Abstract

Intervertebral disc (IVD) degeneration is one of the main contributing factors to low back pain (LBP), the leading cause of years lived in disability worldwide. The degenerative processes in the IVD tissue are characterized by the metabolic dysregulation of IVD cells and aberrant mechanical loading. The major hallmarks of this multifactorial pathology are the degradation of the extracellular matrix (ECM), inflammation, and cell loss. Inflammation has been specifically linked to the development of discogenic LBP, as increased secretion of pro-inflammatory cytokines can cause the infiltration of immune cells and nerve fibers. Toll-like receptors (TLR) are key regulators of inflammation, amongst which TLR-2 is known for its increased expression in degenerated IVD cells and its contribution to IVD degeneration upon activation by affecting gene expression and intracellular signaling. As potent post-transcriptional regulators, microRNAs can modulate numerous cellular mechanisms including inflammation, catabolism, apoptosis, and senescence. Most importantly, the dysregulation of microRNAs has been linked to numerous pathologies, including multiple degenerative diseases. This project aims to study miRNAs in the context of TLR-2 activation, inflammation, and mechanosensing for a better understanding of TLR-2 dysregulation and IVD mechano-immunosensing. As a first step, TLR-2-associated microRNAs were identified by activation of the receptor followed by small RNA sequencing. The impact of TLR-2 activation on miRNA dysregulation was investigated in degenerated and non-degenerated IVD cells. Thereafter, the functional role of miRNA-155-5p in inflammation and degeneration was studied. To that end, the effect of up/downregulation of this miRNA on ECM-degrading proteins, pro-inflammatory cytokines, intracellular signaling, and neurotrophins was analyzed. Furthermore, the role of miRNA 155 5p in mechanosensing was determined by subjecting IVD cells to cyclic stretching. The miR-155-5p was consistently upregulated in degenerated and non-degenerated IVD cells following TLR-2 activation and its expression contributed to the expression of pro-inflammatory cytokines, neurotrophins and the activation of inflammatory signaling pathways. Overall, the project identified TLR-2-associated miRNAs and investigated their role in IVD degeneration, inflammation and mechanosensing, for a better understanding of underlying disease mechanisms and contributing to the identification of new therapeutic targets for IVD degeneration and LBP.

Publication Date

12-8-2023

Document Type

Dissertation

Student Type

Graduate

Degree Name

Biomedical and Chemical Engineering (Ph.D)

Department, Program, or Center

Biomedical Engineering

College

Kate Gleason College of Engineering

Advisor

Karin Wuertz-Kozak

Advisor/Committee Member

Vinay Abhyankar

Advisor/Committee Member

Thomas R. Gaborski

Campus

RIT – Main Campus

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