Salvianolic Acid B Maintained Stem Cell Pluripotency and Increased Proliferation Rate by Activating Jak2–Stat3 Combined with EGFR–Erk1/2 Pathways

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are considered the most powerful in terms of differentiating into three-germ-layer cells. However, maintaining self-renewing ESCs and iPSCs in vitro requires leukemia-induced factor (LIF), an expensive reagent. Here we describe a less expensive compound that may serve as a LIF substitute—salvianolic acid B (Sal B), a Salvia miltiorrhiza extract. We found that Sal B is capable of upregulating Oct4 and Sox2, two genes considered important for the maintenance of ESC pluripotency. Our MTT data indicate that instead of triggering cell death, Sal B induced cell proliferation, especially at optimum concentrations of 0.01 nM and 0.1 nM. Other results indicate that compared to non-LIF controls, Sal B-treated ESCs expressed higher levels of several stem cell markers while still maintaining differentiation into three-germ-layer cells after six passages. Further, we found that Sal B triggers the Jak2–Stat3 and EGFR–ERK1/2 signaling pathways. Following Sal B treatment, (a) levels of phosphorylated (p)-Jak2, p-Stat3, p-EGFR, and p-ERK proteins all increased; (b) these increases were suppressed by AG490 (a Jak2 inhibitor) and ZD1839 (an EGFR inhibitor); and (c) cytokines associated with the Jak2–Stat3 signaling pathway were upregulated. Our findings suggest that Sal B can be used as a LIF replacement for maintaining ESC pluripotency while increasing cell proliferation.