Periodic Reporting for period 1 - MACxercise (Dissecting Macrophage Mechanobiology to Engineer Immuno-Regenerative Biomaterials)
Berichtszeitraum: 2022-06-01 bis 2024-11-30
As the demand for advanced medical implants continues to grow, the exciting field of implant technology is evolving quickly. One of the key challenges we face is to harness the body’s immune response to such implants in order to improve effective integration into the body in a way that ensures long-term functionality of the implant. In this research, we use the body’s immune response to our advantage; we develop biodegradable synthetic biomaterials that, once implanted, are gradually degraded by the immune system and replaced by the body's own living tissue. Among the vital players in this process are macrophages, which are immune cells that control both the degradation of a biomaterial and the formation of new tissue by the body. It is known that the response of macrophages to a biomaterial is dependent on the properties and structural design of an implant. However, a critical aspect that is largely overlooked is how macrophages sense and respond to mechanical loads, such as cyclic stretch —a fascinating area known as 'macrophage mechanobiology.’. Mechanical loads are omnipresent in the body (e.g. due to breathing, heart beat), and highly sought-after medical implants, such as cardiovascular implants (e.g. heart valve replacements), are continuously exposed to such mechanical loads. The lack of understanding of the role of mechanical loads on the immune response to implants has led to unpredictable results. The overall goal of this project is to systematically unravel macrophage mechanobiology and to predict its role in biomaterial degradation and tissue regeneration. This is done by identifying through which cellular components of the macrophage the cell senses the mechanical environment and triggers a change in function. Subsequently, we will use this knowledge to study how macrophages contribute to biomaterial degradation and new tissue formation, and to decouple the influence of mechanical loads from other stimuli in the environment, such as signaling molecules. This is achieved by using a combination of innovatively engineered experimental and numerical models. The results of this project will enable rational design of regenerative medical implants, instead of less effective trial-and-error approaches.
A primary goal is to distinguish mechanical and morphological signals affecting macrophage mechanobiology at the cellular level in 2D and 3D. Changes in macrophages often relate to their mechanical behavior, indicating cytoskeletal dynamics, morphology, and adhesion modifications. We employed polyacrylamide gels with variable stiffness to investigate cytokine secretion, degradation, and uptake responses to differentiate mechanical stimuli from cellular characteristics across activation states. Through AFM measurements at the single-cell level, we found that the activation state of primary human macrophages influences their mechanical properties, including stiffness and viscosity. We also analyzed how mechanical environment variations impacted cellular mechanics and functions. Force spectroscopy showed that cells on low-stiffness substrates were stiffer than those on high-stiffness ones, significantly affecting macrophage phenotype as confirmed by qPCR. These results so far underline that macrophages respond to their mechanical environment. The next step will be to combine changes in the mechanical environment with cell morphological and biochemical signals to identify dominant pathways.
The second key goal is to address macrophage-driven tissue regeneration affected by transient mechanical loads. We concentrate on the functional outcomes arising from alterations in cell mechanics and morphology due to these dynamic loads. At the cellular level, we developed effective culture methods for foreign body giant cells (FBGCs) derived from human peripheral blood and characterized their properties. Following the establishment of FBGC culture methods, we subjected these cells to cyclic stretch to examine their functional responses regarding cytokine secretion, trophic factors, and degradative factors, including reactive oxygen species.
To translate the findings regarding macrophage mechanobiology at the fundamental level to an application, we developed a multi-scale computational model for macrophage-driven tissue regeneration, focusing on regenerative heart valves as a critical application. We have used a computational approach to characterize the mechanical environment in heart valve tissue engineering. The computed stresses and strains were correlated with local expression levels of immunohistochemical markers. Data collected from implants and explants in our previous one-year in vivo study showed a significant correlation between stresses, strains, and immunohistochemical markers, underlining the relevance of the work in an application.
The second key goal is to address macrophage-driven tissue regeneration affected by transient mechanical loads. We concentrate on the functional outcomes arising from alterations in cell mechanics and morphology due to these dynamic loads. At the cellular level, we developed effective culture methods for foreign body giant cells (FBGCs) derived from human peripheral blood and characterized their properties. Following the establishment of FBGC culture methods, we subjected these cells to cyclic stretch to examine their functional responses regarding cytokine secretion, trophic factors, and degradative factors, including reactive oxygen species.
To translate the findings regarding macrophage mechanobiology at the fundamental level to an application, we developed a multi-scale computational model for macrophage-driven tissue regeneration, focusing on regenerative heart valves as a critical application. We have used a computational approach to characterize the mechanical environment in heart valve tissue engineering. The computed stresses and strains were correlated with local expression levels of immunohistochemical markers. Data collected from implants and explants in our previous one-year in vivo study showed a significant correlation between stresses, strains, and immunohistochemical markers, underlining the relevance of the work in an application.
An essential advancement is the application of AFM technology to primary human macrophages. This technology provides a unique opportunity to characterize macrophage mechanics and function at the (sub)cellular level. Our interdisciplinary team enables us to leverage experimental data to create a hierarchical model of human macrophage mechanics, marking a significant advancement in the field. Ultimately, we aim to use this data and methodology to develop, for the first time, a mechanical model of the human macrophage, which would represent a major breakthrough in the field of macrophage mechanobiology.
Additionally, we established standardized cultures for primary human macrophages and foreign body giant cells (FBGCs). Due to the cells' sensitivity to environmental factors, methodological inconsistencies in existing literature led to varying results. A systematic review of methodologies has produced standardized protocols vital for the ERC project and the broader community. Despite their importance in medical grafts, original research on FBGCs could be more extensive, highlighting our contribution. Establishing this methodology has now enabled us to for the first time systematically study human FBGCs in dynamic conditions. This represents an essential advancement when aiming to develop regenerative implants for mechanically loaded applications, which is a highly active area of research.
Lastly, we progressed in developing regenerative heart valve prostheses. We detailed the regenerative process in high-pressure aortic circulation for the first time. Although previous research consortia completed most valve development, our ERC team advanced by characterizing local inflammatory processes and their link to scaffold resorption and tissue formation. We are currently developing a predictive model of heart valve regeneration in order to enable rational implant design.
Additionally, we established standardized cultures for primary human macrophages and foreign body giant cells (FBGCs). Due to the cells' sensitivity to environmental factors, methodological inconsistencies in existing literature led to varying results. A systematic review of methodologies has produced standardized protocols vital for the ERC project and the broader community. Despite their importance in medical grafts, original research on FBGCs could be more extensive, highlighting our contribution. Establishing this methodology has now enabled us to for the first time systematically study human FBGCs in dynamic conditions. This represents an essential advancement when aiming to develop regenerative implants for mechanically loaded applications, which is a highly active area of research.
Lastly, we progressed in developing regenerative heart valve prostheses. We detailed the regenerative process in high-pressure aortic circulation for the first time. Although previous research consortia completed most valve development, our ERC team advanced by characterizing local inflammatory processes and their link to scaffold resorption and tissue formation. We are currently developing a predictive model of heart valve regeneration in order to enable rational implant design.