3D-bioprinted bone scaffolds incorporating SR1 nanoparticles enhance blood vessel regeneration in rat calvarial defects

The inherent limitations of bone grafting in the treatment of critical-sized bone defects have led to a growing demand for bone repair implants. Three-dimensional (3D) bioprinting has emerged as a promising manufacturing technique for implants, offering flexibility in their structural design and the use of applicable materials. Although numerous 3D-bioprinted bone scaffolds have been developed to enhance osteogenesis, angiogenesis remains a challenge. Angiogenesis is crucial for successful bone healing because the process forms blood vessels to deliver essential nutrients and oxygen. Endothelial progenitor cells (EPCs) play a pivotal role in the early stages of vascularization. These cells, capable of differentiating into endothelial cells (ECs), are recruited from the bone marrow to the injured area during the healing process. CD34+ cells, a subset of EPCs, have gained attention because of their neovascularization potential and ability to contribute to bone regeneration. The incorporation of CD34+ cell-enhancing factors into 3D-printed bone scaffolds may facilitate successful bone healing in critical defects. StemRegenin-1 (SR1), a molecule that promotes CD34+ cell expansion, has shown promising results in increasing CD34+ hematopoietic stem and progenitor cell populations. This study aimed to investigate the sustained release of SR1 from a collagen-based scaffold integrated with mesoporous silica nanoparticles (MSNs) to promote angiogenesis and enhance bone healing. The sustained release of SR1 from the collagen scaffold is hypothesized to promote angiogenesis, thereby facilitating bone repair. In vitro studies have demonstrated the angiogenic potential of SR1; however, further in vivo investigations are required to establish its clinical efficacy. This study contributes to the development of novel therapies targeting CD34+ cells and demonstrates the potential of SR1 as a promising agent for promoting angiogenesis and enhancing bone healing in critical defects.