Improved Bone Regeneration With Multiporous PLGA Scaffold and BMP-2-Transduced Human Adipose-Derived Stem Cells by Cell-Permeable Peptide.IMPLANT DENT. 2017;26:4-11. [PMID: 27893514 DOI: 10.1097/ID.0000000000000523]

Adenovirus-Based Gene Therapy for Bone Regeneration: A Comparative Analysis of In Vivo and Ex Vivo BMP2 Gene Delivery

Adenovirus-mediated gene therapy is a promising tool in bone regenerative medicine. In this work, gene-activated matrices (GAMs) composed of (1) polylactide granules (PLA), which serve as a depot for genetic constructs or matrices for cell attachment, (2) a PRP-based fibrin clot, which is a source of growth factors and a binding gel, and (3) a BMP2 gene providing osteoinductive properties were studied. The study aims to compare the effectiveness of in vivo and ex vivo gene therapy based on adenoviral constructs with the BMP2 gene, PLA particles, and a fibrin clot for bone defect healing. GAMs with Ad-BMP2 and MSC(Ad-BMP2) show osteoinductive properties both in vitro and in vivo. However, MSCs incubated with GAMs containing transduced cells showed a more significant increase in osteopontin gene expression, protein production, Alpl activity, and matrix mineralization. Implantation of the studied matrices into critical-size calvarial defects after 56 days promotes the formation of young bone. The efficiency of neoosteogenesis and the volume fraction of newly formed bone tissue are higher with PLA/PRP-MSC(Ad-BMP2) implantation (33%) than PLA/PRP-Ad-BMP2 (28%). Thus, ex vivo adenoviral gene therapy with the BMP2 gene has proven to be a more effective approach than the in vivo delivery of gene constructs for bone regeneration.

Recent advances in gene therapy for bone tissue engineering

Autografting, a major treatment for bone fractures, has potential risks related to the required surgery and disease transmission. Bone morphogenetic proteins (BMPs) are the most common osteogenic factors used for bone-healing applications. However, BMP delivery can have shortcomings such as a short half-life and the high cost of manufacturing the recombinant proteins. Gene delivery methods have demonstrated promising alternative strategies for producing BMPs or other osteogenic factors using engineered cells. These approaches can also enable temporal overexpression and local production of the therapeutic genes in the target tissues. This review addresses recent progress on engineered viral, non-viral, and RNA-mediated gene delivery systems that are being used for bone repair and regeneration. Advances in clustered regularly interspaced short palindromic repeats/Cas9 genome engineering for bone tissue regeneration also is discussed.

Current applications of adipose-derived mesenchymal stem cells in bone repair and regeneration: A review of cell experiments, animal models, and clinical trials

In the field of orthopaedics, bone defects caused by severe trauma, infection, tumor resection, and skeletal abnormalities are very common. However, due to the lengthy and painful process of related surgery, people intend to shorten the recovery period and reduce the risk of rejection; as a result, more attention is being paid to bone regeneration with mesenchymal stromal cells, one of which is the adipose-derived mesenchymal stem cells (ASCs) from adipose tissue. After continuous subculture and cryopreservation, ASCs still have the potential for multidirectional differentiation. They can be implanted in the human body to promote bone repair after induction in vitro, solve the problems of scarce sources and large damage, and are expected to be used in the treatment of bone defects and non-union fractures. However, the diversity of its differentiation lineage and the lack of bone formation potential limit its current applications in bone disease. Here, we concluded the current applications of ASCs in bone repair, especially with the combination and use of physical and biological methods. ASCs alone have been proved to contribute to the repair of bone damage in vivo and in vitro. Attaching to bone scaffolds or adding bioactive molecules can enhance the formation of the bone matrix. Moreover, we further evaluated the efficiency of ASC-committed differentiation in the bone in conditions of cell experiments, animal models, and clinical trials. The results show that ASCs in combination with synthetic bone grafts and biomaterials may affect the regeneration, augmentation, and vascularization of bone defects on bone healing. The specific conclusion of different materials applied with ASCs may vary. It has been confirmed to benefit osteogenesis by regulating osteogenic signaling pathways and gene transduction. Exosomes secreted by ASCs also play an important role in osteogenesis. This review will illustrate the understanding of scientists and clinicians of the enormous promise of ASCs’ current applications and future development in bone repair and regeneration, and provide an incentive for superior employment of such strategies.

