Figure 5.

(A) Cell‐matrix interactions can regulate disc cell phenotype and bioactivity through stiffness‐ and ligand‐mediated effects, where rounded cells observed on “soft” matrices have increased production of nucleus pulposus (NP) markers and sGAG but flattened cells on “stiff” substrates can have decreased sGAG production. (B) Ligand presentation can overcome some stiffness‐mediated effects, as shown by Bridgen et al161 with primary human NP cells that only exhibit increased biosynthetic activity on soft substrates with select laminin‐mimetic peptides. NP cells were cultured on surfaces conjugated with LM‐111 (full length laminin), AG73 (syndecan peptide), P4 or P678 (α3 integrin receptor peptides), or AG10 (α2, α5, α6, β1 integrin‐recognizing peptide). (C) These select ligands can also produce differential NP marker expression independent of substrate stiffness