Characterization of Senescence-Associated Secretory Profile of iPSC Derived Fibroblasts

Objective: Replicative senescence shortens the lifespan of mammalian cells and limits their potential for regenerative therapies.  Senescent cells secrete factors, known as senescence-associated secretory phenotype (SASP), that are linked to loss of growth potential.  We have recently generated fibroblasts with improved biological potency from human embryonic stem cells (EDK6) and induced pluripotent stem cells (iPDK2). However, it is not known if iPDK cells acquire an increased proliferative lifespan when compared to the fibroblasts from which they were reprogrammed.  The goal of this study was to compare SASP profiles between hESC- and iPSC-derived fibroblasts by comparing them to the parental fibroblasts (BJ) from which iPSC were derived.

Method: Replicative senescence of EDK6, iPDK2 and BJ fibroblasts was induced by serial passaging of these cells over three months. RNA was extracted from early (p8) and late (p19-20) passaged cells and relative levels of gene expression for SASP including IL-8, IL-6, IGF-1, HGF, and VEGF were determined by RT-PCR.

Result: In vitro replicative capacity of EDK6, iPDK2 and BJ fibroblasts was assessed by calculating the number of population doublings (PDs) during serial subculture. While a decline in PDs of EDK6 and iPDK2 was observed at p19, BJ underwent an earlier decrease in PDs (p13).  As assessed by RT-PCR, levels of SASP RNA expression increased with passage number in EDK and iPDK, while a decrease in SASP RNA expression was seen with increasing passage of BJ fibroblasts.

Conclusion: These results demonstrate prolonged growth potential and stable secretory profile of EDK6 and iPDK2 when compared to BJ.  This indicates that fibroblasts derived from iPSC may acquire replicative properties that exceed those of the somatic cells from which they were derived.  The sustained growth potential and secretory microenvironment of iPSC-derived fibroblasts demonstrate that these cells may have applications for future regenerative therapies.