Molecular mechanisms involved in self-renewal and pluripotency of embryonic stem cells.

Embryonic stem cells (ES cells) are derived from inner cell mass (ICM). The self-renewal and pluripotency are the main specificities of ES cells, which are likely to reveal a deeper understanding of human cellular biology and which are considered to be promising sources for cell therapy to treat patients with degenerative diseases in clinical. Growth of ES cells as a pluripotent population requires a balance between survival, proliferation, and self-renewal signals. In fact, the precise mechanism that regulates stem cell self-renewal and pluripotency remains largely unknown. Recently, in vitro and in vivo studies have identified several genetic regulators that may play important roles in the self-renewal and pluripotency process of human and mouse ES cells, including extracellular signaling factors, transcription factors, cell-cycle regulators, microRNA, genes implicated in chromosomal stability, and DNA methylation. In this review, we will summarize the currently known molecular regulators for ES cells self-renewal, and we will propose some possibilities to explain the ways in which these distinct pathways might interact. (c) 2007 Wiley-Liss, Inc.