Effective\nBone Tissue Fabrication Using 3D-Printed\nCitrate-Based Nanocomposite Scaffolds Laden with BMP9-Stimulated Human\nUrine Stem Cells

Effective repair\nof large bone defects through bone tissue engineering\n(BTE) remains an unmet clinical challenge. Successful BTE requires\noptimal and synergistic interactions among biocompatible scaffolds,\nosteogenic factors, and osteoprogenitors to form a highly vascularized\nmicroenvironment for bone regeneration and osseointegration. We sought\nto develop a highly effective BTE system by using 3D printed citrate-based\nmPOC/hydroxyapatite (HA) composites laden with BMP9-stimulated human\nurine stem cells (USCs). Specifically, we synthesized and characterized\nmethacrylate poly(1,8 octamethylene citrate) (mPOC), mixed it with\n0%, 40% or 60% HA (i.e., mPOC-0HA, mPOC-40HA, or mPOC-60HA), and fabricated\ncomposite scaffold via micro-continuous liquid interface production\n(μCLIP). The 3D-printed mPOC-HA composite scaffolds were compatible\nwith human USCs that exhibited high osteogenic activity <i>in\nvitro</i> upon BMP9 stimulation. Subcutaneous implantation of\nmPOC-HA scaffolds laden with BMP9-stimulated USCs revealed effective\nbone formation in all three types of mPOC-HA composite scaffolds.\nHistologic evaluation revealed that the mPOC-60HA composite scaffold\nyielded the most mature bone, resembling native bone tissue with extensive\nscaffold-osteointegration. Collectively, these findings demonstrate\nthat the citrate-based mPOC-60HA composite, human urine stem cells,\nand the potent osteogenic factor BMP9 constitute a desirable triad\nfor effective bone tissue engineering.