Islet Transplantation Imaging in vivo

Mouse models and human islet transplantation sites for intravital imaging

Human islet transplantations into rodent models are an essential tool to aid in the development and testing of islet and cellular-based therapies for diabetes prevention and treatment. Through the ability to evaluate human islets in an in vivo setting, these studies allow for experimental approaches to answer questions surrounding normal and disease pathophysiology that cannot be answered using other in vitro and in vivo techniques alone. Intravital microscopy enables imaging of tissues in living organisms with dynamic temporal resolution and can be employed to measure biological processes in transplanted human islets revealing how experimental variables can influence engraftment, and transplant survival and function. A key consideration in experimental design for transplant imaging is the surgical placement site, which is guided by the presence of vasculature to aid in functional engraftment of the islets and promote their survival. Here, we review transplantation sites and mouse models used to study beta cell biology in vivo using intravital microscopy and we highlight fundamental observations made possible using this methodology.

Nanotechnology in Kidney and Islet Transplantation: An Ongoing, Promising Field

Organ transplantation has evolved rapidly in recent years as a reliable option for patients with end-stage organ failure. However, organ shortage, surgical risks, acute and chronic rejection reactions and long-term immunosuppressive drug applications and their inevitable side effects remain extremely challenging problems. The application of nanotechnology in medicine has proven highly successful and has unique advantages for diagnosing and treating diseases compared to conventional methods. The combination of nanotechnology and transplantation brings a new direction of thinking to transplantation medicine. In this article, we provide an overview of the application and progress of nanotechnology in kidney and islet transplantation, including nanotechnology for renal pre-transplantation preservation, artificial biological islets, organ imaging and drug delivery.

Identification and Validation of a New Peptide Targeting Pancreatic Beta Cells

Noninvasive targeted visualization of pancreatic beta cells or islets is becoming the focus of molecular imaging application in diabetes and islet transplantation studies. In this study, we aimed to produce the beta-cell-targeted peptide for molecular imaging of islet. We used phage display libraries to screen a beta-cell-targeted peptide, LNTPLKS, which was tagged with fluorescein isothiocyanate (FITC). This peptide was validated for targeting beta-cell with in vitro and in vivo studies. Immunocytochemistry (ICC) and fluorescence-activated cell sorting (FACS) analysis were used to validate the target specificity of the peptide. FITC-LNTPLKS displayed much higher fluorescence in beta cells vs. control cells in ICC. This discrimination was consistently observed using primary rodent islet. FACS analysis showed right shift of peak point in beta cells compared to control cells. The specific bind to in situ islet was verified by in vitro experiments using rodent and human pancreatic slices. The peptide also showed high affinity of islet grafts under the renal capsule. In the insulinoma animal model, we could find FITC-LNTPLKS accumulated specifically to the tumor, thus indicating a potential clinical application of molecular imaging of insulinoma. In conclusion, LNTPLKS showed a specific probe for beta-cells, which might be further utilized in targeted imaging/monitoring beta cells and theragnosis for beta-cells-related disease (diabetes, insulinoma, etc.).

Nanotechnology in Immunotherapy for Type 1 Diabetes: Promising Innovations and Future Advances

Diabetes is a chronic condition which affects the glucose metabolism in the body. In lieu of any clinical “cure,” the condition is managed through the administration of pharmacological aids, insulin supplements, diet restrictions, exercise, and the like. The conventional clinical prescriptions are limited by their life-long dependency and diminished potency, which in turn hinder the patient’s recovery. This necessitated an alteration in approach and has instigated several investigations into other strategies. As Type 1 diabetes (T1D) is known to be an autoimmune disorder, targeting the immune system in activation and/or suppression has shown promise in reducing beta cell loss and improving insulin levels in response to hyperglycemia. Another strategy currently being explored is the use of nanoparticles in the delivery of immunomodulators, insulin, or engineered vaccines to endogenous immune cells. Nanoparticle-assisted targeting of immune cells holds substantial potential for enhanced patient care within T1D clinical settings. Herein, we summarize the knowledge of etiology, clinical scenarios, and the current state of nanoparticle-based immunotherapeutic approaches for Type 1 diabetes. We also discuss the feasibility of translating this approach to clinical practice.

Noninvasive Tracking of mPEG-poly(Ala) Hydrogel-Embedded MIN6 Cells after Subcutaneous Transplantation in Mice

Recently, we demonstrated the feasibility of subcutaneous transplantation of MIN6 cells embedded in a scaffold with poly(ethylene glycol) methyl ether (mPEG)-poly(Ala) hydrogels. In this study, we further tracked these grafts using magnetic resonance (MR) and bioluminescence imaging. After being incubated overnight with chitosan-coated superparamagnetic iron oxide (CSPIO) nanoparticles and then mixed with mPEG-poly(Ala) hydrogels, MIN6 cells appeared as dark spots on MR scans. For in vivo experiments, we transfected MIN6 cells with luciferase and/or incubated them overnight with CSPIO overnight; 5 × 10⁶ MIN6 cells embedded in mPEG-poly(Ala) hydrogels were transplanted into the subcutaneous space of each nude mouse. The graft of CSPIO-labeled MIN6 cells was visualized as a distinct hypointense area on MR images located at the implantation site before day 21. However, this area became hyperintense on MR scans for up to 64 days. In addition, positive bioluminescence images were also observed for up to 64 days after transplantation. The histology of removed grafts showed positive insulin and iron staining. These results indicate mPEG-poly(Ala) is a suitable scaffold for β-cell encapsulation and transplantation. Moreover, MR and bioluminescence imaging are useful noninvasive tools for detecting and monitoring mPEG-poly(Ala) hydrogel-embedded MIN6 cells at a subcutaneous site.