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Hypoxia and TGF-β3 synergistically mediate inner meniscus-like matrix formation by fibrochondrocytes.


Objective To investigate hypoxia and TGF-β3 effects on inner meniscus-like extracellular matrix (ECM) formation and related gene expression by meniscus fibrochondrocytes (MFCs). Design Aggregates of human MFCs were cultured for 3 weeks under hypoxia (3% O<sub>2</sub>) or normoxia (atmospheric O<sub>2</sub>) with or without TGF-β3 supplementation (10 ng/mL). Inner meniscus-like ECM formation was assessed by biochemistry, histology, and immunofluorescence. mRNA expression of ECM-related genes, TGF-β isoforms 1-3, and HIF-1 targets were assessed by qRT-PCR. Results Hypoxia and TGF-β3 supplementation synergistically induced inner meniscus-like ECM formation at the protein level with similar effects on ECM-related gene expression. Hypoxia alone did not induce an inner meniscus-like ECM-forming response nor upregulate mRNA of TGF-β isoforms. Expression of <i>HIF-1α</i> and HIF-1 target genes suggested that HIF-1 was a likely contributor to the observed synergistic interactions of hypoxia and TGF-β3 supplementation. Conclusion Hypoxia and TGF-β3 supplementation synergistically induced inner meniscus ECM formation by adult human MFCs. Hypoxia alone is insufficient to induce an inner meniscus ECM-forming response in this culture model.