Innovative manufacturing of decellularised bone scaffolds

Musculoskeletal disorders are the second greatest cause of disability in the UK. For example, one third of people aged over 45 have sought treatment for osteoarthritis, costing the NHS over £5 billion per year.

Diseases such as cancer or trauma through mechanical insult can lead to damage of the skeletal structures requiring surgical intervention. Graft materials are used to replace and restore the function of musculoskeletal tissues including bone, cartilage, menisci and tendons.

In iMBE we have developed decellularised musculoskeletal tissue scaffolds from both human and animal tissues to address a range of clinical grafting needs.

Decellularised scaffolds are advantageous over traditional human and animal grafts, as removal of cellular components renders the graft immune-compatible. The advantage over synthetic grafting materials is the retention of the native tissue composition, structure and function which acts as the optimal environment for regenerative stem and progenitor cells.

Decellularised bone has the potential to repair bony defects, but also to act as a skeletal attachment site when incorporated into composite bone-soft tissue scaffolds for example in a bone-tendon graft for cruciate ligament reconstruction. Decellularised bone and tendon products have been shown to function as excellent regenerative scaffolds in large animal studies.

Although appropriate to produce tissues in the research setting, the current decellularisation processing methods for bony tissues are not compatible with scale up for industrial manufacture and therefore prove a real barrier to the use of these scaffolds clinically in patients. Also, one size does not fit all; a range of decellularised bone grafts with differing properties is required to match with orthopaedic application, surgeon preference, and patient variability.

The research challenge is to develop improved industry-compatible methods of bone decellularisation and to elucidate the biological and biomechanical variance in the end product that can be achieved through altering different bioprocess parameters.

The specific research questions are:
1. Can the manufacturing bioprocess be adapted to good manufacturing process (GMP) standards appropriate for clinical grade scaffold production at NHS BT facilities?
2. Can variation of the source tissue, storage and sterilisation method lead to a stratified range of decellularised bone products?

This project will involve biological, biomechanical and CT analysis of bone along with the product design challenge of building a device to partly automate the bioprocess.

This research has the potential to directly impact on industry practice and also contribute towards the production of improved decellularised scaffolds for use in bony tissue regeneration.

Aim: To produce and characterise a range of decellularised bone products using industry compatible manufacturing processes to a standard suitable for clinical use.

Objectives (manufacturing):
1. To physically remove bone marrow in a way compatible with working in a grade B clean room.
2. To develop a rig/device to contain and automate the tissue washing process.
3. To reduce the duration of the decellularisation bioprocess.
The manufacturing process will initially be optimised using porcine tissue prior to application to human tissue.

Objectives (product variation):
1. To determine the effect of the following parameters on resultant biological, material and biomechanical properties of the human bone scaffold.
a. The size and shape of bone blocks which are processed
b. The storage method used e.g. frozen vs lyophilised
c. The sterilisation method used e.g. irradiation vs chemical sterilisation

This project will use decellularisation, histology, cell culture and biochemical assay facilities in FBS. Micro CT imaging and biomechanical testing facilities will be used in the school of mechanical engineering.

Regenerative Medicine been defined as "an interdisciplinary approach, spanning tissue
engineering, stem cell biology, gene therapy, cellular therapeutics, biomaterials (scaffolds and matrices),nanoscience, bioengineering and chemical biology that seeks to repair or replace damaged or diseased human cells or tissues to restore normal function, (UK Strategy for Regenerative Medicine). CDT TERM will focus on acellular therapies, scaffolds,autologous cells and regenerative devices, which can be delivered to patients as class three device interventions, thus reducing the time and cost of translation and which provide an opportunity to deliver economic growth and benefits to health in the next decade. The primary beneficiaries of CDT TERM are patients, the health service, UK industry, as well as the academic community and the students themselves. Recognising that the impact and benefit from CDT TERM will arise in the future, the statements describing impact below are supported by evidence of actual impact from our existing research and training.

Patients will benefit from regenerative interventions, which address unmet clinical needs, have improved safety and reliability, have been stratified to meet patients needs and manufactured in a cost effective manner. An example of impact arising from previous students work is a new acellular scaffold for young adult heart valve repair, which has demonstrated improved clinical outcomes at five years.

The Health Service will benefit from collaborations on research, development and evaluation of technologies, through existing partnerships with National Health Service Blood and Transplant NHSBT and the Leeds Biomedical Musculoskeletal Research Unit LMBRU. NHSBT will benefit through collaborative projects, through technology transfer, through enhancement of manufacturing processes, through pre-clinical evaluation of products and supply of trained personnel. We currently collaborate on heart valves, skin, ligaments and arteries, have licensed patents on acellular bioprocesses, and support product and process developments with pre-clinical testing and simulation. LMBRU and NHS clinicians will benefits from our collaborative research and training environment and access to our research expertise, facilities and students. Existing collaborative projects include, delivery devices for minimally manipulated stem cells and applied imaging for early OA.

Industry will benefit from supply of highly trained multidisciplinary engineers and scientists, from collaborative research and development projects, from creation and translation of IP, creation of spinout companies and through access to unique equipment, facilities and expertise. We have demonstrated: successful spin outs in form of Tissue Regenix and Credentis; successful commercialisation of a novel biological scaffolds for vascular patch repair; sustainable long term R and D and successful licensing of technology with DePuy; collaborative research with Invibio, partnering with Simulation Solutions to develop new pre-clinical simulation systems, which been adopted by regulatory agencies such as China FDA. Our graduates and researchers are employed by our industry partners.

The academic community will benefit through collaborative research and access to our facilities. We have funded collaborations with over 30 academic institutions in UK and internationally. The CDT TERM will support these collaborations and the academic partners will support student research and training. The CDT students will benefit from enhanced integrated multidisciplinary training and research, a cohort experience focused on research innovation and translation, access to our research partners, industry and clinicians. Feedback from existing students has identified the benefit of the multidisciplinary experience, the depth and breadth of excellence in our research base, the outstanding facilities and the added value of the cohort training.