Rho kinase-1 mediates cardiac fibrosis by regulating fibroblast precursor cell differentiation.
OBJECTIVE
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.


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 alpha-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.


CONCLUSIONS
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.
Haudek
Sandra B
SB
DeBakey Heart Center, Baylor College of Medicine and The Methodist Hospital, One Baylor Plaza F620, Houston TX 77030, USA. shaudek@bcm.tmc.edu
Gupta
Damon
D
Dewald
Oliver
O
Schwartz
Robert J
RJ
Wei
Lei
L
Trial
JoAnn
J
Entman
Mark L
ML
D000818:Animals; D009202:Cardiomyopathies / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D054338:Cell Transdifferentiation; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D004195:Disease Models, Animal; D005347:Fibroblasts / Q000201:enzymology* / Q000473:pathology; D005355:Fibrosis; D006801:Humans; D036904:Leukocyte Rolling; D007963:Leukocytes, Mononuclear / Q000201:enzymology* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D015428:Myocardial Reperfusion Injury / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D034622:RNA Interference; D015398:Signal Transduction; D014162:Transfection; D054460:rho-Associated Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D018932:Chemokine CCL2; C515851:ROCK1 protein, human; C515852:ROCK2 protein, human; C515854:Rock1 protein, mouse; D054460:rho-Associated Kinases