Stratification of the vaginal epithelium is regulated by stromal factors. To analyze the mechanisms of stratification in vitro, 3 dimensional (3D) co-culture models were established with clonal cell lines. In the models, stromal cells were embedded in collagen gel and epithelial cells were seeded on the gel. In the 3D co-culture, stromal SV-6c4a1b cells induced epithelial stratification but stromal MV-1e6g1a cells did not, suggesting that SV-6c4a1b cells secretemolecules to induce stratification. Microarray analyses of these stromal cell lines identified chordin-like 1 (Chrd1) andWNT1 inducible signaling pathway protein 2 (Wisp2) as candidate genes inducing stratification. Chrdl1 variant1 and variant2 mRNAs were expressed not only in stromal SV-6c4a1b and MV-1e6g1a cells but also in epithelial SV-4b6b cells. Wisp2-overexpressing MV-1e6g1a cells, secreting WISP2 as much as SV-6c4a1b cells, induced stratification of epithelial cells. In addition, Wisp2-knockdowned SV-6c4a1b cells were unable to induce epithelial stratification. These results suggest that WISP2 is one of the stromal factors inducing stratification of the mouse vaginal epithelium.
WISP2 secreted by vaginal stroma and regulated by estrogen induced stratification in vaginal epithelium.