Mesenchymal stem cells help pancreatic islet transplantation to control type 1 diabetes

Construction of engineered 3D islet micro-tissue using porcine decellularized ECM for the treatment of diabetes

Islet transplantation improves diabetes patients' long-term blood glucose control, but its success and utility are limited by cadaver availability, quality, and considerable islet loss after transplantation due to ischemia and inadequate angiogenesis. This study used adipose, pancreatic, and liver tissue decellularized extracellular matrix (dECM) hydrogels in an effort to recapitulate the islet sites inside the pancreas in vitro, and successfully generated viable and functional heterocellular islet micro-tissues using islet cells, human umbilical vein endothelial cells, and adipose-derived mesenchymal stem cells. The three-dimensional (3D) islet micro-tissues maintained prolonged viability and normal secretory function, and showed high drug sensitivity in drug testing. Meanwhile, the 3D islet micro-tissues significantly enhanced survival and graft function in a mouse model of diabetes. These supportive 3D physiomimetic dECM hydrogels can be used not only for islet micro-tissue culture in vitro, but also have great promise for islet transplantation for the treatment of diabetes.

Adipose Tissue-Derived Stromal/Stem Cells Transplantation with Cholecalciferol Supplementation in Recent-Onset Type 1 Diabetes Patients: Twelve Months Follow-Up

To evaluate safety and therapeutic effect along 12 months of allogenic adipose tissue-derived stromal/stem cells (ASCs) transplantation with cholecalciferol (VITD) in patients with recent-onset type 1 diabetes (T1D). Prospective, phase II, open trial, pilot study in which patients with recent onset T1D received ASCs (1xKgx106 cells) and VITD 2000UI/day for 12 months (group 1) and were compared to controls with standard insulin therapy (group 2). Adverse events, C-peptide area under the curve (CPAUC), insulin dose, HbA1c and frequency of FoxP3+ in CD4+ or CD8+ T-cells(flow cytometry) were evaluated at baseline(T0), after 3(T3), 6(T6) and 12 months(T12). Eleven patients completed follow up (7:group 1;4:group 2). Group 1 had lower insulin requirement at T3(0.24±0.18vs0.53±0.23UI/kg,p=0.04), T6(0.24±0.15vs0.66±0.33 UI/kg,p=0.04) and T12(0.39±0.15vs0.74±0.29 UI/Kg,p=0.04).HbA1c was lower at T6 (50.57±8.56vs72.25±10.34 mmol/mol,p=0.01), without differences at T12 (57.14±11.98 in group 1 vs. 73.5±14.57 mmol/min in group 2, p=0.16). CPAUC was not significantly different between groups at T0(p=0.07), higher in group 1 at T3(p=0.04) and T6(p=0.006), but similar at T12(p=0.23). IDAA1c was significantly lower in group 1 than group 2 at T3,T6 and T12 (p=0.006, 0.006 and 0.042, respectively). IDDA1c was inversely correlated to FoxP3 expression in CD4 and CD8+ T cells at T6 (p<0.001 and p=0.01, respectively). In group 1, one patient had recurrence of a benign teratoma that was surgically removed, not associated to the intervention. ASCs with VITD without immunosuppression were safe and associated lower insulin requirements, better glycemic control, and transient better pancreatic function in recent onset T1D, but the potential benefits were not sustained.

The Therapeutic Potential of Mesenchymal Stem Cells in the Treatment of Diabetes Mellitus

Mesenchymal stem cells (MSCs) exist in many tissues and can differentiate into cells of multiple lineages, such as adipocytes, osteoblasts, or chondrocytes. MSC administration has demonstrated therapeutic potential in various degenerative and inflammatory diseases (e.g., graft-vs.-host disease, multiple sclerosis, Crohn's disease, organ fibrosis, and diabetes mellitus [DM]). The mechanisms involved in the therapeutic effects of MSCs are multifaceted. Generally, implanted MSCs can migrate to sites of injury, where they establish an anti-inflammatory and regenerative microenvironment in damaged tissues. In addition, MSCs can modulate innate and adaptive immune responses through immunosuppressive mechanisms that involve immune cells, inflammatory cytokines, chemokines, and immunomodulatory factors. DM has a high prevalence worldwide; it also contributes to a high rate of mortality worldwide. MSCs offer a promising therapeutic agent to prevent or repair damage from DM and diabetic complications through properties such as multilineage differentiation, homing, promotion of angiogenesis, and immunomodulation (e.g., prevention of oxidative stress, fibrosis, and cell death). In this study, we review current findings regarding the immunomodulatory and regenerative mechanisms of MSCs, as well as their therapeutic applications in DM and DM-related complications.

Engineering Islets From Stem Cells: The Optimal Solution for the Treatment of Diabetes?

Diabetes is a metabolic disease characterized by insulin deficiency. Bioengineering of stem cells with the aim to restore insulin production and glucose regulation has the potential to cure diabetic patients. In this review, we focus on the recent developments for bioengineering of induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and pancreatic progenitor cells in view of generating insulin producing and glucose regulating cells for β-cell replacement therapies. Recent clinical trials using islet cells derived from stem cells have been initiated for the transplantation into diabetic patients, with crucial bottlenecks of tumorigenesis, post-transplant survival, genetic instability, and immunogenicity that should be further optimized. As a new approach given high expectations, bioengineered islets from stem cells occupies considerable potential for the future clinical application and addressing the treatment dilemma of diabetes.

