Trophic molecules derived from human mesenchymal stem cells enhance survival, function, and angiogenesis of isolated islets after transplantation

Mesenchymal stem cells: environmentally responsive therapeutics for regenerative medicine

Mesenchymal stem cells (MSCs) are partially defined by their ability to differentiate into tissues including bone, cartilage and adipose in vitro, but it is their trophic, paracrine and immunomodulatory functions that may have the greatest therapeutic impact in vivo. Unlike pharmaceutical treatments that deliver a single agent at a specific dose, MSCs are site regulated and secrete bioactive factors and signals at variable concentrations in response to local microenvironmental cues. Significant progress has been made in understanding the biochemical and metabolic mechanisms and feedback associated with MSC response. The anti-inflammatory and immunomodulatory capacity of MSC may be paramount in the restoration of localized or systemic conditions for normal healing and tissue regeneration. Allogeneic MSC treatments, categorized as a drug by regulatory agencies, have been widely pursued, but new studies demonstrate the efficacy of autologous MSC therapies, even for individuals affected by a disease state. Safety and regulatory concerns surrounding allogeneic cell preparations make autologous and minimally manipulated cell therapies an attractive option for many regenerative, anti-inflammatory and autoimmune applications.

Trophic effect of adipose tissue-derived stem cells on porcine islet cells

BACKGROUND

Adipose tissue-derived stem cells (ADSCs), which are widely known as multipotent progenitor cells, release several cytokines that support cell survival and repair. The aim of this study was to investigate whether ADSC-secreted molecules could induce a trophic effect in pancreatic islet culture conditions in vitro.

MATERIALS AND METHODS

We cocultured porcine islet cells with ADSCs using a transwell system for 48 h and evaluated the viability of islet cells. We also determined the concentration levels of cytokines and insulin in the supernatant of the culture medium. We used anti-vascular endothelial growth factor (VEGF) and anti-interleukin (IL)-6 receptor antibodies to investigate the effect of VEGF and IL-6 on islet cells.

RESULTS

ADSCs improved the viability of islet cells in the absence of cell-cell contact (P < 0.05). VEGF and IL-6 levels in the culture medium increased when islet cells were cocultured with ADSCs (P < 0.05). Furthermore, inhibition of VEGF decreased the viability of islet cells (P < 0.05); however, inhibition of IL-6 did not affect islet cell viability.

CONCLUSIONS

These results suggested that trophic factors, particularly VEGF, secreted by human ADSCs enhanced the survival and function of porcine islet cells.

Gene expression changes in the injured spinal cord following transplantation of mesenchymal stem cells or olfactory ensheathing cells

Transplantation of bone marrow derived mesenchymal stromal cells (MSC) or olfactory ensheathing cells (OEC) have demonstrated beneficial effects after spinal cord injury (SCI), providing tissue protection and improving the functional recovery. However, the changes induced by these cells after their transplantation into the injured spinal cord remain largely unknown. We analyzed the changes in the spinal cord transcriptome after a contusion injury and MSC or OEC transplantation. The cells were injected immediately or 7 days after the injury. The mRNA of the spinal cord injured segment was extracted and analyzed by microarray at 2 and 7 days after cell grafting. The gene profiles were analyzed by clustering and functional enrichment analysis based on the Gene Ontology database. We found that both MSC and OEC transplanted acutely after injury induce an early up-regulation of genes related to tissue protection and regeneration. In contrast, cells transplanted at 7 days after injury down-regulate genes related to tissue regeneration. The most important change after MSC or OEC transplant was a marked increase in expression of genes associated with foreign body response and adaptive immune response. These data suggest a regulatory effect of MSC and OEC transplantation after SCI regarding tissue repair processes, but a fast rejection response to the grafted cells. Our results provide an initial step to determine the mechanisms of action and to optimize cell therapy for SCI.

Bioengineered sites for islet cell transplantation

Although islet transplantation has demonstrated its potential use in treating type 1 diabetes, this remains limited by the need for daily immunosuppression. Islet encapsulation was then proposed with a view to avoiding any immunosuppressive regimen and related side effects. In order to obtain a standard clinical procedure in terms of safety and reproducibility, two important factors have to be taken into account: the encapsulation design (which determines the graft volume) and the implantation site. Indeed, the implantation site should meet certain requirements: (1) its space must be large enough for the volume of transplanted tissues; (2) there must be proximity to abundant vascularization with a good oxygen supply; (3) there must be real-time access to physiologically representative blood glucose levels; (4) there must be easy access for implantation and the reversibility of the procedure (for safety); and finally, (5) the site should have minimal early inflammatory reaction and promote long-term survival. The aim of this article is to review possible preclinical/clinical implantation sites (in comparison with free islets) for encapsulated islet transplantation as a function of the encapsulation design: macro/microcapsules and conformal coating.

Renal transplantation from elderly living donors

Acceptance of elderly living kidney donors remains controversial due to the higher incidence of comorbidity and greater risk of postoperative complications. This is a review of publications in the English language between 2000 and 2013 about renal transplantation from elderly living donors to determine trends and effects of donation, and the outcomes of such transplantation. The last decade witnessed a 50% increase in living kidney donor transplants, with a disproportionate increase in donors >60 years. There is no accelerated loss of kidney function following donation, and the incidence of established renal failure (ERF) and hypertension among donors is similar to that of the general population. The overall incidence of ERF in living donors is about 0.134 per 1000 years. Elderly donors require rigorous assessment and should have a predicted glomerular filtration rate of at least 37.5 mL/min/1.73 m(2) at the age of 80. Though elderly donors had lower glomerular filtration rate before donation, proportionate decline after donation was similar in both young and elderly groups. The risks of delayed graft function, acute rejection, and graft failure in transplants from living donors >65 years are significantly higher than transplants from younger donors. A multicentred, long-term, and prospective database addressing the outcomes of kidneys from elderly living donors is recommended.

Impact of donor and recipient age difference on long-term allograft survival after living donor renal transplantation: analysis of 478 cases

INTRODUCTION

Either deceased or living-related renal transplantation constitutes the best therapeutic option for patients with end-stage renal disease. In this retrospective study, an attempt to identify parameters that affect allograft survival in living donor renal transplantation was made.

