Capacitive-resistive electric transfer (CRET) at 448 kHz is used clinically for body-contouring and tissue modulation, but most reported effects are attributed to electro-hyperthermia and manual pressure. This study asked whether the electric signal alone, at subthermal dose, can modulate early adipogenic differentiation in human adipose-derived stem cells (ADSCs). Specifically, the authors aimed to determine if short, intermittent 448 kHz stimulation alters lipid accumulation and the PPARγ/MEK regulatory axis during the first days of chemically induced adipogenesis—thereby clarifying non-thermal, mechanistic contributions relevant to Tecar/T-Plus applications.
The study used human adipose-derived stem cells (ADSCs) obtained from subcutaneous fat of four healthy adult donors (two men and two women, aged 29–69). Samples were collected under informed consent and approved by the Ethics Committee of the University Hospital Ramón y Cajal. After enzymatic digestion and cell isolation, ADSCs were cultured and expanded between passages 3–7 in growth medium before induction of adipogenic differentiation.
To trigger differentiation, cultures were incubated in a defined adipogenic medium containing high-glucose DMEM, fetal bovine serum, insulin, indomethacin, dexamethasone, and IBMX for either 2 or 9 days, with medium renewed every 3–4 days. During the final 48 hours, the cells were exposed or sham-exposed to subthermal CRET stimulation—a 448 kHz sine-wave current delivered through sterile stainless-steel electrodes connected to an INDIBA Activ HCR 902 signal generator. The current density was precisely limited to 50 µA/mm², applied in 5-minute pulses every 4 hours over the 48-hour exposure period. Temperature and CO₂ levels (37 °C, 5 % CO₂, 90 % humidity) were monitored continuously to ensure that effects were non-thermal.
After exposure, lipid accumulation was quantified by Oil Red O staining and spectrophotometry at 510 nm. Protein expression of PPARγ and phosphorylated MEK 1/2 (p-MEK 1/2) was analyzed by Western blot, using β-actin as a loading control. Immunofluorescence microscopy assessed the intracellular localization of PPARγ (nuclear vs cytoplasmic). Gene expression changes for PPARG1/2, ANGPTL4, PLIN, FABP4, SREBP1c, SCD, and FASN were measured by RT-qPCR, normalized to the housekeeping gene RPLP0. All experiments included sham-exposed controls, were repeated across multiple cell passages, and analyzed statistically using two-tailed unpaired t-tests with p < 0.05 considered significant.
Exposure of human ADSCs to subthermal 448 kHz CRET currents significantly suppressed adipogenic differentiation compared with sham controls. Quantitative Oil Red O staining revealed that lipid content decreased by ≈ 61 % after 2 days and ≈ 8 % after 9 days of differentiation (p < 0.05), confirming an early anti-adipogenic effect. Western blot analysis showed that while early exposure (day 0–2) did not alter total PPARγ levels, stimulation applied later (day 7–9) caused a 17 % reduction in PPARγ expression. Immunofluorescence confirmed that CRET reduced the proportion of cells displaying nuclear PPARγ (−42 % at 2 days; −67 % at 9 days) and shifted the protein toward cytoplasmic localization, effectively deactivating its transcriptional role.
Concurrently, CRET induced an increase in phosphorylated MEK1/2 (p-MEK)—12 % higher at 2 days and 21 % higher at 9 days—suggesting activation of the MAPK–ERK signaling pathway that drives PPARγ export from the nucleus. Gene-expression analysis by RT-qPCR supported this molecular cascade: PPARG1 mRNA decreased by 9 %, and downstream targets essential to lipid synthesis and storage—perilipin (−18 %), angiopoietin-like 4 (−20 %), and fatty-acid synthase (−11 %)—were all significantly down-regulated after 9 days. Other lipid-metabolism genes (FABP4, SCD, SREBP1c) remained largely unchanged. Together, these results demonstrate that even in the absence of heating or mechanical pressure, electrical stimulation at 448 kHz reprograms early stem-cell signaling, blunting fat-cell formation by modulating both protein activation and adipogenic gene expression.
This study demonstrated that subthermal 448 kHz capacitive-resistive electric transfer (CRET) stimulation can independently modulate human adipose-derived stem-cell behavior without the need for accompanying heat or mechanical pressure. Specifically, it inhibited early adipogenic differentiation by activating MEK1/2 signaling, which in turn caused PPARγ inactivation and cytoplasmic translocation, leading to the downregulation of key lipogenic genes (PPARG1, perilipin, ANGPTL4, and FASN). These cellular and molecular effects collectively reduce lipid synthesis and storage during the initial stages of adipocyte formation.
The findings identify a non-thermal, bioelectrical mechanism through which 448 kHz stimulation influences metabolic and regenerative processes at the cellular level. The authors suggest that this electro-modulatory action likely complements the thermal and mechanical components of full clinical Tecar therapy, helping explain its fat-modulating and tissue-regenerative outcomes observed in vivo. In short, the electric current itself—apart from heat—can alter stem-cell differentiation pathways, providing a deeper scientific rationale for Tecar’s therapeutic efficacy in body-contouring and recovery contexts.
