Effect of intra-articular injection of high-molecular-weight versus low-molecular-weight hyaluronic acid on the articular cartilage structure in experimentally induced knee joint osteoarthritis in albino rats

Introduction: Osteoarthritis (OA) is the most common chronic joint disease in the elderly population, causing significant pain and disability. Currently available pharmacological therapies target palliation of pain. Hyaluronic acid (HA) is the major hydrodynamic component of joint synovial fluid. Hence, intra-articular treatment with HAs has recently become the most widely accepted therapy for OA. Aim of the work :The goal of this study was to clarify whether the potential efficacy of the intraarticularly injected HA in early OA induced in knee joints of albino rats was molecular weight-dependent. Materials and methods : Twenty-five adult male rats were used in the study and were divided into five equal groups. Group I served as the control group. Rats in group II were used as a model of early OA with a single injection of monoiodoacetate into the bilateral knee joints and were sacrificed after 2 weeks. Rats in group III were used as a model of progressive OA using the same drug as in group II but were sacrificed after 4 weeks. Rats in groups IV and V were subjected first to OA induction and, after 2 weeks, to an intra-articular injection of high-molecular-weight or low-molecular-weight HA once weekly for an additional 2 weeks, after which they were sacrificed. Knee joints were dissected out and processed for light microscopic examination. Results: Osteoarthritic degenerative changes in the articular cartilage were seen 2 weeks after MIA intra-articular injection. These changes progressed and worsened after 4 weeks in group III. Intra-articular injection of high-molecular-weight HA reversed most of the early degenerative changes. However, low-molecular-weight HA was not as effective. Conclusion: High-molecular-weight HA efficiently managed the articular cartilage structural damages after OA induction. However, low-molecular-weight HA was less efficient in treating early osteoarthritic changes in rat knee joints.