ABSTRACT
Bone critical-size defects and non-union fractures have no intrinsic capacity for self-healing. In this context, the emergence of bone engineering has allowed the development of functional alternatives. The aim of this study was to evaluate the capacity of ASC spheroids in bone regeneration using a synergic strategy with 3D-printed scaffolds made from poly (lactic acid) (PLA) and nanostructured hydroxyapatite doped with carbonate ions (CHA) in a rat model of cranial critical-size defect. In summary, a set of results suggests that ASC spheroidal constructs promoted bone regeneration. In vitro results showed that ASC spheroids were able to spread and interact with the 3D-printed scaffold, synthesizing crucial growth factors and cytokines for bone regeneration, such as VEGF. Histological results after 3 and 6 months of implantation showed the formation of new bone tissue in the PLA/CHA scaffolds that were seeded with ASC spheroids. In conclusion, the presence of ASC spheroids in the PLA/CHA 3D-printed scaffolds seems to successfully promote bone formation, which can be crucial for a significant clinical improvement in critical bone defect regeneration.
ABSTRACT
Biocompatible scaffolds are porous matrices that are bone substitutes with great potential in tissue regeneration. For this, these scaffolds need to have bioactivity and biodegradability. From this perspective, 3D printing presents itself as one of the techniques with the greatest potential for scaffold manufacturing with porosity and established structure, based on 3D digital modeling. Thus, the objective of the present work was to produce 3D scaffolds from the poly (lactic acid) (PLA) and the nanostructured hydroxyapatite doped with carbonate ions (CHA). For this purpose, filaments were produced via fusion for the fused-filament 3D printing and used to produce scaffolds with 50% porosity in the cubic shape and 0/90°configuration. The dispersive energy spectroscopy and Fourier transform infrared spectroscopy (FTIR) analysis demonstrated the presence of CHA in the polymeric matrix, confirming the presence and incorporation into the composite. The thermogravimetric analysis made it possible to determine that the filler concentration incorporated in the matrix was very similar to the proposed percentage, indicating that there were no major losses in the process of obtaining the filaments. It can be assumed that the influence of CHA as a filler presents better mechanical properties up to a certain amount. The biological results point to a great potential for the application of PLA/CHA scaffolds in bone tissue engineering with effective cell adhesion, proliferation, biocompatibility, and no cytotoxicity effects.
ABSTRACT
Top-down tissue engineering aims to produce functional tissues using biomaterials as scaffolds, thus providing cues for cell proliferation and differentiation. Conversely, the bottom-up approach aims to precondition cells to form modular tissues units (building-blocks) represented by spheroids. In spheroid culture, adult stem cells are responsible for their extracellular matrix synthesis, re-creating structures at the tissue level. Spheroids from adult stem cells can be considered as organoids, since stem cells recapitulate differentiation pathways and also represent a promising approach for identifying new molecular targets (biomarkers) for diagnosis and therapy. Currently, spheroids can be used for scaffold-free (developmental engineering) or scaffold-based approaches. The scaffold promotes better spatial organization of individual spheroids and provides a defined geometry for their 3D assembly in larger and complex tissues. Furthermore, spheroids exhibit potent angiogenic and vasculogenic capacity and serve as efficient vascularization units in porous scaffolds for bone tissue engineering. An automated combinatorial approach that integrates spheroids into scaffolds is starting to be investigated for macro-scale tissue biofabrication.