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Objective: Knee joints are densely innervated by nociceptors. In human knees and rodent models, sprouting of nociceptors has been reported in latestage osteoarthritis (OA). Here, we sought to describe progressive nociceptor remodeling in early and late-stage OA, using four distinct experimental mouse models. Methods: Sham surgery, destabilization of the medial meniscus (DMM), partial meniscectomy (PMX), or non-invasive anterior cruciate ligament rupture (ACLR) was performed in the right knee of 10-12-week old male C57BL/6 NaV1.8-tdTomato mice. Mice were euthanized (1) 4, 8 or 16 weeks after DMM or sham surgery; (2) 4 or 12 weeks after PMX or sham; (3) 1 or 4 weeks after ACLR injury or sham. Additionally, a cohort of naïve male wildtype mice was evaluated at age 6 and 24 months. Mid-joint cryosections were assessed qualitatively and quantitatively for NaV1.8+ or PGP9.5+ innervation. Cartilage damage, synovitis, and osteophytes were assessed. Results: Progressive OA developed in the medial compartment after DMM, PMX, and ACLR. Synovitis and associated neo-innervation of the synovium by nociceptors peaked in early-stage OA. In the subchondral bone, channels containing sprouting nociceptors appeared early, and progressed with worsening joint damage. Two-year old mice developed primary OA in the medial and the lateral compartment, accompanied by nociceptor sprouting in the synovium and the subchondral bone. All four models showed increased nerve signal in osteophytes. Conclusion: These findings suggest that anatomical neuroplasticity of nociceptors is intrinsic to OA pathology. The detailed description of innervation of the OA joint and its relationship to joint damage might help in understanding OA pain. [ABSTRACT FROM AUTHOR]

Transient Receptor Potential Vanilloid 1 (TRPV1) is a nonselective cation channel expressed by pain-sensing neurons and has been an attractive target for the development of drugs to treat pain. Recently, Src homology region two domain-containing phosphatase-1 (SHP-1, encoded by Ptpn6) was shown to dephosphorylate TRPV1 in dorsal root ganglia (DRG) neurons, which was linked with alleviating different pain phenotypes. These previous studies were performed in male rodents only and did not directly investigate the role of SHP-1 in TRPV-1 mediated sensitization. Therefore, our goal was to determine the impact of Ptpn6 overexpression on TRPV1-mediated neuronal responses and capsaicin-induced pain behavior in mice of both sexes. Twelve-week-old male and female mice overexpressing Ptpn6 (Shp1-Tg) and their wild type (WT) littermates were used. Ptpn6 overexpression was confirmed in the DRG of Shp1-Tg mice by RNA in situ hybridization and RT-qPCR. Trpv1 and Ptpn6 were found to be co-expressed in DRG sensory neurons in both genotypes. Functionally, this overexpression resulted in lower magnitude intracellular calcium responses to 200 nM capsaicin stimulation in DRG cultures from Shp1-Tg mice compared to WTs. In vivo, we tested the effects of Ptpn6 overexpression on capsaicin-induced pain through a model of capsaicin footpad injection. While capsaicin injection evoked nocifensive behavior (paw licking) and paw swelling in both genotypes and sexes, only WT mice developed mechanical allodynia after capsaicin injection. We observed similar level of TRPV1 protein expression in the DRG of both genotypes, however, a higher amount of tyrosine phosphorylated TRPV1 was detected in WT DRG. These experiments suggest that, while SHP-1 does not mediate the acute swelling and nocifensive behavior induced by capsaicin, it does mediate a protective effect against capsaicin-induced mechanical allodynia in both sexes. The protective effect of SHP-1 might be mediated by TRPV1 dephosphorylation in capsaicin-sensitive sensory neurons of the DRG. [ABSTRACT FROM AUTHOR]

Introduction: Non-esophageal eosinophilic gastrointestinal disorders (non-EoE EGIDs) are rare, but their prevalence has recently increased. Although it has been reported that one-half of patients with non-EoE EGIDs have intractable clinical courses, their clinical features are not fully understood. Methods: This is a multicenter retrospective study in which 10 institutions in Japan participated. Clinical databases from January 1998 to December 2020 were reviewed to identify patients with non-EoE EGIDs. A total of 44 patients were identified; they were divided into two groups based on their clinical course: an intractable group and a non-intractable group. The clinical features were compared between the two groups by a logistic regression analysis. Remarkable eosinophilic infiltration (REI) was defined histologically when the maximal counts of mucosal eosinophils reached a threshold level in the respective area of biopsy. Results: Prevalence of drug allergy and eosinophil counts more than 500/μL (EOS), vomiting symptoms, abnormalities of the stomach, duodenum, and jejunum on computed tomography (upper gastrointestinal abnormality on computed tomography [UACT]), and REI were significantly different between the two groups. Among the factors that were potentially associated with an intractable clinical course, logistic regression revealed that REI, EOS, and UACT were significant factors. Based on an analysis of the area under the receiver operator characteristic curve, a combination of REI and EOS had the lowest Akaike's information criterion, indicating the best model to predict an intractable clinical course. Conclusions: REI may predict an intractable course in patients with non-EoE EGIDs. In addition, the combination of REI and EOS was a better predictor than REI alone. [ABSTRACT FROM AUTHOR]