In Vitro Differentiation Of Rat Bone Marrow-derived Mast Cells And Mechanism Research Of Macrophage Polarization Mediatied By Intestinal Mast Cells In Inflammatory Bowel Disease

Mast cells(MCs),a class of innate immune cells,not only participate in immune surveillance,but also play a key role in the initiation of early innate immune responses for the resistance of invading pathogens;MC originates from hematopoietic stem cells in the bone marrow,and then become mature in resident target organ.Eventually they form specific phenotype in response to specific tissue microenvironment.In tissue,MC accounts for only 10% of all immune cells.Thus,the amount of MC harvested from tissue remains limited.In order to obtain sufficient MC for related scientific research,ways for culturing large amounts of MC in vitro have been explored for decades year.With the advancement of technology,methods for mouse MC have been widely used.However,due to lots of obstacles in the process of culturing rat MC in vitro,almost no relatively reliable methods for rat bone marrow-derived MC(BMMC)are reported.Compared with mouse MC,rat MC is more suitable for studying its potential mechanism against parasitic infections such as Trichinella spiralis and Clonorchis sinensis,due to the susceptibility of rats to these kinds of parasites.In this research,we reported a fast,effective and simple rat BMMC culture method.In our method,rat recombinated Stem Cell Factor(rr SCF)plays a key role in this process.Compared with the previously unreliable methods,rat BMMC obtained by us showed significant advantages in differentiation,proliferation,lifespan and function.At the same time,it reveals the mucosal MC phenotype,helping to elucidate the function of mucosal MC involved in the developments of various diseases such as asthma,inflammatory bowel disease,etc.In addition,MCs from gastrointestinal(GI)are one series of important immune cells.Most of them settled in the lamina propria(LP)of the GI tract,accounting for approximately 2% to 3% of total immune cells,revealing the phenotype of mucosal MC.MCs from GI regulate many physiological functions,such as altering blood flow,regulating smooth muscle contraction and bowel movements,affecting intestinal mucosal secretion and promoting innate or adaptive immune responses.In the progress of inflammatory bowel disease(IBD),MCs settled in inflammatory mucosa participate in the coordination of epithelial reactions.When the intestinal tract is invaded by inflammation,the mucosa releases a large amount of substances such as SCF and MMP-9,promoting the enrichment of MCs.In our research,we found that in the absence of lesions,the number of MC in the intestine was limited,and even in the inflammatory phase of IBD,the levels of MCs number did not increase significantly.However,during the recovery period of inflammation,the number of MC was significantly up-regulated.In addition,the lack of MC enrichment seriously affects the homeostasis of the intestinal tissue,and then influences the intestinal immune balance,eventually causes the destroy of self-repair function in intestinal tissue.As the research progressed,we found that MC incline to play an indirect regulatory role rather than a direct regulation role,and macrophages may be one of the targets regulated by MCs.There are two phenotypes in macrophages,M1 and M2.The former plays a key role in pro-inflammatory effects,while the latter contributes to anti-inflammatory progress.We found that GI MCs significantly affected the polarization of the phagocytes in intestinal macrophages.They reduced the inflammation not only by promoting the enrichment of M2 macrophages but also by inhibiting the chemotaxis of M1 macrophages.