Thursday, March 15, 2018
4:00 pm
Spalding Laboratory 106 (Hartley Memorial Seminar Room)

Chemical Engineering Seminar

Biolubrication and Gene Regulation: A Physicists Approach to Osteoarthritis
Jacob Klein, Professor, Department of Materials and Interfaces, Weizmann Institute of Science

The major mammalian joints such as hips or knees are uniquely-efficient tribological systems. In health, the articular cartilage coating them presents the most remarkably lubricated surfaces known in nature. They can slide past each other with friction coefficients down to  0.001 or lower under pressures of 100 atmospheres or more at sliding velocities from rest to several cm/second (shear rates ca. 1 – 106 sec-1), and they do this over a lifetime. No man-made surfaces can approach this. But when this lubrication breaks down, the result can be degradation of the articular cartilage, and onset of osteoarthritis (OA), a debilitating joint disease affecting millions. An understanding of the origins of the very efficient lubrication at the cartilage surface is thus essential for better treatments of OA.

The talk will describe progress in our understanding of cartilage friction based on the recently-proposed model whereby lubricin, hyaluronic acid and phospholipids act together, each with a different role, to form boundary layers exposing highly-hydrated phosphocholine headgroups at the articular cartilage surface which provide the lubrication via the hydration lubrication paradigm1-6. The effect of the low friction not only on the wear and tear of the cartilage but also on shear of the chondrocyte cells embedded within it, and the ensuing mechanotransductive effects on gene regulation, is considered as part of the underlying picture for the well-being of the joints.

1. Raviv, U. and Klein, J., 'Fluidity of bound hydration layers' – Science  297, 1540-1543 (2002)

2. Briscoe, W.H., Titmuss, S., Tiberg, F., McGillivray, D.J., Thomas, R.K., Klein, J., 'Boundary lubrication under water', Nature 444, 191-194 (2006)

3. Chen, M., Briscoe, W.H., Armes, S.P. and Klein, J., 'Lubrication at physiological pressures by polyzwitterionic brushes', Science, 323 1698-1702 (2009)

4. Seror, J., Zhu, L., Goldberg, R., Day, A.J. and Klein J., 'Supramolecular synergy in the boundary lubrication of synovial joints' – Nature Communications, | 6:6497 | DOI: 10.1038/ncomms7497 (2015)

5. Zhu, L., Seror, J., Day, A.J., Kampf, N. and Klein J., 'Ultra-low friction between boundary layers of hyaluronan-phosphatidylcholine complexes', Acta Biomaterialia, 59, 283-292 (2017)

6. Klein, J., 'Cartilage boundary lubrication and joint homeostasis', Nature Reviews Rheumatology, (2018, in press)

Contact Sohee Lee at 626-395-4193
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