Low-Intensity Pulsed Ultrasound Promotes a Treg-Like Phenotype and Suppresses a Th17-Like Phenotype in CD4+ T Cells via YAP/TAZ Activation in vitro.

Introduction: CD4⁺ T cell subpopulations, particularly T helper 17 (Th17) and regulatory T (Treg) cells, exhibit antagonistic functions and play essential roles in inflammatory responses. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are critical modulators of cell proliferation and differentiation. Low-intensity pulsed ultrasound (LIPUS) has been shown to regulate YAP/TAZ activity, but its role in Th17/Treg balance remains unclear.

Methods: CD4⁺ T cells were purified from rat peripheral blood mononuclear cells (PBMCs) using magnetic-activated cell sorting (MACS). The cells were then treated with low-intensity pulsed ultrasound (LIPUS) at a set of parameters (1.0 MHz, 20 mW/cm², 20% duty cycle, 2h/day for 3 days) optimized based on preliminary proliferation and apoptosis assays. The effects of LIPUS on the expression of key functional markers (Foxp3 for Treg-like cells and IL-17A for Th17-like cells) were evaluated by flow cytometry, quantitative PCR, and ELISA. The activation and subcellular localization of YAP/TAZ were examined using immunofluorescence staining. Furthermore, siRNA-mediated knockdown was performed to investigate the functional involvement of YAP/TAZ in the LIPUS-mediated effects.

Results: LIPUS treatment significantly increased the frequency of Foxp3-expressing cells while decreasing the frequency of IL-17A-producing cells. Additionally, LIPUS promoted the activation and nuclear translocation of YAP and TAZ, as evidenced by enhanced protein expression and a shift in subcellular localization. siRNA-mediated knockdown of YAP/TAZ attenuated the LIPUS-induced increase in Foxp3⁺ cells and potentiated the population of IL-17A⁺ cells. Importantly, LIPUS treatment effectively rescued the expression patterns of these functional markers following YAP/TAZ inhibition.

Discussion: Our findings demonstrate that LIPUS promotes a Treg-like phenotype and suppresses a Th17-like phenotype in CD4⁺ T cells, a process that is mediated, at least in part, by the activation of the YAP/TAZ signaling pathway. This immunomodulatory effect suggests that LIPUS could be explored as a novel non-invasive strategy for managing autoimmune diseases and chronic inflammatory conditions associated with an imbalance in T cell responses.