RESEARCH
Biophysics, mechanobiology, and biology in health and disease
Our vision is to understand the interplay between biophysics and immunology.
Biomedical sciences increasingly recognise the importance of biophysics in health and disease. For the most part, this is due to an emerging new perspective of the broad impact of mechanobiology on the human immune response. While most mechanisms of the immune response are adequately explained by cell-biology, biochemistry, and genetics, many of its features profoundly depend on biomechanical aspects.
The Biophysical Immunology (BPI) laboratory aims to unravel the impact of these mechanobiological aspect on the human immune system in health and disease. We are especially interested in the understanding of the significance of a vital cellular cytoskeleton, the primary determinant of immune cell biophysics.
Having expertise across multiple disciplines from theoretical-physics to immunology, the BPI group is determined to investigate contentious biomedical research. For our quantitative approach we establish and apply new advanced technology with the biology-demanded sensitivity. Long-term goal of our research is the translation of mechanobiology to mechanomedicine in diagnostics and treatment of patients.
Mechanical forces underpin immune cell homeostasis
Cellular interactions are often ruled by physical changes due to motion, so-called mechanical force. Such forces are involved during molecular rearrangements and most obviously when cells form close contacts, avoid each other, or reshape to change morphology. Mechanobiology focuses on the quantitative study of these mechanical forces in living cells in the context of health and disease.
A new perspective of mechanobiology is currently emerging across multiple disciplines. In contrast to conventional beliefs, recent evidence indicates that immune cells regulate their cell mechanics not only downstream of signalling events triggered by external stimuli, but that these cells employ a diversity of feedback mechanisms enabling them to dynamically adjust their mechanics to meet physiological needs. Consequently, this provides an previously unforeseen picture wherein immune cells actively exert and resist biomechanical force to tune their mechanobiology and thus facilitate their function, which is particularly important during the profound three-dimensional interactions in between immune cells or with their tissue micro-environment.
Advanced technology development and innovation
Bioimaging is rapidly moving forward with experimentations and the utilisation of living systems largely due to the establishment of new technology. These new cutting-edge imaging methodologies underpin a significant proportion of life science research in the biomedical disciplines. Historically, advances in understanding mechanisms of mechanobiology underlying key events of cytoskeletal actin organisation and their impact on immune cell function have been driven by innovations in technologies, that provide greater spatial and temporal sensitivity coupled to appropriate cell-biological, immunochemical, and genetic tools. However, existing technologies often do not provide the right sensitivity for the quantitative imaging of immune cell homeostasis.
Quantifying cellular mechanics has therefore become an important mission across multiple disciplines at the interface of bioengineering , biophysics, and immunology in the biomedical sciences. These efforts focus on the quantification of mechanics of single immune cells, cell-cell contact, and cellular interactions with the microenvironment.
To uncover the importance and broad impact of mechanobiology in health and disease, we therefore establish and apply novel biophysical tools, force probing, high-throughput technologies by utilising advanced and live-cell super-resolution microscopy modalities.
Research environment
The Biophysical Immunology (BPI) group led by Assoc Prof Marco Fritzsche is located at the Kennedy Institute for Rheumatology (KIR) at the University of Oxford and the Rosalind Franklin Institute in the UK. We also support a research lab within the MRC Human Immunology Unit (HIU) at the Weatherall Institute of Molecular Medicine (WIMM), UK.
The BPI group is associated to the Micron Oxford Advanced Bioimaging Unit and works in close collaboration with the Immunological-synapse-group of Professor Michael Dustin and the Biophysical-imaging-group of Professor Christian Eggeling located at the Leibniz Institute for Photonics at the Friedrich-Schiller University in Jena, Germany.
Research aims and objectives
Primary research aim is the identification and characterisation of mechanobiological mechanisms controlling immune cell activation in health and disease. Our objectives therefore involve the application and development of novel ultrasensitive, live-cell super-resolution microscopy techniques with spatiotemporal sensitivity down to the nanoscale, superior to conventional optical microscopes. Long-term goal of our research is the translation of our expertise and methodologies in mechanobiology to mechanomedicine in diagnostics and treatment of patients.
