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Review
. 2022 May 2;42(1):14.
doi: 10.1186/s41232-022-00202-0.

The superficial zone of articular cartilage

Taku Saito  1
Affiliations
Review

The superficial zone of articular cartilage

Taku Saito. Inflamm Regen. .

Abstract

The superficial zone of articular cartilage contributes to smooth joint motion through the production of proteoglycan 4 (PRG4), also known as lubricin. Recent studies indicate novel effects of PRG4 as a signaling molecule, other than a simple extracellular matrix protein. Additionally, the accumulating evidence displays that various molecules and signaling pathways are involved in regulating the superficial zone and PRG4 expression. In addition, Prg4-expressing cells include a progenitor population of articular chondrocytes. Several non-clinical and clinical studies have shown that PRG4 and related molecules are promising candidates for disease-modifying drugs for treating osteoarthritis. Since PRG4 is also expressed in the synovium, tendons, and ligaments, further studies of PRG4-related pathways and PRG4-positive cells may elucidate the mechanisms underlying joint homeostasis.

Keywords: Articular cartilage; Lubricin; Osteoarthritis; Superficial zone.

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Conflict of interest statement

The author declares no competing interests.

Figures

Fig. 1
Fig. 1
Schematic diagram representing the molecular pathway in which PRG4 suppresses the differentiation of SFZ cells, osteophyte formation, and ectopic ossification
Fig. 2
Fig. 2
Schematic diagram representing the molecular pathways that regulate PRG4 expression
See this image and copyright information in PMC

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