Functional Differentiation of Type II and Type I Collagen Articular Models in Synovial Fluid Film Formation and Recombinant Equine Lubricin Retention

Collagen type II (Col‐II) and collagen type I (Col‐I) are major components of articular cartilage present at different ratios at its surface. Understanding how each of these components mediates the assembly of molecular films derived from synovial fluid (SF), the lubricant of synovial joints, is critical to explain the loss of mechanical performance in pathological conditions, guide the design of biomaterial implants meant to be in contact with SF, and develop molecular therapies to restore SF properties. This work demonstrates that Col‐II articular surface model assists in scaffolding SF‐derived films, while Col‐I model lacks SF film scaffolding capabilities. However, when Col‐II and Col‐I are exposed to recombinant equine lubricin (rEqLub), an analog of the major boundary lubricant in SF, both adsorbed and retained similar amounts. These insights, deduced from quartz crystal microbalance with dissipation, diffuse reflectance circular dichroism, and atomic force microscopy, reveal possible mechanisms underlying the loss of mechanical performance of synovial joints in pathology, where Col‐I becomes the major collagenous component of the articular cartilage surface, as well as considerations for designing functional biomaterial implants. Furthermore, this work reinforces the idea of rEqLub as an intra‐articular osteoarthritis therapy with the ability to bind to Col‐II and Col‐I, irrespectively.