摘要：肝細胞移植手術是一個對急性肝衰竭病人有前瞻性的治療選擇。相較於肝臟移植，肝細胞移植手術有侵入性較小的優點。目前臨床肝細胞移植的成功率不如動物實驗一般有效穩定。諸多因素有待改進：細胞來源及品質、純化流程及輸注手術等方面皆會影響最後的成效。輸注手術方面，我們發現經大鼠肝門靜脈輸注肝細胞治療急性肝損傷大鼠時， 適當的速度可產生較早及較佳的engraftment 及repopulation。不過在急性肝衰竭的情況下，大量肝細胞死亡，環境險惡，急需大量成熟的肝細胞。移植進入的肝細胞數量經研究改良雖有增加，可是增生速率不如預期，離實際臨床應用仍有距離。間質幹細胞藉由分泌生長因子、細胞激素及細胞間質等，具有支持肝細胞功能，促進肝細胞增生，抑制肝細胞自殺，以及減緩發炎的能力。在器官移植後再加入間質幹細胞移植的臨床研究亦發現可減少急性排斥的發生。急性肝損傷的間質幹細胞移植文獻報告少且長期效益的機制不明，一方面因為缺乏成熟肝細胞可立即發揮功能穩住個體存活，一方面在急性肝損傷的微環境險惡，不利幹細胞長期存活分化。我們假設肝細胞移植後再加入間質幹細胞移植，可促進移植肝細胞增生，減少肝細胞傷亡，同時幹細胞可得到較佳的環境發揮作用及順勢分化，進一步提升移植細胞的長期殖入率。我們將利用純化的螢光基因轉殖大鼠(DsRedT3-emGFP SD rat) 間質幹細胞在藥物處理下可產生螢光轉換(紅轉綠)的現象，取得不同螢光的肝細胞(紅)及間質幹細胞(綠)進行移植，以進一步了解在此急性肝損傷大鼠模式下間質幹細胞順勢分化(分化成parenchymal, non-parenchymal,抑或協調肝前驅細胞)的過程，並可深入探討間質幹細胞與肝細胞、微環境及分泌因子間交互作用、以及長期移植後(長達6個月)的殖入變化。我們希望藉由這項臨床前期轉譯研究的發現，提出可以進一步改善臨床肝細胞移植的成果。
Abstract: Hepatocyte transplantation is a promising alternative to liver transplantation in patients diagnosed with acute liver failure. Excellent results from animal studies cannot, however, fully translated into clinical practice possibly due to several reasons: not so ideal quality of cells transplanted, lack of proper recipient liver preconditioning protocol, and difference of transfusion technique. We had found that adequate rate of cell transfusion has better early engraftment and repopulation of transplanted hepatocytes in acute liver injured rat model. In the scenario of acute liver failure (massive hepatocyte deaths and hostile inflammatory background), however, urgent need of large amount of functional mature hepatocytes is mandatory. In our acute liver injured rat model (D-gal induced), though more clinically mimicking, transplanted hepatocytes were not proliferative in great degrees. Mesenchymal stem cells (MSCs) can support hepatocyte functions, promote hepatocyte proliferation, inhibit apoptosis, and ameliorate inflammation by secreting growth factors, cytokines, and extracellular matrix. Clinically, there are reports that solid organ transplantation accompanied with MSC transplantation can reduce the rate of acute rejection. Reports of MSC transplantation in the setting of acute liver failure is few and the mechanism of long-term benefit remains elusive because of the short term effect in the hostile microenvironment and lacking of mature hepatocyte function. We hypothesize that facilitated differentiation of co-transplanted MSC improves long-term repopulation efficiency of hepatocyte-MSC transplantation for acute liver injured rats. Transplanted hepatocytes can proliferate extensively and MSCs can accommodate better and facilitated differentiation, the latter of which further improve transplanted cell repopulation efficiency. We will utilize fluorescent DsRedT3-emGFP SD rats as the donor source of hepatocytes and MSCs. Under tamoxifen treatment, the MSCs of rat turn from red to green. We will use different fluorescent colors of hepatocytes (red) and MSCs (green) to trace the course of MSC differentiation post transplantation [whether differentiated into parenchymal (hepatocyte, cholangiocyte), nonparenchymal (sinusoidal endothelial cells, stellate cell) or just remains as MSC but govern partially differentiated cells (progenitor cells)], soluble factors and interaction of MSC with hepatocytes and microenvironment, and long-term transplanted cell repopulation up to 6 months. We hope this preclinical translational study can further improve the efficiency of clinical hepatocyte transplantation.
