Hypothermia Promotes Cell-Protective and Chondroprotective Effects After Blunt Cartilage Trauma

Background: Cryotherapy is routinely administered after sports injuries of synovial joints. Although positive clinical effects on periarticular swelling and pain have been described, the effects on the cell biological activities of cartilage and synovial cells remain largely unknown so far. Hypothesis: Local hypothermia alleviates synovial reactions and prevents chondrocyte death as well as cartilage destructive processes after blunt cartilage trauma. Study Design: Controlled laboratory study. Methods: Human cartilage explants were impacted by a drop-tower apparatus (0.59 J) and cultured at 24 hours or 7 days in different temperature conditions (2 hours [short term], 16 hours [medium term], or throughout [long term] at 27°C; afterwards or throughout at 37°C). Besides, isolated human fibroblast-like synoviocytes (FLS) were stimulated with traumatized cartilage conditioned medium and cultured as mentioned above up to 4 days. The effects of hypothermia were evaluated by cell viability, gene expression, type II collagen synthesis and cleavage, as well as the release of matrix metalloproteinase (MMP)–2, MMP-13, and interleukin 6 (IL-6). Results: Seven days after trauma, hypothermic treatment throughout improved cell viability (short term: 10.1% [ P = .016]; medium term: 6% [ P = .0362]; long term: 12.5% [ P = .0039]). Short-term hypothermia attenuated the expression of catabolic MMP-13 (mRNA: –2.2-fold [ P = .0119]; protein: –2-fold [ P = .0238]). Whereas type II collagen synthesis (1.7-fold [ P = .0227]) was increased after medium-term hypothermia, MMP-13 expression (mRNA: –30.8-fold [ P = .0025]; protein: –10.3-fold [ P < .0001]) and subsequent cleavage of type II collagen (–1.1-fold [ P = .0489]) were inhibited. Long-term hypothermia further suppressed MMP release (pro–MMP-2: –3-fold [ P = .0222]; active MMP-2: −5.2-fold [ P = .0183]; MMP-13: −56-fold [ P < .0001]) and type II collagen breakdown (–1.6-fold [ P = .0036]). Four days after FLS stimulation, hypothermia significantly suppressed the gene expression of matrix-destructive enzymes after medium-term (MMP-3: –4.1-fold [ P = .0211]) and long-term exposure (a disintegrin and metalloproteinase with thrombospondin motifs 4 [ADAMTS4]: –4.3-fold [ P = .0045]; MMP-3: –25.8-fold [ P = .014]; MMP-13: –122-fold [ P = .0444]) and attenuated IL-6 expression by trend. Conclusion: After blunt cartilage trauma, initial hypothermia for only 2 hours and/or 16 hours induced significant cell-protective and chondroprotective effects and promoted the anabolic activity of chondrocytes, while the expression of matrix-destructive enzymes by stimulated FLS was attenuated by prolonged hypothermia. Clinical Relevance: The findings of this preliminary ex vivo investigation indicate that optimized cryotherapy management after cartilage trauma might prevent matrix-degenerative processes associated with the pathogenesis of posttraumatic osteoarthritis.