Serum artemin is not correlated with sensitivity within dogs with naturally occurring osteoarthritis pain

Emerging evidence of artemin/GFRα3 signaling in musculoskeletal pain

Chronic musculoskeletal pain is highly prevalent and poses a significant personal, societal, and economic burden. Management of chronic musculoskeletal pain remains a challenge. Long-term use of common analgesic medications such as nonsteroidal anti-inflammatory drugs and opioids is associated with adverse events, and in the case of opioids, drug addiction. Additionally, many individuals do not experience sufficient pain relief with these therapeutic approaches. Thus, there is an urgent need to develop clinically efficacious and safe therapeutics for musculoskeletal pain. Recent advances in our understanding of musculoskeletal pain neurobiology have helped identify the role of neurotrophic factors, specifically, the glial cell line-derived neurotrophic factor family of ligands (GFL) and their associated signaling pathways. This review outlines our current understanding of the GFL signaling systems, discusses their role in inflammatory and chronic musculoskeletal pain and sensitivity, and comments on the analgesic therapeutic potential of targeting the GFL signaling system.

Initial exploration of the discriminatory ability of the PetPace collar to detect differences in activity and physiological variables between healthy and osteoarthritic dogs

Background

Accelerometry has been used to evaluate activity in dogs with osteoarthritis (OA) pain, especially in relation to effect of treatment; however no studies have compared accelerometry-measured activity in dogs with OA-pain and healthy dogs. The aims of this study were to (1) compare activity output from the PetPace collar with the validated Actical monitor and (2) determine if PetPace collar outputs (overall activity, activity levels, body position, and vital signs) differed between healthy dogs and dogs with OA-pain.

Methods

This was an observational, non-interventional study in healthy dogs and dogs with OA-pain. All dogs were outfitted with the PetPace collar and the Actical monitor simultaneously for 14 days. Output from these devices was compared (correlations), and output from the PetPace device was used to explore differences between groups across the activity and vital sign outputs (including calculated heart rate variability indices).

Results

There was moderate correlation between the PetPace collar and Actical monitor output (R² = 0.56, p < 0.001). Using data generated by the PetPace collar, OA-pain dogs had lower overall activity counts and spent less time standing than healthy dogs. Healthy dogs spent more time at higher activity levels than OA-pain dogs. Certain heart rate variability indices in OA-pain dogs were lower than in healthy dogs.

Conclusions and clinical relevance

The results of this study suggest that the PetPace collar can detect differences between healthy dogs and those with OA-pain, and that OA-pain negatively impacts overall activity levels in dogs, and especially higher intensity activity.

Investigating the Role of Artemin and Its Cognate Receptor, GFRα3, in Osteoarthritis Pain

Osteoarthritis (OA) associated pain (OA-pain) is a significant global problem. OA-pain limits limb use and mobility and is associated with widespread sensitivity. Therapeutic options are limited, and the available options are often associated with adverse effects. The lack of therapeutic options is partly due to a lack of understanding of clinically relevant underlying neural mechanisms of OA-pain. In previous work in naturally occurring OA-pain in dogs, we identified potential signaling molecules (artemin/GFRα3) that were upregulated. Here, we use multiple approaches, including cellular, mouse genetic, immunological suppression in a mouse model of OA, and clinically relevant measures of sensitivity and limb use to explore the functional role of artemin/GFRα3 signaling in OA-pain. We found the monoiodoacetate (MIA)-induced OA-pain in mice is associated with decreased limb use and hypersensitivity. Exogenous artemin induces mechanical, heat, and cold hypersensitivity, and systemic intraperitoneal anti-artemin monoclonal antibody administration reverses this hypersensitivity and restores limb use in mice with MIA-induced OA-pain. An artemin receptor GFRα3 expression is increased in sensory neurons in the MIA model. Our results provide a molecular basis of arthritis pain linked with artemin/GFRα3 signaling and indicate that further work is warranted to investigate the neuronal plasticity and the pathways that drive pain in OA.