Scaffold-assisted assembly of cell-laden microgels to engineer permeable living constructs for vascularized adipose tissue regeneration

Integrating acellular scaffolds with cell-laden hydrogels holds great potential for engineering soft tissue constructs with structural integrity and uniform cellular distribution. However, achieving sustained and viable tissue regeneration remains a challenge due to poor nutrient diffusion and vascularization in bulk hydrogels. We propose to incorporate cell-laden microgels into polymeric scaffolds to engineer highly-permeable living constructs for vascularized adipose tissue regeneration. The cell-laden microgels, with the size ranging from 200 μm to 600 μm, are produced by electrospraying, coated with fibrin precursors, and embedded in a polymeric scaffold to form a mechanically robust construct with interconnected microporous structures. The microgels with a size of ∼200 μm exhibited better mass diffusion, improving viability and proliferation of encapsulated adipose tissue-derived stem cells compared with the bulk hydrogel. Human umbilical vein endothelial cells can be further introduced into the voids among the cell-laden microgels to form a pre-vascularized cellular network inside the assembled constructs. In vivo, the permeable living constructs can effectively maintain their original shape, significantly enhance tissue infiltration, promote vascularization, and alleviate hypoxia, thereby facilitating adipose tissue regeneration. The scaffold-assisted cell-laden microgel assembly strategy provides new insights into engineering living constructs with a structurally stable, permeable microenvironment for vascularized tissue regeneration. Statement of significance This work reports a scaffold-assisted strategy for assembling ADSC-laden electrosprayed microgels within a 3D-printed polymeric scaffold to create a mechanically robust yet permeable living construct for vascularized adipose tissue regeneration. The inherent inter-microgel voids in the assembled living constructs facilitate mass diffusion, thereby enhancing cell viability and proliferation compared with those in bulk hydrogel. To create a pre-vascularized living construct, HUVECs are introduced into the voids among the cell-laden microgels, which form an endothelial network among the microgels and promote ADSC differentiation. Owing to their structural stability and high permeability, the engineered living constructs can maintain a designated regeneration volume upon in vivo implantation, with improved vessel and tissue ingrowth and reduced hypoxia, further enhancing adipogenesis.