Dynamic surfaces to mimic mesenchymal stem cell niche functions

We live in an ageing society and we are outliving the useful lives of our bodies. Structural components suffer with arthritis or osteoporosis and organs provide reduced efficiency and can become damaged or diseased through degenerative processes. We live at an exciting point in history where we all have the expectation that unlocking the potential of stem cells will help with these urgent regenerative demands. Embryonic stem cells remain locked in ethical debate, however, and also have clinical issues associated with their use (including lack of immune privilege, which can cause adverse immune reactions, and the possibility of teratoma formation, which is a type of cancer ). Adult stem cells provide an alternate route with mesenchymal stem cells from, for example, bone marrow (obtained by e.g. marrow donation) or fat tissue (obtained by e.g. liposuction) providing an attractive, autologous (i.e. from the patient) source of multipotent cells.
A major hurdle with adult stem cells is their rapid and spontaneous differentiation during standard culture in the lab (i.e. out of the body they rapidly stop acting as stem cells). Current cell culture materials were developed before our understanding of stem cells had matured and were designed to grow mature cell types (such as fibroblasts) or cell lines (such as HeLa cells). Thus, we are currently lacking good platforms for autologous stem cell growth.
In the last few years, researchers, including ourselves, have understood that MSC growth and differentiation is controlled by the way cells adhere to materials and consistent 'rules' are starting to emerge. Developments in materials science have put forwards surfaces that are either favourable for MSC growth or good for differentiation, however, but that cannot control both.
In our bodies, stem cells reside in specialised locations (called 'niches') that control their growth to allow a supply of stem cells to be present in tissues throughout our lives and also regulate differentiation in response to tissue demand. It is, again, considered that cell adhesion is key to the niche regulation of stem cells.
Here, we will develop highly novel materials that initially support the growth (multiplication) of multipotent MSCs, which can then be switched under user control to turn on the desired type of differentiation, to generate the mature 'functional' cells of the body. To do this, we will use enzymes (biological catalysts) to cleave the self-renewal surface (this will be made by use of adhesion controlling chemistry and use of nanoscale spatial information i.e. small chemical patterns) and reveal the underlying differentiation surface (different chemistries to control differential adhesion, and hence drive stem cell fate). Such enzymes can be simply added by the user to the cell media (their food). We will then go further and place the switch under cell control. As cells become dense in a culture (near confluence) their protein (and hence enzyme) profile changes and we will exploit this to find enzymes that can perform the switch from a growth-promoting substrate to a differentiation-inducing substrate, only after the cells have grown to large numbers.
This technology will act as a platform for MSC growth and differentiation. It will be dynamic, as their natural niche is dynamic, and it will be an important step in the development of production of autologous cells with therapeutic potential.

The stem cell niche acts to control stem cell growth (control self-renewal) and differentiation in a dynamic manner. Current developments in materials science, focused on a key regenerative stem cell type, the mesenchymal stem cell, have allowed us to regulate both self-renewal (to allow us to grow multipotent populations by preventing phenotypical drift to e.g. fibroblasts) and to target differentiation to desired functional cell types. The materials do this by controlling cell adhesion and intracellular tension important for regulation of biochemistry and transcription. However, the materials are designed either for growth or for differentiation and lack the flexibility to support both stem cell functions.
We have developed enzyme switchable surfaces that can be used to control cell adhesion in an on-demand manner and will exploit this technology to develop dynamic materials for stem cell culture. In the proposal, we will create an initial surface that control adhesion to promote self-renewal and hence growth as multipotent stem cells allowing us to achieve large numbers of true stem cells. This will be achieved by controlling the length of polyethyleneglycol (PEG) chains that block cells from adhering to the underlying differentiation surface (e.g. RGD, t-butyl, single peptides). Enzymatic cleavage of the PEG chains will then expose the differentiation surface to the mesenchymal stem cells on demand. Hence we will have fabricated surfaces that allow the cells to grow to large numbers and then change to functional cells in a controllable manner mimicking niche dynamics.
Finally, we will explore the possibility of using secreated enzymes (e.g. matrix metalloproteases) which have changes expression profiles in dense cultures to switch the surfaces as the cells grow more confluent (i.e. the enzymatic switch would automatically happen when enough stem cells were present).

Initially impact will be academic as this is a very new concept. However, it is recognized that a step change is required to facilitate therapeutic use of stem cells as traditional cell culture plastics are not suitable and soluble factor chemistry is proving complex and can add artefact and so this research is vital. The use of niche biomimicry (stem cells responding on demand) will capture the imagination of science in general and we will target high-impact journals to ensure maximum dissemination to the community.

It is noteworthy that the applicants have strong track record in taking fundamental research observations towards commercialisation through spin-out and licensing. We will, again, look to protect IP and then exploit this towards next generation stem cell culture products. Such products will impact on cell culture industry as new products for stem cell growth are made, biotechnology industry will benefit as capacity for stem cell growth increases and autologous stem cell therapies become available. Tissue engineering will benefit as lots of high-quality cells from small isolations can be achieved and incorporated in their scaffold materials. Finally, clinicians and the public will benefit from therapies enabled by our platform technologies. This exploitation will be ongoing through the grant.

Thus, non-academic beneficiaries will include:
1) Industry - the development of new materials will fuel stem cell research. Stem cells themselves can now be purchased from catalogues and we will provide new consumables for purchase alongside the cells to aid research.
2) Clinic - most clinicians now accept that new biomaterials coupled to stem cells and nanotechnology will be important in the medium-term future. We believe it is pivotal for clinicians to engage with early-stage research to inform a realistic compromise between material function and clinical application.
3) Patients - the public are interested in (and actually expect) the delivery of stem cell therapies and our surfaces hold the potential to help deliver these therapies.
4) Public - through our public outreach in schools (Dalby has close ties with Lenzie Academy). We will inspire students to consider a career in research and academia. There is a poor understanding amongst school children taking career decision about what academics do beyond teaching and the best students choose medicine as a default career. However, basic science can be just as rewarding, if not more so, and school leavers should be aware of the possibility to help change medicine through academic research. It is, we believe, encumbent on us to stimulate, inform and inspire the next generation as an informed public base will lead to an informed science culture. Dalby had participated in stem cell debates with the public (for BBSRC, EPSRC and Royal Society of Edinburgh) and will continue this work.

To support this impact we will use our surgical links with Mr Meek through the Glasgow Orthopaedic Research Initiative and also with Prof Hart for plastic and reconstructive surgical links. They are both keen to engage with fundamental science to help facilitate translation.