Abstract
The biophysical properties of the basement membrane that surrounds human breast glands are poorly understood, but are thought to be decisive for normal organ function and malignancy. Here, we characterize the breast gland basement membrane with a focus on molecule permeation and mechanical stability, both crucial for organ function. We used well-established and nature-mimicking MCF10A acini as 3D cell model for human breast glands, with ether low- or highly-developed basement membrane scaffolds. Semi-quantitative dextran tracer (3 to 40 kDa) experiments allowed us to investigate the basement membrane scaffold as a molecule diffusion barrier in human breast acini in vitro. We demonstrated that molecule permeation correlated positively with macromolecule size and intriguingly also with basement membrane development state, revealing a pore size of at least 9 nm. Notably, an intact collagen IV mesh proved to be essential for this permeation function. Furthermore, we performed ultra-sensitive atomic force microscopy to quantify the response of native breast acini and of decellularized basement membrane shells against mechanical indentation. We found a clear correlation between increasing acinar force resistance and basement membrane formation stage. Most important native acini with highly-developed basement membranes as well as cell-free basement membrane shells could both withstand physiologically relevant loads (≤ 20 nN) without loss of structural integrity. In contrast, low-developed basement membranes were significantly softer and more fragile. In conclusion, our study emphasizes the key role of the basement membrane as conductor of acinar molecule influx and mechanical stability of human breast glands, which are fundamental for normal organ function.
Highlights
The pre-pubertal and pubertal mammary gland consists of ducts terminated by highly proliferative structures without hollow lumen [1]
We aimed to achieve higher fraction of MCF10A acini with homogeneously shaped and highlydeveloped basement membrane (BM) shells. To this end we focused on epidermal growth factor (EGF) as main trigger for epithelial cell growth (Fig 1A and 1B)
The influence of temporal staggered EGF withdrawal on morphogenesis was systematically tested on developing MCF10A acini (Fig 1C)
Summary
The pre-pubertal and pubertal mammary gland consists of ducts terminated by highly proliferative structures (called terminal end buds) without hollow lumen [1]. Lumen harboring alveoli are formed only during pregnancy as final functional developmental stage. BMs are highly organized and condensed extracellular matrix structures secreted by epithelial, endothelial and smooth muscle cells [5,6]. BM consist of a collagen IV mesh anchored to laminins, nidogen, entactin and perlecan [7]. The overall composition of BMs varies according to developmental stages and organ function [8]. BMs form physical barriers separating epithelial and stromal cells [9] and regulate molecule diffusion [2,3]
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