Adipose-derived stem cells and BMP-2 delivery in chitosan-based 3D constructs to enhance bone regeneration in a rat mandibular defect model

Rapid osteoinduction of human adipose-derived stem cells grown on bioactive surfaces and stimulated by chemically modified media flow

Adipose-derived stem cells (ASCs) provide an ample, easily accessible source of multipotent cells, an alternative to bone marrow-derived stromal cells (BMSCs), capable of differentiating into osteoblasts. However, the osteogenic potential of ASCs is reportedly lower than that of BMSCs and protocols to effectively differentiate ASCs into osteoblasts are in high demand. Here, we present novel strategies for effective osteogenic differentiation of human ASCs by combining their culture on bioactive growth surfaces with their treatment with specific supplements in osteogenic medium and application of fluid shear stress. Human ASCs were cultured on PLGA-based composites containing 50 wt% sol-gel bioactive glasses (SBGs) from the SiO2-CaO±P2O5 system, either unmodified or modified with 5 wt% ZnO or SrO. The osteogenic medium was supplemented with recombinant human bone morphogenetic protein 2 (BMP-2), MEK1/2 kinase inhibitor (PD98059) and indirect Smurf1 inhibitor (Phenamil). Fluid shear stress was applied with a standard horizontal rocker. ASC culture on SBG-PLGA composites along with the osteogenic medium supplements enhanced the expression of both early and late osteogenic markers. Modification of SBG with either SrO or ZnO further enhanced osteogenic gene expression compared to ASCs cultured on composites containing unmodified SBGs. Notably, the application of fluid shear stress synergistically strengthened the osteogenic effects of bioactive composites and medium supplements. We also show that the presented culture strategies can drive ASCs toward osteoblastic cells in a 3-day culture period and provide mineralizing osteoblasts through a short, 7-day ASC preculture on bioactive composites. Our results also indicate that the applied osteogenic treatment leads to the phosphorylation of β-catenin and CREB or the COX-2 expression. We believe the presented strategies are feasible for rapid ASC differentiation to early osteoblasts or mineralizing osteoblastic cells for various potential cell-based bone regeneration therapies.

An Integrated Optogenetic and Bioelectronic Platform for Regulating Cardiomyocyte Function

Bioelectronic medicine is emerging as a powerful approach for restoring lost endogenous functions and addressing life-altering maladies such as cardiac disorders. Systems that incorporate both modulation of cellular function and recording capabilities can enhance the utility of these approaches and their customization to the needs of each patient. Here we report an integrated optogenetic and bioelectronic platform for stable and long-term stimulation and monitoring of cardiomyocyte function in vitro. Optical inputs are achieved through the expression of a photoactivatable adenylyl cyclase, that when irradiated with blue light causes a dose-dependent and time-limited increase in the secondary messenger cyclic adenosine monophosphate with subsequent rise in autonomous cardiomyocyte beating rate. Bioelectronic readouts are obtained through a multi-electrode array that measures real-time electrophysiological responses at 32 spatially-distinct locations. Irradiation at 27 µW mm-2 results in a 14% elevation of the beating rate within 20-25 min, which remains stable for at least 2 h. The beating rate can be cycled through "on" and "off" light states, and its magnitude is a monotonic function of irradiation intensity. The integrated platform can be extended to stretchable and flexible substrates, and can open new avenues in bioelectronic medicine, including closed-loop systems for cardiac regulation and intervention, for example, in the context of arrythmias.

Use of Plant Extracts in Polymeric Scaffolds in the Regeneration of Mandibular Injuries

Severe loss of bone mass may require grafting, and, among the alternatives available, there are natural biomaterials that can act as scaffolds for the cell growth necessary for tissue regeneration. Collagen and elastin polymers are a good alternative due to their biomimetic properties of bone tissue, and their characteristics can be improved with the addition of polysaccharides such as chitosan and bioactive compounds such as jatoba resin and pomegranate extract due to their antigenic actions. The aim of this experimental protocol was to evaluate bone neoformation in experimentally made defects in the mandible of rats using polymeric scaffolds with plant extracts added. Thirty rats were divided into group 1, with a mandibular defect filled with a clot from the lesion and no graft implant (G1-C, n = 10); group 2, filled with collagen/chitosan/jatoba resin scaffolds (G2-CCJ, n = 10); and group 3, with collagen/nanohydroxyapatite/elastin/pomegranate extract scaffolds (G3-CHER, n = 10). Six weeks after surgery, the animals were euthanized and samples from the surgical areas were submitted to macroscopic, radiological, histological, and morphometric analysis of the mandibular lesion repair process. The results showed no inflammatory infiltrates in the surgical area, indicating good acceptance of the scaffolds in the microenvironment of the host area. In the control group (G1), there was a predominance of reactive connective tissue, while in the grafted groups (G2 and G3), there was bone formation from the margins of the lesion, but it was still insufficient for total bone repair of the defect within the experimental period standardized in this study. The histomorphometric analysis showed that the mean percentage of bone volume formed in the surgical area of groups G1, G2, and G3 was 17.17 ± 2.68, 27.45 ± 1.65, and 34.07 ± 0.64 (mean ± standard deviation), respectively. It can be concluded that these scaffolds with plant extracts added can be a viable alternative for bone repair, as they are easily manipulated, have a low production cost, and stimulate the formation of new bone by osteoconduction.

