Tissue Extracts From Infarcted Myocardium of Rats in Promoting the Differentiation of Bone Marrow Stromal Cells Into Cardiomyocyte-like Cells

Objective To investigate whether cardiac tissue extracts from rats could mimic the cardiac microenvironment and act as a natural inducer in promoting the differentiation of bone marrow stromal cells （BMSCs） into cardiomyocytes. Methods Three kinds of tissue extract or cell lysate [infarcted myocardial tissue extract （IMTE）, normal myocardial tissue extract （NMTE） and cultured neonatal myocardial lysate （NML）] were employed to induce BMSCs into cardiomyocyte-like cells. The cells were harvested at each time point for reverse transcription-polymerase chain reaction （RT-PCR） detection, immunocytochemical analysis, and transmission electron microscopy. Results After a 7-day induction, BMSCs were enlarged and polygonal in morphology. Myofilaments, striated sarcomeres, Z-lines, and more mitochondia were observed under transmission electron microscope. Elevated expression levels of cardiac-specific genes and proteins were also confirmed by RT-PCR and immunocytochemistry. Moreover, IMTE showed a greater capacity of differentiating BMSCs into cardiomyocyte-like cells. Conclusions Cardiac tissue extracts, especially IMTE, can effectively differentiate BMSCs into cardiomyocyte-like cells.

Cartilage and bone tissue engineering using adipose stromal/stem cells spheroids as building blocks

Scaffold-free techniques in the developmental tissue engineering area are designed to mimic in vivo embryonic processes with the aim of biofabricating,in vitro,tissues with more authentic properties.Cell clusters called spheroids are the basis for scaffold-free tissue engineering.In this review,we explore the use of spheroids from adult mesenchymal stem/stromal cells as a model in the developmental engineering area in order to mimic the developmental stages of cartilage and bone tissues.Spheroids from adult mesenchymal stromal/stem cells lineages recapitulate crucial events in bone and cartilage formation during embryogenesis,and are capable of spontaneously fusing to other spheroids,making them ideal building blocks for bone and cartilage tissue engineering.Here,we discuss data from ours and other labs on the use of adipose stromal/stem cell spheroids in chondrogenesis and osteogenesis in vitro.Overall,recent studies support the notion that spheroids are ideal"building blocks"for tissue engineering by“bottom-up”approaches,which are based on tissue assembly by advanced techniques such as three-dimensional bioprinting.Further studies on the cellular and molecular mechanisms that orchestrate spheroid fusion are now crucial to support continued development of bottom-up tissue engineering approaches such as three-dimensional bioprinting.

The Experimental Study of Constructing Tissue Engineered Bone by Compounding Zinc-sintered Bovine Cancellous Bone with Marrow Stromal Cells

To study the osteogenic ability of tissue-engineered bone constructed by compounding zinc-sintered bovine cancellous bone with rabbit marrow stromal cells (MSCs) in vivo,the zinc-sintered bovine cancellous bone of beta-tricalcium phosphate (TCP) type was prepared by sintering the fresh calf cancellous bone twice and then loading it with zinc-ion.The rabbit MSCs were cultured,induced and seeded onto the zinc-sintered bovine cancellous bones.The tissue-engineered bones were then implanted into the rabbits' back muscles.The newly formed bone tissues were observed by histological methods and the areas of new osseous tissues were measured at the end of the 4th and 8th week.The zinc-sintered bovine cancellous bones alone were implanted on the other side as control.The osteogenic activity of MSCs was identified by alkaline phosphatase (ALP) staining and calcification nod chinalizarin staining.At the end of 4th week,a small amount of new bone tissues was observed.At the end of 8th week,there were many newly formed bone mature tissues.Moreover,the area of the latter was significantly larger than that of the former(P<0.01),while in the control group there was no new bone formation.The tissue-engineered bone,which was constructed by combining zinc-sintered bovine cancellous bone with MSCs,has satisfactory osteogenic capabilities in vivo.

