Lunguo Xia

Enhanced osteoporotic bone regeneration by strontium-substituted calcium silicate bioactive ceramics

The regeneration capacity of the osteoporotic bones is generally lower than that of the normal bones. Current methods of bone defect treatment for osteoporosis are not always satisfactory. Recent studies have shown that the silicate based biomaterials can stimulate osteogenesis and angiogenesis due to the silicon (Si) ions released from the materials, and enhance bone regeneration in vivo. Other studies showed that strontium (Sr) plays a distinct role on inhibiting bone resorption. Based on the hypothesis that the combination of Si and Sr may have synergetic effects on osteoporotic bone regeneration, the porous Sr-substituted calcium silicate (SrCS) ceramic scaffolds combining the functions of Sr and Si elements were developed with the goals to promote osteoporotic bone defect repair. The effects of the ionic extract from SrCS on osteogenic differentiation of bone marrow mesenchymal stem cells derived from ovariectomized rats (rBMSCs-OVX), angiogenic differentiation of human umbilical vein endothelial cells (HUVECs) were investigated. The in vitro results showed that Sr and Si ions released from SrCS enhanced cell viability, alkaline phosphatase (ALP) activity, and mRNA expression levels of osteoblast-related genes of rBMSCs-OVX and expression of vascular endothelial growth factor (VEGF) without addition of extra osteogenic and angiogenic reagents. The activation in extracellular signal-related kinases (ERK) and p38 signaling pathways were observed in rBMSCs-OVX cultured in the extract of SrCS, and these effects could be blocked by ERK inhibitor PD98059, and P38 inhibitor SB203580, respectively. Furthermore, the ionic extract of SrCS stimulated HUVECs proliferation, differentiation and angiogenesis process. The in vivo experiments revealed that SrCS dramatically stimulated bone regeneration and angiogenesis in a critical sized OVX calvarial defect model, and the enhanced bone regeneration might be attributed to the modulation of osteogenic differentiation of endogenous mesenchymal stem cells (MSCs) and the inhibition of osteoclastogenesis, accompanying with the promotion of the angiogenic activity of endothelial cells (ECs).

Tailoring the Nanostructured Surfaces of Hydroxyapatite Bioceramics to Promote Protein Adsorption, Osteoblast Growth, and Osteogenic Differentiation

To promote and understand the biological responses of the implant via nanostructured surface design is essential for the development of bioactive bone implants. However, the control of the surface topography of the bioceramics in nanoscale is a big challenge because of their brittle property. Herein, the hydroxyapatite (HAp) bioceramics with distinct nanostructured topographies were fabricated via hydrothermal treatment using α-tricalcium phosphate ceramic as hard-template under different reaction conditions. HAp bioceramics with nanosheet, nanorod and micro-nanohybrid structured surface in macroscopical size were obtained by controlling the composition of the reaction media. Comparing with the traditional sample with flat and dense surface, the fabricated HAp bioceramics with hierarchical 3D micro-nanotextured surfaces possessed higher specific surface area, which selectively enhanced adsorption of specific proteins including Fn and Vn in plasma, and stimulated osteoblast adhesion, growth, and osoteogenic differentiation. In particular, the biomimetic features of the hierarchical micro-nanohybrid surface resulted in the best ability for simultaneous enhancement of protein adsorption, osteoblast proliferation, and differentiation. The results suggest that the hierarchical micro-nanohybrid topography might be one of the critical factors to be considered in the design of functional bone grafts.

Effect of nano-structured bioceramic surface on osteogenic differentiation of adipose derived stem cells

Tissue engineering strategies to construct vascularized bone grafts potentially revolutionize the treatment of massive bone loss. The surface topography of the grafts plays critical roles on bone regeneration, while adipose derived stem cells (ASCs) are known for their capability to promote osteogenesis and angiogenesis when applied to bone defects. In the present study, the effects of hydroxyapatite (HAp) bioceramic scaffolds with nanosheet, nanorod, and micro-nano-hybrid (the hybrid of nanorod and microrod) surface topographies on attachment, proliferation and osteogenic differentiation, as well as the expression of angiogenic factors of rat ASCs were systematically investigated. The results showed that the HAp bioceramic scaffolds with the micro-/nano-topography surfaces significantly enhanced cell attachment and viability, alkaline phosphatase (ALP) activity, and mRNA expression levels of osteogenic markers and angiogenic factors of ASCs. More importantly, the biomimetic feature of the hierarchical micro-nano-hybrid surface topography showed the highest stimulatory effect. The activation in Akt signaling pathway was observed in ASCs cultured on HAp bioceramics with nanorod, and micro-nano-hybrid surface topographies. Moreover, these induction effects could be repressed by Akt signaling pathway inhibitor LY294002. Finally, the in vivo bone regeneration results of rat critical-sized calvarial defect models confirmed that the combination of the micro-nano-hybrid surface and ASCs could significantly enhance both osteogenesis and angiogenesis as compared with the control HAp bioceramic scaffold with traditional smooth surface. Our results suggest that HAp bioceramic scaffolds with micro-nano-hybrid surface can act as cell carrier for ASCs, and consequently combine with ASCs to construct vascularized tissue-engineered bone.