METHODS

Between January 2000 and July 2012, 478 adult patients received a renal transplant from a living-related donor in our center and their records were retrospectively reviewed in November 2012. Data concerning donor age, recipient age, donor/recipient age difference, donor/recipient gender, and ABO compatibility/incompatibility were recorded and associated with renal allograft survival rate.

RESULTS

Renal allograft survival rate was 96%, 89.5%, and 77.7% in the first, fifth, and 10th yr after transplantation, respectively. Only the difference between donor and recipient age was statistically significant in relation to graft survival. In cases with age difference >13 yr, graft survival rate was lower from the third yr onward.

CONCLUSIONS

Only the age difference between donor and recipient exerts an adverse impact on graft outcome after living donor renal transplantation, whereas donor age, recipient age, donor/recipient gender, and ABO incompatibility do not significantly influence renal allograft survival.

Proangiogenic hydrogels within macroporous scaffolds enhance islet engraftment in an extrahepatic site

The transplantation of allogeneic islets in recent clinical trials has shown substantial promise as a therapy for type 1 diabetes; however, long-term insulin independence remains inadequate. This has been largely attributed to the current intravascular, hepatic transplant site, which exposes islets to mechanical and inflammatory stresses. A highly macroporous scaffold, housed within an alternative transplant site, can support an ideal environment for islet transplantation by providing three-dimensional distribution of islets, while permitting the infiltration of host vasculature. In the present study, we sought to evaluate the synergistic effect of a proangiogenic hydrogel loaded within the void space of a macroporous poly(dimethylsiloxane) (PDMS) scaffold on islet engraftment. The fibrin-based proangiogenic hydrogel tested presents platelet derived growth factor (PDGF-BB), via a fibronectin (FN) fragment containing growth factor and major integrin binding sites in close proximity. The combination of the proangiogenic hydrogel with PDMS scaffolds resulted in a significant decrease in the time to normoglycemia for syngeneic mouse islet transplants. This benefit was associated with an observed increase in competent vessel branching, as well as mature intraislet vessels. Overall, the addition of the proangiogenic factor PDGF-BB, delivered via the FN fragment-functionalized hydrogel, positively influenced the efficiency of engraftment. These characteristics, along with its ease of retrieval, make this combination of a biostable macroporous scaffold and a degradable proangiogenic hydrogel a supportive structure for insulin-producing cells implanted in extrahepatic sites.

The effect of donor-recipient gender mismatch on short- and long-term graft survival in kidney transplantation: a systematic review and meta-analysis

BACKGROUND

There is no limitation of gender matching in renal transplantation. This study was intended to evaluate its effect on short- and long-term graft survival.

METHODS

PubMed, the Web of Knowledge, Medline, the Cochrane Library, and two additional Chinese databases were searched. The data were then abstracted and meta-analyzed.

RESULTS

14 studies involving 445 279 patients were included. Each study reported data on the four gender matches (male donor-male recipient, MDMR; male donor-female recipient, MDFR; female donor-male recipient, FDMR; female donor-female recipient, FDFR). The pooled risk ratios (RRs) for 0.5-, 1-, 2-, 3-, 5-, and 10-yr graft survival rates showed that the FDMR group had the worst outcomes, and when recipients were female, short-term graft survival was worse, but long-term graft survival was better. The differences between groups changed with time.

CONCLUSIONS

FDMR patients showed poor graft survival. The female recipients had worse short-term graft survival but the best long-term graft survival. This study introduces an important consideration into donor-recipient matching in renal transplantation.

Factors affecting graft survival among patients receiving kidneys from live donors: a single-center experience

Introduction. The aim of this report is to study the graft and patient survival in a large cohort of recipients with an analysis of factors that may affect the final outcomes. Methods. Between March 1976 and March 2008, 1967 consecutive live-donor renal transplants were carried out. Various variables that may have an impact on patients and/or graft survival were studied in two steps. Initially, a univariate analysis was carried out. Thereafter, significant variables were embedded in a stepwise regression analysis. Results. The overall graft survival was 86.7% and 65.5%, at 5 and 10 years, respectively. The projected half-life for grafts was 17.5 years and for patients was 22 years. Five factors had an independent negative impact on graft survival: donor's age, genetic considerations, the type of primary immunosuppression, number of acute rejection episodes, and total steroid dose during the first 3 months after transplantation. Conclusions. Despite refinements in tissue matching techniques and improvements in immunosuppression protocols, an important proportion of grafts is still lost following living donor kidney transplantation, presumably due to chronic allograft nephropathy.

Multiple intravenous infusions of bone marrow mesenchymal stem cells reverse hyperglycemia in experimental type 2 diabetes rats

The worldwide rapid increase in diabetes poses a significant challenge to current therapeutic approaches. Single-dose mesenchymal stem cell (MSC) infusion ameliorates hyperglycemia but fails to restore normoglycemia in diabetic animals. We therefore hypothesized that multiple intravenous MSC infusions may reverse hyperglycemia in type 2 diabetes (T2D) rats. We administered serial allogenous bone-marrow derived MSC infusions (1 × 10(6)cells/infusion) via the tail vein once every 2 weeks to T2D rats, induced by high-fat diet and streptozocin (STZ) administration. Hyperglycemia decreased only transiently after a single infusion in early-phase (1 week) T2D rats, but approximated normal levels after at least three-time infusions. This normal blood level was maintained for at least 9 weeks. Serum concentrations of both insulin and C-peptide were dramatically increased after serial MSC infusions. Oral glucose tolerance tests revealed that glucose metabolism was significantly ameliorated. Immunofluorescence analysis of insulin/glucagon staining revealed the restoration of islet structure and number after multiple MSC treatments. When multiple-MSC treatment was initiated in late-phase (5 week) T2D rats, the results were slightly different. The results of this study suggested that a multiple-MSC infusion strategy offers a viable clinical option for T2D patients.

Living unrelated renal transplantation: a good match for the pediatric candidate?

BACKGROUND/PURPOSE

Living donor kidney transplantation is encouraged for children with end-stage renal disease given the superior survival of living donor grafts, but pediatric candidates are also given preference for kidneys from younger deceased donors.

