ECM-transmitted shear stress induces apoptotic cell extrusion in early breast gland development

Abstract

Epithelial cells of human breast glands are exposed to various mechanical ECM stresses that regulate tissue development and homeostasis. Mechanoadaptation of breast gland tissue to ECM-transmitted shear stress remained poorly investigated due to the lack of valid experimental approaches. Therefore, we created a magnetic shear strain device that enabled, for the first time, to analyze the instant shear strain response of human breast gland cells. MCF10A-derived breast acini with basement membranes (BM) of defined maturation state and basoapical polarization were used to resemble breast gland morphogenesis in vitro. The novel biophysical tool was used to apply cyclic shear strain with defined amplitudes (≤15%, 0.2 Hz) over 22 h on living spheroids embedded in an ultrasoft matrix (<60 Pa). We demonstrated that breast spheroids gain resistance to shear strain, which increased with BM maturation and basoapical polarization. Most intriguingly, poorly developed spheroids were prone to cyclic strain-induced extrusion of apoptotic cells from the spheroid body. In contrast, matured spheroids were insensitive to this mechanoresponse—indicating changing mechanosensing or mechanotransduction mechanisms during breast tissue morphogenesis. Together, we introduced a versatile tool to study cyclic shear stress responses of 3D cell culture models. It can be used to strain, in principle, all kinds of cell clusters, even those that grow only in ultrasoft hydrogels. We believe that this approach opens new doors to gain new insights into dynamic shear strain-induced mechanobiological regulation circuits between cells and their ECM.

Jak2 and Jaw Muscles Are Required for Buccopharyngeal Membrane Perforation during Mouth Development

“…In other developmental events, mechanical forces can activate several different signals such as the Hippo pathway or Piezo-regulated calcium channels [ 61 , 62 ]. These in turn can initiate cytoskeletal changes, downregulate adherens junctions, and induce apoptosis [ 62 , 63 , 64 , 65 , 66 , 67 ]. We demonstrate here that there are indeed apoptotic cells in the buccopharyngeal membrane just prior to perforation.…”

Jak2 and Jaw Muscles Are Required for Mouth Development

“…In other developmental events, mechanical forces can activate several different signals such as the Hippo pathway or Piezo regulated calcium channels to initiate cytoskeletal changes in the cells. Such changes then can in turn promote events such as apoptosis [52,53] and down regulation of adherens junctions [54], processes we know are critical in buccopharyngeal membrane rupture [1,2,55]. Alternatively, the forces generated by the muscles could physically pull apart the cells of the buccopharyngeal membrane.…”

Transformative Materials to Create 3D Functional Human Tissue Models In Vitro in a Reproducible Manner

“…Technical solutions include the formation of epithelial spheroidal acini and the growth of monolayers on defined material supports, exposing them to different environments at their apical and basal surfaces. [ 113 ] These setups can be used to study epithelial barrier dynamics in various biochemical and mechanical paradigms and how these affect invasions of the basal extracellular matrix, apical extrusion, and epithelial barrier breaching by microbes or immune cells during infection and inflammation or by embryonic trophectoderm cells during implantation. Questions that can be addressed with in vitro epithelium models are how and to what degree biochemical and mechanical stimuli affect epithelial differentiation and function.…”