title: In Vivo Bioluminescence Imaging of Transplanted Mesenchymal Stromal Cells and Their Rejection Mediated by Intrahepatic NK Cells.
abstract: Mesenchymal stromal cells (MSCs) hold promise in the treatment of liver disease. However, short survival time of MSCs after intrahepatic transplantation limits their value; therefore, understanding the basis of MSCs survival and rejection may increase their utility. This study was aimed at determining the role of intrahepatic natural killer (NK) cells on MSCs survival and their retention in the liver shortly after transplant.
  
  
  
  Human MSCs were labeled with the Luc2-mKate2 dual-fusion reporter gene (MSCs-R), and the residence time and survival of MSCs-R xenografts after intrahepatic transplantation were evaluated by in vivo bioluminescence imaging (BLI). Coculture of MSCs and NK cells was performed to assess cytotoxicity. To evaluate the role of NK cells in rejection of the xenografted cells, the fates of transplanted MSCs-R were then assessed in vivo by BLI after activation of intrahepatic NK cells.
  
  
  
  We observed a linear correlation between luciferase activity from live MSCs-R and cell number in vitro (R2= 0.9956). In vivo, we observed a gradual decline in bioluminescent signals from transplanted MSCs-R over a region corresponding to the liver in both the control group and the NK-activated group. However, the survival time and retention of intrahepatic MSCs-R decreased more rapidly in the NK-activated group of mice compared to the control group. This indicated that activated NK cells accelerate the elimination of transplanted MSCs. Also, we found that the number of hepatic NK cells and the expression of NK activation markers significantly increased after intrahepatic delivery of MSCs. This suggested that resident NK cells, in a resting state, were activated by intrahepatic transplantation of human MSCs. Taken together, the data suggests that activated hepatic NK cells mediate, in part, rejection of the MSCs xenografts. Cytotoxicity assays showed that activated NK cells may inhibit the proliferation of MSCs and, to a certain extent, induce MSCs death.
  
  
  
  Human MSCs could be followed dynamically in vivo by BLI, and the role of murine hepatic NK cells, especially activated NK cells, could be inferred from the loss of signals from MSCs. This finding may have practical clinical implications in MSCs transplantation in treating liver disease.
authors.affiliation: Department of Radiology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
authors.forename: Jing-Jing
authors.initials: JJ
authors.lastname: Liu
authors.affiliation: Guangdong Provincial Engineering Research Center of Molecular Imaging, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, 519000, China.
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Hu
authors.affiliation: Department of Radiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510630, China.
authors.forename: Zheng-Ran
authors.initials: ZR
authors.lastname: Li
authors.affiliation: Department of Radiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510630, China.
authors.forename: Rong-Hua
authors.initials: RH
authors.lastname: Yan
authors.affiliation: Guangdong Provincial Engineering Research Center of Molecular Imaging, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, 519000, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: Department of Radiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510630, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.affiliation: Guangdong Provincial Engineering Research Center of Molecular Imaging, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, 519000, China. shanhong@mail.sysu.edu.cn.|Center for Interventional Medicine, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, 519000, China. shanhong@mail.sysu.edu.cn.|Institute of Interventional Radiology of Sun Yat-sen University, Zhuhai, 519000, China. shanhong@mail.sysu.edu.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Shan
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D018920:Coculture Techniques; D005434:Flow Cytometry; D017930:Genes, Reporter; D006801:Humans; D019409:Interleukin-15 / Q000378:metabolism; D007694:Killer Cells, Natural / Q000276:immunology*; D008099:Liver / Q000166:cytology*; D008163:Luminescent Measurements / Q000379:methods*; D008213:Lymphocyte Activation; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D008642:Mesenteric Veins; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D053647:Receptors, Interleukin-15 / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: C508025:Il15ra protein, mouse; D019409:Interleukin-15; D053647:Receptors, Interleukin-15
keywords: Bioluminescence imaging; Immune rejection; Liver disease; Mesenchymal stem cells; Xenograft