The Effects Of Matrix Metalloproteinase （MMP）-13 On The Properties Of Dendritic Cells In Mice

ObjectiveThe skin is inhabited by several populations of immune cells that act as the first line of defense against invading pathogens.Dendritic cells（DCs）play important sentinel functions.The outcome of a cutaneous immune response is critically dependent upon the ability of DCs to migrate from skin to the draining lymph nodes.DCs are bone marrow-derived antigen-presenting cells（APCs）with high specificity,which play an important role in the induction and regulation of immune response.Langerhans cells（LCs）were classified as DCs,are immune cells in the epidermis.After LCs ingest and process antigens,they migrate from epidermis to draining lymph nodes,present antigens to T cells,and induce immunogenicity or tolerance responses.MMP-13 is a member of the collagenase subfamily of matrix metalloproteinases（MMPs）.It plays an important role in extra-cellular matrix circulation,cancer cell migration,cell growth,inflammation and angiogenesis.At present,studies have found the existence of MMP-13 in mouse bone marrow-derived dendritic cells（BMDCs）.Compared with other MMPs（such as MMP-2 and MMP-9）,the expression pattern of MMP-13 is more limited by DCs.Now,the research on the function of MMP-13 in DCs is still uncertain.In this study,mice with specific MMP-13 knock-out（KO）in DCs were constructed by using the Cre/lox P system.DCs were cultured from mouse bone marrow cells,and LCs in mouse ear epidermis were detected to study the role of MMP-13 in DCs.To provide theoretical support for further exploring the effects of MMP-13 on DCs function.MethodsIn this study,C57BL/6J mice at 6-8 weeks were selected as the research objects,mice with specific MMP-13 KO in DCs（KO mice）were constructed by Cre/lox P system as the experimental group and MMP-13 lox P homozygous mice without Cre activity（lox P mice）as the control group.The morphology of LCs in the ear epidermis of KO mice and lox P mice was observed by immunohistochemical staining.The cell number and dendrite number of LCs were counted and analyzed in five fields randomly selecting under 10×40 times light microscope.Mouse bone marrow cells were isolated and induced to differentiate into BMDCs in vitro.BMDCs with specific MMP-13 KO extracted and induced from the bone marrow of KO mice were used as experimental group(hereinafter referred to as MMP-13-KO^DCBMDCs),and wild-type BMDCs extracted and induced from the bone marrow of lox P mice were used as control group(hereinafter referred to as WT^loxBMDCs).The cellular functions of MMP-13-KO^DCBMDCs and WT^loxBMDCs were detected.CCK-8 kit was used to detect the proliferation of MMP-13-KO^DCBMDCs and WT^loxBMDCs.Flow cytometry was used to detect the expression of surface maturation markers CD80,CD86 and MHCⅡof MMP-13-KO^DCBMDCs and WT^loxBMDCs,as well as the proportion of apoptosis and phagocytosis.Results1.Compared with lox P mice epidermal LCs,KO mice epidermal LCs showed atrophy of cell body,and decreased number of dendrites and cells.2.Compared with WT^loxBMDCs,there was no significant difference in CCK-8proliferation activity of MMP-13-KO^DCBMDCs.3.Compared with WT^loxBMDCs,the expression of surface maturation markers CD80,CD86,and MHCⅡof MMP-13-KO^DCBMDCs was decreased.4.Compared with WT^loxBMDCs,MMP-13-KO^DCBMDCs had an increased proportion of FITC-Dextran uptake.5.Compared with WT^loxBMDCs,the proportion of apoptotic cells in MMP-13-KO^DCBMDCs was increased.Conclusion1.MMP-13 deletion of mouse epidermal LCs resulted in abnormal cell morphology and reduced cell number.2.After specific knockout of MMP-13 in DCs,the maturation ability of BMDCs was decreased,the antigen phagocytosis capacity of BMDCs was improved,cell apoptosis of BMDCs was increased,and the proliferation capacity of BMDCs was not affected.