title: Effects of the thermal environment on articular chondrocyte metabolism: a fundamental study to facilitate establishment of an effective thermotherapy for osteoarthritis.
abstract: OBJECTIVE
  To facilitate establishment of an effective thermotherapy for osteoarthritis (OA), we investigated the effects of the thermal environment on articular chondrocyte metabolism in vitro.
  
  
  METHODS
  Chondrocytes were isolated from porcine knee joints, and cultured at 32°C, 37°C and 41°C. Cell proliferation and viability were assessed at Days 2, 4 and 8. In addition, TdT-mediated dUTP nick end labeling (TUNEL) assay was performed at Day 3 to determine the proportion of apoptotic chondrocytes. Analysis of genes specific for factors related to the cartilage extracellular matrix (ECM), cartilage destruction, and cartilage protection was performed at Day 2. Furthermore, evaluation of heat stress tolerance, and heat shock protein 70 (HSP70) mRNA expression and protein synthesis was performed at Day 2 and 3, respectively.
  
  
  RESULTS
  Cell proliferation was more at 37°C than at 32°C and 41°C. Cell viability and the number of TUNEL-positive cells were not affected until Day 8 and 3, respectively. The expression of the ECM-related genes was up-regulated at higher temperature. The expression of MMP13, a type II collagen destructive enzyme, and that of TIMP1 and TIMP2, which are MMP inhibitors, were up-regulated at higher temperatures. Finally, the chondrocytes cultured at 41°C may acquire heat stress tolerance, in part, due to the up-regulation of HSP70, and may inhibit apoptosis induced by various stresses, which is observed in OA.
  
  
  CONCLUSIONS
  The thermal environment affects articular chondrocyte metabolism, and a heat stimulus of approximately 41°C could enhance chondrocyte anabolism and induce heat stress tolerance.
authors: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.|Research Fellow of Japan Society for the Promotion of Science, Tokyo 102-0083, Japan.
authors: Akira
authors: A
authors: Ito
authors: Department of Development and Rehabilitation of Motor Function, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors: Tomoki
authors: T
authors: Aoyama
authors: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors: Junichi
authors: J
authors: Tajino
authors: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors: Momoko
authors: M
authors: Nagai
authors: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors: Shoki
authors: S
authors: Yamaguchi
authors: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors: Hirotaka
authors: H
authors: Iijima
authors: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors: Xiangkai
authors: X
authors: Zhang
authors: Department of Orthopaedic Surgery, Graduate School of Medicine, Gifu University, Gifu 501-1194, Japan.
authors: Haruhiko
authors: H
authors: Akiyama
authors: Department of Motor Function Analysis, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors: Hiroshi
authors: H
authors: Kuroki
keywords: Thermal environment; articular chondrocyte metabolism; thermotherapy