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Sliding motion modulates stiffness and friction coefficient at the surface of tissue engineered cartilage.

Abstract

OBJECTIVE
Functional cartilage tissue engineering aims to generate grafts with a functional surface, similar to that of authentic cartilage. Bioreactors that stimulate cell-scaffold constructs by simulating natural joint movements hold great potential to generate cartilage with adequate surface properties. In this study two methods based on atomic force microscopy (AFM) were applied to obtain information about the quality of engineered graft surfaces. For better understanding of the molecule-function relationships, AFM was complemented with immunohistochemistry.
METHODS
Bovine chondrocytes were seeded into polyurethane scaffolds and subjected to dynamic compression, applied by a ceramic ball, for 1h daily [loading group 1 (LG1)]. In loading group 2 (LG2), the ball additionally oscillated over the scaffold, generating sliding surface motion. After 3 weeks, the surfaces of the engineered constructs were analyzed by friction force and indentation-type AFM (IT-AFM). Results were complemented and compared to immunohistochemical analyses.
RESULTS
The loading type significantly influenced the mechanical and histological outcomes. Constructs of LG2 exhibited lowest friction coefficient and highest micro- and nanostiffness. Collagen type II and aggrecan staining were readily observed in all constructs and appeared to reach deeper areas in loaded (LG1, LG2) compared to unloaded scaffolds. Lubricin was specifically detected at the top surface of LG2.
CONCLUSIONS
This study proposes a quantitative AFM-based functional analysis at the micrometer- and nanometer scale to evaluate the quality of cartilage surfaces. Mechanical testing (load-bearing) combined with friction analysis (gliding) can provide important information. Notably, sliding-type biomechanical stimuli may favor (re-)generation and maintenance of functional articular surfaces and support the development of mechanically competent engineered cartilage.

Links

  • Publisher Full Text
  • Authors

    Grad S, Loparic M, Peter R, Stolz M, Aebi U, Alini M

    Source

    Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society 20:4 2012 Apr pg 288-95

    MeSH

    Aggrecans
    Animals
    Bioreactors
    Cartilage, Articular
    Cattle
    Chondrocytes
    Collagen Type II
    Elasticity
    Friction
    Glycoproteins
    Microscopy, Atomic Force
    Motion
    Stress, Mechanical
    Surface Properties
    Tissue Engineering
    Tissue Scaffolds
    Weight-Bearing

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    22285735