Treatment options for diabetes: potential role of stem cells

Hypoxia within subcutaneously implanted macroencapsulation devices limits the viability and functionality of densely loaded islets

Introduction

Subcutaneous macroencapsulation devices circumvent disadvantages of intraportal islet therapy. However, a curative dose of islets within reasonably sized devices requires dense cell packing. We measured internal PO2 of implanted devices, mathematically modeled oxygen availability within devices and tested the predictions with implanted devices containing densely packed human islets.

Methods

Partial pressure of oxygen (PO2) within implanted empty devices was measured by noninvasive 19F-MRS. A mathematical model was constructed, predicting internal PO2, viability and functionality of densely packed islets as a function of external PO2. Finally, viability was measured by oxygen consumption rate (OCR) in day 7 explants loaded at various islet densities.

Results

In empty devices, PO2 was 12 mmHg or lower, despite successful external vascularization. Devices loaded with human islets implanted for 7 days, then explanted and assessed by OCR confirmed trends proffered by the model but viability was substantially lower than predicted. Co-localization of insulin and caspase-3 immunostaining suggested that apoptosis contributed to loss of beta cells.

Discussion

Measured PO2 within empty devices declined during the first few days post-transplant then modestly increased with neovascularization around the device. Viability of islets is inversely related to islet density within devices.

Solid implantable devices for sustained drug delivery

Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.

Establishment of a diabetes mellitus type 1 model in the common marmoset

Common marmosets have attracted considerable attention as a small standard primate model in biomedical research. However, no marmoset diabetes model is available. Here, we established a marmoset diabetes model via the combination of partial pancreatectomy and intravenous streptozotocin (STZ). A partial pancreatectomy was performed in 11 common marmosets and multiple STZ doses were intravenously administered. Diabetes was diagnosed upon sustained hyperglycaemia (nonfasting blood glucose level >200 mg/dl). Blood glucose and biochemistry were periodically assessed, in addition to glucose tolerance testing, continual blood glucose determination using a continuous glucose monitoring system, urine testing and histological evaluation. In 8 of the 11 animals (73%), diabetes mellitus was induced. The diabetic marmosets also showed abnormal intravenous and oral glucose tolerance test results. Blood glucose levels decreased in response to human insulin administration. The hyperglycaemic state was irreversible and persisted for more than 3 months, and the animals’ condition was manageable via daily insulin administration. Thus, diabetes can be successfully induced and maintained in the common marmoset via partial pancreatectomy and STZ administration. This protocol effectively generates a valuable animal model for studying disease pathogenesis, risk factors and therapeutic interventions, including islet transplantation.

Pax4 synergistically acts with Pdx1, Ngn3 and MafA to induce HuMSCs to differentiate into functional pancreatic β-cells

It has been indicated that the combination of pancreatic and duodenal homeobox 1 (Pdx1), MAF bZIP transcription factor A (MafA) and neurogenin 3 (Ngn3) was able to reprogram various cell types towards pancreatic β-like cells (pβLCs). Paired box 4 (Pax4), a transcription factor, has a key role in regulating the maturation of pancreatic β-cells (pβCs). In the present study, it was investigated whether Pax4 is able to synergistically act with Pdx1, Ngn3 and MafA to induce human umbilical cord mesenchymal stem cells (HuMSCs) to differentiate into functional pβCs in vitro. HuMSCs were isolated, cultured and separately transfected with adenovirus (Ad) expressing enhanced green fluorescence protein, Pax4 (Ad-Pax4), Pdx1+MafA+Ngn3 (Ad-3F) or Ad-Pxa4 + Ad-3F. The expression of C-peptide, insulin and glucagon was detected by immunofluorescence. The transcription of a panel of genes was determined by reverse transcription-quantitative PCR, including glucagon (GCG), insulin (INS), NK6 homeobox 1 (NKX6-1), solute carrier family 2 member 2 (SLC2A2), glucokinase (GCK), proprotein convertase subtilisin/kexin type 1 (PCSK1), neuronal differentiation 1 (NEUROD1), ISL LIM homeobox 1 (ISL 1), Pax6 and PCSK type 2 (PCSK2). Insulin secretion stimulated by glucose was determined using ELISA. The results suggested that, compared with Ad-3F alone, cells co-transfected with Ad-Pax4 and Ad-3F expressed higher levels of INS and C-peptide, as well as genes expressed in pancreatic β precursor cells, and secreted more insulin in response to high glucose. Furthermore, the expression of GCG in cells transfected with Ad-3F was depressed by Ad-Pax4. The present study demonstrated that Pax4 was able to synergistically act with the transcription factors Pdx1, Ngn3 and MafA to convert HuMSCs to functional pβLCs. HuMSCs may be potential seed cells for generating functional pβLCs in the therapy of diabetes.

