Estrogen mediates mammary epithelial cell proliferation in serum-free culture indirectly via mammary stroma-derived hepatocyte growth factor.
Epithelial-stromal cell interactions are important for normal development and function of the mouse mammary gland. The steroid hormone estrogen is required for epithelial cell proliferation and ductal development in vivo. Recent studies of estrogen receptor alpha knockout mice indicate that estrogen-induced proliferation is dependent upon the presence of estrogen receptor in mammary stromal cells, but not in epithelial cells. The purpose of the present study was to identify the underlying mechanism of estrogen-dependent stroma-derived effects on mammary epithelium. We have developed a minimally supplemented serum-free medium, collagen gel primary mammary coculture system to address the issue of stroma-derived, estrogen-dependent effects on epithelial cell proliferation. Conditioned medium from mammary fibroblasts or coculture with mammary fibroblasts caused increased epithelial cell proliferation and produced tubular/ductal morphology. Hepatocyte growth factor (HGF) was identified as the mediator of this effect, as the proliferative activity in fibroblast-conditioned medium was completely abolished by neutralizing antibody to HGF, whereas neutralizing antibodies to either epidermal growth factor or IGF-I had no effect. Treatment of mammary fibroblasts with estrogen increased the production of HGF. From these results we conclude that estrogen may indirectly mediate mammary epithelial cell proliferation via the regulation of HGF in mammary stromal cells and that HGF plays a crucial role in estrogen-induced proliferation in vivo.
Zhang
Hong-Zheng
HZ
Department of Physiology, Michigan State University, East Lansing, Michigan 48824, USA.
Bennett
Jessica M
JM
Smith
Kyle T
KT
Sunil
Nityanand
N
Haslam
Sandra Z
SZ
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D018920:Coculture Techniques; D003094:Collagen; D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; D004847:Epithelial Cells / Q000166:cytology; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D005347:Fibroblasts / Q000502:physiology; D017228:Hepatocyte Growth Factor / Q000032:analysis / Q000276:immunology / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000737:chemistry / Q000166:cytology*; D051379:Mice; D008807:Mice, Inbred BALB C; D011960:Receptors, Estrogen / Q000032:analysis; D011994:Recombinant Proteins / Q000032:analysis; D017154:Stromal Cells / Q000737:chemistry*
D000906:Antibodies; D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; D004967:Estrogens; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D017228:Hepatocyte Growth Factor; D007334:Insulin-Like Growth Factor I; D003094:Collagen