Treatment of Scaphoid Nonunion: Pedicled Vascularized Bone Graft vs. Traditional Bone Graft

The clinical results of the application of pedicled vascularized bone graft （VBG） from Lister＇s tubercle vs. traditional bone graft （TBG） were evaluated and compared. Thirteen cases of symptomatic scaphoid nonunion were treated between January 2011 and December 2012, including 7 cases subject to VBG and the rest 6 cases to TBG, respectively. Outcomes were assessed by modified Mayo wrist score system. All cases were followed up for an average period of 3.5 months after opera- tion. The results showed that total scores in VBG group were 86.4i9.4 after operation with excellent result in 4 cases, good in 2 and acceptable in one, and those in TBG group were 71.7±9.3 after operation with good result in 2 cases, acceptable in 3 and disappointing in one. Total score of wrist function was significantly improved in VBG group as compared with TBG group （P〈0.05）. Our study suggests that VBG method is more effective for treating scaphoid nonunion than TBG method.

ETV2 regulating PHD2-HIF-1αaxis controls metabolism reprogramming promotes vascularized bone regeneration

The synchronized development of mineralized bone and blood vessels is a fundamental requirement for successful bone tissue regeneration.Adequate energy production forms the cornerstone supporting new bone formation.ETS variant 2(ETV2)has been identified as a transcription factor that promotes energy metabolism reprogramming and facilitates the coordination between osteogenesis and angiogenesis.In vitro molecular experiments have demonstrated that ETV2 enhances osteogenic differentiation of dental pulp stem cells(DPSCs)by regulating the ETV2-prolyl hydroxylase 2(PHD2)-hypoxia-inducible factor-1α(HIF-1α)-vascular endothelial growth factor A(VEGFA)axis.Notably,ETV2 achieves the rapid reprogramming of energy metabolism by simultaneously accelerating mitochondrial aerobic respiration and glycolysis,thus fulfilling the energy requirements essential to expedite osteogenic differentiation.Furthermore,decreasedα-ketoglutarate release from ETV2-modified DPSCs contributes to microcirculation reconstruction.Additionally,we engineered hydroxyapatite/chitosan microspheres(HA/CS MS)with biomimetic nanostructures to facilitate multiple ETV2-DPSC functions and further enhanced the osteogenic differentiation.Animal experiments have validated the synergistic effect of ETV2-modified DPSCs and HA/CS MS in promoting the critical-size bone defect regeneration.In summary,this study offers a novel treatment approach for vascularized bone tissue regeneration that relies on energy metabolism activation and the maintenance of a stable local hypoxia signaling state.

Black phosphorus nanosheets-enabled DNA hydrogel integrating 3D-printed scaffold for promoting vascularized bone regeneration

The classical 3D-printed scaffolds have attracted enormous interests in bone regeneration due to the customized structural and mechanical adaptability to bone defects.However,the pristine scaffolds still suffer from the absence of dynamic and bioactive microenvironment that is analogous to natural extracellular matrix(ECM)to regulate cell behaviour and promote tissue regeneration.To address this challenge,we develop a black phosphorus nanosheets-enabled dynamic DNA hydrogel to integrate with 3D-printed scaffold to build a bioactive gel-scaffold construct to achieve enhanced angiogenesis and bone regeneration.The black phosphorus nanosheets reinforce the mechanical strength of dynamic self-healable hydrogel and endow the gel-scaffold construct with preserved protein binding to achieve sustainable delivery of growth factor.We further explore the effects of this activated construct on both human umbilical vein endothelial cells(HUVECs)and mesenchymal stem cells(MSCs)as well as in a critical-sized rat cranial defect model.The results confirm that the gel-scaffold construct is able to promote the growth of mature blood vessels as well as induce osteogenesis to promote new bone formation,indicating that the strategy of nano-enabled dynamic hydrogel integrated with 3D-printed scaffold holds great promise for bone tissue engineering.

Bioinspired porous microspheres for sustained hypoxic exosomes release and vascularized bone regeneration

