IntroductionOsteoarthritis (OA) is a whole-joint disease characterized by a low-grade inflammation that is involved in both cartilage degradation and subchondral bone remodeling. Since subchondral bone has a cholinergic innervation and that acetylcholine (Ach) might have an anti-inflammatory effect through the α7 nicotinic Ach receptor (α7nAchR), we aimed (i) to determine the expression of non-neuronal cholinergic system and nicotinic receptor subunits by murine and human osteoblasts, (ii) to address the role of α7nAchR in osteoblastic response to inflammation, and (iii) to study the role of α7nAchR in a spontaneous aging OA model.MethodsPrimary cultures of WT and α7nAchR knock-out mice (Chrna7-/-) murine osteoblasts and of subchondral bone human OA osteoblasts were performed. The expressions of the non-neuronal cholinergic system and of the nAchR subunits were assessed by PCR. In vitro, IL1β-stimulated WT, Chrna7-/-, and human osteoblasts were pretreated with nicotine. At 24 h, expressions of interleukin-6 (IL6) and metalloproteinase-3 and -13 (MMP), RANK-ligand (RANKL), and osteoprotegerin (OPG) were quantified by qPCR and ELISA. Spontaneous aging OA was evaluated and compared between male WT and Chrna7-/- mice of 9 and 12 months.ResultsMurine WT osteoblasts express the main components of the cholinergic system and α7 subunit composing α7nAchR. Nicotine partially prevented the IL1β-induced expression and production of IL6, MMP3, and RANKL in WT osteoblasts. The effect for IL6 and MMP was mediated by α7nAchR since nicotine had no effect on Chrna7-/- osteoblasts while the RANKL decrease persisted. Chrna7-/- mice displayed significantly higher cartilage lesions than their WT counterparts at 9 and 12 months, without difference in subchondral bone remodeling. Human OA osteoblasts also expressed the non-neuronal cholinergic system and α7 subunit as well as CHRFAM7A, the dominant negative duplicate of Chrna7. Nicotine pretreatment did not significantly reduce IL6 and MMP3 production in IL-1β-stimulated human osteoarthritic osteoblasts (n = 4), possibly due to CHRFAM7A.ConclusionCholinergic system counteracts murine osteoblastic response to IL-1β through α7nAchR. Since α7nAchR deletion may limit cartilage degradation during murine age-related OA, enhancing cholinergic system could be a new therapeutic target in OA but may depend on CHRFAM7A expression.

Objective: To determine the prevalence, distribution and characteristics associated with radiographic metacarpophalangeal (MCP) osteoarthritis (OA).Methods: This is a cross-sectional study of baseline data from the DIGItal Cohort Osteoarthritis Design, a French monocentric cohort including patients with symptomatic hand OA (HOA). We evaluated the prevalence of radiographic MCP OA defined as ≥2 MCP joints with a Kellgren and Lawrence score ≥2. We compared the prevalence of MCP OA in the dominant and non-dominant hands. Associations between radiographic MCP OA and patient characteristics were studied using univariable and multivariable logistic regression.Results: Radiographic MCP OA was present in 138 of the 425 patients (32.5%) but was not severe. Patients with MCP OA had a mean age of 69.2±6.9 years, a BMI of 25±4.2 kg/m 2 , and 86.2% were women. MCP OA was more frequent in the dominant hand and predominated at the 1st and 2nd MCP joints. In the multivariable analysis, MCP OA was associated with older age (OR 1.05, 95%CI [1.01,1.10] for each year), manual occupation (OR 3.74, 95%CI [1.21,11.54]), scaphotrapezial OA (OR 2.18, 95%CI [1.27,3.72]), and a high number of proximal interphalangeal joints with radiographic OA. MCP OA was not associated with metabolic syndrome or HOA symptoms. Conclusion:In this cross-sectional study using a hospital-based HOA cohort, radiographic MCP OA was frequent and associated with structural HOA features rather than with symptom severity. Our results suggest that the involvement of MCP joints in HOA is predominantly related to mechanical rather than systemic factors in this population.