OA Biology

ABSTRACT

Purpose: The field of osteoarthritis (OA) biology is rapidly evolving and brilliant progress has been made this year as well. Methods: Landmark studies of OA biology published in 2021 and early 2022 were selected through PubMed searches and classified by their molecular mechanisms, and it was largely divided into the intra-cellular mechanisms and the inter-compartment or inter-cellular interaction in OA progression. Results: The intra-cellular mechanisms involving OA progression included 1) Piezo1/TRPV4-mediated calcium signaling, 2) low grade inflammation by TLR-CD14-LBP complex and IKKβ-NFkB signaling, 3) PGRN/TNFR2/14-3-3ε/Elk-1 anabolic cascade, 4) G protein-coupled receptor (GPCR) signaling, 5) mechanical loading-cilia/Ift88-hedgehog signaling, 6) mitochondrial fission by ERK1/2-DRP1 pathway, and 7) hypoxia-DOT1L-H3K79 methylation pathway. The studies on inter-compartment or inter-cellular interaction in OA progression included the following subjects: 1) the anabolic role of Lubricin, a proteoglycan from superficial zone cells, 2) osteoclast-chondrocyte interaction via exosomal miRNA and sphingosine 1-phosphate (S1P), 3) αV integrin-mediated TGFβ activation by mechanical loading, 4) TGFβ-mediated suppression of sclerostin in osteocytes, 5) catabolic role of Flightless I as a DAMPs-triggering molecule, and 6) catabolic role of paracrine signaling from fat. Conclusions: Despite the disastrous Covid-19 pandemic situation, many outstanding studies have expanded the boundary of OA biology. They give us not only critical insight on pathophysiology, but also clue for the treatment of OA.