https://pages.htgaa.org/2026b/emmanuel-cardenas-barcelo/week-02-hw-dna-design/index.htmlSynthetic Vascularization Encoded by PDGF-BB for Bioprinted Liver Tissue Emmanuel Cárdenas Barceló Barranquilla, Colombia emmanuel2003cardenas@gmail.com Part 1: Define your expression target What molecule are you expressing? Given the needs of the product, the molecule best aligned for expression is PDGF-BB (Platelet-Derived Growth Factor BB), a secreted growth factor that in my system will be produced by the endothelial cells lining the vascular channel. Its role is to recruit pericytes to the abluminal surface of the newly formed endothelium, a step needed to prevent vessel regression and local hemorrhage inside the printed channel (Zhang et al., 2021). Another option for this work is VEGF-A (Vascular Endothelial Growth Factor A), the factor that triggers the initial stage of the vascular cascade by activating endothelial cells to migrate, proliferate and form the lumen inside the printed channel (Son et al., 2025; Cai et al., 2025). Although it was a viable option, I prioritized PDGF-BB over VEGF-A because sustained overexpression of VEGF-A has been reported to cause leaky and unstable vessels (Son et al., 2025), whereas PDGF-BB acts specifically in the pericyte recruitment and adhesion stage that my design needs to accelerate.Hugoen