Equine synovial fluid small non-coding RNA signatures in early osteoarthritis

Abstract

Background Osteoarthritis remains one of the greatest causes of morbidity and mortality in the equine population. The inability to detect pre-clinical changes in osteoarthritis has been a significant impediment to the development of effective therapies against this disease. Synovial fluid represents a potential source of disease-specific small non-coding RNAs (sncRNAs) that could aid in the understanding of the pathogenesis of osteoarthritis. We hypothesised that early stages of osteoarthritis would alter the expression of sncRNAs, facilitating the understanding of the underlying pathogenesis and potentially provide early biomarkers. Methods Small RNA sequencing was performed using synovial fluid from the metacarpophalangeal joints of both control and early osteoarthritic horses. A group of differentially expressed sncRNAs was selected for further validation through qRT-PCR using an independent cohort of synovial fluid samples from control and early osteoarthritic horses. Bioinformatic analysis was performed in order to identify putative targets of the differentially expressed microRNAs and to explore potential associations with specific biological processes. Results Results revealed 22 differentially expressed sncRNAs including 13 microRNAs; miR-10a, miR-223, let7a, miR-99a, miR-23b, miR-378, miR-143 (and six novel microRNAs), four small nuclear RNAs; U2, U5, U11, U12, three small nucleolar RNAs; U13, snoR38, snord96, and one small cajal body-specific RNA; scarna3. Five sncRNAs were validated; miR-223 was significantly reduced in early osteoarthritis and miR-23b, let-7a-2, snord96A and snord13 were significantly upregulated. Significant cellular actions deduced by the differentially expressed microRNAs included apoptosis (P < 0.0003), necrosis (P < 0.0009), autophagy (P < 0.0007) and inflammation (P < 0.00001). A conservatively filtered list of 57 messenger RNA targets was obtained; the top biological processes associated were regulation of cell population proliferation (P < 0.000001), cellular response to chemical stimulus (P < 0.000001) and cell surface receptor signalling pathway (P < 0.000001). Conclusions Synovial fluid sncRNAs may be used as molecular biomarkers for early disease in equine osteoarthritic joints. The biological processes they regulate may play an important role in understanding early osteoarthritis pathogenesis. Characterising these dynamic molecular changes could provide novel insights on the process and mechanism of early osteoarthritis development and is critical for the development of new therapeutic approaches.

Ribosome dysfunction in osteoarthritis

“…The balance between cap-dependent and IRES-dependent translation is amongst others determined by specific snoRNA-mediated PTMs on the rRNA [ 18 ] and by expression of IRES-transacting factors (ITAFs). With the mapping of differential expression of snoRNAs [ 14 , 22 ▪▪ , 23 , 26 , 50 ] and rRNA PTMs [ 25 ], as well as high-resolution proteomics [ 30 ▪▪ , 39 ] in cells from joint tissues as a function of ageing [ 51 , 52 ] and osteoarthritis, it is expected that insight into this level of ribosome translation regulation will further unfold. The existence of other mechanisms of preferential translation in cell types from the joint is only starting to emerge.…”

Small non-coding RNA landscape of extracellular vesicles from a post-traumatic model of equine osteoarthritis

“…We recently identified that differential expression (DE) of small nucleolar RNAs (snoRNAs) contributes to this imbalance, a key mechanism in OA ( 6 , 7 ). We require biomarkers to identify early OA before cartilage ECM is irreversibly degraded, and our group has identified small non-coding RNAs (sncRNAs) distinguishing early equine OA synovial fluid (SF) ( 8 ). These include microRNAs (miRNAs) and snoRNAs, which are functional RNA molecules that are transcribed from DNA but do not translate into proteins ( 9 ).…”

“…We have identified DE sncRNAs in ageing equine and human and OA human cartilage ( 15 , 16 ), equine OA SF ( 8 ), and mouse serum ( 17 , 18 ). In human OA, others have identified sncRNAs in joint tissues, plasma, and SF as potential therapeutics ( 19 , 20 ) or possible OA biomarkers ( 18 , 21 – 24 ).…”

Circulating MicroRNAs Highly Correlate to Expression of Cartilage Genes Potentially Reflecting OA Susceptibility—Towards Identification of Applicable Early OA Biomarkers

“…Levels of HMGB2 in cartilage were here identified in strong inverse correlation to levels of plasma miR-23b-5p, and we found that it was also previously validated as a target of miR-23b-5p. For that matter, levels of miR-23b were previously shown to be increased in equine synovial fluid early in OA [ 41 ]. Founded by the vision of OA as a whole joint disease, it is tempting to speculate that the initiating joint pathology involves signaling between the synovium and synovial fluid, the cartilage, and into the circulation.…”