Engineering lubrication in articular cartilage.

Department of Orthopaedic Surgery, Lawrence Ellison Center for Tissue Regeneration and Repair, School of Medicine, University of California, Davis, Sacramento, California, USA.
Tissue Engineering Part B Reviews (Impact Factor: 4.64). 09/2011; 18(2):88-100. DOI: 10.1089/ten.TEB.2011.0394
Source: PubMed

ABSTRACT Despite continuous progress toward tissue engineering of functional articular cartilage, significant challenges still remain. Advances in morphogens, stem cells, and scaffolds have resulted in enhancement of the bulk mechanical properties of engineered constructs, but little attention has been paid to the surface mechanical properties. In the near future, engineered tissues will be able to withstand and support the physiological compressive and tensile forces in weight-bearing synovial joints such as the knee. However, there is an increasing realization that these tissue-engineered cartilage constructs will fail without the optimal frictional and wear properties present in native articular cartilage. These characteristics are critical to smooth, pain-free joint articulation and a long-lasting, durable cartilage surface. To achieve optimal tribological properties, engineered cartilage therapies will need to incorporate approaches and methods for functional lubrication. Steady progress in cartilage lubrication in native tissues has pushed the pendulum and warranted a shift in the articular cartilage tissue-engineering paradigm. Engineered tissues should be designed and developed to possess both tribological and mechanical properties mirroring natural cartilage. In this article, an overview of the biology and engineering of articular cartilage structure and cartilage lubrication will be presented. Salient progress in lubrication treatments such as tribosupplementation, pharmacological, and cell-based therapies will be covered. Finally, frictional assays such as the pin-on-disk tribometer will be addressed. Knowledge related to the elements of cartilage lubrication has progressed and, thus, an opportune moment is provided to leverage these advances at a critical step in the development of mechanically and tribologically robust, biomimetic tissue-engineered cartilage. This article is intended to serve as the first stepping stone toward future studies in functional tissue engineering of articular cartilage that begins to explore and incorporate methods of lubrication.


Available from: Kyriacos Athanasiou, Jun 07, 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: Low friction coefficients are required for biomaterials in order for them to be used in the repair of articular cartilage. In the present study, polyvinyl alcohol (PVA)/polyvinylpyrrolidone (PVP) hydrogels were synthesized with different degrees of polymerization in the PVA and different polymer concentrations. A repeated freezing-thawing method was used to prepare them. The microstructures of the synthesized compositions gave an insight into the effects of the preparation processes and properties of the hydrogel. The influences of PVA polymerization and polymer concentration on the swelling behavior of PVA/PVP hydrogels in phosphate-buffered saline (PBS) were examined. The friction coefficients of PVA/PVP hydrogels against stainless steel were measured using a rotating ball-on-plate tribometer. The testing variables were: (a) polymerization degree of PVA, (b) polymer concentration, (c) lubrication condition (dry, physiological saline, and bovine serum), (d) sliding speed and (e) load. With increasing polymer concentration and polymerization degree of PVA, the inner structures of the hydrogels tended to be denser. An effective drop in swelling ratio was observed for hydrogels in PBS. The friction coefficient increased with an increase in polymerization degree of PVA, while it decreased with an increase of polymer concentration in the low load region and under liquid lubrication. At long testing times, the friction coefficient of hydrogels under dry sliding conditions increased rapidly owing to a lack of the interstitial fluid, while the friction coefficient remained stable during the entire friction test when fluid lubricated. Biphasic lubrication is proposed to be the key reason for maintaining a low friction coefficient level for PVA/PVP hydrogel when sliding against stainless steel.
    Wear 07/2013; 305(1-2):280-285. DOI:10.1016/j.wear.2012.12.020 · 1.86 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Interest in osteochondral repair has been increasing with the growing number of sports-related injuries, accident traumas, and congenital diseases and disorders. Although therapeutic interventions are entering an advanced stage, current surgical procedures are still in their infancy. Unlike other tissues, the osteochondral zone shows a high level of gradient and interfacial tissue organization between bone and cartilage, and thus has unique characteristics related to the ability to resist mechanical compression and restoration. Among the possible therapies, tissue engineering of osteochondral tissues has shown considerable promise where multiple approaches of utilizing cells, scaffolds, and signaling molecules have been pursued. This review focuses particularly on the importance of scaffold design and its role in the success of osteochondral tissue engineering. Biphasic and gradient composition with proper pore configurations are the basic design consideration for scaffolds. Surface modification is an essential technique to improve the scaffold function associated with cell regulation or delivery of signaling molecules. The use of functional scaffolds with a controllable delivery strategy of multiple signaling molecules is also considered a promising therapeutic approach. In this review, we updated the recent advances in scaffolding approaches for osteochondral tissue engineering.
    01/2014; 5:2041731414541850. DOI:10.1177/2041731414541850
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cartilage research typically requires a broad range of experimental characterization techniques and thus various testing setups. Here, we describe how several of those tests can be performed with a single experimental platform, i.e. a commercial shear rheometer. Although primarily designed for shear experiments, such a rheometer can be equipped with different adapters to perform indentation and creep measurements, quantify alterations in the sample thickness, and conduct friction measurements in addition to shear rheology. Beyond combining four distinct experimental methods into one setup, the modified rheometer allows for performing material characterizations over a broad range of time scales, frequencies, and normal loads.
    Review of Scientific Instruments 09/2014; 85(9):093903-093903-9. DOI:10.1063/1.4894820 · 1.58 Impact Factor