A new scaffold containing small intestinal submucosa and mesenchymal stem cells improves pancreatic islet function and survival in vitro and in vivo

Manufacture and evaluation of nano-silver-poly-DL-lactide-co-caprolactone-small intestinal submucosa biological mesh in abdominal wall reconstruction

Background

Inguinal hernia repair is a routine surgical procedure and many methods are being applied to improve the operation. In this study, an abdominal wall defect model was established in New Zealand rabbits. The safety and efficacy of the test product was evaluated by observing the physiological state and clinical manifestations and conducting anatomical observations in the rabbits after use of the nano-silver-poly-DL-lactide-co-caprolactone-small intestinal submucosa (NS-PLCL-SIS) mesh.

Methods

A total of 18 New Zealand rabbits were randomly divided into a test group and a blank group. Routine blood and serum biochemical tests, and anatomical observations were conducted on postoperative day 30 (D30), day 60 (D60), and day 90 (D90). During the study period, all animals underwent clinical observation, and the obtained data were counted.

Results

The results showed that the NS-PLCL-SIS mesh was degraded within 90 days, and there was no abnormal reaction and no animal death during the test. There was no significant difference in the changes of animal body weight at each time point. There was no infectious inflammatory reaction in the wound at the study site, and the ocular wound healed well 7 days after the operation.

Conclusions

Under the conditions of this experiment, the NS-PLCL-SIS mesh had good performance in the repair of abdominal wall defect in New Zealand rabbits and is clinically safe for veterinarians.

Human Mesenchymal Stem Cells on Size-Sorted Gelatin Hydrogel Microparticles Show Enhanced In Vitro Wound Healing Activities

The demand for innovative therapeutic interventions to expedite wound healing, particularly in vulnerable populations such as aging and diabetic patients, has prompted the exploration of novel strategies. Mesenchymal stem cell (MSC)-based therapy emerges as a promising avenue for treating acute and chronic wounds. However, its clinical application faces persistent challenges, notably the low survivability and limited retention time of engraftment in wound environments. Addressing this, a strategy to sustain the viability and functionality of human MSCs (hMSCs) in a graft-able format has been identified as crucial for advanced wound care. Hydrogel microparticles (HMPs) emerge as promising entities in the field of wound healing, showcasing versatile capabilities in delivering both cells and bioactive molecules/drugs. In this study, gelatin HMPs (GelMPs) were synthesized via an optimized mild processing method. GelMPs with distinct diameter sizes were sorted and characterized. The growth of hMSCs on GelMPs with various sizes was evaluated. The release of wound healing promoting factors from hMSCs cultured on different GelMPs were assessed using scratch wound assays and gene expression analysis. GelMPs with a size smaller than 100 microns supported better cell growth and cell migration compared to larger sizes (100 microns or 200 microns). While encapsulation of hMSCs in hydrogels has been a common route for delivering viable hMSCs, we hypothesized that hMSCs cultured on GelMPs are more robust than those encapsulated in hydrogels. To test this hypothesis, hMSCs were cultured on GelMPs or in the cross-linked methacrylated gelatin hydrogel (GelMA). Comparative analysis of growth and wound healing effects revealed that hMSCs cultured on GelMPs exhibited higher viability and released more wound healing activities in vitro. This observation highlights the potential of GelMPs, especially those with a size smaller than 100 microns, as a promising carrier for delivering hMSCs in wound healing applications, providing valuable insights for the optimization of advanced therapeutic strategies.

In Vitro and In Vivo Improvement of Islet Quality and Transplantation Successes following Islet Treatment with Biomaterials in Diabetic Rats

Background

Loss of islet survival and function, caused by native niche disruption and oxidative stress induction during mechanical and enzymatic isolation, limits the effectiveness of islet transplantation. Reconstitution of islet microenvironment, vascularization, and decreased oxidative stress with biomaterials may improve islet quality and graft outcomes. We investigated effects of two biomaterials, platelet-rich plasma and pancreatic islets homogenate combination on islet recovery and quality by evaluating in vitro islet survival, secretory function, and oxidative stress parameters and assessing in vivo transplantation outcomes.