Mechanistic insights into the augmented effect of bone marrow mesenchymal stem cells and thiazolidinediones in streptozotocin-nicotinamide induced diabetic rats

This study was designed to assess whether the protective effects of bone marrow-derived mesenchymal stem cells (MSCs) against diabetes could be enhanced by pioglitazone (PIO), a PPARγ agonist. Combined MSCs and PIO treatments markedly improved fasting blood glucose, body weight, lipid profile levels, insulin level, insulin resistance, β cell function. Those protective effects also attenuated both pancreatic lesions and fibrosis in diabetic rats and decreased the depletion of pancreatic mediators of glycemic and lipid metabolism including peroxisome proliferator-activated receptor alpha (PPARα), PGC-1α, GLP-1 and IRS-2. Cardiac biogenesis of diabetic groups was also improved with MSCs and/or PIO treatments as reflected by the enhanced up-regulation of the expressions of cardiac IRS1, Glucose transporter 4, PGC-1, PPARα and CPT-1 genes and the down-regulated expression of lipogenic gene SREBP. The combination of MSCs and PIO also potentiated the decrease of abnormal myocardial pathological lesions in diabetic rats. Similarly, the inhibitory effects of MSCs on diabetic cardiac fibrosis and on the up regulations of TGF-β, collagen I and III gene expressions were partial but additive when combined with PIO. Therefore, combined therapy with PIO and BMCs transplantation could further potentiate the protective benefit of MSCs against diabetes and cardiac damage compared to MSCs monotherapy.

Role of adipose tissue derived stem cells differentiated into insulin producing cells in the treatment of type I diabetes mellitus

Generation of new β cells is an important approach in the treatment of type 1 diabetes mellitus (type 1 DM). Adipose tissue-derived stem cells (ADSCs) might be one of the best sources for cell replacement therapy for diabetes. Therefore, this work aimed to test the possible role of transplanted insulin-producing cells (IPCs) differentiated from ADSCs in treatment of streptozotocin (STZ) induced type I DM in rats. Type 1 DM was induced by single intra peritoneal injection with STZ (50 mg/kg BW). Half of the diabetic rats were left without treatment and the other half were injected with differentiated IPCs directly into the pancreas. ADSCs were harvested, cultured and identified by testing their phenotypes through flow cytometry. They were further subjected to differentiation into IPCs using differentiation medium. mRNA expression of pancreatic transcription factors (pdx1), insulin and glucose transporter-2 genes by real time PCR was done to detect the cellular differentiation and confirmed by stimulated insulin secretion. The pancreatic tissues from all groups were examined 2 months after IPC transplantation and were subjected to histological, Immunohistochemical and morphometric study. The differentiated IPCs showed significant expression of pancreatic β cell markers and insulin secretion in glucose dependent manner. Treatment with IPCs induced apparent regeneration, diffused proliferated islet cells and significant increase in C-peptide immune reaction. We concluded that transplantation of differentiated IPCs improved function and morphology of Islet cells in diabetic rats. Consequently, this therapy option may be a promising therapeutic approach to patient with type 1 DM if proven to be effective and safe.