Biocompatibility Studies on Bone Marrow Stromal Cells with Chitosan-gelatin Blends

To study the effect of chitosan-gelatin blends on the growth and proliferation of in vitro cultured bone marrow stromal cells(BMSCs) and explore a new carrier for the application of tissure engineering, cells from long bones of young rabbitsaged less than two weeks were expanded in vitro for one week and seeded onto the surface of pure chitosan and chitosan-gelatin blends. Cells attached to and proliferated on both pure chitosan and chitosan-gelatin blends were monitored with the aid of an inverted light microscope and a scanning electron microscope. The cell viability was monitored by MTT after 2, 4, 6, 8 days seeding. BMSCs could be attached to and proliferated on both pure chitosan and chitosan-gelatin blends and remain their morphologies seen in vivo. Chitosan-gelatin blends could promote BMSCs to proliferate(P<0.01). It is confirmed that chitosan-gelatin blends maintain the bioactivity feature of chitosan and even enhance the growth and proliferation of in vitro cultured BMSCs because of the adding of gelatin. It is a potential carrier for the delivery of cells tissue engineering.

TISSUE-ENGINEERED GRAFT CONSTRUCTED BY SELF-DERIVED BONE MARROW MONONUCLEAR CELLS AND HETEROGENEOUS ACELLULARIZED TISSUE MATRIX

Objective To create a method for constructing a tissue-engineered graft with self-derived bone marrow cells and heterogeneous acellular matrix.Methods The mononuclear cells were isolated from bone marrows drawn from piglets and cultured in different mediums including either vascular endothelial growth factor(VEGF)or platelet derived growth factor BB(PDGF-BB)to observe their expansion and differentiation.The aortas harvested from canines were processed by a multi-step decellularizing technique to erase.The bone marrow mononuclear cells cultured in the mediums without any growth factors were seeded to the acellular matrix.The cells-seeded grafts were incubated in vitro for 6 d and then implanted to the cells-donated piglets to substitute parts of their native pulmonary arteries.Results After 4 d culturing,the cells incubated in the medium including VEGF showed morphological feature of endothelial cells(ECs)and were positive to ECs-specific monoclonal antibodies of CD31,FLK-1,VE-Cadherin and vWF.The cells incubated in the medium including PDGF-BB showed morphological feature of smooth muscle cells(SMCs)and were positive to SMCs-specific monoclonal antibodies of α-SMA and Calponin.One hundred days after implantation of seeded grafts,the inner surfaces of explants were smooth without thrombosis,calcification and aneurysm.Under the microscopy,plenty of growing cells could be seen and elastic and collagen fibers were abundant.Conclusion Mesenchymal stem cells might exist in mononuclear cells isolated from bone marrow.They would differentiate into endothelial cells or smooth muscle cells in proper in vitro or in vivo environments.The bone marrow mononuclear cells might be a choice of seeding cells in constructing tissue-engineered graft.

Collagen-chitosan scaffold impregnated with bone marrow mesenchymal stem cells for treatment of traumatic brain injury

