Urine-derived stem cells efficiently assemble into micro-bone organoids supported by decellularized bone matrix microparticles for rapidly repairing bone defects through direct filling and paracrine functions.

The repair of large bone defects remains a significant challenge in orthopedic clinical practice. This study aims to rapidly cultivate a novel type of bone organoids (BOs), namely uBOs (USCs@DBM-MPs derived BOs), by utilizing self-developed highly biomimetic decellularized bone matrix microparticles (DBM-MPs) as the supporting carrier in combination with non-invasively obtained urine-derived stem cells (USCs), and to explore its therapeutic efficacy and biological mechanism. In our vitro experiments confirmed that DBM-MPs exhibit excellent biocompatibility and osteoinductivity, and urine-derived stem cells (USCs) have comparable osteogenic potential to bone marrow stem cells (BMSCs). Furthermore, USCs were loaded onto DBM-MPs for osteogenic directional induction, and a novel bone organoid-uBOs, was successfully generated within 14 days. Meanwhile, compared with bBOs (BMSCs@DBM-MPs derived BOs), uBOs exhibit comparable levels of biological activity, proliferation characteristics, and osteogenic potential. Moreover, uBOs offer the advantages of a broader availability and a non-invasive acquisition process. What is particularly noteworthy is that these uBOs exhibit paracrine functions capable of promoting both angiogenesis and osteogenesis. In-vivo rat femoral condyle defect model, minimally invasive injection of uBOs into the bone defect area achieved rapid bone regeneration within only 6 weeks, perfectly repairing the defect area. The uBOs developed in this study not only as a bone substitute unit for direct filling and repair of bone defects, but also continuously induce angiogenesis and bone fusion at the defect site through their paracrine mechanism, offering a brand-new and efficient tissue engineering strategy for bone defect treatment.