Advances in islet encapsulation technologies

Type 1 diabetes is an autoimmune disorder in which the immune system attacks and destroys insulin-producing islet cells of the pancreas. Although islet transplantation has proved to be successful for some patients with type 1 diabetes, its widespread use is limited by islet donor shortage and the requirement for lifelong immunosuppression. An encapsulation strategy that can prevent the rejection of xenogeneic islets or of stem cell-derived allogeneic islets can potentially eliminate both of these barriers. Although encapsulation technology has met several challenges, the convergence of expertise in materials, nanotechnology, stem cell biology and immunology is allowing us to get closer to the goal of encapsulated islet cell therapy for humans.

Factors influencing the longevity and replacement frequency of Provox voice prostheses

INTRODUCTION

This study aimed to assess the factors that influence the longevity and replacement frequency of Provox voice prostheses following their placement.

METHODS

The medical records of 27 patients who received Provox voice prostheses after total laryngectomy and attended follow-up regularly between 1998 and 2012 were retrospectively reviewed. The success rate of the Provox voice prostheses (i.e. whether speech was achieved), quality of speech achieved, number and type of complications encountered, frequency of prostheses replacement and reasons for prostheses replacements were evaluated.

RESULTS

All 27 patients were men and their mean age was 63.0 (range 43-78) years. The mean follow-up period was 60.3 (range 1-168) months. Fluent and understandable speech was achieved in 85.0% of the patients. The mean duration before prosthesis replacement had to be performed was 17.1 (range 1-36) months. The most frequent complication was fluid leakage through the prosthesis. There was a strong positive correlation of 77.1% between the longevity of prostheses and postoperative follow-up duration (r = 0.771; p < 0.01).

CONCLUSION

The voice prosthesis is a tool that can be delivered in a practical fashion and replaced easily with no serious complications. It is a means by which speech can be restored, with a high success rate, after total laryngectomy. In the present study, we found that postoperative follow-up duration was the most important factor influencing the longevity of the Provox voice prosthesis.

Cell-based therapy approaches: the hope for incurable diseases

Cell therapies aim to repair the mechanisms underlying disease initiation and progression, achieved through trophic effect or by cell replacement. Multiple cell types can be utilized in such therapies, including stem, progenitor or primary cells. This review covers the current state of cell therapies designed for the prominent disorders, including cardiovascular, neurological (Parkinson's disease, amyotrophic lateral sclerosis, stroke, spinal cord injury), autoimmune (Type 1 diabetes, multiple sclerosis, Crohn's disease), ophthalmologic, renal, liver and skeletal (osteoarthritis) diseases. Various cell therapies have reached advanced clinical trial phases with potential marketing approvals in the near future, many of which are based on mesenchymal stem cells. Advances in pluripotent stem cell research hold great promise for regenerative medicine. The information presented in this review is based on the analysis of the cell therapy collection detailed in LifeMap Discovery(®) (LifeMap Sciences Inc., USA) the database of embryonic development, stem cell research and regenerative medicine.

Applicability of Adipose-Derived Stem Cells in Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (T1DM) is a form of early onset diabetes mellitus characterized by the autoimmune destruction of insulin-producing cells (IPCs), resulting in hyperglycemia and abnormal glucose metabolism. There are currently no treatments available capable of completely curing the symptoms associated with the loss or functional defects of IPCs. Nonetheless, stem cell therapy has demonstrated considerable promise in the replacement of IPCs with immunomodulatory functions to overcome the defects caused by T1DM. Adipose-derived stem cells (ADSCs) are particularly suitable for use in cell transplantation therapy, especially when seeking to avoid the ethical issues and tumorigenic complications commonly associated with embryos or induced pluripotent stem cells. Cell-based treatments have demonstrated therapeutic advantages and clinical applicability of ADSCs in T1DM, ensuring their suitability for transplantation therapy. This manuscript focuses on the benefits and possible mechanisms in a T1DM-relevant model and displays positive results from finished or ongoing human clinical trials. We also discuss and hypothesize potential methods to further enhance the therapeutic efficacy of these efforts, such as a humanized rodent model and gene therapies for IPC clusters, to meet the clinical applicability of the standard.

