In Vitro Chondrotoxicity of Mepivacaine Is Exposure- and Culture Model-Dependent

Introduction: Local anaesthetic administration into joints is a common diagnostic and analgesic procedure in veterinary species and people. Several published studies have documented that local anaesthetics cause articular chondrocyte death. These studies used isolated chondrocytes, excessive drug concentrations and/or did not account for drug half-lives and clearance profiles. We hypothesized that cartilage matrix and appropriate drug half-life dilutions would mitigate the in vitro chondrotoxic effects of mepivacaine.

Materials and Methods: Articular cartilage explants (n = 4) and chondrocyte aggregates (n = 6) were cultured in basal medium (controls), in 40% mepivacaine/medium (Full) or in medium with appropriate mepivacaine “half-life” dilutions (T1/2), in nonadherent culture wells for the equivalent of eight mepivacaine half-lives. Chondrotoxicity after exposure was assessed using the MTS assay. Explant cell viability was also assessed by “live/dead” fluorescence. The impact of Mepivacaine on Sox 9, Collagen type II and aggrecan expression was assessed by qPCR. Outcomes were analysed using repeated measure ANOVAs.

Results: There was significant chondrotoxicity in “Full Mep” aggregate and explant cultures, however, the T1/2 groups did not differ from controls. Aggrecan expression was reduced in “Full Mep” explant cultures, while other gene targets were not statistically affected in either culture model.

Discussion/Conclusion: With appropriate half-life dilution profiles, mepivacaine chondrotoxicity was not significant in either culture model. A cartilaginous matrix was not, by itself, protective. These results are reassuring, from a clinical perspective, but emphasize the importance of appropriate modelling in designing in vitro toxicity experiments.

Acknowledgment

This study was funded by the Companion Animal Research Fund.

 

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Publication History

Article published online:
15 July 2025