Change of lymphatic vessel density by induced muscle atrophy

Introduction: The functions of lymphatic system include homeostasis, drain of skeletal muscles and return of proteins and other macromolecules from interstitial tissue to the blood vessel system. A disability of the lymphatic efflux can induce grave consequences e.g. an increased loss of proteins. The trial “Exercise-Induced Decline in the Density of LYVE-1-Positive Lymphatic Vessels in Human Skeletal Muscle” from the Institute of Cardiology and Sports medicine, German Sport University Cologne ”(…) investigated, if alterations in lymphatic density can be observed in human skeletal muscle as a response to endurance exercise (…) ” It becomes apparent that the density of lymphatic capillaries within the extracted biopsy of M. vastus lat. decreased significantly after a cycling training intervention. (Gehlert et al. 2009). After it is asserted that raised endurance training leads to decreased density of lymphatic capillaries in human skeletal muscle, a change is also expected in an atrophied skeletal muscle. We hypothesize an increased density of lymphatic capillaries in human skeletal muscle and use biopsies of M. soleus to investigate the effects. Methods: The extracted biopsies are results of the “NutriHep”-Trial which shows an induced muscular atrophy after load reduction within wearing “Hepahoios Orthese” for sixty days. (Schopen et al. 2016) It is expected that the atrophied muscle contains an increased density of lymphatic capillaries. 7 subjects were treated by Lupin-substitution and daily electrostimulations. The control group used Hepaistos Orthesis without any treatments. Biopsies were extracted pre and post induced atrophy. Lymphatic capillaries were stained by immunohistochemistry using Anti-LYVE-1 and Podoplanin antibodies for lymph specific staining and AntiCaveolin-1 for detecting endothelial cells of lymphatic and blood vessels. Results: For quantitative analysis of the fraction of lymphatic vessels in the total area of the muscle biopsies and the ratio of lymphatic to blood vessels we used ImageJ. Our preliminary results of NutriHep show the following percentages: lymphatic vessels in non-atrophic muscle 0,24+/-0,038%, in atrophic muscle 0,35+/- 0,114%. For the ratio of lymphatic to blood vessels we found 3,6+/-1,612% in non- atrophic muscle, while in atrophy it was 5,59+/-1,84% Conclusions: We could demonstrate that muscle atrophy increases the total fraction as well as the ratio in respect to blood vessels of lymphatic vessels in muscle biopsies. However not all data were taken into account and further analyzes are required. Especially the Lupin- and electrostimulating treatments may have significant influence on these preliminary result