Proteoglycan-4 (PRG4) serum concentration is lower in aged mice, and genetic deficiency impacts survival probability, blood parameters, and bone during aging.

Proteoglycan 4 (PRG4) is a mucin-like glycoprotein best known as a boundary lubricant of articular cartilage; however, it also has anti-inflammatory, anti-fibrotic, and immunomodulatory properties. Loss-of-function mutations in the PRG4 gene in humans result in Camptodactyly-Arthropathy-Coxa vara-Pericarditis (CACP), a rare disease in which patients often require joint replacements at young ages. However, it remains unknown how circulating PRG4 levels change with age or how PRG4 deficiency affects aging.