Exosomes derived from mesenchymal stem cells(MSCs)have demonstrated regenerative potential for cell-free bone tissue engineering,nevertheless,certain challenges,including the confined therapeutic potency of exosomes and ineffective delivery method,are still persisted.Here,we confirmed that hypoxic precondition could induce enhanced secretion of exosomes from stem cells from human exfoliated deciduous teeth(SHEDs)via comprehensive proteomics analysis,and the corresponding hypoxic exosomes(H-Exo)exhibited superior potential in promoting cellular angiogenesis and osteogenesis via the significant up-regulation in focal adhesion,VEGF signaling pathway,and thyroid hormone synthesis.Then,we developed a platform technology enabling the effective delivery of hypoxic exosomes with sustained release kinetics to irregular-shaped bone defects via injection.This platform is based on a simple adsorbing technique,where exosomes are adsorbed onto the surface of injectable porous poly(lactide-co-glycolide)(PLGA)microspheres with bioinspired polydopamine(PDA)coating(PMS-PDA microspheres).The PMS-PDA microspheres could effectively adsorb exosomes,show sustained release of H-Exo for 21 days with high bioactivity,and induce vascularized bone regeneration in 5-mm rat calvarial defect.These findings indicate that the hypoxic precondition and PMS-PDA porous microsphere-based exosome delivery are efficient in inducing tissue regeneration,hence facilitating the clinical translation of exosome-based therapy.

Fabrication of a bio-instructive scaffold conferred with a favorable microenvironment allowing for superior implant osseointegration and accelerated in situ vascularized bone regeneration via type H vessel formation

The potential translation of bio-inert polymer scaffolds as bone substitutes is limited by the lack of neovascularization upon implantation and subsequently diminished ingrowth of host bone,most likely resulted from the inability to replicate appropriate endogenous crosstalk between cells.Human umbilical vein endothelial cell-derived decellularized extracellular matrix(HdECM),which contains a collection of angiocrine biomolecules,has recently been demonstrated to mediate endothelial cells(ECs)-osteoprogenitors(OPs)crosstalk.We employed the HdECM to create a PCL(polycaprolactone)/fibrin/HdECM(PFE)hybrid scaffold.We hypothesized PFE scaffold could reconstitute a bio-instructive microenvironment that reintroduces the crosstalk,resulting in vascularized bone regeneration.Following implantation in a rat femoral bone defect,the PFE scaffold demonstrated early vascular infiltration and enhanced bone regeneration by microangiography(μ-AG)and micro-computational tomography(μ-CT).Based on the immunofluorescence studies,PFE mediated the endogenous angiogenesis and osteogenesis with a substantial number of type H vessels and osteoprogenitors.In addition,superior osseointegration was observed by a direct host bone-PCL interface,which was likely attributed to the formation of type H vessels.The bio-instructive microenvironment created by our innovative PFE scaffold made possible superior osseointegration and type H vessel-related bone regeneration.It could become an alternative solution of improving the osseointegration of bone substitutes with the help of induced type H vessels,which could compensate for the inherent biological inertness of synthetic polymers.

The intragraft vascularized bone marrow component plays a critical role in tolerance induction after reconstructive transplantation

The role of the vascularized bone marrow component as a continuous source of donor-derived hematopoietic stem cells that facilitate tolerance induction of vascularized composite allografts is not completely understood.In this study,vascularized composite tissue allograft transplantation outcomes between recipients receiving either conventional bone marrow transplantation(CBMT)or vascularized bone marrow(VBM)transplantation from Balb/c(H2d)to C57BL/6(H2b)mice were compared.Either high-or low-dose CBMT(1.5×10^(8)or 3×10^(7)bone marrow cells,respectively)was applied.In addition,recipients were treated with costimulation blockade(1 mg anti-CD154 and 0.5 mg CTLA4Ig on postoperative days 0 and 2,respectively)and short-term rapamycin(3 mg/kg/day for the first posttransplant week and then every other day for another 3 weeks).Similar to high-dose conventional bone marrow transplantation,5/6 animals in the vascularized bone marrow group demonstrated long-term allograft survival(>120 days).In contrast,significantly shorter median survival was noted in the low-dose CBMT group(~64 days).Consistently high chimerism levels were observed in the VBM transplantation group.Notably,low levels of circulating CD4^(+)and CD8^(+)T cells and a higher ratio of Treg to Teff cells were maintained in VBM transplantation and high-dose CBMT recipients(>30 days)but not in low-dose VBM transplant recipients.Donor-specific hyporesponsiveness was shown in tolerant recipients in vitro.Removal of the vascularized bone marrow component after secondary donor-specific skin transplantation did not affect either primary allograft or secondary skin graft survival.

A baicalin-loaded coaxial nanofiber scaffold regulated inflammation and osteoclast differentiation for vascularized bone regeneration

We demonstrate a simple,effective and feasible method to address the shrinkage of Poly(lactic-co-glycolic acid)(PLGA)through a core-shell structure fiber strategy.The results revealed that introducing size-stable poly-caprolactone(PCL)as the core fiber significantly improved the PLGA-based fibrous scaffold’s dimensional maintenance.We further utilized fish collagen to modify the PLGA shell layer(PFC)of coaxial fibers and loaded baicalin(BA)into the PCL core layer(PCL-BA)to endow fibrous scaffold with more functional biological cues.The PFC/PCL-BA fibrous scaffold promoted the osteogenic differentiation of bone mesenchymal stem cells and stimulated the RAW264.7 cells to polarize into a pro-reparative phenotype.Importantly,the in vivo study demonstrated that the PFC/PCL-BA scaffold could regulate inflammation and osteoclast differentiation,favor neovascularization and bone formation.This work tactfully combined PLGA and PCL to establish a drug release platform based on the core-shell fibrous scaffold for vascularized bone regeneration.