3D Printing Mini-Capsule Device for Islet Delivery to Treat Type 1 Diabetes

Transplantation of encapsulated islets has been shown to hold a promising potential treatment for type 1 diabetes (T1D). However, there are several obstacles to overcome, such as immune rejection by the host of the grafts, sustainability of islet function, and retrievability or replacement of the encapsulated system, hinder their clinical applications. In this study, mini-capsule devices containing islets were fabricated by using digital light processing (DLP) 3D printing. To ensure a high survival rate and low immunogenicity of the fabricated islets, 20s was selected as the most suitable printing condition. Meanwhile, the mini-capsule devices with a groove structure were fabricated to prevent islet cells leakage. Subcutaneous transplantations of encapsulated islets in immunocompetent C57BL/6 mice indicated significant improvement in the symptoms of streptozotocin-induced hyperglycemia without any immunosuppression treatment for at least 15 weeks. In vivo intraperitoneal glucose tolerance tests (IPGTT) performed at different time points demonstrated therapeutically relevant glycemic ameliorate of the device. The implants retrieved after 15 weeks still contained viable and adequate numbers of islet cells. The results of this study indicate that the proposed mini-capsule device can deliver sufficient islet cell mass, prevent islet cells leakage, and maintain long-term cell survival while allowing easy retrieval. Furthermore, the proposed encapsulated islets may help with T1D cellular treatment by overcoming the obstacles of islet transplantation.

The Influence of Microenvironment on Survival of Intraportal Transplanted Islets

Clinical islet transplantation has the potential to cure type 1 diabetes. Despite recent therapeutic success, it is still uncommon because transplanted islets are damaged by multiple challenges, including instant blood mediated inflammatory reaction (IBMIR), inflammatory cytokines, hypoxia/reperfusion injury, and immune rejection. The transplantation microenvironment plays a vital role especially in intraportal islet transplantation. The identification and targeting of pathways that function as “master regulators” during deleterious inflammatory events after transplantation, and the induction of immune tolerance, are necessary to improve the survival of transplanted islets. In this article, we attempt to provide an overview of the influence of microenvironment on the survival of transplanted islets, as well as possible therapeutic targets.

Inhibitory Effect of Bovine Adipose-Derived Mesenchymal Stem Cells on Lipopolysaccharide Induced Inflammation of Endometrial Epithelial Cells in Dairy Cows

Endometritis is a disease that affects reproductive health in dairy cows and causes serious economic damage to the dairy industry world-wide. Although in recent years, the application of mesenchymal stem cell (MSC) therapy for the treatment of inflammatory diseases has attracted much attention, there are few reports of the use of MSCs in dairy cows. In the present study, our objective was to explore the inhibitory effects of bovine adipose-derived mesenchymal stem cells (bAD-MSCs) on lipopolysaccharide (LPS) induced inflammation in bovine endometrial epithelial cells (bEECs) along with the potential underlying molecular mechanisms. We characterized isolated bAD-MSCs using cell surface marker staining and adipogenic/osteogenic differentiation, and analyzed them using immunofluorescence, flow cytometry (surface marker staining), and adipogenic and osteogenic differentiation. Furthermore, to understand the anti-inflammatory effects of bAD-MSCs on LPS induced bEEC inflammation, we used a bAD-MSC/bEEC co-culture system. The results showed that bAD-MSC treatments could significantly decrease LPS induced bEEC apoptosis and pro-inflammatory cytokine expression levels, such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α). Furthermore, our results showed that bAD-MSC treatments could also significantly downregulate LPS induced p38, IkB-a, and JAK1 phosphorylation and Bax protein expression levels, which are closely related to inflammatory progress and cellular apoptosis in bEECs. Our findings demonstrate that bAD-MSCs play an inhibitory role in LPS induced bEEC inflammation and provide new insights for the clinical therapy of endometritis in dairy cows.

Human Wharton's Jelly-Derived Mesenchymal Stromal Cells Primed by Tumor Necrosis Factor-α and Interferon-γ Modulate the Innate and Adaptive Immune Cells of Type 1 Diabetic Patients

The unique immunomodulation and immunosuppressive potential of Wharton’s jelly-derived mesenchymal stromal cells (WJ-MSCs) make them a promising therapeutic approach for autoimmune diseases including type 1 diabetes (T1D). The immunomodulatory effect of MSCs is exerted either by cell-cell contact or by secretome secretion. Cell-cell contact is a critical mechanism by which MSCs regulate immune-responses and generate immune regulatory cells such as tolerogenic dendritic cells (tolDCs) and regulatory T cell (Tregs). In this study, we primed WJ-MSCs with TNF-α and IFN-γ and investigated the immunomodulatory properties of primed WJ-MSCs on mature dendritic cells (mDCs) and activated T cells differentiated from mononuclear cells (MNCs) of T1D patient’s. Our findings revealed that primed WJ-MSCs impaired the antigen-mediated immunity, upregulated immune-tolerance genes and downregulated immune-response genes. We also found an increase in the production of anti-inflammatory cytokines and suppression of the production of pro-inflammatory cytokines. Significant upregulation of FOXP3, IL10 and TGFB1 augmented an immunosuppressive effect on adaptive T cell immunity which represented a strong evidence in support of the formation of Tregs. Furthermore, upregulation of many critical genes involved in the immune-tolerance mechanism (IDO1 and PTGES2/PTGS) was detected. Interestingly, upregulation of ENTPD1/NT5E genes express a strong evidence to switch immunostimulatory response toward immunoregulatory response. We conclude that WJ-MSCs primed by TNF-α and IFN-γ may represent a promising tool to treat the autoimmune disorders and can provide a new evidence to consider MSCs- based therapeutic approach for the treatment of TID.

Human Hemangioblast-Derived Mesenchymal Stem Cells Promote Islet Engraftment in a Minimal Islet Mass Transplantation Model in Mice

Islet transplantation can restore glycemic control in patients with type 1 diabetes. Using this procedure, the early stages of engraftment are often crucial to long-term islet function, and outcomes are not always successful. Numerous studies have shown that mesenchymal stem cells (MSCs) facilitate islet graft function. However, experimental data can be inconsistent due to variables associated with MSC generation (including donor characteristics and tissue source), thus, demonstrating the need for a well-characterized and uniform cell product before translation to the clinic. Unlike bone marrow- or adipose tissue-derived MSCs, human embryonic stem cell-derived-MSCs (hESC-MSCs) offer an unlimited source of stable and highly-characterized cells that are easily scalable. Here, we studied the effects of human hemangioblast-derived mesenchymal cells (HMCs), (i.e., MSCs differentiated from hESCs using a hemangioblast intermediate), on islet cell transplantation using a minimal islet mass model. The co-transplantation of the HMCs allowed a mass of islets that was insufficient to correct diabetes on its own to restore glycemic control in all recipients. Our in vitro studies help to elucidate the mechanisms including reduction of cytokine stress by which the HMCs support islet graft protection in vivo. Derivation, stability, and scalability of the HMC source may offer unique advantages for clinical applications, including fewer islets needed for successful islet transplantation.

