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Lack of MK2 inhibits myofibroblast formation and exacerbates pulmonary fibrosis.

Authors :
Liu T
Warburton RR
Guevara OE
Hill NS
Fanburg BL
Gaestel M
Kayyali US
Source :
American journal of respiratory cell and molecular biology [Am J Respir Cell Mol Biol] 2007 Nov; Vol. 37 (5), pp. 507-17. Date of Electronic Publication: 2007 Jun 28.
Publication Year :
2007

Abstract

Fibroblasts play a major role in tissue repair and remodeling. Their differentiation into myofibroblasts, marked by increased expression of smooth muscle-specific alpha-actin (alpha-SMA), is believed to be important in wound healing and fibrosis. We have recently described a role for MK2 in this phenotypic differentiation in culture. In this article, we demonstrate that MK2 also regulates myofibroblasts in vivo. Disruption of MK2 in mice prevented myofibroblast formation in a model of pulmonary fibrosis. However, MK2 disruption and consequent lack of myofibroblast formation exacerbated fibrosis rather than ameliorated it as previously postulated. When mice lacking MK2 (MK2-/-) were exposed to bleomycin, more collagen accumulated and more fibroblasts populated fibrotic regions in their lungs than in similarly treated wild-type mice. While there were many vimentin-positive cells in the bleomycin-treated MK2-/- mouse lungs, few alpha-SMA-positive cells were observed in these lungs compared with wild-type mouse lungs. siRNA against MK2 reduced alpha-SMA expression in wild-type mouse embryonic fibroblasts (MEF), consistent with its suppression in MK2-/- MEF. On the other hand expressing constitutively active MK2 in MK2-/- MEF significantly increased alpha-SMA expression. MK2-/-MEF proliferated at a faster rate and produced more collagen; however, they migrated at a slower rate than wild-type MEF. Overexpressing phosphomimicking HSP27, a target of MK2, did not reverse the effect of MK2 disruption on fibroblast migration. MK2 disruption did not affect Smad2 activation by transforming growth factor-beta. Thus, MK2 appears to mediate myofibroblast differentiation, and inhibiting that differentiation might contribute to fibrosis rather than protect against it.

Details

Language :
English
ISSN :
1535-4989
Volume :
37
Issue :
5
Database :
MEDLINE
Journal :
American journal of respiratory cell and molecular biology
Publication Type :
Academic Journal
Accession number :
17600313
Full Text :
https://doi.org/10.1165/rcmb.2007-0077OC