Musculoskeletal research at NFB involves devising strategies to regenerate the intervertebral disc and bone.
Intervertebral Disc Regeneration
Degeneration of the intervertebral disc (IVD) is the primary cause of neck and low back pain. The IVD is composed of two distinct but interdependent tissues: a gelatinous centre known as the nucleus pulposus (NP), and several surrounding coaxial lamellae that form the inner and outer annulus fibrosus (AF). This unique structural feature allows the IVD to constrain motion under high loads and provide flexibility at low loads. Factors such as abnormal mechanical stresses, biochemical imbalances and nutritional and genetic deficiencies are all reported to contribute to an imbalance in the intervertebral environment and play a role in disc degeneration disease (DDD). As the natural aging process continues, the gelatinous nucleus pulposus region of the disc is replaced by a more solid, less flexible, cartilaginous disc. This in turn has a negative effect on cell viability due to altered mechanical stresses and limited access to nutrition and oxygen. Cellular adaptation, due to this imbalance, is evidenced by regulation of critical genes implicated in apoptotic mechanisms. In degenerated discs, resident nucleus pulposus cells may still remain responsive to exogenous treatment factors and may be stimulated to recapitulate the biosynthesis of functional extracellular matrix (ECM) in vivo.
IVD regeneration strategies at NFB are based on the use of a functionalized injectable scaffold that can deliver therapeutic biomolecules such as genes and cells. Genes that simultaneously inhibit degeneration and promote normal matrix turnover are currently being investigated.
Bone defects are a common occurrence and can be caused by an injury, disease or surgical procedure. The treatment of these defects is both costly and problematic. The most commonly used therapy is the use of autografts.This involves the excision of the patient's own tissue, e.g. from the pelvis, and implantation at the defect site. This therapy is associated with donor-site morbidity, infections, and blood loss. As a result, the treatment will create a second scar site and a transfusion may be required.
The introduction of tissue engineering scaffolds aims to overcome the shortcomings of the currently used therapies. Current research at NFB takes a non-viral gene therapy approach to this problem. Plasmid DNA is delivered via a scaffold that mimics the composition of bone, i.e. collagen type I/calcium phosphate. The scaffold structure is designed to encourage cellular infiltration through pore channels, while the plasmid DNA is complexed into a form that enables transfection efficiency.
Another aspect of orthopaedic research at NFB is in the fabrication of scaffolds that closely mimic the biomechanical properties of the surrounding bone. A patented multi-stage rapid prototyping technique has been developed which produces porous titanium scaffolds with a fully interconnected pore network. Results show that both pore size and porosity are reproducible. Treatment of this titanium surface creates a scaffold capable of supporting osteoblast growth. Tests of the spine when subjected to biomechanical stresses indicate that the porous titanium scaffolds have the potential to be employed in spinal fusion or other orthopaedic applications.
Jaipur, a town in northern India, is famous in strife-torn areas as the birthplace of an extraordinary prosthesis, or artificial limb, known as the Jaipur Foot. This has revolutionized life for millions of land-mine amputees. The beauty of the Jaipur Foot is its lightness, mobility and its low price. Those who wear it can run, climb trees and pedal bicycles. While a prosthesis for a similar level of amputation can cost several thousand dollars in the U.S., the Jaipur Foot can cost as little as $30 in India. However, the success of the Jaipur Foot is not without its drawbacks. Compared to western prosthetic feet, where lighter and more durable materials are available, the Jaipur Foot is both somewhat heavier and of a shorter functional life (only 3-5 years). The current project involves developing the next generation of the Jaipur Foot using computer aided design (CAD), reducing its weight and increasing its durability so that its life is extended.. Evaluation of the performance of a prototype is being carried out through laboratory testing and gait analysis; and when optimal performance is achieved, it will be tested in a field trial where the improved prosthesis will be fitted to amputees. The overall objective of the project is to design a durable prosthetic foot to be used in landmine-affected countries It should be sufficiently robust and locally made using available resources.
Tendon and Ligament Regeneration
Over 17 million tendon operations are performed annually in US alone. Tendon incidents are associated with pain and poor quality of life leading to healthcare costs exceeding US $150 billion in Europe annually. Non-invasive pharmacological strategies show little success, even for small injuries. Intervening replacement is therefore necessary, especially in severe injuries or in cases of large defects. Tendon repair therapies rely heavily on tissue grafts and synthetic biomaterials. However, the limited supply of autografts in severe injuries and in degenerative conditions restricts their use. The use of allografts/xenografts has also been questioned due to poor success rate. Long-term implantation studies have also revealed several drawbacks (e.g. fibrotic encapsulation of the implant) in the use of synthetic materials. To this end, NFB has developed collagen-based nano-textured scaffolds with structural, physical and biological properties similar to those obtained from native supramolecular assemblies. Currently, we are investigating the influence of scaffold functionalisation with proteoglycans and glycosaminoglycans for functional regeneration. NFB is also developing cell-based therapies for tendon repair.