METHODS

Death-censored graft survival of pediatric kidney-only transplants performed in the U.S. between 1987-2012 was compared across living related (LRRT) (n=7741), living unrelated (LURT) (n=618), and deceased donor renal transplants (DDRT) (n=8945) using Kaplan-Meier analysis, multivariable Cox proportional hazards models, and matched controls analysis.

RESULTS

As expected, HLA mismatch was greater among LURT compared to LRRT (p<0.001). Unadjusted graft survival was lower, particularly long-term, for LURT compared to LRRT (p=0.009). However, LURT graft survival was still superior to DDRT graft survival, even when compared only to deceased donors under age 35 (p=0.002). The difference in graft survival between LURT and LRRT was not seen when adjusting for HLA mismatch, year of transplantation, and donor and recipient characteristics using a Cox model (aHR=1.04, 95% CI: 0.87-1.24, p=0.7) or matched controls (HR=1.02, 95% CI: 0.82-1.27, p=0.9).

CONCLUSION

Survival of LURT grafts is superior to grafts from younger deceased donors and equivalent to LRRT grafts when adjusting for other factors, most notably differences in HLA mismatch.

Electrofusion of mesenchymal stem cells and islet cells for diabetes therapy: a rat model

Islet transplantation is a minimally invasive treatment for severe diabetes. However, it often requires multiple donors to accomplish insulin-independence and the long-term results are not yet satisfying. Therefore, novel ways to overcome these problems have been explored. Isolated islets are fragile and susceptible to pro-apoptotic factors and poorly proliferative. In contrast, mesenchymal stem cells (MSCs) are highly proliferative, anti-apoptotic and pluripotent to differentiate toward various cell types, promote angiogenesis and modulate inflammation, thereby studied as an enhancer of islet function and engraftment. Electrofusion is an efficient method of cell fusion and nuclear reprogramming occurs in hybrid cells between different cell types. Therefore, we hypothesized that electrofusion between MSC and islet cells may yield robust islet cells for diabetes therapy. We establish a method of electrofusion between dispersed islet cells and MSCs in rats. The fusion cells maintained glucose-responsive insulin release for 20 days in vitro. Renal subcapsular transplantation of fusion cells prepared from suboptimal islet mass (1,000 islets) that did not correct hyperglycemia even if co-transplanted with MSCs, caused slow but consistent lowering of blood glucose with significant weight gain within the observation period in streptozotocin-induced diabetic rats. In the fusion cells between rat islet cells and mouse MSCs, RT-PCR showed new expression of both rat MSC-related genes and mouse β-cell-related genes, indicating bidirectional reprogramming of both β-cell and MSCs nuclei. Moreover, decreased caspase3 expression and new expression of Ki-67 in the islet cell nuclei suggested alleviated apoptosis and gain of proliferative capability, respectively. These results show that electrofusion between MSCs and islet cells yield special cells with β-cell function and robustness of MSCs and seems feasible for novel therapeutic strategy for diabetes mellitus.

Human mesenchymal stem cells: a bank perspective on the isolation, characterization and potential of alternative sources for the regeneration of musculoskeletal tissues

The continuous discovery of human mesenchymal stem cells (hMSCs) in different tissues is stirring up a tremendous interest as a cell source for regenerative medicine therapies. Historically, hMSCs have been always considered a sub-population of mononuclear cells present in the bone marrow (BM). Although BM-hMSCs are still nowadays considered as the most promising mesenchymal stem cell population to reach the clinics due to their capacity to differentiate into multiple tissues, hMSCs derived from other adult and fetal tissues have also demonstrated to possess similar differentiation capacities. Furthermore, different reports have highlighted a higher recurrence of hMSCs in some of these tissues as compared to BM. This offer a fascinating panorama for cell banking, since the creation of a stem cell factory could be envisioned where hMSCs are stocked and used for ad hoc clinical applications. In this review, we summarize the main findings and state of the art in hMSCs isolation, characterization, and differentiation from alternative tissue sources and we attempt to compare their potency for musculoskeletal regeneration.

Influence of ischemic microenvironment on human Wharton's Jelly mesenchymal stromal cells

INTRODUCTION

While in vivo studies suggest poor survival of mesenchymal stromal cells (MSCs) after transplantation in ischemic conditions, in vitro studies report diverse effects on proliferation, apoptosis and differentiation of stem/precursor cells of different tissue-origin. The present focus is to understand the influence of ischemic microenvironment on the survival, proliferation, apoptosis, ROS-generation, antioxidant levels, immunophenotypic-expression and neurotrophic factor secretion of Wharton's Jelly (WJ)-MSCs.

METHOD

WJ-MSCs were cultured in normoxic and hypoxic conditions in presence and absence of serum and the end-point parameters were measured at 4 time-points. Cell survival, proliferation, apoptosis, ROS-generation and immunophenotypic-expression were quantitatively detected either by fluorimetry or flow cytometry techniques. ELISA-based methods were used for detection of antioxidant-substrate glutathione (GSH) and neurotrophic factors [vascular endothelial factor (VEGF), hepatocyte growth factor (HGF) and brain-derived neurotrophic factor (BDNF)]. Expression of the antioxidants glutathione peroxidase (GPx) and superoxide dismutase 1 (SOD1), was measured by real-time RT-PCR.

RESULT

Immunophenotypic analysis showed reduction in mesenchymal-marker (CD73, CD90, and CD105) expression under ischemic conditions influenced mainly by hypoxia, whereas the decrease in cell-survival under ischemic condition was mainly as a result of nutrition depletion. This was associated with increased ROS-generation and apoptosis and reduction in antioxidants (GSH, GPx, SOD1). For neurotrophic factors, ELISA-readings showed that VEGF and HGF secretion (which were higher in hypoxia) peaked at 48 h and decreased from 72 h, though BDNF release did not decrease.

DISCUSSION

Therapeutic benefits rendered by WJ-MSCs in in vitro ischemic microenvironment are highest at the 48 h time-point, declining thereafter with time probably due to failure in cellular defense systems and the onset of apoptosis.

CONCLUSION

It is hence clear that the growth factor deficiency is more lethal to the cells than hypoxia in ischemic microenvironment.

