Cardiovascular Research Advance Access [Accepted Manuscript] published online on April 30, 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, TX77030, 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: Sandra B. Haudek, phone: (713) 798-3388 fax: (713) 796-0015 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 ischemic/ reperfusion cardiomyopathy model (I/RC). 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 to 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 (siRNA) 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 transendothelial migration 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