Enhancing soft tissue integration and preventing implant-associated infection play a crucial role in improving the long-term success of percutaneous implants. Microgroove pattern modification of titanium implants has been proven to be effective for enhancing soft tissue integration. However, single microgroove pattern modification may not improve the antibacterial activity of implants, posing a threat of bacterial infection at the percutaneous site of the implant. While hybrid magnesium/zinc-metal organic framework (Mg/Zn-MOF74) coating exhibits excellent antibacterial ability due to its degradation which generates 2,5-dihydroxyterephthalic acid (DTHA), Zn2+ and Mg2+. Therefore, we propose a surface modification method that combines microgroove pattern modification with the hybrid Mg/Zn-MOF74 coating for titanium implants. We expect to simultaneously utilize microgroove pattern modification for enhancing soft tissue integration and hybrid Mg/Zn-MOF74 coating for improve the antibacterial activity. Both in vitro and in vivo experiments have demonstrated that the combination of microgroove pattern and hybrid Mg/Zn-MOF74 coating of Ti implants can promote fibroblast migration, adhesion, and myogenic differentiation. Meanwhile, this surface modification exhibits promising antibacterial activity, and could inhibit the migration of epithelial cell. These properties not only facilitate the formation of a biological seal, but also reduce the incidence of implant-associated infection. Overall, the microgroove pattern modification combined with hybrid Mg/Zn-MOF74 coating has great potential for the surface modification of Ti implants to promote soft-tissue integration and prevent implant-associated infections.

Given afferent functions, sensory nerves have recently been found to exert efferent effects and directly alter organ physiology. Additionally, several studies have highlighted the indirect but crucial role of sensory nerves in the regulation of the physiological function of osteoclasts. Nonetheless, evidence regarding the direct sensory nerve efferent influence on osteoclasts is lacking. In the current study, we found that high levels of efferent signals were transported directly from the sensory nerves into osteoclasts. Furthermore, sensory hypersensitivity significantly increased osteoclastic bone resorption, and sensory neurons (SNs) directly promoted osteoclastogenesis in an in vitro coculture system. Moreover, we screened a novel neuropeptide, Cyp40, using an isobaric tag for relative and absolute quantitation (iTRAQ). We observed that Cyp40 is the efferent signal from sensory nerves, and it plays a critical role in osteoclastogenesis via the aryl hydrocarbon receptor (AhR)-Ras/Raf-p-Erk-NFATc1 pathway. These findings revealed a novel mechanism regarding the influence of sensory nerves on bone regulation, i.e., a direct promoting effect on osteoclastogenesis by the secretion of Cyp40. Therefore, inhibiting Cyp40 could serve as a strategy to improve bone quality in osteoporosis and promote bone repair after bone injury.

Exploitation of advanced methotrexate (MTX) delivery with nanocomposites has important clinical application value. Poloxamer 188 micelle and layered double hydroxide loaded with MTX (LDH-MTX) by exfoliation reassembling were used to prepare LDH-MTX-poloxamer 188 nanocomposites with good dispersibility and efficient cellular uptake for controlled drug delivery. The LDH-MTX-poloxamer 188 nanocomposites with sphere-like morphology, of which the average hydrodynamic diameter was <100 nm, were shown to have better dispersion state than naked LDH-MTX. Importantly, the LDH-MTX-poloxamer 188 nanocomposites could achieve significant sustained drug release and have obvious pH dependent responsive release ability. In addition, these nanocomposites also exhibited long-term and excellent in vitro antitumor efficacy as opposed to pure MTX or LDH-MTX as evident from cell viability. More interestingly, compared to pure FITC used to simulate MTX, LDH nanocomposites labeled with FITC were considered to have better cell adhesion through cell uptake. Therefore, the studied nanocomposites of LDH-MTX-poloxamer 188 can be further used as a new advanced MTX delivery nanovehicles with desired properties in future therapeutic aspects.