Allogeneic bone marrow cocultured with human islets significantly improves islet survival and function in vivo

BACKGROUND

A significant barrier to islet transplantation is the rapid loss of human islet function in vivo. The present study evaluates whether bone marrow (BM) could be used to support human islet survival and function in vivo.

METHODS

We cocultured human islets and BM for 3 weeks before transplantation into the left subrenal capsule of diabetic severe combined immunodeficient mice.

RESULTS

The cocultured human islets before transplantation demonstrated improved viability, increased size, and migration capacity in vitro. After 4 months, animals transplanted with precultured BM/islets exhibited euglycemia and detectable human insulin levels (157 μU/mL), whereas no human insulin was detected in the islet-only transplantation group. Furthermore, the removal of the transplants on day 126 resulted in hyperglycemia, indicating that the reduction of blood glucose was dependent on the transplants. Diabetic mice transplanted with BM/islets demonstrated the longest survival period (130 vs. 40 days for those with islet-only transplants). The transplanted BM/islets showed signs of vascularization and migration from the renal capsule into medulla.

CONCLUSIONS

Our results suggest that BM precultured with human islets may enhance the survival and function of transplanted islets, thus significantly improving the therapeutic efficacy of islet transplantation for type 1 diabetes.

Pre-culturing islets with mesenchymal stromal cells using a direct contact configuration is beneficial for transplantation outcome in diabetic mice

BACKGROUND AIMS

We recently showed that co-transplantation of mesenchymal stromal cells (MSCs) improves islet function and revascularization in vivo. Pre-transplant islet culture is associated with the loss of islet cells. MSCs may enhance islet cell survival or function by direct cell contact mechanisms and soluble mediators. We investigated the capacity of MSCs to improve islet cell survival or β-cell function in vitro using direct and indirect contact islet-MSC configurations. We also investigated whether pre-culturing islets with MSCs improves islet transplantation outcome.

METHODS

The effect of pre-culturing islets with MSCs on islet function in vitro was investigated by measuring glucose-stimulated insulin secretion. The endothelial cell density of fresh islets and islets cultured with or without MSCs was determined by immunohistochemistry. The efficacy of transplanted islets was tested in vivo using a syngeneic streptozotocin-diabetic minimal islet mass model. Graft function was investigated by monitoring blood glucose concentrations.

RESULTS

Indirect islet-MSC co-culture configurations did not improve islet function in vitro. Pre-culturing islets using a direct contact MSC monolayer configuration improved glucose-stimulated insulin secretion in vitro, which correlated with superior islet graft function in vivo. MSC pre-culture had no effect on islet endothelial cell number in vitro or in vivo.

CONCLUSIONS

Pre-culturing islets with MSCs using a direct contact configuration maintains functional β-cell mass in vitro and the capacity of cultured islets to reverse hyperglycemia in diabetic mice.

Co-transplantation of islets with mesenchymal stem cells in microcapsules demonstrates graft outcome can be improved in an isolated-graft model of islet transplantation in mice

BACKGROUND AIMS

Co-transplantation of islets with mesenchymal stem cells (MSCs) has been shown to improve graft outcome in mice, which has been partially attributed to the effects of MSCs on revascularization and preservation of islet morphology. Microencapsulation of islets provides an isolated-graft model of islet transplantation that is non-vascularized and prevents islet aggregation to preserve islet morphology. The aim of this study was to investigate whether MSCs could improve graft outcome in a microencapsulated/isolated-graft model of islet transplantation.

METHODS

Mouse islets and kidney MSCs were co-encapsulated in alginate, and their function was assessed in vitro. A minimal mass of 350 syngeneic islets encapsulated alone or co-encapsulated with MSCs (islet+MSC) were transplanted intraperitoneally into diabetic mice, and blood glucose concentrations were monitored. Capsules were recovered 6 weeks after transplantation, and islet function was assessed.

RESULTS

Islets co-encapsulated with MSCs in vitro had increased glucose-stimulated insulin secretion and content. The average blood glucose concentration of transplanted mice was significantly lower by 3 weeks in the islet+MSC group. By week 6, 71% of the co-encapsulated group were cured compared with 16% of the islet-alone group. Capsules recovered at 6 weeks had greater glucose-stimulated insulin secretion and insulin content in the islet+MSC group.

CONCLUSIONS

MSCs improved the efficacy of microencapsulated islet transplantation. Using an isolated-graft model, we were able to eliminate the impact of MSC-mediated enhancement of revascularization and preservation of islet morphology and demonstrate that the improvement in insulin secretion and content is sustained in vivo and can significantly improve graft outcome.

Potential role of mesenchymal stromal cells in pancreatic islet transplantation

Pancreatic islet transplantation is an attractive option for treatment of type 1 diabetes mellitus but maintaining long term islet function remains challenging. Mesenchymal stromal cells (MSCs), derived from bone marrow or other sources, are being extensively investigated in the clinical setting for their immunomodulatory and tissue regenerative properties. Indeed, MSCs have been already tested in some feasibility studies in the context of islet transplantation. MSCs could be utilized to improve engraftment of pancreatic islets by suppressing inflammatory damage and immune mediated rejection. In addition to their immunomodulatory effects, MSCs are known to provide a supportive microenvironmental niche by secreting paracrine factors and depositing extracellular matrix. These properties could be used for in vivo co-transplantation to improve islet engraftment, or for in vitro co-culture to prime freshly isolated islets prior to implantation. Further, tissue specific pancreatic islet derived MSCs may open new opportunities for its use in islet transplantation as those cells might be more physiological to pancreatic islets.

Identity of tendon stem cells--how much do we know?

Tendon stem cells are multi-potent adult stem cells with broad differentiation plasticity that render them of great importance in cell-based therapies for the repair of tendons. We called them tendon-derived stem cells (TDSCs) to indicate the tissue origin from which the stem cells were isolated in vitro. Based on the work of other sources of MSCs and specific work on TDSCs, some properties of TDSCs have been characterized / implicated in vitro. Despite these findings, tendon stem cells remained controversial cells. This was because MSCs residing in different organs, although very similar, were not identical cells. There is evidence of differences in stem cell-related properties and functions related to tissue origins. Similar to other stem cells, tendon stem cells were identified and characterized in vitro. Their in vivo identities, niche (both anatomical locations and regulators) and roles in tendons were less understood. This review aims to summarize the current evidence of the possible anatomical locations and niche signals regulating the functions of tendon stem cells in vivo. The possible roles of tendon stem cells in tendon healing and non-healing are presented. Finally, the potential strategies for understanding the in vivo identity of tendon stem cells are discussed.

