Generation of Self-Organizing Macrovascular Constructs by Bioprinting human iPSC-Derived Mesodermal Progenitor Cells

Vascularization remains a major obstacle in tissue engineering. Here, we introduce a developmentally inspired bioprinting strategy to generate centimeter-scale, self-organising "mother vessel" constructs from iPSC-derived human mesodermal progenitor cells (hiMPCs). By systematically optimizing the bioink composition, we identified a formulation that combines high print fidelity, mechanical stability and cell compatibility within a single-step bioprinting process. Within the first week after printing, hiMPCs in the "mother vessel" constructs underwent spontaneous differentiation and morphogenesis, forming intima-, media-, and adventitia-like layers containing CD31 endothelial, SMA mural and CD34/CD150 progenitor cells. Remarkably, Iba1 macrophage-like cells appeared despite their absence in the initial population, indicating intrinsic differentiation into both vascular and non-vascular lineages essential for angiogenesis, remodeling and tissue homeostasis. Surrounding the newly formed vessel wall-like structure was a broad, vascularized mesodermal tissue compartment that also contained the above-mentioned progenitors. Co-culture with prevascularized mesodermal organoids resulted in early structural interconnection of microvessels with the printed wall, representing a prerequisite for subsequent hierarchical vascular network formation. As a proof-of-concept, the mother vessel withstood controlled flow conditions in a bioreactor without detectable leakage, demonstrating its principal suitability for perfusion analyses. Together, these findings establish a biologically driven platform that bridges macro- and microvascularization. This may pave the way toward perfusable, vascularized larger tissue constructs, a major bottleneck in regenerative biofabrication.