# Flowerbed-inspired biomimetic 3D-printed scaffolds functionalized with urine-derived stem cell exosomes promote alveolar bone regeneration by regulating energy metabolism

## TL;DR

A 3D-printed scaffold inspired by flowerbeds and enhanced with stem cell exosomes promotes alveolar bone regeneration by regulating energy metabolism.

## Contribution

A novel biomimetic scaffold combining 3D bioprinting and urine-derived stem cell exosomes to regulate energy metabolism for bone regeneration.

## Key findings

- The scaffold showed high printing fidelity and sustained exosome release for over 16 days.
- The scaffold increased ATP content and promoted osteogenic differentiation of stem cells.
- In vivo, the scaffold led to a 3-fold increase in vessel density and 65.6% new bone volume after 8 weeks.

## Abstract

Rationale: The anatomical complexity and restricted regenerative potential of alveolar bone defects create a significant clinical challenge and highlight the need for spatially biomimetic and biologically supportive biomaterials.

Methods: We developed a bone-mimicking matrix hydrogel scaffold inspired by the features of a “flowerbed,” utilizing machine learning-guided three-dimensional bioprinting. Gelatin methacrylate (GelMA), decellularized bone matrix (DBM), and urine-derived stem cell exosomes (USC-Exos) were co-integrated during the printing process to deliver crucial biophysical and biochemical signals for bone regeneration.

Results: The GelMA/DBM/USC-Exos scaffold exhibited high printing fidelity, enabling precise fabrication of defect-specific geometries while preserving exosome bioactivity and achieving sustained release (> 16 days). Functionally, the scaffold promoted M2 macrophage polarization and markedly upregulated osteogenic and angiogenic gene expression, which was approximately 2-fold higher than that of the control (p < 0.01). Mechanistically, the scaffold enhanced oxidative phosphorylation by activating the AMP-activated protein kinase pathway, resulting in a nearly 2-fold increase in adenosine triphosphate content and promoting the osteogenic differentiation of jawbone marrow-derived mesenchymal stem cells. In vivo implantation in mandibular defect models induced robust neovascularization and bone formation, resulting in a nearly 3-fold increase in vessel density and 65.6 ± 3.0% new bone volume after 4 and 8 weeks, respectively, effectively promoting coordinated and functional alveolar bone regeneration.

Conclusions: This study establishes a biomimetic approach that integrates structural biomimicry, exosome-mediated bioactivity, and energy metabolism regulation, offering a promising and targeted strategy for personalized alveolar bone regeneration.