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. 2021 Mar 19;9:620128. doi: 10.3389/fbioe.2021.620128

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Copyright © 2021 Wang, Jarman, Lin and Baker.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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Endothelial sprout invasion speed is anti-correlated with sprout diameter. (A) Schematic overview of multiplexed angiogenesis-on-a-chip platform. Polydimethylsiloxane (PDMS) replica casts are generated from 3D printed molds and are composed of a 2 × 4 array of single devices. These PDMS molds are bonded to glass coverslips and functionalized with glutaraldehyde (Step 1). Gelatin-coated needles are then inserted into the device (Step 2). Type 1 collagen hydrogel precursor solution is injected into each device, allowed to cross-link around the needles, and hydrated overnight (Step 3). Needle removal generates 3D channels fully embedded within user-defined hydrogel (Step 4). Each device is composed of two parallel channels: (1) an endothelial channel seeded with endothelial cells (ECs) to serve as the parent vessel from which angiogenic sprouting is induced and (2) a chemokine channel to which pro-angiogenic factors [e.g., sphingosine 1-phosphate (S1P)] are added to generate diffusive gradients that promote EC activation and invasion across a user-defined 3D extracellular matrix (e.g., collagen hydrogel). (B) Representative images (max intensity projections) of invading ECs in response to varying S1P. All conditions were cultured for 5 days with indicated S1P dose in endothelial cell growth medium 2 [EGM2; supplemented with 25 ng ml^–1 phorbol 12-myristate 13-acetate (PMA)] added to the chemokine channel within 3 mg ml^–1 collagen hydrogels. F-actin (cyan), nuclei (magenta), and yellow dashed lines indicate parent vessel edge. (C,D) Quantifications of invasion speed and sprout diameter as a function of S1P. For invasion speed: n ≥ 36 per condition and for sprout diameter: n ≥ 55 per condition. (E) Relationship between invasion speed and sprout diameter, with red dashed line indicating a linear regression and statistical analysis performed by Pearson’s correlation. Sample size for each mean was taken from panels (C,D). All data presented as mean ± SD; ^∗indicates a statistically significant comparison with P < 0.05 (one-way analysis of variance).