Preclinical Evaluation of Bioactive Scaffolds for the Treatment of Mandibular Critical-Sized Bone Defects: A Systematic Review

This systematic review evaluated current in vivo research on regenerating critical-sized mandibular defects and discussed methodologies for mandibular bone tissue engineering. Out of the 3650 articles initially retrieved, 88 studies were included, and all studies that used a scaffold reported increased bone formation compared to negative controls. Combining scaffolds with growth factors and mesenchymal stem cells improved bone formation and healing. Bone morphogenic proteins were widely used and promoted significant bone formation compared to controls. However, discrepancies between studies exist due to the various methodologies and outcome measures used. The use of scaffolds with bioactive molecules and/or progenitor cells enhances success in mandibular bone engineering. Scaffold-based mandibular bone tissue engineering could be introduced into clinical practice due to its proven safety, convenience, and cost-effectiveness.

DPSC-Derived Extracellular Vesicles Promote Rat Jawbone Regeneration

Repair and functional reconstruction of large jawbone defects remain one of the challenges in the field of head and neck surgery. The recent progress in tissue engineering technologies and stem cell biology has significantly promoted the development of regenerative reconstruction of jawbone defects. The multiple trophic activities of extracellular vesicles (EVs) produced by mesenchymal stem cells (MSCs) may play a critical role in their therapeutic effects. Accumulating evidence has shown the promise of dental pulp stem cells (DPSCs) in bone regeneration, but less is known about the regenerative effects of DPSC-EVs on jawbone defects. The purpose of this study is to explore the osteogenic effects of DPSC-EVs on jawbone marrow-derived MSCs (JB-MSCs) in vitro and their osteoinductive effects in a mandibular bone defect model in rats. Our results showed that JB-MSCs could efficiently uptake DPSC-EVs, which in turn significantly promoted the expression of osteogenic genes, such as runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), and osteocalcin (OCN), as well as the osteogenic differentiation capability of JB-MSCs. Meanwhile, we found that the pro-osteogenic effect in vitro induced by DPSC-EVs was comparable to that induced by BMP-2 (bone morphogenetic protein 2), currently the only Food and Drug Administration-approved osteoinductive growth factor. In vivo, animals that were locally treated with DPSC-EVs laden with a commercially available collagen membrane exhibited a relatively fast wound closure and increased new bone density at the mandible defects. Our results provide evidence for the osteogenic and osteoinductive effects of DPSC-EVs on jawbone regeneration. Due to the accessibility, rapid proliferation, and osteogenic propensity of DPSCs, DPSC-EVs may represent a safe cell-free therapeutic approach for craniofacial bone regeneration.

Advanced Hydrogel systems for mandibular reconstruction

Mandibular defect becomes a prevalent maxillofacial disease resulting in mandibular dysfunctions and huge psychological burdens to the patients. Considering the routine presence of oral contaminations and aesthetic restoration of facial structures, the current clinical treatments are however limited, incapable to reconstruct the structural integrity and regeneration, spurring the need for cost-effective mandibular tissue engineering. Hydrogel systems possess great merit for mandibular reconstruction with precise involvement of cells and bioactive factors. In this review, current clinical treatments and distinct mode(s) of mandible formation and pathological resorption are summarized, followed by a review of hydrogel-related mandibular tissue engineering, and an update on the advanced fabrication of hydrogels with improved mechanical property, antibacterial ability, injectable form, and 3D bioprinted hydrogel constructs. The exploration of advanced hydrogel systems will lay down a solid foundation for a bright future with more biocompatible, effective, and personalized treatment in mandibular reconstruction.

Repair of a Rat Mandibular Bone Defect by Hypertrophic Cartilage Grafts Engineered From Human Fractionated Adipose Tissue

Background: Devitalized bone matrix (DBM) is currently the gold standard alternative to autologous bone grafting in maxillofacial surgery. However, it fully relies on its osteoconductive properties and therefore requires defects with healthy bone surrounding. Fractionated human adipose tissue, when differentiated into hypertrophic cartilage in vitro, was proven reproducibly osteogenic in vivo, by recapitulating endochondral ossification (ECO). Both types of bone substitutes were thus compared in an orthotopic, preclinical mandibular defect model in rat.

Methods: Human adipose tissue samples were collected and cultured in vitro to generate disks of hypertrophic cartilage. After hypertrophic induction, eight samples from two donors were implanted into a mandible defect in rats, in parallel to Bio-Oss® DBM granules. After 12 weeks, the mandible samples were harvested and evaluated by Micro-CT and histology.

Results: Micro-CT demonstrated reproducible ECO and complete restoration of the mandibular geometry with adipose-based disks, with continuous bone inside and around the defect, part of which was of human (donor) origin. In the Bio-Oss® group, instead, osteoconduction from the border of the defect was observed but no direct connection of the granules with the surrounding bone was evidenced. Adipose-based grafts generated significantly higher mineralized tissue volume (0.57 ± 0.10 vs. 0.38 ± 0.07, n = 4, p = 0.03) and newly formed bone (18.9 ± 3.4% of surface area with bone tissue vs. 3 ± 0.7%, p < 0.01) than Bio-Oss^®.

Conclusion: Our results provide a proof-of-concept that adipose-based hypertrophic cartilage grafts outperform clinical standard biomaterials in maxillofacial surgery.

