VEGF-C and aortic cardiomyocytes guide coronary artery stem development
Heidi I. Chen, Aruna Poduri, Harri Numi, Riikka Kivela, Pipsa Saharinen, Andrew S. McKay, Brian Raftrey, Jared Churko, Xueying Tian, Bin Zhou, Joseph C. Wu, Kari Alitalo, Kristy Red-Horse
Heidi I. Chen, Aruna Poduri, Harri Numi, Riikka Kivela, Pipsa Saharinen, Andrew S. McKay, Brian Raftrey, Jared Churko, Xueying Tian, Bin Zhou, Joseph C. Wu, Kari Alitalo, Kristy Red-Horse
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Research Article Vascular biology

VEGF-C and aortic cardiomyocytes guide coronary artery stem development

Abstract

Coronary arteries (CAs) stem from the aorta at 2 highly stereotyped locations, deviations from which can cause myocardial ischemia and death. CA stems form during embryogenesis when peritruncal blood vessels encircle the cardiac outflow tract and invade the aorta, but the underlying patterning mechanisms are poorly understood. Here, using murine models, we demonstrated that VEGF-C–deficient hearts have severely hypoplastic peritruncal vessels, resulting in delayed and abnormally positioned CA stems. We observed that VEGF-C is widely expressed in the outflow tract, while cardiomyocytes develop specifically within the aorta at stem sites where they surround maturing CAs in both mouse and human hearts. Mice heterozygous for islet 1 (Isl1) exhibited decreased aortic cardiomyocytes and abnormally low CA stems. In hearts with outflow tract rotation defects, misplaced stems were associated with shifted aortic cardiomyocytes, and myocardium induced ectopic connections with the pulmonary artery in culture. These data support a model in which CA stem development first requires VEGF-C to stimulate vessel growth around the outflow tract. Then, aortic cardiomyocytes facilitate interactions between peritruncal vessels and the aorta. Derangement of either step can lead to mispatterned CA stems. Studying this niche for cardiomyocyte development, and its relationship with CAs, has the potential to identify methods for stimulating vascular regrowth as a treatment for cardiovascular disease.

Authors

Heidi I. Chen, Aruna Poduri, Harri Numi, Riikka Kivela, Pipsa Saharinen, Andrew S. McKay, Brian Raftrey, Jared Churko, Xueying Tian, Bin Zhou, Joseph C. Wu, Kari Alitalo, Kristy Red-Horse

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Figure 6

ISL1 heterozygosity decreases aortic cardiomyocytes and disrupts normal stem development and positioning.

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ISL1 heterozygosity decreases aortic cardiomyocytes and disrupts normal ...
(A) Second heart field lineage tracing (Mef2c-AHF-Cre, RosamTmG) labels aortic cardiomyocytes (CMs, arrows). (B) Confocal images of wild-type and Isl1 heterozygous embryos showing decreased numbers of cardiomyocytes within the aorta (dotted line). The pulmonary artery is also outlined (solid lines). Cardiomyocytes (cTnT+) are shown in red; peritruncal vessels (VE-cadherin+) are shown in blue. The bottom panel shows only the cTnT channel where red lines indicate the stem position. (C) Boxed regions in A showing only the cTnT channel. (D) Quantification of the length distal to the valve occupied by aortic cardiomyocytes shows a significant decrease in Isl1 mutant hearts. (E and F) Other developmental parameters, (E) smooth muscle cell development and (F) coronary vessel growth, are unchanged in mutant hearts. (D–F) Data represent mean ± SD. Each dot represents a value obtained from one sample. (G) Isl1 heterozygous hearts have abnormally low stem positioning with respect to the valves (lines) in comparison to wild-type hearts. (H) Distribution of stem phenotypes observed in Isl1 mutant and wild-type hearts. n values are shown on the right. (I) The height of CA stems does not significantly rise above the level of aortic cardiomyocytes in both wild-type and mutant hearts, as evidenced by the paucity of points in the pink area (y > x) of the graph. These data were measured at E14.5. A linear regression for the data set (dotted line, y = 0.5999x – 36.39) indicates a positive correlation. ****P < 0.0001; NS ≥ 0.05. Scale bars: 100 μm.