Research focus: Nanoscale mechanical forces
Cell generated mechanical forces are emerging as a key regulator of biological function. Traction force microscopy (TFM) is perhaps the most widely used mechanical force probing methodology, owing to its versatility in mimicking biological and mechanical conditions. The accuracy and resolution of TFM depends on the microscopy modality with which the technique is applied. While the frequency of temporal sampling influences the referencing and trackability of the fiducial markers over time, the spatial resolution of the force field depends on the density at which information within the displacement field can be sampled.
One shortcoming of classical TFM is therefore its limited sensitivity due to the finite density at which the displacement field can be sampled within the gel, which must be high enough to reflect the complexity of the traction field that is applied by the cell.
To overcome these challenges of classical TFM, we recently improved the spatial resolution and accuracy of TFM using optical super-resolution stimulated emission depletion (STED) and structural illumination (SIM) microscopy. The increased spatial resolution of (STFM) allows a greater than five-fold higher sampling of the forces generated by the cell than conventional TFM, thus enabling live-cell quantification of nanoscale mechanical forces approaching physiological sensitivity.
Please see detailed information for the development and application of the STFM.
Schematic of TFM experiments. Living cells are interacting with a functionalised mechanical-tunable hydrogel with fluorescent impeded beads placed on a glass coverslide.
Research focus: Mechanisms of cytoskeletal actin organisation
Little is also known about the mechanisms controlling the organisation and dynamics of cytoskeletal actin structures in space and time in living immune cells.
Two fundamentally different mechanisms exist to generate actin networks: self-assembly and self-organisation. Self-assembly involves the physical association of motor proteins to actin, for instance, to assemble actin filaments into equilibrium networks. Self-organised actin networks are at steady state kept far from equilibrium by the constant input of energy. They arise solely through the local physical interactions of actin filaments initiated by a spontaneous instability such as symmetry breaking events, for example, when actin-polymerisation dynamics or intrinsic mechanical stress of actin networks spontaneously change.
Conclusive understanding of these rearrangements involves the tight coupling between biochemical and physical properties of three components of the actin cytoskeleton: (i) actin kinetics: actin protomer association/dissociation into filamentous actin (F-actin); (ii) actin dynamics: the assembly of filaments into actin structures; and (iii) mechanics: the cytoskeleton generates, senses, and transmits mechanical forces.
Cell-free studies involving computer-simulations and experiments in vitro have previously demonstrated how collective action of actin-associated proteins can organise actin filaments into dynamic patterns, such as vortices, asters and stars.
We have recently shown evidence of such self-organisation of the actin cortex in living cells. During cell adhesion, an active multistage process naturally leads to pattern transitions from actin vortices over stars into asters. The organisaiton of actin filaments (green in the video) is primarily driven by Arp2/3 complex (orange in the video) nucleation, but not by myosin motors, which is in contrast to what has been theoretically predicted and observed in vitro.
Research foucs: Calcium signalling in the immune response
As a second messenger, calcium plays a vital role in relaying information from cell-surface receptors into changes in cellular mechanisms, including cytoskeletal rearrangement. In T cells, calcium signalling is a key aspect in its development, survival, and activation. Given the transient, dynamic nature of calcium, a high temporal resolution is crucial in measuring calcium levels over time. And, while such studies have been done, they are typically done with only a few cells at a time. Because calcium responses can be heterogeneous between , it is imperative to measure many cells at once while still depicting individual calcium levels. CalQuo2 is recently updated user-friendly, MATLAB based software that can robustly analyses calcium patterns of individual cells within hundreds to thousands of cells that have been captured using fluorescence microscopy. Please see detailed information for the development and application of the calcium analysis software CalQuo.
