RESUMO
Scaffold-free bone microtissues differentiated from mesenchymal stem cell (MSC) spheroids offer great potential for bottom-up bone tissue engineering as a direct supply of cells and osteogenic signals. Many biomaterials or biomolecules have been incorporated into bone microtissues to enhance their osteogenic abilities, but these materials are far from clinical approval. Here, we aimed to incorporate hydroxyapatite (HAP) nanoparticles, an essential component of bone matrix, into MSC spheroids to instruct their osteogenic differentiation into bone microtissues and further self-organization into bone organoids with a trabecular structure. Furthermore, the biological interaction between HAP nanoparticles and MSCs and the potential molecular mechanisms in the bone development of MSC spheroids were investigated by both in vitro and in vivo studies. As a result, improved cell viability and osteogenic abilities were observed for the MSC spheroids incorporated with HAP nanoparticles at a concentration of 30 µg/mL. HAP nanoparticles could promote the sequential expression of osteogenic markers (Runx2, Osterix, Sclerostin), promote the expression of bone matrix proteins (OPN, OCN, and Collagen I), promote the mineralization of the bone matrix, and thus promote the bone development of MSC spheroids. The differentiated bone microtissues could further self-organize into linear, lamellar, and spatial bone organoids with trabecular structures. More importantly, adding FAK or Akt inhibitors could decrease the level of HAP-induced osteogenic differentiation of bone microtissues. Finally, excellent new bone regeneration was achieved after injecting bone microtissues into cranial bone defect models, which could also be eliminated by the Akt inhibitor. In conclusion, HAP nanoparticles could promote the development of bone microtissues by promoting the osteogenic differentiation of MSCs and the formation and mineralization of the bone matrix via the FAK/Akt pathway. The bone microtissues could act as individual ossification centers and self-organize into macroscale bone organoids, and in this meaning, the bone microtissues could be called microscale bone organoids. Furthermore, the bone microtissues revealed excellent clinical perspectives for injectable cellular therapies for bone defects.
RESUMO
Objective: Both impulsiveness and trait depression are the trait-level risk factors for depressive symptoms. However, the two traits overlap and do not affect depressive symptoms independently. This study takes impulsiveness and trait depression into a whole construct, aiming to find the complex associations among all facets and explore their relative importance in a trait network. It can help us find the key facets that need consideration in preventing depression. Materials and Methods: We used the Barratt Impulsiveness Scale (BIS) and Trait Depression Scale (T-DEP) as measuring tools, conducted network analysis, and applied the Graphic Least Absolute Shrinkage and Selection Operator (GLASSO) algorithm to estimate the network structure and compute the linkage and centrality indexes. The accuracy and stability of the indexes were estimated through bootstrapping. All the computations were performed by R script and packages. Results: We found that "trait anhedonia" was connected with "non-planning" and "cognitive" impulsiveness, while "trait dysthymia" was connected with "motor" impulsiveness. "Cognitive" impulsiveness had a statistically significant higher expected influence than "motor" impulsiveness and had the trend to be dominant in the network. "Trait dysthymia" had a statistically significant higher bridge expected influence than "cognitive" impulsiveness and had the trend to be the key facet linking impulsiveness with trait depression. "Non-only children" had higher network global strength than "only children." All indexes were accurate and stable. Conclusion: The present study confirms the complex associations among facets of trait depression and impulsiveness, finding that "cognitive" impulsiveness and "trait dysthymia" are the two key factors in the network. The results imply that different facets of impulsiveness should be considered respectively regarding anhedonia and dysthymia. "Cognitive" impulsiveness and "trait dysthymia" are critical to the prevention of depression.