Vertical alveolar ridge augmentation with β-tricalcium phosphate and autologous osteoblasts in canine mandible

A tissue-engineered bone has become a viable alternative to autologous bone for bone augmentation in atrophy alveolar ridge. The aim of the present study was to evaluate porous beta-tricalcium phosphate (beta-TCP) combined with autologous osteoblasts to augment edentulous alveolar ridge in a canine model. Autologous osteoblasts were expanded and combined with beta-TCP scaffold to fabricate a tissue-engineered bone. 12 bilateral alveolar ridge augmentation surgeries were carried out in 6 beagle dogs with the following 3 groups: beta-TCP/osteoblasts, beta-TCP alone and autogenous iliac bone control (n=4 per group). Sequential fluorescent labeling and radiographs were used to compare new bone formation and mineralization in each group. 24 weeks later, animals were sacrificed and non-decalcified and decalcified sections were evaluated histologically and histomorphometrically. Results indicated that the tissue-engineered bone dramatically enhanced new bone formation and mineralization, increase the new bone area, and maintain the height and thickness of the augmented alveolar ridge when compared with beta-TCP alone group. More importantly, the tissue-engineered bone achieved an elevated bone height and thickness comparable to that of autogenous iliac bone graft. This study demonstrated the potential of porous beta-TCP as a substrate for autogenous osteoblasts in bone tissue engineering for alveolar ridge augmentation.

EGF signalling pathway regulates colon cancer stem cell proliferation and apoptosis

Cancer stem cells (CSCs) compose a subpopulation of cells within a tumour that can self‐renew and proliferate. Growth factors such as epidermal growth factor (EGF) and basic fibroblast growth factor (b‐FGF) promote cancer stem cell proliferation in many solid tumours. This study assesses whether EGF, bFGF and IGF signalling pathways are essential for colon CSC proliferation and self‐renewal.

Enhanced osteogenesis through nano-structured surface design of macroporous hydroxyapatite bioceramic scaffolds via activation of ERK and p38 MAPK signaling pathways

The design of the three-dimensional (3D) porous structures and surface morphological/topographies of implants is considered as a novel approach to enhance the bioactivity and osteoinductive ability in the field of bone regeneration. In the present study, highly interconnective macroporous hydroxyapatite (HAp) bioceramic scaffolds with nanosheet, nanorod and micro-nano-hybrid (the hybrid of nanorod and microrod) surface topographies were fabricated using α-tricalcium phosphate (α-TCP) ceramic scaffolds as precursors, through regulation of the hydrothermal reaction conditions. Moreover, the effects of these three surface topographies on attachment, proliferation and osteogenic differentiation of rat bone marrow stromal cells (bMSCs) as well as the related mechanisms were systematically investigated. The results showed that the HAp bioceramics with these micro-/nano-topography surfaces significantly enhanced cell attachment, cell viability, alkaline phosphatase (ALP) activity, and mRNA expression levels of osteoblast-related genes of bMSCs. In particular, the biomimetic feature of the micro-nano-hybrid topography surface possessed the highest stimulatory effect. The activation in extracellular signal-related kinases (ERK), and p38 mitogen-activated protein kinase (MAPK) signaling pathways was observed in bMSCs cultured on HAp bioceramics with micro-/nano-topography surfaces especially for the micro-nano-hybrid topography surface, and these enhancement effects could be blocked by ERK inhibitor PD98059, and P38 inhibitor SB203580, respectively. Moreover, the in vivo bone regeneration results of rat critical-sized calvarial defect models confirmed that macroporous HAp bioceramics with these micro-/nano-topography surfaces could promote new bone formation and mineralization as compared with the control HAp bioceramic with traditional smooth surfaces, while the scaffold with a micro-nano-hybrid surface could achieve a better effect. The study suggests that the hierarchical micro-nano-hybrid topography shows immense potential in improving the clinical performance of macroporous HAp bioceramics.