Regulation of Blood Glucose Using Islets Encapsulated in a Melanin-Modified Immune-Shielding Hydrogel

Islet transplantation is currently a promising treatment for type 1 diabetes mellitus. However, the foreign body reaction and retrieval difficulty often lead to transplantation failure and hinder the clinical application. To address these two challenges, we propose a balanced charged sodium alginate-polyethyleneimine-melanin (SA-PEI-Melanin) threadlike hydrogel with immune shielding and retrievable properties. The attractiveness of this study lies in that the introduction of melanin can stimulate insulin secretion, especially under near-infrared (NIR) irradiation. After demonstrating a good immune-shielding effect, we performed an in vivo transplantation experiment. The results showed that the blood glucose level in the SA-PEI-Melanin group was stably controlled below the diabetic blood glucose criterion, and this blood glucose level could be further adjusted after NIR irradiation. In addition, the evaluation after retrieving the SA-PEI-Melanin hydrogel indicated that the islets still maintained a normal physiological function, further proving its excellent immunological protection. This study provides a new approach for the accurate regulation of blood glucose in patients with type 1 diabetes mellitus and contributes to developing a promising transplant system to reconcile real-time and precise light-defined insulin secretion regulation.

3D Bioprinting and Translation of Beta Cell Replacement Therapies for Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disorder in which the body's own immune system selectively attacks beta cells within pancreatic islets resulting in insufficient insulin production and loss of the ability to regulate blood glucose (BG) levels. Currently, the standard of care consists of BG level monitoring and insulin administration, which are essential to avoid the consequences of dysglycemia and long-term complications. Although recent advances in continuous glucose monitoring and automated insulin delivery systems have resulted in improved clinical outcomes for users, nearly 80% of people with T1D fail to achieve their target hemoglobin A1c (HbA1c) levels defined by the American Diabetes Association. Intraportal islet transplantation into immunosuppressed individuals with T1D suffering from impaired awareness of hypoglycemia has resulted in lower HbA1c, elimination of severe hypoglycemic events, and insulin independence, demonstrating the unique potential of beta cell replacement therapy (BCRT) in providing optimal glycemic control and a functional cure for T1D. BCRTs need to maximize cell engraftment, long-term survival, and function in the absence of immunosuppression to provide meaningful clinical outcomes to all people living with T1D. One innovative technology that could enable widespread translation of this approach into the clinic is three-dimensional (3D) bioprinting. Herein, we review how bioprinting could facilitate translation of BCRTs as well as the current and forthcoming techniques used for bioprinting of a BCRT product. We discuss the strengths and weaknesses of 3D bioprinting in this context in addition to the road ahead for the development of BCRTs. Impact statement Significant research developments in beta cell replacement therapies show its promise in providing a functional cure for type 1 diabetes (T1D); yet, their widespread clinical use has been difficult to achieve. This review provides a brief overview of the requirements for a beta cell replacement product followed by a discussion on both the promise and limitations of three-dimensional bioprinting in facilitating the fabrication of such products to enable translation into the clinic. Advancements in this area could be a key component to unlocking the safety and effectiveness of beta cell therapy for T1D.

Co-Microencapsulation of Islets and MSC CellSaics, Mosaic-Like Aggregates of MSCs and Recombinant Peptide Pieces, and Therapeutic Effects of Their Subcutaneous Transplantation on Diabetes

The subcutaneous transplantation of microencapsulated islets has been extensively studied as a therapeutic approach for type I diabetes. However, due to the lower vascular density and strong inflammatory response in the subcutaneous area, there have been few reports of successfully normalized blood glucose levels. To address this issue, we developed mosaic-like aggregates comprised of mesenchymal stem cells (MSCs) and recombinant peptide pieces called MSC CellSaics, which provide a continuous release of angiogenic factors and anti-inflammatory cytokines. Our previous report revealed that the diabetes of immunodeficient diabetic model mice was reversed by the subcutaneous co-transplantation of the MSC CellSaics and rat islets. In this study, we focused on the development of immune-isolating microcapsules to co-encapsulate the MSC CellSaics and rat islets, and their therapeutic efficiency via subcutaneous transplantation into immunocompetent diabetic model mice. As blood glucose level was monitored for 28 days following transplantation, the normalization rate of the new immuno-isolating microcapsules was confirmed to be significantly higher than those of the microcapsules without the MSC CellSaics, and the MSC CellSaics transplanted outside the microcapsules (p < 0.01). Furthermore, the number of islets required for the treatment was reduced. In the stained sections, a larger number/area of blood vessels was observed around the new immuno-isolating microcapsules, which suggests that angiogenic factors secreted by the MSC CellSaics through the microcapsules function locally for their enhanced efficacy.

A New Islet Transplantation Method Combining Mesenchymal Stem Cells with Recombinant Peptide Pieces, Microencapsulated Islets, and Mesh Bags

Microencapsulated islet transplantation was widely studied as a promising treatment for type 1 diabetes mellitus. However, micro-encapsulated islet transplantation has the following problems—early dysfunction of the islets due to the inflammatory reaction at the transplantation site, and hyponutrition and hypoxia due to a lack of blood vessels around the transplantation site, and difficulty in removal of the islets. On the other hand, we proposed a cell transplantation technique called CellSaic, which was reported to enhance the vascular induction effect of mesenchymal stem cells (MSCs) in CellSaic form, and to enhance the effect of islet transplantation through co-transplantation. Therefore, we performed islet transplantation in diabetic mice by combining three components—microencapsulated islets, MSC-CellSaic, and a mesh bag that encapsulates them and enables their removal. Mesh pockets were implanted in the peritoneal cavity of Balb/c mice as implantation sites. After 4 weeks of implantation, a pocket was opened and transplanted with (1) pancreatic islets, (2) microencapsulated islets, and (3) microencapsulated islets + MSC-CellSaic. Four weeks of observation of blood glucose levels showed that the MSC-CellSaic co-transplant group showed a marked decrease in blood glucose levels, compared to the other groups. A three-component configuration of microcapsules, MSC-CellSaic, and mesh bag was shown to enhance the efficacy of islet transplantation.

