Smooth Muscle Proliferation in Moyamoya Vasculopathy
Smooth Muscle Proliferation in Moyamoya Vasculopathy
Smooth Muscle Proliferation in Moyamoya Vasculopathy
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<strong>Smooth</strong> <strong>Muscle</strong> <strong>Proliferation</strong> <strong>in</strong><br />
<strong>Moyamoya</strong> <strong>Vasculopathy</strong><br />
Dianna M. Milewicz, MD PhD<br />
University of Texas Health Science<br />
Center at Houston
<strong>Moyamoya</strong> Disease<br />
• Ischemic strokes due to stenosis of the <strong>in</strong>tracranial <strong>in</strong>ternal<br />
carotid arteries and their proximal branches associated with<br />
the formation of collaterals<br />
• Increased <strong>in</strong> prevalence <strong>in</strong> Japan<br />
– RNF213 mutations<br />
• Familial <strong>in</strong> 8% of patients<br />
genetic predisposition<br />
• MMD and genetic syndromes:<br />
– Neurofibromatosis<br />
– Noonan syndrome<br />
– Sickle cell anemia<br />
genetic heterogeneity
Cerebrovascular Pathology Associated<br />
with <strong>Moyamoya</strong> Disease<br />
Occlusion of the artery<br />
Neo<strong>in</strong>timal lesions with<br />
smooth muscle cells<br />
No lipid deposition or<br />
<strong>in</strong>flammation<br />
Do genetic mutations that <strong>in</strong>crease SMC<br />
proliferation play a role <strong>in</strong> the pathogenesis of<br />
<strong>Moyamoya</strong> disease?
ACTA2 Missense Mutations Cause Familial<br />
Thoracic Aortic Aneurysms and Dissections<br />
ACTA2 R149C missense mutation<br />
Penetrance of TAAD: 50%
Aortic <strong>Smooth</strong> <strong>Muscle</strong> Cells and<br />
Aortic Media<br />
the Contractile Unit<br />
Act<strong>in</strong><br />
Contractile Unit<br />
Myos<strong>in</strong>
ACTA2 Missense Mutations <strong>in</strong> FTAAD<br />
G48V<br />
P72Q<br />
N117T R149C<br />
Forty ACTA2 missense mutations<br />
No polymorphic variants <strong>in</strong> controls<br />
All mutations mutant prote<strong>in</strong><br />
R179H<br />
1 2 3 4 5 6 7 8 9<br />
R39C R39H R118Q Y135H G160D R212Q<br />
L69Q<br />
W88R<br />
V154A<br />
R258H R258C<br />
G270R<br />
R292G<br />
T353N
ACTA2 Mutations Cause Livedo Reticularis:<br />
Sk<strong>in</strong> Rash Due to Arterial Occlusion<br />
Penetrance of livedo reticularis is 100%
Aortic Arterial Pathology <strong>in</strong> Patients<br />
with ACTA2 Mutations<br />
Control ACTA2 R149C ACTA2 R149C ACTA2 T353N<br />
ACTA2 Sta<strong>in</strong><strong>in</strong>g<br />
100X
ACTA2 Mutations Lead to Early Onset<br />
Coronary Artery Disease<br />
TAAD<br />
Premature CAD<br />
Premature stroke
<strong>Moyamoya</strong> Disease and<br />
Early Onset Strokes <strong>in</strong><br />
ACTA2 Mutation Carriers<br />
TAAD<br />
Premature CAD<br />
Premature stroke
De Novo ACTA2 R179H Mutations<br />
<strong>Smooth</strong> <strong>Muscle</strong> Dysfunction Syndrome<br />
• 15 patients with de novo ACTA2 R179H<br />
• Fully penetrant vascular diseases at young ages:<br />
– Ascend<strong>in</strong>g aortic aneurysms<br />
– <strong>Moyamoya</strong> disease<br />
– PDA<br />
• Loss of SMC function <strong>in</strong> other organs:<br />
– Fixed dilated pupils<br />
– Hypotonic bladder<br />
– Hypoperistalsis with malrotation<br />
– Patent ductus arteriosus<br />
• Proliferative SMC phenotypes:<br />
– Aortic coarctation<br />
– Primary pulmonary hypertension
Loss of function:<br />
Decreased SMC<br />
contraction<br />
Large arteries:<br />
-high elast<strong>in</strong> content<br />
- Exposed to high<br />
pressures<br />
Aortic<br />
Aneurysms<br />
ACTA2 <strong>Vasculopathy</strong><br />
Ga<strong>in</strong> of function:<br />
Increased SMC<br />
proliferation<br />
Small arteries:<br />
-low elast<strong>in</strong> content<br />
-exposed to low<br />
pressures<br />
Vascular occlusive diseases<br />
(CAD, stroke)
Characterization of Mouse Model:<br />
Acta2 -/- Mice<br />
Fold change (a.u.)<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
Acta2 expression<br />
Wt<br />
Acta2 mRNA<br />
α-act<strong>in</strong><br />
GAPDH<br />
Acta2 -/-<br />
Previously characterized by Schildmeyer et al<br />
(2000):<br />
Contractility of arteries<br />
Blood pressure<br />
Schildmeyer LA et al (2000). FASEB J.
