BACKGROUND & AIMS: The availability of in vitro expandable human hepatocytes would greatly advance liver-directed cell therapies. Therefore, we examined whether human fetal hepatocytes are amenable to telomerase-mediated immortalization without inducing a transformed phenotype and disrupting their differentiation potential. Telomerase is a ribonucleoprotein that plays a pivotal role in maintaining telomere length and chromosome stability. Human somatic cells, including hepatocytes, exhibit no telomerase activity. Consequently, their telomeres progressively shorten with each cell cycle until critically short telomeres trigger replicative senescence. METHODS: The catalytic subunit, telomerase reverse transcriptase, was expressed in human fetal hepatocytes. Transduced cells were characterized for telomerase activity, telomere length, proliferative capacity, hepatocellular functions, oncogenicity, and their in vivo maturation potential. RESULTS: The expression of human telomerase reverse transcriptase restored telomerase activity in human fetal hepatocytes. Telomerase-reconstituted cells were capable of preserving elongated telomeres, propagated in culture beyond replicative senescence for more than 300 cell doublings (to date), and maintained their liver-specific nature, as analyzed by a panel of hepatic growth factors, growth factor receptors, and transcription factors as well as albumin, glucose-6-phosphatase, glycogen synthesis, cytochrome P450 (CYP) expression profiles, and urea production. Moreover, the immortalized cells exhibited no oncogenicity, and no up-regulation of c-Myc was detected. The cells engrafted and survived in the liver of immunodeficient mice with hepatocellular gene expression. CONCLUSIONS: Reconstitution of telomerase activity induces indefinite replication in human fetal hepatocytes and offers unique opportunities for examining basic biologic mechanisms and for considering development of stable cell lines for liver-directed therapies.
BACKGROUND & AIMS: The availability of in vitro expandable human hepatocytes would greatly advance liver-directed cell therapies. Therefore, we examined whether human fetal hepatocytes are amenable to telomerase-mediated immortalization without inducing a transformed phenotype and disrupting their differentiation potential. Telomerase is a ribonucleoprotein that plays a pivotal role in maintaining telomere length and chromosome stability. Human somatic cells, including hepatocytes, exhibit no telomerase activity. Consequently, their telomeres progressively shorten with each cell cycle until critically short telomeres trigger replicative senescence. METHODS: The catalytic subunit, telomerase reverse transcriptase, was expressed in human fetal hepatocytes. Transduced cells were characterized for telomerase activity, telomere length, proliferative capacity, hepatocellular functions, oncogenicity, and their in vivo maturation potential. RESULTS: The expression of human telomerase reverse transcriptase restored telomerase activity in human fetal hepatocytes. Telomerase-reconstituted cells were capable of preserving elongated telomeres, propagated in culture beyond replicative senescence for more than 300 cell doublings (to date), and maintained their liver-specific nature, as analyzed by a panel of hepatic growth factors, growth factor receptors, and transcription factors as well as albumin, glucose-6-phosphatase, glycogen synthesis, cytochrome P450 (CYP) expression profiles, and urea production. Moreover, the immortalized cells exhibited no oncogenicity, and no up-regulation of c-Myc was detected. The cells engrafted and survived in the liver of immunodeficientmice with hepatocellular gene expression. CONCLUSIONS: Reconstitution of telomerase activity induces indefinite replication in human fetal hepatocytes and offers unique opportunities for examining basic biologic mechanisms and for considering development of stable cell lines for liver-directed therapies.
Authors: Kristoffer Weber; Michael Thomaschewski; Michael Warlich; Tassilo Volz; Kerstin Cornils; Birte Niebuhr; Maike Täger; Marc Lütgehetmann; Jörg-Matthias Pollok; Carol Stocking; Maura Dandri; Daniel Benten; Boris Fehse Journal: Nat Med Date: 2011-03-27 Impact factor: 53.440
Authors: Tanja Deurholt; Niek P van Til; Aniska A Chhatta; Lysbeth ten Bloemendaal; Ruth Schwartlander; Catherine Payne; John N Plevris; Igor M Sauer; Robert Afm Chamuleau; Ronald Pj Oude Elferink; Jurgen Seppen; Ruurdtje Hoekstra Journal: BMC Biotechnol Date: 2009-10-21 Impact factor: 2.563