Engineering Fibroblast with Reprogramming and Spheronization for Bone Defect Repair

Bone diseases profoundly affect patients, particularly the elderly, leading to severe health complications and disabilities. Osteoblasts play a crucial role in bone formation and are ideal candidates for treating bone diseases and engineering living materials. However, the stem and progenitor cells that give rise to osteoblasts, as well as osteoblasts themselves, exhibit dysfunction with aging. Although chemical reprogramming of fibroblasts into osteoblasts has been achieved, effective cell-based therapies or living materials have not been established in clinical practice. Here, we present a method using small molecules to achieve complete osteoblastic specification from human fibroblasts across all age groups. By targeting Wnt signaling pathways and modularizing small molecules and their combinations based on their effects on stage-specific genes, we optimized the temporal regulation of small molecules in reprogramming, achieving healthy induced osteoblasts(iOBs). The iOBs with traits of young native osteoblasts are ideal for forming transplantable tissue spheroids with improved survival, self-bone formation, and accelerated local angiogenesis in vivo, promoting effective bone defect repair. The material-free spheroids function as living, self-scaffolding building blocks for biofunctional constructs that reproduce tissue composition, maintain high cell density, and support matrix remodeling, offering a promising avenue for clinical autologous bone defect repair.