A controlled release bupivacaine-alginate construct: Effect on chondrocyte hypertrophy conversion

OBJECTIVE: Osteoarthritis is a degenerative disease of the joint, affecting over 30 million people in the US(1). A key characteristic of OA is chondrocyte hypertrophy, characterized by chondrocyte changes to a more rounded and osteoblastic phenotype, characterized by increased IL-6 and IL-8 secretion(2). While there are no cures for OA, treatments focus on mitigating pain and inflammation, the two main symptoms of OA. However, the analgesics, NSAIDS and corticosteroids commonly used, do not target regeneration and have negative side effects. Local anesthetics (LA) can be used as a pain management alternative but are usually short lasting and therefore, not suited for chronic conditions such as OA. Our engineered sustained release local anesthetic construct successfully delivers bupivacaine for an extended period of time(3-5). This study is designed to evaluate the effect of the LA system on chondrocytes in an inflammatory OA-like environment. DESIGN: Chondrocytes were cultured with bolus, liposomal, or construct LA and either untreated or treated with TNF-α and IL-1α for 24 hrs, 48 hrs, or 96 hrs. Chondrocyte viability, interleukin-8 (IL-8), interleukin-6 (IL-6), collagenase activity and proteoglycan deposition were assessed. RESULTS: In the presence of the engineered construct, the chondrocytes retained viability and regenerative function. Moreover, the construct allowed for higher initial doses to be used, which promoted more regeneration and decreased inflammation without compromising cellular viability. CONCLUSIONS: The construct promotes a less hypertrophic chondrocyte environment while promoting a more anti-inflammatory environment. These two factors are consistent with a less OA progressive environment when using the engineered construct, compared to bolus LA.