Study On Inulin And Thermosensitive GelMA Hydrogel In Optimizing Pancreatic Islet Transplantation For The Treatment Of Diabete

Diabetes is a chronic metabolic disorder,affecting 7%of people worldwide.China is a country with the largest diabetic population.Particularly,in recent years,with the change of lifestyle and improved quality of living,incidents of diabetes is increasing at an alarming rate,accompanied by decreased age of onset.Type 1 diabetes is an autoimmune disease characterized by pancreatic islet β-cell death and shortage of insulin secretion.The sustained increase in plasma glucose levels results in multiple diabetic complications,including macro-and microvascular diseases.Although the exact etiology of type 1 diabetes remains unclear,it is now generally believed that a combination of immune factors,genetic dispositions as well as environmental factors is the common cause of type 1 diabetes onset.Islet transplantation has been considered as one of the most promising therapeutic approaches to reverse type 1 diabetes.Although major progress has been made in the past few decades,shortage of organ donors,post-transplantation graft failure due to poor engraftment and host immune rejection still pose as major challenges that limit the clinical applicability of islet transplantation.Considering the aforementioned limitations,we have investigated the potential of using biomaterials in assisting islet transplantation.Inulin is an oligosacchrride that is typically used as dietary supplements.In addition.it has also been reported that inulin with low-degree polymerization could improve insulin sensitivity while exhibit anti-inflammatory,anti-hypoxic,and pro-angiogenic properties.Given the multitude of metabolic benefit of low-degree polymerized inulin,w e adopted an islet cell surface engineering approach with inulin.Thus,inulin was initially oxidized and the resulted-CHO groups of the oxidized inulin would then react w ith the-NH2 groups on the surface of islet cells to achieve surface engineering of the pancreatic islets.Results obtained by scanned electron microscopy(SEM)demonstrated that the structure of inulin is highly similar to the extracellular matrix(ECM)that surround the native pancreatic islets,implicating excellent physical support offered by the ECM-mimicking inulin.Subsequent examination with transmission electron microscope(TEM)and confocal microscopy showed that the oxidized inulin can indeed form a layer of inulin deposition across the periphery of mouse pancreatic islets.More importantly.inulin-coated mouse islets also exhibited better glucose responsiveness and endothelial cell tube formation.In addition,reduced apoptosis and intracellular reactive oxygen species(ROS)levels under proinflammatory condition were also observed,confirming the anti-inflammatory and antihypoxic properties of inulin as previously reported.RNA-seq analysis further confirmed significant beneficial alteration in the expression levels of genes related to insulin secretion.angiogenesis and immune regulation in the inulin islets.Furthermore.in vivo results of islet transplantation experiments using streptozotocin-induced hyperglycemic mice showed that mice that have received inulin islet exhibited improved blood glucose levels,which are attributable to ameliorated CD45+immune cell infiltration.enhanced lectin+endothelial cell recuitment and graft insulin expression as detected by immunofluorescence staining.Therefore,the use of oxidized inulin for islet surface engineering modification showed promising potential as a safe and effective approach to optimize clinical islet transplantation.In addition,we also carried out preliminary investigation on islet co-transplantation with functional cells such’as endothelial cells.In order to facilitate co-transplantation of multiple types of cells,we designed and prepared 18 different hydrogels formed with various combination of GelMA,methacryloyl compounds,N-isopropylacrylamide(NIPAM)and crosslinkers.GelMA-based thermosensitive hydrogels with specific volume phase transition temperature(VPTT)range and porosity suitable for cell culturing and delivery were selected.Mouse pancreatic islet endothelial cells(MS1)and mouse pancreatic islet β-cells(MIN6)were used as model cell lines for hydrogel-cell culturing assays.The selected GelMA-based thermosensitive hydrogels exhibited excellent cytocompatibility,with no detrimental impact on cell viability,morphology,cell proliferation and migration.Further in vivo investigation using the thermosensitive GelMA-based hydrogels for co-transplantation of islets with functional cells would be performed in the future to reveal the applicability of these hydrogels in assisting islet transplantation.