Wu Hao-Hsiang, Lee Oscar K
Institute of Biophotonics, National Yang-Ming University, No.155, Sec.2, Linong Street, Taipei, 112, Taiwan.
Taipei City Hospital, No.145, Zhengzhou Road, Datong District, Taipei, 10341, Taiwan.
Stem Cell Res Ther. 2017 May 23;8(1):117. doi: 10.1186/s13287-017-0560-z.
We previously reported that mesenchymal stem cells (MSCs) possess therapeutic effects in a murine model of carbon tetrachloride-induced acute liver failure. In the study, we observed that the majority of repopulated hepatocytes were of recipient origin and were adjacent to transplanted MSCs; only a low percentage of repopulated hepatocytes were from transplanted MSCs. The findings indicate that MSCs guided the formation of new hepatocytes. Exosomes are important messengers for paracrine signaling delivery. The aim of this study is to investigate the paracrine effects, in particular, the effects of exosomes from MSCs, on hepatocytes.
Mature hepatocytes were isolated from murine liver by a two-step perfusion method with collagenase digestion. MSCs were obtained from murine bone marrow, and conditioned medium (CM) from MSC culture was then collected. Time-lapse imaging was used for observation of cell morphological change induced by CM on hepatocytes. In addition, expression of markers for hepatic progenitors including oval cells, intrahepatic stem cells, and hepatoblasts were analyzed.
Treatment with the CM promoted the formation of small oval cells from hepatocytes; time-lapse imaging demonstrated the change from epithelial to oval cell morphology at the single hepatocyte level. Additionally, expression of EpCAM and OC2, markers of hepatic oval cells, was upregulated. Also, the number of EpCAM cells was increased after CM treatment. The EpCAM small oval cells possessed colony-formation ability; they also expressed cytokeratin 18 and were able to store glycogen upon induction of hepatic differentiation. Furthermore, exosomes from MSC-CM could induce the conversion of mature hepatocytes to EpCAM small oval cells.
In summary, paracrine signaling through exosomes from MSCs induce the conversion of hepatocytes into hepatic oval cells, a mechanism of action which has not been reported regarding the therapeutic potentials of MSCs in liver regeneration. Exosomes from MSCs may therefore be used to treat liver diseases. Further studies are required for proof of concept of this approach.
我们之前报道过，间充质干细胞（MSCs）在四氯化碳诱导的急性肝衰竭小鼠模型中具有治疗作用。在该研究中，我们观察到大多数重新填充的肝细胞来源于受体，且与移植的MSCs相邻；只有一小部分重新填充的肝细胞来自移植的MSCs。这些发现表明MSCs引导了新肝细胞的形成。外泌体是旁分泌信号传递的重要信使。本研究的目的是探讨旁分泌效应，特别是MSCs来源的外泌体对肝细胞的影响。
通过两步灌注法并用胶原酶消化从小鼠肝脏中分离出成熟肝细胞。从鼠骨髓中获取MSCs，然后收集MSC培养的条件培养基（CM）。采用延时成像观察CM对肝细胞诱导的细胞形态变化。此外，分析了包括卵圆细胞、肝内干细胞和成肝细胞在内的肝祖细胞标志物的表达。
用CM处理可促进肝细胞形成小卵圆细胞；延时成像在单个肝细胞水平上显示了从上皮细胞形态向卵圆细胞形态的变化。此外，肝卵圆细胞标志物EpCAM和OC2的表达上调。而且，CM处理后EpCAM阳性细胞数量增加。EpCAM阳性小卵圆细胞具有集落形成能力；它们还表达细胞角蛋白18，并且在诱导肝分化时能够储存糖原。此外，MSC-CM来源的外泌体可诱导成熟肝细胞转化为EpCAM阳性小卵圆细胞。
总之，MSCs来源的外泌体通过旁分泌信号诱导肝细胞转化为肝卵圆细胞，这是一种关于MSCs在肝脏再生中的治疗潜力尚未见报道的作用机制。因此，MSCs来源的外泌体可用于治疗肝脏疾病。需要进一步研究来验证这种方法的概念。
