Accepted

Central post stroke pain (CPSP) is an intractable neuropathic pain syndrome that occurs after the acute focal lesion of the central nervous system (CNS) due to a cerebrovascular cause. Epoxyeicosatrienoic acids (EETs) exert many pharmacological effects in vivo and in vitro, such as anti-apoptosis, anti-inflammatory, and anti-oxidative stress. Neuroinflammation and apoptosis are the potential pathophysiological mechanisms of neuropathic pain. This study aimed to investigate whether 14,15-EET has an antinociception effect on CPSP rats through its anti-inflammation and anti-apoptosis mechanisms. Rats were treated with type IV collagenase (CPSP group) or saline (Sham group) via injection with a Hamilton syringe into the ventral posterior lateral nucleus (VPL) according to the stereotaxic coordinates. We first tested the mechanical withdrawal threshold, as well as neuroinflammation- and apoptosis-related protein expressions in the per-lesion site of CPSP and Sham rats. Sprague-Dawley rats were randomly divided into five groups, as follows: vehicle; EET at 0.025, 0.05, and 0.1 μg; and EET (0.1 μg) + EEZE (3.25 ng). EET or and vehicle were administered into VPL nuclei three consecutive days after hemorrhagic stroke. Immunostaining, ELISA, and Western blot were performed to evaluate neuroinflammation and apoptosis. Hemorrhagic stroke induced mechanical allodynia, glial activation, neuroinflammation, and apoptosis-related protein upregulation. However, early treatment with 14,15-EET inhibited glial cell activation, decreased proinflammatory cytokines and apoptosis-related protein, and alleviated the pain behavior of CPSP rats. Our results provided strong evidence that antinociception produced by 14,15-EET is partly mediated by the inhibition of neuroinflammation and apoptosis.

The increased prevalence of temporomandibular joint osteoarthritis (TMJOA) in children and adolescents has drawn considerable attention as it may interfere with mandibular condyle growth, resulting in dento-maxillofacial deformities. However, treatments for osteoarthritis have been ineffective at restoring the damaged bone and cartilage structures due to poor understanding of the underlying degenerative mechanism. In this study, we demonstrate that Gli1 cells residing in the subchondral bone contribute to bone formation and homeostasis in the mandibular condyle, identifying them as osteogenic progenitors in vivo. Furthermore, we show that, in a TMJOA mouse model, derivatives of Gli1+ cells undergo excessive expansion along with increased but uneven distribution of osteogenic differentiation in the subchondral bone, which leads to abnormal subchondral bone remodeling via Hedgehog (Hh) signaling activation and to the development of TMJOA. The selective pharmacological inhibition and specific genetic inhibition of Hh signaling in Gli1 osteogenic progenitors result in improved subchondral bone microstructure, attenuated local immune inflammatory response in the subchondral bone, and reduced degeneration of the articular cartilage, providing in vivo functional evidence that targeting Hh signaling in Gli1 osteogenic progenitors can modulate bone homeostasis in osteoarthritis and provide a potential approach for treating TMJOA.

Neuropathic pain is a prevalent and debilitating chronic disease that is characterized by activation in glial cells in various pain-related regions within the central nervous system. Recent studies have suggested a sexually dimorphic role of microglia in the maintenance of neuropathic pain in rodents. Here, we utilized RNA sequencing analysis and in vitro primary cultures of microglia to identify whether there is a common neuropathic microglial signature and characterize the sex differences in microglia in pain-related regions in nerve injury and chemotherapy-induced peripheral neuropathy mouse models. While mechanical allodynia and behavioral changes were observed in all models, transcriptomic analysis of microglia revealed no common transcriptional changes in spinal and supraspinal regions and in the different neuropathic models. However, there was a substantial change in microglial gene expression within the ipsilateral lumbar spinal cord 7 days after chronic constriction injury (CCI) of the sciatic nerve. Both sexes upregulated genes associated with inflammation, phagosome, and lysosome activation, though males revealed a prominent global transcriptional shift not observed in female mice. Transcriptomic comparison between male spinal microglia after CCI and data from other nerve injury models and neurodegenerative microglia demonstrated a unique CCI-induced signature reflecting acute activation of microglia. Further, in vitro studies revealed that only male microglia from nerve-injured mice developed a reactive phenotype with increased phagocytotic activity. This study demonstrates a lack of a common neuropathic microglial signature and indicates distinct sex differences in spinal microglia, suggesting they contribute to the sex-specific pain processing following nerve injury.