Contraction of myofibroblasts in granulation tissue is dependent on Rho/Rho kinase/myosin light chain phosphatase activity

• Published in: Wound repair and regeneration Vol. 14; no. 3; pp. 313 - 320
• Main Authors: Tomasek, James J., Vaughan, Melville B., Kropp, Bradley P., Gabbiani, Giulio, Martin, Michael D., Haaksma, Carol J., Hinz, Boris
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.05.2006
• Subjects: Amides - pharmacology; Animals; Endothelin-1 - pharmacology; Enzyme Inhibitors - pharmacology; Fibroblasts - enzymology; Fibroblasts - physiology; Granulation Tissue - enzymology; Granulation Tissue - pathology; Granulation Tissue - physiopathology; Intracellular Signaling Peptides and Proteins - antagonists & inhibitors; Intracellular Signaling Peptides and Proteins - metabolism; Isometric Contraction - drug effects; Male; Muscle, Smooth - cytology; Myosin-Light-Chain Phosphatase - antagonists & inhibitors; Myosin-Light-Chain Phosphatase - metabolism; Protein Kinase Inhibitors - pharmacology; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - metabolism; Pyridines - pharmacology; Rats; Rats, Sprague-Dawley; rho-Associated Kinases; Signal Transduction; Wound Healing - physiology
• ISSN: 1067-1927; 1524-475X
• DOI: 10.1111/j.1743-6109.2006.00126.x

ABSTRACT During wound healing and fibrocontractive diseases fibroblasts acquire a smooth muscle cell‐like phenotype by differentiating into contractile force generating myofibroblasts. We examined whether regulation of myofibroblast contraction in granulation tissue is dominated by Ca2+‐induced phosphorylation of myosin light chain kinase or by Rho/Rho kinase (ROCK)‐mediated inhibition of myosin light chain phosphatase, similar to that of cultured myofibroblasts. Strips of granulation tissue obtained from rat granuloma pouches were stimulated with endothelin‐1 (ET‐1), serotonin, and angiotensin‐II and isometric force generation was measured. We here investigated ET‐1 in depth, because it was the only agonist that produced a long‐lasting and strong response. The ROCK inhibitor Y27632 completely inhibited ET‐1–promoted contraction and the phosphatase inhibitor calyculin elicited contraction in the absence of any other agonists, suggesting that activation of the Rho/ROCK/myosn light chain phosphatase pathway is critical in regulating in vivo myofibroblast contraction. Membrane depolarization with K+ also stimulated a long‐lasting contraction of granulation tissue; however, the amount of force generated was significantly less compared to ET‐1. Moreover, K+‐induced contraction was inhibited by Y27632. These results are consistent with inhibition of myosin light chain phosphatase by the Rho/ROCK signaling pathway, which would account for the long‐duration contraction of myofibroblasts necessary for wound closure.