The Effect of Lubricin on Cartilage Friction and Wear

Jeffery Coles (Advisor: Zauscher)
Friday, March 19, 2010 - 12:00pm
Hudson 216
Seminar Contact(s): 
Jeffery Coles
Semester & Year: 
Spring 2010
Lubricin is a glycoprotein that contributes to boundary lubrication in joints and is also thought to have a role in protecting cartilage surfaces. Direct studies of joint protection by lubricin have been difficult but a lubricin null mouse has been developed recently, providing completely lubricin-free cartilage for study. We have shown that atomic force microscopy can be used for measurements of interfacial friction in the boundary lubrication regime and use this technique to measure friction directly on cartilage not expressing lubricin. We further use atomic force microscopy and histology to characterize stiffness and surface and subsurface morphology of these joints. While friction measured directly on lubricin null cartilage was only slightly lower than on wild type cartilage, surface structure and mechanical integrity were altered significantly. Lubricin null cartilage surfaces were significantly rougher, stiffness did not develop normally, and glycosaminoglycan (a core structural component of cartilage) concentration near cells was lost as joints developed. While reduction of friction is likely an important factor in lubricin's role in protecting cartilage, our measurements on lubricin null cartilage suggest that lubricin may additionally protect cartilage through other mechanisms and are working to measure this directly.