Comparison between xCELLigence biosensor technology and conventional cell culture system for real-time monitoring human tenocytes proliferation and drugs cytotoxicity screening

BACKGROUND Local injections of anesthetics, NSAIDs, and corticosteroids for tendinopathies are empirically used. They are believed to have some cytotoxicity toward tenocytes. The maximal efficacy dosages of local injections should be determined. A commercial 2D microfluidic xCELLigence system had been developed to detect real-time cellular proliferation and their responses to different stimuli and had been used in several biomedical applications. The purpose of this study is to determine if human tenocytes can successfully proliferate inside xCELLigence system and the result has high correlation with conventional cell culture methods in the same condition. METHODS First passage of human tenocytes was seeded in xCELLigence and conventional 24-well plates. Ketorolac tromethamine, bupivacaine, methylprednisolone, and betamethasone with different concentrations (100, 50, and 10% diluted of clinical usage) were exposed in both systems. Gene expression of type I collagen, type III collagen, tenascin-C, decorin, and scleraxis were compared between two systems. RESULTS Human tenocytes could proliferate both in xCELLigence and conventional cell culture systems. Cytotoxicity of each drug revealed dose-dependency when exposed to tenocytes in both systems. Significance was found between groups. All the four drugs had comparable cytotoxicity in their 100% concentration. When 50% concentration was used, betamethasone had a relatively decreased cytotoxicity among them in xCELLigence but not in conventional culture. When 10% concentration was used, betamethasone had the least cytotoxicity. Strong and positive correlation was found between cell index of xCELLigence and result of WST-1 assay (Pearson's correlation [r] = 0.914). Positive correlation of gene expression between tenocytes in xCELLigence and conventional culture was also observed. Type I collagen: [r] = 0.823; type III collagen: [r] = 0.899; tenascin-C: [r] = 0.917; decorin: [r] = 0.874; and scleraxis: [r] = 0.965. CONCLUSIONS Human tenocytes could proliferate inside xCELLigence system. These responses varied when tenocytes were exposed to different concentrations of ketorolac tromethamine, bupivacaine, methylprednisolone, and betamethasone. The result of cell proliferation and gene expression of tenocytes in both xCELLigence and conventional culture system is strongly correlated. CLINICAL RELEVANCE xCELLigence culture system may replace conventional cell culture, which made real-time tenocyte proliferation monitoring possible.