Intercellular adhesion molecule‐1 is expressed by skeletal muscle cells in hypertrophying muscle of mice

Abstract

Our laboratory recently demonstrated that β2 integrins contribute to overload‐induced skeletal muscle hypertrophy. One potential mechanism by which β2 integrin expressing leukocytes influence the hypertrophic response of skeletal muscle involves intercellular adhesion molecule‐1 (ICAM‐1), the major ligand for β2 integrins. The objective of our current work is to examine ICAM‐1 expression and localization to skeletal muscle cells in hypertrophying muscle and to determine if β2 integrins influence ICAM‐1 expression and/or its localization.Plantaris muscles of wild type and β2 integrin deficient mice were exposed to 3, 7, or 14 days of mechanical overload via synergist ablation. Real‐time PCR and western blotting analysis revealed that ICAM‐1 gene and protein expression was significantly elevated in overloaded muscle. Experiments using flow cytometry and multi‐photon laser scanning confocal microscopy revealed that ICAM‐1 was expressed by mononuclear cells (satellite cells/myoblasts and leukocytes) as well as mature muscle fibers following mechanical loading.We speculate that expression of ICAM‐1 by skeletal muscle cells after mechanical loading serves as a mechanism by which neutrophils and macrophages can bind to and directly communicate with skeletal muscle cells to promote hypertrophy.This work was partially supported by The University of Toledo Interdisciplinary Grant Program.