Three-dimensional (3D) bioprinting is an extremely convenient biofabrication technique for creating biomimetic tissue-engineered bone constructs and has promising applications in regenerative medicine. However, existing bioinks have shown low mechanical strength, poor osteoinductive ability, and lacking a suitable microenvironment for laden cells. Nanosilicate (nSi) has shown to be a promising biomaterial, due to its unique properties such as excellent biocompatibility, degrade into nontoxic products, and with osteoinductive properties, which has been used in bone bioprinting. However, the long term bone healing effects and associating risks, if any, of using nSi in tissue engineering bone scaffolds in vivo are unclear and require a more thorough assessment prior to practical use. Hence, a functional and biomimetic nanocomposite bioink composed of rat bone marrow mesenchymal stem cells (rBMSCs), nSi, gelatin and alginate for the 3D bioprinting of tissue-engineered bone constructs is firstly demonstrated, mimicking the structure of extracellular matrix, to create a conducive microenvironment for encapsulated cells. It is shown that the addition of nSi significantly increases the printability and mechanical strength of fabricated human-scale tissue or organ structures (up to 15 mm height) and induces osteogenic differentiation of the encapsulated rBMSCs in the absence of in vitro osteoinductive factors. A systematic in vivo research of the biomimetic nanocomposite bioink scaffolds is further demonstrated in a rat critical-size (8 mm) bone defect-repair model. The in vivo results demonstrate that the 3D bioprinted nanocomposite scaffolds can significantly promote the bone healing of the rat calvarial defects compared to other scaffolds without nSi or cells, and show rarely side effects on the recipients. Given the above advantageous properties, the 3D bioprinted nanocomposite scaffolds can greatly accelerate the bone healing in critical bone defects, thus providing a clinical potential candidate for orthopedic applications.

Objective To investigate the effects of fibroblast growth factor 2 (FGF-2) on the cytoskeleton and morphology of rat bone marrow mesenchymal stem cells (BMSCs). Methods Morphological and cytoskeleton changes of BMSCs were observed by scanning electron microscopy and rhodamine-phalloidin staining in TranswellTM co-culture system of rat vascular endothelial cells (RAECs) and BMSCs. The content of FGF-2 in cell supernatants were detected by ELISA, and the mRNA expression of FGF-2 in both conventional and co-cultured cells were evaluated by real-time quantitative PCR. NVP-BGJ398, an inhibitor of FGF-2 receptor was added into the co-culture system to block FGF-2 signal and its effect on BMSCs skeleton was observed. Recombinant FGF-2 was supplemented into the conventional medium of BMSCs to further verify the effect of exogenous FGF-2. Results After co-cultured with RAECs, BMSCs gradually stretched, contracted and formed a large number of filopodia. The content of FGF-2 increased in the co-culture system and was mainly secreted by RAECs. Cytoskeleton remodeling of BMSCs was significantly blocked by the inhibitor of FGF-2 receptor and the cells were mostly short spindle-shaped and arranged in a spiral pattern. Exogenous FGF-2 promoted the contraction and edge stretching of BMSCs, forming filopodia with staggered distribution. Conclusion FGF-2 secreted by RAECs induces cytoskeletal remodeling of BMSCs.

Background and aim As a newly emerging three-dimensional (3D) printing technology, low-temperature robocasting can be used to fabricate geometrically complex ceramic scaffolds at low temperatures. Here, we aimed to fabricate 3D printed ceramic scaffolds composed of nano-biphasic calcium phosphate (BCP), polyvinyl alcohol (PVA), and platelet-rich fibrin (PRF) at a low temperature without the addition of toxic chemicals. Methods Corresponding nonprinted scaffolds were prepared using a freeze-drying method. Compared with the nonprinted scaffolds, the printed scaffolds had specific shapes and well-connected internal structures. Results The incorporation of PRF enabled both the sustained release of bioactive factors from the scaffolds and improved biocompatibility and biological activity toward bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the printed BCP/PVA/PRF scaffolds promoted significantly better BMSC adhesion, proliferation, and osteogenic differentiation in vitro than the printed BCP/PVA scaffolds. In vivo, the printed BCP/PVA/PRF scaffolds induced a greater extent of appropriate bone formation than the printed BCP/PVA scaffolds and nonprinted scaffolds in a critical-size segmental bone defect model in rabbits. Conclusion These experiments indicate that low-temperature robocasting could potentially be used to fabricate 3D printed BCP/PVA/PRF scaffolds with desired shapes and internal structures and incorporated bioactive factors to enhance the repair of segmental bone defects.

