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Role of uppermost superficial surface layer of articular cartilage in the lubrication mechanism of joints

Published online by Cambridge University Press:  24 August 2001

P. KUMAR
Affiliation:
Department of Tissue Regeneration, Institute for Frontier Medical Sciences
M. OKA
Affiliation:
Department of Tissue Regeneration, Institute for Frontier Medical Sciences
J. TOGUCHIDA
Affiliation:
Department of Tissue Regeneration, Institute for Frontier Medical Sciences
M. KOBAYASHI
Affiliation:
Department of Tissue Regeneration, Institute for Frontier Medical Sciences
E. UCHIDA
Affiliation:
Department of Life Science, Kacho Junior College, Kyoto, Japan
T. NAKAMURA
Affiliation:
Department of Orthopaedic Surgery, School of Medicine, Kyoto University
K. TANAKA
Affiliation:
Department of Orthopaedic Surgery, School of Medicine, Kyoto University
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Abstract

The uppermost superficial surface layer of articular cartilage, the ‘lamina splendens’ which provides a very low friction lubrication surface in articular joints, was investigated using atomic force microscopy (AFM). Complementary specimens were also observed under SEM at −10 °C without dehydration or sputter ion coating. Fresh adult pig osteochondral specimens were prepared from the patellas of pig knee joints and digested with the enzymes, hyaluronidase, chondroitinase ABC and alkaline protease. Friction coefficients between a pyrex glass plate and the osteochondral specimens digested by enzymes as well as natural (undigested) specimens were measured, using a thrust collar apparatus. Normal saline, hyaluronic acid (HA) and a mixture of albumin, globulin, HA (AGH) were used as lubrication media. The surface irregularities usually observed in SEM studies were not apparent under AFM. The articular cartilage surface was resistant to hyaluronidase and also to chondroitinase ABC, but a fibrous structure was exhibited in alkaline protease enzymes-digested specimens. AFM analysis revealed that the thickness of the uppermost superficial surface layer of articular cartilage was between 800 nm and 2 μm in adult pig articular cartilage. The coefficient of friction (c.f.) was significantly higher in chondroitinase ABC and alkaline protease enzymes digested specimens. Generally, in normal saline lubrication medium, c.f. was higher in comparison to HA and AGH lubrication media. The role of the uppermost, superficial surface layer of articular cartilage in the lubrication mechanism of joints is discussed.

Type
Paper
Copyright
© Anatomical Society of Great Britain and Ireland 2001

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