Mesenchymal stem cell-based therapy

Mesenchymal stem cells (MSCs) are multipotent adult stem cells which have self-renewal capacity and differentiation potential into several mesenchymal lineages including bones, cartilages, adipose tissues and tendons. MSCs may repair tissue injuries and prevent immune cell activation and proliferation. Immunomodulation and secretion of growth factors by MSCs have led to realizing the true potential of MSC-based cell therapy. The use of MSCs as immunomodulators has been explored in cell/organ transplant, tissue repair, autoimmune diseases, and prevention of graft vs host disease (GVHD). This review focuses on the clinical applications of MSC-based cell therapy, with particular emphasis on islet transplantation for treating type I diabetes.

The protective effect of adipose-derived stem cells against liver injury by trophic molecules

BACKGROUND

In this study we investigated whether adipose-derived stem cells (ADSCs) had any beneficial protective effects on liver injury and regeneration in vivo. Moreover, we examined whether ADSCs protect hepatocytes via trophic molecules.

MATERIALS AND METHODS

We transplanted ADSCs into mice after 70% hepatectomy and ischemia-reperfusion, and observed liver injury and regeneration after reperfusion. We co-cultured hepatocytes with ADSCs using a Transwell system for 7 d and evaluated the viabilities of hepatocytes and the cytokine levels in the culture medium. Bevacizumab was used to confirm the effect of vascular endothelial growth factor (VEGF) on hepatocytes.

RESULTS

ADSCs improved serum liver function at 6 h after reperfusion in a nonlethal model and stimulated liver regeneration at 24 h after reperfusion in a lethal model. VEGF levels in the culture medium were increased by co-culture ADSCs with hepatocytes. ADSCs improved the viabilities of hepatocytes. The inhibited production of VEGF by bevacizumab did not affect the viability of hepatocytes.

CONCLUSIONS

ADSCs were able to ameliorate liver injury and stimulate liver regeneration in subsequent hepatectomy and ischemia-reperfusion-injured model mice. Furthermore, hepatocytes were protected by the trophic molecules of the ADSCs. However, such protective effects might be provided by mechanisms other than VEGF signaling.

Harnessing the immunomodulatory and tissue repair properties of mesenchymal stem cells to restore β cell function

Islet cell transplantation has therapeutic potential to cure type 1 diabetes (T1D), which is characterized by autoimmune-mediated destruction of insulin-producing β cells. However, current success rates are limited by long-term decline in islet graft function resulting partially from poor revascularization and immune destruction. Mesenchymal stem cells (MSCs) have the potential to enhance islet transplantation and prevent disease progression by a multifaceted approach. MSCs have been shown to be effective at inhibiting inflammatory-mediated immune responses and at promoting tissue regeneration. The immunomodulatory and tissue repairing properties of MSCs may benefit β cell regeneration in the context of T1D. This review will elucidate how MSCs can minimize β cell damage by providing survival signals and simultaneously modulate the immune response by inhibiting activation, and proliferation of several immune cell types. In addition, MSCs can enhance islet graft revascularization, maintaining long-term β cell viability and function.

Induction of beta-cell resistance to hypoxia and technologies for oxygen delivery to transplanted pancreatic islets

Hypoxia is believed to be a crucial factor involved in cell adaptation to environmental stress. Islet transplantation, especially with immunoisolated islets, interrupts vascular connections, resulting in the substantially decreased delivery of oxygen and nutrients to islet cells. Insulin-producing pancreatic beta cells are known to be highly susceptible to oxygen deficiency. Such susceptibility to hypoxia is believed to be one of the main causes of beta-cell death in the post-transplantation period. Different strategies have been developed for the protection of beta cells against hypoxic injury and for oxygen delivery to transplanted islets. The enhancement of beta-cell defense properties against hypoxia has been achieved using various techniques such as gene transfection, drug supplementation, co-culturing with stem cells and cell selection. Technologies for oxygen delivery to transplanted islets include local neovascularization of subcutaneous sites, electrochemical and photosynthetic oxygen generation, oxygen refuelling of bio-artificial pancreas and whole body oxygenation by using hyperbaric therapy. Progress in the field of oxygen technologies for islet transplantation requires a multidisciplinary approach to explore and optimize the interaction between components of the biological system and different technological processes. This review article focuses mainly on the recently developed strategies for oxygenation and protection from hypoxic injury - to achieve stable and long-term normoglycaemia in diabetic patients with transplanted pancreatic islets.

Stem cells as a tool to improve outcomes of islet transplantation

The publication of the promising results of the Edmonton protocol in 2000 generated optimism for islet transplantation as a potential cure for Type 1 Diabetes Mellitus. Unfortunately, follow-up data revealed that less than 10% of patients achieved long-term insulin independence. More recent data from other large trials like the Collaborative Islet Transplant Registry show incremental improvement with 44% of islet transplant recipients maintaining insulin independence at three years of follow-up. Multiple underlying issues have been identified that contribute to islet graft failure, and newer research has attempted to address these problems. Stem cells have been utilized not only as a functional replacement for β cells, but also as companion or supportive cells to address a variety of different obstacles that prevent ideal graft viability and function. In this paper, we outline the manners in which stem cells have been applied to address barriers to the achievement of long-term insulin independence following islet transplantation.