Design of chemically defined synthetic substrate surfaces for the in vitro maintenance of human pluripotent stem cells: A review

Human pluripotent stem cells (hPSCs) have the potential of long-term self-renewal and differentiation into nearly all cell types in vitro. Prior to the downstream applications, the design of chemically defined synthetic substrates for the large-scale proliferation of quality-controlled hPSCs is critical. Although great achievements have been made, Matrigel and recombinant proteins are still widely used in the fundamental research and clinical applications. Therefore, much effort is still needed to improve the performance of synthetic substrates in the culture of hPSCs, realizing their commercial applications. In this review, we summarized the design of reported synthetic substrates and especially their limitations in terms of cell culture. Moreover, much attention was paid to the development of promising peptide displaying surfaces. Besides, the biophysical regulation of synthetic substrate surfaces as well as the three-dimensional culture systems were described.

Advances in Engineered Three-Dimensional (3D) Body Articulation Unit Models

Indeed, the body articulation units, commonly referred to as body joints, play significant roles in the musculoskeletal system, enabling body flexibility. Nevertheless, these articulation units suffer from several pathological conditions, such as osteoarthritis (OA), rheumatoid arthritis (RA), ankylosing spondylitis, gout, and psoriatic arthritis. There exist several treatment modalities based on the utilization of anti-inflammatory and analgesic drugs, which can reduce or control the pathophysiological symptoms. Despite the success, these treatment modalities suffer from major shortcomings of enormous cost and poor recovery, limiting their applicability and requiring promising strategies. To address these limitations, several engineering strategies have been emerged as promising solutions in fabricating the body articulation as unit models towards local articulation repair for tissue regeneration and high-throughput screening for drug development. In this article, we present challenges related to the selection of biomaterials (natural and synthetic sources), construction of 3D articulation models (scaffold-free, scaffold-based, and organ-on-a-chip), architectural designs (microfluidics, bioprinting, electrospinning, and biomineralization), and the type of culture conditions (growth factors and active peptides). Then, we emphasize the applicability of these articulation units for emerging biomedical applications of drug screening and tissue repair/regeneration. In conclusion, we put forward the challenges and difficulties for the further clinical application of the in vitro 3D articulation unit models in terms of the long-term high activity of the models.

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.

Rational design of hydrogels to enhance osteogenic potential

Bone tissue engineering (BTE) encompasses the field of biomaterials, cells, and bioactive molecules to successfully guide the growth and repair of bone tissue. Current BTE strategies rely on delivering osteogenic molecules or cells via scaffolding materials. However, growth factor- and stem cell-based treatments have several limitations, such as source restriction, low stability, difficulties in predicting long-term efficacy, and high costs, among others. These issues have promoted the development of material-based therapy with properties of accessibility, high stability, tunable efficacy, and low-cost production. Hydrogels are widely used in BTE applications because of their unique hydrophilic nature and tunable physicochemical properties to mimic the native bone environment. However, current hydrogel materials are not ideal candidates due to minimal osteogenic capability on their own. Therefore, recent studies of BTE hydrogels attempt to counterbalance these issues by modifying their biophysical properties. In this article, we review recent progress in the design of hydrogels to instruct osteogenic potential, and present strategies developed to precisely control its bone healing properties.

Landscape of transcription and expression regulated by DNA methylation related to age of donor and cell passage in adipose-derived mesenchymal stem cells

Adipose-derived mesenchymal stem cells (ADSCs) are pluripotent stromal cells that can differentiate into a variety of cell types, including skin cells. High-throughput sequencing was performed on cells of different ages and cell passage, obtaining their methylation, mRNA expression, and protein profile data. The stemness of each sample was then calculated using the TCGAbiolinks package in R. Co-expression modules were identified using WGCNA, and a crosstalk analysis was performed on the corresponding modules. The ClusterProfile package was used for the functional annotation of module genes. Finally, the regulatory network diagram was visualized using the Cytoscape software. First, a total of 16 modules were identified, where 3 modules were screened that were most relevant to the phenotype. 29 genes were screened in combination of the RNA seq, DNA methylation seq and protein iTRAQ. Finally, a comprehensive landscape comprised of RNA expression, DNA methylation and protein profiles of age relevant ADSCs was constructed. Overall, the different omics of ADSCs were comprehensively analyzed in order to reveal mechanisms pertaining to their growth and development. The effects of age, cell passage, and stemness on the therapeutic effect of ADSCs were explored. Additionally, a theoretical basis for selecting appropriate ADSC donors for regenerative medicine was provided.

Bioinspired channeled, rhBMP-2-coated β-TCP scaffolds with embedded autologous vascular bundles for increased vascularization and osteogenesis of prefabricated tissue-engineered bone

To date, the recovery of large bone defects is a major clinical challenge despite the availability of numerous therapeutic procedures including tissue engineering. Although there is a pressing need for large tissue-engineered constructs, inadequate vascularization remains an insurmountable barrier for successful clinical translation. Considering that vascularization is a prerequisite for osteogenesis, we proposed an advanced design of large customized porous β-tricalcium phosphate (TCP) scaffolds with biomimetic vascular hierarchy which upon embedding of femoral axial vascular bundles significantly improved overall vascularity of the scaffolds. Such scaffolds also promoted osteogenesis when they were coated with recombinant bone morphogenetic protein-2 (rhBMP-2). Compared to the conventional TCP scaffolds (S), the newly designed multi-channeled β-TCP (CS) scaffolds led to adequate blood vessels and bone-like tissue formation throughout their porous hierarchy within 4 weeks of implantation. Especially, the scaffolds coated with rhBMP-2 and embedded with flow-through vascular bundle (FVB) were able to form more uniform vascularized bone within 2 weeks post-implantation. Based on the clinical, radiographic, angiographic and histological assessments, the newly designed multi-channeled scaffolds were found to be promising for successful recovery of large bone defects.

