Cardiovascular Research Advance Access first published online on April 30, 2009
This version [Corrected Proof] published online on June 5, 2009
Cardiovascular Research, doi:10.1093/cvr/cvp135
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Rho kinase-1 mediates cardiac fibrosis by regulating fibroblast precursor cell differentiation
1 DeBakey Heart Center, Baylor College of Medicine and The Methodist Hospital, One Baylor Plaza F620, Houston TX 77030, USA
2 Department of Cardiac Surgery, University Clinical Center Bonn, Sigmund-Freud-Straße 25, 53105 Bonn, Germany
3 The Institute of Biosciences and Technology, The Texas A&M University System Health Science Center, Houston, TX 77030, USA
4 Riley Heart Research Center, Wells Center for Pediatric Research, Department of Pediatrics, Indian University School of Medicine, Indianapolis, IN 46202, USA
* Corresponding author. Tel: +1 713 798 3388; fax: +1 713 796 0015. E-mail address: shaudek{at}bcm.tmc.edu
Aims: Highly proliferative, CD34+/CD45+ fibroblasts derived from monocytic, blood-borne precursor cells play a critical role in the development of fibrosis in a murine ischaemic/reperfusion cardiomyopathy (I/RC) model. The differentiation of human monocytes into fibroblasts in vitro occurs after transendothelial migration (TEM) induced by monocyte chemoattractant protein 1 (MCP-1). Because Rho-associated kinase-1 (ROCK-1) has been implicated in fibrosis and leukocyte TEM, we investigated its involvement in I/RC.
Methods and results: We subjected mice with genetic deletion of ROCK-1 to I/RC. We found that ROCK-1–/– mice did not develop the fibrosis and cardiac dysfunction characteristic for I/RC: compared with wild-type, ROCK-1–/– hearts showed markedly lower numbers of I/RC-induced 
-smooth muscle actin+ fibroblasts and CD34+/CD45+ fibroblast precursors. Isolated cardiac fibroblasts from ROCK-1–/– mice undergoing I/RC were large and slowly proliferating, similar to fibroblasts isolated from sham-treated hearts. We also performed in vitro assays in which human peripheral blood mononuclear cells (PBMC) migrated through endothelial cells in response to MCP-1. Prior to migration, PBMC were incubated with ROCK-1-targeting small interfering RNA to silence ROCK-1 expression. We found that an 80% reduction of ROCK-1 protein did not inhibit TEM, but significantly reduced the amount of mononuclear cells that differentiated into fibroblasts by >20-fold.
Conclusion: Our data implicate an important role for ROCK-1 in the differentiation, but not in the TEM of monocytes that mature into cardiac fibroblasts. These cells mediate non-adaptive fibrosis.
KEYWORDS Cardiac fibroblasts; Monocytes; Rho-associated kinase-1; Endothelial transmigration; Fibrosis
Time for primary review: 29 days