Enhanced function of pancreatic islets co-encapsulated with ECM proteins and mesenchymal stromal cells in a silk hydrogel

Pancreatic islet encapsulation within biosynthetic materials has had limited clinical success due to loss of islet function and cell death. As an alternative encapsulation material, a silk-based scaffold was developed to reestablish the islet microenvironment lost during cell isolation. Islets were encapsulated with ECM proteins (laminin and collagen IV) and mesenchymal stromal cells (MSCs), known to have immunomodulatory properties or to enhance islet cell graft survival and function. After a 7 day in vitro encapsulation, islets remained viable and maintained insulin secretion in response to glucose stimulation. Islets encapsulated with collagen IV, or laminin had increased insulin secretion at day 2 and day 7, respectively. A 3.2-fold synergistic improvement in islet insulin secretion was observed when islets were co-encapsulated with MSCs and ECM proteins. Furthermore, encapsulated islets had increased gene expression of functional genes; insulin I, insulin II, glucagon, somatostatin, and PDX-1, and lower expression of the de-differentiation genes cytokeratin 19 and vimentin compared to non-encapsulated cells. This work demonstrates that encapsulation in silk with both MSCs and ECM proteins enhances islet function and with further development may have potential as a suitable platform for islet delivery in vivo.

Targets and delivery methods for therapeutic angiogenesis in peripheral artery disease

Therapeutic angiogenesis utilizing genetic and cellular modalities in the treatment of arterial obstructive diseases continues to evolve. This is, in part, because the mechanism of vasculogenesis, angiogenesis, and arteriogenesis (the three processes by which the body responds to obstruction of large conduit arteries) is a complex process that is still under investigation. To date, the majority of human trials utilizing molecular, genetic, and cellular modalities for therapeutic angiogenesis in the treatment of peripheral artery disease (PAD) have not shown efficacy. Consequently, the current available knowledge is yet to be translated into novel therapeutic approaches for the treatment of PAD. The aim of this review is to discuss relevant scientific and clinical advances in therapeutic angiogenesis and their potential application in the treatment of ischemic diseases of the peripheral arteries. Additionally, this review article discusses past and recent developments, such as some unconventional approaches that have the potential to be applied as therapeutic targets. The article also includes advances in the delivery of genetic, cellular, and bioactive endothelial growth factors.

Infusion of mesenchymal stem cells ameliorates hyperglycemia in type 2 diabetic rats: identification of a novel role in improving insulin sensitivity

Infusion of mesenchymal stem cells (MSCs) has been shown to effectively lower blood glucose in diabetic individuals, but the mechanism involved could not be adequately explained by their potential role in promoting islet regeneration. We therefore hypothesized that infused MSCs might also contribute to amelioration of the insulin resistance of peripheral insulin target tissues. To test the hypothesis, we induced a diabetic rat model by high-fat diet/streptozotocin (STZ) administration, performed MSC infusion during the early phase (7 days) or late phase (21 days) after STZ injection, and then evaluated the therapeutic effects of MSC infusion and explored the possible mechanisms involved. MSC infusion ameliorated hyperglycemia in rats with type 2 diabetes (T2D). Infusion of MSCs during the early phase not only promoted β-cell function but also ameliorated insulin resistance, whereas infusion in the late phase merely ameliorated insulin resistance. Infusion of MSCs resulted in an increase of GLUT4 expression and an elevation of phosphorylated insulin receptor substrate 1 (IRS-1) and Akt (protein kinase B) in insulin target tissues. This is the first report of MSC treatment improving insulin sensitivity in T2D. These data indicate that multiple roles and mechanisms are involved in the efficacy of MSCs in ameliorating hyperglycemia in T2D.

Mesenchymal stem cells and islet cotransplantation in diabetic rats: improved islet graft revascularization and function by human adipose tissue-derived stem cells preconditioned with natural molecules

Hypoxia plays an important role in limiting the engraftment, survival, and function of intrahepatically transplanted islets. Mesenchymal stem cells (MSCs) were recently used in animal models of islet transplantation not only to reduce allograft rejection but also to promote revascularization. Among different possible origins, adipose tissue represents a novel and good source of MSCs. Moreover, the capability of adipose tissue-derived stem cells (ASCs) to improve islet graft revascularization was recently reported after hybrid transplantation in mice. Within this context, we have previously shown that hyaluronan esters of butyric and retinoic acids can significantly enhance the rescuing potential of human MSCs (hMSCs). Here we evaluated whether ex vivo preconditioning of human ASCs (hASCs) with a mixture of hyaluronic (HA), butyric (BU), and retinoic (RA) acids may result in optimization of graft revascularization after islet/stem cell intrahepatic cotransplantation in syngeneic diabetic rats. We demonstrated that hASCs exposed to the mixture of molecules are able to increase the secretion of vascular endothelial growth factor (VEGF) as well as the transcription of angiogenic genes, including VEGF, KDR (kinase insert domain receptor), and hepatocyte growth factor (HGF). Rats transplanted with islets cocultured with preconditioned hASCs exhibited a better glycemic control than rats transplanted with an equal volume of islets and control hASCs. Cotransplantation with preconditioned hASCs was also associated with enhanced islet revascularization in vivo, as highlighted by graft morphological analysis. The observed increase in islet graft revascularization and function suggests that our method of stem cell preconditioning may represent a novel strategy to remarkably improve the efficacy of islets-hMSCs cotransplantation.

Islet organogenesis, angiogenesis and innervation

The pancreas is characterized by a major component, an exocrine and ductal system involved in digestion, and a minor component, the endocrine islets represented by islet micro-organs that tightly regulate glucose homoeostasis. Pancreatic organogenesis is strictly co-ordinated by transcription factors that are expressed sequentially to yield functional islets capable of maintaining glucose homoeostasis. Angiogenesis and innervation complete islet development, equipping islets to respond to metabolic demands. Proper regulation of this triad of processes during development is critical for establishing functional islets.