Combination of β‐TCP and BMP‐2 gene‐modified bMSCs to heal critical size mandibular defects in rats

OBJECTIVE To investigate the effects of mandibular defects repaired by a tissue engineered bone complex with beta-tricalcium phosphate (beta-TCP) and bone morphogenic protein-2 (BMP-2) gene-modified bone marrow stromal cells (bMSCs). MATERIALS AND METHODS bMSCs derived from Fisher 344 rats were cultured and transduced with adenovirus AdBMP-2, AdEGFP gene in vitro. Osteogenic differentiation of bMSCs was determined by alkaline phosphatase staining, von Kossa assay and reverse transcription-polymerase chain reaction. Gene transduced or untransduced bMSCs were seeded on beta-TCP scaffolds to repair mandibular full thickness defects with a diameter of 5 mm. Eight weeks post-operation, X-ray examination, micro-computerized tomography and histological and histomorphological analysis were used to evaluate the bone healing effects. RESULTS Alkaline phosphatase staining and mineralized nodules formation were more pronounced in AdBMP-2 group 14 days after gene transduction when compared with that of AdEGFP or untransduced group. The mRNA expression of osteopontin and osteocalcin also significantly increased 9 days after AdBMP-2 gene transduction. Mandibular defects were successfully repaired with AdBMP-2-transduced bMSCs/beta-TCP constructs. The percentage of new bone formation in AdBMP-2 group was significantly higher than that of other control groups. CONCLUSIONS Bone morphogenic protein-2 regional gene therapy together with beta-TCP scaffold could be used to promote mandibular repairing and bone regeneration.

Systematic evaluation of a tissue-engineered bone for maxillary sinus augmentation in large animal canine model.

The objective of this study is to systematically evaluate the effects of a tissue-engineered bone complex for maxillary sinus augmentation in a canine model. Twelve sinus floor augmentation surgeries in 6 animals were performed bilaterally and randomly repaired with the following 3 groups of grafts: group A consisted of tissue-engineered osteoblasts/beta-TCP complex (n=4); group B consisted of beta-TCP alone (n=4); group C consisted of autogenous bone obtained from iliac crest as a positive control (n=4). All dogs had uneventful healings following the surgery. Sequential polychrome fluorescent labeling, maxillofacial CT, microhardness tests, as well as histological and histomorphometric analyses indicated that the tissue-engineered osteoblasts/beta-TCP complex dramatically promoted bone formation and mineralization and maximally maintained the height and volume of elevated maxillary sinus. By comparison, both control groups of beta-TCP or autologous iliac bone showed considerable resorption and replacement by fibrous or fatty tissue. We thus conclude that beta-TCP alone could barely maintain the height and volume of the elevated sinus floor, and that the transplantation of autogenous osteoblasts on beta-TCP could promote earlier bone formation and mineralization, maximally maintain height, volume and increase the compressive strength of augmented maxillary sinus. This tissue engineered bone complex might be a better alternative to autologous bone for the clinical edentulous maxillary sinus augmentation.

Akermanite bioceramics promote osteogenesis, angiogenesis and suppress osteoclastogenesis for osteoporotic bone regeneration.

It is a big challenge for bone healing under osteoporotic pathological condition with impaired angiogenesis, osteogenesis and remodeling. In the present study, the effect of Ca, Mg, Si containing akermanite bioceramics (Ca2MgSi2O7) extract on cell proliferation, osteogenic differentiation and angiogenic factor expression of BMSCs derived from ovariectomized rats (BMSCs-OVX) as well as the expression of osteoclastogenic factors was evaluated. The results showed that akermanite could enhance cell proliferation, ALP activity, expression of Runx2, BMP-2, BSP, OPN, OCN, OPG and angiogenic factors including VEGF and ANG-1. Meanwhile, akermanite could repress expression of osteoclastogenic factors including RANKL and TNF-α. Moreover, akermanite could activate ERK, P38, AKT and STAT3 signaling pathways, while crosstalk among these signaling pathways was evident. More importantly, the effect of akermanite extract on RANKL-induced osteoclastogenesis was evaluated by TRAP staining and real-time PCR assay. The results showed that akermanite could suppress osteoclast formation and expression of TRAP, cathepsin K and NFATc1. The in vivo experiments revealed that akermanite bioceramics dramatically stimulated osteogenesis and angiogenesis in an OVX rat critical-sized calvarial defect model. All these results suggest that akermanite bioceramics with the effects of Mg and Si ions on osteogenesis, angiogenesis and osteoclastogenesis are promising biomaterials for osteoporotic bone regeneration.

Icariin induces osteogenic differentiation of bone mesenchymal stem cells in a MAPK-dependent manner.

Icariin, a flavonoid isolated from Epimedium pubescens, has previously been identified to exert beneficial effects on preventing bone loss and promoting bone regeneration. However, molecular mechanisms for its anabolic action have, up to now, remained largely unknown.