Vitamin D deficiency promotes intracranial aneurysm rupture

Abstract

Intracranial aneurysm rupture causes severe disability and high mortality. Epidemiological studies show a strong association between decreased vitamin D levels and an increase in aneurysm rupture. However, the causality and mechanism remain largely unknown. In this study, we tested whether vitamin D deficiency promotes aneurysm rupture and examined the underlying mechanism for the protective role of vitamin D against the development of aneurysm rupture utilizing a mouse model of intracranial aneurysm. Mice consuming a vitamin D-deficient diet had a higher rupture rate than mice with a regular diet. Vitamin D deficiency increased proinflammatory cytokines in the cerebral arteries. Concurrently, vitamin D receptor knockout mice had a higher rupture rate than the corresponding wild-type littermates. The vitamin D receptors on endothelial and vascular smooth muscle cells, but not on hematopoietic cells, mediated the effect of aneurysm rupture. Our results establish that vitamin D protects against the development of aneurysmal rupture through the vitamin D receptors on vascular endothelial and smooth muscle cells. Vitamin D supplementation may be a viable pharmacologic therapy for preventing aneurysm rupture.

Keywords: Intracranial aneurysm; mice; stroke; subarachnoid hemorrhage; vitamin D.

Figure 1.

Dietary vitamin D deficiency promotes aneurysmal rupture in a mouse model of intracranial aneurysm. (a and b) There was a significantly increased rupture rate in the vitamin D-deficient group compared to the control diet group. There was no difference in the incidence of aneurysms between the control diet and vitamin D deficient diet groups. (c) Symptom-free survival rate was lower in the vitamin D-deficient group. (d and e) Vitamin D deficient diet effectively decreased 25-hydroxy vitamin D in the serum but did not affect serum Ca²⁺ in the serum (n = 15 for both, P > 0.05) and (f) No difference in blood pressure between the two diet groups. ∗P < 0.05.

Figure 2.

Effect of dietary vitamin D deficiency on inflammation. Compared to the control diet group, in vitamin D-deficient mice, IL-1β, TNF-α, NF-κB, MMP-9, and MCP-1 in cerebral arteries were significantly higher, while TIMP-1 and TIMP-2 were significantly lower. VDR was also significantly higher. ∗P < 0.05. There was no difference between the two groups in mRNA levels of RXR-α, VEGF, TGF-β, and iNOS.

Figure 3.

Endothelial cell-specific knockout of vitamin D receptors increases the rupture rate of aneurysms. (a) No difference in the incidence of aneurysms between endothelial cell-specific vitamin D receptor knockout mice (VDR^f/fTie2-Cre⁺) and control mice (VDR^f/f). (b) Significantly increased rupture rate in VDR^f/fTie2-Cre⁺ mice. (c) Significantly lower symptom-free survival rate in VDR^f/fTie2-Cre⁺ mice and (d) No difference in blood pressure between the knockout group and control littermates. Fisher’s exact test was used to analyze the rupture rate of aneurysms. Log-rank (Mantel-Cox) test was used for the analysis of the survival rate. ∗P < 0.05.

Figure 4.

Smooth muscle cell-specific knockout of vitamin D receptors increases the rupture rate of aneurysms. (a) No difference in the incidence of aneurysms between smooth muscle cell-specific vitamin D receptor knockout mice (VDR^f/fSM22-Cre⁺) and control mice (VDR^f/f). (b) Significantly increased rupture rate in VDR^f/fSM22-Cre⁺ mice. (c) Significantly lower symptom-free survival rate in VDR^f/fSM22-Cre⁺ mice and (d) No difference in blood pressure between the knockout group and control littermates. Fisher’s exact test was used to analyze the rupture rate of aneurysms. Log-rank (Mantel-Cox) test was used for the analysis of the survival rate. ∗P < 0.05.

Figure 5.

Myeloid lineage cell-specific knockout of vitamin D receptors has no effect on the rupture rate of aneurysms. There was no difference in incidence rate (a), rupture rate of aneurysms (b), symptom-free survival rate (c) or blood pressures (d) between myeloid lineage cell-specific vitamin D receptor knockout mice (VDR^f/fLysM-Cre⁺) and control mice (VDR^f/f). Fisher’s exact test was used to analyze the rupture rate of aneurysms. Log-rank (Mantel-Cox) test was used for the analysis of the survival rate.