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Differential gene expression analysis reveals pathways important in early post-traumatic osteoarthritis in an equine model.

ABSTRACT: Background: Post-traumatic osteoarthritis (PTOA) is a common and significant problem in equine athletes. It is a disease of the entire joint, with the synovium thought to be a key player in disease onset and progression due to its role in inflammation. The development of effective tools for early diagnosis and treatment of PTOA remains an elusive goal. Altered gene expression represents the earliest discernable disease-related change, and can provide valuable information about disease pathogenesis and identify potential therapeutic targets. However, there is limited work examining global gene expression changes in early disease. In this study, we quantified gene expression changes in the synovium of osteoarthritis-affected joints using an equine metacarpophalangeal joint (MCPJ) chip model of early PTOA. Synovial samples were collected arthroscopically from the MCPJ of 11 adult horses before (preOA) and after (OA) surgical induction of osteoarthritis and from sham-operated joints. After sequencing synovial RNA, Salmon was used to quasi-map reads and quantify transcript abundances. Differential expression analysis with the limma-trend method used a fold-change cutoff of log2(1.1). Functional annotation was performed with PANTHER at FDR?
Results: RNA was sequenced from 28 samples (6 preOA, 11 OA, 11 sham). "Sham" and "preOA" were not different and were grouped. Three hundred ninety-seven genes were upregulated and 365 downregulated in OA synovium compared to unaffected. Gene ontology (GO) terms related to extracellular matrix (ECM) organization, angiogenesis, and cell signaling were overrepresented. There were 17 enriched pathways, involved in ECM turnover, protein metabolism, and growth factor signaling. Network analysis revealed clusters of differentially expressed genes involved in ECM organization, endothelial regulation, and cellular metabolism.

Conclusions: Enriched pathways and overrepresented GO terms reflected a state of high metabolic activity and tissue turnover in OA-affected tissue, suggesting that the synovium may retain the capacity to support healing and homeostasis in early disease. Limitations of this study include small sample size and capture of one point post-injury. Differentially expressed genes within key pathways may represent potential diagnostic markers or therapeutic targets for PTOA. Mechanistic validation of these findings is an important next step.

SUBMITTER: McCoy AM

PROVIDER: S-EPMC7708211 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Differential gene expression analysis reveals pathways important in early post-traumatic osteoarthritis in an equine model.

McCoy Annette M AM Kemper Ann M AM Boyce Mary K MK Brown Murray P MP Trumble Troy N TN

BMC genomics 20201130 1

<h4>Background</h4>Post-traumatic osteoarthritis (PTOA) is a common and significant problem in equine athletes. It is a disease of the entire joint, with the synovium thought to be a key player in disease onset and progression due to its role in inflammation. The development of effective tools for early diagnosis and treatment of PTOA remains an elusive goal. Altered gene expression represents the earliest discernable disease-related change, and can provide valuable information about disease pat ...[more]

PMID: 33256611

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Project description: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.

Project description:Galectins are potent regulators of cell adhesion, growth and apoptosis in diverse cell types, including chondrocytes and synovial fibroblasts. Elevations in synovial fluid galectin-3 have been observed in rheumatoid arthritis, juvenile idiopathic arthritis and experimental inflammatory arthritis in animal models, whereas galectin-1 is thought to be protective. Less is known about galectins-1 and-3 in osteoarthritis (OA). Therefore, the purpose of this study was: (1) to determine whether galectin-1 and-3 synovial fluid concentrations and synovial membrane and cartilage histochemical staining were altered following osteochondral injury in an experimental equine osteoarthritis (OA) model and (2) to measure galectin-1 and-3 mRNA expression and synovial fluid concentrations in naturally occurring equine carpal OA. Synovial fluid galectin-1 and-3 concentrations were quantified using custom ELISAs in two research horse cohorts undergoing experimental OA induction (n = 5 and 4) and in a cohort of horses with naturally occurring carpal OA (n = 57). Galectin mRNA expression in synovial membrane and cartilage tissue obtained from carpal joints of horses with naturally occurring OA was measured using RT-qPCR, and galectin immunostaining was assessed in synovial membrane and osteochondral tissues in the experimental model (n = 5). Synovial fluid galectin-1 and-3 concentrations increased following experimental carpal osteochondral fragmentation. Cartilage galectin-1 mRNA expression increased with OA severity in naturally occurring disease. The superficial zone of healthy articular cartilage stained intensely for galectin-3 in sham-operated joints, whereas galectin-1 staining was nearly absent. Chondrocyte galectin-1 and-3 immunoreactivity increased following cartilage injury, particularly in galectin-1 positive chondrones. Galectins-1 and-3 are present in healthy equine synovial fluid and increase following post-traumatic OA. Healthy superficial zone chondrocytes express galectin-3, whereas galectin-1 chondrocyte staining is limited predominantly to chondrones and injured cartilage. Further work is needed to clarify the functions of galectins-1 and-3 in healthy and OA joints.

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Differential gene expression analysis reveals pathways important in early post-traumatic osteoarthritis in an equine model.

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Differential gene expression analysis reveals pathways important in early post-traumatic osteoarthritis in an equine model.

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