Methods

In vitro, islet viability and secretory function of isolated islets were assessed after 24 h and 72 h incubation with biomaterials. Also, oxidative stress markers were measured once after isolation and 24 h after incubation with biomaterials. For evaluating in vivo effects, cultured islets for 24 h were transplanted into subscapular space of diabetic rat kidney, and outcomes were analyzed by measuring serum glucose and insulin concentrations, glucose tolerance test, level of oxidative parameters, and pancreatic gene expression.

Results

Treating islets with biomaterials significantly increased their viability and secretory function, reduced MDA level, and elevate SOD and CAT activity. Decreased level of glucose and MDA improved insulin level, increased SOD activity, and also enhanced pdx1 and insulin gene expression in diabetic rats after islet transplantation.

Conclusions

Biomaterials used in the present study should be consider as beneficial materials for increasing islet transplantation outcome. These materials may hamper transplantation limitation to some extent.

Umbilical cord derived mesenchymal stem cell-GelMA microspheres for accelerated wound healing

Mesenchymal stem cells (MSCs) are an ideal seed cell for tissue engineering and stem cell transplantation. MSCs combined with biological scaffolds play an important role in promoting the repair of cutaneous wound. However, direct administration of MSCs is challenging for MSCs survival and integration into tissues. Providing MSCs with a biocompatible scaffold can improve MSCs survival, but the effect of gelatin methacrylate (GelMA) loaded MSCs from umbilical cord MSCs (UC-MSCs) in wound healing remains unknown. Here, we investigated the ability of GelMA with UC-MSCs complexes to promote migration and proliferation and the effect on wound healing in mouse models. We discovered that UC-MSCs attached to GelMA and promoted the proliferation and migration of fibroblasts. Both UC-MSCs and UC-MSCs-derived extracellular vesicles accelerated wound healing. MSC + Gelatin methacrylate microspheres (GMs) application decreased expression of transforming growth factor-β(TGF-β) and Type III collagen (Col3)in vivo, leading to new collagen deposition and angiogenesis, and accelerate wound healing and skin tissue regeneration. Taken together, these findings indicate MSC + GMs can promote wound healing by regulating wound healing-related factors in the paracrine. Therefore, our research proves that GelMA is an ideal scaffold for the top management of UC-MSCs in wound healing medical practice.

Microfluidically fabricated fibers containing pancreatic islets and mesenchymal stromal cells improve longevity and sustained normoglycemia in diabetic rats

Type 1 diabetes mellitus is an autoimmune disease characterized by the loss of pancreatic isletβcells. Insulin injections and pancreas transplants are currently available therapies. The former requires daily insulin injections, while the latter is constrained by donor organ availability. Islet transplantation is a promising alternative treatment for type 1 diabetes mellitus that may overcome the limitations of previous techniques. Two challenges, however, must be addressed: limited cell retention as a result of the immune response and limited function of the transplanted cells that survive. To address these problems, we developed a microfluidic technology for a one-step generation of islet-laden fibers to protect them from the immune response. This approach enables continuous generation of microfibers with a diameter suitable for islet encapsulation (275µm). We, then, transplanted islet-laden fibers into diabetic Wistar rats. While islet-laden fibers alone were unable to restore normoglycemia in diabetic rats, adding mesenchymal stromal cells (MSCs) restored normoglycemia for an extended time. It increased the animals' lifespan by up to 75 d. Additionally, it improved the glucose-stimulated response of islets to the point where there was no significant difference between the treatment group and the healthy animals. Additionally, the presence of MSCs suppressed the immune response, as seen by decreased levels of pro-inflammatory cytokines such as tumor necrosis factor-α. Taken together, these fibers including islet and MSCs provide a versatile platform for concurrently improving cell preservation and functioning followingin vivotransplantation.

