Neurotrophin synthesis by mammary cells during lactation (623.19)

Abstract

Neurotrophins are growth factors primarily described in the development of the nervous system. They are secreted by developing organs to attract nerve fibres, acting as molecular mediators for establishment of connections with the nervous system. Recent evidence demonstrates that mammary cells synthesize neurotrophins; however, variation in their expression is poorly understood. In this study, we examined expression of a panel of key neurotrophins and their receptors by mammary cells in the normal breast. Rare specimens of human resting and lactating breast tissue were stained for these genes. This demonstrated an upregulation of certain neurotrophins and associated receptors, such as pro‐NGF, in the lactating breast, and a differential expression of others, such as TrkA, between the myoepithelial and luminal layers. We next measured transcript levels in breastmilk cells from 20 lactating women. For some genes, such as TRKB1 and Sortilin, transcript levels were upregulated during lactation, while for others, such as NT‐3 and p75NTR, a marked downregulation was observed during lactation. These findings describe differential regulation of neurotrophin expression in the normal breast during different stages of development. The downregulation of some neurotrophins during lactation suggests a potential pathway of de‐sensitization of the breast, which may contribute to successful breastfeeding.