A sparing procedure to clear the mouse mammary fat pad of epithelial components for transplantation analysis.

Transplantation of epithelial cells into cleared fat pads is a widely used technique in the study of mammary gland biology. It was first described in 1959 and has remained a valuable technique, most recently in conjunction with the analysis of mammary anlagen from knockout mice with an embryonic lethal phenotype or reproductive defect, and for mammary epithelial stem-cell assays or analysis of precancerous cells. Mammary glands, unlike most other organs, mainly develop postnatally. When the small amount of endogenous epithelium present in the fat pad of a prepubertal mouse is removed, this clearance leaves a natural microenvironment that can be repopulated with exogenously supplied epithelial cells. Cells with the appropriate developmental potential (stem cells or progenitor cells) can regenerate the epithelial portion of the mammary gland after puberty and pregnancy. The conventional clearance of the fat pad is an involved surgical procedure. We have improved the technique and minimized surgery and recovery time, while maintaining an efficient removal of endogenous epithelium from the mammary fat pad.