Novel high-resolution imaging modalities for monitoring in vitro models of cartilage degeneration and mesenchymal stem cell therapy in osteoarthritis
Duffy, Niamh
Duffy, Niamh
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Publication Date
2023-06-20
Type
Thesis
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Abstract
Osteoarthritis (OA) is a chronic disease of synovial joints characterized by progressive degeneration of articular cartilage causing pain and disability in millions of people worldwide. Current imaging systems used for clinical diagnosis of OA include conventional radiography and morphological magnetic resonance imaging. These modalities are limited to micrometer resolution and often cannot detect osteoarthritic changes in the joint until significant structural abnormalities are present and advanced disease established. Early events that occur during the onset of OA begin at the molecular and cellular level, with alterations in chondrocyte physiology and metabolic homeostasis driving compositional and structural changes, and eventually degradation of the cartilage extra-cellular matrix. Advanced imaging systems capable of elucidating these disease-associated structural changes occurring at sub micron to nanoscale levels, are required to facilitate early diagnosis of OA and timely intervention with disease modifying therapies. Mesenchymal stem cells (MSCs) have been proposed as one such disease modifying therapy for the treatment of OA, with delivery of MSCs shown to slow the progression of cartilage degeneration, yet our understanding of MSC mechanism of action remains incomplete. Molecular imaging and tracking of cells post administration to the OA joint could provide key information that may further our understanding of MSC therapy and enhance their clinical translation. The work presented in this thesis sought to investigate two novel high-resolution imaging modalities; the first (a nano-sensitive variant of optical coherence tomography referred to as nsOCT) in the detection of structural changes associated with in vitro cartilage development and degeneration in MSCs and the second (a functional variant of photoacoustic imaging referred to as multi-spectral optoacoustic tomography (MSOT)) combined with novel plasmonic gold nanostars (NS) for molecular tracking of MSCs following intra-articular (IA) delivery in a murine model of OA. The feasibility of nsOCT to monitor submicron changes in MSCs was shown using MSC chondrogenesis experiments and three-dimensional in vitro models of OA simulated by activation of the pathogen recognizing receptor NLRP3 inflammasome pathway with repetitive administration of S100A8/A9 danger signals. For in vivo tracking of MSCs using MSOT, MSCs were first labelled in vitro with gold NS and characterized to ensure no cellular phenotypic or functional alterations had occurred following NS labelling. A series of experiments assessing cell viability, tri-lineage differentiation, surface immunophenotype, response to therapeutic inflammatory cytokine licensing and gene expression profiles indicated no cytotoxicity of the label on MSCs. NS-labelled MSCs were then delivered via IA injection to a murine model of OA and safety and longitudinal monitoring of the cells for a period of 84 days was demonstrated using MSOT. Finally, post-mortem histological analysis showed retention of MSC potency in prevention of OA following NS labelling. Together, this work demonstrates the feasibility of nsOCT to monitor nano-sensitive OA-related structural changes in MSCs, and the future potential of this technique for diagnostic applications in OA, and MSOT as an effective imaging tool in combination with gold NS for monitoring the in vivo distribution of MSCs in a preclinical model of OA.
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Publisher
NUI Galway