Repopulating Activity of Ex Vivo-Expanded Murine Hematopoietic Stem Cells Resides in the CD48 super(-)c-Kit super(+)Sca-1 super(+)Lineage Marker super(-) Cell Population

• Published in: Stem cells (Dayton, Ohio) Ohio), 2008-03, Vol.26 (3), p.646-655
• Main Authors: Noda, Shinichi, Horiguchi, Kana, Ichikawa, Hitoshi, Miyoshi, Hiroyuki
• Format: Article
• Language: English
• ISSN: 1066-5099

A better understanding of the biology of cultured hematopoietic stem cells (HSCs) is required to achieve ex vivo expansion of HSCs. In this study, clonal analysis of the surface phenotype and repopulating activity of ex vivo-expanded murine HSCs was performed. After 7 days of culture with stem cell factor, thrombopoietin, fibroblast growth factor-1, and insulin-like growth factor-2, single CD34 super(-/low)c-Kit super(+)Sca-1 super(+)lineage marker super(-) (CD34 super(-)KSL) cells gave rise to various numbers of cells. The proportion of KSL cells decreased with increasing number of expanded cells. Transplantation studies revealed that the progeny containing a higher percentage of KSL cells tended to have enhanced repopulating potential. We also found that CD48 was heterogeneously expressed in the KSL cell population after culture. Repopulating activity resided only in the CD48 super(-)KSL cell population, which had a relatively long intermitotic interval. Microarray analysis showed surprisingly few differences in gene expression between cultured CD48 super(-)KSL cells (cycling HSCs) and CD48 super(+)KSL cells (cycling non-HSCs) compared with freshly isolated CD34 super(-)KSL cells (quiescent HSCs), suggesting that the maintenance of stem cell activity is controlled by a relatively small number of genes. These findings should lead to a better understanding of ex vivo-expanded HSCs. Disclosure of potential conflicts of interest is found at the end of this article.