A Narrative Review of Cell-Based Approaches for Cranial Bone Regeneration

Current cranial repair techniques combine the use of autologous bone grafts and biomaterials. In addition to their association with harvesting morbidity, autografts are often limited by insufficient quantity of bone stock. Biomaterials lead to better outcomes, but their effectiveness is often compromised by the unpredictable lack of integration and structural failure. Bone tissue engineering offers the promising alternative of generating constructs composed of instructive biomaterials including cells or cell-secreted products, which could enhance the outcome of reconstructive treatments. This review focuses on cell-based approaches with potential to regenerate calvarial bone defects, including human studies and preclinical research. Further, we discuss strategies to deliver extracellular matrix, conditioned media and extracellular vesicles derived from cell cultures. Recent advances in 3D printing and bioprinting techniques that appear to be promising for cranial reconstruction are also discussed. Finally, we review cell-based gene therapy approaches, covering both unregulated and regulated gene switches that can create spatiotemporal patterns of transgenic therapeutic molecules. In summary, this review provides an overview of the current developments in cell-based strategies with potential to enhance the surgical armamentarium for regenerating cranial vault defects.

Current evidence on potential of adipose derived stem cells to enhance bone regeneration and future projection

Injuries to the postnatal skeleton are naturally repaired through successive steps involving specific cell types in a process collectively termed “bone regeneration”. Although complex, bone regeneration occurs through a series of well-orchestrated stages wherein endogenous bone stem cells play a central role. In most situations, bone regeneration is successful; however, there are instances when it fails and creates non-healing injuries or fracture nonunion requiring surgical or therapeutic interventions. Transplantation of adult or mesenchymal stem cells (MSCs) defined by the International Society for Cell and Gene Therapy (ISCT) as CD105+CD90+CD73+CD45-CD34-CD14orCD11b-CD79αorCD19-HLA-DR- is being investigated as an attractive therapy for bone regeneration throughout the world. MSCs isolated from adipose tissue, adipose-derived stem cells (ADSCs), are gaining increasing attention since this is the most abundant source of adult stem cells and the isolation process for ADSCs is straightforward. Currently, there is not a single Food and Drug Administration (FDA) approved ADSCs product for bone regeneration. Although the safety of ADSCs is established from their usage in numerous clinical trials, the bone-forming potential of ADSCs and MSCs, in general, is highly controversial. Growing evidence suggests that the ISCT defined phenotype may not represent bona fide osteoprogenitors. Transplantation of both ADSCs and the CD105^- sub-population of ADSCs has been reported to induce bone regeneration. Most notably, cells expressing other markers such as CD146, AlphaV, CD200, PDPN, CD164, CXCR4, and PDGFRα have been shown to represent osteogenic sub-population within ADSCs. Amongst other strategies to improve the bone-forming ability of ADSCs, modulation of VEGF, TGF-β1 and BMP signaling pathways of ADSCs has shown promising results. The U.S. FDA reveals that 73% of Investigational New Drug applications for stem cell-based products rely on CD105 expression as the “positive” marker for adult stem cells. A concerted effort involving the scientific community, clinicians, industries, and regulatory bodies to redefine ADSCs using powerful selection markers and strategies to modulate signaling pathways of ADSCs will speed up the therapeutic use of ADSCs for bone regeneration.