Human mesenchymal stem cells protect human islets from pro-inflammatory cytokines

Transplantation of human islets is an attractive alternative to daily insulin injections for patients with type 1 diabetes. However, the majority of islet recipients lose graft function within five years. Inflammation is a primary contributor to graft loss, and inhibiting pro-inflammatory cytokine activity can reverse inflammation mediated dysfunction of islet grafts. As mesenchymal stem cells (MSCs) possess numerous immunoregulatory properties, we hypothesized that MSCs could protect human islets from pro-inflammatory cytokines. Five hundred human islets were co-cultured with 0.5 or 1.0 × 10(6) human MSCs derived from bone marrow or pancreas for 24 hours followed by 48 hour exposure to interferon-γ, tumor necrosis factor-α and interleukin 1β. Controls include islets cultured alone (± cytokines) and with human dermal fibroblasts (± cytokines). For all conditions, glucose stimulated insulin secretion (GSIS), total islet cellular insulin content, islet β cell apoptosis, and potential cytoprotective factors secreted in the culture media were determined. Cytokine exposure disrupted human islet GSIS based on stimulation index and percentage insulin secretion. Conversely, culture with 1.0 × 10(6) bMSCs preserved GSIS from cytokine treated islets. Protective effects were not observed with fibroblasts, indicating that preservation of human islet GSIS after exposure to pro-inflammatory cytokines is MSC dependent. Islet β cell apoptosis was observed in the presence of cytokines; however, culture of bMSCs with islets prevented β cell apoptosis after cytokine treatment. Hepatocyte growth factor (HGF) as well as matrix metalloproteinases 2 and 9 were also identified as putative secreted cytoprotective factors; however, other secreted factors likely play a role in protection. This study, therefore, demonstrates that MSCs may be beneficial for islet engraftment by promoting cell survival and reduced inflammation.

Therapeutic applications of mesenchymal stromal cells: paracrine effects and potential improvements

Among the various types of cell-to-cell signaling, paracrine signaling comprises those signals that are transmitted over short distances between different cell types. In the human body, secreted growth factors and cytokines instruct, among others, proliferation, differentiation, and migration. In the hematopoietic stem cell (HSC) niche, stromal cells provide instructive cues to stem cells via paracrine signaling and one of these cell types, known to secrete a broad panel of growth factors and cytokines, is mesenchymal stromal cells (MSCs). The factors secreted by MSCs have trophic, immunomodulatory, antiapoptotic, and proangiogenic properties, and their paracrine profile varies according to their initial activation by various stimuli. MSCs are currently studied as treatment for inflammatory diseases such as graft-versus-host disease and Crohn's disease, but also as treatment for myocardial infarct and solid organ transplantation. In addition, MSCs are investigated for their use in tissue engineering applications, in which their differentiation plays an important role, but as we have recently demonstrated, their trophic factors may also be involved. Furthermore, a functional improvement of MSCs might be obtained after preconditioning or tailoring the cells themselves. Also, the way the cells are clinically administered may be specialized for specific therapeutic scenarios. In this review we will first discuss the HSC niche, in which MSCs were recently identified and are thought to play an instructive and supportive role. We will then evaluate therapeutic applications that currently try to utilize the trophic and/or immunomodulatory properties of MSCs, and we will also discuss new options to enhance their therapeutic effects.

Glial cell line-derived neurotrophic factor enhances human islet posttransplantation survival

BACKGROUND

Development of pretransplantation islet culture strategies that preserve or enhance β-cell viability would eliminate the requirement for the large numbers of islets needed to restore insulin independence in type 1 diabetes patients. We investigated whether glial cell line-derived neurotrophic factor (GDNF) could improve human islet survival and posttransplantation function in diabetic mice.

METHODS

Human islets were cultured in medium supplemented with or without GDNF (100 ng/mL) and in vitro islet survival and function assessed by analyzing β-cell apoptosis and glucose stimulated insulin release. In vivo effects of GDNF were assessed in streptozotocin-induced diabetic nude mice transplanted under the kidney capsule with 2000 islet equivalents of human islets precultured in medium supplemented with or without GDNF.

RESULTS

In vitro, human islets cultured for 2 to 10 days in medium supplemented with GDNF showed lower β-cell death, increased Akt phosphorylation, and higher glucose-induced insulin secretion than islets cultured in vehicle. Human islets precultured in medium supplemented with GDNF restored more diabetic mice to normoglycemia and for a longer period after transplantation than islets cultured in vehicle.

CONCLUSIONS

Our study shows that GDNF has beneficial effects on human islet survival and could be used to improve islet posttransplantation survival.

Current status of immunomodulatory and cellular therapies in preclinical and clinical islet transplantation

Clinical islet transplantation is a β-cell replacement strategy that represents a possible definitive intervention for patients with type 1 diabetes, offering substantial benefits in terms of lowering daily insulin requirements and reducing incidences of debilitating hypoglycemic episodes and unawareness. Despite impressive advances in this field, a limiting supply of islets, inadequate means for preventing islet rejection, and the deleterious diabetogenic and nephrotoxic side effects associated with chronic immunosuppressive therapy preclude its wide-spread applicability. Islet transplantation however allows a window of opportunity for attempting various therapeutic manipulations of islets prior to transplantation aimed at achieving superior transplant outcomes. In this paper, we will focus on the current status of various immunosuppressive and cellular therapies that promote graft function and survival in preclinical and clinical islet transplantation with special emphasis on the tolerance-inducing capacity of regulatory T cells as well as the β-cells regenerative capacity of stem cells.

Mesenchymal Stromal Cells as a Therapeutic Strategy to Support Islet Transplantation in Type 1 Diabetes Mellitus

Type 1 diabetes is an autoimmune disorder that leads to destruction of pancreatic β islet cells and is a growing global health issue. While insulin replacement remains the standard therapy for type 1 diabetes, exogenous insulin does not mimic the physiology of insulin secretion. Transplantation of pancreatic islets has the potential to cure this disease; however, there are several major limitations to widespread implementation of islet transplants. The use of mesenchymal stromal cells (MSCs) in the treatment of type 1 diabetes has been investigated as an adjunct therapy during islet graft administration to prevent initial islet loss and promote engraftment and revascularization of islets. In this review we will discuss the results of recent MSC studies in animal models of diabetes with a focus on islet transplantation and explore the potential for these findings to be extended to clinical use for the treatment of type 1 diabetes.

The stem cell niche should be a key issue for cell therapy in regenerative medicine

Recent advances in stem cell research have highlighted the role played by such cells and their environment (the stem cell niche) in tissue renewal and homeostasis. The control and regulation of stem cells and their niche are remaining challenges for cell therapy and regenerative medicine on several tissues and organs. These advances are important for both, the basic knowledge of stem cell regulation, and their practical translational applications into clinical medicine. This article is primarily concerned with the mesenchymal stem cells (MSCs) and it reviews the current aspects of their own niche. We discuss on the need for a deeper understanding of the identity of this cell type and its microenvironment in order to improve the effectiveness of any cell therapy for regenerative medicine. Ex vivo reproduction of the conditions of the natural stem cell niche, when necessary, would provide success to tissue engineering. The first challenge of regenerative medicine is to find cells able to replace and/or repair the lost function of tissues and organs by disease or aging and the trophic and immunomodulatory effects recently found for MSCs open up for new opportunities. If MSCs are pericytes, as it has been proposed, perhaps it may explain the ubiquity of these cells and their possible role in miscellaneous repairs throughout the body opening for new chances for extensive tissue repair.

