Submitted to: Journal of Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2007
Publication Date: 12/1/2007
Citation: Maningat, P.D., Sen, P., Sunehag, A.L., Hadsell, D.L., Haymond, M.W. 2007. Regulation of gene expression in human mammary epithelium: Effect of breast pumping. Journal of Endocrinology. 195(3):503-511. Interpretive Summary: During the process of milk production the mammary cell deposits a portion of itself into the milk through a structure known as the milk fat globule crescent. Cellular messenger RNA is one of the components that can be found within these structures. In this study, RNA was purified from the milk of lactating women and then used to study changes in mammary cell gene expression. The results demonstrated that mammary cell messenger RNAs reflected changes in mammary cell function. This work lays the foundation for future research that will allow scientists to understand in greater detail how gene expression is regulated in the mammary cells of breastfeeding women.
Technical Abstract: Little is known of the molecular regulation of human milk production because of limitations in obtaining mammary tissue from lactating women. Our objectives were to evaluate whether RNA isolated from breast milk fat globules (MFGs) could be an alternative to mammary biopsies and to determine whether intense breast pumping, which increases prolactin (PRL) secretion, will upregulate alpha-lactalbumin (alpha-LA, a major determinant of lactose synthesis) transcription. RNA was isolated from MFG, and transcripts of interest were identified and quantitated by real-time RT-PCR using an external standard for normalization. In addition, we performed microarray studies to determine MFG RNA gene expression profile. Ten lactating women were studied using two protocols: protocol A with intense pumping from 0800 to 0814 h followed by short pumping, and protocol B with intense pumping from 1200 to 1214 h preceded by short pumping. Plasma PRL and MFG alpha-LA mRNA expression were measured. During protocol A, plasma PRL (61+/-7-248+/-43 mug/l by 14 min) and alpha-LA (3.5+/-0.9 fold by 6 h; P<0.03) increased. During protocol B, PRL gradually increased over 4 h from 69+/-14 to 205+/-28 mug/l, and further to 329+/-23 mug/l by 12 min of intense pumping; alpha-LA mRNA expression did not increase significantly. We conclude that MFGs provide a unique source to study the in vivo regulation of gene expression in mammary epithelial cells. alpha-LA mRNA is abundant in the MFG and its expression may be regulated by hormonal and temporal factors.