Development of miRNA Therapeutics Targeting Intervertebral Disc Degeneration

Abstract

Low back pain is one of the leading causes of disability worldwide, with its prevalence growing. Believed to be predominately caused through degeneration of the intervertebral disc (IVD), current treatments are conservative and do not target the homeostatic imbalance at the core of the degradative cascade. This dysregulation is characterised by a disruption to and loss of key extracellular matrix (ECM) proteins, with a concurrent aggravated inflammatory and catabolic response. microRNAs (miRNAs) can regulate the expression of multiple target genes, making them an attractive treatment option. Subsequently, this thesis aims to explore miRNA approaches with the aim of developing a translationally relevant injectable therapy that will impart a multimodal effect: suppression of the inflammatory milieu and promoting of regenerative ECM factors. Firstly, this work screened miRNAs identified from the literature with the aim of identifying the most suitable for IVD delivery, systematically evaluating their anti-catabolic and pro-matrix potential. Concurrently two cell penetrating peptides (CPPs) were assessed for optimal delivery to the nucleus pulposus (NP) of the IVD. To enhance therapeutic the miRNAs were co-delivered in pairs to investigate possible synergistic effects. Secondly, this thesis explored adjunct stimulation in combination with dual-miRNA treatment. For this purpose, human platelet lysate (HPL), a clinically established regenerative aid in the orthopaedics and musculoskeletal field, was delivered alongside the selected dual-miRNA. Cell transplantation to the IVD has been suggested as a method to replace the native population that was depleted through degeneration. Therefore, the third aim of this work was to compare dual-miRNA stimulation of NP and bone marrow derived stem cells (BMSCs) to analyse the most appropriate cell source for IVD delivery. Finally, the optimised dual-miRNA formulation was evaluated in a preclinical large animal model of mild IVD degeneration, to determine its safety, efficacy, and translational feasibility. Overall, this work highlights miRNAs as a promising component to injectable therapies for IVD degeneration, exploring their utility alone, in pairs, and combined with external factors, both HPL and cells. By integrating a robust experimental framework with physiologically relevant culture and preclinical models the findings presented here support the translational potential of miRNA-based therapies for clinical applications to target IVD degeneration.