Liu Shuang, Wang Xinyue, Zhao Qian, Liu Shu, Zhang Huishan, Shi Junchao, Li Na, Lei Xiaohua, Zhao Huashan, Deng Zhili, Cao Yujing, Ning Lina, Xia Guoliang, Duan Enkui
State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, China.
Cell Mol Life Sci. 2015 Aug;72(15):2949-60. doi: 10.1007/s00018-015-1877-3. Epub 2015 Mar 10.
Multipotent skin-derived precursors (SKPs) are dermal stem cells with the capacity to reconstitute the dermis and other tissues, such as muscles and the nervous system. Thus, the easily available human SKPs (hSKPs) hold great promises in regenerative medicine. However, long-term expansion is difficult for hSKPs in vitro. We previously demonstrated that hSKPs senesced quickly under routine culture conditions. To identify the underlying mechanisms so as to find an effective way to expand hSKPs, time-dependent microarray analysis of gene expression in hSKPs during in vitro culture was performed. We found that the senescence of hSKPs had a unique gene expression pattern that differs from reported typical senescence. Subsequent investigation ruled out the role of DNA damage and classical p53 and p16(INK4a) signaling in hSKP senescence. Examination of cyclin-dependent kinase inhibitors revealed the involvement of p15(INK4b) and p27(KIP1). Further exploration about upstream signals indicated the contribution of Akt hypo-activity and FOXO3 to hSKP senescence. Forced activation of Akt and knockdown of FOXO3, p15(INK4b) and p27(KIP1) effectively inhibited hSKP senescence and promoted hSKP proliferation. The unique senescent phenotype of human dermal stem cells and the role of Akt-FOXO3-p27(KIP1)/p15(INK4b) signaling in regulating hSKP senescence provide novel insights into the senescence and self-renewal regulation of adult stem cells. The present study also points out a way to propagate hSKPs in vitro so as to fulfill their promises in regenerative medicine.
多能皮肤衍生前体细胞（SKP）是具有重建真皮及其他组织（如肌肉和神经系统）能力的真皮干细胞。因此，易于获取的人SKP（hSKP）在再生医学中具有巨大潜力。然而，hSKP在体外进行长期扩增很困难。我们之前证明hSKP在常规培养条件下会迅速衰老。为了确定其潜在机制以便找到扩增hSKP的有效方法，我们对体外培养的hSKP进行了基因表达的时间依赖性微阵列分析。我们发现hSKP的衰老具有独特的基因表达模式，不同于已报道的典型衰老。后续研究排除了DNA损伤以及经典的p53和p16（INK4a）信号通路在hSKP衰老中的作用。对细胞周期蛋白依赖性激酶抑制剂的检测揭示了p15（INK4b）和p27（KIP1）的参与。对上游信号的进一步探索表明Akt活性降低和FOXO3对hSKP衰老有影响。强制激活Akt以及敲低FOXO3、p15（INK4b）和p27（KIP1）可有效抑制hSKP衰老并促进hSKP增殖。人真皮干细胞独特的衰老表型以及Akt - FOXO3 - p27（KIP1）/p15（INK4b）信号通路在调节hSKP衰老中的作用为成体干细胞的衰老和自我更新调控提供了新的见解。本研究还指出了一种在体外扩增hSKP的方法，以便在再生医学中实现其潜力。