Combinations of biomaterials and cells can effectively target delivery of cells or other therapeutic factors to the brain to rebuild damaged nerve pathways after brain injury.Porous collagen-chitosan scaffolds were prepared by a freeze-drying method based on brain tissue engineering.The scaffolds were impregnated with rat bone marrow mesenchymal stem cells.A traumatic brain injury rat model was established using the 300 g weight free fall impact method.Bone marrow mesenchymal stem cells/collagen-chitosan scaffolds were implanted into the injured brain.Modified neurological severity scores were used to assess the recovery of neurological function.The Morris water maze was employed to determine spatial learning and memory abilities.Hematoxylin-eosin staining was performed to measure pathological changes in brain tissue.Immunohistochemistry was performed for vascular endothelial growth factor and for 5-bromo-2-deoxyuridine(BrdU)/neuron specific enolase and BrdU/glial fibrillary acidic protein.Our results demonstrated that the transplantation of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds to traumatic brain injury rats remarkably reduced modified neurological severity scores,shortened the average latency of the Morris water maze,increased the number of platform crossings,diminished the degeneration of damaged brain tissue,and increased the positive reaction of vascular endothelial growth factor in the transplantation and surrounding areas.At 14 days after transplantation,increased BrdU/glial fibrillary acidic protein expression and decreased BrdU/neuron specific enolase expression were observed in bone marrow mesenchymal stem cells in the injured area.The therapeutic effect of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds was superior to stereotactic injection of bone marrow mesenchymal stem cells alone.To test the biocompatibility and immunogenicity of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds,immunosuppressive cyclosporine was intravenously injected 12 hours before transplantation and 1-5 days after transplantation.The above indicators were similar to those of rats treated with bone marrow mesenchymal stem cells and collagen-chitosan scaffolds only.These findings indicate that transplantation of bone marrow mesenchymal stem cells in a collagen-chitosan scaffold can promote the recovery of neuropathological injury in rats with traumatic brain injury.This approach has the potential to be developed as a treatment for traumatic brain injury in humans.All experimental procedures were approved by the Institutional Animal Investigation Committee of Capital Medical University,China(approval No.AEEI-2015-035)in December 2015.

Combining acellular nerve allografts with brainderived neurotrophic factor transfected bone marrow mesenchymal stem cells restores sciatic nerve injury better than either intervention alone

In this study, we chemically extracted acellular nerve allografts from bilateral sciatic nerves, and repaired 10-mm sciatic nerve defects in rats using these grafts and brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells. Experiments were performed in three groups： the acellular nerve allograft bridging group, acellular nerve allograft ＋ bone marrow mesenchymal stem cells group, and the acellular nerve allograft ＋ brain-derived neurotrophic factor transfected bone marrow mesenchyrnal stem cells group. Results showed that at 8 weeks after bridging, sciatic functional index, triceps wet weight recovery rate, myelin thickness, and number of myelinated nerve fibers were significantly changed in the three groups. Variations were the largest in the acellular nerve allograft ＋ brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells group compared with the other two groups. Experimental findings suggest that chemically extracted acellular nerve allograft combined nerve factor and mesenchymal stem cells can promote the restoration of sciatic nerve defects. The repair effect seen is better than the single application of acellular nerve allograft or acellular nerve allograft combined mesenchymal stem cell transplantation.

Platelet-rich plasma-induced bone marrow mesenchymal stem cells versus autologous nerve grafting for sciatic nerve repair

Autologous nerve grafting is the gold standard of peripheral nerve repair.We previously showed that autologous platelet-rich plasma（PRP）contains high concentrations of growth factors and can induce in vitro cultured bone marrow mesenchymal stem cells（BMSCs）to differentiate into Schwann cells.Here we used PRP-induced BMSCs combined with chemically extracted acellular nerves to repair sciatic nerve defects and compared the effect with autologous nerve grafting.The BMSCs and chemically extracted acellular nerve promoted target muscle wet weight restoration,motor nerve conduction velocity,and axonal and myelin sheath regeneration,with similar effectiveness to autologous nerve grafting.This finding suggests that PRP induced BMSCs can be used to repair peripheral nerve defects.

Nanofibrous Scaffold Containing Osteoblast-Derived Extracellular Matrix for the Proliferation of Bone Marrow Mesenchymal Stem Cells

