Microencapsulated Islet Transplantation Research Articles

Microencapsulated islet transplantation alleviates podocyte injury in diabetic nephropathy via inhibiting Notch-1 signaling

ObjectivePodocyte injury has a critical role in the pathogenesis of diabetic nephropathy (DN). Microencapsulated islet transplantation (MIT) is identified as an effective method for improving the clinical condition of DN. This study aimed to explore the role and mechanism of MIT in alleviating podocyte injury in DN. MethodsA mouse model of DN was constructed using streptozotocin (STZ). Mice were divided into 3 groups: the untreated diabetic nephropathy group (DN group), the microencapsulated islet transplantation-treated group (MIT group) and the control group. The mice were raised for 6 weeks posterior to islet transplantation to identify the role of MIT. Renal function and structure of glomerular filtration barrier were assessed by urine analysis, histopathological examination, and transmission electron microscopy. The expression levels of several proteins including Caspase-3, Bcl2/Bax, β-galactosidase, Ki-67, synaptopodin, WT-1, Jagged-1, Notch-1, and Hes-1 in renal tissues were identified via immunohistochemistry (IHC), immunofluorescence (IF), and western blotting techniques. ResultsCompared with the DN group, the MIT group presented decreased levels of blood glucose, urinary albumin/creatinine, urea nitrogen, and serum creatinine while their body weight gradually increased. Glomerular injury in the MIT group was significantly better than that in the DN group. The MIT group indicated significantly decreased expression of Caspase-3, β-galactosidase, Bax/Bcl-2, and Ki-67 when compared with DN group, while the proportion of synaptopodin- and WT-1-positive cells was significantly increased (P < 0.05). The protein expression of Jagged-1, Notch-1, and Hes-1 in the glomerulus of the MIT group was significantly lower than that in the DN group (P < 0.05). ConclusionMIT alleviates podocyte injury induced by DN by inhibiting Notch-1 signaling. The identification of signaling pathways influencing podocyte restoration can help evaluate personalized medicine efficacy for patients treated with islet transplantation.

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.

Magnetic Resonance Imaging of Alginate Beads Containing Pancreatic Beta Cells and Paramagnetic Nanoparticles

Microencapsulation is being investigated as a means to avoid rejection of transplanted pancreatic islets. Monitoring bead distribution and stability in vivo is an important step toward improving microencapsulated islet transplantation strategies. Islet co-encapsulation with gadolinium-labeled mesoporous silica nanoparticles (Gd-MSNs) could allow bead visualization while immobilizing and limiting the potential internalization of the contrast agent. The porous nature of the MSNs could also be used to locally release anti-inflammatory, angiogenic, or anti-apoptotic factors. Mouse insulinoma 6 (MIN6) beta cells were co-encapsulated with Gd-MSNs in alginate beads produced by emulsification and internal gelation. Gd-MSN alginate beads appeared brighter in T1-weighted imaging sequences (detection threshold of 0.016 mM Gd; relaxometric ratio r2/r1 = 1.45) than beads without Gd-MSNs. No leaching of Gd3+ from the hydrogels was detected over the course of 3 months. MIN6 cells co-encapsulated with Gd-MSNs were viable without significant differences in cell growth rate compared to encapsulated controls without Gd-MSNs. This study paves the way for microencapsulated islet tracking via MRI using co-encapsulated paramagnetic nanomaterials.

Islet Microencapsulation: Strategies and Clinical Status in Diabetes.

Type 1 diabetes mellitus (T1DM) is an autoimmune disease that results from the destruction of insulin-producing pancreatic β cells in the islets of Langerhans. Islet cell transplantation has become a successful therapy for specific patients with T1DM with hypoglycemic unawareness. The reversal of T1DM by islet transplantation is now performed at many major medical facilities throughout the world. However, many challenges must still be overcome in order to achieve continuous, long-term successful transplant outcomes. Two major obstacles to this therapy are a lack of islet cells for transplantation and the need for life-long immunosuppressive treatment. Microencapsulation is seen as a technology that can overcome both these limitations of islet cell transplantation. This review depicts the present state of microencapsulated islet transplantation. Microencapsulation can play a significant role in overcoming the need for immunosuppression and lack of donor islet cells. This review focuses on microencapsulation and the clinical status of the technology in combating T1DM.

Combined Microencapsulated Islet Transplantation and Revascularization of Aortorenal Bypass in a Diabetic Nephropathy Rat Model.

