The long-term goal of this project is to identify cellular and molecular mechanisms that regulate the development and function of the tunica adventitia, an important but poorly understood layer of artery wall. We recently discovered a sonic hedgehog (Shh) signaling domain in developing conduit arteries and veins that is localized exclusively to the adventitia and contains resident Sca1+ progenitor cells (AdvSca1). In vertebrates, Hh proteins are morphogens that activate smoothened (SMO)-dependent signaling pathways to pattern connective tissue, control arterial-venous identity, and direct growth and survival functions for lineage-specific stem/progenitor cells. In the vascular system, the adventitia plays important roles in artery wall homeostasis and disease. The adventitia contains vasa vasorum microvessels that are key conduits for leukocyte trafficking into and out of atherosclerotic lesions. In addition, vessel wall remodeling, arterial tone and compliance, and perivascular adipose tissue are all critically dependent on the adventitia. Most forms of arterial injury evoke rapid and robust adventitial reactions suggesting that cellular and molecular pathways that sense and respond to injury are intrinsic functions of adventitial cells. Our published and preliminary data identify a resident Shh- dependent progenitor cell population that is mobilized in response to multiple forms of vascular injury. Our preliminary studies using ShhEGFP/+ reporter mice suggest that the primary producers of Shh in the adventitia are AdvSca1 cells themselves. By contrast, Gli1lacZ/+, Ptc1lacZ/+, and Ptc2lacZ/+ reporter mice indicate that the majority of Shh-responsive cells in the adventitia are CD68+, F4/80+, and Csf1R+ resident macrophage-like cells (AdvRM). AdvRM cells are clustered in close proximity to, or in direct contact with, AdvSca1 cells in the inner adventitia. These results raise the novel possibility of a progenitor cell niche in the inner adventitia that is formed and maintained by reciprocal signaling interactions between AdvSca1 progenitor cells and AdvRMs. We propose that cells within the adventitial progenitor niche function at the media-adventitia interface to initiate compensatory wall remodeling and repair responses via paracrine signaling pathways in the vessel wall. To test this novel hypothesis, we will emphasize whole animal experiments and genetic fate mapping approaches in vivo. The results of this project will change our current understanding of the roles of the adventitia in development, homeostasis and disease of the artery wall.

Public Health Relevance

The research proposed in this application seeks to identify new targets for regenerative therapies directed to the artery wall. We discovered that embryonic morphogen signaling pathways support resident vascular stem/progenitor cells in the outer layer of artery wall called the tunica adventitia. Our studies will test the functions of these cells in artery wall development, repair and disease. We believe new therapeutic targets will emerge from further study of the adventitial layer of the artery wall.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL123650-02
Application #
8898210
Study Section
Vascular Cell and Molecular Biology Study Section (VCMB)
Program Officer
Gao, Yunling
Project Start
2014-08-01
Project End
2018-05-31
Budget Start
2015-07-01
Budget End
2016-05-31
Support Year
2
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Seattle Children's Hospital
Department
Type
DUNS #
048682157
City
Seattle
State
WA
Country
United States
Zip Code
98101
Bentzon, Jacob F; Majesky, Mark W (2018) Lineage tracking of origin and fate of smooth muscle cells in atherosclerosis. Cardiovasc Res 114:492-500
Brewer, Chris M; Majesky, Mark W (2018) Branch Point Smooth Muscle Cells Highlighted by Novel Lineage Tracking Approach. Circ Res 122:194-196
Majesky, Mark W (2018) Vascular Development. Arterioscler Thromb Vasc Biol 38:e17-e24
Berthiaume, Andrée-Anne; Hartmann, David A; Majesky, Mark W et al. (2018) Pericyte Structural Remodeling in Cerebrovascular Health and Homeostasis. Front Aging Neurosci 10:210
Majesky, Mark W; Horita, Henrick; Ostriker, Allison et al. (2017) Differentiated Smooth Muscle Cells Generate a Subpopulation of Resident Vascular Progenitor Cells in the Adventitia Regulated by Klf4. Circ Res 120:296-311
Wu, Jing; Montaniel, Kim Ramil C; Saleh, Mohamed A et al. (2016) Origin of Matrix-Producing Cells That Contribute to Aortic Fibrosis in Hypertension. Hypertension 67:461-8
Majesky, Mark W (2016) Vascular Smooth Muscle Cells. Arterioscler Thromb Vasc Biol 36:e82-6
Kuang, Shao-Qing; Medina-Martinez, Olga; Guo, Dong-Chuan et al. (2016) FOXE3 mutations predispose to thoracic aortic aneurysms and dissections. J Clin Invest 126:948-61
Strub, Graham M; Kirsh, Andrew L; Whipple, Mark E et al. (2016) Endothelial and circulating C19MC microRNAs are biomarkers of infantile hemangioma. JCI Insight 1:e88856
Kao, Robert M; Rurik, Joel G; Farr 3rd, Gist H et al. (2015) Pbx4 is Required for the Temporal Onset of Zebrafish Myocardial Differentiation. J Dev Biol 3:93-111

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