Mesenchymal stem cell derived extracellular vesicles: promising immunomodulators against autoimmune, autoinflammatory disorders and SARS-CoV-2 infection

Discovery of novel and broad-acting immunomodulators is of critical importance for the prevention and treatment of disorders occurring due to overexuberant immune responseincluding SARS-CoV-2 triggered cytokine storm leading to lung pathology and mortality during the ongoing viral pandemic. Mesenchymal stem/stromal cells (MSCs), highly regarded for their regenerative capacities, also possessesremarkable immunoregulatory functions affecting all types of innate and adaptive immune cells. Owing to that, MSCs have been heavily investigated in clinic for the treatment of autoimmune and inflammatory diseases along with transplant rejection. Extensive research in the last decaderevealed that MSCs carry out most of their functions through paracrine factors which are soluble mediators and extracellular vesicles (EVs). EVs, including exosomes and microvesicles, are an efficient way of intercellular communication due to their unique ability to carry biological messages such as transcription factors, growth factors, cytokines, mRNAs and miRNAs over long distances. EVs originate through direct budding of the cell membrane or the endosomal secretion pathway and they consist of the cytosolic and membrane components of their parent cell. Therefore, they are able to mimic the characteristics of the parent cell, affecting the target cells upon binding or internalization. EVs secreted by MSCs are emerging as a cell-free alternative to MSC-based therapies. MSC EVs are being tested in preclinical and clinical settings where they exhibit exceptional immunosuppressivecapacity. They regulate the migration, proliferation, activation and polarization of various immune cells, promoting a tolerogenic immune response while inhibiting inflammatory response. Being as effective immunomodulators as their parent cells, MSC EVs are also preferable over MSC-based therapies due to their lower risk of immunogenicity, tumorigenicity and overall superior safety. In this review, we present the outcomes of preclinical and clinical studies utilizing MSC EVs as therapeutic agents for the treatment of a wide variety of immunological disorders.

Transplantation of human dental pulp stem cells in streptozotocin-induced diabetic rats

Type 1 diabetes mellitus (T1DM) is a chronic metabolic disease caused by the destruction of pancreatic β-cells. Human dental pulp stem cells represent a promising source for cell-based therapies, owing to their easy, minimally invasive surgical access, and high proliferative capacity. It was reported that human dental pulp stem cells can differentiate into a pancreatic cell lineage in vitro; however, few studies have investigated their effects on diabetes. Our study aimed to investigate the therapeutic potential of intravenous and intrapancreatic transplantation of human dental pulp stem cells in a rat model of streptozotocin-induced type 1 diabetes. Forty Sprague Dawley male rats were randomly categorized into four groups: control, diabetic (STZ), intravenous treatment group (IV), and intrapancreatic treatment group (IP). Human dental pulp stem cells (1 × 10⁶ cells) or vehicle were injected into the pancreas or tail vein 7 days after streptozotocin injection. Fasting blood glucose levels were monitored weekly. Glucose tolerance test, rat and human serum insulin and C-peptide, pancreas histology, and caspase-3, vascular endothelial growth factor, and Ki67 expression in pancreatic tissues were assessed 28 days post-transplantation. We found that both IV and IP transplantation of human dental pulp stem cells reduced blood glucose and increased levels of rat and human serum insulin and C-peptide. The cells engrafted and survived in the streptozotocin-injured pancreas. Islet-like clusters and scattered human dental pulp stem cells expressing insulin were observed in the pancreas of diabetic rats with some difference in the distribution pattern between the two injection routes. RT-PCR analyses revealed the expression of the human-specific pancreatic β-cell genes neurogenin 3 (NGN3), paired box 4 (PAX4), glucose transporter 2 (GLUT2), and insulin in the pancreatic tissues of both the IP and IV groups. In addition, the transplanted cells downregulated the expression of caspase-3 and upregulated the expression of vascular endothelial growth factor and Ki67, suggesting that the injected cells exerted pro-angiogenetic and antiapoptotic effects, and promoted endogenous β-cell replication. Our study is the first to show that human dental pulp stem cells can migrate and survive within streptozotocin-injured pancreas, and induce antidiabetic effects through the differentiation and replacement of lost β-cells and paracrine-mediated pancreatic regeneration. Thus, human dental pulp stem cells may have therapeutic potential to treat patients with long term T1DM.

Microvessel Network Formation and Interactions with Pancreatic Islets in Three-Dimensional Chip Cultures

The pancreatic islet is a highly vascularized micro-organ, and rapid revascularization postislet transplantation is important for islet survival and function. However, the various mechanisms involved in islet revascularization are not fully understood, and we currently lack good in vitro platforms to explore this. Our aim for this study was to generate perfusable microvascular networks in a microfluidic chip device, in which islets could be easily integrated, to establish an in vitro platform for investigations on islet-microvasculature interactions. We compared the ability of mesenchymal stem cells (MSCs) and fibroblasts to support microvascular network formation by human umbilical vein endothelial cells (HUVECs) and human induced pluripotent stem cell-derived endothelial colony-forming cell in two-dimensional and three-dimensional models of angiogenesis, and tested the effect of different culture media on microvessel formation. HUVECs that were supported by MSCs formed patent and perfusable networks in a fibrin gel, whereas networks supported by fibroblasts rapidly regressed. Network morphology could be controlled by adjusting relative cell numbers and densities. Incorporation of isolated rat islets demonstrated that islets recruit local microvasculature in vitro, but that the microvessels did not invade islets, at least during the course of these studies. This in vitro microvascularization platform can provide a useful tool to study how various parameters affect islet integration with microvascular networks and could also be utilized for studies of vascularization of other organ systems. Impact statement To improve pancreatic islet graft survival and function posttransplantation, rapid and adequate revascularization is critical. Efforts to improve islet revascularization are demanding due to an insufficient understanding of the mechanisms involved in the process. We have applied a microfluidics platform to generate microvascular networks, and by incorporating pancreatic islets, we were able to study microvasculature-islet interactions in real time. This platform can provide a useful tool to study islet integration with microvascular networks, and could be utilized for studies of vascularization of other organ systems. Moreover, this work may be adapted toward developing a prevascularized islet construct for transplantation.