The prevascularization of tissue-engineered bone grafts (TEBGs) has been shown to accelerate capillary vessel ingrowth in bone defect remodeling and to enhance new bone formation. However, the exact mechanisms behind this positive effect remain unknown. Here, we report that basic fibroblast growth factor (FGF2)-Ras homolog gene family member A (RhoA)/Rho-associated protein kinase (ROCK) signaling functions as a molecular switch to regulate the lineage fate of bone mesenchymal stem cells (BMSCs) and that prevascularization promotes the cell fate switch, which contributes to increased bone regeneration with the use of prevascularized TEBGs compared with control TEBGs. Prevascularized TEBGs enhanced the in vivo endothelial differentiation of BMSCs by inhibiting RhoA/ROCK signaling. In vitro data more clearly showed that BMSCs differentiated into von Willebrand factor (vWF)-positive endothelial cells, and FGF2-induced inhibition of RhoA/ROCK signaling played a key role. Our novel findings uncovered a new mechanism that stimulates the increased vascularization of engineered bone and enhanced regeneration by promoting the endothelial differentiation of BMSCs implanted in TEBGs. These results offer a new molecular target to regulate TEBG-induced bone regeneration.

Vascularization is one of the most important processes in tissue-engineered bone graft (TEBG)-mediated regeneration of large segmental bone defects. We previously showed that prevascularization of TEBGs promoted capillary vessel formation within the defected site and accelerated new bone formation. However, the precise mechanisms and contribution of endogenous cells were not explored.

Objective To systematically evaluate the biomechanical recovery of drilled holes in the femur in SD rats.Methods Eighteen female SD rats were randomized into 3 even groups (n =6).Models of 2-mm drilled holes in bilateral femurs were established in groups A and B with 2 holes on each side while no drilling was performed in group C.Samples were harvested in group A at postoperative 4 weeks,in group B at postoperative 8 weeks while at both 4 and 8 weeks in group C.The samples were evaluated in terms of linear elasticity (compression test),viscoelasticity (relaxation and creep tests) and durability (fatigue failure test).Micro-CT scan was performed to measure the bone volume fraction (BV/TV) and bone mineral density (BMD) of new bone.Sirus red staining was performed to measure regeneration of type Ⅰ collagen of new bone.Results The elasticity modulus,maximum load,compression strength and conditional yield limit in groups A were significantly lower than those in group B which were also significantly lower than those in group C (P ＜ 0.05).At 7,200 s,the relaxation (14.56 ±0.69 MPa) and creep variation (11.37％ ± 0.70％) in group A were significantly higher than those in group B (11.06 0.63 MPa and 8.98％ ± 0.40％) which were also significantly higher than those in group C (6.99 ±0.56 MPa and 5.10％ ±0.23％) (P ＜ 0.05).At the constant amplitude loads from 20 N to 200 N,from 20 N to 300 N and from 20 N to 400 N,the recycling numbers in group A (6,044.3 ±879.7,4,093.3 ±628.5 and 1,919.3 ±847.5) were significantly lower than those in group B (10,192.3 ± 1,109.1,6,750.6 ± 818.0 and 3,376.6 ± 671.3) which were also significantly lower than those in group C (28,068.3 ±2,702.6,11,788.3 ± 1,141.6 and 5,296.3 ± 735.0) (P ＜ 0.05).By micro-CT scan,the BVT and BMD in group A were significantly lower than those in group B which were also significantly lower than those in group C (P ＜ 0.05).The sirus red staining showed the type Ⅰ collagen in the bone defect area was completely regenerated in group B.Conclusion Systematic biomechanical measurements may actually detect the characteristics of biomechanical recovery of bone holes in SD rats,enriching the basic research on the bone damage repairing progress.

Massive bone defects are a challenge in orthopaedic research. Defective regeneration leads to bone atrophy, non-union of bone, and physical morbidity. Large animals are important models, however, production costs are high, nursing is complex, and evaluation methods are limited. A suitable laboratory animal model is required to explore the underlying molecular mechanism and cellular process of bone tissue engineering. We designed a stainless steel plate with 8 holes; the middle 2 holes were used as a guide to create a standardized critical size defect in the femur of anaesthetized rats. The plate was fixed to the bone using 6 screws, serving as an inner fixed bracket to secure a tricalcium phosphate implant seeded with green fluorescent protein-positive rat bone marrow mesenchymal stem cells within the defect. In some animals, we also grafted a vessel bundle into the lateral side of the implant, to promote vascularized bone tissue engineering. X-ray, microcomputed tomography, and histological analyses demonstrated the stainless steel plate resulted in a stable large segmental defect model in the rat femur. Vascularization significantly increased bone formation and implant degradation. Moreover, survival and expansion of green fluorescent protein-positive seeded cells could be clearly monitored in vivo at 1, 4, and 8 weeks postoperation via fluorescent microscopy. This standardized large segmental defect model in a small animal may help to advance the study of bone tissue engineering. Furthermore, availability of antibodies and genetically modified rats could help to dissect the precise cellular and molecular mechanisms of bone repair.