Cotransplant With Pancreatic Islet Homogenate Improved Survival and Long-Term Efficacy of Islet Transplant in Streptozotocin-Diabetic Rats

OBJECTIVES

Pancreatic islet transplant is suggested as a promising treatment option in diabetes, but the number of viable and functional islets and the long-term efficacy of transplanted islets have not been satisfactory. Islet isolation leads to destruction of the extracellular matrix and loss of trophic support of islets, which reduces their survival and function. Reconstruction of islet microenvironment with biomaterials may preserve islet survival and graft efficacy. Accordingly, we investigated the effects of pancreatic islet homogenate on islet quality and graft outcomes in diabetic rats.

MATERIALS AND METHODS

Islets were isolated from the pancreas of Sprague Dawley rats and were cultured with or without pancreatic islet homogenate. Before transplant, viability, insulin content, and insulin released from cultured islets were assessed. Islets were then transplanted into subcapsular space of diabetic rat kidney. Transplant outcomes were evaluated by plasma glucose and insulin levels, glucose tolerance tests, and stress oxidative markers.

RESULTS

Viability and insulin release in the pancreatic islet homogenate-treated islets were significantly higher than that in the control islets. After transplant of islets, recipient rats with pancreatic islet homogenate showed significant decreases in blood glucose and malondialdehyde levels and increases in superoxide dismutase activity and plasma insulin levels.

CONCLUSIONS

Islet treatment with pancreatic islet homogenate could improve islet survival and transplant function and outcomes. Oxidative stress reduction might be a secondary beneficial effect of improved quality of treated islets.

Tissue Models for Neisseria gonorrhoeae Research—From 2D to 3D

Neisseria gonorrhoeae is a human-specific pathogen that causes gonorrhea, the second most common sexually transmitted infection worldwide. Disease progression, drug discovery, and basic host-pathogen interactions are studied using different approaches, which rely on models ranging from 2D cell culture to complex 3D tissues and animals. In this review, we discuss the models used in N. gonorrhoeae research. We address both in vivo (animal) and in vitro cell culture models, discussing the pros and cons of each and outlining the recent advancements in the field of three-dimensional tissue models. From simple 2D monoculture to complex advanced 3D tissue models, we provide an overview of the relevant methodology and its application. Finally, we discuss future directions in the exciting field of 3D tissue models and how they can be applied for studying the interaction of N. gonorrhoeae with host cells under conditions closely resembling those found at the native sites of infection.

Decellularized Whole-Organ Pre-vascularization: A Novel Approach for Organogenesis

Introduction: Whole-organ decellularization is an attractive approach for three-dimensional (3D) organ engineering. However, progress with this approach is hindered by intra-vascular blood coagulation that occurs after in vivo implantation of the re-cellularized scaffold, resulting in a short-term graft survival. In this study, we explored an alternative approach for 3D organ engineering through an axial pre-vascularization approach and examined its suitability for pancreatic islet transplantation. Methods: Whole livers from male Lewis rats were decellularized through sequential arterial perfusion of detergents. The decellularized liver scaffold was implanted into Lewis rats, and an arteriovenous bundle was passed through the scaffold. At the time of implantation, fresh bone marrow preparation (BM; n = 3), adipose-derived stem cells (ADSCs; n = 4), or HBSS (n = 4) was injected into the scaffold through the portal vein. After 5 weeks, around 2,600 islet equivalents (IEQs) were injected through the portal vein of the scaffold. The recipient rats were rendered diabetic by the injection of 65 mg/kg STZ intravenously 1 week before islet transplantation and were followed up after transplantation by measuring the blood glucose and body weight for 30 days. Intravenous glucose tolerance test was performed in the cured animals, and samples were collected for immunohistochemical (IHC) analyses. Micro-computed tomography (CT) images were obtained from one rat in each group for representation. Results: Two rats in the BM group and one in the ADSC group showed normalization of blood glucose levels, while one rat from each group showed partial correction of blood glucose levels. In contrast, no rats were cured in the HBSS group. Micro-CT showed evidence of sprouting from the arteriovenous bundle inside the scaffold. IHC analyses showed insulin-positive cells in all three groups. The number of von-Willebrand factor-positive cells in the islet region was higher in the BM and ADSC groups than in the HBSS group. The number of 5-bromo-2'-deoxyuridine-positive cells was significantly lower in the BM group than in the other two groups. Conclusions: Despite the limited numbers, the study showed the promising potential of the pre-vascularized whole-organ scaffold as a novel approach for islet transplantation. Both BM- and ADSCs-seeded scaffolds were superior to the acellular scaffold.