Review of Advanced Hydrogel-Based Cell Encapsulation Systems for Insulin Delivery in Type 1 Diabetes Mellitus

: Type 1 Diabetes Mellitus (T1DM) is characterized by the autoimmune destruction of β-cells in the pancreatic islets. In this regard, islet transplantation aims for the replacement of the damaged β-cells through minimally invasive surgical procedures, thereby being the most suitable strategy to cure T1DM. Unfortunately, this procedure still has limitations for its widespread clinical application, including the need for long-term immunosuppression, the lack of pancreas donors and the loss of a large percentage of islets after transplantation. To overcome the aforementioned issues, islets can be encapsulated within hydrogel-like biomaterials to diminish the loss of islets, to protect the islets resulting in a reduction or elimination of immunosuppression and to enable the use of other insulin-producing cell sources. This review aims to provide an update on the different hydrogel-based encapsulation strategies of insulin-producing cells, highlighting the advantages and drawbacks for a successful clinical application.

The Tumor-Immune Response Is Not Compromised by Mesenchymal Stromal Cells in Humanized Mice

Therapeutic uses of mesenchymal stromal cells (MSCs) have emerged over the past decade. Yet, their effect on tumor growth remains highly debated, particularly in an immune competent environment. In this study, we wanted to investigate the impact of human umbilical cord-derived MSCs (hUC-MSCs) on tumor growth in humanized mice generated by the human adoptive transfer of PBMCs or the cotransplantation of hematopoietic stem cells and human thymic tissue (human BLT [Hu-BLT]). Our results showed that the growth and immune rejection of engineered human fibroblastic tumors was not altered by the injection of hUC-MSCs in immune-deficient or humanized mice, respectively. This was observed whether tumor cells were injected s.c. or i.v. and independently of the injection route of the hUC-MSCs. Moreover, only in Hu-BLT mice did hUC-MSCs have some effects on the tumor-immune infiltrate, yet without altering tumor growth. These results demonstrate that hUC-MSCs do not promote fibroblastic tumor growth and neither do they prevent tumor infiltration and rejection by immune cells in humanized mice.

iPSC-derived MSC therapy induces immune tolerance and supports long-term graft survival in mouse orthotopic tracheal transplants

Background

Lung transplantation is a life-saving surgical replacement of diseased lungs in patients with end-stage respiratory malfunctions. Despite remarkable short-term recovery, long-term lung survival continues to face several major challenges, including chronic rejection and severe toxic side effects due to global immunosuppression. Stem cell-based immunotherapy has been recognized as a crucial immunoregulatory regimen in various preclinical and clinical studies. Despite initial therapeutic outcomes, conventional stem cells face key limitations. The novel Cymerus™ manufacturing facilitates production of a virtually limitless supply of consistent human induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells, which could play a key role in selective immunosuppression and graft repair during rejection.

Methods

Here, we demonstrated the impact of iPSC-derived human MSCs on the development of immune tolerance and long-term graft survival in mouse orthotopic airway allografts. BALB/c → C57BL/6 allografts were reconstituted with iPSC-derived MSCs (2 million/transplant/at d0), and allografts were examined for regulatory T cells (Tregs), oxygenation, microvascular blood flow, airway epithelium, and collagen deposition during rejection.

Results

We demonstrated that iPSC-derived MSC treatment leads to significant increases in hTSG-6 protein, followed by an upregulation of mouse Tregs and IL-5, IL-10, and IL-15 cytokines, which augments graft microvascular blood flow and oxygenation, and thereby maintained a healthy airway epithelium and prevented the subepithelial deposition of collagen at d90 post transplantation.

Conclusions

Collectively, these data confirmed that iPSC-derived MSC-mediated immunosuppression has potential to establish immune tolerance and rescue allograft from sustained hypoxic/ischemic phase, and subsequently limits long-term airway epithelial injury and collagen progression, which therapeutically warrant a study of Cymerus iPSC-derived MSCs as a potential management option for immunosuppression in transplant recipients.

Adipose tissue-derived mesenchymal stem cells rescue the function of islets transplanted in sub-therapeutic numbers via their angiogenic properties

A significant proportion of islets are lost following transplantation due to hypoxia and inflammation. We hypothesize that adipose tissue-derived mesenchymal stem cells (AD-MSCs) can rescue a sub-therapeutic number of transplanted islets by helping them establish a new blood supply and reducing inflammation. Diabetic mice received syngeneic transplantation with 75 (minimal), 150 (sub-therapeutic), or 225 (therapeutic) islets, with or without 1 × 10⁶ mouse AD-MSCs. Fasting blood glucose (FBG) values were measured over 6 weeks with tissue samples collected for islet structure and morphology (H&E, insulin/glucagon staining). Histological and immunohistochemical analyses of islets were also performed at 2 weeks in animals transplanted with a sub-therapeutic number of islets, with and without AD-MSCs, to determine new blood vessel formation, the presence of pro-angiogenic factors facilitating revascularization, and the degree of inflammation. AD-MSCs had no beneficial effect on FBG values when co-transplanted with a minimal or therapeutic number of islets. However, AD-MSCs significantly reduced FBG values and restored glycemic control in diabetic animals transplanted with a sub-therapeutic number of islets. Islets co-transplanted with AD-MSCs preserved their native morphology and organization and exhibited less aggregation when compared to islets transplanted alone. In the sub-therapeutic group, AD-MSCs significantly increased islet revascularization and the expression of angiogenic factors including hepatocyte growth factor (HGF) and angiopoietin-1 (Ang-1) while also reducing inflammation. AD-MSCs can rescue the function of islets when transplanted in a sub-therapeutic number, for at least 6 weeks, via their ability to maintain islet architecture while concurrently facilitating islet revascularization and reducing inflammation.