Extracellular matrix( ECM) plays a prominent role in establishing and maintaining an appropriate microenvironment for tissue regeneration. The aims of this study were to construct a tissue engineered scaffold by reconstituting osteoblast cell-derived ECM( O-ECM) on the electrospun nanofibrous scaffold,and further to evaluate its subsequent application for promoting the proliferation of bone marrow mesenchymal stem cells( BMSCs). To engineer a biomimetic scaffold, calvarial osteoblasts and electrospun poly-llactic acid( PLLA) nanofibers were prepared and subjected to decellularize for O-ECM deposition. To evaluate and characterize the O-ECM/PLLA scaffold, the morphology was examined and several specific mark proteins of osteoblasts matrix were evaluated.Furthermore,the cell counting kit-8( CCK-8) assay was used to detect the proliferation of the BMSCs cultivated on the O-ECM/PLLA scaffold. The results indicated O-ECM/PLLA scaffold was loaded with Collagen I, Fibronectin, and Laminin, as the composition of the marrow ECM. After decellularization,O-ECM deposition was observed in O-ECM/PLLA scaffold. Moreover,the O-ECM/PLLA scaffold could significantly enhance the proliferation of BMSCs,suggesting better cytocompatibility compared to the other groups tested. Taken together,a biomimetic scaffold based on the joint use of O-ECM and PLLA biomaterials,which represents a promising approach to bone tissue engineering, facilitates the expansion of BMSCs in vitro.

Modifying oxygen tension affects bone marrow stromal cell osteogenesis for regenerative medicine

AIM To establish a hypoxic environment for promoting osteogenesis in rat marrow stromal cells(MSCs) using osteogenic matrix cell sheets(OMCSs).METHODS Rat MSCs were cultured in osteogenic media under one of four varying oxygen conditions: Normoxia(21% O_2) for 14 d(NN), normoxia for 7 d followed by hypoxia(5% O_2) for 7 d(NH), hypoxia for 7 d followed by normoxia for 7 d(HN), or hypoxia for 14 d(HH). Osteogenesis was evaluated by observing changes in cell morphology and calcium deposition, and by measuring osteocalcin secretion(ELISA) and calcium content. In vivo syngeneic transplantation using OMCSs and β-tricalcium phosphate discs, preconditioned under NN or HN conditions, was also evaluated by histology, calcium content measurements,and real-time quantitative PCR.RESULTS In the NN and HN groups, differentiated, cuboidal-shaped cells were readily observed, along with calcium deposits. In the HN group, the levels of secreted osteocalcin increased rapidly from day 10 as compared with the other groups, and plateaued at day 12(P < 0.05). At day 14, the HN group showed the highest amount of calcium deposition. In vivo, the HN group showed histologically prominent new bone formation, increased calcium deposition, and higher collagen type Ⅰ?messenger RNA expression as compared with the NN group.CONCLUSION The results of this study indicate that modifying oxygen tension is an effective method to enhance the osteogenic ability of MSCs used for OMCSs.

Wnt3a-induced ST2 decellularized matrix ornamented PCL scaffold for bone tissue engineering

The limited bioactivity of scaffold materials is an important factor that restricts the development of bone tissue engineering.Wnt3a activates the classicWnt/β-catenin signaling pathway which effects bone growth and development by the accumulation ofβ-catenin in the nucleus.In this study,we fabricated 3D printed PCL scaffold with Wnt3a-induced murine bone marrow-derived stromal cell line ST2 decellularized matrix(Wnt3a-ST2-dCM-PCL)and ST2 decellularized matrix(ST2-dCM-PCL)by freeze-thaw cycle and DNase decellularization treatment which efficiently decellularized>90%DNA while preserved most protein.Compared to ST2-dCM-PCL,Wnt3a-ST2-dCM-PCL significantly enhanced newly-seeded ST2 proliferation,osteogenic differentiation and upregulated osteogenic marker genes alkaline phosphatase(Alp),Runx2,type I collagen(Col 1)and osteocalcin(Ocn)mRNA expression.After 14 days of osteogenic induction,Wnt3a-ST2-dCM-PCL promoted ST2 mineralization.These results demonstrated that Wnt3a-induced ST2 decellularized matrix improve scaffold materials’osteoinductivity and osteoconductivity.

