OUP accepted manuscript

Mineralized Osteoblast-Derived Exosomes and 3D-printed Ceramic-based Scaffolds for Enhanced Bone Healing: A Preclinical Exploration

In regenerative medicine, addressing the complex challenge of bone tissue regeneration demands innovative strategies. Exosomes, nanoscale vesicles rich in bioactive molecules, have shown great promise in tissue repair. This study focuses on exosomes derived from mineralized osteoblasts (MOBs), which play a pivotal role in bone formation. We investigated the therapeutic potential of exosomes isolated from osteoblasts cultured in osteogenic medium for 21 days, delivered via 3D-printed gyroid scaffolds composed of hydroxyapatite (HA) and tricalcium phosphate (TCP). The exosomes were characterized through nanoparticle tracking analysis to determine size, morphology, and concentration, while proteomics revealed their cargo contents. In vitro, rabbit bone marrow mesenchymal stromal cells (rBMSCs) were cultured as monolayers and within ceramic scaffolds, where MOB-derived exosomes were shown to promote osteogenic differentiation. In vivo, their osteoconductive and bone augmentation capabilities were evaluated in two rabbit calvarial models, while the osteoinductive potential was further tested in a heterotopic mouse model. Neo-bone formation was assessed using µCT and histological analysis. Our findings demonstrated that MOB-derived exosomes upregulated bone-related gene expression and promoted mineralization in rBMSCs, even in the absence of osteogenic medium. Proteomics confirmed the presence of bone-associated proteins in these exosomes. In rabbit models, however, exosomes did not significantly enhance bone formation. In contrast, in the heterotopic mouse model, exosomes functionalized onto ceramic scaffolds exhibited strong osteoinductive activity. This study highlights the potential of MOB-derived exosomes to enhance 3D-printed ceramic scaffolds for bone regeneration, offering a promising avenue for bone healing without the need for additional growth factors or stem cells. STATEMENT OF SIGNIFICANCE: The here presented report of our project not only advances our understanding of the role of exosome-functionalized scaffolds in bone regeneration but also proposes a promising alternative to traditional growth factor- or cell-based approaches. We are confident that this study represents a novel and impactful contribution to the field.

Engineered stromal vascular fraction for tissue regeneration

The treatment of various tissue injuries presents significant challenges, particularly in the reconstruction of large and severe tissue defects, with conventional clinical methods often yielding suboptimal results. However, advances in engineering materials have introduced new possibilities for tissue repair. Bioactive components are commonly integrated with synthetic materials to enhance tissue reconstruction. Stromal vascular fraction (SVF), an adipose-derived cell cluster, has shown considerable potential in tissue regeneration due to its simple and efficient way of obtaining and its richness in growth factors. Therefore, this review illustrated the preparation, characterization, mechanism of action, and applications of engineered SVF in various tissue repair processes, to provide some references for the option of better methods for tissue defect reconstruction.

Influence of Scaffold Microarchitecture on Angiogenesis and Regulation of Cell Differentiation during the Early Phase of Bone Healing: A Transcriptomics and Histological Analysis

The early phase of bone healing is a complex and poorly understood process. With additive manufacturing, we can generate a specific and customizable library of bone substitutes to explore this phase. In this study, we produced tricalcium phosphate-based scaffolds with microarchitectures composed of filaments of 0.50 mm in diameter, named Fil050G, and 1.25 mm named Fil125G, respectively. The implants were removed after only 10 days in vivo followed by RNA sequencing (RNAseq) and histological analysis. RNAseq results revealed upregulation of adaptive immune response, regulation of cell adhesion, and cell migration-related genes in both of our two constructs. However, significant overexpression of genes linked to angiogenesis, regulation of cell differentiation, ossification, and bone development was observed solely in Fil050G scaffolds. Moreover, quantitative immunohistochemistry of structures positive for laminin revealed a significantly higher number of blood vessels in Fil050G samples. Furthermore, µCT detected a higher amount of mineralized tissue in Fil050G samples suggesting a superior osteoconductive potential. Hence, different filament diameters and distances in bone substitutes significantly influence angiogenesis and regulation of cell differentiation involved in the early phase of bone regeneration, which precedes osteoconductivity and bony bridging seen in later phases and as consequence, impacts the overall clinical outcome.

The Effect of Tissue Stromal Vascular Fraction as Compared to Cellular Stromal Vascular Fraction to Treat Anal Sphincter Incontinence

BACKGROUND

The long-term prognosis of current treatments for anal sphincter incontinence (ASI) is poor. Here, we explored the efficacy of tissue adipose stromal vascular fraction SVF (tSVF) on ASI and compared it to that of cellular SVF (cSVF). We then investigated possible mechanisms.

METHODS

Rat cSVF and tSVF were isolated and labeled with DIL. One day after modeling, three groups received phosphate-buffered saline (PBS), cSVF, tSVF, respectively. The control group received nil modeling nor any treatments. The effect was assessed by function test for anal pressure and electromyography, and staining for fiber content, proliferation and differentiation at day 5 and day 10.

RESULTS

cSVF injection resulted in faster healing than tSVF. The cSVF group showed significant improvement on anal pressure on day 10. For the electromyography test, cSVF showed significant improvement for the frequencies on day 10, and for the peak values on both time points, while tSVF showed significant improvement for the peak values on day 10. The two SVF both alleviated fibrosis. Immunofluorescence tracing identified differentiation of some injected cells towards myosatellite cells and smooth muscle cells in both SVF groups. For all the tests, the tSVF group tends to have similar or lower effects than the cSVF group with no significant difference.

CONCLUSION

cSVF and tSVF are both safe and effective in treating ASI, while the effect of cSVF is slighter higher than tSVF.