Membrane metallo-endopeptidase is dispensable for repair after nerve injury

Perineural Invasion Is Associated With Function-evoked Pain and Altered Extracellular Matrix in Patients With Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is painful, and perineural invasion (PNI) has been associated with the worst pain. Pain due to HNSCC is diverse and may vary based on clinicopathological factors. This study aims to characterize different pain patterns linked with PNI, its influence on daily functioning, and gain insights into molecular changes and pathways associated with PNI-related pain in HNSCC patients. We conducted a cross-sectional study across 3 medical centers (n = 114), assessing pain phenotypes and their impact on daily functioning using 2 self-reported pain questionnaires, given to patients prior to their cancer surgery. Furthermore, we conducted RNA-seq analysis utilizing the The Cancer Genome Atlas dataset of HNSCC tumor from patients (n = 192) to identify genes relevant to both PNI and pain. Upon adjusting for demographic and clinicopathological variables using linear regression models, we found that PNI independently predicted function-evoked pain according to the University of Calfornia San Francisco Oral Cancer Pain Questionnaire, as well as the worst pain intensity reported in the Brief Pain Inventory. Distinct pain patterns were observed to be associated with daily activities in varying manners. Our molecular analyses revealed significant disruptions in pathways associated with the extracellular matrix structure and organization. The top differentially expressed genes linked to the extracellular matrix are implicated in cancer development, pain, and neurodegenerative diseases. Our data underscore the importance of properly categorizing pain phenotypes in future studies aiming to uncover mechanistic underpinnings of pain. Additionally, we have compiled a list of genes of interest that could serve as targets for both cancer and cancer pain management. PERSPECTIVE: PNI independently predicts function-evoked pain. Different pain phenotypes affect daily activities differently. We identified a list of candidate genes involved in the extracellular matrix structure and function that can be targeted for both cancer and cancer pain control.

Pain sensitivity genes as therapeutic targets in knee osteoarthritis: A comprehensive analysis

Pain sensitivity is a significant factor in knee osteoarthritis (KOA), influencing patient outcomes and complicating treatment. Genetic differences, particularly in pain-sensing genes (PSRGs), are known to contribute to the variability in pain experiences among KOA patients. This study aims to systematically analyze PSRGs in KOA to better understand their role and potential as therapeutic targets. We utilized bulk RNA-seq data from the GSE114007 and GSE169077 datasets to identify differentially expressed genes, with 20 genes found to be significantly altered. Key PSRGs, including PENK, NGF, HOXD1, and TRPA1, were identified using LASSO, SVM, and random forest algorithms. Further, KEGG and GO enrichment analyses revealed pathways such as "Neuroactive ligand-receptor interaction" and "ECM-receptor interaction," which were validated through external datasets. Single-cell RNA-seq analysis from GSE152805, GSE133449, and GSE104782 datasets demonstrated the heterogeneity and dynamic expression of PSRGs across different cell subpopulations in synovium, meniscus, and cartilage samples. UMAP and pseudotime analyses were used to visualize spatial distribution and developmental trajectories of these genes. The findings emphasize the critical roles of PSRGs in KOA, highlighting their potential as therapeutic targets and suggesting that integrating genetic information into clinical practice could significantly improve pain management and treatment strategies for KOA.

Membrane metallo-endopeptidase is dispensable for repair after nerve injury

Membrane metallo-endopeptidase (MME), also known as neprilysin (NEP), has been of interest for its role in neurodegeneration and pain due to its ability to degrade β-amyloid and substance-P, respectively. In addition to its role in the central nervous system, MME has been reported to be expressed in the peripheral system, specifically in the inner and outer border of myelinating fibers, in the Schmidt-Lantermann cleft and in the paranodes. Recently, mutations of this gene have been associated with Charcot-Marie-Tooth Type 2 (CMT2). Peripheral nerve morphometry in mice lacking MME previously showed minor abnormalities in aged animals in comparison to CMT2 patients. We found that MME expression was dysregulated after nerve injury in a Neuregulin-1 dependent fashion. We therefore explored the hypothesis that MME may have a role in remyelination. In the naïve state in adulthood we did not find any impairment in myelination in MME KO mice. After nerve injury the morphological outcome in MME KO mice was indistinguishable from WT littermates in terms of axon regeneration and remyelination. We did not find any difference in functional motor recovery. There was a significant difference in sensory function, with MME KO mice starting to recover response to mechanical stimuli earlier than WT. The epidermal reinnnervation, however, was unchanged and this altered sensitivity may relate to its known function in cleaving the peptide substance-P, known to sensitise nociceptors. In conclusion, although MME expression is dysregulated after nerve injury in a NRG1-dependent manner this gene is dispensable for axon regeneration and remyelination after injury.