Periodic thermomechanical modulation of toll-like receptor expression and distribution in mesenchymal stromal cells

This study investigated whether periodic thermomechanical cues can modulate antiviral toll-like receptor (TLR) expression and subcellular localization in human adipose-derived mesenchymal stromal cells (MSCs), with emphasis on SARS-CoV-2-associated sensors TLR4 (surface) and TLR7 (intracellular). Using thermally controlled, programmable shape-memory polymer (cPCLBA) actuator sheets as culture substrates, the authors compared untreated controls, thermal-only cycling, mechanical-only cycling, and combined thermomechanical stimulation. Flow cytometry showed that periodic stimulation selectively increased the proportion of MSCs co-expressing TLR4 and TLR7 and increased the fraction of IFN-α1-positive cells. Super-resolution confocal imaging demonstrated increased recruitment/colocalization of TLR4 and TLR7 within endoplasmic reticulum (ER) regions, with ~85% of ER-localized TLR7 colocalizing with TLR4. Mechanistically, thermomechanical stimulation increased F-actin assembly and increased F-actin-colocalized TLR4 and TLR7; inhibition of myosin light chain kinase (MLCK) with ML7 abrogated these effects, implicating myosin-mediated actin remodeling in TLR redistribution. The findings suggest thermomechanical preconditioning as a route to tune MSC innate immune sensing relevant to antiviral responses.