Effects of hypoxia on Achilles tendon repair using adipose tissue-derived mesenchymal stem cells seeded small intestinal submucosa

BACKGROUND

The study was performed to evaluate the feasibility of utilizing small intestinal submucosa (SIS) scaffolds seeded with adipose-derived mesenchymal stem cells (ADMSCs) for engineered tendon repairing rat Achilles tendon defects and to compare the effects of preconditioning treatments (hypoxic vs. normoxic) on the tendon healing.

METHODS

Fifty SD rats were randomized into five groups. Group A received sham operation (blank control). In other groups, the Achilles tendon was resected and filled with the original tendon (Group B, autograft), cell-free SIS (Group C), or SIS seeded with ADMSCs preconditioned under normoxic conditions (Group D) or hypoxic conditions (Group E). Samples were collected 4 weeks after operation and analyzed by histology, immunohistochemistry, and tensile testing.

RESULTS

Histologically, compared with Groups C and D, Group E showed a significant improvement in extracellular matrix production and a higher compactness of collagen fibers. Group E also exhibited a significantly higher peak tensile load than Groups D and C. Additionally, Group D had a significantly higher peak load than Group C. Immunohistochemically, Group E exhibited a significantly higher percentage of MKX + cells than Group D. The proportion of ADMSCs simultaneously positive for both MKX and CM-Dil observed from Group E was also greater than that in Group D.

CONCLUSIONS

In this animal model, the engineered tendon grafts created by seeding ADMSCs on SIS were superior to cell-free SIS. The hypoxic precondition further improved the expression of tendon-related genes in the seeded cells and increased the rupture load after grafting in the Achilles tendon defects.

Modulating the foreign body response of implants for diabetes treatment

Diabetes Mellitus is a group of diseases characterized by high blood glucose levels due to patients' inability to produce sufficient insulin. Current interventions often require implants that can detect and correct high blood glucose levels with minimal patient intervention. However, these implantable technologies have not reached their full potential in vivo due to the foreign body response and subsequent development of fibrosis. Therefore, for long-term function of implants, modulating the initial immune response is crucial in preventing the activation and progression of the immune cascade. This review discusses the different molecular mechanisms and cellular interactions involved in the activation and progression of foreign body response (FBR) and fibrosis, specifically for implants used in diabetes. We also highlight the various strategies and techniques that have been used for immunomodulation and prevention of fibrosis. We investigate how these general strategies have been applied to implants used for the treatment of diabetes, offering insights on how these devices can be further modified to circumvent FBR and fibrosis.

Bone marrow-derived mesenchymal stem cells improve rat islet graft revascularization by upregulating ISL1

Revascularization of the islet transplant is a crucial step that defines the success rate of patient recovery. Bone marrow-derived mesenchymal stem cells (BMSCs) have been reported to promote revascularization; however, the underlying cellular mechanism remains unclear. Moreover, our liquid chromatography-tandem mass spectrometry results showed that BMSCs could promote the expression of insulin gene enhancer binding protein-1 (ISL1) in islets. ISL1 is involved in islets proliferation and plays a potential regulatory role in the revascularization of islets. This study identifies the ISL1 protein as a potential modulator in BMSCs-mediated revascularization of islet grafts. We demonstrated that the survival rate and insulin secretion of islets were increased in the presence of BMSCs, indicating that BMSCs promote islet revascularization in a coculture system and rat diabetes model. Interestingly, we also observed that the presence of BMSCs led to an increase in ISL1 and vascular endothelial growth factor A (VEGFA) expression in both islets and the INS-1 rat insulinoma cell line. In silico protein structure modeling indicated that ISL1 is a transcription factor that has four binding sites with VEGFA mRNA. Further results showed that overexpression of ISL1 increased both the abundance of VEGFA transcripts and protein accumulation, while inhibition of ISL1 decreased the abundance of VEGFA. Using a ChIP-qPCR assay, we demonstrated that direct molecular interactions between ISL1 and VEGFA occur in INS-1 cells. Together, these findings reveal that BMSCs promote the expression of ISL1 in islets and lead to an increase in VEGFA in islet grafts. Hence, ISL1 is a potential target to induce early revascularization in islet transplantation.

