Sodium Alginate-organoid Microspheres From Microfluidics For Treating Inflammatory Bowel Disease

BackgroundInflammatory bowel disease（IBD）,exemplified by Crohn’s disease（CD）and ulcerative colitis（UC）,whose incidence and prevalence increase year by year have a great negative impact on patients’physical and psychological health as well as the society.It remains a significant challenge to cure IBD because of the complex etiological factors and clinical symptoms.Current treatments for IBD mainly focus on anti-inflammatory and immune regulation,which bring up many side effects,and their curative effects are not ideal.In recent years,stem cell transplantation has become a new treatment for IBD,but there are still some problems such as cell retention,low survival rate and low efficiency of transplantation.The development of microfluidic technologies makes it possible to solve this problem.Crypts containing intestinal stem cells wrapped in hydrogel microspheres can improve the survival rate of cells in the process of transplantation and improve the efficiency of transplantation,which should have a good application prospect.In this paper,hydrogel microspheres contained stem cells were prepared by microfluidic electrospray technique for stem cell transplantation and their role in treating IBD was investigated.MethodsFirstly,we established a mice intestinal organoids culture system in vitro,in order to obtain the intestinal organoids with the structure and function of intestinal epithelial cells.And then we built a capillary microfluidic device,where sodium alginate（sodium alginate,Na-alg）solution served as the outer phase,while mature mice intestinal organoids in Matrigel and carboxymethylcellulose（CMC）as the inner phase.By electric spray,the organoids and the surroundings were wrapped in Na-alg,and after dropping in 2%Ca Cl₂,the Na-alg was gelled and microspheres were formed.The morphology and structure of microspheres were detected by optical microscope and scanning electron microscope.The degradation ability of microspheres was evaluated by a degradation experiment.Biocompatibility of microspheres was evaluated by cell experiments.In the dextran sulfate sodium（DSS）-induced colitis mouse model,phosphate buffer solution（PBS）,PBS containing organoids,microspheres containing organoids in PBS were respectively used for enema,and the efficacy of these methods in repairing colitis was evaluated through general observation,cytokines detection and histological analysis.ResultsWe have successfully established a culture system for mice intestinal organoids in vitro.The extracted intestinal crypts can differentiate and develop into various types of intestinal epithelial cells and can be passed on in a stable manner.The prepared sodium alginate microspheres had good spherical shape and monodispersity.In the degradation experiment,the microspheres hardly degrade in the simulated gastric fluid,but rapidly cracked in the simulated intestinal fluid in vitro,so as to quickly release the contents of the microspheres in a specific p H environment.Cell experiments have proved that the microspheres have good biocompatibility,so that the cells can grow normally in the microspheres.In the model of ulcerative colitis in mice,the organoids could be transported and transplanted into mice without being damaged by the mechanical force under the protection of microspheres,and mice with colitis could benefit from the treatment.ConclusionsThe microspheres prepared by microfluidic technology can provide a protective environment for organoids,improving the success rate of transplantation,and provide a new platform for the treatment of IBD.