Multiple differentiation pathways of rat mammary stromal cells in vitro: acquisition of a fibroblast, adipocyte or endothelial phenotype is dependenton hormonal and extracellular matrix stimulation
D. Zangani et al., Multiple differentiation pathways of rat mammary stromal cells in vitro: acquisition of a fibroblast, adipocyte or endothelial phenotype is dependenton hormonal and extracellular matrix stimulation, DIFFERENTIA, 64(2), 1999, pp. 91-101
It has previously been shown that mammary stromal cells possess the ability
to maintain a fibroblastlike phenotype or differentiate in vitro into matu
re adipocytes in a hormone-dependent manner. This paper reports that rat ma
mmary stromal cells can also differentiate into capillary-like structures i
n vitro when cultured on a reconstituted basement membrane (RBM). The diffe
rentiation potential of mammary stromal cells was compared with that of hum
an umbilical vein endothelial cells (HUVEC) and 3T3-L1 preadipocytes. When
cultured on plastic, mammary stromal cells, 3T3-L1 and HUVEC maintained a f
ibroblast-like phenotype. Mammary stromal cells and 3T3-L1, but not HUVEC,
differentiated into mature adipocytes when cultured in adipogenic medium. W
hen plated on reconstituted basement membrane, all three cell types began t
o migrate and organize themselves into an interconnected capillary network.
By 18-20 h, mammary stromal cells organized into complex, highly branched
capillary-like tubules whereas 3T3-L1 cells and HUVEC formed more simple st
ructures. Cross-sectional analysis demonstrated the presence of an internal
lumen. Mammary stromal cells were unique in their ability to progressively
develop into a three-dimensional, highly branched network invading the RBM
surface. The network formation was enhanced by the presence of vascular en
dothelial growth factor (VEGF) and was inhibited by the anti-angiogenic dru
g suramin. Western blotting analysis demonstrated the presence of the endot
helial-specific marker flk-1, as well as the presence of the tight-junction
-associated protein ZO-1. Mammary stromal cell differentiation into capilla
ry structures was not a terminal state, since these cells were still able t
o differentiate into adipocytes when ex posed to adipogenic medium. These f
indings suggest that mammary stromal cells differentiate into fibroblasts,
adipocytes or vascular structures in a hormone- and substatum-dependent man
ner, and may explain the dramatic changes in stromal composition during bot
h normal mammary gland development and tumorigenesis.