Role of miR96 in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a devasting disease with a very poor survival rate. It occurs more frequently in women and involves the closing down of lung arteries due to thickening of their walls (remodelling). This puts a strain on the heart and causes failure of the right ventricle of the heart and death. Serotonin is a chemical that can cause this remodelling and it acts via a protein called a 5HT1B receptor. Small pieces of RNA called microRNAs can regulate genes and microRNA96 can decrease the number of 5HT1B receptors thus reducing the disease-causing effects of serotonin. In lung cells from female PAH patients or animal models, there can be a deficiency in this microRNA96 which causes an increase in the number of 5HT1B receptors. We have shown that restoring the levels of microRNA96 in lung arteries using a microRNA96 'mimic' by injection can decrease the number of 5HT1B receptors and can reverse pulmonary hypertension in mouse and rat models of the disease. Here we wish to understand fully how this mimic works. We will also determine the best way to administer the mimic, the best dose, if it has side effects and if it would work better with other drugs.

MicroRNA(miR)96 targets the 5HT1B gene and is under-expressed in pulmonary artery smooth muscle cells (PASMCs) with a BMPR-II mutation; 5HT1B protein and mRNA expression and serotonin-induced proliferation is increased in these cells. MiR96 is also down-regulated in hPASMCs from female pulmonary arterial hypertension (PAH) patients where increased 5HT1B expression causes increased proliferation. This increased proliferation can be reversed by pre-miR96. This suggests that miR96 may play a role in the pathobiology of PAH and that a mimic may be a novel therapy for PAH. Delivery of miR96 to pulmonary arteries in vivo prevents/reverses PH in mouse models via decreased 5HT1B expression and increased BMPR-II signalling. Here we will fully determine the molecular mechanisms behind the oestrogen/BMPR-II /miR96 axis and evaluate the potential of a miR96 mimic as a treatment for PAH. We will examine effectiveness of a miR96 mimic in a robust PH rat model after optimizing pulmonary specific delivery and dosage. We will determine off-target and side-effects and determine if a combination approach optimises the therapeutic effect.

During the course of this study we will seek to attract R&D investment and commercial partners to drive this novel therapeutic strategy into the clinic. For example we will approach United Therapeutics and MiRagen. Professor MacLean has previous or ongoing collaborations with these companies. The novelty of the miR-mimic strategy and optimisation of the dosing procedures will be of extreme interest to these companies as will be transferable to other miR-mimic approaches to other lung diseases. Well beyond this study, this could lead ultimately to improvement to the quality of life and survival of PAH patients.
The development of the novel and innovative methodology for miR-mimic delivery to lung requires cross-disciplinary approaches as described and we intend to publish as quickly as possible to impact others in the field who wish to adopt similar procedures.
In vivo techniques are recognised by the MRC and BBSRC as vulnerable skills. Professor MacLean is recognised as an expert in the training of scientists in in vivo skills, having run one of the four UK Integrative Mammalian Biology centres (co-funded by the MRC) and secured over £4M of postgraduate training grants for in vivo. This research will assist in retaining these skills within the academic sector by delivering highly skilled researchers in in vivo skills. This will apply to the PDRA and also more junior RAs who will be trained up in these skills by the PDRA. PDRA development and mentoring is taken seriously and they will be given the opportunity to supervise and train undergraduates and postgraduates. Mentoring will ensure that the PDRAs research productivity is not compromised by this. It is possible that after the research is finished the PDRA could transfer these skills to the commercial sector which has acknowledged the continued requirement for researchers trained in these skills.
Professor MacLean received an MBE for her many Public Engagement (PE) activities. She is involved in The University PE strategy and has run Glasgow's Cafe Scientifique every month since 2004. These events have informed and will continue to inform the public about the value of research using animals. This contributes to a cultural change to the UKs understanding and tolerance of such research. This will be facilitated by the Pathways to Impact activities associated with this research.
The research will be of great interest to the Pulmonary Hypertension Associations led by patient groups who keep patients informed of new promising therapies and MacLean will maintain a dialogue with these societies.
Through her Pathways to Impact activities, MacLean will engage with and inform a local MP, Scientific Advisor for Chief Scientists Office (Muffy Calder), Head of Research and Enterprise, Director of Scottish Enterprise, representative from Research Councils, Charities, Scottish Development International and representatives from the NHS.
In addition, basic scientists and clinicians in the field of PAH have already expressed an interest in the work leading up to this proposal and will gain important knowledge and understanding about the potential of such a novel therapeutic strategy.