Effects of recombinant adeno-associated viral vectors on angiopoiesis and osteogenesis in cultured rabbit bone marrow stem cells via co-expressing hVEGF and hBMP genes: a preliminary study in vitro

VEGF-A and FGF4 Engineered C2C12 Myoblasts and Angiogenesis in the Chick Chorioallantoic Membrane

Angiogenesis is the formation of new blood vessels from pre-existing vessels. Adequate oxygen transport and waste removal are necessary for tissue homeostasis. Restrictions in blood supply can lead to ischaemia which can contribute to disease pathology. Vascular endothelial growth factor (VEGF) is essential in angiogenesis and myogenesis, making it an ideal candidate for angiogenic and myogenic stimulation in muscle. We established C2C12 mouse myoblast cell lines which stably express elevated levels of (i) human VEGF-A and (ii) dual human FGF4-VEGF-A. Both stably transfected cells secreted increased amounts of human VEGF-A compared to non-transfected cells, with the latter greater than the former. In vitro, conditioned media from engineered cells resulted in a significant increase in endothelial cell proliferation, migration, and tube formation. In vivo, this conditioned media produced a 1.5-fold increase in angiogenesis in the chick chorioallantoic membrane (CAM) assay. Delivery of the engineered myoblasts on Matrigel demonstrated continued biological activity by eliciting an almost 2-fold increase in angiogenic response when applied directly to the CAM assay. These studies qualify the use of genetically modified myoblasts in therapeutic angiogenesis for the treatment of muscle diseases associated with vascular defects.

Synergistic effects of recombinant Lentiviral-mediated BMP2 and TGF-beta3 on the osteogenic differentiation of rat bone marrow mesenchymal stem cells in vitro

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs) are considered good candidates for seed cells in bone engineering. The study aim to investigate the synergistic effects of human bone morphogenetic protein 2 (hBMP2) and transforming growth factor beta3 (hTGF-beta3) modified BMSCs on inducing osteogenic differentiation in vitro.

METHODS

Lentivirus (LV) carrying hBMP2 and/or hTGF-beta3 genes were constructed and used to transduce rat BMSCs. The expression of osteogenic molecules was detected by qRT-PCR and western blotting.

RESULTS

Targeted genes were PCR-amplified and confirmed by DNA sequencing and BLAST analysis. BMSCs infected by vectors effectively resulted in the overexpressions of hBMP2 and hTGF-beta3 and higher levels of hBMP2 and hTGF-beta3 in the culture supernatant. The co-transduction of hBMP2 and hTGF-beta3 induced BMSCs osteogenic differentiation more effectively than the transduction of hBMP2 or hTGF-beta3 individually. The expression levels of osteopontin (OPN), osteocalcin (OCN), and osteoprotegerin (OPG) in LV-hBMP2 + LV-hTGF-beta3 group (BMSCs transfected by vectors respectively carrying hBMP-2 gene and hTGF-beta3 gene) and LV-hBMP2-hTGF-beta3 group (BMSCs transfected by vector carrying hBMP2 and hTGF-beta3 fusion gene) were significantly higher than in LV-BMP2 (BMSCs transfected by vector carrying hBMP2 gene) and LV-TGF-beta3 (BMSCs transfected by vector carrying hTGF-beta3 gene) groups (P < 0.05). The hBMP2 and/or hTGF-beta3 overexpression upregulated alkaline phosphatase (ALP) activity.

CONCLUSION

The present study showed that hBMP2 and/or hTGF-beta3 genes can be successfully overexpressed in BMSCs. Our study proved that the two cytokines (hBMP2 and hTGF-beta3) could induce bone differentiation synergistically, which foresees the use of the combination of these two cytokines as a therapeutic strategy in the future.