Experimental Study on Allogenic Decalcified Bone Matrix as Carrier for Bone Tissue Engineering

The biocompatibility and osteogenic activity of allogenic decalcified bone matrix (DBM) used as a carrier for bone tissue engineering were studied. Following the method described by Urist, allogenic DBM was made. In vitro, DBM and bone marrow stromal cell (BMSC) from rabbits were co-cultured for 3-7 days and subjected to HE staining, and a series of histomorphological observations were performed under phase-contrast microscopy and scanning electron microscopy (SEM). In vivo the mixture of DBM/BMSC co-cultured for 3 days was planted into one side of muscules sacrospinalis of rabbits, and the DBM without BMSC was planted into other side as control. Specimens were collected at postoperative week 1, 2 and 4, and subjected to HE staining, and observed under SEM. The results showed during culture in vitro, the BMSCs adherent to the wall of DBM grew, proliferated and had secretive activity. The in vivo experiment revealed that BMSCs and undifferentiated mesenchymal cells in the perivascular region invaded gradually and proliferated together in DBM/BMSC group, and colony-forming units of chondrocytes were found. Osteoblasts, trabecular bone and medullary cavity appeared. The inflammatory reaction around muscles almost disappeared at the second weeks. In pure DBM group, the similar changes appeared from the surface of the DBM to center, and the volume of total regenerate bones was less than the DBM/BMSC group at the same time. The results indicated that the mixture of DBM and BMSC had good biocompatibility and ectopic induced osteogenic activity.

Differentiation of mesenchymal stem cells into neuronal cells on fetal bovine acellular dermal matrix as a tissue engineered nerve scaffold

The purpose of this study was to assess fetal bovine acellular dermal matrix as a scaffold for supporting the differentiation of bone marrow mesenchymal stem cells into neural cells fol-lowing induction with neural differentiation medium. We performed long-term, continuous observation of cell morphology, growth, differentiation, and neuronal development using several microscopy techniques in conjunction with immunohistochemistry. We examined speciifc neu-ronal proteins and Nissl bodies involved in the differentiation process in order to determine the neuronal differentiation of bone marrow mesenchymal stem cells. The results show that bone marrow mesenchymal stem cells that differentiate on fetal bovine acellular dermal matrix display neuronal morphology with unipolar and bi/multipolar neurite elongations that express neuro-nal-speciifc proteins, includingβIII tubulin. The bone marrow mesenchymal stem cells grown on fetal bovine acellular dermal matrix and induced for long periods of time with neural differen-tiation medium differentiated into a multilayered neural network-like structure with long nerve ifbers that was composed of several parallel microifbers and neuronal cells, forming a complete neural circuit with dendrite-dendrite to axon-dendrite to dendrite-axon synapses. In addition, growth cones with filopodia were observed using scanning electron microscopy. Paraffin sec-tioning showed differentiated bone marrow mesenchymal stem cells with the typical features of neuronal phenotype, such as a large, round nucleus and a cytoplasm full of Nissl bodies. The data suggest that the biological scaffold fetal bovine acellular dermal matrix is capable of supporting human bone marrow mesenchymal stem cell differentiation into functional neurons and the subsequent formation of tissue engineered nerve.

Liver regeneration using decellularized splenic scaffold: a novel approach in tissue engineering

