Mechanosensitive structures in epithelial integrity

Force-producing actomyosin bundles are required for the maintenance of intracellular tension at cell-cell junctions and cell-substrate interface of immotile epithelial sheets. Through their connections to both integrin-and cadherin-based cell adhesion sites, these mechanosensitive structures also sense changes in their physical environment and adjust cellular contractility in order to maintain a force-equilibrium with the surroundings. During neoplastic progression, abnormal regulation of these mechanosensitive structures may cause a force-imbalance between the cell and its environment, possibly creating favourable conditions for the transformed cells to escape from the primary tumor site. In our research, we are focusing on the mechanosensitive signaling pathways that regulate the assembly and maintenance of actomyosin structures and trying to find out how alterations in these pathways triggers scattering of the transformed epithelial cells. Additionally, we are trying to understand how the detached cancer cells utilize these aberrantly regulated actin-based structures in intruding to the surrounding tissues. In these studies we utilize several human and canine cell lines and manipulation of 2D and 3D cultures combined with advanced imaging methods.

In the image: MDCK, canine kidney epithelial monolayer, Actin-blue, P-MLC-green, DAPI-red

 

In­ter­play with stromal and epithelial cells

Currently it is understood that cancer cells do not invade without the help of their stroma. Stromal cells undergo significant changes in their gene-expression profiles along cancer progression, signal abnormally to epithelial cells and may modify the micro-environment more permissive to cancer cell invasion. This abnormal stromal impact may induce invasive cellular features in transformed cells through their actomyosin machinery. We are currently investigating the role of stromal adipocytes in this process. Despite the fact that these cells are the most abundant cells in the mammary gland and excess adipose tissue has a clear connection to breast cancer progression, these cells are still understudied. Besides cancer progression, obesity is linked to several other disease and these studies could also reveal links in between adipose-derived signaling and other pathological conditions. In our studies we utilize both human cell lines and canine-derived adipose tissue samples, advanced 3D cultures combined with imaging as well as proteomic screens.

 

In the Image: Primary carcinosarcoma sample from the mammary gland of canine, containing epithelial cell population and fibroblasts

 

Bio­phys­ical changes of the microenvironment in disease progression

Altered biophysical features of the extracellular matrix, such as increased stiffness, changes in the composition and architectural features of the matrix, are associated with several common diseases. Tissue homeostasis, due to abnormal stroma, is for example linked to invasive carcinomas, cardiovascular diseases, airway diseases and fibrosis. In most solid tumors cancer cells are exposed to major stiffening of the stroma. Rigid environment may activate specific mechanosensitive pathways with subsequent alterations in the actomyosin bundles. As increasing stiffness strongly correlates with the development of invasive breast cancer, biophysical environment could promote invasive disease through the generation of abnormal cellular forces. In our studies, we aim in understanding how specific changes in the biophysical cell microenvironment plays a role in the regulation of force-producing actomyosin bundles and how they could be linked to scattering of the epithelial cells. Althoug we utilize human and canine mammary epithelial material in these studies, the impact of stromal changes in the maintenance of epithelial homeostasis most likely has overlapping features in distinct tissues. In the experiments we utilize shape-and stiffness-determined 3D culture setups, which allows us to manipulate specific mechanical features in the culture environment.

 

 

In the Image: Mammary spheroids formed by breast epithelial cells in compliant matrix

Myoepithelial cells in the maintenance of tubular homeostasis

Tubular tissue structures such as airways, gastrointestinal tract, vasculature, and exocrine glands are involved in a number of highly pathological conditions. In vivo, these tubular structures are maintained by mechanical features of the outer cell layer consisting of smooth muscle- or myoepithelial cells. This contractile layer is controlled by mechanotransduction pathways that themselves are coordinated by the physical changes both in the luminal and stromal compartments. Our studies on mammary myoepithelial cells aim in deeper understanding on the molecular mechanisms that determine the response of this contractile layer upon physical cues from the environment: How is the mechanotransduction machinery activated and how is the cytoskeletal network responding to maintain tubular homeostasis. As myoepithelial cells have been suggested to constrain spreading of luminal carcinoma cells, our studies with patient samples may reveal important mechanical changes within the myoepithelial layer that makes it permissive to invasion. Additionally, the principle mechanisms regulating different tubular structures are most likely overlapping and these studies may also shed a light on the homeostasis of other tubular systems. In these studies we utilize human primary myoepithelial cells as well as canine patient material from different stages of mammary carcinomas, advanced 3D culture setups and imaging.

In the image: Smooth muscle actin (SMA) staining of a paraffin-embedded normal canine mammary gland tissue slice