Hydrogel Microfibers-Mediated Engineering Vascularized High-Cell-Density Tissues with Structural Developmental Reinforcement

Abstract

Engineering vascularized high-cell-density (HCD) tissues is pivotal for recapitulating the physiological functions of biomimetic constructs in vitro. However, traditional strategy that directly mix high-density cells with polymeric hydrogels remain challenging. To address these bottlenecks, might we move beyond the traditional strategy of mixing high-density cells with dense polymer hydrogels? Instead, could the self-sustained proliferation of basic cells together with endothelial vascularization be harnessed to construct vascularized HCD tissues exhibiting structural developmental reinforcement? Here, by integrating fiber-inducing factors from natural cell-extracellular matrix (ECM) structures with porous matrices, we propose a model where biomimetic structural units are directly mixed with a specific quantity of basic cells to construct a porous structural carrier that confines cells to two-dimensional constraints within microfibers. The two-dimensional constraint method using microfiber units eliminates the confining constraints of traditional hydrogel networks on cells, providing ample physiological space for rapid extension, migration, and proliferation. Meanwhile, the strategy of combining microfiber units with porous hydrogels significantly enhances structural porosity while ensuring structural integrity and strength, preventing collapse. Within this porous biomimetic microfiber system, basic cells proliferate continuously, strengthening intercellular interactions and reinforcing the structure’s overall mechanical properties and stability. Furthermore, the microfibrillar framework provides ECM-like cues that promote ordered expansion and spontaneous vascular formation. Introducing human bone marrow-derived mesenchymal stem cells (BMSCs) enables paracrine pro-angiogenic signaling to stimulate endothelial proliferation and migration. The synergistic effect of spatial structural induction and biological signaling stimulation significantly promotes the generation and maturation of vascular-like structures within the system. The tissue engineering strategy of mixing biomimetic microfiber units with a specific quantity of basic cells overcomes the limitations of traditional methods involving direct mixing of dense polymer hydrogels with large numbers of cells. This approach offers a novel solution for constructing vascularized, HCD tissues with physiological strength.

Graphical Abstract