Dr Anvesha Singh, Dr Katy Roach and Professor Peter Bradding
Many types of chronic heart diseases are characterised by myocardial fibrosis (MF), including ischemic heart disease, valvular heart disease, inherited and acquired cardiomyopathies, diabetes and aging1. Like many other fibrosing diseases, accumulation of fibrotic extracellular matrix leads to impaired tissue function. Fibrosis disturbs mechanical function and promotes electrical dysfunction leading to heart failure and an increased risk of sudden cardiac death2-4.
Aortic stenosis (AS), or narrowing of the aortic valve is the commonest valve lesion requiring surgery in the western world. It is characterised by progressive thickening, fibrosis and calcification of the aortic valve leaflets, leading to reduced leaflet mobility and valve obstruction5. Current guidelines recommend aortic valve replacement in severe AS, only once patients become symptomatic. However, the chronic pressure overload caused by the stenosed valve leads to many changes within the heart or ‘cardiac remodelling’, including MF. These changes occur early in response to AS, and MF has been detected in up to 50% of those with AS6. The presence of MF in AS is a poor prognostic marker, which progresses rapidly and remains only partially reversible even after aortic valve replacement, which is the only available treatment for AS. There are no specific medical therapies available which ameliorate or prevent MF or progression of AS and this therefore represents an important unmet clinical need. Safely inhibiting pathological fibroblast activity is likely to provide an effective means to ameliorate both AS and MF.
Myofibroblasts and KCa3.1 ion channels
Myofibroblasts are the key cells implicated in driving excessive extracellular deposition7, 8. The signalling pathways involved in MF are similar to those that promote fibroblast to myofibroblast transition in other tissues, such as TGFβ1, ALK5 and SMAD2/39, 10. Active KCa3.1 ion channels promote pro-fibrotic (myo)fibroblast activity in human cells derived from many human organs, and also from rodent hearts, and regulate cardiac fibrosis driven by hypertension, volume overload and angiotensin II in animal models11. However there are no data on the expression of KCa3.1 channels in human cardiac or valvular fibroblasts or cardiac tissue.
The KCa3.1 knockout mouse is healthy and viable, and a selective orally bioavailable KCa3.1 blocker senicapoc (ICA-17043) was very well tolerated for 12 months in a human phase III clinical trial for sickle cell disease. KCa3.1 is therefore a potentially attractive therapeutic target for the prevention of cardiac and valvular fibrosis, with the potential for rapid translation to the clinic.
We hypothesise that KCa3.1 ion channels are a common denominator promoting both MF and AS progression.
1. To examine KCa3.1 ion channel expression in cultured primary human atrial, ventricular and aortic valve fibroblasts using RT-PCR, western blotting and patch clamp electrophysiology
2. To examine KCa3.1 ion channel expression in cardiac and aortic valve tissue using immunohistochemistry
3. To determine the effects KCa3.1 channel inhibition on cardiac and aortic valve fibroblast TGF1- and advanced glycation end product (AGE)-dependent pro-fibrotic responses, specifically: Ca2+ mobilisation, SMAD2/3 nuclear translocation/phosphorylation, proliferation, survival, SMA expression, contraction in collagen gels12.
4. To develop an ex vivo model of human cardiac and aortic valve fibrogenesis, similar to that described for human lung, and the effects of KCa3.1 inhibition13.
The student will work in an experienced lab with an excellent track record. They will receive full training in the above-mentioned techniques, in addition to being supported by relevant courses provided by the Doctoral College on research effectiveness (using reference managers, performing literature searches, statistical skills and writing skills) and professional development. The student will be expected to submit abstracts to national and international conferences and aim to publish their work in peer-reviewed journals. The results of this PhD will also be used to inform future grant applications.
