Rajvanshi P, Kerr A, Bhargava K K, Burk R D, Gupta S
Liver Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Hepatology. 1996 Mar;23(3):482-96. doi: 10.1002/hep.510230313.
The feasibility of liver repopulation with hepatocytes has been shown, although clinical applications demand significant hepatic replacement. To show whether portal vascular bed in large animals could accomodate a greater cell number, we analyzed liver repopulation in syngeneic Fischer 344 rats deficient in dipeptidyl peptidase IV. This system allowed localization of transplanted normal hepatocytes in liver or various ectopic sites, as well as dual studies for analysis of gene expression. Interestingly, the product of a dipeptidyl peptidase IV substrate inactivated bile canalicular adenosine triphosphatase (ATPase) activity in normal but not in dipeptidyl peptidase IV-deficient rats, which allowed localization of dipeptidyl peptidase IV-deficient hepatocytes in normal rat liver for additional reversed transplantation systems. Further studies with genetically marked cells showed that because of the size difference between hepatocytes and portal vein radicles, intrasplenically transplanted cells were distributed in periportal areas (zone 1) in mice, whereas in larger animals (rats or rabbits) cells were also distributed downstream to midlobular (zone 2) or perivenous (zone 3) areas. Transplantation of an escalating number of hepatocytes showed that adult rats tolerated intrasplenic injection of a large cell number in single sessions (up to 1 X 10(8), approximately 10% to 15% of the host hepatocyte mass). Morphometric analysis of recipient livers showed survival of a significantly greater cell number with incorporation in host liver plates. At 4 weeks, transplantation of 2 x 10(7) hepatocytes into adult rats led to a survival of 1.4 +/- 1.0 x 10(6) transplanted cells/cm3 liver, whereas after transplantation of 5 x 10(7) cells or 7.5 x 10(7) cells, the number of surviving transplanted cells in the liver significantly increased to 4.1 +/- 1.4 x 10(6) transplanted cells/cm3 liver (mean, 2.9-fold; P<.003) and 5.5 +/- 1.3 x 10(6) transplanted cells/cm3 liver (mean, 3.9-fold; P<.003), respectively. When cells were injected in greater numbers, transplanted hepatocytes retained normal function and produced more serum albumin or hepatitis B surface antigen in deficient hosts. These data indicate the feasibility in larger animals of significant liver repopulation with hepatocyte transplantation. Use of dipeptidyl peptidase IV-deficient rats should help further analysis of mechanisms in liver repopulation.
肝细胞肝脏再填充的可行性已得到证实，尽管临床应用需要大量的肝脏替代。为了研究大型动物的门静脉血管床是否能容纳更多的细胞，我们分析了缺乏二肽基肽酶IV的同基因Fischer 344大鼠的肝脏再填充情况。该系统可以将移植的正常肝细胞定位在肝脏或各种异位部位，还可以进行双重研究以分析基因表达。有趣的是，二肽基肽酶IV底物的产物可使正常大鼠而非二肽基肽酶IV缺陷大鼠的胆小管三磷酸腺苷酶（ATPase）活性失活，这使得二肽基肽酶IV缺陷的肝细胞能够定位在正常大鼠肝脏中，用于额外的反向移植系统。对基因标记细胞的进一步研究表明，由于肝细胞和门静脉分支大小不同，脾内移植的细胞在小鼠中分布于门静脉周围区域（1区），而在大型动物（大鼠或兔子）中，细胞也分布到小叶中部（2区）或静脉周围（3区）区域的下游。递增数量的肝细胞移植表明，成年大鼠能够耐受单次脾内注射大量细胞（高达1×10⁸个，约占宿主肝细胞质量的10%至15%）。对受体肝脏的形态计量分析表明，大量细胞存活并整合到宿主肝板中。4周时，将2×10⁷个肝细胞移植到成年大鼠体内，导致移植细胞在肝脏中的存活率为1.4±1.0×10⁶个移植细胞/cm³肝脏，而移植5×10⁷个细胞或7.5×10⁷个细胞后，肝脏中存活的移植细胞数量显著增加至4.1±1.4×10⁶个移植细胞/cm³肝脏（平均为2.9倍；P<0.003）和5.5±1.3×10⁶个移植细胞/cm³肝脏（平均为3.9倍；P<0.003）。当注射更多数量的细胞时，移植的肝细胞保持正常功能，并在缺陷宿主中产生更多的血清白蛋白或乙型肝炎表面抗原。这些数据表明在大型动物中通过肝细胞移植实现显著肝脏再填充是可行的。使用二肽基肽酶IV缺陷大鼠应有助于进一步分析肝脏再填充的机制。