Objective. Revascularization of aortorenal bypass is a preferred technique for renal artery stenosis (RAS) in diabetic nephropathy (DN) patients. Restenosis of graft vessels also should be considered in patients lacking good control of blood glucose. In this study, we explored a combined strategy to prevent the recurrence of RAS in the DN rat model. Methods. A model of DN was established by intraperitoneal injection of streptozotocin. Rats were divided into 4 groups: SR group, MIT group, Com group, and the untreated group. The levels of blood glucose and urine protein were measured, and changes in renal pathology were observed. The expression of monocyte chemoattractant protein-1 (MCP-1) in graft vessels was assessed by immunohistochemical staining. Histopathological staining was performed to assess the pathological changes of glomeruli and tubules. Results. The levels of urine protein and the expression of MCP-1 in graft vessels were decreased after islet transplantation. The injury of glomerular basement membrane and podocytes was significantly ameliorated. Conclusions. The combined strategy of revascularization and microencapsulated islet transplantation had multiple protective effects on diabetic nephropathy, including preventing atherosclerosis in the graft vessels and alleviating injury to the glomerular filtration barrier. This combined strategy may be helpful for DN patients with RAS.

Transplantation of Pancreatic Islets Immobilized in Alginate-Based Microcapsules: From Animal Studies to Clinical Trials

Microencapsulated islet transplantation has been investigated for over three decades in an attempt to eliminate the hostile effects of long-term immunosuppressant usage and improve islet engraftment in patients suffering from Type 1 Diabetes Mellitus (T1DM). Once feasibility of the islet encapsulation process was confirmed, the biocompatibility and survival of microencapsulated islets were directly tested in different animal models. Such animal models include: immunodeficient rodents (nude and NOD-SCID mice), immunocompetent rodents, autoimmune diabetic rodents (NOD mice and BB rats), and large animals (dogs, pigs, and non-human primates). In general, the majority of microcapsules tested in vivo was found to be biocompatible with the host and retained their function. This was especially apparent in small animal models. However, greater variability and reduced biocompatibility was observed in larger animal models. Since the first attempts to introduce this methodology to the clinical field, different devices and several implementation techniques have been proposed in order to support this technology. To date islet microencapsulation in the absence of immunosuppressive medication has not yet successfully reached the clinical setting. The purpose of this review is to summarize the transplant outcomes of different microencapsulation systems and transplant models, to reveal the major obstacles that each has presented, and to propose better avenues of investigation into future studies, which may lead to a successful clinical application for this technology.

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.

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. 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. 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. 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.

A Recommended Laparoscopic Procedure for Implantation of Microcapsules in the Peritoneal Cavity of Non-Human Primates

The anatomical spatial distribution of microencapsulated islets transplanted into the peritoneal cavity of large animals remains a relatively unexplored area of study. In this study, we developed a new implantation approach using laparoscopy in order to avoid microcapsule amalgamation. This approach constitutes a clinically relevant method, which can be used to evaluate the distribution and in vivo biocompatibility of various types of transplanted microcapsules in the future. Two healthy baboons were implanted intraperitoneally with microencapsulated islets through mini-laparotomy and observed at 76 d after implantation. Nine baboons underwent laparoscopic implantation of approximately 80,000 empty microcapsules. Microcapsule distribution was observed by laparoscopic camera during and after implantation at 1, 2, and 4 wk. At each time point, microcapsules were retrieved and evaluated with brightfield microscopy and histologic analysis. Mini-laparotomic implantation resulted in microcapusle aggregation in both baboons. In contrast, laparoscopic implantation resulted in even distribution of microcapsules throughout the peritoneum without sedimentation to the Douglas space in all animals. In eight out of nine animals, retrieved microcapsules were evenly distributed in the peritoneal cavity and presented with no pericapsular overgrowth and easily washed out during laparoscopic procedure. The one exception was attributed to microcapsule contamination with blood from the abdominal wall following trocar insertion. Laparoscopic implantation of microcapsules in non-human primates can be successfully performed and prevents microcapsule aggregation. Given the current widespread clinical application of laparoscopy, we propose that this presented laparoscopy technique could be applied in future clinical trials of microencapsulated islet transplantation.

Evaluation of the effect of microencapsulation and immuno-modulation on islet immunogenicity in vitro.

The complexity of the transplantation model in microencapsulated islet transplantation suggests the use of an in vitro model for the analysis of the effect of encapsulation and graft pretreatment on islet immunogenicity. In this study, the mixed lymphocyte islet culture is applied to islets encapsulated in barium alginate beads, showing a significant reduction of the cellular response compared with non-encapsulated islets. Moreover, the effect of low-temperature culture as the immuno modulatory principle is shown on encapsulated and non-encapsulated islets. The data suggest that encapsulation reduces but not totally impedes the immunological interaction between the encapsulated tissue and the surrounding immune cells and that the stimulatory potency of the encapsulated islet may be modified by immuno-altering pretreatment.