Nano-biological mesh constructed by astragaloside-IV-induced bone marrow mesenchymal stem cells on PLGA-NPs-SIS can be used for abdominal wall reconstruction

A combination of stem cells, scaffold materials, nanoparticles (NPs), and physiological factors can be used to engineer a tissue that can replace or improve the function of the damaged tissue. This study was designed to assess whether astragaloside (aS)-IV-activated rat bonemarrow-derived mesenchymal stem cells (BMSCs), seeded on a nano-biological mesh composed of small intestinal submucosa (SIS) modified with poly (D,L-lactide-co-glycolide) NPs (PLGA-NPs-SIS), can promote cell engraftment, proliferation, and mesh incorporation into the tissue upon implantation. aS-IV-induced BMSCs cultured with PLGA-NPs-SIS showed enhanced viability and proliferation as well as reduced apoptosis. Vascular endothelial growth factor, type I and II collagen, and monocyte chemoattractant protein-1 were upregulated, whereas matrix metalloproteinase and interleukin-6 were downregulated in these BMSCs. Pre-seeded BMSCs induced with aS-IV engrafted in a rat abdominal wall defect model showed migratory and proliferative capacities while enhancing vascularity at the musculofascial/graft interface. These findings imply that the nano-biological mesh composed of aS-IV-induced BMSCs seeded on PLGA-NPs-SIS can be used for abdominal wall reconstruction.

Considerations for an Alternative Site of Islet Cell Transplantation

Islet cell transplantation has been limited most by poor graft survival. Optimizing the site of transplantation could improve clinical outcomes by minimizing required donor cells, increasing graft integration, and simplifying the transplantation and monitoring process. In this article, we review the history and significant human and animal data for clinically relevant sites, including the liver, spleen, and kidney subcapsule, and identify promising new sites for further research. While the liver was the first studied site and has been used the most in clinical practice, the majority of transplanted islets become necrotic. We review the potential causes for graft death, including the instant blood-mediated inflammatory reaction, exposure to immunosuppressive agents, and low oxygen tension. Significant research exists on alternative sites for islet cell transplantation, suggesting a promising future for patients undergoing pancreatectomy.

The emerging field of pancreatic tissue engineering: A systematic review and evidence map of scaffold materials and scaffolding techniques for insulin-secreting cells

A bioartificial endocrine pancreas is proposed as a future alternative to current treatment options. Patients with insulin-secretion deficiency might benefit. This is the first systematic review that provides an overview of scaffold materials and techniques for insulin-secreting cells or cells to be differentiated into insulin-secreting cells. An electronic literature survey was conducted in PubMed/MEDLINE and Web of Science, limited to the past 10 years. A total of 197 articles investigating 60 different materials met the inclusion criteria. The extracted data on materials, cell types, study design, and transplantation sites were plotted into two evidence gap maps. Integral parts of the tissue engineering network such as fabrication technique, extracellular matrix, vascularization, immunoprotection, suitable transplantation sites, and the use of stem cells are highlighted. This systematic review provides an evidence-based structure for future studies. Accumulating evidence shows that scaffold-based tissue engineering can enhance the viability and function or differentiation of insulin-secreting cells both in vitro and in vivo.

