Hyaluronan initiates chondrogenesis mainly via CD44 in human adipose-derived stem cells.

Cell-matrix adhesion is one of the important interactions that regulates stem cell survival, self-renewal, and differentiation. Our previous report (Wu SC, Chang JK, Wang CK, Wang GJ, Ho ML. Biomaterials 31: 631-640, 2010) indicated that a microenvironment enriched with hyaluronan (HA) initiated and enhanced chondrogenesis in human adipose-derived stem cells (hADSCs). We further hypothesize that HA-induced chondrogenesis in hADSCs is mainly due to the interaction of HA and CD44 (HA-CD44), a cell surface receptor of HA. The HA-CD44 interaction was tested by examining the mRNA expression of hyaluronidase-1 (Hyal-1) and chondrogenic marker genes (SOX-9, collagen type II, and aggrecan) in hADSCs cultured on HA-coated wells. Cartilaginous matrix formation, sulfated glycosaminoglycan, and collagen productions by hADSCs affected by HA-CD44 interaction were tested in a three-dimensional fibrin hydrogel. About 99.9% of hADSCs possess CD44. The mRNA expressions of Hyal-1 and chondrogenic marker genes were upregulated by HA in hADSCs on HA-coated wells. Blocking HA-CD44 interaction by anti-CD44 antibody completely inhibited Hyal-1 expression and reduced chondrogenic marker gene expression, which indicates that HA-induced chondrogenesis in hADSCs mainly acts through HA-CD44 interaction. A 2-h preincubation and coculture of cells with HA in hydrogel (HA/fibrin hydrogel) not only assisted in hADSC survival, but also enhanced expression of Hyal-1 and chondrogenic marker genes. Higher levels of sulfated glycosaminoglycan and total collagen were also found in HA/fibrin hydrogel group. Immunocytochemistry showed more collagen type II, but less collagen type X, in HA/fibrin than in fibrin hydrogels. Our results indicate that signaling triggered by HA-CD44 interaction significantly contributes to HA-induced chondrogenesis and may be applied to adipose-derived stem cell-based cartilage regeneration.