Abstract: Apoptosis and p53 Expression in Chondrocytes Relate to Degeneration in Articular Cartilage of Immobilized Knee Joints

Apoptosis and p53 Expression in Chondrocytes Relate to Degeneration in Articular Cartilage of Immobilized Knee Joints

RYUJI OKAZAKI, AKINORI SAKAI, AKIRA OOTSUYAMA, TAKESHI SAKATA, TOSHITAKA NAKAMURA, and TOSHIYUKI NORIMURA

ABSTRACT.

Objective. We have reported that articular cartilage showed early stage degeneration at 7 and 14 days after immobilization, moderate degeneration at 28 days, and severe degeneration at 42 days in rabbits. To test whether apoptosis occurs in association with p53 expression in chondrocytes during the process of articular cartilage degeneration, we investigated the degree of cartilage degeneration, the frequency of apoptotic cells, and the levels of p53 mRNA in rabbits and mice after knee immobilization.

Methods. Right knees of male Japanese white rabbits were immobilized in full extension with fiberglass casts for up to 42 days. Similarly, right knees of male p53 wild-type [p53 (+/+)] and p53 null [p53 (-/-)] mice were immobilized in full extension with bandage tape for up to 84 days. Apoptotic cells were confirmed by TUNEL staining on the sections of knee joints. Total RNA of articular chondrocytes obtained from Day 0 or immobilized knees was analyzed semiquantitatively by RT-PCR using specific primers for p53.

Results. Articular cartilage degenerated after immobilization of p53 (+/+) mouse knees, but not after immobilization of p53 (-/-) knees. Apoptotic cells were observed in articular cartilage in the femur and tibia of rabbits and p53 (+/+) mice after immobilization. However, only a few apoptotic cells were observed at the same sites in p53 (-/-) mice. In RT-PCR analysis, the levels of p53 mRNA obtained from immobilized groups were significantly higher than those of Day 0 groups in rabbit and p53 (+/+) mouse knees.

Conclusion. Apoptosis and p53 expression in chondrocytes relate to degeneration in articular cartilage of immobilized knee joints. (J Rheumatol 2003;30:559-66)

Key Indexing Terms:

ARTICULAR CARTILAGE
IMMOBILIZATION
DEGENERATION
APOPTOSIS
p53

From the Department of Radiation Biology and Health, University of Occupational and Environmental Health, Kitakyushu, Japan.

Supported in part by a Grant-in-Aid from the Encouragement of Young Scientists of Japan Society for the Promotion of Science (No. 11770824); the Japan Ministry of Health and Welfare (Comprehensive Research on Aging and Health to T. Nakamura and the Research Grant for Longevity Sciences to T. Nakamura); and the Japan Ministry of Education, Science, Sports, and Culture (Scientific Research B No. 11470315 to A. Sakai, Scientific Research B No. 12470313 to T. Nakamura and Scientific Research on Priority Areas B No. 12137210 to T. Nakamura)

R. Okazaki, MD, PhD, Research Associate; A. Ootsuyama, DVM, PhD, Associate Professor; T. Norimura, PhD, Professor, Department of Radiation Biology and Health; A. Sakai, MD, PhD, Associate Professor; T. Sakata, MD, PhD, Postdoctoral Fellow; T. Nakamura, MD, PhD, Professor, Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health.

Address reprint requests to Dr. A. Sakai, Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka Yahatanishi-ku, Kitakyushu, 807-8555 Japan. E-mail: a-sakai@med.uoeh-u.ac.jp

Submitted November 21, 2001; revision accepted August 26, 2002.