In Vitro and Ex Vivo Evaluation of Rifampicin Cytotoxicity in Human Skin Models.

Background/Objectives: Drugs for human use require several studies for the assessment of their efficacy and safety. An important property is cytotoxicity, which should be tested in different environments and models in closer proximity to the final use of the drug, with greater reliability. Thus, we proposed to evaluate the toxicity of rifampicin, the only bactericidal drug in the anti-leprosy multidrug therapy, using skin cells and skin explant cultures. Methods: Cell viability was tested by the MTT method using primary keratinocytes and fibroblasts and immortalized skin cells (HaCaT and 3T3) at 24, 48, and 72 h of treatment. For the skin explant, we used the TTC assay to determine viability (24, 48, 72, and 96 h), hematoxylin and eosin staining to analyze the structure and architecture of the tissue, and TUNEL to assess apoptotic cells at 3, 6, 12, 24, 48, 72, and 96 h. Results: Regarding the toxicity of primary and immortalized cells, viability was above 70% up to a concentration of 50 μg/mL at 24, 48, and 72 h, and at the concentration of 200 μg/mL, all cells showed greater sensitivity, especially at 72 h. Tissue viability analysis revealed a high percentage (above 96%) of viable tissue at the concentrations of 100, 150, and 200 μg/mL at the time points studied. Histological analysis showed that tissue architecture was maintained, with no apoptotic cells being observed. Conclusions: Thus, our results showed the importance of evaluating drug toxicity using different cell types, with the ex vivo skin model proving to be an alternative to animal use.