Final Report Summary - CYTOANCHOR (Actin–membrane anchoring in giant liposomes: a biomimetic system to study cell mechanics)
OVERVIEW
This Marie Curie IIF fellowship has been highly successful to me, both in terms of scientific output as well as in developing my personal qualities as a young researcher.
The originally proposed project was aimed to uncover how (biological) cells are able to physically interact with their environment, using a bottom-up approach of artificial cells with minimal biochemical ingredients. During the period of the fellowship, I increasingly realized that to obtain a holistic understanding, it is necessary to investigate the structural and mechanical roles of protein biopolymers in cells and tissues. To do so, I geared the project to focus on the three different levels of the problem: the extracellular matrix environment (with fibrin as the model system), the intracellular cytoskeleton (particularly actin), and the cell itself. These projects can therefore be broadly categorized into fibrin-related, actin-related, and cell-related projects. The results from the projects have yielded important insights into the structure–property relations in these biomaterials. Parts of the results have been published in scientific journals and disseminated through international meetings, and several additional publications are in the pipeline, as will be described in more detail below.
The fellowship has thus greatly contributed to my personal development as an independent researcher. Moving forward, I am excited to pursue my scientific aspiration as well as my passion in education, and I have accepted a new position as an Assistant Professor at Eindhoven University of Technology, Eindhoven, the Netherlands, starting from 1 August 2015. I will join a strong Biomedical Engineering Department there, working on cell biophysics and tissue engineering, particularly in the context of cardiovascular biomechanics. This will give me a perfect opportunity to establish myself as an independent investigator not only for understanding the fundamental science of mechanobiology but also for directly applying the knowledge in biomedical and clinical applications
A. Fibrin project
The overall goal of this project is to unravel the structural origins behind the extraordinary elastomeric and mechanical resilience of fibrin, the scaffold of blood clots. I discovered and explored a number of intriguing properties of fibrin, leading to several sub-projects and collaborative works that have been very fruitful. Some highlights:
• I discovered that during the formation and maturation of fibrin clots, a gradual fiber compaction process takes place, which can explain the stiffening of the clot as well as its susceptibility to degradation. These stiffening and degradation, in turn, are crucial for normal blood clotting and hemostasis. Collaborations: Dr. J. Koopman and Dr. J. Grimbergen (ProFibrix BV, the Netherlands).
• I showed that the mechanical properties of fibrin at small and large deformations can be fully explained and quantitatively predicted by a theoretical model for bundled semiflexible polymers. Importantly, this agreement paves the way for future rational design of networks (of fibrin or other biopolymers) with desired mechanical properties. Moreover, I found an intriguing behavior of fibrin to retain mechanical memory upon cyclic deformation, which turns out to arise from its ability to structurally adapt to applied stresses. Collaboration: Prof. D. Bonn (University of Amsterdam, the Netherlands), Prof. G.J.L. Wuite, Prof. E.J.G. Peterman, and Prof. F.C. MacKintosh (VU University, the Netherlands).
• I discovered that the formation process of fibrin is surprisingly sensitive not only to the buffering agent, which is usually regarded as inert, but also to various small solutes. This effect is manifested in the bundling kinetics of the fibers and the evidence suggests that this may be mediated by hydrogen bonds that facilitate lateral fiber associations. As such, this is likely to be a universal physicochemical effect that can provide insight into the aggregation mechanisms of other biopolymers such as actin, collagen, and amyloids. Further work is underway to establish the molecular origins of this effect, both using experimental and simulation approaches. Collaborations: Prof. J.W. Weisel (University of Pennsylvania, USA), Prof. V. Barsegov (University of Massachusetts Lowell, USA), Prof. A. Zhmurov (Moscow Institute of Physics and Technology), Prof. L. Medved (University of Maryland, USA), and Prof. H.J. Bakker (AMOLF, the Netherlands).
This project will be further pursued in the host laboratory by a new postdoc, who will be funded by the Dutch government through the “Topsectoren” initiative.
B. Actin project
The overall goal of this project is to understand how dynamics of actin at the filament level translates to the activity and properties of actin at the network level. This project is also sub-divided into a few sub-projects. Some highlights:
• I showed that the softening behavior of solutions of actin filaments, which is thought to be important during cell shape change and cytoplasmic flows, is caused by alignment of filaments in the direction of the flow and loss of entanglement between the filaments, without filament damage. This resolved a long-standing puzzle in the community and, more generally, provides insights into the flow behavior of solutions of semiflexible filaments, including in consumer products. Collaboration: Prof. M.P. Lettinga (Forschungzentrum Jülich, Germany).
