Thermo-Magnetic Induction of Pro-Inflammatory Microglia: A Lipid-Based Nanovector Strategy for Glioblastoma...

Microglia, the main immune cells in the central nervous system (CNS), maintain physiological homeostasis and react to pathological changes. Besides their neuroprotective function, they play a crucial role in brain tumor microenvironments such as glioblastoma (GBM), by composing up 40% of the tumor mass. Glioma-associated microglia exhibit a dynamic activation state characterized mainly by an immunosuppressive (M2-like) response, with a lesser contribution of pro-inflammatory (M1-like) response. Modulating microglial into M1-like phenotype offers antitumor response and a promising immunotherapy strategy against GBM. Nanoparticles can induce microglial polarization, also modulating pro-inflammatory responses for tumor suppression. Magnetically responsive nanoparticles are promising nanotransducers due to their remote-control capabilities via external magnetic fields, enabling precise therapeutic interventions. This study proposes a novel strategy that exploits lipid-based magnetic nanovectors (LMNVs) composed of a lipid matrix doped with iron oxide nanoparticles to induce M1-like microglial response through magneto-thermal conversion. Results demonstrated that LMNVs exhibit excellent biocompatibility and efficient internalization within human microglia (HMC3 cells). Upon alternating magnetic field (AMF) stimulation, LMNVs triggered a sustained increase in intracellular Ca²⁺ levels, leading to the polarization of microglia toward a pro-inflammatory M1-like phenotype. This activation was confirmed by the upregulation of key inflammatory markers (CD40, CD86) and cytokine release (IL-6, IL-8, and TNF-α), mirroring the effects of IFN-γ stimulation. These findings were further corroborated by comparative transcriptomic analysis. Notably, conditioned medium from LMNVs + AMF-stimulated microglia significantly impaired the viability and proliferation of both immortalized and patient-derived GBM cells, demonstrating a potent antitumor response. The tumor cell death was associated with immunogenic cell death (ICD), as indicated by the translocation of the damage-associated molecular patterns, in particular high mobility group box 1 (HMGB1) and calreticulin (CRT). Overall, these results highlight the potential of LMNVs as a remotely activatable nanoplatform capable of reprogramming microglia and to promote antitumor immunity in GBM.