Liu Jing-Jing, Hu Xiao-Jun, Li Zheng-Ran, Yan Rong-Hua, Li Dan, Wang Jin, Shan Hong
Department of Radiology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
Guangdong Provincial Engineering Research Center of Molecular Imaging, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, 519000, China.
Mol Imaging Biol. 2017 Feb;19(1):31-40. doi: 10.1007/s11307-016-0962-9.
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 (R = 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.
间充质基质细胞（MSCs）在肝病治疗中具有应用前景。然而，肝内移植后MSCs的存活时间较短限制了其应用价值；因此，了解MSCs存活和排斥的基础可能会提高其效用。本研究旨在确定肝内自然杀伤（NK）细胞对MSCs存活的作用以及移植后短期内它们在肝脏中的留存情况。
用人源MSCs标记Luc2-mKate2双融合报告基因（MSCs-R），通过体内生物发光成像（BLI）评估肝内移植后MSCs-R异种移植物的停留时间和存活情况。进行MSCs与NK细胞的共培养以评估细胞毒性。为了评估NK细胞在异种移植细胞排斥中的作用，在激活肝内NK细胞后，通过BLI在体内评估移植的MSCs-R的命运。
我们观察到活的MSCs-R的荧光素酶活性与体外细胞数量之间呈线性相关（R = 0.9956）。在体内，我们观察到对照组和NK激活组中，与肝脏相对应区域内移植的MSCs-R的生物发光信号逐渐下降。然而，与对照组相比，NK激活组小鼠肝内MSCs-R的存活时间和留存情况下降得更快。这表明激活的NK细胞加速了移植MSCs的清除。此外，我们发现肝内递送MSCs后，肝内NK细胞数量和NK激活标志物的表达显著增加。这表明处于静息状态的驻留NK细胞被人源MSCs的肝内移植激活。综上所述，数据表明激活的肝内NK细胞部分介导了MSCs异种移植物的排斥。细胞毒性试验表明，激活的NK细胞可能抑制MSCs的增殖，并在一定程度上诱导MSCs死亡。
通过BLI可在体内动态追踪人源MSCs，并且可以从MSCs信号的丧失推断小鼠肝内NK细胞的作用，尤其是激活的NK细胞。这一发现可能对MSCs移植治疗肝病具有实际临床意义。