• I started to explore how the nature of cross-linker affects the contractility dynamics and rupture behavior of active and passive actin networks. Preliminary results suggest that different actin cross-linkers with different binding affinities and molecular structures lead to qualitatively different contractility and rupture dynamics. This is particularly relevant in cells, where various actin-binding and accessory proteins have been identified.
This project is currently further pursued in the host laboratory by a PhD student and a postdoc.
C. Cell project
The overall goal of this project is to understand how physical, mechanical, and biochemical signals from within the cell and from the extracellular environment are integrated by the cell, resulting in observable cellular behavior. I specifically focused on the migration behavior of individual cells, particularly in the context of cancer invasion. Collaboration: Prof. C.T. Lim (Mechanobiology Institute, Singapore). Some highlights:
• I discovered that the migration behavior of cells is strongly dependent on the local properties of the immediate microenvironment. Importantly, these local properties can at the same time be modulated, both physically and biochemically, by the cells, creating a feedback loop that can facilitate cell invasion.
• I showed that the efficacy of anti-migratory drugs is strongly affected by the matrix condition. The converse is also true: different drugs have different efficacies with the same matrix condition. This finding has broad implications in the field of drug discovery, especially in the case of cancer metastasis, and provides practical guidelines for future drug screening strategies.
SOCIO-ECONOMIC IMPACTS
These projects will have an impact on biotechnology, materials science, and biomedical engineering, given the direct applicability of the findings for the creation of bioinspired materials and tissue-like matrices with defined properties and biocompatibility, for example for tissue engineering/repair purposes. The valorization of this project, that is, its translation from basic research into practical applications, will be enhanced by the active concern that the host institution, AMOLF, has in cooperating with industry, as expressed in its mission statement and proved by the active collaborations established with industrial companies (i.e. Philips, Unilever, Shell). The technological and biomedical applications derived from this project can potentially give rise to long-term synergies between the host institute and biomedical/engineering companies, likely to have a relevant structuring effect in the European economy.
This Marie Curie IIF fellowship has been highly successful to me, both in terms of scientific output as well as in developing my personal qualities as a young researcher.
The originally proposed project was aimed to uncover how (biological) cells are able to physically interact with their environment, using a bottom-up approach of artificial cells with minimal biochemical ingredients. During the period of the fellowship, I increasingly realized that to obtain a holistic understanding, it is necessary to investigate the structural and mechanical roles of protein biopolymers in cells and tissues. To do so, I geared the project to focus on the three different levels of the problem: the extracellular matrix environment (with fibrin as the model system), the intracellular cytoskeleton (particularly actin), and the cell itself. These projects can therefore be broadly categorized into fibrin-related, actin-related, and cell-related projects. The results from the projects have yielded important insights into the structure–property relations in these biomaterials. Parts of the results have been published in scientific journals and disseminated through international meetings, and several additional publications are in the pipeline, as will be described in more detail below.
The fellowship has thus greatly contributed to my personal development as an independent researcher. Moving forward, I am excited to pursue my scientific aspiration as well as my passion in education, and I have accepted a new position as an Assistant Professor at Eindhoven University of Technology, Eindhoven, the Netherlands, starting from 1 August 2015. I will join a strong Biomedical Engineering Department there, working on cell biophysics and tissue engineering, particularly in the context of cardiovascular biomechanics. This will give me a perfect opportunity to establish myself as an independent investigator not only for understanding the fundamental science of mechanobiology but also for directly applying the knowledge in biomedical and clinical applications
A. Fibrin project
The overall goal of this project is to unravel the structural origins behind the extraordinary elastomeric and mechanical resilience of fibrin, the scaffold of blood clots. I discovered and explored a number of intriguing properties of fibrin, leading to several sub-projects and collaborative works that have been very fruitful. Some highlights:
• I discovered that during the formation and maturation of fibrin clots, a gradual fiber compaction process takes place, which can explain the stiffening of the clot as well as its susceptibility to degradation. These stiffening and degradation, in turn, are crucial for normal blood clotting and hemostasis. Collaborations: Dr. J. Koopman and Dr. J. Grimbergen (ProFibrix BV, the Netherlands).
