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

Institution

AO Research Institute Davos, Switzerland. sibylle.grad@aofoundation.org

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