Islet alpha cell number is maintained in microencapsulated islet transplantation

Islet transplantation can reverse hyperglycaemia in Type 1 diabetes patients. One problem in islet transplantation is a loss of beta cell mass as well as blunted glucagon responses from the grafted islets. It has been suggested that alpha cell loss is associated with close contact of the alpha cells with the implantation organ. In the present study we made use of microencapsulation, where transplanted islets are not in direct contact with the host implantation site. After transplantation, the number of glucagon cells stained per microencapsulated islet section was increased whereas the number of insulin cells stained was decreased. DNA content of the islets was reduced, as was insulin content, whereas glucagon content was unchanged. This indicates that cell number in transplanted microencapsulated islets diminishes, which can be accounted for by loss of beta cells. However, in contrast to previous studies using non-encapsulated islets, alpha cell number seems to be maintained.

Biodritin Microencapsulated Human Islets of Langerhans and Their Potential for Type 1 Diabetes Mellitus Therapy

Background Microencapsulation of pancreatic islets with polymeric compounds constitutes an attractive alternative therapy for type 1 diabetes mellitus. The major limiting factor is the availability of a biocompatible and mechanically stable polymer. We investigated the potential of Biodritin, a novel polymer constituted of alginate and chondroitin sulfate, for islet microencapsulation. Methods Biodritin microcapsules were obtained using an air jet droplet generator and gelated with barium or calcium chloride. Microencapsulated rat insulinoma RINm5F cells were tested for viability using the [3-(4,5-dimetyl-thiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide] [MTT] colorimetric assay. Microencapsulated rat pancreatic islets were coincubated with macrophages derived from mouse peritoneal liquid to assess the immunomodulatory potential of the microcapsules, using quantitative real time-PCR (qPCR). Biodritin biocompatibility was demonstrated by subcutaneous injection of empty microcapsules into immunocompetent Wistar rats. Insulin secretion by microencapsulated human pancreatic islets was evaluated using an electrochemoluminescent assay. Microencapsulated human islets transplanted into chemically induced diabetic mice were monitored for reversal of hyperglycemia. Results The metabolic activity of microencapsulated RINm5F cells persisted for at least 15 days. Interleukin-1β expression by macrophages was observed during coculture with islets microencapsulated with Biodritin-CaCl 2, but not with Biodritin-BaCl 2. No statistical difference in glucose-stimulated insulin secretion was observed between nonencapsulated and microencapsulated islets. Upon microencapsulated islet transplantation, the blood glucose level of diabetic mice normalized; they remained euglycemic for at least 60 days, displaying normal oral glucose tolerance tests. Conclusion This study demonstrated that Biodritin can be used for islet microencapsulation and reversal of diabetes; however, further investigations are required to assess its potential for long-term transplantation.

Glucose-Insulin Kinetics of the Extravascular Bioartificial Pancreas A Study Using Microencapsulated Rat Islets

The success of the extravascular bioartificial pancreas (BAP) is contingent on the rapid transfer of the glycemic signal across both an extravascular compartment and a semipermeable membrane and of insulin from the BAP to the recipient. To examine the possibility of microencapsulated islets such as the BAP to achieve satisfactory in vivo glucose-insulin kinetics, islets were isolated from Lewis rats, encapsulated in poly-L-lysine-alginate membranes, and isogenically transplanted into the peritoneal cavity of 14 streptozotocin induced diabetic rats. Fasting blood glucose (BG) was measured and intravenous glucose tolerance was tested at 8-10 weeks and compared with three control groups: 1) normal Lewis rats (n = 6); 2) untreated diabetic rats (n = 5); and 3) diabetic rats that received intraperitoneal implants of empty capsules (n = 4). Ten animals that received microencapsulated islets (5,271 +/- 431) promptly became normoglycemic, with a mean BG of 128 +/- 17 ng/dl 3 days after transplantation and maintained this level > 100 days. Intravenous glucose tolerance K-value for the group was 3.84 +/- 0.32 compared with 3.96 +/- 0.39 (p = 0.83) for the normal control group, and 0.60 +/- 0.12 (p < 0.01) and 0.40 +/- 0.15 (p < 0.01) for the diabetic control groups with and without empty capsules. The authors conclude from these results that, given sufficient beta-cell mass, a BAP without any vascular access can respond appropriately to an increase in blood glucose concentration, without overshoot hypoglycemia and within a lag lapse compatible with normal physiologic insulin delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Preliminary report on microencapsulated islet transplantation in experimental diabetes mellitus in China

Pancreatic islets were encapsulated with sodium alginate-polylysine after procurement by collagenase digestion and Ficoll density-gradient-dispersion. The encapsulated islets were intact and during the first week of culture produced insulin 63 +/- 42 microU/d vs 69 +/- 42 microU/d by noncapsulated islets. Seven streptozotocin-induced diabetic rats each received 4.0-4.5 x 10(3) microencapsulated islets intraperitoneally. After transplantation, blood glucose dropped from 350 +/- 29 mg/dl to 142 +/- 12 mg/dl. To date, normoglycemia has been maintained for 222 days. Control animals either died or developed cataracts.