Orthobiologics with phytobioactive cues: A paradigm in bone regeneration

Bone injuries occur due to various traumatic and disease conditions. Healing of bone injury occurs via a multi-stage intricate process. Body has the potential to rectify most of the bone injuries but some severe traumatic cases with critical size defects may require interventions. Autografts are still considered the "gold standard" for fracture healing but due to limitations associated with it, new alternatives are warranted. The field of orthobiologics has provided novel approaches using scaffolds, bioactive molecules, stem cells for the treatment of bone defects. Phyto-bioactives have been widely used in alternative medicine and folklore practices for curing bone ailments. It is believed that different bioactive constituents in plants work synergistically to give the therapeutic efficacy. Bioactives in plants extracts act upon different signal transduction pathways aiding in bone healing. The present review focuses on the use, chemical composition, mode of delivery, mechanism of action, and possible future strategies of three medicinal plants popularly used in traditional medicine for bone healing: Cissus quadrangularis, Withania somnifera and Tinospora cordifolia. Plants extracts seem to be a natural and non-toxic therapeutic alternative in treating bone injuries. Most of the studies on bone healing for these plants have reported oral administration of the extracts and presented them as a safe alternative without any side effects despite giving higher doses. Forthcoming studies could be directed towards the local delivery of extracts at the defect site. Unification of herbal extracts and orthobiologics could be an interesting direction in the field of bone healing in future. The present review intends to provide a bird's eye view of different strategies used in bone healing, mechanisms involved and future direction of advancements using phytobioactives and orthobiologics.

In Vitro Cultures of Adipose-Derived Stem Cells: An Overview of Methods, Molecular Analyses, and Clinical Applications

Adipose-derived stem cells (ASCs) exhibiting mesenchymal stem cell (MSC) characteristics, have been extensively studied in recent years. Because they have been shown to differentiate into lineages such as osteogenic, chondrogenic, neurogenic or myogenic, the focus of most of the current research concerns either their potential to replace bone marrow as a readily available and abundant source of MSCs, or to employ them in regenerative and reconstructive medicine. There is close to consensus regarding the methodology used for ASC isolation and culture, whereas a number of molecular analyses implicates them in potential therapies of a number of pathologies. When it comes to clinical application, there is a range of examples of animal trials and clinical studies employing ASCs, further emphasizing the advancement of studies leading to their more widespread use. Nevertheless, in vitro studies will most likely continue to play a significant role in ASC studies, both providing the molecular knowledge of their ex vivo properties and possibly serving as an important step in purification and application of those cells in a clinical setting. Therefore, it is important to consider current methods of ASC isolation, culture, and processing. Furthermore, molecular analyses and cell surface properties of ASCs are essential for animal studies, clinical studies, and therapeutic applications of the MSC properties.

Characterizations and interfacial reinforcement mechanisms of multicomponent biopolymer based scaffold

It is difficult for a single component biopolymer to meet the requirements of scaffold at present. The development of multicomponent biopolymer based scaffold provides an effective method to solve the issue based on the advantages of each kind of the biomaterials. However, the compatibility between different components might be very poor due to the difficulties in forming strong interfacial bonding, and thereby significantly degrading the integrated mechanical properties of the scaffold. In recent years, interface phase introduction, surface modification and in situ growth have been the major strategies for enhancing interfacial bonding. This article presents a comprehensive overview on the research in the area of constructing multicomponent biopolymer based scaffold and reinforcing their interfacial properties, and more importantly, the interfacial bonding mechanisms are systematically summarized. Detailly, interface phase introduction can build a bridge between biopolymer and other components to form strong interface bonding with the two phases under the action of interface phase. Surface modification can graft organic molecules or polymers containing functional groups onto other components to crosslink with biopolymer. In situ growth can directly in situ synthesize other components with the action of nucleating agent serving as an adherent platform for the nucleation and growth of other components to biopolymer surface by chemical bonding. In addition, the mechanical properties (including strength and modulus) and biological properties (including bioactivity, cytocompatibility and biosensing in vitro, and tissue compatibility, bone regeneration capacity in vivo) of multicomponent biopolymer based scaffold after interfacial reinforcing are also reviewed and discussed. Finally, suggestions for further research are given with highlighting the need for specific investigations to assess the interface formation, structure, properties, and more in vivo studies of scaffold before applications.

