Oral Presentation The Annual Scientific Meeting of the Endocrine Society of Australia and the Society for Reproductive Biology 2013

Impaired TGFB signalling in macrophages perturbs mammary gland development (#147)

Xuan Sun 1 2 , Sarah Robertson 1 2 , Wendy Ingman 1 2 3
  1. Obstetrics and Gynaecology, The University of Adelaide, Adelaide, SA, Australia
  2. Robinson Institute, Adelaide
  3. Discipline of Surgery, School of Medicine , The Queen Elizabeth Hospital, Adelaide

Transforming growth factor beta 1 (TGFB1) is a multi-functional cytokine that regulates cell proliferation, apoptosis and immune system responses. In the breast, TGFB1 is mainly produced by mammary epithelium, where it co-localises with macrophages and regulates macrophage functions. We aimed to investigate the role of TGFB-regulated macrophages in normal mammary gland development using a double transgenic mouse whereby the macrophage specific Cfms promoter drives expression of a tetracycline-inducible dominant negative TGFB receptor (Cfms-rtTA x TetO-TBRII). Administration of doxycycline in the drinking water induces expression of the dominant negative TGFB receptor expression specifically in macrophages, thus switching off TGFB signalling. Single transgenic Cfms-rtTA mice given doxycycline were negative controls. The length of estrous cycles, monitored in the mice for a period of 4 weeks, was comparable between genotypes however time spent in the metestrus phase was reduced in double transgenic mice compared to single transgenic mice. To investigate the effect of impaired TGFB signalling in macrophages on mammary gland development, mammary glands were collected from doxycycline-treated double and single transgenic mice at diestrus. The number of ductal branching points and the percentage of alveolar epithelium was increased by 15% and 11% respectively in doxycycline-treated double transgenic mice mammary gland compared to single transgenic mice mammary gland (p<0.05). Mammary glands were also analysed by immunohistochemistry to investigate the location and abundance of F4/80+ and iNOS+ macrophages. Abundance of F4/80+ macrophages around the mammary gland epithelium of double transgenic mice was increased by 50% compared to single transgenic mice (p<0.05). The number of iNOS+ macrophages in the stroma surrounding doxycycline-treated double transgenic mice mammary epithelium was increased by 2.7 fold (p<0.01). These results suggest that TGFB exerts effects on mammary gland development via regulation of macrophage function.