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Culturing a better mesenchymal stem cell: using biomaterials to expand therapeutically active, naive cells for therapy

Primary Supervisor: Dr Ewan Ross, Life & Health Sciences 

Secondary supervisor: Professor Andrew Devitt

PhD project title: Culturing a better mesenchymal stem cell: using biomaterials to expand therapeutically active, naive cells for therapy.

University of Registration: Aston University 

Project outline:

Cell based therapies have become an increasingly effective clinical approach to promote tissue repair, wound healing or reduce inflammation. Mesenchymal stem cells (MSCs) are a key cell type used in cell based therapies. MSCs are multipotent stromal cells with the capacity to differentiate into a variety of cells (fat, bone, muscle) raising the potential for MSC transplants to graft and replace cells lost through injury or trauma. However, MSC can also exert beneficial therapeutic effects through modifying (suppressing) inflammation by inducing ‘repair’ responses from the immune system[1,2]

Producing sufficient MSCs for patients in the laboratory is difficult as they spontaneously differentiate in culture over time, losing their immuno-modulatory abilities and commit to differentiate to bone cells[3]. We have recently found that certain biomaterials can modulate the immunosuppressive function of MSCs[4]. In this work, we show that by growing MSCs on a surface containing nanopits arranged in a regular order, we maintain the naïve phenotype of cultured MSCs, prolonging their immunosuppressive capacity to inhibit T cell proliferation. During this work we identified alterations to MSCs metabolism which drives this maintenance of the naïve phenotype. Using certain metabolites, we can recapitulate the biomaterial driven MSC phenotype. This provides a new strategy to grow and maintain functional, naïve immunomodulatory MSCs in culture.

MSCs have a number of different ways in which they can modulate an inflammatory environment, including release of soluble factors, cross-talk mediated by surface proteins with immune cells as well as the release of extracellular vesicles (EVs). Immunomodulation by EVs is an exciting and novel mechanism by which the immune system may be controlled for therapeutic benefit and it provides great potential for regenerative medicine applications. Importantly, it highlights that EV, rather than the MSC alone, have therapeutic potential. A current challenge in the field is the production of MSC and EV that are optimally active for immunomodulation.

This PhD will expand on our initial studies by looking at how exposure to biomaterials affects MSCs release of immuno-modulatory EVs. MSCs will be cultured for extended periods on existing nanotopography biomaterials as well as on newer polymer based systems (through collaboration with the University of Glasgow). Polymer based biomaterials allow delivery of both an adhesive and soluble factor signal to the MSCs, and by changing the factor presented allows “tuning” of the system. Maintenance of naïve MSCs will be optimised using the polymer based systems and will be compared to cells grown on nanotopographies or cells treated with identified metabolites that promote immune-modulation. Changes to MSC physiology and phenotype will be assessed as well as immuno-suppressive function on T cell proliferation. Once optimal conditions have been established, EVs will be collected, characterised, phenotyped and their contents examined using established techniques at Aston. Effects of MSCs derived EVs on macrophage biology as well as T cell function will inform about the therapeutic potential of these cell products.

To formally demonstrate the therapeutic translational potential of biomaterial educated MSCs and their EVs, the immuno-modulatory potential of cells or cell products will be assessed using in vivo models of inflammation. Depending on results from the in-vitro studies, we will us an appropriate model of inflammation (e.g. delayed type hypersensitivity for T cell responses, air pouch model for innate immune responses). More complex models disease associated models such as inflammatory arthritis may also be challenged with MSCs derived EVs in order to reveal how the inflammatory response is modulated. 

References:

  1. Tissue regeneration: The crosstalk between mesenchymal stem cells and immune  response. Qi et al., J Cellular Immunology2018. https://doi.org/10.1016/j.cellimm.2017.11.010
  2. Challenges in clinical development of mesenchymal stromal/stem cells. Mastrolla et al., Stem Cells Trans Med 2019. https://doi.org/10.1002/sctm.19-0044
  3. Bone marrow-derived mesenchymal stem cells change phenotype following in vitro culture: implications for basic research and the clinic. Bara et al., Stem Cells 2014. https://doi.org/10.1002/stem.1649
  4. Nanotopography reveals metabolites that maintain the immunosuppressive phenotype of mesenchymal stem cells. Ross et al., 2019. https://doi.org/10.1101/603332

BBSRC Strategic Research Priority: Understanding the Rules of Life: Immunology & Regenerative Biology

Techniques that will be undertaken during the project:

MSCs will be grown on tuneable biomaterial surfaces using standard tissue culture techniques. Effects on MSCs immuno-modulation will be assessed by suppression of T cell proliferation (via flow cytometry), regulatory T cell maturation (in vitro suppression assay) and MSC characterisation (PCR, Western Blot, in vitro differentiation assay). Release of soluble factors by cultured MSCs will be quantified (by ELISA). EVs will be collected, characterised, phenotyped and their contents examined using established methods and expertise at Aston University. The immunomodulatory potential of purified EVs will be assessed using in vitro assays of T cell proliferation as well as assessing changes to specific subsets of T cells and B cells (by flow cytometry). EVs may also be used to assess effects on macrophage function (via horizontal and vertical chemotaxis assays), polarisation (via flow cytometry) and activation (by ELISA) in vitro. As progress allows, purified MSCs derived EVs may be used in murine models of inflammation (such as peritonitis or inflammatory arthritis) to demonstrate their therapeutic potential. 

Contact: Dr Ewan Ross, Aston University