# A Safety and Efficacy Study of a Synthetic Biolubricant in an Equine Model of Post-Traumatic Osteoarthritis

## TL;DR

This study tests a synthetic biolubricant in horses with joint damage, finding some cartilage protection but also mild inflammation.

## Contribution

The study evaluates a biolubricant's safety and efficacy in a translational equine model of post-traumatic osteoarthritis.

## Key findings

- pMPC-treated joints showed lower cartilage erosion and higher glycosaminoglycan content.
- pMPC induced mild inflammation with increased synovial cell count and prostaglandin E2 levels.
- Osteophyte formation was higher in pMPC-treated joints compared to controls.

## Abstract

The biolubricant polymer, poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC), enhances articular lubrication in ex vivo cartilage explants and protects articular cartilage in an in vivo small animal model. Herein, we assessed the efficacy of the biolubricant pMPC for the treatment of a highly translational model of post-traumatic osteoarthritis (PTOA) model in horses. The pMPC may demonstrate cartilage protective effects with lower total cartilage erosion scores and increased levels of glycosaminoglycan retained in the cartilage compared to saline-treated joints. However, a mild inflammatory state is present on a cellular level, resulting in clinical evidence of mild pain scores and increased osteophyte formation. Further research is warranted to elucidate a chemical structure, concentration, and dose that maximizes the cartilage protective effects and minimizes the synovial inflammatory effects.

Post-traumatic osteoarthritis (PTOA) is a common cause of lameness in the horse. There is no cure, therefore treatments are aimed at reducing pain and improving the joint environment by modifying inflammatory pathways or by viscosupplementation. Here, we report the safety and efficacy of the biolubricant (poly(2-methacryloyloxyethyl phosphorylcholine; pMPC) to mitigate the physical, gross, histological, and biochemical effects of arthritis. We created an osteochondral fragment in the middle carpal joint of one limb in 16 horses to induce PTOA; the contralateral limb served as a sham-operated joint. Two weeks postoperative, half (n = 8) of the horses received a single injection of pMPC in the PTOA joint, while the other half received saline. All sham-operated joints (n = 16) received saline. We conducted clinical evaluations weekly while synovial fluid biomarkers were measured biweekly during the 70-day study period. Subsequently, we performed postmortem gross and histologic analyses. Horses in which PTOA joints were treated with pMPC exhibited mild increases in clinical data, including lameness, effusion, and flexion scores. Similarly, synovial cell count, total protein, and prostaglandin E2 values were higher for pMPC-treated joints. Radiographic changes included significantly higher osteophyte scores in pMPC-treated joints at the terminal timepoint. The biolubricant may demonstrate some chondroprotective effects with lower total erosion scores and higher cartilage glycosaminoglycan content. In summary, when pMPC is administered to PTOA joints, the biolubricant induces a mild inflammatory response but may offer some chondroprotective effects in horses.