Tissue engineering applications in otolaryngology-The state of translation

While tissue engineering holds significant potential to address current limitations in reconstructive surgery of the head and neck, few constructs have made their way into routine clinical use. In this review, we aim to appraise the state of head and neck tissue engineering over the past five years, with a specific focus on otologic, nasal, craniofacial bone, and laryngotracheal applications. A comprehensive scoping search of the PubMed database was performed and over 2000 article hits were returned with 290 articles included in the final review. These publications have addressed the hallmark characteristics of tissue engineering (cellular source, scaffold, and growth signaling) for head and neck anatomical sites. While there have been promising reports of effective tissue engineered interventions in small groups of human patients, the majority of research remains constrained to in vitro and in vivo studies aimed at furthering the understanding of the biological processes involved in tissue engineering. Further, differences in functional and cosmetic properties of the ear, nose, airway, and craniofacial bone affect the emphasis of investigation at each site. While otolaryngologists currently play a role in tissue engineering translational research, continued multidisciplinary efforts will likely be required to push the state of translation towards tissue-engineered constructs available for routine clinical use.

LEVEL OF EVIDENCE

NA.

Systematic scoping review of mandibular bone tissue engineering

Tissue engineering is a promising alternative that may facilitate bony regeneration in small defects in compromised host tissue as well as large mandibular defects. This scoping systematic review was therefore designed to assess in vivo research on its use in the reconstruction of mandibular defects in animal models. A total of 4524 articles were initially retrieved using the search algorithm. After screening of the titles and abstracts, 269 full texts were retrieved, and a total of 72 studies included. Just two of the included studies employed osteonecrosis as the model of mandibular injury. All the rest involved the creation of a critical defect. Calcium phosphates, especially tricalcium phosphate and hydroxyapatite, were the scaffolds most widely used. All the studies that used a scaffold reported increased formation of bone when compared with negative controls. When combined with scaffolds, mesenchymal stem cells (MSC) increased the formation of new bone and improved healing. Various growth factors have been studied for their potential use in the regeneration of the maxillofacial complex. Bone morphogenic proteins (BMP) were the most popular, and all subtypes promoted significant formation of bone compared with controls. Whilst the studies published to date suggest a promising future, our review has shown that several shortfalls must be addressed before the findings can be translated into clinical practice. A greater understanding of the underlying cellular and molecular mechanisms is required to identify the optimal combination of components that are needed for predictable and feasible reconstruction or regeneration of mandibular bone. In particular, a greater understanding of the biological aspects of the regenerative triad is needed before we can to work towards widespread translation into clinical practice.

Bilaminar Chitosan Scaffold for Sellar Floor Repair in Transsphenoidal Surgery

Background

Endoscopic endonasal transsphenoidal surgery (EETS) is a standard technique used to approach sellar tumors. It is relatively safe, minimally invasive and carries a low risk of complications. However, one of the common complications reported with this technique is CSF leakage which causes morbidity, an increase in recovery time and hospital costs. This complication usually occurs from violation of the diaphragma sellae and a defect in the structures of the sellar floor or incomplete repair. In this article we report the first case with the use of a novel bilaminar chitosan scaffold which can be potentially used in the repair of the sellar floor, primarily aiming to the bony part of this structure.

Case Presentation

After a personalized design employing a tissue engineering strategy, we reconstructed the sellar floor in a 65-year-old woman who had undergone EETS for a pituitary adenoma with progressive bilateral visual loss. To repair the bony defect of the sellar floor, we used a novel bilaminar chitosan scaffold. The patient had an unremarkable postoperative course with no evidence of CSF leak. The polymer was well tolerated without toxicity, infection or complications. After 2 years of follow up the patient remains neurologically intact, and in good endocrinological status.

Conclusion

This is the first report of the use of this biomaterial and its biocompatibility in a clinical setting for the repair of the sellar floor during EETS. Our experience with chitosan bilaminar scaffold and in several preclinical studies in the literature have demonstrated good biocompatibility and effective bioengineered bone regeneration due to its excellent osteoconductive properties, this study pretends to be one landmark for further clinical research and larger case series with the use of this personalized tissue engineering materials in order to see they real efficacy to increase the surgeon armamentarium.