Stem cells as a potential therapy for diabetes mellitus: a call-to-action in Latin America

Latin America is a fast-growing region that currently faces unique challenges in the treatment of all forms of diabetes mellitus. The burden of this disease will be even greater in the coming years due, in part, to the large proportion of young adults living in urban areas and engaging in unhealthy lifestyles. Unfortunately, the national health systems in Latin-American countries are unprepared and urgently need to reorganize their health care services to achieve diabetic therapeutic goals. Stem cell research is attracting increasing attention as a promising and fast-growing field in Latin America. As future healthcare systems will include the development of regenerative medicine through stem cell research, Latin America is urged to issue a call-to-action on stem cell research. Increased efforts are required in studies focused on stem cells for the treatment of diabetes. In this review, we aim to inform physicians, researchers, patients and funding sources about the advances in stem cell research for possible future applications in diabetes mellitus. Emerging studies are demonstrating the potential of stem cells for β cell differentiation and pancreatic regeneration. The major economic burden implicated in patients with diabetes complications suggests that stem cell research may relieve diabetic complications. Closer attention should be paid to stem cell research in the future as an alternative treatment for diabetes mellitus.

The Fate of Allogeneic Pancreatic Islets following Intraportal Transplantation: Challenges and Solutions

Pancreatic islet transplantation as a therapeutic option for type 1 diabetes mellitus is gaining widespread attention because this approach can restore physiological insulin secretion, minimize the risk of hypoglycemic unawareness, and reduce the risk of death due to severe hypoglycemia. However, there are many obstacles contributing to the early mass loss of the islets and progressive islet loss in the late stages of clinical islet transplantation, including hypoxia injury, instant blood-mediated inflammatory reactions, inflammatory cytokines, immune rejection, metabolic exhaustion, and immunosuppression-related toxicity that is detrimental to the islet allograft. Here, we discuss the fate of intrahepatic islets infused through the portal vein and propose potential interventions to promote islet allograft survival and improve long-term graft function.

Reduction of marginal mass required for successful islet transplantation in a diabetic rat model using adipose tissue-derived mesenchymal stromal cells

BACKGROUND AIMS

Adipose tissue-derived mesenchymal stromal cells (AT-MSCs), widely known as multipotent progenitors, release several cytokines that support cell survival and repair. There are in vitro and in vivo studies reporting the regenerative role of AT-MSCs possibly mediated by their protective effects on functional islet cells as well as their capacity to differentiate into insulin-producing cells (IPCs).

METHODS

On such a basis, our goal in the present study was to use three different models including direct and indirect co-cultures and islet-derived conditioned medium (CM) to differentiate AT-MSCs into IPCs and to illuminate the molecular mechanisms of the beneficial impact of AT-MSCs on pancreatic islet functionality. Furthermore, we combined in vitro co-culture of islets and AT-MSCs with in vivo assessment of islet graft function to assess whether co-transplantation of islets with AT-MSCs can reduce marginal mass required for successful islet transplantation and prolong graft function in a diabetic rat model.

RESULTS

Our findings demonstrated that AT-MSCs are suitable for creating a microenvironment favorable for the repair and longevity of the pancreas β cells through the improvement of islet survival and maintenance of cell morphology and insulin secretion due to their potent properties in differentiation. Most importantly, hybrid transplantation of islets with AT-MSCs significantly promoted survival, engraftment and insulin-producing function of the graft and reduced the islet mass required for reversal of diabetes.

CONCLUSIONS

This strategy might be of therapeutic potential solving the problem of donor islet material loss that currently limits the application of allogeneic islet transplantation as a more widespread therapy for type 1 diabetes.

Human mesenchymal-stem-cells-derived exosomes are important in enhancing porcine islet resistance to hypoxia

BACKGROUND

Hypoxia-induced damage is one of the key factors associated with islet graft dysfunction. Mesenchymal stem cells (MSCs) could be used to enhance the therapeutic effect of islet transplantation due to their paracrine potential such as exosomes. In this study, we investigated whether exosomes from human umbilical cord-derived MSC-conditioned medium (hu-MSC-CM) could increase the survival and function of neonatal porcine islet cell clusters (NICCs) exposed to hypoxia.

METHODS

Neonatal porcine islet cell clusters were cultured with hu-MSC-CM, with or without exosomes, and native medium RPMI-1640 (Control) under hypoxic conditions (1% O₂ ). The effects of exosomes on NICCs viability and function in vitro were examined by FACS, the Loops system, and the Extracellular Flux assay, respectively.

RESULTS

Compared with NICCs cultured in RPMI-1640 medium and hu-MSC-CM without exosomes, the survival ratio, viability, and function increased in NICCs cultured in hu-MSC-CM with exosomes.

CONCLUSIONS

This study found that hu-MSC-CM could protect NICCs from hypoxia-induced dysfunction, and exosomes played an important role in hypoxic resistance, suggesting a potential strategy to improve islet transplantation outcomes.

