Award details

Mechno-regulation of genome function to direct stem cell fate

Reference	BB/N018532/1
Principal Investigator / Supervisor	Professor David Alan Lee
Co-Investigators / Co-Supervisors	Dr Nuria Gavara, Dr Stephen Thorpe
Institution	Queen Mary University of London
Department	School of Engineering & Materials Scienc
Funding type	Research
Value (£)	436,194
Status	Completed
Type	Research Grant
Start date	01/01/2017
End date	31/12/2019
Duration	36 months

Abstract

Bone marrow derived mesenchymal stem cells (MSCs) provide a promising cell source for a range of regenerative medicine therapies. We have preliminary data indicating that nuclear architecture and cell and nuclear mechanical properties change significantly with differentiation, and are further modulated by biophysical stimulation. We hypothesise that the nucleus as a mechanosensor in the biophysical regulation of stem cell fate. This project aims to determine the factors behind differentiation-induced alterations to the MSC mechano-phenotype. We will compare human MSCs with and without biophysical stimulation before and after differentiation to elucidate biomechanical, compositional and structural differences in nuclear architecture and the LINC (Linker of cytoskeleton and nucleoskeleton) complex which may modulate mechanosensitivity and cell mechanics. Analysis of nuclear strain transfer in conjunction with cytoskeletal and nuclear architecture modulation will enhance our understanding of mechanotransduction mechanisms within the cell. Quantitative proteomic analysis will characterise changes in cytoplasmic and nuclear composition with differentiation allowing us to identify potential targets responsible for the modulation of mechanosensitivity. Quantitative data on force transfer across the LINC complex from a nesprin force sensor will provide unique insights into how nuclear mechanoregulation changes with differentiation. Finally, characterisation of biophysically induced epigenetic alterations will identify the mechanisms through which repeated biophysical stimulation can instil an epigenetic mechanical memory within the nucleus.

Summary

A growing number of pathological conditions are associated with inappropriate or defective cellular sensing of their mechanical environment. Adult mesenchymal stem cells (MSCs) provide a promising cell source for many regenerative therapies although relatively little is known concerning the mechanisms through which mechanical stimuli are transduced into regulatory signals within the cell. Cellular behaviour is largely regulated by gene expression, which is directed from within the nucleus through transcription of DNA. DNA is packaged within the nucleus as chromatin. The compaction state of chromatin impacts gene transcription, and can result in gene silencing. This compaction state is controlled by a number of histone proteins, and is further influenced by the nuclear lamina, a fibrillar matrix within the nucleus lining the inner nuclear membrane. This controls gene silencing in DNA situated near the edge of the nucleus, and is connected via a complex of proteins (the LINC complex) to the cytoskeleton; the cells skeleton which provides the cell with structure. During stem cell differentiation, the nucleus has been shown to remodel, with alterations to nuclear stiffness and the nuclear lamina; potentially influencing gene transcription. Furthermore, if the nucleus stiffness and the connections between the nucleus and cytoskeleton, the LINC complex, are modulated, force transfer to the nucleus may be altered. This project will address the concept that the nucleus acts as a sensor for mechanical stimuli. It will also address the hypothesis that the role of the nucleus as a mechanosensor changes as a cell progresses along its differentiation route. We will investigate the mechanisms through which mechanical stimuli can induce changes in nuclear organisation and stem cell differentiation. By fully characterising changes in the mechanical properties, protein composition, nuclear architecture and epigenetic signature of biophysically stimulated MSCs as they undergo differentiation, we will identify key pathways responsible for the alteration of cellular mechanosensitivity. These can then be targeted to repair defective mechanosensitivity in diseased or aged cells. The results of this work will have far reaching implications for our understanding of how cells respond to mechanical stimulation, and will impact strategies for cell based regenerative medicine and musculoskeletal repair.

Impact Summary

Disease and ageing have been associated with abnormal or defective cellular mechanobiology, leading to an inappropriate mechano-response and catabolic signalling. As a result, the focus of this project is not on the development of a therapy, but the understanding of MSC mechanobiology, specifically the mechanisms responsible for alteration of the mechano-response with differentiation. If we are to move the findings of this work toward translation, our primary beneficiaries are other academic researchers, clinicians, biotech and the pharmaceutical industry. We will of course also ensure the general public engage with this exciting stem cell mechanobiology research. This programme will provide an improved understanding of the mechanisms behind mechanotransduction and how they regulate stem cell differentiation. Given that mechanical forces impact the growth and form of practically every tissue within the human body, defining a role for the nucleus as a mechanosensor will have potential implications across all eukaryotic cell types; for example to better understand and prevent the mechanosensitive initiation and spread of diseases such as prostate cancer. While this work relates primarily to MSCs, it may elucidate more widely applicable cellular signalling mechanisms. Armed with this knowledge, we can begin to explore therapies aimed at restoring the mechanosensitive regenerative potential of diseased and aged MSCs, first for in vitro tissue engineering techniques, and perhaps later for the stem cells residing within our bodies. We anticipate considerable long term societal benefits to patients suffering from a range of musculoskeletal and orthopaedic ailments. The enhanced understanding of MSC mechanotransduction will lead to improvements in both mechanical conditioning regimes used to engineer replacement tissues, and post-operative rehabilitation regimes. In addition to health, improved treatments bring economic impacts as a result of less post-operative revisionsand less time out of work for patients. Furthermore, the parallels drawn between this work on nuclear mechanosensitivity, and debilitating nuclear envelope related diseases may further progress toward the treatment of diseases including Hutchinson Gilford Progeria syndrome and Emery-Dreifuss Muscular Dystrophy. Towards the end of the project, we will focus on the exploitation of the findings with a focus on R&D investment. In characterising the mechanisms behind alteration of the mechano-response in stem cell differentiation, we will identify pathways, the modulation of which has the potential to rescue diseased or aged cells with abhorrent mechanical signalling. This will be of interest to gene therapy and pharmaceutical companies. There is also potential for collaboration with tissue engineering companies as the findings of this work will enhance the potential of MSCs for these therapies. With applicable skills present among the applicants, we would remain closely involved in the development of any industrial collaboration. In this regard, we also ensure maximum impact for the researcher, with potential opportunities to further develop professionally and remain involved in the project exploitation beyond the grant lifetime.

Committee	Research Committee C (Genes, development and STEM approaches to biology)
Research Topics	Regenerative Biology, Stem Cells
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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