Advances in Pluripotent Stem Cells: History, Mechanisms, Technologies, and Applications

Over the past 20 years, and particularly in the last decade, significant developmental milestones have driven basic, translational, and clinical advances in the field of stem cell and regenerative medicine. In this article, we provide a systemic overview of the major recent discoveries in this exciting and rapidly developing field. We begin by discussing experimental advances in the generation and differentiation of pluripotent stem cells (PSCs), next moving to the maintenance of stem cells in different culture types, and finishing with a discussion of three-dimensional (3D) cell technology and future stem cell applications. Specifically, we highlight the following crucial domains: 1) sources of pluripotent cells; 2) next-generation in vivo direct reprogramming technology; 3) cell types derived from PSCs and the influence of genetic memory; 4) induction of pluripotency with genomic modifications; 5) construction of vectors with reprogramming factor combinations; 6) enhancing pluripotency with small molecules and genetic signaling pathways; 7) induction of cell reprogramming by RNA signaling; 8) induction and enhancement of pluripotency with chemicals; 9) maintenance of pluripotency and genomic stability in induced pluripotent stem cells (iPSCs); 10) feeder-free and xenon-free culture environments; 11) biomaterial applications in stem cell biology; 12) three-dimensional (3D) cell technology; 13) 3D bioprinting; 14) downstream stem cell applications; and 15) current ethical issues in stem cell and regenerative medicine. This review, encompassing the fundamental concepts of regenerative medicine, is intended to provide a comprehensive portrait of important progress in stem cell research and development. Innovative technologies and real-world applications are emphasized for readers interested in the exciting, promising, and challenging field of stem cells and those seeking guidance in planning future research direction.

Glycosaminoglycan-based biomaterials for growth factor and cytokine delivery: Making the right choices

Controlled, localized drug delivery is a long-standing goal of medical research, realization of which could reduce the harmful side-effects of drugs and allow more effective treatment of wounds, cancers, organ damage and other diseases. This is particularly the case for protein "drugs" and other therapeutic biological cargoes, which can be challenging to deliver effectively by conventional systemic administration. However, developing biocompatible materials that can sequester large quantities of protein and release them in a sustained and controlled manner has proven challenging. Glycosaminoglycans (GAGs) represent a promising class of bio-derived materials that possess these key properties and can additionally potentially enhance the biological effects of the delivered protein. They are a diverse group of linear polysaccharides with varied functionalities and suitabilities for different cargoes. However, most investigations so far have focused on a relatively small subset of GAGs - particularly heparin, a readily available, promiscuously-binding GAG. There is emerging evidence that for many applications other GAGs are in fact more suitable for regulated and sustained delivery. In this review, we aim to illuminate the beneficial properties of various GAGs with reference to specific protein cargoes, and to provide guidelines for informed choice of GAGs for therapeutic applications.

Transplantation of dedifferentiated fat cells combined with a biodegradable type I collagen-recombinant peptide scaffold for critical-size bone defects in rats

Tissue engineering is a promising approach to supplement existing treatment strategies for craniofacial bone regeneration. In this study, a type I collagen scaffold made from a recombinant peptide (RCP) with an Arg-Gly-Asp motif was developed, and its effect on regeneration in critical-size mandibular bone defects was evaluated. Additionally, the combined effect of the scaffold and lipid-free dedifferentiated fat (DFAT) cells was assessed. Briefly, DFAT cells were separated from mature adipocytes by using a ceiling culture technique based on buoyancy. A 3 cm × 4 cm critical-size bone defect was created in the rat mandible, and regeneration was evaluated by using RCP with DFAT cells. Then, cultured DFAT cells and adipose-derived stem cells (ASCs) were seeded onto RCP scaffolds (DFAT/RCP and ASC/RCP) and implanted into the bone defects. Micro-computed tomography imaging at 8 weeks after implantation showed significantly greater bone regeneration in the DFAT/RCP group than in the ASC/RCP and RCP-alone groups. Similarly, histological analysis showed significantly greater bone width in the DFAT/RCP group than in the ASC/RCP and RCP-alone groups. These findings suggest that DFAT/RCP is effective for bone formation in critical-size bone defects and that DFAT cells are a promising source for bone regeneration.

Application of Chitosan in Bone and Dental Engineering

Chitosan is a deacetylated polysaccharide from chitin, the natural biopolymer primarily found in shells of marine crustaceans and fungi cell walls. Upon deacetylation, the protonation of free amino groups of the d-glucosamine residues of chitosan turns it into a polycation, which can easily interact with DNA, proteins, lipids, or negatively charged synthetic polymers. This positive-charged characteristic of chitosan not only increases its solubility, biodegradability, and biocompatibility, but also directly contributes to the muco-adhesion, hemostasis, and antimicrobial properties of chitosan. Combined with its low-cost and economic nature, chitosan has been extensively studied and widely used in biopharmaceutical and biomedical applications for several decades. In this review, we summarize the current chitosan-based applications for bone and dental engineering. Combining chitosan-based scaffolds with other nature or synthetic polymers and biomaterials induces their mechanical properties and bioactivities, as well as promoting osteogenesis. Incorporating the bioactive molecules into these biocomposite scaffolds accelerates new bone regeneration and enhances neovascularization in vivo.

Review of the Pathways Involved in the Osteogenic Differentiation of Adipose-Derived Stem Cells

Grafts and prosthetic materials used for the repair of bone defects are often accompanied by comorbidity and rejection. Therefore, there is an immense need for novel approaches to combating the issues surrounding such defects. Because of their accessibility, substantial proportion, and osteogenic differentiation potential, adipose-derived stem cells (ASCs) make for an ideal source of bone tissue in regenerative medicine. However, efficient induction of ASCs toward an osteoblastic lineage in vivo is met with challenges, and many signaling pathways must come together to secure osteoblastogenesis. Among them are bone morphogenic protein, wingless-related integration site protein, Notch, Hedgehog, fibroblast growth factor, vascular endothelial growth factor, and extracellular regulated-signal kinase. The goal of this literature review is to conglomerate the present research on these pathways to formulate a better understanding of how ASCs are most effectively transformed into bone in the context of tissue engineering.

