetes and the development of drugs. The emerging vertebrate model of zebrafish has many advantages, such as its small size, large number of eggs, short growth cycle, simple cultivation of adult fish, and effective improvement of experimental efficiency. Thus, this model is highly suitable for research as an animal model of diabetes. This review not only summarizes the advantages of zebrafish as a diabetes model, but also summarizes the construction methods and challenges of zebrafish models of type 1 diabetes, type 2 diabetes, and diabetes complications. This study provides valuable reference information for further study of the pathological mechanisms of diabetes and the research and development of new related therapeutic drugs.

Micro-RNA-124-5p promotes insulin producing cell differentiation through regulating transcriptional factor NKX6.1

Aims

Differentiating human embryonic stem cells into pancreatic β cells has been proposed as a practical approach to managing diabetes. There have been several protocols attempting to generate β-like cells or insulin-producing cells (IPCs), but their low efficiency is a common issue. The expression level of Nkx6.1 is crucial for maintaining pancreatic β cell identity, while the proportion of PDX1 and Nkx6.1 double positive cells were not satisfied in the present protocols, leading to relative low efficiency in the differentiation into IPCs. This study aims to identify the mechanism underlying the regulation of Nkx6.1 during IPC differentiation and provide new insights for diabetes therapy.

Methods

In the current study, human embryonic stem cell (hESC) line H1 was used to perform IPC specifications. Immunofluorescence, flow cytometry, and qPCR were conducted to analyze gene expression. In addition, insulin and C-peptide were measured through glucose-stimulated insulin secretion (GSIS) assays and ELISA.

Results

We found that the transcription factor NKX6.1, a crucial inducer of early pancreatic development and IPC generation, was downregulated by micro-RNA-124-5p (miR-124-5p) in hESCs during IPC differentiation. Also, we observed that miR-124-5p was upregulated and bound to the 3’ untranslated region (3’ UTR) of NKX6.1 in pancreatic progenitor (PP), which subsequently suppressed PP differentiation. Moreover, inhibiting miR-124-5p induced the generation of IPCs.

Conclusion

The current study results demonstrated an important role for miR-124-5p in regulating NKX6.1 expression, which appears to be a practical strategy for producing IPCs.

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miR-124-5p is upregulated during the IPCs differentiation.

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Inhibition of miR-124-5p enhances Nkx6.1 expresssion.

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miR-124-5p promotes the specification of IPCs from hESCs.

The Current Status of Bioartificial Pancreas Devices

Type 1 diabetes mellitus is a common and highly morbid disease for which there is no cure. Treatment primarily involves exogenous insulin administration, and, under specific circumstances, islet or pancreas transplantation. However, insulin replacement alone fails to replicate the endocrine function of the pancreas and does not provide durable euglycemia. In addition, transplantation requires lifelong use of immunosuppressive medications, which has deleterious side effects, is expensive, and is inappropriate for use in adolescents. A bioartificial pancreas that provides total endocrine pancreatic function without immunosuppression is a potential therapy for treatment of type 1 diabetes. Numerous models are in development and take different approaches to cell source, encapsulation method, and device implantation location. We review current therapies for type 1 diabetes mellitus, the requirements for a bioartificial pancreas, and quantitatively compare device function.

Feasibility of Induced Pluripotent Stem Cell Therapies for Treatment of Type 1 Diabetes

IMPACT STATEMENT

This review of iPSCs to treat T1D provides a current assessment of the challenges and potential for this proposed new therapy.

Polymeric Scaffolds for Pancreatic Tissue Engineering: A Review

In recent years, there has been an alarming increase in the incidence of diabetes, with one in every eleven individuals worldwide suffering from this debilitating disease. As the available treatment options fail to reduce disease progression, novel avenues such as the bioartificial pancreas are being given serious consideration. In the past decade, the research focus has shifted towards the field of tissue engineering, which helps to design biological substitutes for repair and replacement of non-functional or damaged organs. Scaffolds constitute an integral part of tissue engineering; they have been shown to mimic the native extracellular matrix, thereby supporting cell viability and proliferation. This review offers a novel compilation of the recent advances in polymeric scaffolds, which are used for pancreatic tissue engineering. Furthermore, in this article, the design strategies for bioartificial pancreatic constructs and their future applications in cell-based therapy are discussed.

[Research progress on the donor cell sources of pancreatic islet transplantation for treatment of diabetes mellitus]

Objective

To summarize the research progress on the source and selection of donor cells in the field of islet replacement therapy for diabetes mellitus.

