sST2 as a candidate for dual biosensing with cTnI in presentations of myocardial infarction

Thesis

sST2 is an emerging biomarker of interest for cardiovascular stress, where this thesis aims to isolate specific pathologies contributing to its serous release. On a molecular level, sST2 is a decoy receptor that intercepts IL-33 and sequesters its natural association with the transmembrane isoform of ST2: ST2L. This pathway, if not inhibited, signals to a cascade of transcription factors that upregulate cardioprotective chemokines and cytokinesto reduce the severity of adverse remodelling processes such as hypertrophy post-injury. The work described in this thesis has a significant focus of developing an applicable solution of sST2 measurements in instances of MI. This was facilitated via a partnership with Osler Diagnostics, a point of care immunoassay development start-up (an Oxford University spinout), where a duplex assay for sST2 and cTnI was created, enabling a rapid solution for measuring both biomarkers simultaneousl

Chapter 2 describes the optimisation of this complex assay in 96-well plate ELISA format with novel techniques for improving sensitivity and specificity of biomarker detection, with the adoption of different detection methods for distinguishing each signal. The resulting assay achieved an LoD of 20ng/L for cTnI and 10.3ng/mL for sST2; this assay was then used to analyse biomarker levels in a clinical cohort of 215 MI patients, where sST2 levels were significantly (P<0.0001) higher in patients diagnosed with MI in comparison to a healthy “normals” cohort (n=37). In addition, sST2 had similar predictive ability for HF post-MI in comparison to NT-proBNP (AUC of 0.70 and 0.72, respectively). Chapter 3 involved investigative experiments pertaining to the molecular pathways involved in sST2 upregulation, and the effects of sST2 expression according to two injury models. Current literature disputes the attribution of MI and HF to upregulation of sST2, and so this chapter aimed to isolate the contribution of both diseases to sST2 upregulation. These injury models utilised AngII to simulate HF, and H2O2 to induce ischemic injury, where sST2 on the transcript and protein level showed increased expression. Additionally, an in vivo model subject to coronary artery ligation characterised, for the first time, the release profile of sST2 post-MI in a controlled environment. This showed a 2.95-fold increase in sST2 released into sera within 24 hours of injury.

In conclusion, sST2 is a promising biomarker for MI and injury severity, providing additional information to what is already diagnostically available. More research should be conducted into sST2 and MI to continue building a dataset convincing enough to acquire commercial interest and funding to propel the addition of sST2 to MI investigative recommendations.

Authors: Jones, O

• DOI: 10.5287/ora-2rye0da7z
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English