Bioengineering a complex 3D human breast tissue culture system on silk scaffolds

Epithelial-stromal interactions play a crucial role in normal embryonic development and carcinogenesis of the human breast while the underlying mechanisms of these events remain poorly understood. Here, we constructed a physiologically relevant, 3D culture surrogate of complex human breast tissue that included a tri-culture system made up of human mammary epithelial cells (MCF10A), fibroblasts and adipocytes in a Matrigel¿/collagen mixture on porous silk scaffolds. The presence of stromal cells inhibited MCF10A proliferation and induced both alveolar and ductal morphogenesis and enhanced casein expression. Only alveolar structures with reverted polarity were observed in MCF10A monocultures. In contrast to the immature polarity exhibited by co-cultures with either fibroblasts or adipocytes, the alveolar structures formed by the tri-cultures exhibited proper polarity similar to that observed in breast tissue. Furthermore, consistent with their phenotypic appearance, more functional differentiation of epithelial cells was also observed in the tri-cultures, where casein a and ß-mRNA expression was significantly increased. This in vitro tri-culture system sustained on silk scaffold effectively represents a more physiologically relevant 3D microenvironment for mammary epithelial cells and stromal cells than either co-cultures or monocultures. This experimental model provides an important first step for bioengineering an informative human breast tissue system.