Our previous studies found that sensory nerve tracts implanted in tissue-engineered bone (TEB) could result in better osteogenesis. To explore the mechanism of the sensory nerve promoting osteogenesis in TEB in vitro, a transwell coculture experiment was designed between dorsal root ganglion (DRG) cells and bone marrow mesenchymal stem cells (BMSCs). BMSC proliferation was determined by CCK8 assay, and osteo-, chondro-, and adipogenic differentiation were assessed by alizarin red, alcian blue, and oil red staining. We found that the proliferation and multipotent differentiation of BMSCs were all enhanced in the coculture group compared to the BMSCs group. Crystal violet staining showed that the clone-forming ability of BMSCs in the coculture group was also enhanced and mRNA levels of Sox2, Nanog, and Oct4 were significantly upregulated in the coculture group. Moreover, the autophagy level of BMSCs, regulating their stemness, was promoted in the coculture group, mediated by the AMPK/mTOR pathway. In addition, AMPK inhibitor compound C could significantly downregulate the protein expression of LC3 and the mRNA level of stemness genes in the coculture group. Finally, we found that the NK1 receptor antagonist, aprepitant, could partly block this effect, which indicated that substance P played an important role in the effect. Together, we conclude that DRG could maintain the stemness of BMSCs by enhancing autophagy through the AMPK/mTOR pathway in a transwell coculture system, which may help explain the better osteogenesis after implantation of the sensory nerve into TEB.

CD31hiEmcnhi vessels were a subtype of vessels in the murine skeletal system, with high levels of platelet and endothelial cell adhesion molecule-1 (PECAM-1/CD31) and endomucin (Emcn). They were reported coupling angiogenesis and osteogenesis during bone development. We investigated the distribution of these vessels in rat tibiae and their temporal and spatial distribution during the bone defect repair process to improve our understanding of the importance of these vessels. We confirmed that CD31hiEmcnhi vessels were specially distributed around the trabecular bones near metaphysis and endosteum in rat tibiae. At 3 days post bone injury, CD31hiEmcnhi vessels proliferated and were extensively distributed across the entire repair area. At 7 and 14 days post-injury, these vessels decreased but were specially distributed around the growing trabecular bones near the frontier growth area, suggesting that these vessels support new bone formation. The distribution of CD31hiEmcnhi vessels and the transcriptions of Hif - 1α and VEGFA , as well as BMP2 and Osterix decreased at 7 and 14 days post-injury under osteoporotic conditions, in combination with insufficient osteogenesis. Our research is of great significance to help understand the important role of CD31hiEmcnhi vessels in supporting new trabecular bones formation during bone defect repair process.

Objective To investigate the effect of sensory and motor nerve homogenates at different concentrations on the proliferation and osteogenesis differentiation of bone marrow mesenchymal stem cells (BMSCs) in rats.Methods The saphenous nerve and the muscle branch of the sciatic nerve in rats were extracted surgically as sensory and motor nerve tissues,respectively.The primary nerve homogenates (10 mg/mL) were prepared as per 10 mg tissue with 1 mL osteoblast inducing conditional media,and 10 times diluted after filtration purification to prepare sensory and motor nerve homogenates at concentration gradients of 1.0,0.1,0.01,0.001 and 0.0001 mg/mL.Cultivation GFP ± rat pups BMSCs in vitro were trained to P3 generation.The experiment was carried out in 3 groups.The sensory and motor nerve homogenates of 500 μL at the above 6 concentration gradients were added during cultivation respectively in the sensory nerve group (n =18) and the motor nerve group(n =18) while 500 μL of osteoblast inducing conditional media was added in the control group(n =3).Cell proliferation quantity detection and alkaline phosphatase (ALP) staining were used to assess the proliferation and differentiation of BMSCs after 14 days.Results According to the results of CCK-8,the cellular absorbance values at concentrations of 1.0 and 0.1 mg/mL homogenate in the sensory nerve group (1.957 ±0.065 and 1.751±0.073) were significantly greater than in the control group (1.145±0.087) while the cellular absorbance value at concentration of 10.0 mg/mL homogenate in the motor nerve group (0.304 ± 0.619) was significandy smaller than in the control group (1.145 ± 0.087) (P ＜ 0.05).According to the ALP staining,the amounts of cellular calcium nodules in the sensory and motor nerve groups (2.667 ± 0.816 and 3.000 ± 0.632,respectively) were significantly smaller than in the control group (11.833 ± 1.471) (P ＜ 0.05).Conclusion Sensory nerve homogenate is different from motor nerve homogenate in that it may promote proliferation of BMSCs and inhibit osteogenesis differentiation of BMSCs in a certain rage of concentrations.