New hope for type 2 diabetics: targeting insulin resistance through the immune modulation of stem cells

The prevalence of type 2 diabetes (T2D) is increasing worldwide, highlighting the need for a better understanding of the pathogenesis of the disease and the development of innovative therapeutic approaches for the prevention and cure of the condition. Mounting evidence points to the involvement of immune dysfunction in insulin resistance in T2D, suggesting that immune modulation may be a useful tool in treating the disease. Recent advances in the use of adult stem cells from human umbilical cord blood and bone marrow for immune modulation hold promise for overcoming immune dysfunction in T2D without many of the complications associated with traditional immunosuppressive therapies. This review focuses on recent progress in the use of immune modulation in T2D and discusses the potential for future therapies. New insights are provided on the use of cord blood-derived multipotent stem cells (CB-SC) in T2D.

The therapeutic role of endothelial progenitor cells in Type 1 diabetes mellitus

Pancreatic β-cells sense and adjust the blood glucose level by secretion of insulin. In Type 1 diabetes mellitus, these insulin-producing cells are destroyed, leaving the patients incapable of regulating blood glucose homeostasis. At the time of diagnosis, most patients still have 20–30% of their original β-cell mass remaining. These residual β-cells are targets for intervention therapies aimed at preventing further autoimmune destruction, in addition to increasing the number of existing β-cells. Such a therapeutic option is highly desirable since it may lead to a full recovery of newly diagnosed patients, with no need for further treatment with immunosuppressant drugs or exogenous insulin administration. In this article, we propose that endothelial progenitor cells, a cell type known to promote and support neovascularization following endothelial injury, may be used as part of a combinational stem cell therapy aimed to improve the vascularization, survival and proliferation of β-cells.

Consideration of donor age and human leukocyte antigen matching in the setting of multiple potential living kidney donors

BACKGROUND

Defining living donor (LD)-related risk factors affecting kidney transplant outcome will allow better donor selection and more educated informed consent when there is more than one potential donor. We studied risk factors in a large cohort at a single institution.

METHODS

We reviewed 1632 recipients who underwent LD kidney transplantation at the University of Minnesota between January 1, 1990, and October 1, 2009. Using Cox regression, we studied the effect of donor and recipient risk factors on patient and graft survival. We specifically examined the effect of donor age and human leukocyte antigen (HLA) matching because these are variables that may help clinical decision making when multiple potential donors exist.

RESULTS

Mean donor age was 40.6 years for all transplants; 180 (11%) donors were 55 years or older, and 24 (1.5%) donors were older than 65 years. Mean number of HLA mismatches (per transplant) was 2.9 (29.2% of recipients had one to two HLA mismatches, 39.8% had three to four HLA mismatches, and 25% had five to six HLA mismatches). Donor age more than 65 years, five to six HLA mismatches, delayed graft function, and acute rejection were independent predictors of decreased patient and graft survival. When controlling for recipient age, donor age more than 65 years remained a risk factor for worse outcome.

CONCLUSIONS

Our data suggest that advanced donor age (>65 years) and degree of HLA mismatch (≥5) are independent donor-related risk factors associated with worse outcome. When multiple potential LDs exist, it may be ideal to attempt to use a donor younger than 65 years and with less than five HLA mismatches.

Improved quantification of islet transplants by magnetic resonance imaging with Resovist

OBJECTIVES

We aimed to develop an accurate and reproducible method to quantify transplanted islets and monitor their functional status in vivo. To support this aim, we investigated the cytotoxic effect of Resovist on islet function and survival.

METHODS

The average pixel number for a single Resovist-labeled islet was measured. To determine Resovist cytotoxicity, DNA fragmentation, adenosine diphosphate-adenosine triphosphate ratio, ion channel activity, and in vivo islet function were evaluated. To quantitatively monitor the fate of islet transplant, we transplanted Resovist-labeled islets into syngeneic C57BL/6 mice for magnetic resonance imaging analysis.

RESULTS

The average pixel volume for a medium-sized islet (100-150 μm in diameter) was determined from the contrast signal void of magnetic resonance image. Toxicological analysis showed that Resovist did not affect islet at concentrations up to 40 times the labeling dose. In the quantitative analysis, the number of contrast spots did not correlated with the number of transplanted islets, whereas our newly adopted measure showed a significant correlation.

CONCLUSIONS

Islet transplant survival may be safely and accurately monitored using magnetic resonance imaging with the Resovist. We found in this study that pixel number may correlate more closely than the number of contrast spots with the number of islets transplanted.

Graft volume as the surrogate marker for nephron number affects the outcomes of living-donor kidney transplantation

Post-transplant outcome of kidney allografts depends on various factors, one of which may be the compatibility in volume between graft and recipient. However, previous studies adjusted the graft volume only for recipient's size. As the adjusted graft volume for donor's size would be substituted of nephron number more accurately, we adjusted the graft volume for both recipient's and donor's sizes. In 351 cases of living-donor kidney transplantation, we found that the adjusted graft volume for both recipient's and donor's body surface areas (BSAs) yielded larger area under the curves for the transplant outcomes than looking only at the adjusted volume for the recipient's BSA. The recipients were separated into two groups according to the low and high adjusted graft volumes. During the follow-up period (mean 55.6 months), the low-graft-volume group conferred greater risk of rejection, chronic change, glomerulonephritis, and graft loss than the high-graft-volume group (all p's < 0.05). However, the frequency of T-cell infiltration, as evaluated in protocol biopsy, was not different between the two adjusted graft volume groups. In conclusion, the graft volume as the surrogate marker for nephron number should be considered in kidney transplantation, especially in otherwise similar donor conditions.