The Role Of MicroRNAs In The Peripheral Circadian Rhythms Of Cartilage

Bailey, Molly-Kay Bridget (2025) The Role Of MicroRNAs In The Peripheral Circadian Rhythms Of Cartilage. Doctoral thesis, University of East Anglia.

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Abstract

Osteoarthritis (OA) is a chronic joint disease characterised by gradual loss of the articular cartilage (AC), OA affects 7.6% of the global population and clinical interventions have been limited OA’s complex pathogenesis. The peripheral circadian clock and microRNAs (miR) are mediators of chondrocyte gene expression and, their deregulation is associated with AC degeneration in OA. An informed understanding of their intrinsic regulators may aid the development of novel therapies. Therefore, the purpose of this study has been to characterise co-regulation between the time keeping mechanism and microRNAs using an in-vitro and in-vivo model of AC.

Time keeping mechanisms pivots around core clock proteins oscillating in an autoregulatory transcriptional/translational feedback loop. In this study, clock genes CLOCK, RORα PER2 CRY2 were targeted by miR-455-5p and NPAS2 was targeted by mir-455-3p in 3’UTR luciferase reporter assays. No significant changes in the expression of circadian genes was identified in RNA-seq data of miR-455 KO mouse AC or miR-455 overexpression in SW1353 cells. miRNAs are likely subtle modulators of the clock gene expression with roles in determining circadian phase and amplitude.

Using a circadian small RNA sequencing model, 19.5% of chondrocyte miRNAs exhibit autonomous 24-hour oscillations in knee AC. Two-thirds of rhythmic miRNAs peaked within the animal’s rest-phase including miR-23a-5p and miR-30b-5p, miR-30d-3p and miR-30c-2-3p of the miR-30 family. The 5p arms of the miR-30 family share a conserved 6-mer seed region, though were differentially regulated by the clock diversifying their biological function. miR-17-5p and miR-18a-5p of the miR-17/92 cluster, were co-regulated and peaked at CT12. Circadian regulation of miR-17-5p was a conserved mechanism between knee and hip AC and transcripts oscillated in antiphase. miR-140-5p was stably expressed in knee AC, whilst miR-140-5p oscillated in SW1353 cells in-vitro. This demonstrates that the miRNAomes are differentially regulated between human and mouse and may evolve to accommodate different biophysical tissue demands. The miRNAome hosted miRNAs involved in AC physiology and putative targets were enriched for cartilage development and extracellular matrix ontologies. Thus, the miRNAome emerges as an effector of the clock mechanism. and future work will study the implications of daily fluctuations in miRNA abundance as on AC homeostasis.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	21 Oct 2025 08:42
Last Modified:	21 Oct 2025 08:42
URI:	https://ueaeprints.uea.ac.uk/id/eprint/100728
DOI:

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