Combined supplementation of ascorbic acid and thyroid hormone T3 affects tenocyte proliferation. The effect of ascorbic acid in the production of nitric oxide

Background: Tissue engineering is now increasingly focusing on cell-based treatments as pro-mising tools to improve tendon repair. However, many crucial aspects of tendon biology remain to be understood before adopting the best experimental approach for cell-tissue engineering. Methods: The role played by Ascorbic Acid (AA) alone and in combination with thyroid hormone T-3 in the viability and proliferation of primary human tendon-derived cells was investigated. Human tenocyte viability was detected by Trypan blue exclusion test and cellular proliferation rate was evaluated by CFSE CellTrace T. In addition, the potential role of the AA in the production of Nitric Oxide (NO) was also examined. Results: In this in vitro model, an increase in tenocyte proliferation rate was observed as a consequence of progressively increased concentrations of AA (from 10 to 50 mu g/ml). The addition of the T-3 hormone to the culture further increased tenocyte proliferation rate. In detail, the most evident effect on cellular growth was achieved using the combined supplementation of 50 mu g/ml AA and 10(-7) M T-3. Conclusion: We showed that the highest concentration of AA (100 and 500 mu g/ml) caused cytotoxicity to human tenocytes. Moreover, it was shown that AA reduces NO synthesis. These results show that AA is a cell proliferation inducer that triggers tenocyte growth, while it reduces NO synthesis.