Biomimetic hydroxyapatite coating on the 3D-printed bioactive porous composite ceramic scaffolds promoted osteogenic differentiation via PI3K/AKT/mTOR signaling pathways and facilitated bone regeneration in vivo

The architecture and surface modifications have been regarded as effective methods to enhance the bi-ological response of biomaterials in bone tissue engineering.The porous architecture of the implanta-tion was essential conditions for bone regeneration.Meanwhile,the design of biomimetic hydroxyap-atite(HAp)coating on porous scaffolds was demonstrated to strengthen the bioactivity and stimulate osteogenesis.However,bioactive bio-ceramics such asβ-tricalcium phosphate(β-TCP)and calcium sili-cate(CS)with superior apatite-forming ability were reported to present better osteogenic activity than that of HAp.Hence in this study,3D-printed interconnected porous bioactive ceramicsβ-TCP/CS scaf-fold was fabricated and the biomimetic HAp apatite coating were constructed in situ via hydrothermal reaction,and the effects of HAp apatite layer on the fate of mouse bone mesenchymal stem cells(mBM-SCs)and the potential mechanisms were explored.The results indicated that HAp apatite coating en-hanced cell proliferation,alkaline phosphatase(ALP)activity,and osteogenic gene expression.Further-more,PI3K/AKT/mTOR signaling pathway is proved to have an important impact on cellular functions.The present results demonstrated that the key molecules of phosphatidylinositol 3-kinase(PI3K),protein kinase B(AKT)and mammalian target of rapamycin(mTOR)were activated after the biomimetic hydrox-yapatite coating were constructed on the 3D-printed ceramic scaffolds.Besides,the activated influence on the protein expression of Runx2 and BMP2 could be suppressed after the treatment of inhibitor HY-10358.In vivo studies showed that the constructed HAp coating promoted bone formation and strengthen the bone quality.These results suggest that biomimetic HAp coating constructed on the 3D-printed bioac-tive composite scaffolds could strengthen the bioactivity and the obtained biomimetic multi-structured scaffolds might be a potential alternative bone graft for bone regeneration.

Simultaneous incorporation of PTH(1-34) and nano-hydroxyapatite into Chitosan/Alginate Hydrogels for efficient bone regeneration

Tissue regeneration based on the utilization of artificial soft materials is considered a promising treatment for bone-related diseases.Here,we report cranial bone regeneration promoted by hydrogels that contain parathyroid hormone(PTH)peptide PTH(1-34)and nano-hydroxyapatite(nHAP).A combination of the positively charged natural polymer chitosan(CS)and negatively charged sodium alginate led to the formation of hydrogels with porous structures,as shown by scanning electron microscopy.Rheological characterizations revealed that the mechanical properties of the hydrogels were almost maintained upon the addition of nHAP and PTH(1-34).In vitro experiments showed that the hydrogel containing nHAP and PTH(1-34)exhibited strong biocompatibility and facilitated osteogenic differentiation of rat bone marrow mesenchymal stem cells(rBMSCs)via the Notch signaling pathway,as shown by the upregulated expression of osteogenic-related proteins.We found that increasing the content of PTH(1-34)in the hydrogels resulted in enhanced osteogenic differentiation of BMSCs.Implantation of the complex hydrogel into a rat cranial defect model led to efficient bone regeneration compared to the rats treated with the hydrogel alone or with nHAP,indicating the simultaneous therapeutic effect of nHAP and PTH during the treatment process.Both the in vitro and in vivo results demonstrated that simultaneously incorporating nHAP and PTH into hydrogels shows promise for bone regeneration,suggesting a new strategy for tissue engineering and regeneration in the future.