title: Combined negative effect of donor age and time in culture on the reprogramming efficiency into induced pluripotent stem cells.
abstract: Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSC) by the forced expression of the transcription factors OCT4, SOX2, KLF4 and c-MYC. Pluripotent reprogramming appears as a slow and inefficient process because of genetic and epigenetic barriers of somatic cells. In this report, we have extended previous observations concerning donor age and passage number of human fibroblasts as critical determinants of the efficiency of iPSC induction. Human fibroblasts from 11 different donors of variable age were reprogrammed by ectopic expression of reprogramming factors. Although all fibroblasts gave rise to iPSC colonies, the reprogramming efficiency correlated negatively and declined rapidly with increasing donor age. In addition, the late passage fibroblasts gave less reprogrammed colonies than the early passage cell counterparts, a finding associated with the cellular senescence-induced upregulation of p21. Knockdown of p21 restored iPSC generation even in long-term passaged fibroblasts of an old donor, highlighting the central role of the p53/p21 pathway in cellular senescence induced by both donor age and culture time.
authors.affiliation: Research Programs Unit, Molecular Neurology, Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland. Electronic address: ras.trokovic@helsinki.fi.
authors.forename: Ras
authors.initials: R
authors.lastname: Trokovic
authors.affiliation: Research Programs Unit, Molecular Neurology, Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland. Electronic address: jere.weltner@helsinki.fi.
authors.forename: Jere
authors.initials: J
authors.lastname: Weltner
authors.affiliation: Institute of Biomedicine, Department of Physiology, University of Helsinki, Helsinki, Finland; School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand. Electronic address: p.noisa@sut.ac.th.
authors.forename: Parinya
authors.initials: P
authors.lastname: Noisa
authors.affiliation: Institute of Biomedicine, Department of Physiology, University of Helsinki, Helsinki, Finland; Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland. Electronic address: taneli.raivio@helsinki.fi.
authors.forename: Taneli
authors.initials: T
authors.lastname: Raivio
authors.affiliation: Research Programs Unit, Molecular Neurology, Biomedicum Stem Cell Center, University of Helsinki, Helsinki, Finland; Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland. Electronic address: timo.otonkoski@helsinki.fi.
authors.forename: Timo
authors.initials: T
authors.lastname: Otonkoski
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000369:Aged, 80 and over; D002478:Cells, Cultured; D065150:Cellular Reprogramming; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000166:cytology* / Q000378:metabolism; D007223:Infant; D007231:Infant, Newborn; D000090062:Kruppel-Like Factor 4; D008297:Male; D008875:Middle Aged; D012190:Retroviridae / Q000378:metabolism; D029082:Sendai virus / Q000378:metabolism; D013997:Time Factors; D014019:Tissue Donors; D055815:Young Adult
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; C000715467:KLF4 protein, human; D000090062:Kruppel-Like Factor 4