Chronological Changes in Tip Cells during Sprouting Angiogenesis of Development of the Retinal Vasculature in Newborn Mice

ABSTRACT

Purpose: To investigate a sequential chronological change in tip cells during the development of the retinal vasculature in newborn mice.

Materials and Methods: Newborn C57BL/6 mice were used for this study. To elucidate the patterns in the developing retinal vasculature, histology, and immunohistochemistry—antiplatelet endothelial cell adhesion molecule-1, anticollagen type IV, isolectin IB₄—were performed on sections of mouse retina on postnatal days (P)-4, -8, and -12. Staining patterns of isolectin IB₄-stained arterial and venous tip cells were compared in retinal wholemounts, in which the numbers and characteristics of tip cells were compared between arteries and veins on P-4, -6, and -8. In addition, vascular densities and branching patterns were compared between arterial and venous vascular forefront areas.

Results: Tip cells in the superficial vascular plexus were observed until P-8. The number of tip cells was highest on P-6, decreasing dramatically from P-6 to P-8 (P-4, 165.2 ± 10.1, n = 17; P-6, 183.8 ± 19.4, n = 15; P8, 21.4 ± 6.4, n = 15) (p < 0.05, respectively, t-test). There was a greater number of tip cells in veins versus arteries on P-4 and P-6 (P-4, 91.0 ± 9.2 veins versus 74.2 ± 10.4 arteries; P-6, 104.0 ± 10.2 veins versus 79.8 ± 11.3 arteries) (p < 0.05, respectively). Arterial tip cells had thinner and longer sprouts compared with venous tip cells (basal thickness: 15.7 ± 8.7 veins versus 9.9 ± 3.5 μm arteries) (length, 20.3 ± 9.1 veins versus 37.1 ± 13.2 μm arteries on P-4) (p < 0.05, respectively). Vessel areas and densities of vascular branch points were significantly higher around veins compared to arteries (vessel areas: 58.9 ± 1.2% veins versus 40.8 ± 1.9% arteries; vascular branch points, 1371.9 ± 136.7/mm² veins versus 1046.7 ± 175.5/mm² arteries) (p < 0.05, respectively).

Conclusion: The number of tip cells increased to a greater extent in the superficial vascular plexus of veins versus arteries until P-6. Consequently, there are more vessel areas and vascular branch points near retinal veins versus arteries. Arterial tip cells are longer and thinner than the shorter and thicker venous tip cells.

KEYWORDS:

• Retina
• tip cell
• vascular development
• vascular remodeling
• sprout

Funding

This study was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1A6A3A04004741), the Pioneer Research Program of NRF/MEST (2012-0009544), the Bio & Medical Technology Development Program of the NRF, and MSIP (NRF-2015M3A9E6028949), the Development of Platform Technology for Innovative Medical Measurements Program from Korea research Institute of Standards and Science (KRISS–2016-16011064), and the Interdisciplinary Research Initiatives Program from College of Engineering and College of Medicine, Seoul National University (800-2016-0082).

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This study was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1A6A3A04004741), the Pioneer Research Program of NRF/MEST (2012-0009544), the Bio & Medical Technology Development Program of the NRF, and MSIP (NRF-2015M3A9E6028949), the Development of Platform Technology for Innovative Medical Measurements Program from Korea research Institute of Standards and Science (KRISS–2016-16011064), and the Interdisciplinary Research Initiatives Program from College of Engineering and College of Medicine, Seoul National University (800-2016-0082).