title: Human side population keratinocytes exhibit long-term proliferative potential and a specific gene expression profile and can form a pluristratified epidermis.
abstract: The aim of the present study was to characterize human side population (SP) epidermal keratinocytes isolated from primary cell cultures. For that purpose, keratinocytes were isolated from normal adult breast skin samples and the Hoechst 33342 exclusion assay described for hematopoietic cells was adapted to keratinocytes. Three types of keratinocytes were studied: the SP, the main population (MP), and the unsorted initial population. SP keratinocytes represented 0.16% of the total population. In short-term cultures, they exhibited an increased colony-forming efficiency and produced more actively growing colonies than did unsorted and MP keratinocytes. In long-term cultures, SP cells exhibited an extensive expansion potential, performing a mean of 44 population doublings for up to 12 successive passages after cell sorting. Moreover, even in long-term cultures, SP keratinocytes were able to form a pluristratified epidermis when seeded on a dermal substrate. Unsorted and MP keratinocytes promoted a reduced expansion: mean values of 14 population doublings for five passages and 12 population doublings for four successive passages, respectively. To further characterize SP cells, cDNA microarrays were used to identify their molecular signature. Transcriptome profiling showed that 41 genes were differentially expressed in SP (vs. MP) cells, with 37 upregulated genes and only four downregulated genes in SP cells. The majority of these genes were functionally related to the regulation of transcription and cell signaling. In conclusion, SP human keratinocytes isolated from primary cultures exhibited both short- and long-term high proliferative potential, formed a pluristratified epidermis, and were characterized by a specific gene expression profile.
authors.affiliation: Service de Génomique Fonctionnelle, CEA, Evry, France.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Larderet
authors.forename: Nicolas O
authors.initials: NO
authors.lastname: Fortunel
authors.forename: Pierre
authors.initials: P
authors.lastname: Vaigot
authors.forename: Marine
authors.initials: M
authors.lastname: Cegalerba
authors.forename: Peggy
authors.initials: P
authors.lastname: Maltère
authors.forename: Olivia
authors.initials: O
authors.lastname: Zobiri
authors.forename: Xavier
authors.initials: X
authors.lastname: Gidrol
authors.forename: Gilles
authors.initials: G
authors.lastname: Waksman
authors.forename: Michèle T
authors.initials: MT
authors.lastname: Martin
mesh_terms: D000328:Adult; D002454:Cell Differentiation; D049109:Cell Proliferation; D002469:Cell Separation; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D066298:In Vitro Techniques; D015603:Keratinocytes / Q000145:classification / Q000166:cytology* / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D013234:Stem Cells / Q000145:classification / Q000166:cytology* / Q000378:metabolism*; D013997:Time Factors