title: Uniaxial repetitive mechanical overloading induces influx of extracellular calcium and cytoskeleton disruption in human tenocytes.
abstract: Tendon calcification is common in the Achilles tendon, and injuries affect not only athletes, but also the general population. However, the underlying cellular mechanisms are not yet fully understood. In this study, we isolated healthy human tenocytes and subjected them to uniaxial mechanical stretching (at 1.0 Hz) for various stretch times (4 h, 8 h, 12 h) or magnitudes (0%, 4%, 8%, 12%). The extracellular calcium chelator EGTA, calcium channel inhibitor MnCl2, nifedipine, or various doses of exogenous calcium were administered to these cells with or without mechanical overloading. The intracellular calcium concentration was determined by using a Fluo-3/AM fluorescence probe, and the cytoskeleton was revealed by F-actin Phalloidin staining. The intracellular calcium concentration increased in a magnitude- and time-dependent manner following stretching. These increases were suppressed by EGTA, MnCl2, or nifedipine. Additionally, cytoskeleton F-actin was disrupted significantly by stretching in a time-dependent manner. When extracellular calcium was applied, the intracellular calcium concentration increased, and F-actin was disrupted dramatically under mechanical stretching compared with non-stretched cells. Thus, repetitive mechanical overloading induces the accumulation of abnormally high concentrations of intracellular calcium resulting from extracellular calcium influx mediated, at least in part, by membrane calcium channels and finally causes cytoskeleton disorganization and tenocyte dysfunction. These findings provide novel experimental evidence for the pathology of tendon calcification and indicate that the blockade of calcium influx is a potential target for the prevention and treatment of calcific tendinopathy.
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, People's Republic of China.
authors.forename: Wan
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, People's Republic of China.|Department of Orthopaedics, Lanzhou General Hospital, Lanzhou, 730050, People's Republic of China.
authors.forename: Yinshuan
authors.initials: Y
authors.lastname: Deng
authors.affiliation: Department of Neurobiology, Chongqing Key Laboratory of Neurobiology, Third Military Medical University, Chongqing, 400038, People's Republic of China. zhangjqtmmu@yahoo.com.
authors.forename: Jiqiang
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, People's Republic of China. tangkanglai@sina.com.
authors.forename: Kanglai
authors.initials: K
authors.lastname: Tang
mesh_terms: D000125:Achilles Tendon / Q000166:cytology*; D000199:Actins / Q000378:metabolism; D000328:Adult; D000704:Analysis of Variance; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D005453:Fluorescence; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D008297:Male; D013314:Stress, Mechanical; D015854:Up-Regulation / Q000187:drug effects; D016474:Weight-Bearing; D055815:Young Adult
chemical_list: D000199:Actins; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002614:Chelating Agents; D002118:Calcium