Piezo2 mechanosensitive ion channel is located to sensory neurons and non-neuronal cells in rat peripheral sensory pathway: implications in pain

Piezo2 mechanotransduction channel is a crucial mediator of sensory neurons for sensing and transducing touch, vibration, and proprioception. We here characterized Piezo2 expression and cell specificity in rat peripheral sensory pathway using a validated Piezo2 antibody. Immunohistochemistry using this antibody revealed Piezo2 expression in pan primary sensory neurons (PSNs) of dorsal rood ganglia (DRG) in normal rats, which was actively transported along afferent axons to both central presynaptic terminals innervating the spinal dorsal horn (DH) and peripheral afferent terminals in skin. Piezo2 immunoreactivity (IR) was also detected in the postsynaptic neurons of the DH and in the motor neurons of the ventral horn, but not in spinal GFAP- and Iba1-positive glia. Notably, Piezo2-IR was clearly identified in peripheral non-neuronal cells, including perineuronal glia, Schwann cells in the sciatic nerve and surrounding cutaneous afferent endings, as well as in skin epidermal Merkel cells and melanocytes. Immunoblots showed increased Piezo2 in DRG ipsilateral to plantar injection of complete Freund adjuvant (CFA), and immunostaining revealed increased Piezo2-IR intensity in the DH ipsilateral to CFA injection. This elevation of DH Piezo2-IR was also evident in various neuropathic pain models and monosodium iodoacetate (MIA) knee osteoarthritis (OA) pain model, compared to controls. We conclude that 1) the pan neuronal profile of Piezo2 expression suggests that Piezo2 may function extend beyond simply touch/proprioception mediated by large-sized low-threshold mechanosensitive PSNs, 2) Piezo2 may have functional roles involving sensory processing in spinal cord, Schwann cells, and skin melanocytes, and 3) aberrant Piezo2 expression may contribute pain pathogenesis.