MECHANISMS IN ENDOCRINOLOGY: Towards the clinical translation of stem cell therapy for type 1 diabetes

Pancreas-on-a-Chip Technology for Transplantation Applications

PURPOSE OF REVIEW

Human pancreas-on-a-chip (PoC) technology is quickly advancing as a platform for complex in vitro modeling of islet physiology. This review summarizes the current progress and evaluates the possibility of using this technology for clinical islet transplantation.

RECENT FINDINGS

PoC microfluidic platforms have mainly shown proof of principle for long-term culturing of islets to study islet function in a standardized format. Advancement in microfluidic design by using imaging-compatible biomaterials and biosensor technology might provide a novel future tool for predicting islet transplantation outcome. Progress in combining islets with other tissue types gives a possibility to study diabetic interventions in a minimal equivalent in vitro environment. Although the field of PoC is still in its infancy, considerable progress in the development of functional systems has brought the technology on the verge of a general applicable tool that may be used to study islet quality and to replace animal testing in the development of diabetes interventions.

Urocortin 2 Gene Transfer Improves Glycemic Control and Reduces Retinopathy and Mortality in Murine Insulin Deficiency

Type 1 diabetes affects 20 million patients worldwide. Insulin is the primary and commonly the sole therapy for type 1 diabetes. However, only a minority of patients attain the targeted glucose control and reduced adverse events. We tested urocortin 2 gene transfer as single-agent therapy for insulin deficiency using two mouse models. Urocortin 2 gene transfer reduced blood glucose for months after a single intravenous injection, through increased skeletal muscle insulin sensitivity, increased insulin release in response to glucose stimulation, and increased plasma insulin levels before and during euglycemic clamp. The combined increases in both insulin availability and sensitivity resulted in improved glycemic indices-events that were not anticipated in these insulin-deficient models. In addition, urocortin 2 gene transfer reduced ocular manifestations of long-standing insulin deficiency such as vascular leak and improved retinal function. Finally, mortality was reduced by urocortin 2 gene transfer. The mechanisms for these beneficial effects included increased activities of AMP-activated protein kinase and Akt (protein kinase B) in skeletal muscle, increased skeletal muscle glucose uptake, and increased insulin release. These data suggest that urocortin 2 gene transfer may be a viable therapy for new onset type 1 diabetes and might reduce insulin needs in later stage disease.

Function and Gene Expression of Islets Experimentally Transplanted to Muscle and Omentum

Islet transplantation to the liver is a potential curative treatment for patients with type 1 diabetes. Muscle and the greater omentum are two alternative implantation sites, which can provide excellent engraftment and hold potential as future sites for stem-cell-derived beta-cell replacement. We evaluated the functional outcome after islet transplantation to muscle and omentum and found that alloxan-diabetic animals were cured with a low number of islets (200) at both sites. The cured animals had a normal area under the curve blood glucose response to intravenous glucose, albeit animals with intramuscular islet grafts had increased 120-min blood glucose levels. They also demonstrated an exaggerated counter regulatory response to hypoglycemia. The expression of genes important for beta-cell function was, at both implantation sites, comparable to that in native pancreatic islets. The gene expression of insulin (INS1 and INS2) and glucose transporter-2 was even increased, and the expression of lactate dehydrogenase decreased, at both sites when compared to native islets. We conclude that muscle and omentum provide excellent conditions for engraftment of transplanted islets. When compared to control, 200 islets implanted to the omentum displayed a restored glucose tolerance, whereas animals with intramuscular islet grafts of similar size displayed mild glucose intolerance.

Investigating curcumin potential for diabetes cell therapy, in vitro and in vivo study

AIMS

An important obstacle on the way of cell-based therapy is the risk of tumorigenicity in the patients benefit from these transplanted cells due to undifferentiated cells which participate in transplantation. Curcumin, the main compound of spice turmeric -as one of the natural products-was demonstrated to possess effective anti-cancer properties, with no significant effect on normal cells in dose and/or time-dependent manner. Furthermore many studies have been accomplished using curcumin for diabetes treatment. Therefore in this study we examined the efficacy of IPCs treated with curcumin in vivo.

MAIN METHODS

Differentiation efficiency investigated by flowcytometry. RNA extraction and real-time PCR performed for important genes in IPC differentiation and tumorigenesis including Insulin, Nestin, Ngn3, Pdx1, P21, and P53. Finally we investigated the efficiency of these differentiated and treated cells in diabetic rats.

KEY FINDINGS

Our data indicates that nanocurcumin -in a specific dose-reduces the expression of Nestin with no significant effect on insulin expression in mRNA and protein level. Besides blood glucose level of diabetic rats which treated with DNC + cells, decreased from average 350 (mg/dI) to 100 (mg/dI). Checking out the pancreases of these rats, demonstrated that their endocrine segment was rebuilt. Moreover hematoxylin & eosin staining and IF results revealed that the Langerhans Islands were reformed.

SIGNIFICANCE

IPCs' which treated with DNC were able to efficiently control the blood glucose level in diabetic rats which these cells were transplanted to them. Hence Curcumin has the potential to be employed in this kind of cell therapy.

Connexin 43 Functions as a Positive Regulator of Stem Cell Differentiation into Definitive Endoderm and Pancreatic Progenitors

Efficient stem cell differentiation into pancreatic islet cells is of critical importance for the development of cell replacement therapies for diabetes. Here, we identify the expression pattern of connexin 43 (Cx43), a gap junction (GJ) channel protein, in human embryonic stem cell (hESC)-derived definitive endoderm (DE) and primitive gut tube cells, representing early lineages for posterior foregut (PF), pancreatic progenitors (PP), pancreatic endocrine progenitors (PE), and islet cells. As the function of GJ channels is dependent on their gating status, we tested the impact of supplementing hESC-derived PP cell cultures with AAP10, a peptide that promotes Cx43 GJ channel opening. We found that this treatment promotes the expression of DE markers FoxA2 and Sox17, leads to a more efficient derivation of DE, and improves the yield of PF, PP, and PE cells. These results demonstrate a functional involvement of GJ channels in the differentiation of embryonic stem cells into pancreatic cell lineages.

Concise Review: Human Pluripotent Stem Cells for the Modeling of Pancreatic β-Cell Pathology

Pancreatic β‐cells are the only source of insulin. Disturbances in β‐cell development or function may thus result in insulin deficiency or excess, presenting as hyper‐ or hypoglycemia. It is increasingly evident that common forms of diabetes (types 1 and 2) are pathogenically heterogeneous. Development of efficient therapies is dependent on reliable disease models. Although animal models are remarkably useful research tools, they present limitations because of species differences. As an alternative, human pluripotent stem cell technologies offer multiple possibilities for the study of human diseases in vitro. In the last decade, advances in the derivation of induced pluripotent stem cells from diabetic patients, combined with β‐cell differentiation protocols, have resulted in the generation of useful disease models for diabetes. First disease models have been focusing on monogenic diabetes. The development of genome editing technologies, more advanced differentiation protocols and humanized mouse models based on transplanted cells have opened new horizons for the modeling of more complex forms of β‐cell dysfunction. We present here the incremental progress made in the modeling of diabetes using pluripotent stem cells. We discuss the current challenges and opportunities of these approaches to dissect β‐cell pathology and devise new pharmacological and cell replacement therapies. stem cells2019;37:33–41