Tew, S. R. | bioRxiv Science

bioRxiv2025

Characterising the effect of age and sex on post-transcriptional regulation in synovial joint tissues

Age and sex are major risk factors for joint degeneration and disease susceptibility. While epigenetic and post-transcriptional mechanisms are known to be influenced by these factors, their effects on mRNA kinetics and configuration in musculoskeletal tissues remain poorly defined. To address this gap, we used an equine model to examine how age and sex impact mRNA stability in joint tissues. We measured global transcript half-life in primary chondrocytes from young and old female and young male horses using SLAM-seq. Polyadenylation patterns were additionally analysed in cartilage and synovium across age groups. Our findings demonstrated that age and sex exert distinct regulatory influences on post-transcriptional gene expression in joint tissues. Specifically, ageing alters polyadenylation site usage and transcript turnover in cartilage, even in absence of overt pathology, suggesting that molecular ageing may precede and predispose to joint degeneration. We also found that mean RNA half-life differed significantly between young females and males, with male chondrocytes showing greater transcript stability. This difference suggests that sex-specific regulatory mechanisms may influence RNA stability, which could contribute to differential susceptibility to joint degeneration. Together, these results point to age and sex as key drivers of post-transcriptional regulation with potential roles in shaping joint health trajectories. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=79 SRC="FIGDIR/small/677035v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@99310borg.highwire.dtl.DTLVardef@162ee69org.highwire.dtl.DTLVardef@125108org.highwire.dtl.DTLVardef@860828_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2022

Analysis of RNA polyadenylation in healthy and osteoarthritic human articular cartilage

An important transcript structural element is its 3 polyadenylated (polyA) tail, which defines the 3 boundary of the transcripts genetic information and is necessary for transcript stability. The position of the polyA tail can vary, with multiple alternatively polyadenylated (APA) transcripts existing for a single gene. This can lead to different length transcripts which can vary in their 3 regulatory domains and even by inclusion or exclusion of protein-coding introns. The distribution of polyA tail location on articular chondrocyte transcripts has not been examined before and this study aimed to be the first to define polyadenylation events in human chondrocytes using age-matched healthy and osteoarthritic knee articular cartilage samples. Total RNA was isolated from frozen tissue samples and analysed using the QuantSeqReverse 3 RNA Sequencing approach, where each read runs 3 to 5 from within the polyA tail into the transcript and will contains a distinct polyA site. Initial analysis of differential expression of overall transcript abundance identified by the reads showed significant disruption to transcript levels when healthy samples were compared to osteoarthritic ones. As we expected, differentially regulated genes were enriched with functionalities that were strongly associated with joint pathology. As part of this analysis, we also identified a substantial number of differentially expressed long non-coding RNAs that had not been linked to osteoarthritis before. Subsequent examination of polyA site data allowed us to deifne the extent of site usage across all the samples. This included identification of chondrocyte genes that exhibited the greatest amount polyA site variation. When comparing healthy and osteoarthritic samples, we found that differential use of polyadenylation sites was modest. However, of the small number of genes affected, there was clear potential for the change in polyadenylation site usage elicited by pathology to have functional relevance. We examined two genes, OSMR and KMT2A, in more detail, defining how APA affects transcript turnover and then, in the case of OSMR, identifying that APA is sensitive to inflammatory cytokine stimulation. Overall, we have characterised the polyadenylation landscape of human knee articular chondrocytes but can conclude that osteoarthritis does not elicit a widespread change in their polyadenylation site usage. This finding differentiates knee osteoarthritis from pathologies such as cancer where APA is more commonly observed.

molecular biology↗