TGF-β2 Acts as a Context-Dependent Bidirectional Modulator at the Microglia-Neuron Crosstalk in Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a severe chronic facial pain disorder with limited therapeutic options due to unclear underlying mechanisms. Neuroinflammation within the trigeminal ganglion (TG) microenvironment is increasingly recognized as a key driver of TN pathogenesis. Neuron-microglia crosstalk has been shown to be important for the neuroinflammation environment, yet the specific ligand–receptor interactions mediating this process remain poorly defined. This study aimed to identify critical neuroimmune signaling pathways in TN and to understand the functional role of the key ligand in microglia–neuron crosstalk. We performed single-cell RNA sequencing analysis followed by in vitro functional validation. In the human trigeminal microenvironment, microglia and neurons showed the strongest ligand–receptor coupling via TGFB2–TGFBR1/TGFBR2. Notably, transforming growth factor beta‑2 (TGF‑β2) tended to be downregulated in patients with TN. Exogenous TGF-β2 (10 ng/mL) protected both microglia and neurons from lipopolysaccharide (LPS)-induced cytotoxicity and promoted an M2-like phenotype in BV2 cells, upregulating arginase-1 (Arg1), interleukin-10 (IL-10) and mannose receptor (CD206) by over 2-fold. However, combined LPS and glutamate stimulation severely blunted endogenous TGF-β2 compensatory upregulation, mirroring the dual inflammatory and excitotoxic insults in TN. While TGF-β2 restored glutamate-suppressed Arg1, IL-10 and CD206 expression, the TβRI/II inhibitor LY2109761 failed to block this restorative effect in microglia, indicating that TGF-β2 exerts its effect on microglia through non canonical pathway. Yet, it completely reversed TGF-β2-mediated suppression of neuronal calcitonin gene-related peptide (CGRP). Our findings suggested that TGF-β2 acts as a context-dependent bidirectional modulator at the microglia–neuron interface. This discovery extended the conventional view of TGF-β2 as a purely anti-inflammatory factor and provided new therapeutic insights for TN by targeting neuroinflammation and cytotoxicity.