Experimental Investigation of the Adsorption Characteristics of Mixed Coal and Variations of Specific Surface Areas before and after CH4 Adsorption

Tectonic coal is a kind of soft coal that is generated during tectonic movement. Gas outbursts usually occur in seams containing both virgin coal and tectonic coal. To reveal the adsorption characteristics of this type of coal seam (containing both virgin coal and tectonic coal), both tectonic coal and virgin coal were collected from the same longwall face and a series of laboratory tests were conducted, including coal sorption tests and pore specific surface measurements. Both the tectonic coal and virgin coal were crushed into coal powder (0.18–0.25 mm) for the coal sorption tests. In these laboratory tests, different mass ratios between tectonic coal and virgin coal were tested. We found that with the increase of the percentage of tectonic coal, the adsorption volume showed a rising trend, reached its maximum value, and then decreased. The specific surface areas of the mixed coal samples had the same evolution trends as those of the adsorption volume. From the laboratory tests, we found that when the mass ratio of virgin coal to tectonic coal was 1:1, both the adsorption volume and the specific surface areas reached their maximum values. Due to the percentage variation of the tectonic coal in the panel with the advancement of the longwall face, when the tectonic coal accounted for 50% of the total coal, the gas content would rise. Thus, proper measures should be adopted for outburst hazards control. The mathematical model between the change of specific surface area and the stress and strain of pore expansion before and after gas adsorption was established, and the relationship between the change of pore structure and gas emission before and after gas adsorption was obtained. It provides a theoretical basis for further research on coal and gas outburst mechanisms.

Poly-l-lysine-coated PLGA/poly(amino acid)-modified hydroxyapatite porous scaffolds as efficient tissue engineering scaffolds for cell adhesion, proliferation, and differentiation

Ideal bone tissue engineering scaffolds should be biocompatible, biodegradable, and mechanically robust and have the ability to regulate cell function.

Enhancement in sustained release of antimicrobial peptide and BMP-2 from degradable three dimensional-printed PLGA scaffold for bone regeneration

One of the goals of bone tissue engineering is to create scaffolds with well-defined, inter-connected pores, excellent biocompatibility and osteoinductive ability. Three-dimensional (3D)-printed polymer scaffold coated with bioactive peptide are an effective approach to fabricating ideal bone tissue engineering scaffolds for bone defect repair. However, the current strategy of adding bioactive peptides generally cause degradation to the polymer materials or damage the bioactivity of the biomolecules. Thus, in this study, we used a biomimetic process via poly(dopamine) coating to prepare functional 3D PLGA porous scaffolds with immobilized BMP-2 and ponericin G1 that efficiently regulate the osteogenic differentiation of preosteoblasts (MC3T3-E1) and simultaneously inhibit of pathogenic microbes, thereby enhancing biological activity. In this study, we analysed a 3D PLGA porous scaffold by scanning electron microscopy, water contact angle measurements, and materials testing. Subsequently, we examined the adsorption, release and in vitro antimicrobial activity of the 3D PLGA. Surface characterization showed that poly(dopamine) surface modification could more efficiently mediate the immobilization of BMP-2 and ponericin G1 onto the scaffold surfaces than physical adsorption, and that ponericin G1-immobilized 3D PLGA scaffolds were able to maintain long-term antibacterial activity. We evaluated the influence on cell adhesion, proliferation and differentiation by culturing MC3T3-E1 cells on different modified 3D PLGA scaffolds in vitro. The biological results indicate that MC3T3-E1 cell attachment and proliferation on BMP-2/ponericin G1-immobilized 3D PLGA scaffolds were much higher than those on other groups. Calcium deposition, and gene expression results showed that the osteogenic differentiation of cells was effectively improved by loading the 3D PLGA scaffold with BMP-2 and ponericin G1. In summary, our findings indicated that the polydopamine-assisted surface modification method can be a useful tool for grafting biomolecules onto biodegradable implants, and the dual release of BMP-2 and ponericin G1 can enhance the osteointegration of bone implants and simultaneously inhibit of pathogenic microbes. Therefore, we conclude that the BMP-2/ponericin G1-loaded PLGA 3D scaffolds are versatile and biocompatible scaffolds for bone tissue engineering.