Early islets and mesenchyme from an injured adult pancreas improve syngeneic engraftments and islet graft function in diabetic rats

A decrease in mass of isografts and a decline in islet function are major challenges in islet transplantations. Despite this, transplantation of 84 h harvested pancreatic duct ligation (PDL) tissues have been shown to have the same functional ability to foetal pancreata, but there was only 40% success in reverting hyperglycaemia. We tested the potential of early islets with mesenchymal stromal cells (MSCs) to promote isogeneic grafts survival and to restore normoglycemia in diabetic rats, in comparison with late islets. Islets were isolated from injured adult pancreata of donor rats at 24 h post ligation either with MSCs (24 h islet/MSC+) or without MSCs (24 h islet/MSC-), and at 84 h without MSCs (84 h islet/MSC-). These cells were transplanted under the renal capsule of syngeneic STZ-diabetic recipient rats. The islet grafts were monitored using the BGLs of recipients and the immunohistomorphology of the grafts were analysed using anti-insulin and anti-Ki67 antibodies. The mean BGL in 24 h islet/MSC+ recipients was reduced over time toward the control value. The curves of the mean BGLs in the control islet/MSC- and the 24 h islet/MSC- recipients dropped significantly below the control normal glucose group's levels to reach their nadirs on weeks 4 and 6, respectively. Both curves had a peak overshoot on week 9, with no statistical significant difference between them. Engrafted islets were evident in these recipients, lasted for 5 and 6 weeks and correspondingly survived failure. However, insulin+ cells were present in the isografts of all recipients; but, only isografts in the 24 h islet/MSC+ presented with a homogenous subcapsular beta cell mass. In addition, the tendency of 24 h islet/MSC- to restore normoglycaemia with its survival capacity was statistically highly significant compared to the 84 islet/MSC- recipients (80%; 20%; p = 0.001). Transplantation of early islets with MSCs from injured adult pancreata prolongs islet graft survival and improves isograft function in diabetic rats. This novel observation requires much further exploration for its clinical application, but this model already provides hope for new sources of donor islets for transplantation.

The journey of islet cell transplantation and future development

Intraportal islet transplantation has proven to be efficacious in preventing severe hypoglycemia and restoring insulin independence in selected patients with type 1 diabetes. Multiple islet infusions are often required to achieve and maintain insulin independence. Many challenges remain in clinical islet transplantation, including substantial islet cell loss early and late after islet infusion. Contributions to graft loss include the instant blood-mediated inflammatory reaction, potent host auto- and alloimmune responses, and beta cell toxicity from immunosuppressive agents. Protective strategies are being tested to circumvent several of these events including exploration of alternative transplantation sites, stem cell-derived insulin producing cell therapies, co-transplantation with mesenchymal stem cells or exploration of novel immune protective agents. Herein, we provide a brief introduction and history of islet cell transplantation, limitations associated with this procedure and methods to alleviate islet cell loss as a means to improve engraftment outcomes.

Stimulation of vascularization of a subcutaneous scaffold applicable for pancreatic islet-transplantation enhances immediate post-transplant islet graft function but not long-term normoglycemia

The liver as transplantation site for pancreatic islets is associated with significant loss of islets, which can be prevented by grafting in a prevascularized, subcutaneous scaffold. Supporting vascularization of a scaffold to limit the period of ischemia is challenging and was developed here by applying liposomes for controlled release of angiogenic factors. The angiogenic capacity of platelet-derived growth factor, vascular endothelial growth factor, acidic fibroblast growth factor (aFGF), and basic FGF were compared in a tube formation assay. Furthermore, the release kinetics of different liposome compositions were tested. aFGF and L-α-phosphatidylcholine/cholesterol liposomes were selected to support vascularization. Two dosages of aFGF-liposomes (0.5 and 1.0 μg aFGF per injection) were administered weekly for a month after which islets were transplanted. We observed enhanced efficacy in the immediate post-transplant period compared to the untreated scaffolds. However, on the long-term, glucose levels of the aFGF treated animals started to increase to diabetic levels. These results suggest that injections with aFGF liposomes do improve vascularization and the immediate restoration of blood glucose levels but does not facilitate the long-term survival of islets. Our data emphasize the need for long-term studies to evaluate potential beneficial and adverse effects of vascularization protocols of scaffolds. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2533-2542, 2017.

Applications of Cell Microencapsulation

The goal of this chapter is to provide an overview of the different purposes for which the cell microencapsulation technology can be used. These include immunoisolation of non-autologous cells used for cell therapy; immobilization of cells for localized (targeted) delivery of therapeutic products to ablate, repair, or regenerate tissue; simultaneous delivery of multiple therapeutic agents in cell therapy; spatial compartmentalization of cells in complex tissue engineering; expansion of cells in culture; and production of different probiotics and metabolites for industrial applications. For each of these applications, specific examples are provided to illustrate how the microencapsulation technology can be utilized to achieve the purpose. However, successful use of the cell microencapsulation technology for whatever purpose will ultimately depend upon careful consideration for the choice of the encapsulating polymers, the method of fabrication (cross-linking) of the microbeads, which affects the permselectivity, the biocompatibility and the mechanical strength of the microbeads as well as environmental parameters such as temperature, humidity, osmotic pressure, and storage solutions.The various applications discussed in this chapter are illustrated in the different chapters of this book and where appropriate relevant images of the microencapsulation products are provided. It is hoped that this outline of the different applications of cell microencapsulation would provide a good platform for tissue engineers, scientists, and clinicians to design novel tissue constructs and products for therapeutic and industrial applications.

Failure of transplantation tolerance induction by autologous regulatory T cells in the pig-to-non-human primate islet xenotransplantation model

BACKGROUND

Islet allotransplantation is a promising way to treat some type 1 diabetic (T1D) patients with frequent hypoglycemic unawareness, and islet xenotransplantation is emerging to overcome the problem of donor organ shortage. Our recent study showing reproducible long-term survival of porcine islets in non-human primates (NHPs) allows us to examine whether autologous regulatory T-cell (Treg) infusion at peri-transplantation period would induce transplantation tolerance in xenotransplantation setting.

METHODS

Two diabetic rhesus monkeys were transplanted with porcine islets from wild-type adult Seoul National University (SNU) miniature pigs with immunosuppression by anti-thymoglobulin (ATG), cobra venom factor, anti-CD154 monoclonal antibody (mAb), and sirolimus. CD4(+) CD25(high) CD127(low) autologous regulatory T cells from the recipients were isolated, ex vivo expanded, and infused at the peri-transplantation period. Blood glucose and porcine C-peptide from the recipients were measured up to 1000 days. Maintenance immunosuppressants including a CD40-CD154 blockade were deliberately discontinued to confirm whether transplantation tolerance was induced by adoptively transferred Tregs.

