Investigating the role of the RNA binding protein HuR in musculoskeletal development and disease

Age-associated diseases of the musculoskeletal system carry a heavy socio-economic burden, which is set to increase as life expectancy increases. Many of these diseases affect bone or cartilage in the joints, and lead to immobility and pain. This project will determine a molecular mechanism that can control cartilage formation and has strong relevance to the processes that affect cartilage in diseases of old age such as osteoarthritis. The central molecule of interest that is involved in the processes to be examined is a protein called HuR. It regulates the function of genes by controlling the destruction of an important functional molecule called mRNA. Importantly, HuR is widespread in the body and performs a number of critical roles in many tissues.

There is good evidence that HuR has important functions in cartilage but a study to fully define these roles has yet to be conducted. Therefore, the project's first aim will be to fully characterise the distribution and timing of HuR production in the developing skeleton, using the mouse as a model. Then, using a genetically modified mouse that we have recently developed in which HuR levels can be knocked out specifically in cartilage tissues, we will examine the effect that loss of HuR has on cartilage development as well as on knee joint degeneration in adult animals.

A further aim of the project is to determine the mechanisms affected by HuR in a cell culture model of cartilage development. We will use state-of-the-art gene sequencing technology and subsequent molecular analysis methods to identify the mRNAs regulated by HuR in cartilage cells and how this is occurring. The technologies used in this part of the project have the added benefit of defining how gene regulation that controls cartilage formation is affected at different tiers of control in a far greater level of detail than has previously been attempted.

To investigate the translational opportunities of these findings we will determine how inhibiting the functions of HuR can alter the generation of bone and cartilage tissue by adult human stem cells. These studies will allow the use of reagents that we already know directly affect HuR function, offering a valid approach for tissue regeneration when employed in laboratory-based skeletal tissue engineering.

This project will determine the role of the RNA binding protein HuR in the control of skeletal development by focussing on its role in cartilage differentiation. HuR is a post-transcriptional regulator of mRNA and can reduce the turnover of target transcripts in the cytoplasm. We have observed localised loss of HuR expression in critical regulatory regions of developing mouse long bone cartilage. This supports previous mouse knockout studies, which have identified a role for HuR in the differentiation, patterning and mineralisation of the developing skeleton. This project will characterise the detailed mechanisms affected by HuR, using in vivo and in vitro experimental systems. Firstly we will examine development and disease in a newly established cartilage-specific, tamoxifen-inducible HuR knockout mouse. Secondly, we will perform cutting edge characterisation of post-transcriptional and translational gene control during in vitro chondrogenesis. Thirdly, we will determine HuR's role in stem cells systems, which offer ready translatability into bone and cartilage tissue engineering. Characterising the processes affected by HuR during skeletal development will enhance our ability to modulate regenerative medicine strategies through the use of existing small molecule regulators. Furthermore, the work will improve our understanding of how post transcriptional gene regulation affects cartilage, which is timely given the emerging role of this tier of regulation in chronic diseases of the elderly such as osteoarthritis. Overall, this work will identify exciting new mechanisms that could underpin future treatments of debilitating, age-related diseases of the skeleton, which represent an ever-increasing socioeconomic burden.

Degenerative diseases associated with the skeletal system result in pain and disability for millions of people around the world. As our population continues to age, it is important that we address the degeneration of the musculoskeletal system so that people can lead their longer lives in a happier and more productive manner. This work aims to better understand basic aspects of cartilage and stem cell biology and, in doing so, develop novel approaches to treat cartilage disease and regeneration. This will benefit other scientists in the fields of skeletal development, arthritis research and ageing. Furthermore, tissue engineers will be able to use and build on the improvements to stem cell culture conditions that the project will define. The gene examined in the project performs essential roles in tissues throughout the body, which will be of interest to biological researchers in these diverse areas. These impacts will occur over a period of months or years as the work is disseminated at conferences and in scientific literature.

The project will impact upon society. Improved understanding of stem cells and cartilage biology will be the basis upon which treatments for individuals suffering from degenerative joint diseases will be developed. This applies particularly to older people as well as to very active people e.g. sportsmen and women. Such treatments will relieve pain and immobility for a great many people, vastly improving their quality of life. A further consequence of better treatments for cartilage disease and injury include lower treatment costs and a reduced care burden within the National Health Service. In addition, the UK economy would benefit through savings in disability and mobility benefit payments as would employers in the public and private sector as a result of reduced sickness pay and lost working hours. These are long-term societal impacts (years or decades), but stakeholders can be informed of the pipeline for the development of these treatments in the shorter term (months/years), which could shape policy. Stakeholders will include politicians, industry leaders, clinicians, healthcare managers and orthopaedic charities such as Arthritis Research UK. Impact of the work on the general public can occur continuously and will raise awareness of scientific research and healthy ageing. This can be implemented through open days where the public can meet scientists, through hosting work experience placements and by taking part in outreach activities in local schools.

The mechanisms determined in this work will be of interest to companies that are keen to develop products that can prevent or treat degenerative joint diseases such as osteoarthritis. The project will also develop novel cartilage tissue-engineering approaches. The findings have the potential to be commercially exploitable leading to the production of new spin out companies and to partnership with or expansion of existing enterprise. The project will employ a post-doctoral research associate for three years, training them in numerous molecular techniques. In addition, they will gain transferable skills such as science writing, data presentation, project management, and commercialisation. This will result in an individual who possesses a skillset that would benefit employers in the UK public or private sector.

Timescales for these impacts could be measured in months and years for public engagement and academic beneficiaries. Applying the findings to clinical treatments and commercialisation to a level that may benefit the general public could take 10 years or more and the further development of these treatments to a scale where they are able to affect welfare on a national scale may take decades.