Tackling bone loss of the lower extremity:vascularized bone grafting

Post-traumatic lower extremity bone loss in the setting of high-energy trauma can occur acutely as a result of an open fracture and surgical debridement,or secondarily as a result of nonunion or infection.Several techniques have been described in the literature for the management of these bony defects,including non-vascularized bone grafts,vascularized bone grafts and distraction osteogenesis.Herein,the authors review the role of vascularized bone grafts in the management of post-traumatic bone loss in the lower extremity.

A hierarchical vascularized engineered bone inspired by intramembranous ossification for mandibular regeneration

Mandibular defects caused by injuries,tumors,and infections are common and can severely affect mandibular function and the patient's appearance.However,mandible reconstruction with a mandibular bionic structure remains challenging.Inspired by the process of intramembranous ossification in mandibular development,a hierarchical vascularized engineered bone consisting of angiogenesis and osteogenesis modules has been produced.Moreover,the hierarchical vascular network and bone structure generated by these hierarchical vascularized engineered bone modules match the particular anatomical structure of the mandible.The ultra-tough polyion complex has been used as the basic scaffold for hierarchical vascularized engineered bone for ensuring better reconstruction of mandible function.According to the results of in vivo experiments,the bone regenerated using hierarchical vascularized engineered bone is similar to the natural mandibular bone in terms of morphology and genomics.The sonic hedgehog signaling pathway is specifically activated in hierarchical vascularized engineered bone,indicating that the new bone in hierarchical vascularized engineered bone underwent a process of intramembranous ossification identical to that of mandible development.Thus,hierarchical vascularized engineered bone has a high potential for clinical application in mandibular defect reconstruction.Moreover,the concept based on developmental processes and bionic structures provides an effective strategy for tissue regeneration.

VEGF-expressing Bone Marrow Mesenchymal Stem Cells Transplantation Improved Heart Function of Myocardial Infarct Rabbits

Objectives To treat myocardial infarction with MSCs transplantation combined with VEGF gene therapy in rabbits and to study its mechanisms. Methods Forty-eight rabbits were randomly divided into MI group （n=12）, MSCs group （n=12）, VEGF group （n=12）, MSCs＋VEGF group （M＋V group, n=12）. Rabbit myocardial infarction models were founded by the ligation of left anterior descending artery. 107 MSCs were injected into the infarct-zone in four sites 2 weeks later in MSCs and M＋ V group, phVEGF gene were injected in infarct-zone in VEGF group and MSCs transfected with phVEGF gene were injected in M＋V group. Heart function including LVEDP, LVSP, LVDP, -dp/dtmax, ＋dp/dtmax, were measured in vivo. The hearts were harvested at 4 weeks after transplantation and sectioned for HE stain, immunohistochemical stain of BrdU and VIII factor antigen. Results The left ventricular hemodynamics parameters showed that heart function were improved more in M＋V group than MSCs group, MI group and VEGF group. The numbers of BrdU positive cells in M＋ V group（61±8）were more than in MSCs group （44±8, P 〈 0.01）. The numbers of vessels in infarcted zone were more in M＋V group （49±8） than in MSCs group （33±6, P 〈 0.01）,VEGF group（30±8, P 〈 0.01）and Mlgroup （18±4, P〈0.01）. Conclusions VEGF-expressing MSCs transplantation could improve heart function after myocardial infarction, and they were more effective than sole MSCs transplantation. Keeping more MSCs survival and ameliorating the blood supply of infarct-zone might be involved in the mechanisms.

