title: Direct transdifferentiation of spermatogonial stem cells to morphological, phenotypic and functional hepatocyte-like cells via the ERK1/2 and Smad2/3 signaling pathways and the inactivation of cyclin A, cyclin B and cyclin E.
abstract: BACKGROUND
  Severe shortage of liver donors and hepatocytes highlights urgent requirement of extra-liver and stem cell source of hepatocytes for treating liver-related diseases. Here we hypothesized that spermatogonial stem cells (SSCs) can directly transdifferentiate to hepatic stem-like cells capable of differentiating into mature hepatocyte-like cells in vitro without an intervening pluripotent state.
  
  
  RESULTS
  SSCs first changed into hepatic stem-like cells since they resembled hepatic oval cells in morphology and expressed Ck8, Ck18, Ck7, Ck19, OV6, and albumin. Importantly, they co-expressed CK8 and CK19 but not ES cell markers. Hepatic stem-like cells derived from SSCs could differentiate into small hepatocytes based upon their morphological features and expression of numerous hepatic cell markers but lacking of bile epithelial cell hallmarks. Small hepatocytes were further coaxed to differentiate into mature hepatocyte-like cells, as identified by their morphological traits and strong expression of Ck8, Ck18, Cyp7a1, Hnf3b, Alb, Tat, Ttr, albumin, and CYP1A2 but not Ck7 or CK19. Notably, these differentiated cells acquired functional attributes of hepatocyte-like cells because they secreted albumin, synthesized urea, and uptake and released indocyanine green. Moreover, phosphorylation of ERK1/2 and Smad2/3 rather than Akt was activated in hepatic stem cells and mature hepatocytes. Additionally, cyclin A, cyclin B and cyclin E transcripts and proteins but not cyclin D1 or CDK1 and CDK2 transcripts or proteins were reduced in mature hepatocyte-like cells or hepatic stem-like cells derived from SSCs compared to SSCs.
  
  
  CONCLUSIONS
  SSCs can transdifferentiate to hepatic stem-like cells capable of differentiating into cells with morphological, phenotypic and functional characteristics of mature hepatocytes via the activation of ERK1/2 and Smad2/3 signaling pathways and the inactivation of cyclin A, cyclin B and cyclin E. This study thus provides an invaluable source of mature hepatocytes for treating liver-related diseases and drug toxicity screening and offers novel insights into mechanisms of liver development and cell reprogramming.
authors.affiliation: Renji Hospital, Stem Cell Research Center, Shanghai Jiao Tong University School of Medicine, 1630 Dongfang Road, Shanghai 200127, China. zupinghe@sjtu.edu.cn.
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Zhang
authors.forename: Yuehua
authors.initials: Y
authors.lastname: Gong
authors.forename: Ying
authors.initials: Y
authors.lastname: Guo
authors.forename: Yanan
authors.initials: Y
authors.lastname: Hai
authors.forename: Hao
authors.initials: H
authors.lastname: Yang
authors.forename: Shi
authors.initials: S
authors.lastname: Yang
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Meng
authors.initials: M
authors.lastname: Ma
authors.forename: Linhong
authors.initials: L
authors.lastname: Liu
authors.forename: Zheng
authors.initials: Z
authors.lastname: Li
authors.forename: Wei-Qiang
authors.initials: WQ
authors.lastname: Gao
authors.forename: Zuping
authors.initials: Z
authors.lastname: He
mesh_terms: D000418:Albumins / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D002478:Cells, Cultured; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology* / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010641:Phenotype; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D013093:Spermatogonia / Q000166:cytology* / Q000378:metabolism*; D013234:Stem Cells
chemical_list: D000418:Albumins; D019925:Cyclin A; D019926:Cyclin B; D019927:Cyclin E; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse
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