Acta2 -/- SMCs Proliferate and Migrate<br />
Faster than Wild-type SMCs<br />
<strong>Proliferation</strong> – ascend<strong>in</strong>g SMCs <strong>Proliferation</strong> – descend<strong>in</strong>g SMCs<br />
BrdU <strong>in</strong>corporation (OD)<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
p
Acta2 -/- Mice: Increased<br />
Neo<strong>in</strong>timal <strong>Proliferation</strong> with Vascular Injury<br />
ligation site<br />
Neo<strong>in</strong>tima Area (µm 2 )<br />
40000<br />
30000<br />
20000<br />
10000<br />
0<br />
Injury<br />
wildtype Acta2-/-<br />
p < 0.01<br />
p < 0.01<br />
- + - +<br />
WT Acta2-/-<br />
% Stenosis<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
Injury<br />
p < 0.01<br />
+ +<br />
WT Acta2-/-
BrdU <strong>in</strong>corporation (OD)<br />
Anti-cancer Drug Decreases <strong>Proliferation</strong><br />
<strong>in</strong> vitro and Neo<strong>in</strong>timal Formation <strong>in</strong> vivo<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
p
Loss of function:<br />
Decreased SMC<br />
contraction<br />
Large arteries:<br />
-high elast<strong>in</strong> content<br />
- Exposed to high<br />
pressures<br />
Aortic<br />
Aneurysms<br />
ACTA2 <strong>Vasculopathy</strong><br />
Ga<strong>in</strong> of function:<br />
Increased SMC<br />
proliferation<br />
Small arteries:<br />
-low elast<strong>in</strong> content<br />
-exposed to low<br />
pressures<br />
Vascular occlusive diseases<br />
(CAD, stroke)
<strong>Vasculopathy</strong> Associated with Neurofibromatosis<br />
• Affects aorta to small arterioles<br />
• Can cause aneurysms and occlusive diseases, <strong>in</strong>clud<strong>in</strong>g<br />
<strong>Moyamoya</strong> disease<br />
• Mouse studies show <strong>in</strong>creased SMC proliferation and<br />
migration and <strong>in</strong>crease neo<strong>in</strong>timal formation<br />
• NF1 mutations
<strong>Moyamoya</strong> disease and RNF213 Mutations<br />
• Identified through l<strong>in</strong>kage analysis and<br />
association studies as a gene that causes<br />
MMD <strong>in</strong> Japan.<br />
• “Founder” mutation <strong>in</strong> Japan (Asia?).<br />
• Function of the gene is unknown.<br />
• 10 – 15% of MMD patients <strong>in</strong> our U.S. cohort<br />
have RNF213 mutations (unpublished data).
Conclusions<br />
• A subset of ACTA2 mutations predispose to MMD.<br />
• Acta2 deficient mouse models suggest that<br />
occlusive disease is driven by SMC hyperplasia.<br />
– Why do some mutations cause more SMC hyperplasia?<br />
• Anti-cancer drug may prevent or limit MMD lesions<br />
<strong>in</strong> patients with ACTA2 mutations.<br />
– Can anti-proliferative drugs used to treat MMD?<br />
• NF1 mouse model also suggests that occlusive<br />
disease is due to SMC hyperplasia.<br />
• RNF213 is a major gene for MMD.<br />
– Do RNF213 mutations cause SMC hyperplasia?
Milewicz Lab members<br />
Ellen Regalado<br />
Dongchuan Guo, Ph.D.<br />
Christ<strong>in</strong>a Papke, Ph.D.<br />
Jiumei Cao, Ph.D.<br />
Stanford School of Medic<strong>in</strong>e<br />
Gary Ste<strong>in</strong>berg, MD PhD<br />
MD Anderson Cancer Center<br />
Aarif Khakoo, M.D.<br />
Meredith Rees<br />
Texas A&M<br />
Warren Zimmer, Ph.D.<br />
Soon-Mi Lim, Ph.D.<br />
Andreea Trache, Ph.D.<br />
University of Geneva<br />
Giulio Gabbiani, Ph.D.<br />
Christ<strong>in</strong>e Chaponnier, Ph.D.<br />
Acknowledgements<br />
Fund<strong>in</strong>g<br />
NIH P50HL083794-01<br />
NIH R01HL034786<br />
Vivian L. Smith Foundation