Going deeper: three-dimensional study of γδ T cells in mouse reproductive tract using tissue clearing methods.

Several tissue clearing methods have been developed for three-dimensional imaging of thick specimens. Here, we applied CUBIC and ScaleS approaches to whole-mounted vaginal wall to reveal spatial distribution of γδ T lymphocytes, the key cells engaged in the epithelial homeostasis control and immune surveillance. Both methods rendered the tissue transparent and enabled detection of the green fluorescent protein (GFP)-expressing γδ T cells in vaginal samples of Tcrd-H2BeGFP transgenic mice. Upon additional immunolabeling, however, only CUBIC preserved the GFP signal and allowed for cell localization assessment during the estrous cycle. Using a combination of single- and two-photon microscopy, we found that during the diestrus phase the number of γδ T cells in the vaginal wall increased compared to estrus, while the proportion of cells residing in epithelium and stroma remained constant, irrespective of the cycle phase, and was close to 3:1, respectively. Moreover, the distance from epithelial γδ T cells to laminin-positive basal membrane and collagen-rich stroma also increased in diestrus in spite of thinning of epithelium upon shedding cornified cells. Our data indicate that γδ T cells sense sex hormone fluxes which influence their number and position them closer to the vaginal lumen in the diestrus phase.