The following is a summary of the “Ribosomal RNA-based epitranscriptomic regulation of chondrocyte translation and proteome in osteoarthritis,” published in the March 2023 issue of Osteoarthritis and Cartilage by Chabronova, et al.

Alterations in chondrocyte protein expression are required for extracellular matrix remodeling in osteoarthritic cartilage. Yet, the function of ribosomes in controlling translation in chondrocytes remains uncertain. They used an exploratory approach based on epitranscriptomic analysis of ribosomal RNA (rRNA) to examine ribosome heterogeneity in human articular chondrocytes and its potential significance for osteoarthritis. Around 5 non-OA primary human articular chondrocytes were exposed to osteoarthritic synovial fluid (14 donors, pooled, 20% v/v) for 14 days and then sequenced to analyze rRNA 2′-O-methylation profiling (RiboMethSeq). 

Using LentiCRISPRv2/Cas9, a pool of SW1353 SNORD71 KO cells was created. The use of dual-luciferase reporters allowed us to ascertain the beginning and accuracy of translation systematically. Collagen type I protein expression was assessed by using immunoblotting, and the cellular proteome was studied using LC-MS/MS. Polysome COL1A1 mRNA loading efficiency was evaluated by sucrose gradient ultracentrifugation and fractionation. Researchers found that the rRNA 2′-O-me profile of primary human articular chondrocytes was altered in specific locations due to exposure to synovial fluid from patients with osteoarthritis. 

They found 5 locations with varying degrees of 2′-O-me. 5.8S-U14 was one of the identified differential 2′-O-me sites, and its 2′-O-me status was aimed at reducing the abundance of its guide snoRNA SNORD71 (50% reduction, 95% CI [33-64%]). In turn, this accelerated translation of COL1A1 mRNA, leading to elevated amounts of COL1A1 protein (FC 1.7, 95% CI [1.3-2.0]) and a changed ribosome translation modus (e.g., CrPV IRES, FC 3, 95% CI [2.2-4.1]). Their findings reveal a unique hypothesis indicating that rRNA epitranscriptomic pathways are utilized by articular chondrocytes in the progression of osteoarthritis.