BioProject

Objective: To quantify gene expression changes in the synovium of osteoarthritis-affected joints in an equine metacarpophalangeal joint (MCPJ) chip model specifically designed to recapitulate early post-traumatic osteoarthritis (PTOA). Design: Synovial samples were collected arthroscopically from the MCPJ of 11 adult horses before (pre-OA) and after (OA) surgical induction of osteoarthritis and from sham-operated joints. Briefly, in this model, an osteochondral fragment is created in one randomly chosen MCPJ at the proximal dorsomedial aspect of the first phalanx. The fragment is replaced in the fragment bed after creation so that subchondral bone is not exposed to the opposing cartilage surface. The opposite MCPJ is sham-operated. After a two week recover period, the horses are treadmill-exercised for 14 weeks and then the osteochondral fragment is removed (16 weeks after creation). Synovial tissue samples were collected arthroscopically from the MCPJ of eleven adult horses before (pre-OA) and 16 weeks after (OA) experimental induction of OA as well as from the sham-operated joints (sham). After sequencing of synovial RNA, Salmon was used to quasi-map reads to the reference genome and quantify transcript abundances. Differential expression analysis was performed with the limma-treat method using a fold-change cutoff of 1.1. Functional annotation was performed with PANTHER and Reactome at FDR < 0.05. Results: RNA was successfully extracted from 28 samples (6 pre-OA, 11 OA, 11 sham). Sequencing yielded 15.7-29.4 million paired-end reads per sample. “Sham” and “pre-OA” were not different and were grouped. 321 genes were upregulated and 351 genes were downregulated in OA synovium compared to unaffected. Gene ontology (GO) terms related to extracellular matrix (ECM) organization and growth factor binding were overrepresented among differentially expressed genes. There were 20 significantly enriched pathways; these included pathways involved in ECM turnover, O-glycosylation of TSR domain-containing proteins, and growth factor signaling. Conclusions: Most enriched pathways and overrepresented GO terms reflect a state of high metabolic activity and tissue turnover in OA-affected tissue, suggesting efforts at healing and restoring homeostasis. Limitations of this study include a small sample size and capture of a single point post-injury. Differentially expressed genes falling within key pathways may represent potential diagnostic markers or therapeutic targets for PTOA. Overall design: Synovial samples were collected arthroscopically from the MCPJ of 11 adult horses before (pre-OA) and after (OA) surgical induction of osteoarthritis and from sham-operated joints. Briefly, in this model, an osteochondral fragment is created in one randomly chosen MCPJ at the proximal dorsomedial aspect of the first phalanx. The fragment is replaced in the fragment bed after creation so that subchondral bone is not exposed to the opposing cartilage surface. The opposite MCPJ is sham-operated. After a two week recover period, the horses are treadmill-exercised for 14 weeks and then the osteochondral fragment is removed (16 weeks after creation). Synovial tissue samples were collected arthroscopically from the MCPJ of eleven adult horses before (pre-OA) and 16 weeks after (OA) experimental induction of OA as well as from the sham-operated joints (sham). RNA was successfully extracted from 28 samples (6 pre-OA, 11 OA, 11 sham)