Fig. 6. FXIIIA induction of type X collagen is associated with FAK and p38 MAP kinase phosphorylation and dependent upon the 1-integrin subunit. (A) Type X collagen. Aliquots of 10⁵ human articular chondrocytes were starved and pre-treated for 2 hours with 1 µg/ml of IgG control, β1-integrin subunit or 1-integrin-subunit-blocking (FB12) antibodies in serum-free DMEM and then incubated for the indicated times with 100 ng/ml sTG2 or sFXIIIA, with type X collagen assessed by western blotting of cell lysates as above. (B) FAK and p38 MAP kinase phosphorylation. Aliquots of 10⁵ cells were starved for 2 hours in serum-free DMEM and then incubated for the indicated times with 100 ng/ml sTG2 or sFXIIIA and 1 µg/ml of 1-integrin-subunit-blocking antibody (FB12) where indicated, with cell lysates examined for FAK and p38 phosphorylation by western blotting. Representative of results from three experiments employing three separate donors.