RESULTS

After pig islet transplantation via portal vein, blood glucose levels of diabetic recipients became normalized and maintained over 6 months while in immunosuppressive maintenance with a CD40-CD154 blockade and sirolimus. However, the engrafted pig islets in the long-term period were fully rejected by activated immune cells, particularly T cells, when immunosuppressants were stopped, showing a failure of transplantation tolerance induction by autologous Tregs.

CONCLUSIONS

Taken together, autologous Tregs infused at the peri-transplantation period failed to induce transplantation tolerance in pig-to-NHP islet xenotransplantation setting.

DAMP production by human islets under low oxygen and nutrients in the presence or absence of an immunoisolating-capsule and necrostatin-1

In between the period of transplantation and revascularization, pancreatic islets are exposed to low-oxygen and low-nutrient conditions. In the present study we mimicked those conditions in vitro to study the involvement of different cell death processes, release of danger-associated molecular patterns (DAMP), and associated in vitro immune activation. Under low-oxygen and low-nutrient conditions, apoptosis, autophagy and necroptosis occur in human islets. Necroptosis is responsible for DAMP-release such as dsDNA, uric acid, and HMGB1. The sensors of the innate immune system able to recognize these DAMPs are mainly TLR, NOD receptors, and C-type lectins. By using cell-lines with a non-functional adaptor molecule MyD88, we were able to show that the islet-derived DAMPs signal mainly via TLR. Immunoisolation in immunoprotective membranes reduced DAMP release and immune activation via retention of the relative large DAMPs in the capsules. Another effective strategy was suppressing necroptosis using the inhibitor nec-1. Although the effect on cell-survival was minor, nec-1 was able to reduce the release of HMGB1 and its associated immune activation. Our data demonstrate that in the immediate post-transplant period islets release DAMPs that in vitro enhance responses of innate immune cells. DAMP release can be reduced in vitro by immunoisolation or intervention with nec-1.

Clinical Trials With Mesenchymal Stem Cells: An Update

In the last year, the promising features of mesenchymal stem cells (MSCs), including their regenerative properties and ability to differentiate into diverse cell lineages, have generated great interest among researchers whose work has offered intriguing perspectives on cell-based therapies for various diseases. Currently the most commonly used adult stem cells in regenerative medicine, MSCs, can be isolated from several tissues, exhibit a strong capacity for replication in vitro, and can differentiate into osteoblasts, chondrocytes, and adipocytes. However, heterogeneous procedures for isolating and cultivating MSCs among laboratories have prompted the International Society for Cellular Therapy (ISCT) to issue criteria for identifying unique populations of these cells. Consequently, the isolation of MSCs according to ISCT criteria has produced heterogeneous, nonclonal cultures of stromal cells containing stem cells with different multipotent properties, committed progenitors, and differentiated cells. Though the nature and functions of MSCs remain unclear, nonclonal stromal cultures obtained from bone marrow and other tissues currently serve as sources of putative MSCs for therapeutic purposes, and several findings underscore their effectiveness in treating different diseases. To date, 493 MSC-based clinical trials, either complete or ongoing, appear in the database of the US National Institutes of Health. In the present article, we provide a comprehensive review of MSC-based clinical trials conducted worldwide that scrutinizes biological properties of MSCs, elucidates recent clinical findings and clinical trial phases of investigation, highlights therapeutic effects of MSCs, and identifies principal criticisms of the use of these cells. In particular, we analyze clinical trials using MSCs for representative diseases, including hematological disease, graft-versus-host disease, organ transplantation, diabetes, inflammatory diseases, and diseases in the liver, kidney, and lung, as well as cardiovascular, bone and cartilage, neurological, and autoimmune diseases.

Mesenchymal stem cells in the treatment of type 1 diabetes mellitus

Diabetes mellitus type 1 is a form of diabetes mellitus that results from the autoimmune destruction of insulin-producing beta cells in the pancreas. The current gold standard therapy for pancreas transplantation has limitations because of the long list of waiting patients and the limited supply of donor pancreas. Mesenchymal stem cells (MSCs), a relatively new potential therapy in various fields, have already made their mark in the young field of regenerative medicine. Recent studies have shown that the implantation of MSCs decreases glucose levels through paracrine influences rather than through direct transdifferentiation into insulin-producing cells. Therefore, these cells may use pro-angiogenic and immunomodulatory effects to control diabetes following the cotransplantation with pancreatic islets. In this review, we present and discuss new approaches of using MSCs in the treatment of diabetes mellitus type 1.

Immunological and technical considerations in application of alginate-based microencapsulation systems

Islets encapsulated in immunoprotective microcapsules are being proposed as an alternative for insulin therapy for treatment of type 1 diabetes. Many materials for producing microcapsules have been proposed but only alginate does currently qualify as ready for clinical application. However, many different alginate-based capsule systems do exist. A pitfall in the field is that these systems are applied without a targeted strategy with varying degrees of success as a consequence. In the current review, the different properties of alginate-based systems are reviewed in view of future application in humans. The use of allogeneic and xenogeneic islet sources are discussed with acknowledging the different degrees of immune protection the encapsulation system should supply. Also issues such as oxygen supply and the role of danger associated molecular patterns (DAMPS) in immune activation are being reviewed. A common property of the encapsulation systems is that alginates for medical application should have an extreme high degree of purity and lack pathogen-associated molecular patterns (PAMPs) to avoid activation of the recipient’s immune system. Up to now, non-inflammatory alginates are only produced on a lab-scale and are not yet commercially available. This is a major pitfall on the route to human application. Also the lack of predictive pre-clinical models is a burden. The principle differences between relevant innate and adaptive immune responses in humans and other species are reviewed. Especially, the extreme differences between the immune system of non-human primates and humans are cumbersome as non-human primates may not be predictive of the immune responses in humans, as opposed to the popular belief of regulatory agencies. Current insight is that although the technology is versatile major research efforts are required for identifying the mechanical, immunological, and physico-chemical requirements that alginate-based capsules should meet for successful human application.