Journal
CIRCULATION
Volume 141, Issue 25, Pages 2078-2094Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/CIRCULATIONAHA.119.040963
Keywords
cerebral hemorrhage; collagen type IV; myocytes; smooth muscle; Notch3 protein; mouse
Funding
- Fondation Leducq (Transatlantic Network of Excellence on the Pathogenesis of Small Vessel Disease of the Brain)
- European Union (Horizon 2020 Research and Innovation Program SVDs@target) [666881]
- French National Agency of Research (ANR I-Can)
- French Fondation for Rare Diseases
- National Institute of Neurological Disorders and Stroke
- National Institute of Aging [R01NS110656]
- National Institutes of Health [R35HL140027]
- Henry M. Jackson Foundation for the Advancement of Military Medicine [HU0001-18-2-0016]
- UK Medical Research Council
- Stroke Association
- Medical Research Council
- MRC [MR/R014140/1, MR/L016400/1] Funding Source: UKRI
- H2020 Societal Challenges Programme [666881] Funding Source: H2020 Societal Challenges Programme
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Background: Spontaneous deep intracerebral hemorrhage (ICH) is a devastating subtype of stroke without specific treatments. It has been thought that smooth muscle cell (SMC) degeneration at the site of arteriolar wall rupture may be sufficient to cause hemorrhage. However, deep ICHs are rare in some aggressive small vessel diseases that are characterized by significant arteriolar SMC degeneration. Here we hypothesized that a second cellular defect may be required for the occurrence of ICH. Methods: We studied a genetic model of spontaneous deep ICH usingCol4a1(+/G498V)andCol4a1(+/G1064D)mouse lines that are mutated for the alpha 1 chain of collagen type IV. We analyzed cerebroretinal microvessels, performed genetic rescue experiments, vascular reactivity analysis, and computational modeling. We examined postmortem brain tissues from patients with sporadic deep ICH. Results: We identified in the normal cerebroretinal vasculature a novel segment between arterioles and capillaries, herein called the transitional segment (TS), which is covered by mural cells distinct from SMCs and pericytes. InCol4a1mutant mice, this TS was hypermuscularized, with a hyperplasia of mural cells expressing more contractile proteins, whereas the upstream arteriole exhibited a loss of SMCs. TSs mechanistically showed a transient increase in proliferation of mural cells during postnatal maturation. Mutant brain microvessels, unlike mutant arteries, displayed a significant upregulation of SM genes andNotch3target genes, and genetic reduction ofNotch3inCol4a1(+/G498V)mice protected against ICH. Retina analysis showed that hypermuscularization of the TS was attenuated, but arteriolar SMC loss was unchanged inCol4a1(+/G498V),Notch3(+/-)mice. Moreover, hypermuscularization of the retinal TS increased its contractility and tone and raised the intravascular pressure in the upstream feeding arteriole. We similarly found hypermuscularization of the TS and focal arteriolar SMC loss in brain tissues from patients with sporadic deep ICH. Conclusions: Our results suggest that hypermuscularization of the TS, through increased Notch3 activity, is involved in the occurrence of ICH inCol4a1mutant mice, by raising the intravascular pressure in the upstream feeding arteriole and promoting its rupture at the site of SMC loss. Our human data indicate that these 2 mutually reinforcing vascular defects may represent a general mechanism of deep ICH.
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