CD163+ macrophages restrain vascular calcification, promoting the development of high-risk plaque.

Abstract

Vascular calcification (VC) is concomitant with atherosclerosis, yet it remains uncertain why rupture-prone high-risk plaques do not typically show extensive calcification. Intraplaque hemorrhage (IPH) deposits erythrocyte-derived cholesterol enlarging the necrotic core and promoting the high-risk plaque development. Pro-atherogenic CD163+ alternative macrophages engulf hemoglobin-haptoglobin (HH) complexes at IPH sites. However, their role in VC has never been examined. Here we show, in human arteries, the distribution of CD163+ macrophages correlates inversely with VC. In vitro experiments using vascular smooth muscle cells (VSMC) cultured with HH-exposed human macrophages supernatant (M(Hb)) reduced calcification, while arteries from ApoE-/-CD163-/- mice showed greater VC. M(Hb) supernatant-exposed VSMC showed activated NFκB, while blocking NFκB attenuated the anti-calcific effect of M(Hb) on VSMCs. CD163+ macrophages altered VC through NFκB-induced transcription of hyaluronan synthase (HAS), an enzyme which catalyzes the formation of the extracellular matrix glycosaminoglycan, hyaluronan, within VSMCs. M(Hb) supernatants enhanced HAS production in VSMC, while knocking-down HAS attenuated its anti-calcific effect. NFκB blockade in ApoE-/- mice reduced hyaluronan and increased VC. In human arteries, hyaluronan/HAS were increased in areas of CD163+ macrophage presence. Our findings highlight an important mechanism by which CD163+ macrophages inhibit VC through NFκB-induced HAS augmentation and thus promote the high-risk plaques development.