Comparison of osteogenic differentiation induced by siNoggin and pBMP-2 delivered by lipopolysaccharide-amine nanopolymersomes and underlying molecular mechanisms

Purpose: Gene therapies via Noggin small interfering (si)RNA (siNoggin) and bone morphogenetic protein (BMP)-2 plasmid DNA (pBMP-2) may be promising strategies for bone repair/regeneration, but their ideal delivery vectors, efficacy difference, and underlying mechanisms have not been explored, so these issues were probed here.

Methods: This study used lipopolysaccharide-amine nanopolymersomes (LNPs), an efficient cytosolic delivery vector developed by the research team, to mediate siNoggin and pBMP-2 to transfect MC3T3-E1 cells, respectively. The cytotoxicity, cell uptake, and gene knockdown efficiency of siNoggin-loaded LNPs (LNPs/siNoggin) were studied, then the osteogenic-differentiation efficacy of MC3T3-E1 cells treated by LNPs/pBMP-2 and LNPs/siNoggin, respectively, were compared by measuring the expression of osteogenesis-related genes and proteins, alkaline phosphatase (ALP) activity, and mineralization of the extracellular matrix at all osteogenic stages. Finally, the possible signaling pathways of the two treatments were explored.

Results: LNPs delivered siNoggin into cells efficiently to silence 50% of Noggin expression without obvious cytotoxicity. LNPs/siNoggin and LNPs/pBMP-2 enhanced the osteogenic differentiation of MC3T3 E1 cells, but LNPs/siNoggin was better than LNPs/pBMP-2. BMP/Mothers against decapentaplegic homolog (Smad) and glycogen synthase kinase (GSK)-3β/β-catenin signaling pathways appeared to be involved in osteogenic differentiation induced by LNPs/siNoggin, but GSK-3β/β-catenin was not stimulated upon LNPs/pBMP-2 treatment.

Conclusion: LNPs are safe and efficient delivery vectors for DNA and RNA, which may find wide applications in gene therapy. siNoggin treatment may be a more efficient strategy to enhance osteogenic differentiation than pBMP-2 treatment. LNPs loaded with siNoggin and/or pBMP-2 may provide new opportunities for the repair and regeneration of bone.

Advanced biomaterials for repairing and reconstruction of mandibular defects

Mandibles are the largest and strongest bone in the human face and are often severely compromised by mandibular defects, compromising the quality of life of patients. Mandibular defects may result from trauma, inflammatory disease and benign or malignant tumours. The reconstruction of mandibular defect has been a research hotspot in oral and maxillofacial surgery. Although the principles and techniques of mandibular reconstruction have made great progress in recent years, the development of biomedical materials is still facing technical bottleneck, and new materials directly affect technological breakthroughs in this field. This paper reviews the current status of research and application of various biomaterials in mandibular defects and systematically elaborates different allogeneic biomaterial-based approaches. It is expected that various biomaterials, in combination with new technologies such as digital navigation and 3D printing, could be tuned to build new types of scaffold with more precise structure and components, addressing needs of surgery and post-reconstruction. With the illustration and systematization of different solutions, aims to inspire the development of reconstruction biomaterials.

Effect of recombinant human bone morphogenetic protein delivered by chitosan microspheres on ectopic osteogenesis in rats

In the present study, the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered by chitosan (CS) microspheres on ectopic osteogenesis was investigated in a rat model. rhBMP-2-loaded CS microspheres and blank CS microspheres were prepared. A total of 24 male Sprague Dawley rats were divided into 4 groups with 6 rats in each group: The CS/rhBMP-2 group, the rhBMP-2 group, in which rhBMP-2 was directly implanted (rhBMP-2 dose in either group, 1 mg), the CS blank group and the control group. X-ray was performed at 4 weeks after ectopic osteogenesis surgery and micro-computed tomography (CT) examination was scheduled at 1, 2, 3 and 4 weeks after the surgery to determine ectopic osteogenesis in the different groups. Histological analysis, and determination of alkaline phosphatase (ALP) activity and calcium content were also performed. The mean diameter of the osteoid tissues was 1.1±0.3 cm (range, 0.8-1.4 cm) in the CS/rhBMP-2 group, which was significantly bigger than that in the rhBMP-2 group (0.3±0.1 cm; range, 0.1-0.4 cm) at 4 weeks after the surgery. X-ray analysis and micro-CT scan indicated that the area of high-density tissues and the radionuclide intensity, as well as bone volume in the 3-dimensional reconstruction were greatest in the CS/rhBMP-2 group, followed by those in the rhBMP-2 group. All parameters, including bone mineral density, tissue mineral density, tissue mineral content and bone volume fraction, were significantly higher in the CS/rhBMP-2 group at 3 and 4 weeks after the surgery, compared with those in the rhBMP-2 group. The histological analysis, ALP activity analysis and determination of calcium content revealed that the CS/rhBMP-2 system had the greatest ability to induce osteoblast differentiation. In conclusion, the CS/rhBMP-2 microsphere delivery system significantly enhanced the induction and promotion effects of rhBMP-2 regarding ectopic osteogenesis. The present study enhances the basic data available for future application of the CS/rhBMP-2 microspheres delivery system and provides a deeper understanding of the role of BMP-2 in bone regeneration.

