Triple-helical ligands for collagen-binding proteins improve cartilage extracellular matrix production in nasal...

The use of articular chondrocytes for cartilage repair is constrained by donor-site morbidity, poor proliferation, and difficulties to maintain a stable phenotype. As a result, nasal chondrocytes (NCs) have recently emerged as an alternative cell source. To better establish the potential of NCs in tissue engineering, we have explored their response to the activation of collagen-binding proteins (integrins, discoidin domain receptors (DDRs) andthe secreted protein acidic cysteine-rich (SPARC)) which are essential to cartilage homeostasis. Ligands for these proteins were synthesized as triple-helical peptides (THPs) that mimic the biological and structural properties of collagen, and were covalently linked to PEG or alginate hydrogels hosting human NCs. Compared to human adipose-tissue mesenchymal stem cells, NCs over-expressed chondrogenic markers, yielding higher Sox9 translocation and type II collagen production. THP ligands significantly improved the expression of key cartilage extracellular matrix components in hydrogels, at both the RNA and protein level, for up to 21 days of culture. In particular, THP ligands for DDRs and SPARC led to increased glycosaminoglycan and collagen deposition. In addition, THPs limited fibrocartilage formation, matrix metalloproteinase 13 expression and chondrocytes hypertrophy after 7 days of culture in hydrogels. This work introduces a biomimetic strategy to drive the early stages of the formation of an engineered cartilage tissue from NCs, by replicating key cell/collagen interactions. It provides a preliminary effort to combine an accessible cell source with functionalized biomaterials for cartilage repair.