CYTOKERATIN EXPRESSION IN MOUSE MAMMARY GLAND DURING FIRST FIVE WEEKS POST-PARTUM

Changes during mammary gland development can be detected with methods using specific antibodies directed against specific cell structures. In the present study, the expression pattern of a type of intermediate filament called cytokeratins (CKs) was evaluated in tissue samples from mice mammary glands during the first five weeks post-partum (pp). Animals were divided into 5 homogeneous groups with 8 mice in each. Immunofluorescence and immunohistochemical staining procedures were used to determine various characteristics of different cells in the mammary gland. Several CKs were analyzed with specific markers and immunohistochemistry methods: CK5, CK7 and CK14 were detected in all weeks pp, although in different cell types; CK8 was positive in all periods except at week 1 pp; CK6, CK16 and CK19 were partially identified; CK1 and CK13 were not observed during the trial; and vimentin was detected in fibroblasts and fatty cells. It is known that CK expression varies with physiological and pathological changes, and it has been reported to mark different epithelial cell lineages; its evaluation is therefore of considerable importance for studies of breast cancer of a stem/progenitor cell origin, both in humans and animals. Our trial provides additional knowledge relative to the use of specific antibodies and techniques as valuable tools to detect CKs during early post-partum (pp) mice mammary gland development (weeks 1 to 5 pp), emphasizing the role of CKs as markers of mammary epithelial differentiation.