Heparin-Conjugated Decellularized Bone Particles Promote Enhanced Osteogenic Signaling of PDGF-BB to Adipose-Derived Stem Cells in Tissue Engineered Bone Grafts

Adipose-derived stem cells (ASCs) are a promising cell source for regenerating critical-sized craniofacial bone defects, but their clinical use is limited due to the supraphysiological levels of bone morphogenetic protein-2 required to induce bone formation in large grafts. It has been recently reported that platelet-derived growth factor-BB (PDGF) directly enhances the osteogenesis of ASCs when applied at physiological concentrations. In this study, a biomimetic delivery system that tethers PDGF to decellularized bone matrix (DCB) is developed to enhance osteogenic signaling in bone grafts by colocalizing PDGF-extracellular matrix cues. Heparin is conjugated to DCB particles (HC-DCB) to promote sustained binding of PDGF via electrostatic interactions. HC-DCB particles bind to PDGF with >99% efficiency and release significantly less PDGF over 21 days compared to nonconjugated DCB particles (1.1% vs 22.8%). HC-DCB-PDGF signaling in polycaprolactone (PCL)-fibrin grafts promotes >40 µg Ca²⁺ µg^-1 DNA deposition by ASCs during in vitro osteogenic culture compared to grafts without HC-DCB or PDGF. Furthermore, more bone formation is observed in grafts with HC-DCB-PDGF at 12 weeks following implantation of grafts into murine critical-sized calvarial defects. Collectively, these results demonstrate that HC-DCB enhances the osteogenic signaling of PDGF to ASCs and may be applied to promote ASC-mediated bone regeneration in critical-sized defects.

Repair of Critical-Sized Mandible Defects in Aged Rat Using Hypoxia Preconditioned BMSCs with Up-regulation of Hif-1α

The repair of bone defects in the geriatric population remains a challenge for modern medicine. Transplantation of bone marrow mesenchymal stem cells (BMSCs) combined with or without biomaterials has been a promising approach to bone restoration and regeneration. Typically, the transplanted BMSCs are cultured under normoxic conditions (21% O2 and 10% serum medium) in vitro. However, the micro-environment of bone defect area is much more severe, in which lower physiological oxygen tension (<1%) and tissue ischemia were present. Therefore, how to improve the survival rate and osteogenesis of transplanted BMSCs at the low oxygenic and ischemic region in vivo is critical. Hypoxia inducible factor-1α (HIF-1α) plays an important role in the tolerance, angiogenesis and osteogenesis of BMSCs during bone regeneration after transplantation. Previous studies have demonstrated that Dimethyloxaloylglycine (DMOG) improves the angiogenic activity of BMSCs. Typically, angiogenesis and osteogenesis are coupled with each other. Therefore, we detected that hypoxia preconditioned BMSCs with the combined treatment of 1% O2 and 0.5mM DMOG showing up-regulation of Hif-1α could enhance the survival rate of BMSCs under severe condition (serum-free medium and 1% O2) in vitro and enhances the angiogenesis and osteogenesis potential of BMSCs under 1% O2 microenvironment in vitro. The hypoxia preconditioned BMSCs were transplanted into critical-sized mandible defects in aged SD rats to test the effectiveness of hypoxic preconditioning approach. We found that hypoxia preconditioned BMSCs improved the repair of critical-sized mandible defects in vivo. These data showed that hypoxia preconditioned BMSCs with the up-regulation of Hif-1α have the potential of enhancing the bone healing process in geriatric individuals.

Co-injection of human adipose stromal cells and rhBMP-2/fibrin gel enhances tendon graft osteointegration in a rabbit anterior cruciate ligament-reconstruction model

The objective of this study was to investigate whether the co-injection of human adipose stromal cells (hASCs) and rhBMP-2/fibrin gel into the bone tunnels of anterior cruciate-ligament reconstructions can effectively enhance tendon graft osteointegration. We performed bilateral reconstructions using autologous semitendinosus tendons in 45 New Zealand rabbits, which we divided into three groups. We injected the bone tunnels with fibrin gel for group 1, rhBMP-2 (1 μg/ml)/fibrin gel for group 2, and hASCs wrapped in rhBMP-2 (1 μg/ml)/fibrin gel for group 3. We sacrificed five rabbits (two for histological assessment and three for biomechanical tests) from each group at 2, 4, and 8 weeks post surgery. At 2 and 4 weeks post surgery, histological analysis showed that fibro-cartilage had appeared in the tendon-bone interface in group 2. At 4 weeks post surgery, mature bone cells could be seen in group 3. There was new bone formed between the host bone and the graft in groups 2 and 3 at 8 weeks post surgery. Biomechanical testing showed that at 4 and 8 weeks post surgery, the ultimate failure loads in group 3 were significantly higher than those in groups 1 and 2 (both P=0.01). The tendon stiffness in group 3 was significantly higher than that in the other groups at 4 weeks post surgery (P=0.01). Our results indicate that co-injection of hASCs and rhBMP-2/fibrin gel has the potential to promote tendon-bone healing after anterior cruciate-ligament reconstruction.

