Bioactive sulfated galactans from Gracilaria fisheri promote chondrogenic activity via integrin-β1/FAK/Akt signaling in human chondrocytes

Osteoarthritis (OA) is characterized by progressive cartilage degradation and limited tissue regeneration, commonly affecting older adults. Current treatment strategies mainly alleviate symptoms without effectively restoring cartilage integrity. Sulfated polysaccharides derived from marine algae have attracted attention for their potential biological effects in promoting cartilage repair. This study examined the chondrogenic activity of sulfated galactans (SG) isolated from the marine red alga Gracilaria fisheri in human C28/I2 chondrocytes, using transforming growth factor-beta 3 (TGF-β3) as a comparative control. SG treatment significantly increased the synthesis of essential cartilage extracellular matrix (ECM) components, such as type II collagen and aggrecan. These effects were mediated through the integrin β1/FAK/Akt signaling pathway, as demonstrated by reduced ECM synthesis following treatment with the Akt inhibitor, MK2206. Additionally, SG improved chondrocyte adhesion and proliferation. These results suggest that sulfated galactans from Gracilaria fisheri may support cartilage ECM synthesis and exhibit potential as biologically active components for osteoarthritis management.