Micrornas at the Interface between Osteogenesis and Angiogenesis as Targets for Bone Regeneration

Bone formation and regeneration is a multistep complex process crucially determined by the formation of blood vessels in the growth plate region. This is preceded by the expression of growth factors, notably the vascular endothelial growth factor (VEGF), secreted by osteogenic cells, as well as the corresponding response of endothelial cells, although the exact mechanisms remain to be clarified. Thereby, coordinated coupling between osteogenesis and angiogenesis is initiated and sustained. The precise interplay of these two fundamental processes is crucial during times of rapid bone growth or fracture repair in adults. Deviations in this balance might lead to pathologic conditions such as osteoarthritis and ectopic bone formation. Besides VEGF, the recently discovered important regulatory and modifying functions of microRNAs also support this key mechanism. These comprise two principal categories of microRNAs that were identified with specific functions in bone formation (osteomiRs) and/or angiogenesis (angiomiRs). However, as hypoxia is a major driving force behind bone angiogenesis, a third group involved in this process is represented by hypoxia-inducible microRNAs (hypoxamiRs). This review was focused on the identification of microRNAs that were found to have an active role in osteogenesis as well as angiogenesis to date that were termed "CouplingmiRs (CPLGmiRs)". Outlined representatives therefore represent microRNAs that already have been associated with an active role in osteogenic-angiogenic coupling or are presumed to have its potential. Elucidation of the molecular mechanisms governing bone angiogenesis are of great relevance for improving therapeutic options in bone regeneration, tissue-engineering, and the treatment of bone-related diseases.

Multiscale Stem Cell Technologies for Osteonecrosis of the Femoral Head

The last couple of decades have seen brilliant progress in stem cell therapies, including native, genetically modified, and engineered stem cells, for osteonecrosis of the femoral head (ONFH). In vitro studies evaluate the effect of endogenous or exogenous factor or gene regulation on osteogenic phenotype maintenance and/or differentiation towards osteogenic lineage. The preclinical and clinical outcomes accelerate the clinical translation. Bone marrow mesenchymal stem cells and adipose-derived stem cells have demonstrated better effects in the treatment of femoral head necrosis. Various materials have been used widely in the ONFH treatment in both preclinical and clinical trials. In a word, in vivo and multiscale efforts are expected to overcome obstacles in the approaches for treating ONFH and provide clinical relevance and commercial strategies in the future. Therefore, we will discuss the above aspects in this paper and present our opinions.

Critical assessment of the efficiency of CD34 and CD133 antibodies for enrichment of rabbit hematopoietic stem cells

Rabbits have many hereditary diseases common to humans and are therefore a valuable model for regenerative disease and hematopoietic stem cell (HSC) therapies. Currently, there is no substantial data on the isolation and/or enrichment of rabbit HSCs. This study was initiated to evaluate the efficiency of the commercially available anti-CD34 and anti-CD133 antibodies for the detection and potential enrichment of rabbit HSCs from peripheral blood. PBMCs from rabbit and human blood were labelled with different clones of anti-human CD34 monoclonal antibodies (AC136, 581, and 8G12) and rabbit polyclonal CD34 antibody (pCD34) and anti-human CD133 monoclonal antibodies (AC133 and 293C3). Flow cytometry showed a higher percentage of rabbit CD34⁺ cells labelled by AC136 in comparison to the clone 581 and pCD34 (P < 0.01). A higher percentage of rabbit CD133⁺ cells were also detected by 293C3 compared to the AC133 clone (P < 0.01). Therefore, AC136 clone was used for the indirect immunomagnetic enrichment of rabbit CD34⁺ cells using magnetic-activated cell sorting (MACS). The enrichment of the rabbit CD34⁺ cells after sorting was low in comparison to human samples (2.4% vs. 39.6%). PCR analyses confirmed the efficient enrichment of human CD34⁺ cells and the low expression of CD34 mRNA in rabbit positive fraction. In conclusion, the tested antibodies might be suitable for detection, but not for sorting the rabbit CD34⁺ HSCs and new specific anti-rabbit CD34 antibodies are needed for efficient enrichment of rabbit HSCs. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1278-1289, 2018.