One of the goals of bone tissue engineering is to create scaffolds with well-defined, inter-connected pores, excellent biocompatibility and osteoinductive ability.

Enhancement of osteogenesis of rabbit bone marrow derived mesenchymal stem cells by transfection of human BMP-2 and EGFP recombinant adenovirus via Wnt signaling pathway

Bone marrow mesenchymal stem cells (BMSCs) are considered the most important seed cells in bone tissue engineering. The present study aimed to investigate the potential of rabbit BMSCs in osteogenesis after the transfection of human BMP-2 and EGFP recombinant adenovirus. Rabbit BMSCs were isolated and the surface stem cell makers, including CD29, CD44 and CD45 were detected by flow cytometry. The expression of BMP-2 mRNA and protein in BMSCs were detected by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. After an induction with osteogenic medium, the alkaline phosphatase (ALK) activity at 7 days, the type I collagen at 14 days, and the calcium nodules at 21 days were performed using an ALK activity kit, immunohistochemical staining and alizarin red S staining, respectively. The expression levels of proteins related to the Wnt signaling pathway were detected by western blot analysis. The positive rates of CD29, CD44 and CD45 were 62.92±1.99, 93.55±0.99 and 0.21±0.12%. The expression of BMP-2 mRNA and protein was significantly upregulated in Ad-BMP-2/EGFP transfected BMSCs. Furthermore, Ad-BMP-2/EGFP induced ALP activity, promoted the production of type I collagen and calcium nodule formation in rabbit BMSCs. The levels of β-catenin, cyclin D1, Runx2 and c-myc were upregulated in Ad-hBMP-2/EGFP transfected BMSCs, while the level of GSK3β was significantly decreased. Results also indicated that the overexpression of BMP-2 by Ad-hBMP-2/EGFP enhanced the osteogenic differentiation ability of cultured rabbit BMSCs via stimulating the Wnt signaling pathway with the accumulation of β-catenin and suppression of GSK3β. The Ad-hBMP-2/EGFP transfected rabbit BMSCs are expected to be a good seed cell in bone tissue engineering.

Repair of bone defects in rat radii with a composite of allogeneic adipose-derived stem cells and heterogeneous deproteinized bone

Background

In the bone tissue engineering domain, seed cells, scaffold and cell-scaffold composites are three focuses. In this study, the feasibility of using allogeneic adipose-derived stem cells(ADSCs) combined with heterogeneous deproteinized bone (HDB) to repair segmental radial defects was investigated by observing the repair of the defect area.

Methods

ADSCs were cultured in vitro, purified, antigen-detected and osteogenic differentiation potency-measured; then, the ADSCs of the third generation were seeded into HDB to prepare an ADSCs-HDB composite partly with osteogenesis induced cells. Sixty Wistar rats were randomly divided into four groups with 15 in each group. A bone defect (4 mm in length) was created at the left radius in each rat. Two kinds of ADSCs-HDB composites were implanted in the ADSCs osteogenesis group or ADSCs group; HDB was implanted in the negative control group; nothing was filled in the blank control group. The bone defect repair was evaluated by gross observation, molybdenum target X-ray examination and histological analyses after surgery.

