Developing a novel therapeutic to target endogenous stem cells to accelerate tissue repair and regeneration.

Treatments based on stem cells hold huge promise but significant challenges remain in transferring the enormous strides that have been made in the lab to routine patient care. Whilst many of these problems have been overcome for blood stem cells, e.g. to treat cancers of blood cells, early reports of success in other organs are only just beginning to emerge but even these are limited to specialist sites such as the eye. An alternative approach would be based on administering a drug that enhances the regenerative properties of the body's own stem cells without first taking them out and growing them in the lab.
When a cell is injured it releases its contents and alerts neighbouring cells, which are then primed to respond quickly and repair the injury. We have discovered that a key molecule called High Mobility Group Box 1 (HMGB1), which is present in the nuclei of all cells of the body, alerts stem cells from a variety of tissues including bone, muscle and blood. We have further shown that if HMGB1 is administered to mice at the time of injury, and even 2 weeks before injury, it leads to accelerated healing of all of these tissues.
Our overall aim is to design a drug that is an analogue of HMGB1 and can be used to accelerate healing in humans. However, it is difficult to produce large amounts of highly purified HMGB1 suitable for clinical use. Our current proposal is to overcome these limitations by deleting the parts of the HMGB1 molecule with the unwanted activities whilst preserving the key property of improving healing to maximise its efficacy as a therapeutic. We have already successfully deleted unwanted sections of the HMGB1 molecule and will further fine-tune its properties. Our data from all our mouse injury models show that it is only necessary to give a single dose of HMGB1 either directly into the vein or at the site of injury. If successful, our strategy has the potential for accelerating healing in patients suffering from a wide range of disorders, including injury, elective surgery and even those requiring blood stem cell transplants.

Alarmins are passively released by dying or stressed cells after injury. We have found that the prototypical alarmin HMGB1, a highly-conserved molecule that forms a crucial part of the transcriptome, promotes tissue regeneration by transitioning stem cells from a wide variety of tissues, including blood, bone and muscle to G(Alert). This strategy to accelerate tissue healing and promote regeneration by targeting endogenous stem cells has significant advantages over treatments that rely on administration of stem cells that have been expanded in vitro.
We found that only native HMGB1, which has no inflammatory action, transitions stem cells to G(Alert) and acts in conjunction with CXCL12 by forming a heterocomplex and inducing a conformational change in the receptor CXCR4. However, native HMGB1 has inherent limitations as it has LPS binding domains, nuclear localisation sequences and the C-terminus is toxic to bacteria. Furthermore, it can be oxidised in vivo to the disulphide form, which is pro-inflammatory.
Our aim is to identify a truncated variant of HMGB1 which retains the key property of transitioning stem cells to G(Alert) without the unwanted characteristics of the native molecule and which can be expressed in E. coli and purified with ease. We have already successfully expressed truncated variants of HMGB1 in E. coli and are screening for biological activity using a high-throughput chemotaxis assay. Our truncated variants include forms where cysteines have been substituted with serine to prevent oxdisation to the pro-inflammatory form. We will generate further truncated variants, incorporating data from crystal structure determination of the heterocomplex with CXCl12 and assess the efficacy of the truncations that pass the chemotaxis assay using our well-established murine models of muscle, bone and haematological injury.
This will allow us to proceed with development of a therapeutic that will be suitable for testing in early phase clinical trials.

Development of an effective therapeutic that can be administered systemically or locally to improve healing will have major health benefit for millions of patients across the globe for wide variety of disorders ranging from trauma and elective surgery through to haematopoietic stem cell transplantation. We already have data demonstrating the regenerative effects of HMGB1 in a variety of in vivo murine models and are well placed to develop a therapeutic and take it through to early phase proof of concept clinical trials.
Through our contacts in the biotechnology industry it is clear that there is a need for effective therapeutic strategies to accelerate tissue healing and regeneration. The team spans across diverse skill sets and experience in basic and clinical sciences, and is ideally suited to deliver on the development of an effective therapeutic and develop it all the way through to early phase clinical trials.
Prof Bountra leads a world class team at the Structural Genomics Consortium in Oxford. The SGC has to date solved the structures of >1500 medically relevant proteins and delivered 40 potent selective and cell-permeable chemical probes. The other co-applicants from the SGC include experts in expression of recombinant proteins (Dr Burgess-Brown), membrane proteins (Dr Duerr) and crystallography of protein complexes (Prof Yue). Prof Sir Marc Feldmann has extensive experience of successfully translating lab findings to the clinic, most notably the development of anti-TNF for the treatment of rheumatoid arthritis. Prof Nanchahal is a translational surgeon scientist leading an early phase clinical trial funded by the Wellcome Trust and Department of Health for a novel treatment based on his lab data for Dupuytren's disease, a common fibrotic condition of the hand. Based on positive dose response data he is now proceeding with a phase IIB trial.