Bone mesenchymal stem cells co-expressing VEGF and BMP-6 genes to combat avascular necrosis of the femoral head

The aim of the present study was to investigate the potential of bone mesenchymal stem cells (BMSCs) treated with a combination of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-6 (BMP-6) genes for the treatment of avascular necrosis of the femoral head (ANFH). Rat BMSCs were isolated and purified using a density gradient centrifugation method. The purity and characteristics of the BMSCs were detected by cell surface antigens identification using flow cytometry. The experimental groups were administered with one of the following adeno-associated virus (AAV) vector constructs: AAV-green fluorescent protein (AAV-GFP), AAV-BMP-6, AAV-VEGF or AAV-VEGF-BMP-6. The expression of VEGF and BMP-6 was detected by reverse transcription-quantitative polymerase chain reaction, western blotting and ELISA assays. The effects of VEGF and BMP-6 on BMSCs were evaluated by angiogenic and osteogenic assays. The transfected BMSCs were combined with a biomimetic synthetic scaffold poly lactide-co-glycolide (PLAGA) and they were then subcutaneously implanted into nude mice. After four weeks, the implants were analyzed with histology and subsequent immunostaining to evaluate the effects of BMSCs on blood vessel and bone formation in vivo. In the AAV-VEGF-BMP-6 group, the expression levels of VEGF and BMP-6 were significantly increased and human umbilical vein endothelial cells tube formation was significantly enhanced compared with other groups. Capillaries and bone formation in the AAV-VEGF-BMP-6 group was significantly higher compared with the other groups. The results of the present study suggest that BMSCs expressing both VEGF and BMP-6 induce an increase in blood vessels and bone formation, which provides theoretical support for ANFH gene therapy.

Cortisol inhibits mTOR signaling in avascular necrosis of the femoral head

BACKGROUND

ANFH is a major health problem, to which long lasting and definitive treatments are lacking. The aim of this study is to study RNA alterations attributed to cortisol-induced ANFH.

METHODS

Rat models were stratified into three groups: in vitro group (n = 20) for molecular biological assays, control group (n = 3), and ANFH group induced using lipopolysaccharide and dexamethasone (n = 3). Bone marrow-derived endothelial progenitor cells (BM-EPCs) were extracted from the rats. An RNA expression array was performed on BM-EPCs, and enriched genes were subject to pathway analysis. In vitro studies following findings of array results were also performed using the isolated BM-EPCs.

RESULTS

Significant alterations in mammalian target of rapamycin (mTOR) and HIF signaling pathways were identified in BM-EPCs of ANFH. By applying cortisol and dexamethasone to BM-EPCs, significant changes in mTOR and HIF elements were identified. The alteration of HIF pathways appeared to be downstream of mTOR signaling. Glucocorticoid receptor (GR) expression was related to glucocorticoid-dependent mRNA expression of mTOR/HIF genes. mTOR-dependent angiogenesis but not anabolism was the target of GR in ANFH. Inhibition of mTOR signaling also induced apoptosis of BM-EPCs via CHOP-dependent DR5 induction in response to GR stimulation.

CONCLUSION

Decreased mTOR signaling in response to GR stimulation leading to downregulated HIF pathway as well as increased apoptosis could be the pathophysiology.

Bone formation in rabbit's leg muscle after autologous transplantation of bone marrow-derived mesenchymal stem cells expressing human bone morphogenic protein-2

BACKGROUND

To test whether autologous transplantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) expressing human bone morphogenic protein-2 (hBMP-2) can produce bone in rabbit leg muscles.

MATERIALS AND METHODS

MSCs were isolated from BM of the iliac crest of rabbits and then infected with lentiviral vectors (LVs) bearing hBMP-2 and green fluorescent protein under the control of the cytomegalovirus (immediate early promoter). Differentiation of transduced MSCs to osteoblasts in vitro was evaluated with an alkaline phosphatase activity assay and immuohistochemistry against osteoblast specific markers. MSCs expressing hBMP-2 were placed in an absorbable gelatin sponge, which was then transplanted into the gastrocnemius of rabbits from which MSCs were isolated. Bone formation was examined by X-ray and histological analysis.

RESULTS

LVs efficiently mediated hBMP-2 gene expression in rabbit BM-MSCs. Ectopic expression of hBMP in these MSCs induced osteoblastic differentiation in vitro. Bone was formed after the MSCs expressing hBMP-2 were transplanted into rabbit muscles.