Results

Gross observation: the bone defect area was completely filled and difficult to recognize in the ADSCs osteogenesis group. The connection of the ADSCs group was strong, but the implants were clearly identifiable. The joints of the negative control group were slightly thick but the connection was unstable. In the blank control group, kermesinus tissue was between the two ends and bones were not connected after 8 weeks. Molybdenum target X-ray examinations: In the ADSCs osteogenesis group, evident bridges in the graft were observed in the defects in the fourth week; the defects were filled with new bone completely and a marrow cavity appeared at 8 weeks. In the ADSCs group, there were some callus formations, but the radial defect was still obvious at 8 weeks. In the negative control group, fracture lines were clear. In the blank control group, no osseous bridges were observed, which resulted in bone nonunion eventually in 8 weeks. There were significant differences in the callus density between experimental groups and the blank control group at 4 and 8 weeks (P < 0.01). Histological measures showed that the rate and quality of the new bone formation and remodelling was significantly different between the experimental and control groups.

Conclusions

A composite of ADSCs-HDB has a strong osteogenic ability. It can repair segmental bone defects well and is promising to serve as grafting material in bone tissue engineering.

Synergistic delivery of bFGF and BMP-2 from poly(l-lactic-co-glycolic acid)/graphene oxide/hydroxyapatite nanofibre scaffolds for bone tissue engineering applications

One of the goals of bone tissue engineering is to create scaffolds with excellent biocompatibility, osteoinductive ability and mechanical properties.

Enhancing Cell Proliferation and Osteogenic Differentiation of MC3T3-E1 Pre-osteoblasts by BMP-2 Delivery in Graphene Oxide-Incorporated PLGA/HA Biodegradable Microcarriers

Lack of bioactivity has seriously restricted the development of biodegradable implants for bone tissue engineering. Therefore, surface modification of the composite is crucial to improve the osteointegration for bone regeneration. Bone morphogenetic protein-2 (BMP-2), a key factor in inducing osteogenesis and promoting bone regeneration, has been widely used in various clinical therapeutic trials. In this study, BMP-2 was successfully immobilized on graphene oxide-incorporated PLGA/HA (GO-PLGA/HA) biodegradable microcarriers. Our study demonstrated that the graphene oxide (GO) facilitated the simple and highly efficient immobilization of peptides on PLGA/HA microcarriers within 120 min. To further test in vitro, MC3T3-E1 cells were cultured on different microcarriers to observe various cellular activities. It was found that GO and HA significantly enhanced cell adhesion and proliferation. More importantly, the immobilization of BMP-2 onto the GO-PLGA/HA microcarriers resulted in significantly greater osteogenic differentiation of cells in vitro, as indicated by the alkaline phosphate activity test, quantitative real-time polymerase chain reaction analysis, immunofluorescence staining and mineralization on the deposited substrates. Findings from this study revealed that the method to use GO-PLGA/HA microcarriers for immobilizing BMP-2 has a great potential for the enhancement of the osseointegration of bone implants.

Glycosaminoglycan-based resorbable polymer composites in tissue refurbishment

Regeneration of tissue structure with the aid of bioactive polymer matrices/composites and scaffolds for respective applications is one of the emerging areas of biomedical engineering. Recent advances in conjugated glycosaminoglycan (GAG) hybrids using natural and synthetic polymers have opened new avenues for producing a wide variety of resorbable polymer matrices. These hybrid scaffolds are low-immunogenic, highly biocompatible and biodegradable with incredible mechanical and tensile properties. GAG-based resorbable polymeric matrices are being exploited in migration of stem cells, cartilage and bone replacement/regeneration and production of scaffolds for various tissue engineering applications. In the current review, we will discuss the role of GAG-based resorbable polymer matrices in the field of regenerative medicine.

Improving osteogenesis of PLGA/HA porous scaffolds based on dual delivery of BMP-2 and IGF-1 via a polydopamine coating

To engineer bone tissue, an ideal biodegradable implant should be biocompatible, biodegradable, osteoinductive and osteoconductive.