Optimization and Application of In Vitro and Ex Vivo Models for Vaginal Semisolids Safety Evaluation

Preclinical safety assessment of vaginal products includes cytotoxicity assays upon cell lines. Furthermore, tissue explants have been considered for application on ex vivo models. In this study, traditional and renewed methods were studied for toxicity assessment of vaginal semisolids upon products currently used in clinical practice as antimicrobials (Gino-Canesten^®, Sertopic^®, Dermofix^®, Gyno-Pevaryl^®, Lomexin^®, Gino Travogen^®, Dalacin V^®), containing estrogens (Ovestin^®, Blissel^®, Colpotrophine^®), and reference formulations (Replens^®, Universal Placebo). Two in vitro cytotoxicity tests were performed: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and neutral red uptake upon uterine (HEC-1A), cervical (HeLa) and vaginal (VK2 E6/E7) cells, according to ISO/EN 10993-5 (in vitro evaluation of medical devices). Similarly, a strategy to determine tissue viability on ex vivo porcine vaginal model (through MTT reduction assay and histological analysis) was developed and optimized. The vaginal cell line VK2 E6/E7 conducted to the most accurate calculation of half-maximal toxic concentration among all cells on the MTT assay. However, it was shown not be sensitive to the neutral red uptake assay. Tissues from the porcine model were collected with approx. 15% variability in thickness and variation coefficients lower than 25% when testing negative and positive controls were achieved. These models can improve cost-efficiency in early steps of product development.