BACKGROUND： The potential application of decellularized liver scaffold for liver regeneration is limited by severe shortage of donor organs. Attempt of using heterograft scaffold is accompanied with high risks of zoonosis and immunological rejection. We proposed that the spleen, which procured more extensively than the liver, could be an ideal source of decellularized scaffold for liver regeneration. METHODS： After harvested from donor rat, the spleen was processed by 12-hour freezing/thawing ×2 cycles, then circulation perfusion of 0.02% trypsin and 3% Triton X-100 sequentially through the splenic artery for 32 hours in total to prepare decellularized scaffold. The structure and component characteristics of the scaffold were determined by hematoxylin and eosin and immumohistochemical staining, scanning electron microscope, DNA detection, porosity measurement, biocompatibility and cytocompatibility test. Recellularization of scaffold by 5×106 bone marrow mesenchymal stem cells（BMSCs） was carried out to preliminarily evaluate the feasibility of liver regeneration by BMSCs reseeding and differentiation in decellularized splenic scaffold.RESULTS： After decellularization, a translucent scaffold, which retained the gross shape of the spleen, was generated. Histological evaluation and residual DNA quantitation revealed the remaining of extracellular matrix without nucleus and cytoplasm residue. Immunohistochemical study proved the existence of collagens I, IV, fibronectin, laminin and elastin in decellularized splenic scaffold, which showed a similarity with decellularized liver. A scanning electron microscope presented the remaining three-dimensional porous structure of extracellular matrix and small blood vessels. The poros-ity of scaffold, aperture of 45.36±4.87 μm and pore rate of 80.14%±2.99% was suitable for cell engraftment. Subcutaneous implantation of decellularized scaffold presented good histocompatibility, and recellularization of the splenic scaffold demonstrated that BMSCs could locate and survive in the decellularized matrix. CONCLUSION： Considering the more extensive organ source and satisfying biocompatibility, the present study indicated that the three-dimensional decellularized splenic scaffold might have considerable potential for liver regeneration when combined with BMSCs reseeding and differentiation.

Role of endogenous Schwann cells in tissue repair after spinal cord injury

Schwann cells are glial cells of peripheral nervous system, responsible for axonal myelination and ensheathing, as well as tissue repair following a peripheral nervous system injury. They are one of several cell types that are widely studied and most commonly used for cell transplantation to treat spinal cord injury, due to their intrinsic characteristics including the ability to secrete a variety of neurotrophic factors. This mini review summarizes the recent findings of endogenous Schwann cells after spinal cord injury and discusses their role in tissue repair and axonal regeneration. After spinal cord injury, numerous endogenous Schwann cells migrate into the lesion site from the nerve roots, involving in the construction of newly formed repaired tissue and axonal myelination. These invading Schwann cells also can move a long distance away from the injury site both rostrally and caudally. In addition, Schwann cells can be induced to migrate by minimal insults （such as scar ablation） within the spinal cord and integrate with astrocytes under certain circumstances. More importantly, the host Schwann cells can be induced to migrate into spinal cord by transplantation of different cell types, such as exogenous Schwann cells, olfactory ensheathing cells, and bone marrow-derived stromal stem cells. Migration of endogenous Schwann cells following spinal cord injury is a common natural phenomenon found both in animal and human, and the myelination by Schwann cells has been examined effective in signal conduction electrophysiologically. Therefore, if the inherent properties of endogenous Schwann cells could be developed and utilized, it would offer a new avenue for the restoration of injured spinal cord.

Comparative study on seeding methods of human bone marrow stromal cells in bone tissue engineering

Background In general the traditional static seeding method has its limitation while the dynamic seeding method reveals its advantages over traditional static method. We compared static and dynamic seeding method for human bone marrow stromal cells (hBMSCs) in bone tissue engineering. Methods DNA assay was used for detecting the maximal initial seeding concentration for static seeding. Dynamic and static seeding methods were compared, when scaffolds were loaded with hBMSCs at this maximal initial cell seeding concentration. Histology and scanning electron microscope (SEM) were examined to evaluate the distribution of cells inside the constructs. Markers encoding osteogenic genes were measured by fluorescent RT-PCR. The protocol for dynamic seeding of hBMSCs was also investigated. Results DNA assay showed that the static maximal initial seeding concentration was lower than that in dynamic seeding. Histology and SEM showed even distribution and spread of cells in the dynamically seeded constructs, while their statically seeded counterparts showed cell aggregation. Fluorescent RT-PCR again showed stronger osteogenic potential of dynamically seeded constructs. Conclusion dynamic seeding of hBMSCs is a promising technique in bone tissue engineering.

