Engineered Human Meniscus in Modeling Sex Differences of Knee Osteoarthritis in Vitro

This study developed a human tissue-engineered meniscus model to examine how mechanical loading versus unloading regulates osteoarthritis (OA)-related responses and whether these responses differ by biological sex. Meniscus fibrochondrocytes from non-OA female and male donors were seeded into porous type I collagen scaffolds and precultured for 2 weeks in chondrogenic medium, then exposed for 3 additional weeks to either cyclic hydrostatic pressure (CHP), simulated microgravity (SMG), or static controls. CHP promoted a more chondrogenic phenotype, increasing cartilage matrix markers (ACAN,COL2A1) and GAG/DNA and supporting higher construct wet weight, while generally reducing hypertrophic tendencies compared with SMG. In contrast, SMG induced more OA-like features, including lower GAG/DNA and stronger hypertrophy-associated signals (e.g., increased collagen X staining trends). RNA-seq showed that CHP and SMG modulated largely distinct gene sets and enriched OA-relevant pathways (e.g., mineral absorption,Wnt,HIF-1,IL-17), with notable sex-dependent differences in fold-change magnitude and direction for multiple mechanosensitive and pathway genes (including strong female-biased induction of FOSB under CHP). Overall, the combined CHP and SMG paradigm provides a mechanically tunable in vitro platform for probing early molecular events in knee OA and sex-dependent mechanobiology in meniscus tissue.