In Situ Calcium Signaling of Chondrocytes Under Non-Serum and Serum Culture

Chemically defined serum-free medium has been shown to maintain the mechanical properties of cartilage allografts better than serum supplemented medium during long-term in vitro culture [1]. Little is known about this beneficial mechanism at a cellular level. Intracellular calcium ([Ca²⁺]_i) signaling is one of the earliest responses in chondrocytes under mechanical stimulation [2]. It was recently found that calcium signaling is involved in the regulation of chondrocyte morphology changes and its short-term anabolic and catabolic responses under mechanical stimulation [3]. In this study we hypothesized that the beneficial mechanisms of serum-free culture could be indicated by the spatiotemporal features of [Ca²⁺]_i signaling of chondrocytes in situ. We aimed to: (i) compare the in situ spontaneous [Ca²⁺]_i responses of chondrocytes cultured in medium with and without serum; (ii) investigate the correlation between the [Ca²⁺]_i responses of chondrocytes and the biomechanical properties of cartilage explants.