A novel strategy for in vivo expansion of transplanted hepatocytes using preparative hepatic irradiation and FasL-induced hepatocellular apoptosis

Abstract

A strategy for inducing preferential proliferation of the engrafted hepatocytes over host liver cells should markedly increase the benefit of hepatocyte transplantation for the treatment of liver diseases and ex vivo gene therapy. We hypothesized that preparative hepatic irradiation (HIR) to inhibit host hepatocellular regeneration in combination with the mitotic stimulus of host hepatocellular apoptosis should permit repopulation of the liver by transplanted cells. To test this hypothesis, congeneic normal rat hepatocytes were transplanted into UDP-glucuronosyltransferase (UGT1A1)-deficient jaundiced Gunn rats (a model of Crigler-Najjar syndrome type I), following HIR and adenovirus-mediated FasL gene transfer. Progressive repopulation of the liver by engrafted UGT1A1-proficient hepatocytes over 5 months was demonstrated by the appearance of UGT1A1 protein and enzyme activity in the liver, biliary bilirubin glucuronides secretion, and long-term normalization of serum bilirubin levels. This is the first demonstration of massive hepatic repopulation by transplanted cells by HIR and FasL-induced controlled apoptosis of host liver cells.

Construction of liver tissue in vivo with preparative partial hepatic irradiation and growth stimulus: investigations of less invasive techniques and progenitor cells

“…Although these results are very attractive, hepatectomy is too invasive to be carried out in patients. Instead of hepatectomy, Fas-mediated apoptosis of host hepatocytes (9) or administration of a recombinant adenovirus vector expressing hepatocyte growth factor (HGF) (10,11) has been successful in inducing massive repopulation of transplanted hepatocytes. However, these strategies appear difficult to implement clinically because of potential toxicity.…”

“…alone was transient and minimum (8,9). PVBL could provide a selective growth stimulus to transplanted hepatocytes in combination with HIR, resulted in massive proliferation, and significant and continuous therapeutic effects.…”

Noninvasive evaluation of liver repopulation by transplanted hepatocytes using 31P MRS imaging in mice

“…[15][16][17][18][19] HIR caused genotoxic injury, cell cycle arrest, accelerated senescence and mitotic catastrophe in host hepatocytes, providing selective proliferative advantage to transplanted nonirradiated hepatocytes in response to mitototic stimuli, leading to progressive replacement of host hepatocytes by the progeny of the engrafted cells. We report a preparative regimen consisting of partial liver irradiation with systemic administration of an adenovirus expressing human hepatocyte growth factor (HGF), followed by transplantation of CKexpressing hepatocytes into mice.…”

Liver gene therapy: advances and hurdles

“…85,89,90 In combination with a strong regenerative pressure (eg twothirds partial hepatectomy, thyroid hormone administration, ischemia-reperfusion injury or FasL gene transfer), a nearly complete repopulation of host liver by donor hepatocytes was obtained after transplantation of 0.5% of the recipient liver mass. 89,[91][92][93] Similarly, lentivirally transduced hepatocytes were massively expanded in retrorsine/partial hepatectomy-treated rats. 94 Rather than blocking hepatocyte proliferative ability, host hepatocytes were selectively depleted by Fas ligandinduced apoptosis for expanding fas-resistant donor hepatocytes.…”