The CD44+ALDH+ Population of Human Keratinocytes Is Enriched for Epidermal Stem Cells with Long-Term Repopulating Ability§

Authors

  • Akos Z. Szabo,

    1. Department of Dermatology, University of California San Francisco and Veteran Affairs Medical Center, Dermatology Service, San Francisco, California, USA
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  • Stephen Fong,

    1. Department of Dermatology, University of California San Francisco and Veteran Affairs Medical Center, Dermatology Service, San Francisco, California, USA
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  • Lili Yue,

    1. Department of Dermatology, University of California San Francisco and Veteran Affairs Medical Center, Dermatology Service, San Francisco, California, USA
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  • Kai Zhang,

    1. Department of Dermatology, University of California San Francisco and Veteran Affairs Medical Center, Dermatology Service, San Francisco, California, USA
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  • Lauren R. Strachan,

    1. Department of Dermatology, University of California San Francisco and Veteran Affairs Medical Center, Dermatology Service, San Francisco, California, USA
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  • Kenneth Scalapino,

    1. Department of Medicine, University of California San Francisco and Veterans Affairs Medical Center, Medical Service, Arthritis Division, San Francisco, California, USA
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  • Maria Laura Mancianti,

    1. Department of Pathology, Alta Bates Medical Center, Berkeley, California, USA
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  • Ruby Ghadially

    Corresponding author
    1. Department of Dermatology, University of California San Francisco and Veteran Affairs Medical Center, Dermatology Service, San Francisco, California, USA
    • Department of Dermatology, University of California, San Francisco, Epithelial Section, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, 4150 Clement Street MC190, San Francisco, California 94121, USA
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    • Telephone: 415-221-4810x3373; Fax: 415-750-6959


  • Author contributions: A.S.: conception and design, data collection and/or assembly, data analysis and interpretation, and manuscript writing; S.F. data collection and/or assembly and data analysis and interpretation; K.Z. and K.S.: conception and design and data collection and/or assembly; L.R.S.: conception and design and data analysis and interpretation; L.Y.: data analysis and interpretation; M.L.M.: manuscript writing and data analysis and interpretation; R.G.: conception and design, data analysis and interpretation, and manuscript writing. A.S. and S.F. contributed equally to this article.

  • Disclosure of potential conflicts of interest is found at the end of this article.

  • §

    First published online in STEM CELLS EXPRESS January 17, 2013.

Abstract

Like for other somatic tissues, isolation of a pure population of stem cells has been a primary goal in epidermal biology. We isolated discrete populations of freshly obtained human neonatal keratinocytes (HNKs) using previously untested candidate stem cell markers aldehyde dehydrogenase (ALDH) and CD44 as well as the previously studied combination of integrin α6 and CD71. An in vivo transplantation assay combined with limiting dilution analysis was used to quantify enrichment for long-term repopulating cells in the isolated populations. The ALDH+CD44+ population was enriched 12.6-fold for long-term repopulating epidermal stem cells (EpiSCs) and the integrin α6hiCD71lo population was enriched 5.6-fold, over unfractionated cells. In addition to long-term repopulation, CD44+ALDH+ keratinocytes exhibited other stem cell properties. CD44+ALDH+ keratinocytes had self-renewal ability, demonstrated by increased numbers of cells expressing nuclear Bmi-1, serial transplantation of CD44+ALDH+ cells, and holoclone formation in vitro. CD44+ALDH+ cells were multipotent, producing greater numbers of hair follicle-like structures than CD44ALDH cells. Furthermore, 58% ± 7% of CD44+ALDH+ cells exhibited label-retention. In vitro, CD44+ALDH+ cells showed enhanced colony formation, in both keratinocyte and embryonic stem cell growth media. In summary, the CD44+ALDH+ population exhibits stem cell properties including long-term epidermal regeneration, multipotency, label retention, and holoclone formation. This study shows that it is possible to quantify the relative number of EpiSCs in human keratinocyte populations using long-term repopulation as a functional test of stem cell nature. Future studies will combine isolation strategies as dictated by the results of quantitative transplantation assays, in order to achieve a nearly pure population of EpiSCs. STEM CELLS 2013;31:786–799

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