In Vitro Study Of Mesenchymal Stem Cells Encapsulating Human Islets To Reduce Instant Blood-mediated Inflammatory Reaction

Objective:To explore the effect of mesenchymal stem cells（MSC）encapsulated islets on the instant blood-mediated inflammatory reaction（IBMIR）after islet transplantation,and provide a new idea for the application of MSC in islet transplantation and islet protection.Methods:Human islets were isolated and purified by semi-automatic method in vitro,and human umbilical cord MSC were identified and cultured in vitro.Then,MSC were directly co-cultured with human islets in a low-adhesion petri dish and incubated at 37℃and 5%CO₂for 24 h to achieve MSC-encapsulated islets.The co-localization of MSC and islets was observed by confocal microscopy to evaluate the degree of MSC encapsulation of islets.The activity and function of MSC encapsulated islets were evaluated.The blood circulation tube model was constructed in vitro.The 800 IEQ MSC-coated and uncoated islets were added to 3 m L fresh whole blood in the experimental group and the blank control group.The 0.2m L islet culture medium was added to 3 m L fresh whole blood and incubated at 37℃for 60 min.The reduction effect of MSC-encapsulated islets on IBMIR was evaluated by detecting coagulation,complement activation and inflammatory response.Results:Co-culture of MSC and islets in direct contact in low-adsorption dishes allowed MSC-encapsulated islets;the MSC-encapsulated islets had no effect on the activity and function of islets.In the coagulation response assay with increasing time,the mean platelets,neutrophils and monocytes decreased in both islet and MSC-wrapped groups;platelets,monocytes and neutrophils were higher in the MSC-wrapped group than in the islet group after 60 min of circulation（all P<0.05）;TAT and TF contents were lower in the MSC-wrapped group than in the islet group（all P<0.05）.In the complement activation assay,complement C3a and C5b-9 appeared to be elevated after islet entry;the expression levels of C3a and C5b-9 were lower in the MSC-wrapped group than in the islet group（all P<0.05）.In the inflammatory response assay,the expression levels of IL-1β,IL-6 and TNF-a were lower in the MSC-wrapped group than in the islet group（all P<0.05）.Conclusions:The direct contact co-culture of MSC and islets in a low adsorption dish allows MSC wrapped islets;MSC wrapped islets do not affect insulin secretory function and islet activity;MSC wrapped islets attenuate coagulation response,complement activation,inflammatory cell aggregation,and reduce the levels of inflammatory factors and chemokines,thus reducing IBMIR in the early stage of islet transplantation.