Evaluation of the Immunomodulatory Effects of All-Trans Retinoic Acid Solid Lipid Nanoparticles and Human Mesenchymal Stem Cells in an A549 Epithelial Cell Line Model.

<p><strong>PURPOSE:</strong> To investigate two potential strategies aimed at targeting the inflammatory pathogenesis of COPD: a small molecule, all trans retinoic acid (atRA) and human mesenchymal stem cells (hMSCs).</p> <p><strong>METHODS:</strong> atRA was formulated into solid lipid nanoparticles (SLNs) via the emulsification-ultrasonication method, and these SLNs were characterised physicochemically. Assessment of the immunomodulatory effects of atRA-SLNs on A549 cells in vitro was determined using ELISA. hMSCs were suspended in a previously developed methylcellulose, collagen and beta-glycerophosphate hydrogel prior to investigating their immunomodulatory effects in vitro.</p> <p><strong>RESULTS:</strong> SLNs provided significant encapsulation of atRA and also sustained its release over 72 h. A549 cells were viable following the addition of atRA SLNs and showed a reduction in IL-6 and IL-8 levels. A549 cells also remained viable following addition of the hMSC/hydrogel formulation - however, this formulation resulted in increased levels of IL-6 and IL-8, indicating a potentially pro-inflammatory effect.</p> <p><strong>CONCLUSION:</strong> Both atRA SLNs and hMSCs show potential for modulating the environment in inflammatory disease, though through different mechanisms and leading to different outcomes - despite both being explored as strategies for use in inflammatory disease. atRA shows promise by acting in a directly anti-inflammatory manner, whereas further research into the exact mechanisms and behaviours of hMSCs in inflammatory diseases is required.</p>