Dissecting the role of matrix stiffness and composition for macrophage function in ovarian ageing

• Applicant: Anna Jaeschke, Ph.D.
• Subject Area: Cell Biology ; Biophysics ; Developmental Biology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 521343357

The ageing of the female reproductive system results in decreased fertility due to a decline in follicle number and oocyte quality. In the tissue context, follicles are embedded in an extracellular matrix and surrounded by various cell types. Reciprocal cell-cell and cell-matrix interactions are crucial for tissue homeostasis but are also involved in ageing and diseases. Ovarian ageing is accompanied by significant changes in the tissue characteristics, such as increased stiffness, altered matrix composition and aberrant signalling molecules, collectively resulting in chronic tissue inflammation. These changes in the microenvironment have significant impacts on the molecular and cellular phenotype of the ovarian tissue. This project aims to study how the alterations of the ovarian tissue that occur during ageing affect macrophage function. Studying macrophages is of interest due to their critical roles in inflammatory responses and their involvement in tissue homeostasis. Macrophages residing in the ovary can be derived from two different origins: tissue-resident macrophages (TRMs) that arise from embryonic progenitor cells and macrophages derived from monocytes that migrate to the tissue upon injury and inflammation. It is unclear whether the monocyte-derived macrophages can fully recapitulate the function of ovarian TRMs. Notably, monocyte-derived macrophages have been shown to contribute significantly to matrix remodelling and fibrosis. First, I will study how monocyte-derived macrophages and TRMs respond to changes in their surrounding matrix. I will develop matrices that mimic young and aged matrix stiffness and composition in vitro utilising a 3D hydrogel with tuneable elastic modulus and molecular components. Cell survival, migration, and molecular phenotype of TRMs and bone marrow-derived macrophages (BMDMs) will be compared in response to culture in the hydrogels. Next, I will study how changes in macrophage paracrine signalling affects matrix deposition by fibroblasts in vitro. Fibroblasts will be exposed to secreted factors collected from the macrophages grown in the hydrogels. The characteristics of the fibroblast-derived matrices will be a functional readout for macrophage-mediated fibrosis. Eventually, the biophysical properties of macrophages will be explored as a potential key factor for cells adapting to their microenvironment. Atomic force microscope and real-time deformability cytometry will be utilized to study cell mechanical properties in response to matrix stiffness and composition. Ultimately, the mechanical phenotype will be linked to the molecular and functional phenotype to understand better the implications of matrix characteristics for macrophage function. Overall, this research will provide novel insights how ovarian TRMs and monocyte-derived macrophages respond to signalling cues from their surrounding matrix, and the implications for fibrosis through crosstalk with other stroma cells.

• DFG Programme: WBP Fellowship
• International Connection: Singapore
• Host: Professor Dr. Chii Jou Chan