CO-TRANSFECTION OF RAT BONE MARROW MESENCHYMAL STEM CELLS WITH HUMAN BMP2 AND VEGF165 GENES

Objective To explore the feasibility and efficacy of lentivirus-mediated co-transfection of rat bone marrow mesenchymal stem cells （MSCs） with human vascular endothelial growth factor 165 （hVEGFI65） gene and human bone morphogenetic protein 2 （hBMP2） gene. Methods The hVEGF165 and hBMP2 cDNAs were obtained from human osteosarcoma cell line MG63 and cloned into lentiviral expression vectors designed to co-express the copepod green fluorescent protein （copGFP）. The expression lentivector and packaging Plasmid Mix were co-transferred to 293TN cells, which produced the lentivirus carrying hVEGF165 （Lv-VEGF） or hBMP2 （ Lv-BMP） , respectively. MSCs of Wistar rats were co-transfected with Lv-BMP and Lv-VEGF （BMP ＋ VEGF group）, or each alone （BMP group and VEGF group）, or with no virus （ Control group）. The mRNA and protein expressions of hVEGF165 and hBMP2 genes in each group were detected by real-time PCR and enzyme linked immunosorbent assay （ELISA）. Results Lentiviral expression vectors carrying hVEGF165 or hBMP2 were correctly constructed and confirmed by restriction endonucleses analysis and DNA sequencing analysis. A transfer efficiency up to 90% was archieved in all the transfected groups detected by the fraction of fluorescent cells using fluorescent microscopy. From the results generated by real-time PCR and ELISA, VEGF165 and BMP2 genes were co-expressed in BMP ＋ VEGF group. No significant difference of BMP2 expression was detected between BMP ＋ VEGF and BMP groups （ P 〉 0. 05）. Similarly, there was no significant difference of VEGF165 expression between BMP ＋ VEGF and VEGF groups （ P 〉 0. 05）. Conclusion VEGF165 and BMP2 genes were successfully co-expressed in MSCs by lentivirus-mediated co-transfection, which provided a further foundation for the combined gene therapy of bone regeneration.

Reconstruction of extremity long bone defects with vascularized fibula bone grafts

Aim: Composite tissue defects encompassing bone and/or isolated bony defects can pose a surgical challenge;however, their reconstruction is critical for successful functional limb salvage. These cases become increasingly problematic as secondary defects, following multiple nonvascularized grafting attempts resulting in complex bony nonunion. Herein, our experience utilizing fibula vascularized bone grafts (VBGs) for bone restoration will be presented to demonstrate their utility in a variety of reconstructions for limb salvage. Methods: This is a case series describing a series of vascularized fibula grafts for extremity reconstruction performed by a single academic surgeon over multiple institutions in seven years. Results: Twenty-seven (27) total VBGs met inclusion criteria and underwent reconstruction for traumatic (16), oncologic (6) and chronic degenerative (5) etiologies. Bony union was achieved in 26 of 27 cases. Conclusion: The decision-making process for bony reconstruction in these scenarios is difficult and multivariable. Fibula VBGs can provide a single-stage solution for autologous bony and soft tissue replacement of large or complex bone defects and can often be superior options compared with non-vascularized bone grafts or non-bone internal fixation techniques. Their osteogenic potential is unmatched by allogenic or synthetic substitutions. These benefits are evident in a variety of clinical settings such as pediatrics, oncology and trauma.

Role of the bone marrow vascular niche in chemotherapy for MLL-AF9-induced acute myeloid leukemia

Leukemia stem cells in acute myeloid leukemia(AML)can persist within unique bone marrow niches similar to those of healthy hematopoietic stem cells and resist chemotherapy.In the context of AML,endothelial cells(ECs)are crucial components of these niches that appear to promote malignant expansion despite treatment.To better understand these interactions,we developed a real-time cell cycle-tracking mouse model of AML(Fucci-MA9)with an aim of unraveling why quiescent leukemia cells are more resistant to chemotherapy than cycling cells and proliferate during disease relapse.We found that quiescent leukemia cells were more prone to escape chemotherapy than cycling cells,leading to relapse and proliferation.Importantly,post-chemotherapy resting leukemia cells tended to localize closer to blood vessels.Mechanistically,after chemotherapy,resting leukemia cells interacted with ECs,promoting their adhesion and anti-apoptotic capacity.Further,expression analysis of ECs and leukemia cells during AML,after chemotherapy,and after relapse revealed the potential of suppressing the post-chemotherapy inflammatory response to regulate the functions of leukemia cells and ECs.These findings highlight the role of leukemia cells in evading chemotherapy by seeking refuge near blood vessels and provide important insights and directions for future AML research and treatment.

The evolution of lower extremity reconstruction

Reconstruction of the lower extremity is a complex task that has evolved greatly in both technique and indication over the past century.Early advances in treating traumatic lower extremity injuries focused on primary amputation to avoid the high mortality of infection.The introduction of antibiotics improved surgical debridement and local reconstructive options,enhancing the viability of lower extremities with simple and proximal defects.With the advent of microvascular surgery,free tissue transfer techniques provided a means to reconstruct more distal and complex problems.As these surgical techniques have continued to evolve,so too have indications for reconstruction,patient management and post-operative care-now with a greater emphasis on patient quality of life and limb function.The purpose of this article is to outline the evolution of lower extremity reconstruction,and how the standard of practice has changed over time.