Evaluation of the bioactivity about anti-sca-1/basic fibroblast growth factor-urinary bladder matrix scaffold for pelvic reconstruction

Introduction and hypothesis: Pelvic support structure injury is the major cause of pelvic organ prolapse. At present, polypropylene-based filler material has been suggested as a common method to treat pelvic organ prolapse. However, it cannot functionally rehabilitate the pelvic support structure. In addition to its poor long-term efficiency, the urinary bladder matrix was the most suitable biological scaffold material for pelvic floor repair. Here, we hypothesize that anti-sca-1 monoclonal antibody and basic fibroblast growth factor were cross-linked to urinary bladder matrix to construct a two-factor bioscaffold for pelvic reconstruction.

METHODS

Through a bispecific cross-linking reagent, sulfosuccinimidyl 4-[N-maleimidomethyl] cyclohexane-1-carboxylate (sulfo-smcc) immobilized anti-sca-1 and basic fibroblast growth factor to urinary bladder matrix. Then scanning electron microscope and plate reader were used to detect whether the anti-sca-1/basic fibroblast growth factor-urinary bladder matrix scaffold was built successfully. After that, the capacity of enriching sca-1 positive cells was measured both in vitro and in vivo. In addition, we evaluated the differentiation capacity and biocompatibility of the scaffold. Finally, western blotting was used to detect the level of fibulin-5 protein.

RESULTS

The scanning electron microscope and plate reader revealed that the double-factor biological scaffold was built successfully. The scaffold could significantly enrich a large number of sca-1 positive cells both in vitro and in vivo, and obviously accelerate cells and differentiate functional tissue with good biocompatibility. Moreover, the western blotting showed that the scaffold could improve the expression of fibulin-5 protein.

CONCLUSION

The anti-sca-1/basic fibroblast growth factor-urinary bladder matrix scaffold revealed good biological properties and might serve as an ideal scaffold for pelvic reconstruction.

Tissue and organ decellularization in regenerative medicine

The advancement and improvement in decellularization methods can be attributed to the increasing demand for tissues and organs for transplantation. Decellularized tissues and organs, which are free of cells and genetic materials while retaining the complex ultrastructure of the extracellular matrix (ECM), can serve as scaffolds to subsequently embed cells for transplantation. They have the potential to mimic the native physiology of the targeted anatomic site. ECM from different tissues and organs harvested from various sources have been applied. Many techniques are currently involved in the decellularization process, which come along with their own advantages and disadvantages. This review focuses on recent developments in decellularization methods, the importance and nature of detergents used for decellularization, as well as on the role of the ECM either as merely a physical support or as a scaffold in retaining and providing cues for cell survival, differentiation and homeostasis. In addition, application, status, and perspectives on commercialization of bioproducts derived from decellularized tissues and organs are addressed. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1494-1505, 2018.

Decellularized Matrices As Cell-Instructive Scaffolds to Guide Tissue-Specific Regeneration

Decellularized scaffolds are promising clinically translational biomaterials that can be applied to direct cell responses and promote tissue regeneration. Bioscaffolds derived from the extracellular matrix (ECM) of decellularized tissues can naturally mimic the complex extracellular microenvironment through the retention of compositional, biomechanical, and structural properties specific to the native ECM. Increasingly, studies have investigated the use of ECM-derived scaffolds as instructive substrates to recapitulate properties of the stem cell niche and guide cell proliferation, paracrine factor production, and differentiation in a tissue-specific manner. Here, we review the application of decellularized tissue scaffolds as instructive matrices for stem or progenitor cells, with a focus on the mechanisms through which ECM-derived scaffolds can mediate cell behavior to promote tissue-specific regeneration. We conclude that although additional preclinical studies are required, ECM-derived scaffolds are a promising platform to guide cell behavior and may have widespread clinical applications in the field of regenerative medicine.

