Objective: To use protein kinase C (PKC) δ-knockout mice to investigate the role of PKCδ in lesion development and to understand the underlying mechanism of the vascular disease.
Methods and results: PKCδ functions as a signal transducer mediating several essential functions of cell proliferation and apoptosis. However, the effect of PKCδ on neointimal formation in wire-injured vessels is unknown. Three weeks after wire injury of femoral arteries, neointimal lesions were significantly increased in PKCδ(-/-) mice compared with PKCδ(+/+) animals. Immunohistochemical staining revealed that total numbers of smooth muscle cells and macrophages in the lesions of PKCδ(-/-) mice were markedly elevated without changing the ratio of these 2 cell types. To further elucidate the mechanisms of PKCδ-mediated increase in the lesion, an in vivo endothelial migration model was established to evaluate endothelial wound healing after wire injury. Data showed that reendothelialization of the injured vessel was markedly delayed in PKCδ(-/-) mice; this coincided with more severe intimal hyperplasia. Migration of endothelial cells cultivated from cardiac tissue was markedly reduced in the absence of PKCδ, whereas no difference in proliferation or apoptosis was detected. Inhibition of PKCδ activity or protein expression by small hairpin RNA (shRNA) in cultured endothelial cells confirmed the defective migratory phenotype. Interestingly, vasohibin-1, an antiangiogenesis protein, was elevated in endothelial cells derived from PKCδ(-/-) mice, which was mainly because of delayed protein degradation mediated by PKCδ. Downregulation of vasohibin-1 restored the migration rate of PKCδ(-/-) endothelial cells to a similar level as PKCδ(+/+) cells.
Conclusions: PKCδ deficiency enhances neointimal formation, which is associated with delayed reendothelialization and involves increased cellular vasohibin-1 accumulation.