Objective To investigate the effect of prevascularized tissue-engineered bone graft on regeneration of femoral bone defects in rats.Methods Models of femoral bone defect were created at the bilateral hind limbs of 20 healthy female 10 week-old rats which were divided into 2 even groups randomly (n =10).In group A,conventional tissue-engineered bone grafts were transplanted into the femoral bone defects;in group B,tissue-engineered bone grafts and vascular bundles were implanted into the femoral defects.At 1,4 and 8 weeks after operation,3 rats were sacrificed each time in each group to harvest samples.The remaining one in each group served as a spare animal.Regeneration of bone defects and degradation of scaffolds were assessed by radiologic modality and hematein eosin staining.Results At week 1,the new bone ratio (BV/TV) was 5.47％ ± 1.90％ in group A and 8.49％ ± 1.26％ in group B,showing no significant difference (P ＞ 0.05);at weeks 4 & 8,the BV/TV were 17.54％ ±2.04％ and 39.73％ ± 4.01％ in group A,significantly lower than those in group B (25.32％ ± 2.15％ and 53.22％ ± 2.94％) (P ＜ 0.05).At weeks 1 & 4,the scaffold degradation ratios (RSV/SV) were 97.33％ ± 2.52％ and 80.60％ ±4.00％,showing no significant differences from those in group B (95.67％ ±3.51％ and 75.22％ ±6.20％) (P ＞ 0.05).At week 8,the scaffold degradation ratio in group A (65.46％ ±4.51％) was significantly higher than that in group B (50.19％ ±4.91％) (P ＜ 0.05).At week 8,hematein eosin staining showed better integration of scaffolds with the femur,faster degradation of the interior scaffolds and greater osteogenetic activity in group B.Conclusion Prevascularization of tissue-engineered bone graft may increase new bone volume and scaffold degradation rate,promoting repair of femoral bone defects in rats.

In order to establish the best procedure to store the femur samples from the biomechanical viewpoint,we compared the effects of different storage methods on the mechanical properties of mouse femurs.We obtained femurs surgically from twenty C57BL/6Jfemale mice,12 weeks old,and randomly divided them into 5groups,i.e.fresh control group,4% paraformaldehyde fixation group,4℃storage group,-20℃storage group and-80℃storage group,respectively,with five mice in each group.For the three low-temperature storage groups,each group was stored for 1week,2months,6months at their respective temperatures.After rewarming,three-point bending test was performed to test the load and deflection changes.The results showed that both the elastic modulus and deflection decreased significantly in the 4% paraformaldehyde group.The maximum load and elastic modulus of the samples in the 4 ℃ group after one week storage was significantly reduced;The mechanical properties were close to the fresh control group in the-20℃ group stored for 2months but the maximum load was also reduced after 6months.However,mechanical properties,such as elastic load,maximum load and elastic modulus,were not changed obviously in the-80 ℃ storage group.Accordingly,-80 ℃ cryopreservation had little influence on the mechanical properties of bone tissues,which proved that the temperature-80 ℃is a suitable one for long-term preservation.

Viral protein glycosylation is very common in nature , but it is ignored in a long time .Due to the development of the related technologies , the research of protein glycosylation gets a rapid development in recent years .Now we know that virus glycoprotein closlely correlates with virus recongnition , cell fusion and immune response .This review is to summarize the types of viral protein glycosylation , knowledge about the roles of virus glycoprotein and how we use glycosylation .