Self-organization is a dynamic and lineage-intrinsic property of mammary epithelial cells

Abstract

Loss of organization is a principle feature of cancers; therefore it is important to understand how normal adult multilineage tissues, such as bilayered secretory epithelia, establish and maintain their architectures. The self-organization process that drives heterogeneous mixtures of cells to form organized tissues is well studied in embryology and with mammalian cell lines that were abnormal or engineered. Here we used a micropatterning approach that confined cells to a cylindrical geometry combined with an algorithm to quantify changes of cellular distribution over time to measure the ability of different cell types to self-organize relative to each other. Using normal human mammary epithelial cells enriched into pools of the two principal lineages, luminal and myoepithelial cells, we demonstrated that bilayered organization in mammary epithelium was driven mainly by lineage-specific differential E-cadherin expression, but that P-cadherin contributed specifically to organization of the myoepithelial layer. Disruption of the actomyosin network or of adherens junction proteins resulted in either prevention of bilayer formation or loss of preformed bilayers, consistent with continual sampling of the local microenvironment by cadherins. Together these data show that self-organization is an innate and reversible property of communities of normal adult human mammary epithelial cells. mammary gland | tissue biology M ost mammalian adult tissues are replenished and repaired throughout life by reservoirs of stem cells. As new somatic cells replace old ones or build new tissue, organization and architecture must be maintained. The alternative, loss of organization in adult tissues, is associated with cancer and other diseases. Lineage-specific progenitors or their differentiated progeny must have a means to reach their ultimate site of residence within the adult tissue. The robust ability to organize cells into tissues is marked from conception: Heterogeneous aggregates of dissociated cells from embryonic tissues, suspended in gels or hanging droplets or on agarose-coated plates, self-organize into semblances of the original tissues (1-5). The mechanisms governing self-organization during developmental morphogenesis (6-10) are likely conserved in the maintenance of organization in adult tissues. Here we use normal human mammary epithelial cells (HMEC) as a model to determine how organized states are preserved in normal adult epithelia.The mammary gland undergoes cycles of proliferation and involution, showing as much as a 10-fold expansion in preparation for lactation followed by return to normal size. During these processes, the precise bilayered branching organization throughout the gland is maintained; secretory luminal epithelial cells (LEPs) line the lumen, surrounded by a layer of contractile myoepithelial cells (MEPs) that are adjacent to the basement membrane. We hypothesized that mammary epithelial cells possessed lineage-specific intrinsic abilities to self-organize into domains of lineage specificity. Such a...

Self-organization process in newborn skin organoid formation inspires strategy to restore hair regeneration of adult cells

“…7 can also be useful to appreciate the diverse morphogenetic phenotypes by different epithelial organoids. For example, reconstituted primary mammary myoepithelial cells and luminal cells can form glandular cystic aggregates when placed on Matrigel substrates (2,35). However, when FGF2 is provided, the cysts undergo branching morphogenesis (36) and do not coalesce toward a planar configuration.…”

A strategy for tissue self-organization that is robust to cellular heterogeneity and plasticity

“…Regulated differences in cell-cell cohesion are also thought to contribute to the self-organization and repair of adult human secretory organs such as the mammary gland (7,8). The mammary gland, along with the prostate, salivary, lacrimal, and sweat glands, has an architecture comprising two concentrically arranged epithelial cell types as shown in Fig.…”

Processing of Human Reduction Mammoplasty and Mastectomy Tissues for Cell Culture

“…We have observed superior growth when cultures are initiated as organoids rather than as dissociated single cells. Placement of organoids in culture using lowstress inducing media supports long-term growth of normal HMEC with markers of multiple lineage types (myoepithelial, luminal, progenitor) [4][5] . Sufficient numbers of cells can be obtained from one individual's tissue to allow extensive experimental examination using standardized cell batches, as well as interrogation using high throughput modalities.…”

“…Cultured HMEC have been employed in a wide variety of studies examining the normal processes governing growth, differentiation, aging, and senescence, and how these normal processes are altered during immortal and malignant transformation [4][5][6][7][8][9][10][11][12][13][14][15]16 . The effects of growth in the presence of extracellular matrix material, other cell types, and/or 3D culture can be compared with growth on plastic 5,15 .…”