P1233M2 MACROPHAGES PROMOTE MOUSE AORTIC SMOOTH MUSCLE CELLS CALCIFICATION BY SGK1-TGFB1 AXIS

Abstract

Abstract Background and Aims Vascular calcification is an independent risk factor for all-cause mortality in patients with CKD. Macrophages play an important role in vascular calcification, which involve in the osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). Recent research shows SGK1 is a highly attractive candidate for developing VSMCs calcification. Previous studies indicated that TGFβ1 induces vascular calcification by regulating osteo-/chondrogenic transdifferentiation of VSMCs. This study focus on the effects of macrophages-derived SGK1 on VSMCs transdifferentiation via regulating TGFβ1 expression. Method Before induced into M2 phenotype with IL-4, RAW 264.7 cells were treated with SGK1 inhibitor EMD638683 for 24 hours to reduce SGK1 expression. The above cells were grouped as: M0, M2, M2+EMD to explore the expression of SGK1 and TGFβ1 by using western blot, qRT-PCR and immunofluorescence staining, respectively. The culture medium (CM) of the above group macrophages was collected. Then mouse aortic smooth muscle cells (MAoSMCs ) were cultured in these supernatants with normal medium or osteogenic medium (OM) with or without TGFβ1 receptor inhibitor SB-431542 for 3 weeks to explore the transdifferentiation and calcification of MOVAS by using western blot, RT-qPCR, immunofluorescence staining, calcium quantification, Alizarin Red and Von Kossa Staining. Results As Alizarin Red and Von Kossa Staining shown, MAoSMCs contained more calcium deposits in the M2-CM group compared with either in the group of NC nor M0-CM. Consistent with the above results, We also found that M2-CM promoted MAoSMCs transdifferentiation, which was characterized by markedly increase of expression of osteo-/chondrogenic markers (Runx2, ALPL, FGF23) and decrease of the MAoSMCs marker (SM22α). Exploring the mechanism of the above phenomenon we found the expression of SGK1 and TGFβ1 were significantly increased in M2 group compared with M0 group. Interestingly, both SGK1 inhibitor EMD638683 which reduced TGFβ1 expression in M2 and TGFβ1 receptor inhibitor SB-431542 could partially blocked MAoSMCs osteo-/chondrogenic transdifferentiation and calcification. Furthermore, recombinant mouse TGFβ1 Protein increased calcium content in MAoSMCs by using calcium quantification, Alizarin Red and Von Kossa Staining and promoted MAoSMCs osteo-/chondrogenic transdifferentiation, which was characterized by markedly increase of expression of osteo-/chondrogenic markers (Runx2, ALPL, FGF23) and decrease of the MAoSMCs marker (SM22α). Conclusion Our findings shed light M2 macrophages promotes MAoSMCs osteo-/chondrogenic transdifferentiation and calcification by up-regulating TGFβ1 expression.