ZiMT Journal Club July 2020: Dr. Anna-Maria Liphardt / Effects of Immobilization, Microgravity, and Physical Activity on the Human Body

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Dr. Anna-Maria Liphardt, Internal Medicine III, University Hospital Erlangen

Effects of Immobilization, Microgravity, and Physical Activity on the Human Body, specifically on Cartilage and Bone Tissue

Healthy articular cartilage is a prerequisite for proper joint function, and thus for unrestricted physical activity. In synovial joints, articular cartilage provides joint congruency, and distributes force between articulating surfaces, thus facilitating joint motion. In humans, investigating the effect of unloading on articular cartilage is difficult especially in healthy individuals, and space- flight related models provide a unique possibility to investigate this particular response. However, space flight is not only a good model for investigating the effects of immobilization on a healthy human body but the associated effects are highly relevant for crew health: to date space flight research has not tackled issues related to cartilage health. This may be due to the shorter crew times during the space shuttle missions and the fact, that cartilage degeneration is not visible and cannot be felt by the crew members. In recent years, imaging techniques and the availability of biochemical methods for analyzing serum biomarker concentrations have advanced. Previous work by our group [3, 4] and others suggests that immobilization can initiate cartilage degeneration leading to an increased health risk for human space flight and that current countermeasure regiments may not be capable of addressing cartilage health. In our most recent projects together with the German Sport University Cologne (Prof. Dr. A. Niehoff) the objective was to investigate the potential of different countermeasure regiments to affect cartilage biology [1, 2]. Countermeasure optimization is an important component of successful human space flight concerning crew health and while various exercise countermeasures are currently implemented on the International Space Station (ISS) the optimal training regimen has yet to be found. We could confirm that (beyond others) cartilage oligomeric matric protein (COMP) is a mechano-sensitive cartilage biomarker and affected by immobilization and mechanical loading. Simple interventions such as standing upright or a specific resistance training program during bed rest could not prevent these changes.

(1) Liphardt AM, Mündermann A, Heer M, Achtzehn S, Niehoff A, Mester J. J Orthop Res. (2020). Locomotion replacement exercise cannot counteract cartilage biomarker response to 5 days of immobilization in healthy adults. May 26. doi: 10.1002/jor.24753. Online ahead of print.

(2) Dreiner M, Willwacher S, Kramer A, Kümmel J, Frett T, Zaucke F, Liphardt AM, Gruber M, Niehoff A. (2020). Short-term Response of Serum Cartilage Oligomeric Matrix Protein to Different Types of Impact Loading Under Normal and Artificial Gravity. Front Physiol. Aug 31;11:1032. doi: 10.3389/fphys.2020.01032. eCollection 2020.

(3) Liphardt AM, Mündermann A, Andriacchi TP, Achtzehn S, Heer M, Mester J. (2018). Sensitivity of serum concentration of cartilage biomarkers to 21-days of bed rest. J Orthop Res. May;36(5):1465-1471. doi: 10.1002/jor.23786. Epub 2017 Nov 17.

(4) Liphardt AM, Mündermann A, Koo S, Bäcker N, Andriacchi TP, Zange J, Mester J, Heer M. (2009). Vibration training intervention to maintain cartilage thickness and serum concentrations of cartilage oligometric matrix protein (COMP) during immobilization. Osteoarthritis Cartilage, Dec;17(12):1598-603. doi: 10.1016/j.joca.2009.07.007. Epub 2009 Sep 1. PMID: 19747585