Mechanocytometry Session:

Friday, September, 30th, 2022: 09:00 am

Chairs: Marta Urbanska and Oliver Otto

Integrating biophysical perspective into the description of cellular behaviors — typically studied from a biochemical angle — fosters comprehensive understanding of health and disease. In its broad understanding, mechanocytometry encompasses all methods that measure mechanical properties of the cells, such as stiffness or deformability. Classically, methods such as micropipette aspiration or atomic force microscopy-based indentation are used to characterize such properties. More recent developments aim at addressing challenges such as measuring of cell mechanical properties in situ in developing tissues (for example using Brillouin microscopy or intratissue bead sensors), or characterizing the mechanical properties of singles cells at high throughput in a flow cytometry-like manner (using a class of methods called deformability cytometry). The goal of measuring the mechanical properties of cells is to unravel their role in physiological and pathological processes such as tissue development and cancer metastasis, or to harness their potential as a diagnostic marker in various diseases. Our session will showcase new developments in the field of mechanocytometry, and present how cell mechanics can play a role in mammalian development and in breast cancer progression as ßstudied in 3D model systems with adaptable environment stiffness.

Chii Jou Chan

Mechanical control of mammalian ovarian folliculogenesis

Principal Investigator, Mechanobiology Institute, National University of Singapore, Singapore
Assistant Professor, Department of Biological Sciences, National University of Singapore, Singapore

Abstract

The formation of ovarian follicles that house the functional eggs (oocytes) is a critical process in mammalian development as it ensures successful reproduction and species propagation. While past molecular genetics studies have revealed genes that are critical for regulating the bidirectional communication between the oocyte and the somatic cells, the underlying mechanisms driving follicular growth remain enigmatic. Recent work suggests that follicle growth is sensitive to surrounding matrix stiffness, which calls for a need to understand cell-cell interactions within the follicle. Here, we investigate the mechanical functions of theca cells (TCs), which are the outer cells encapsulating the follicles. Using both in vivo staining and in vitro reconstitution assay, we demonstrate that the TCs are highly contractile and generate significant compressive stress to modulate follicle growth. TCs are also mechanosensitive and can modulate their proliferation rate and YAP signalling in response to cell stretch and substrate stiffness, suggesting that follicle growth or basement membrane stiffness may regulate TC functions in vivo. Finally, we found that the follicles are relatively compressible, and perturbing mechanical stress can influence somatic cell proliferation, oocyte signalling and growth. Overall, our data suggest that the interplay between tissue pressure and cell mechanics may control robust follicle morphogenesis and oocyte maturation through mechanotransduction pathways. These findings will have profound implications for future understanding and treatment of ovarian diseases and infertility.

Biosketch

Chii Jou (Joe) Chan studied theoretical physics at the University of Cambridge (B.A., M.Phil.), and received his doctorate from Cambridge on biophysical studies of cells and nuclei under the supervison of Prof. Jochen Guck. Inspired by how physical forces shape early development of living organisms, he joined the group of Dr. Takashi Hiiragi at EMBL Heidelberg, where he made a major discovery in hydraulic regulation of mouse embryo size and cell fate specification. Since 2021, Chan was a Principal Investigator at the Mechanobiology Institute at the National University of Singapore, where his lab investigates the biophysics and mechanobiology underlying ovarian follicular development and tissue hydraulics in mammalian ovaries, and their relevance in ovarian ageing and diseases. Chan has been awarded the Singaporean Teaching and Academic Research Talent Inauguration Grant in 2021. His interdisciplinary productivity is reflected in the diversity of his collaborators (cell and developmental biologists, experimental biophysicists, theorists) across the world.

Anna Taubenberger
Anna Taubenberger

Studying the mechanical and morphological phenotype of Cancer-associated fibroblasts of the prostate

Biotechnology Center, Technische Universität Dresden, Germany

Abstract
Reciprocal interactions between prostate epithelial cells and their adjacent stromal
microenvironment not only are essential for tissue homeostasis but also play a key role in tumor development and progression. Malignant transformation is associated with the formation of a reactive stroma where cancer-associated fibroblasts (CAFs) induce matrix remodeling and thereby provide atypical biochemical and biomechanical signals to epithelial cells. Previous work has been focused on the cellular and molecular phenotype as well as on matrix stiffness and remodeling, providing potential targets for cancer therapeutics. So far, biomechanical changes in CAFs and adjacent epithelial cells of the prostate have not been explored. Here, we compared the mechanical properties of primary prostatic CAFs and patient-matched non-malignant prostate tissue fibroblasts (NPFs) using atomic force microscopy (AFM) and real-time deformability cytometry (RT-FDC). We found that CAFs exhibit an increased apparent Young’s modulus, coinciding with an altered architecture of the cytoskeleton compared with NPFs. In contrast, co-cultures of benign prostate epithelial (BPH-1) cells with CAFs resulted in a decreased stiffness of the epithelial cells, as well as an elongated morphological phenotype, when compared with co-cultures with NPFs. Moreover, the presence of CAFs increased proliferation and invasion of epithelial cells, features typically associated with tumor progression. Altogether, this study provides novel insights into the mechanical interactions between epithelial cells with the malignant prostate microenvironment, which could potentially be explored for new diagnostic approaches.

Biosketch
Since 2020 I have been a group leader at the Biotechnology Center of the TU Dresden. I have a background in bioengineering with more than 10 years research experience in the biophysics field. Over the past years I could contribute to a better understanding of cell and tissue mechanics and changes associated with disease. My group, supported by the Mildred Scheel Early Career Center Dresden, currently focuses on mechanical tumor cell- microenvironment interactions. To study the role of cancer cell and microenvironment mechanics on cancer cell growth, invasion and metastasis, we employ different tools in the lab, e.g. atomic force microscopy (AFM), realtime deformability cytometry (RT-DC), and Brillouin microscopy. Besides mechanical characterization of patient tumour samples, bioengineered 3D in vitro models are developed to systematically study the influence of microenvironment stiffness on cancer cell behaviour. In particular, mechanisms by which cells sense
and adapt to their mechanical environment in 3D are explored and how this can be potentially used for new diagnostic approaches. I have (co-)authored more than 50 publications in peer-reviewed (h-index = 32) with over 3,493 citations.