摘要:細胞移植有許多優點,並且可能取代器官移植成為器官衰竭病人的第一治療選擇。不管在動物實驗或臨床上肝細胞移植已被證明可以用來治療多種不同的肝臟疾病,包括代謝性肝臟疾病,急性肝臟衰竭和慢性肝臟硬化。從我們過去的研究顯示通常每一次我们只能移植1~2%的肝細胞,且約只有20%的移植肝細胞能嵌入受贈者肝臟內。如此有限的嵌入移植肝細胞(佔整個肝臟體積的0.2~0.4% )並不能達到我們治療肝臟疾病代謝缺失的目地。如何增加移植肝細胞的數目及擴展移植細胞的來源以改善肝細胞移植的治療效果是肝細胞移植成為臨床上肝臟疾病新的治療方式前需克服的兩大問題。在筆者過去五年的研究結果顯示,肝細胞和幹細胞一樣有很強的分裂增殖能力,並且在經過受贈者的前置治療後能夠廣泛的取代宿主的肝細胞,將來我們可能只需要移植少量的捐贈者肝細胞(少於受贈者肝臟體積的1%),經過適當的刺激後,他們能夠在受贈者肝臟內不斷複製,並達到我們治療的需求(大於30%的受贈者肝臟被捐贈者肝細胞所取代)。在我們所研究出來的宿主非侵入性前置治療下不僅可增加移植肝細胞嵌入宿主肝臟的比例,並且可誘導嵌入的移植肝細胞不斷複製,進而大範圍取代宿主肝細胞。(1-4) 近兩年來我們使用第九凝血因子惕除小鼠為研究模式(血友病B 的動物模式),發現在我们發展出來的捐贈者前置治療下可以很有效的增加肝細胞移植對此類肝臟基因缺陷疾病的治療效果。(5)擴展移植細胞的來源是另一個重要的課題。治療肝臟疾病細胞移植的來源除了肝細胞外,幹細胞也是另一個選擇,並且可以解決細胞來源短缺及移植後排斥的問題。誘導性全能幹細胞 (induced pluripotent stem cell, iPS cell) 具有與胚胎幹細胞相同特質,可以在體外被誘導分化為各種體細胞,更是增加移植細胞來源的選擇性。在此計畫中我們打算使用第九凝血因子惕除小鼠為研究模式(血友病B 的動物模式),並將iPS細胞誘導分化成具有功能性的肝細胞探討其治療潛力;另一方面利用過去我们所發展出來的宿主非侵入性前置治療模式,研究 iPS 細胞分化後的肝細胞移植對此基因缺陷肝臟疾病的治療效果。細胞移植能成為臨床上治療肝臟疾病病人新的選擇。宿主的前置治療可有效改善肝細胞移植的治療效果,將iPS 細胞誘導分化成具有功能性的肝細胞更可解決細胞來源短缺及移植後排斥的問題。從此計劃中我们不僅可了解此種新的治療方式對肝臟基因缺陷疾病的療效,並可發展將來臨床上可行的宿主前置治療方式及擴展移植細胞的來源。
Abstract: Cell transplantation has many advantages and has the potential to replace the wholeorgan transplantation as the first therapeutic choice for patients with organ failure. Recently,hepatocyte transplantation has been demonstrated as an effective therapeutic strategy fordifferent kinds of liver disease in animals and clinical trials, including metabolic liver disease,acute liver failure, and chronic liver cirrhosis. In our previous studies, we showed that justonly 1~2% hepatocytes can be transplanted into reciepients each time, and just only 20% oftransplanted cells have the opportunity to engraft into the recipient’s liver finally。We can’treach the therapeutic purpose to correct the metabolic deficiency of liver diseases by suchlimited engrafted transplanted hepatocytes (0.2~0.4% of the whole liver mass). How toimprove the therapeutic efficiency of hepatocyte transplantation by the increasing percentageof donor cells engraftment and expand the source of donor cells are two big issues toovercome before clinical application of this new therapeutic strategy.According to our studies in the past five years, hepatocyts have strong proliferativecapacity, and can repopulate extensively in the recipient’s liver by the replacement of therecipient’s hepatocytes after suitable preconditioning treatment of recipient. In ourpreconditioning protocol, we can transplant limited donor hepatocytes (less than 1% of thewhole liver volume) and reach eventually the therapeutic target (more than 30% of donor cellsrepopulation in the recipient’s liver) by continuing proliferation of the engrafted donor cells inthe recipient’s liver. We not only increased the percentage of donor cells engraftment but alsostimulated the proliferation of engrafted donor cells under our noninvasive preconditioningtreatment for the recipients. Both effects contributed to the improvement of therapeuticefficiency of hepatocyte transplantation.(1-4) We also demonstrated the donor preconditiong(genetic modified donor cells) can improve the therapeutic efficiency of hepatocytetransplantation for genetic liver disease in our factor IX knock-out mice (animal model forhemophilia B). (5) So, both the preconditioning treatment for donor and recipients have theadvantages to improve the therapeutic efficiency of cell transplantation for liver diseases fromour previous studies.(1-5)Stem cells are an alternative source of donor cells for cell transplantation, and canovercome the problems of organ shortage and posttransplantation rejection. Inducedpluripotent stem cells (iPS cells) have the characteristics of ES cells, and have beendemonstrated to differentiate into different kinds of somatic cells. The iPS cells can expandthe donor cell source of hepatocyte transplantation for liver disease. In this project, we plan toinvestigate the potential of differentiation of iPS cells into functional hepatocytes and studythe therapeutic efficiency of these iPS cells-derived hepatocytes transplantation for geneticliver disease--factor IX knockout mice (hemophilia B disease). Finally we will addresswhether the efficiency of iPS cells-derived hepatocyte transplantation can be improved by ourestablished preconditioning protocol.Cell transplantation is a new therapeutic strategy for liver diseases in clinical practice.The preconditioning treatment improves the therapeutic efficiency of hepatocytetransplantation. The generation of functional hepatoyctes from the iPS cells can overcomeproblems of organ shortage and rejection. In this project, we expect to disclose the efficiencyof hepatocyte transplantation for genetic liver disease, expanding the functional donor sourcefrom the iPS cells and try to identify the suitable preconditioning protocol for clinicalapplication.