Transplantation sites for human and murine islets

AIMS/HYPOTHESIS

Beta cell replacement is a potential cure for type 1 diabetes. In humans, islet transplants are currently infused into the liver via the portal vein, although this site has disadvantages. Here, we investigated alternative transplantation sites for human and murine islets in recipient mice, comparing the portal vein with quadriceps muscle and kidney, liver and spleen capsules.

METHODS

Murine islets were isolated from C57BL6/J mice and transplanted into syngeneic recipients. Human islets were isolated and transplanted into either severe combined immunodeficiency (SCID) or recombination-activating gene 1 (RAG-1) immunodeficient recipient mice. All recipient mice were 8-12 weeks of age and had been rendered diabetic (defined as blood glucose concentrations ≥20 mmol/l on two consecutive days before transplantation) by alloxan tetrahydrate treatment. Islets were transplanted into five different sites (portal vein, quadriceps muscle, kidney, liver and spleen capsules). Blood glucose concentrations were monitored twice weekly until mice were killed. Dose-response studies were also performed to determine the minimum number of islets required to cure diabetes ('cure' is defined for this study as random fed blood glucose of <15 mmol/l).

RESULTS

For transplantation of murine islets into the different sites, the kidney yielded 100% success, followed by muscle (70%), portal vein (60%), spleen capsule (29%) and liver capsule (0%). For human islets, transplantation into the kidney cured diabetes in 75-80% of recipient mice. Transplantation into muscle and portal vein had intermediate success (both 29% at 2000 islet equivalents), while transplantation into liver and spleen capsule failed (0%). With increased islet mass, success rates for muscle grafts improved to 52-56%.

CONCLUSIONS/INTERPRETATION

For both human and murine islets, equivalent or superior glucose lowering results were obtained for transplantation into skeletal muscle, compared with the portal vein. Unfortunately, kidney grafts are not feasible in human recipients. Skeletal muscle offers easier access and greater potential for protocol biopsies. This study suggests that human trials of muscle as a transplant site may be warranted.

Multipotent mesenchymal stromal cells enhance insulin secretion from human islets via N-cadherin interaction and prolong function of transplanted encapsulated islets in mice

BACKGROUND

Multipotent mesenchymal stromal cells (MSC) enhance viability and function of islets of Langerhans. We aimed to examine the interactions between human MSC and human islets of Langerhans that influence the function of islets.

METHODS

Human MSC and human islets (or pseudoislets, obtained after digestion and reaggregation of islet cells) were cocultured with or without cellular contact and glucose-stimulated insulin secretion assays were performed to assess cell function. The expression of several adhesion molecules, notably ICAM-1 and N-cadherin on islets and MSC, was investigated by qPCR. The role of N-cadherin was analyzed by adding an anti-N-cadherin antibody in islets cultured with or without MSC for 24 h followed by insulin measurements in static incubation assays. Islets and MSC were coencapsulated in new hydrogel microspheres composed of calcium alginate and covalently crosslinked polyethylene glycol. Encapsulated cells were transplanted intraperitoneally in streptozotocin-induced diabetic mice and glycemia was monitored. Islet function was evaluated by the intraperitoneal glucose tolerance test.

RESULTS

In vitro, free islets and pseudoislets cocultured in contact with MSC showed a significantly increased insulin secretion when compared to islets or pseudoislets cultured alone or cocultured without cell-to-cell contact with MSC (p < 0.05). The expression of ICAM-1 and N-cadherin was present on islets and MSC. Blocking N-cadherin prevented the enhanced insulin secretion by islets cultured in contact with MSC whereas it did not affect insulin secretion by islets cultured alone. Upon transplantation in diabetic mice, islets microencapsulated together with MSC showed significantly prolonged normoglycemia when compared with islets alone (median 69 and 39 days, respectively, p < 0.01). The intraperitoneal glucose tolerance test revealed an improved glycemic response in mice treated with islets microencapsulated together with MSC compared to mice transplanted with islets alone (p < 0.001).

CONCLUSIONS

MSC improve survival and function of islets of Langerhans by cell-to-cell contact mediated by the adhesion molecule N-cadherin.