文摘
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 p16INK4a signaling in hSKP senescence. Examination of cyclin-dependent kinase inhibitors revealed the involvement of p15INK4b and p27KIP1. 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, p15INK4b and p27KIP1 effectively inhibited hSKP senescence and promoted hSKP proliferation. The unique senescent phenotype of human dermal stem cells and the role of Akt-FOXO3-p27KIP1/p15INK4b 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.