Co-transplantation of mesenchymal stromal cells and cord blood cells in treatment of diabetes

BACKGROUND AIMS

Stem cells provide a promising source for treatment of type 1 diabetes, but the treatment strategy and mechanism remain unclear. The aims of this study were to investigate whether co-transplantation of umbilical cord-derived mesenchymal stromal cells (UC-MSCs) and cord blood mononuclear cells (CB-MNCs) could reverse hyperglycemia in type 1 diabetic mice and to determine the appropriate ratio for co-transplantation. The treatment mechanism was also studied.

METHODS

A simple and efficient isolation method was developed to generate qualified UC-MSCs. UC-MSCs and CB-MNCs were then transplanted into type 1 diabetic mice at different ratios (UC-MSCs to CB-MNCs = 1:1, 1:4, 1:10) to observe the change in blood glucose concentration. Histology, immunohistochemistry, and human Alu polymerase chain reaction assay were performed to evaluate for the presence of donor-derived cells and the repair of endogenous islets. We also induced UC-MSCs into islet-like cells under specific culture conditions to determine their differentiate potential in vitro.

RESULTS

Co-transplantation of UC-MSCs and CB-MNCs at a ratio of 1:4 effectively reversed hyperglycemia in diabetic mice. The detection of human Alu sequence indicated that the engraftment of donor-derived cells had homed into the recipient's pancreas and kidney. Although neither human insulin nor human nuclei antigen was detected in the regenerated pancreas, UC-MSCs could differentiate into insulin-secreted cells in vitro.

CONCLUSIONS

Co-transplantation of UC-MSCs and CB-MNCs at a ratio of 1:4 could efficiently reverse hyperglycemia and repair pancreatic tissue.

Compliant 3D microenvironment improves β-cell cluster insulin expression through mechanosensing and β-catenin signaling

Type 1 diabetes is chronic disease with numerous complications and currently no cure. Tissue engineering strategies have shown promise in providing a therapeutic solution, but maintenance of islet function and survival within these therapies represents a formidable challenge. The islet microenvironment may hold the key for proper islet maintenance. To elucidate the microenvironmental conditions necessary for improved islet function and survival, three-dimensional (3D) polyacrylamide cell scaffolds were fabricated with stiffnesses of 0.1 and 10 kPa to regulate the spatial and mechanical control of biosignals. Specifically, we show a significant increase in insulin mRNA expression of 3D primary mouse islet-derived and Min6-derived β-cell clusters grown on compliant 0.1 kPa scaffolds. Moreover, these compliant 0.1 kPa scaffolds also increase glucose sensitivity in Min6-derived β-cell clusters as demonstrated by the increased glucose stimulation index. Our data suggest that stiffness-specific insulin processing is regulated through the myosin light chain kinase (MLCK) and Rho-associated protein kinase (ROCK) mechanosensing pathways. Additionally, β-catenin is required for regulation of stiffness-dependent insulin expression. Through activation or inhibition of β-catenin signaling, reversible control of insulin expression is achieved on the compliant 0.1 kPa and overly stiff 10 kPa substrates. Understanding the role of the microenvironment on islet function can enhance the therapeutic approaches necessary to treat diabetes for improving insulin sensitivity and response.

Nonhuman primate models of type 1 diabetes mellitus for islet transplantation

Islet transplantation is an attractive treatment of type 1 diabetes mellitus (T1DM). Animal models of diabetes mellitus (DM) contribute a lot to the experimental studies of islet transplantation and to evaluations of isolated islet grafts for future clinical applications. Diabetic nonhuman primates (NHPs) represent the suitable models of DMs to better evaluate the effectiveness of islet transplantation, to assess new strategies for controlling blood glucose (BG), relieving immune rejection, or prolonging islet survival, and eventually to translate the preclinical data into tangible clinical practice. This review introduces some NHP models of DM, clarifies why and how the models should be used, and elucidates the usefulness and limitations of the models in islet transplantation.