WJSC 6^(th) Anniversary Special Issues(2):Mesenchymal stem cells Mesenchymal stem cells in the treatment of spinal cord injuries:A review

With technological advances in basic research,the intricate mechanism of secondary delayed spinal cord injury(SCI)continues to unravel at a rapid pace.However,despite our deeper understanding of the molecular changes occurring after initial insult to the spinal cord,the cure for paralysis remains elusive.Current treatment of SCI is limited to early administration of high dose steroids to mitigate the harmful effect of cord edema that occurs after SCI and to reduce the cascade of secondary delayed SCI.R ecent evident-based clinical studies have cast doubt on the clinical benefit of steroids in SCI and intense focus on stem cell-based therapy has yielded some encouraging results.An array of mesenchymal stem cells(MSCs)from various sources with novel and promising strategies are being developed to improve function after SCI.In this review,we briefly discuss the pathophysiology of spinal cord injuries and characteristics and the potential sources of MSCs that can be used in the treatment of SCI.We will discuss the progress of MSCs application in research,focusing on the neuroprotective properties of MSCs.Finally,we will discuss the results from preclinical and clinical trials involving stem cell-based therapy in SCI.

Transfect bone marrow stromal cells with pcDNA3.1-VEGF to construct tissue engineered bone in defect repair

Background We previously showed that nano-hydroxyapatite/carboxymethyl chitosan （n-Ha/CMCS） displayed excellent mechanical properties, good degradation rates and exceptional biocompatibility, with negligible toxicity. The aim of this study was to determine the effect of the same composite with vascular endothelial growth factor （VEGF）transfected bone marrow stromal cells （BMSCs） in a rabbit radial defect model.

The ectopic study of tissue-engineered bone with hBMP-4 gene modified bone marrow stromal cells in rabbits

Background Tissue-engineering techniques combined with gene therapy have beenrecently reported to improve osteogenesis. In this study, tissue-engineered bone constructed byhuman Bone Morphogenetic Protein 4 (hBMP-4) gene-modified bone marrow stromal cells (bMSCs) wasexplored in an ectopic bone formation model in rabbits. Methods A pEGFP-hBMP-4 mammalian plasmid (EGFP: Enhanced Green Fluorescent Protein) was constructed by subcloning techniques. bMSCs obtainedfrom rabbits were cultured and transfected with either pEGFP-hBMP-4, pEGFP or left uninfected invitro. Transfer efficiency was detected through the expression of EGFP. Transcription of the targetgene was detected by RT-PCR. Alkaline phosphatase (ALP) and Von Kossa tests were also conducted toexplore the phenotypes of osteoblasts. The autologous bMSCs of the 3 groups were then combined withNatural Non-organic Bone ( NNB) , a porous hydroxyapatite implant with a dimension of 6 mm x 6 mm x3 mm, at a concentration of 5 x 10~7 cells/ml. They were subsequently implanted into 6 rabbitssubcutaneously using NNB alone as a blank control (6 implants per group). Four weeks after surgery,the implants were evaluated with histological staining and computerized analysis of new boneformation. Results pEGFP-hBMP-4 expression plasmid was constructed. Under optimal conditions, genetransfer efficiency reached more than 30% , Target gene transfer could strengthen the transcriptionof BMP-4, and increase the expression of ALP as well as the number of calcium nodules. In theectopic animal model, NNB alone could not induce new bone formation. The new bone area formed in thebMSCs group was (17.2 ± 7.1)%, and pEGFP group was (14.7 ± 6.1) % , while pEGFP-hBMP-4 group was(29.5 ± 8.2) % , which was the highest among the groups (F = 7.295, P < 0. 01). Conclusions Themammalian hBMP-4 expression plasmid was successfully constructed and a comparatively high transferefficiency was achieved. The gene transfer technique enhanced the expression of BMP-4 and promoteddifferentiation from bMSCs to osteoblasts. These in vivo results suggested that transfection ofbMSCs with hBMP-4 might be a suitable method to enhance their inherent osteogenic capacity for bonetissue engineering applications.