1. de Boer RA, De Keulenaer G, Bauersachs J, Brutsaert D, Cleland JG, Diez J, Du XJ, Ford P, Heinzel FR, Lipson KE, McDonagh T, Lopez-Andres N, Lunde IG, Lyon AR, Pollesello P, Prasad SK, Tocchetti CG, Mayr M, Sluijter JPG, Thum T, Tschope C, Zannad F, Zimmermann WH, Ruschitzka F, Filippatos G, Lindsey ML, Maack C and Heymans S. Towards better definition, quantification and treatment of fibrosis in heart failure. A scientific roadmap by the Committee of Translational Research of the Heart Failure Association (HFA) of the European Society of Cardiology. Eur J Heart Fail. 2019;21:272-285.
2. Harris KM, Spirito P, Maron MS, Zenovich AG, Formisano F, Lesser JR, Mackey-Bojack S, Manning WJ, Udelson JE and Maron BJ. Prevalence, clinical profile, and significance of left ventricular remodeling in the end-stage phase of hypertrophic cardiomyopathy. Circulation. 2006;114:216-225.
3. O'Hanlon R, Grasso A, Roughton M, Moon JC, Clark S, Wage R, Webb J, Kulkarni M, Dawson D, Sulaibeekh L, Chandrasekaran B, Bucciarelli-Ducci C, Pasquale F, Cowie MR, McKenna WJ, Sheppard MN, Elliott PM, Pennell DJ and Prasad SK. Prognostic Significance of Myocardial Fibrosis in Hypertrophic Cardiomyopathy. J Am Coll Cardiol. 2010;56:867-874.
4. Vasquez C and Morley GE. The Origin and Arrhythmogenic Potential of Fibroblasts in Cardiac Disease. J Cardiovasc Transl Res. 2012;5:760-767.
5. Pawade TA, Newby DE and Dweck MR. Calcification in Aortic Stenosis: The Skeleton Key. Journal of the American College of Cardiology. 2015;66:561-77.
6. Balciunaite G, Skorniakov V, Rimkus A, Zaremba T, Palionis D, Valeviciene N, Aidietis A, Serpytis P, Rucinskas K, Sogaard P and Glaveckaite S. Prevalence and prognostic value of late gadolinium enhancement on CMR in aortic stenosis: meta-analysis. Eur Radiol. 2020;30:640-651.
7. Camelliti P, Borg TK and Kohl P. Structural and functional characterisation of cardiac fibroblasts. Cardiovasc Res. 2005;65:40-51.
8. Banerjee I, Yekkala K, Borg TK and Baudino TA. Dynamic interactions between myocytes, fibroblasts, and extracellular matrix. Ann N Y Acad Sci. 2006;1080:76-84.
9. Roach KM, Feghali-Bostwick C, Wulff H, Amrani Y and Bradding P. Human lung myofibroblast TGFbeta1-dependent Smad2/3 signalling is Ca(2+)-dependent and regulated by KCa3.1 K(+) channels. Fibrogenesis & tissue repair. 2015;8:5-015-0022-0. eCollection 2015.
10. Huang C, Shen S, Ma Q, Chen J, Gill A, Pollock CA and Chen X-M. Blockade of KCa3.1 ameliorates renal fibrosis through the TGF-beta1/Smad pathway in diabetic mice. Diabetes. 2013;62:2923-2934.
11. Roach KM and Bradding P. Ca(2+) signalling in fibroblasts and the therapeutic potential of KCa3.1 channel blockers in fibrotic diseases. Br J Pharmacol. 2020;177:1003-1024.
12. Roach KM, Duffy SM, Coward W, Feghali-Bostwick C, Wulff H and Bradding P. The K(+) Channel KCa3.1 as a Novel Target for Idiopathic Pulmonary Fibrosis. PLoS One. 2013;8:e85244.
13. Roach KM, Sutcliffe A, Matthews L, Elliott G, Newby C, Amrani Y and Bradding P. A model of human lung fibrogenesis for the assessment of anti-fibrotic strategies in idiopathic pulmonary fibrosis. Scientific reports. 2018;8:342.