Abstract
Mechanical stretching of connective tissue occurs with normal movement and postural changes, as well as treatments including physical therapy, massage and acupuncture. Connective tissue fibroblasts were recently shown to respond actively to short-term mechanical stretch (minutes to hours) with reversible cytoskeletal remodeling, characterized by extensive cell spreading and lamellipodia formation. In this study, we have examined the effect of tissue stretch on the distribution of α- and β-actin in subcutaneous tissue fibroblasts ex vivo. Normal fibroblasts uniformly exhibited α-smooth muscle actin (α-SMA) immunoreactivity. Unlike cultured fibroblasts and smooth muscle cells, α-SMA in these fibroblasts was not in F-actin form (indicated by lack of phalloidin co-localization) nor was it organized into distinct stress fibers. The lack of stress fibers and fibronexus was confirmed by electron microscopy, indicating that these cells were not myofibroblasts. In unstretched tissue, the pattern of α-actin was diffuse and granular. With tissue stretch (30 min), α-actin formed a star-shaped pattern centered on the nucleus, while β-actin extended throughout the cytoplasm including lamellipodia and cell cortex. This dual response pattern of α- and β-actin may be an important component of cellular mechanotransduction mechanisms relevant to physiologic and therapeutic mechanical forces applied to connective tissue.
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Acknowledgements
The authors thank Dr. Christine Chaponnier for the generous gift of antibodies and α-SMA peptide, as well as many helpful discussions, Drs. David Schneider and Robert Kelm for the kind gift of SMCs, Nicole Bishop and Heidi Taatjes for technical assistance, as well as Nicole A. Bouffard for help with manuscript preparation. We also thank Drs. Guido Majno, Isabelle Joris and Robert Kelm for their insight and advice. This work was funded in part by the NIH Center for Complementary and Alternative Medicine Research Grant RO1-AT01121 and by NIH Grant P20 RR16435 from the COBRE Program of the National Center for Research Resources. Its content is solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health.
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Langevin, H.M., Storch, K.N., Cipolla, M.J. et al. Fibroblast spreading induced by connective tissue stretch involves intracellular redistribution of α- and β-actin. Histochem Cell Biol 125, 487–495 (2006). https://doi.org/10.1007/s00418-005-0138-1
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DOI: https://doi.org/10.1007/s00418-005-0138-1