Selective repopulation of normal mouse liver by Fas/CD95-resistant hepatocytes

Abstract

Hepatocyte transplantation might represent a potential therapeutic alternative to liver transplantation in the future; however, transplanted cells have a limited capacity to repopulate the liver, as they do not proliferate under normal conditions. Recently, studies in urokinase (uPA) transgenic mice and in fumarylacetoacetate hydrolase (FAH)-deficient mice have shown that the liver can be repopulated by genetically engineered hepatocytes harboring a selective advantage over resident hepatocytes. We have reported that transgenic mice expressing human Bcl-2 in their hepatocytes are protected from Fas/CD95-mediated liver apoptosis. We now show that Bcl-2 transplanted hepatocytes selectively repopulate the liver of mice treated with nonlethal doses of the anti-Fas antibody Jo2. FK 506 immunosuppressed mice were transplanted by splenic injection with Bcl-2 hepatocytes. The livers of female recipients were repopulated by male Bcl-2 transgenic hepatocytes, as much as 16%, after 8 to 12 administrations of Jo2. This only occurred after anti-Fas treatment, confirming that resistance to Fas-induced apoptosis constituted the selective advantage of these transplanted hepatocytes. Thus, we have demonstrated a method for increasing genetic reconstitution of the liver through selective repopulation with modified transgenic hepatocytes, which will allow optimization of cell and gene therapy in the liver.

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

“…The agonistic antibody (Jo-mab) has been employed to augment hepatic repopulation. 8,22,23 In these studies, engrafted bcl-2-expressing donor hepatocytes were protected from Jo-mab-induced apoptosis and resulted in up to 15-20% repopulation of the host liver by repeated injections of an agonistic anti-Fas antibody. Although the bcl-2-protection approach is scientifically interesting, constant expression of bcl-2 from an integrated gene would be associated with long-term cancer risk.…”

“…Other investigators have used an activating Fas antibody to induce apoptosis in host liver cells, followed by the transplantation of hepatocytes from Bcl-2 transgenic mice, that were protected against the activating antibody. 8 To develop a more generally applicable system, normal rat hepatocytes were transplanted into Nagase analbuminemic rats that were subjected to partial hepatectomy (PH) and treated with retrorsine to inhibit host hepatocyte proliferation. This resulted in significant correction of the albumin deficiency.…”

Liver gene therapy: advances and hurdles

“…94 Rather than blocking hepatocyte proliferative ability, host hepatocytes were selectively depleted by Fas ligandinduced apoptosis for expanding fas-resistant donor hepatocytes. 95,96 Interestingly, hepatocytes deficient for p27Kip1, an inhibitor of the cell cycle, had enhanced growth potential and repopulated host liver better than normal hepatocytes. This result showed that engineering donor hepatocytes that have a enhanced growth ability would also be an effective strategy for liver repopulation.…”

Basal c-Jun NH2-terminal protein kinase activity is essential for survival and proliferation of T-cell acute lymphoblastic leukemia cells

“…Several studies have shown that dysregulated expression of the oncoprotein c-Myc is critical for the development of T-ALL (26,27), whereas the protein level of Bcl-2 determines the sensitivity to Fas-mediated apoptosis in various types of cells (28,29). JNK activity has been shown to regulate the protein levels of c-Myc and Bcl-2 family members in certain cell context (3,10,11,30).…”