Three-dimensional (3D) bioprinting is an emerging method for tissue regeneration. However, promoting the epithelial-mesenchymal interaction (EMI), while maintaining the characteristics of epithelial cells has always been a challenge in tissue engineering. Since EMI acts as a critical factor in bone regeneration, this study aims to promote EMI by recombining epithelial and mesenchymal cells through 3D bioprinting. Hertwig’s epithelial root sheath (HERS) is a transient structure appeared in the process of tooth root formation. Its epithelial characteristics are easy to attenuate under appropriate culture environment. We recombined HERS cells and dental papilla cells (DPCs) through 3D bioprinting to simulate the micro-environment of cell-cell interaction in vivo. HERS cells and DPCs were mixed with gelatin methacrylate (GelMA) separately to prepare bio-inks for bioprinting. The cells/GelMA constructs were transplanted into the alveolar socket of Sprague-Dawley rats and then observed for 8 weeks. Hematoxylin and eosin staining, Masson staining, and immunohistochemical analysis showed that dimensional cultural pattern provided ideal environment for HERS cells and DPCs to generate mineralization texture and promote alveolar bone regeneration through their interactions. 3D bioprinting technology provides a new way for the co-culture of HERS cells and DPCs and this study is inspiring for future research on EMI model.
Xenogenic organ transplantation has been considered the most promising strategy in providing possible substitutes with the physiological function of the failing organs as well as solving the problem of insufficient donor sources. However, the xenograft, suffered from immune rejection and ischemia-reperfusion injury (IRI), causes massive reactive oxygen species (ROS) expression and the subsequent cell apoptosis, leading to the xenograft failure. Our previous study found a positive role of PPAR-γ in anti-inflammation through its immunomodulation effects, which inspires us to apply PPAR-γ agonist rosiglitazone (RSG) to address survival issue of xenograft with the potential to eliminate the excessive ROS. In this study, xenogenic bioroot was constructed by wrapping the dental follicle cells (DFC) with porcine extracellular matrix (pECM). The hydrogen peroxide (H2O2)-induced DFC was pretreated with RSG to observe its protection on the damaged biological function. Immunoflourescence staining and transmission electron microscope were used to detect the intracellular ROS level. SD rat orthotopic transplantation model and superoxide dismutase 1 (SOD1) knockout mice subcutaneous transplantation model were applied to explore the regenerative outcome of the xenograft. It showed that RSG pretreatment significantly reduced the adverse effects of H2O2 on DFC with decreased intracellular ROS expression and alleviated mitochondrial damage. In vivo results confirmed RSG administration substantially enhanced the host’s antioxidant capacity with reduced osteoclasts formation and increased periodontal ligament-like tissue regeneration efficiency, maximumly maintaining the xenograft function. We considered that RSG preconditioning could preserve the biological properties of the transplanted stem cells under oxidative stress (OS) microenvironment and promote organ regeneration by attenuating the inflammatory reaction and OS injury.
Cell polarity is essential for ameloblast differentiation and enamel formation. Smurf1 can mediate cell polarization through ubiquitination degradation of specific substrates. But it remains unclear whether Smurf1 could regulate ameloblast polarity and the underlying mechanism. Here, immuno-fluorescence staining and RT-qPCR were applied to detect the expression of Smurf1 and F-actin. A mouse lower incisor defect model was constructed. Scanning electron microscope, rat lower incisor culture, western blot, wound healing assay and trans-well migration assay were performed to detect the influence of Smurf1 knockdown on ameloblast. IF double staining, western blot and co-immunoprecipitation were conducted to detect the interaction between Smurf1 and RhoA. The in vivo experiment was also performed.We found that Smurf1 was mainly expressed in the membrane and cell cortex of ameloblast, similar to F-actin. Smurf1 expression increased along ameloblast polarization and differentiation. After knocking down Smurf1, the cytoskeleton and cell morphology changed and the cell polarity was damaged. Smurf1 regulated ameloblast polarity through ubiquitination degradation of activated RhoA in vitro. Local knockdown of Smurf1 in rat lower incisor ameloblast resulted in ameloblast polarity loss, enamel matrix secretion disorder and chalky enamel, but RhoA inhibitor Y-27632 could reverse this effect. Collectively, Smurf1 could regulate the polarization of ameloblast through ubiquitination degradation of activated RhoA, which contributed to the knowledge of tooth development and provided new research ideas for cell polarity.
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