Article: Eguiluz, RCA; Cook, SG; Brown, CN; Wu, F; Pacifici, NJ; Bonassar, LJ; Gourdon, D; (2015) “Fibronectin Mediates Enhanced Wear Protection of Lubricin During Shear”, Biomacromolecules, 16(9):2884-2894
Abstract: Fibronectin (FN) is a glycoprotein found in the superficial zone of cartilage; however, its role in the lubrication and the wear protection of articular joints is unknown. In this work, we have investigated the molecular interactions between FN and various components of the synovial fluid such as lubricin (LUB), hyaluronan (HA), and serum albumin (SA), which are all believed to contribute to joint lubrication. Using a Surface Forces Apparatus, we have measured the normal
(adhesion/repulsion) and lateral (friction) forces across layers of individual synovial fluid components physisorbed onto FN-coated mica substrates. Our chief findings are (i) FN strongly tethers LUB and HA to mica, as indicated by high and reversible long-range repulsive normal interactions between surfaces, and (ii) FN and LUB synergistically enhance wear protection of surfaces during shear, as suggested by the structural robustness of FN+LUB layers under pressures up to about 4 MPa. These findings provide new insights into the role of FN in the lubricating properties of synovial fluid components sheared between ideal substrates and represent a significant step forward in our understanding of cartilage damage involved in diseases such as osteoarthritis.
Funding Acknowledgement: NSF [DMR-1352299]; CONACYT ; Cornell Center for Materials Research [NSF DMR-1120296]
Funding Text: This research was supported by the NSF under Award DMR-1352299 (to D.G.), CONACYT under Award 308671 (to R.C.A.E.), the Cornell Center for Materials Research through Award Number (NSF DMR-1120296), and the Cornell University Biotechnology Resource Center (BRC) for data collected on the Zeiss LSM 710 Confocal (NIH 1S10RR025502-01). We also thank Dr. Kirk J. Samaroo, Dr. Mingchee Tan, Edward Bonnevie, Heidi Reesink, and Prof. Dave Putnam for enriching discussions.