Hyaluronic acid promotes proliferation and migration of human meniscus cells via a CD44-dependent mechanism.

Treatment of meniscal injury is important for osteoarthritis (OA) prevention. Meniscus cells are divided between inner and outer cells, which have different characteristics and vascularity. We evaluated the effects of hyaluronic acid (HA) on the proliferation and migration of human inner and outer meniscus cells, and investigated the underlying healing mechanisms. Lateral menisci from 18 patients who underwent total knee arthroplasty were used. Meniscus cells were harvested from the outer and inner menisci and evaluated using migration and proliferation assays after treatment with HA or chondroitin sulfate (CS). The effects of HA on prostaglandin E2 (PGE2)-induced apoptosis and gene expression were evaluated. Cell migration and proliferation were increased by HA in a concentration-dependent manner, in both inner and outer meniscus cells. PGE2-induced apoptosis and caspase-3/7 activity were suppressed by HA in both inner and outer meniscus cells, and these effects were blocked by an anti-CD44 antibody. COL2A1 and ACAN mRNA levels were upregulated following HA treatment of inner meniscus cells. MMP13 mRNA was downregulated following CS stimulation of both inner and outer meniscus cells. These results suggest that CS treatment suppresses the inflammatory reaction rather than providing meniscal restoration. The phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways were activated by HA in both types of meniscus cells; these effects were blocked by treatment with an anti-CD44 antibody. HA promoted human meniscus regeneration by inhibiting apoptosis, promoting cell migration, and accelerating cell proliferation, potentially through the PI3K/MAPK pathway via the CD44 receptor.