Infection through the vaginal-ectocervical (VEC) tissue is believed to be the main route for the heterosexual transmission of the human immunodeficiency virus (HIV) in women.
Recently, a tissue culture-based model of the VEC (EpiVaginal) has been developed. Normal, human VEC epithelial and dendritic cell co-cultures were used to form a three-dimensional tissue using specially formulated medium. The in vitro engineered tissue reproduces many of the histological and ultrastructural features including basal, parabasal, glycogenated intermediate, and the superficial cell layers.
Preliminary experiments showed the use of this tissue model and the MTT tissue viability assay for predicting VEC irritation of microbicides*. Different concentrations of Nonoxynol-9 (N-9), carrageenin-I, and methyl cellulose were dosed topically and the viability of the VEC tissue was determine by MTT.
Following 24 hr exposure to N-9 (0.1%) tissue viability was reduced to 51%. In contrast, carrageenin-I (20%) reduces viability to 77% and no effect was observed for methyl cellulose (up to 20%). H & E staining showed irritation of epithelial lining following N-9 treatment greater than or equal to 0.1%. Experiments also showed that HIV virions do not pass freely through the tissue but they infect cells in the reconstructed VEC tissue model containing dendritic cells.
In conclusion, the tissue model is likely to serve as a useful tool to screen new or existing microbicide formulations for vaginal toxicity and microbicidal efficacy.
Excerpted from, "HUMAN VAGINAL-ECTOCERVICAL TISSUE MODEL FOR MICROBICIDE IRRITATION STUDIES" (MatTek Corp. Technical Reference TR-320) - Presented at "Microbicides 2004", London, England, March 28-31, (2004).
Technical References - Microbicide Toxicity, Efficacy Testing
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EpiVaginal Data Sheet
EpiVaginal Technical References
*Microbicide - any substance that can substantially reduce transmission of sexually transmitted infections (STIs) when applied either in the vagina or the rectum.