CONCLUSION

Ectopic expression of hBMP-2 in rabbit MSCs induces them to differentiate into osteoblasts in vitro and to form a bone in vivo.

The increase of VEGF secretion from endothelial progenitor cells post ultrasonic VEGF gene delivery enhances the proliferation and migration of endothelial cells

We investigated the feasibility of exogenous gene expression in endothelial progenitor cells (EPCs) through the use of ultrasonic microbubble transfection (UMT). EPCs originating from porcine peripheral blood were cultured in a medium containing constructed vascular endothelial growth factor (VEGF) pDNA followed by UMT. Simultaneously, comprehensive functional evaluations were conducted to investigate the effects of UMT of the VEGF gene on the EPCs. The results showed that UMT yielded significant VEGF protein expression. VEGF-containing supernatant originating from EPCs post UMT led to significantly enhanced activities of proliferation by more than 20% and migration by approximately 30% in human aortic endothelial cells. The duration of additional secretion of VEGF protein attributable to the exogenous VEGF gene in the EPCs post UMT lasted more than 96 hours. In conclusion, UMT successfully delivers the VEGF gene into porcine EPCs, and VEGF-containing supernatant derived from EPCs post UMT enhances the proliferation and migration of human aortic endothelial cells.

Comparative study of osteogenic potential of a composite scaffold incorporating either endogenous bone morphogenetic protein-2 or exogenous phytomolecule icaritin: an in vitro efficacy study

A local delivery system with sustained and efficient release of therapeutic agents from an appropriate carrier is desirable for orthopedic applications. Novel composite scaffolds made of poly (lactic-co-glycolic acid) with tricalcium phosphate (PLGA/TCP) were fabricated by an advanced low-temperature rapid prototyping technique, which incorporated either endogenous bone morphogenetic protein-2 (BMP-2) (PLGA/TCP/BMP-2) or phytomolecule icaritin (ICT) (PLGA/TCP/ICT) at low, middle and high doses. PLGA/TCP served as control. In vitro degradation, osteogenesis and release tests showed statistical differences among PLGA/TCP/ICT, PLGA/TCP and PLGA/TCP/BMP-2 groups, where PLGA/TCP/ICT had the desired slow release of bioactive icaritin in a dose-dependent manner, whereas there was almost no BMP-2 release from the PLGA/TCP/BMP-2 scaffolds. PLGA/TCP/ICT significantly increased more ALP activity, upregulated mRNA expression of osteogenic genes and enhanced calcium deposition and mineralization in rabbit bone marrow stem cells cultured on scaffolds compared with the other two groups. These results indicate the desired degradation rate, osteogenic capability and release property in PLGA/TCP/ICT composite scaffold, as icaritin preserved its bioactivity and structure after incorporation, while PLGA/TCP/BMP-2 did not show an initially expected osteogenic potential, owing to loss of the original bioactivity of BMP-2 during its incorporation and fabrication procedure. The results suggest that PLGA/TCP composite scaffolds incorporating osteogenic ICT might be a promising approach for bone tissue bioengineering and regeneration.

Genetically modified mesenchymal stem cells for improved islet transplantation

The use of adult stem cells for therapeutic purposes has met with great success in recent years. Among several types of adult stem cells, mesenchymal stem cells (MSCs) derived from bone marrow (BM) and other sources have gained popularity for basic research and clinical applications because of their therapeutic potential in treating a variety of diseases. Because of their tissue regeneration potential and immune modulation effect, MSCs were recently used as cell-based therapy to promote revascularization, increase pancreatic β-cell proliferation, and avoid allograft rejection in islet transplantation. Taking advantage of the recent progress in gene therapy, genetically modified MSCs can further enhance and expand the therapeutic benefit of primary MSCs while retaining their stem-cell-like properties. This review aims to gain a thorough understanding of the current obstacles to successful islet transplantation and discusses the potential role of primary MSCs before or after genetic modification in islet transplantation.