Methods

Domestic and abroad literature concerning islet replacement therapy for diabetes mellitus, as well as donor source and donor selection was reviewed and analyzed thoroughly.

Results

The shortage of donor supply is still a major obstacle for the widely clinical application of pancreatic islet transplantation (PIT). Currently, in addition to the progress on the allogeneic/autologous donor islet supply, some remarkable achievements have been also attained in the application of xenogeneic islet (from pig donor), as well as islet like cells derived from stem cells and islet cell line, potentially enlarging the source of implantable cells.

Conclusion

Adequate and suitable donor cell supply is an essential prerequisite for widely clinical application of PIT therapy for type 1 diabetes mellitus (T1DM). Further perfection of organ donation system, together with development of immune-tolerance induction, gene and bioengineering technology etc. will possibly solve the problem of donor cell shortage and provide a basis for clinical application of cellular replacement therapy for T1DM.

Selection of Implantation Sites for Transplantation of Encapsulated Pancreatic Islets

Pancreatic islet transplantation has been validated as a valuable therapy for type 1 diabetes mellitus patients with exhausted insulin treatment. However, this therapy remains limited by the shortage of donor and the requirement of lifelong immunosuppression. Islet encapsulation, as an available bioartificial pancreas (BAP), represents a promising approach to enable protecting islet grafts without or with minimal immunosuppression and possibly expanding the donor pool. To develop a clinically implantable BAP, some key aspects need to be taken into account: encapsulation material, capsule design, and implant site. Among them, the implant site exerts an important influence on the engraftment, stability, and biocompatibility of implanted BAP. Currently, an optimal site for encapsulated islet transplantation may include sufficient capacity to host large graft volumes, portal drainage, ease of access using safe and reproducible procedure, adequate blood/oxygen supply, minimal immune/inflammatory reaction, pliable for noninvasive imaging and biopsy, and potential of local microenvironment manipulation or bioengineering. Varying degrees of success have been confirmed with the utilization of liver or extrahepatic sites in an experimental or preclinical setting. However, the ideal implant site remains to be further engineered or selected for the widespread application of encapsulated islet transplantation.

Microencapsulated Schwann cell transplantation inhibits P2X3 receptor expression in dorsal root ganglia and neuropathic pain

Schwann cell transplantation is a promising method to promote neural repair, and can be used for peripheral nerve protection and myelination. Microcapsule technology largely mitigates immune rejection of transplanted cells. We previously showed that microencapsulated olfactory ensheathing cells can reduce neuropathic pain and we hypothesized that microencapsulated Schwann cells can also inhibit neuropathic pain. Rat Schwann cells were cultured by subculture and then microencapsulated and were tested using a rat chronic constriction injury (CCI) neuropathic pain model. CCI rats were treated with Schwann cells or microencapsulated Schwann cells and were compared with sham and CCI groups. Mechanical withdrawal threshold and thermal withdrawal latency were assessed preoperatively and at 1, 3, 5, 7, 9, 11 and 14 days postoperatively. The expression of P2X3 receptors in L4-5 dorsal root ganglia of the different groups was detected by double-label immunofluorescence on day 14 after surgery. Compared with the chronic constriction injury group, mechanical withdrawal threshold and thermal withdrawal latency were higher, but the expression of P2X3 receptors was remarkably decreased in rats treated with Schwann cells and microencapsulated Schwann cells, especially in the rats transplanted with microencapsulated Schwann cells. The above data show that microencapsulated Schwann cell transplantation inhibits P2X3 receptor expression in L4-5 dorsal root ganglia and neuropathic pain.

Contribution of polymeric materials to progress in xenotransplantation of microencapsulated cells: a review

Cell microencapsulation and subsequent transplantation of the microencapsulated cells require multidisciplinary approaches. Physical, chemical, biological, engineering, and medical expertise has to be combined. Several natural and synthetic polymeric materials and different technologies have been reported for the preparation of hydrogels, which are suitable to protect cells by microencapsulation. However, owing to the frequent lack of adequate characterization of the hydrogels and their components as well as incomplete description of the technology, many results of in vitro and in vivo studies appear contradictory or cannot reliably be reproduced. This review addresses the state of the art in cell microencapsulation with special focus on microencapsulated cells intended for xenotransplantation cell therapies. The choice of materials, the design and fabrication of the microspheres, as well as the conditions to be met during the cell microencapsulation process, are summarized and discussed prior to presenting research results of in vitro and in vivo studies. Overall, this review will serve to sensitize medically educated specialists for materials and technological aspects of cell microencapsulation.