Abstract 307: Deficiency of Lim-only Protein Fhl2 Accelerates Neointima Formation After Carotid Artery Ligation

Abstract

Rationale The LIM-only protein FHL2, also known as DRAL or SLIM3, has a regulatory function in many physiological processes and is expressed in the vessel wall in smooth muscle cells (SMCs) and endothelial cells, but not in macrophages. FHL2 regulates SMC phenotype, but its function in vascular injury is unknown. Objective To assess the role of FHL2 in SMC-rich lesion formation after vascular injury and to elucidate the underlying mechanism. Methods & Results Cultured aortic SMCs from FHL2-KO mice showed increased migration and increased proliferation through enhanced phosphorylation of extracellular-regulated kinase-1/2 (ERK1/2) and induction of CyclinD1 expression. In agreement with this, overexpression of FHL2 in SMCs reduced CyclinD1 expression. In addition, FHL2-KO SMCs showed enhanced expression of pro-inflammatory cytokines in a NFkB dependent manner. Consistent with these findings, NFkB activity is higher in FHL2-KO SMCs. In response to carotid artery ligation FHL2-deficient (FHL2-KO) mice developed accelerated lesion formation compared with wild-type (WT)-mice. Furthermore, FHL2-KO mice displayed high number of macrophages in lesions and enhanced expression of RANTES and stromal derived factor-1α (SDF-1α) in ligated carotid arteries. SDF-1α expression was also increased in plasma of FHL2-KO mice. Finally, FHL2-KO mice showed enhanced Ki67 expression in lesions compared with wild-type (WT)-mice. Conclusion FHL2 deficiency in mice results in an exacerbated neointima formation by enhanced proliferation and migration of SMCs, possibly regulated via ERK1/2 and NFkB pathway.