# In Vitro Effects of PRP, Ozonized PRP, Hyaluronic Acid, Paracetamol, and Polyacrylamide on Equine Synovial Fluid-Derived Mesenchymal Stem Cells

## TL;DR

This study examines how various substances affect the growth and viability of stem cells from horse joint fluid, aiming to improve regenerative treatments for equine joint disorders.

## Contribution

The novel contribution is the in vitro evaluation of PRP, ozonized PRP, hyaluronic acid, paracetamol, and polyacrylamide on equine synovial fluid-derived MSCs.

## Key findings

- PRP significantly promotes MSC proliferation in a time- and dose-dependent manner.
- NOLTREX® shows a biphasic effect on MSCs, with initial inhibition followed by stimulation at 7 days.
- Ozonized PRP exhibits concentration-dependent redox activity, with lower doses maintaining cell viability.

## Abstract

Musculoskeletal disorders are a major cause of lameness in horses, often necessitating innovative regenerative strategies to restore joint function and improve quality of life. This study investigated the effects of platelet-rich plasma (PRP), ozonized PRP, hyaluronic acid, paracetamol, and polyacrylamide hydrogel (NOLTREX®) on the behavior of mesenchymal stem cells (MSCs) derived from equine synovial fluid. Synovial fluid samples were collected under strict cytological criteria to ensure viability, followed by in vitro expansion and phenotypic characterization of MSCs. Cultures were supplemented with the tested preparations, and cellular proliferation and viability were evaluated at 24 h, 72 h, and 7 days. PRP significantly promoted MSC proliferation in a time- and dose-dependent manner, with maximal effect at 10%. Hyaluronic acid stimulated growth, most pronounced at 1 mg/mL, while paracetamol induced a concentration-dependent proliferative response, strongest at 100 μg/mL. NOLTREX displayed a biphasic effect, initially inhibitory at high concentrations but stimulatory at 7 days. Ozonized PRP showed concentration-dependent redox activity, with lower doses maintaining viability and higher doses producing an initial suppression followed by delayed stimulation. Collectively, these findings support the therapeutic potential of PRP and related biologic preparations as intra-articular regenerative therapies in equine medicine, while underscoring the importance of dose optimization and standardized protocols to facilitate clinical translation.