• I showed that the mechanical properties of fibrin at small and large deformations can be fully explained and quantitatively predicted by a theoretical model for bundled semiflexible polymers. Importantly, this agreement paves the way for future rational design of networks (of fibrin or other biopolymers) with desired mechanical properties. Moreover, I found an intriguing behavior of fibrin to retain mechanical memory upon cyclic deformation, which turns out to arise from its ability to structurally adapt to applied stresses. Collaboration: Prof. D. Bonn (University of Amsterdam, the Netherlands), Prof. G.J.L. Wuite, Prof. E.J.G. Peterman, and Prof. F.C. MacKintosh (VU University, the Netherlands).
• I discovered that the formation process of fibrin is surprisingly sensitive not only to the buffering agent, which is usually regarded as inert, but also to various small solutes. This effect is manifested in the bundling kinetics of the fibers and the evidence suggests that this may be mediated by hydrogen bonds that facilitate lateral fiber associations. As such, this is likely to be a universal physicochemical effect that can provide insight into the aggregation mechanisms of other biopolymers such as actin, collagen, and amyloids. Further work is underway to establish the molecular origins of this effect, both using experimental and simulation approaches. Collaborations: Prof. J.W. Weisel (University of Pennsylvania, USA), Prof. V. Barsegov (University of Massachusetts Lowell, USA), Prof. A. Zhmurov (Moscow Institute of Physics and Technology), Prof. L. Medved (University of Maryland, USA), and Prof. H.J. Bakker (AMOLF, the Netherlands).
This project will be further pursued in the host laboratory by a new postdoc, who will be funded by the Dutch government through the “Topsectoren” initiative.
B. Actin project
The overall goal of this project is to understand how dynamics of actin at the filament level translates to the activity and properties of actin at the network level. This project is also sub-divided into a few sub-projects. Some highlights:
• I showed that the softening behavior of solutions of actin filaments, which is thought to be important during cell shape change and cytoplasmic flows, is caused by alignment of filaments in the direction of the flow and loss of entanglement between the filaments, without filament damage. This resolved a long-standing puzzle in the community and, more generally, provides insights into the flow behavior of solutions of semiflexible filaments, including in consumer products. Collaboration: Prof. M.P. Lettinga (Forschungzentrum Jülich, Germany).
• I started to explore how the nature of cross-linker affects the contractility dynamics and rupture behavior of active and passive actin networks. Preliminary results suggest that different actin cross-linkers with different binding affinities and molecular structures lead to qualitatively different contractility and rupture dynamics. This is particularly relevant in cells, where various actin-binding and accessory proteins have been identified.
This project is currently further pursued in the host laboratory by a PhD student and a postdoc.
C. Cell project
The overall goal of this project is to understand how physical, mechanical, and biochemical signals from within the cell and from the extracellular environment are integrated by the cell, resulting in observable cellular behavior. I specifically focused on the migration behavior of individual cells, particularly in the context of cancer invasion. Collaboration: Prof. C.T. Lim (Mechanobiology Institute, Singapore). Some highlights:
• I discovered that the migration behavior of cells is strongly dependent on the local properties of the immediate microenvironment. Importantly, these local properties can at the same time be modulated, both physically and biochemically, by the cells, creating a feedback loop that can facilitate cell invasion.
• I showed that the efficacy of anti-migratory drugs is strongly affected by the matrix condition. The converse is also true: different drugs have different efficacies with the same matrix condition. This finding has broad implications in the field of drug discovery, especially in the case of cancer metastasis, and provides practical guidelines for future drug screening strategies.
SOCIO-ECONOMIC IMPACTS
These projects will have an impact on biotechnology, materials science, and biomedical engineering, given the direct applicability of the findings for the creation of bioinspired materials and tissue-like matrices with defined properties and biocompatibility, for example for tissue engineering/repair purposes. The valorization of this project, that is, its translation from basic research into practical applications, will be enhanced by the active concern that the host institution, AMOLF, has in cooperating with industry, as expressed in its mission statement and proved by the active collaborations established with industrial companies (i.e. Philips, Unilever, Shell). The technological and biomedical applications derived from this project can potentially give rise to long-term synergies between the host institute and biomedical/engineering companies, likely to have a relevant structuring effect in the European economy.