Resveratrol targeting Smad4 via a concentration-dependent biphasic effect regulates stem cells-mediated regeneration

Resveratrol (RSV), a globally utilized nutraceutical compound, is primarily recognized for its human health benefits, contributing to its widespread and often unregulated use in daily life and clinical settings. However, its influence on cellular stemness remains poorly understood. While numerous reports suggest anti-tumor properties, systematic and robust evidence is lacking. This study employed high-throughput RNA sequencing, RNA interference, RT-qPCR, and whole-mount in situ hybridization, and used the planarian Dugesia japonica as a stem cell model, aiming to investigate the effects of varying RSV concentrations on blastema regeneration following amputation and analyze the associated mechanism. We demonstrated a biphasic effect of RSV on anterior blastema regeneration: low-concentration RSV (5 μM) promoted regeneration, whereas high-concentration RSV (50 μM) caused significant inhibition. RNA-seq identified Smad4 as a key mediator; its inhibition exacerbated the regenerative deficit under low concentration. Intriguingly, PiwiA expression increased in the anterior blastema at both RSV concentrations, most notably at low concentration condition. Conversely, the late stem cell marker Agat1 was significantly suppressed by high-concentration RSV. These findings indicated that RSV promoted stem cell proliferation. Critically, low-concentration RSV enhanced both proliferation and differentiation, while high-concentration RSV inhibited differentiation independently of Smad4. This study provided the first in vivo evidence at the whole-organism level that RSV concentration dictated divergent stem cell differentiation fates, offering a scientific basis for its rational evaluation and application.