Cadherin-mediated cell-cell adhesion and tissue segregation in relation to malignancy

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...

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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

Chanson

Brownfield

Garbe

et al. 2011

“…Most studies on the cell-cell adhesion that drives self-assembly are qualitative and have focused on the self-sorting of a mixture of cells (1,16), the role of cadherins (17), and the influence of surface tension (1,2). In this study, we have developed a unique assay to measure cell power, a quantitative measure of the work output of self-assembling cells.…”

Section: Discussionmentioning

confidence: 99%

“…In this theory, the apparent surface tension is regarded as the sole factor determining the formation and structure of self-assembled microtissues. Within a single cell line it was demonstrated that spheroid surface tension was directly proportional to cadherin expression, with cells with increased cadherin levels moving to the center of mixed spheroids (2,16,17). With this model, the process of self-assembly was deemed to be passive and even likened to soap bubble formations (26).…”

Section: Discussionmentioning

confidence: 99%

Quantification of the forces driving self-assembly of three-dimensional microtissues

Youssef¹,

Nurse

Freund

et al. 2011

In a nonadhesive environment, cells will self-assemble into microtissues, a process relevant to tissue engineering. Although this has been recognized for some time, there is no basis for quantitative characterization of this complex process. Here we describe a recently developed assay designed to quantify aspects of the process and discuss its application in comparing behaviors between cell types. Cells were seeded in nonadhesive micromolded wells, each well with a circular trough at its base formed by the cylindrical sidewalls and by a central peg in the form of a right circular cone. Cells settled into the trough and coalesced into a toroid, which was then driven up the conical peg by the forces of self-assembly. The mass of the toroid and its rate of upward movement were used to calculate the cell power expended in the process against gravity. The power of the toroid was found to be 0.31 ± 0.01 pJ/h and 4.3 ± 1.7 pJ/h for hepatocyte cells and fibroblasts, respectively. Blocking Rho kinase by means of Y-27632 resulted in a 50% and greater reduction in power expended by each type of toroid, indicating that cytoskeletal-mediated contraction plays a significant role in the self-assembly of both cell types. Whereas the driving force for self-assembly has often been viewed as the binding of surface proteins, these data show that cellular contraction is important for cell-cell adhesion. The power measurement quantifies the contribution of cell contraction, and will be useful for understanding the concerted action of the mechanisms that drive self-assembly. T he self-assembly of cells into microtissues, often viewed as a passive process driven by chemical forces resulting from binding of cadherins expressed on cell surfaces (1, 2), is now thought to be a more complex process. Recent work has shown that the cytoskeleton also plays an important role in force generation, stability, and self-sorting of microtissues (3-6). Thus, self-assembly is a complex process involving multiple protein mechanisms working in concert.Self-assembly and the cell-cell adhesion that drives it are relevant to tissue formation, morphogenesis, and disease. However, little quantitative data are available on the forces driving self-assembly. At the molecular level, precise measurements of the binding strength and energy of adhesion of surface proteins (7,8) as well as the force of contraction of the actin cytoskeleton (9, 10) have been made. On the cellular level, traction-force microscopy has been used to measure the adhesion forces of single cells on flat substrates (11-13), and fibroblast-populated collagen gels have been used in the study of cell-matrix interactions (14). However, cell-cell interactions in a 3D environment have not been fully investigated. Doing so requires a quantitative systems biology approach that can be used not only to quantify the aggregation and self-assembly of groups of cells but also to quantify the contributions of specific proteins and protein systems to the process.In the past, we have reported observations on ...

“…Not only do they hold cells together, but also differential expression of different types of these molecules plays a central role during development. Members of the cadherin family are the most widespread molecules that mediate adhesion among animal cells, and their role has been demonstrated in, e.g., cell sorting, migration, tumor invasibility, cell intercalation, packing of epithelial cells, axon outgrowth, and more (1)(2)(3)(4)(5)(6). We focus here on the role of adhesion in the determination of epithelial cell shape (7).…”

mentioning

confidence: 99%

Cell adhesion and cortex contractility determine cell patterning in the Drosophila retina

Käfer

Hayashi

Marée

et al. 2007

185

174

Because of the resemblance of many epithelial tissues to densely packed soap bubbles, it has been suggested that surface minimization, which drives soap bubble packing, could be governing cell packing as well. We test this by modeling the shape of the cells in a Drosophila retina ommatidium. We use the observed configurations and shapes in wild-type flies, as well as in flies with different numbers of cells per ommatidia, and mutants with cells where Eor N-cadherin is either deleted or misexpressed. We find that surface minimization is insufficient to model the experimentally observed shapes and packing of the cells based on their cadherin expression. We then consider a model in which adhesion leads to a surface increase, balanced by cell cortex contraction. Using the experimentally observed distributions of E-and N-cadherin, we simulate the packing and cell shapes in the wild-type eye. Furthermore, by changing only the corresponding parameters, this model can describe the mutants with different numbers of cells or changes in cadherin expression.cell shape ͉ surface mechanics ͉ Cellular Potts model