[The progress of research on three-dimensional printed jaw scaffolds]

Large defects of jaw caused by tumor, trauma and so on in oral and maxillofacial region lead to facial deformity, language and chewing dysfunction, which severely damage the patient's life quality. Three-dimensional printing (3DP) is also named additive manufacturing (AM), which can print materials layer by layer to create three-dimensional objects. The complex shape of jaw defects can be accurately reconstructed using 3DP scaffold combined with image data, computer-aided-design and manufacture. It has specific advantages compared with traditional way of jaw reconstruction and has attracted much attention in the field of jaw tissue engineering recently. This article presented the progress of 3DP scaffold and its application in jaw reconstruction, providing a new idea for jaw reconstruction.

Proceedings of the American Association of Oral and Maxillofacial Surgeon's 2017 Clinical and Scientific Innovations in Oral and Maxillofacial Surgery (CSIOMS)

The sixth biennial Clinical and Scientific Innovations in Oral and Maxillofacial Surgery, formerly the Research Summit, of the American Association of Oral and Maxillofacial Surgeons and its Committee on Research Planning and Technology Assessment was held in Rosemont, Illinois from April 28 to 30, 2017. The goal of the symposium is to provide a forum for the latest clinical and scientific advances to be brought to the specialty. It also nurtures collaboration and the development of relationships between oral and maxillofacial surgeons and researchers to bridge the gap between clinical and basic science. The goal is to improve the care of oral and maxillofacial surgical patients through the advancement of translational and clinical research.

Small molecule-mediated tribbles homolog 3 promotes bone formation induced by bone morphogenetic protein-2

Although bone morphogenetic protein-2 (BMP2) has demonstrated extraordinary potential in bone formation, its clinical applications require supraphysiological milligram-level doses that increase postoperative inflammation and inappropriate adipogenesis, resulting in well-documented life-threatening cervical swelling and cyst-like bone formation. Recent promising alternative biomolecular strategies are toward promoting pro-osteogenic activity of BMP2 while simultaneously suppressing its adverse effects. Here, we demonstrated that small molecular phenamil synergized osteogenesis and bone formation with BMP2 in a rat critical size mandibular defect model. Moreover, we successfully elicited the BMP2 adverse outcomes (i.e. adipogenesis and inflammation) in the mandibular defect by applying high dose BMP2. Phenamil treatment significantly improves the quality of newly formed bone by inhibiting BMP2 induced fatty cyst-like structure and inflammatory soft-tissue swelling. The observed positive phenamil effects were associated with upregulation of tribbles homolog 3 (Trib3) that suppressed adipogenic differentiation and inflammatory responses by negatively regulating PPARγ and NF-κB transcriptional activities. Thus, use of BMP2 along with phenamil stimulation or Trib3 augmentation may be a promising strategy to improve clinical efficacy and safety of current BMP therapeutics.

Simultaneous delivery of hydrophobic small molecules and siRNA using Sterosomes to direct mesenchymal stem cell differentiation for bone repair

The use of small molecular drugs with gene manipulation offers synergistic therapeutic efficacy by targeting multiple signaling pathways for combined treatment. Stimulation of mesenchymal stem cells (MSCs) with osteoinductive small molecule phenamil combined with suppression of noggin is a promising therapeutic strategy that increases bone morphogenetic protein (BMP) signaling and bone repair. Our cationic Sterosome formulated with stearylamine (SA) and cholesterol (Chol) is an attractive co-delivery system that not only forms stable complexes with small interfering RNA (siRNA) molecules but also solubilizes hydrophobic small molecules in a single vehicle, for directing stem cell differentiation. Herein, we demonstrate the ability of SA/Chol Sterosomes to simultaneously deliver hydrophobic small molecule phenamil and noggin-directed siRNA to enhance osteogenic differentiation of MSCs both in in vitro two- and three-dimensional settings as well as in a mouse calvarial defect model. These results suggest a novel liposomal platform to simultaneously deliver therapeutic genes and small molecules for combined therapy.

STATEMENT OF SIGNIFICANCE

Application of phenamil, a small molecular bone morphogenetic protein (BMP) stimulator, combined with suppression of natural BMP antagonists such as noggin is a promising therapeutic strategy to enhance bone regeneration. Here, we present a novel strategy to co-deliver hydrophobic small molecule phenamil and noggin-targeted siRNA via cationic Sterosomes formed with stearylamine (SA) and high content of cholesterol (Chol) to enhance osteogenesis and bone repair. SA/Chol Sterosomes demonstrated high phenamil encapsulation efficiency, supported sustained release of encapsulated drugs, and significantly reduced drug dose requirements to induce osteogenic differentiation of mesenchymal stem cells (MSCs). Simultaneous deliver of phenamil and noggin siRNA in a single vehicle synergistically enhanced MSC osteogenesis and calvarial bone repair. This study suggests a new non-phospholipid liposomal formulation to simultaneously deliver small molecules and therapeutic genes for combined treatment.

Versatility of Chitosan-Based Biomaterials and Their Use as Scaffolds for Tissue Regeneration

Chitosan is a naturally occurring polysaccharide obtained from chitin, present in abundance in the exoskeletons of crustaceans and insects. It has aroused great interest as a biomaterial for tissue engineering on account of its biocompatibility and biodegradation and its affinity for biomolecules. A significant number of research groups have investigated the application of chitosan as scaffolds for tissue regeneration. However, there is a wide variability in terms of physicochemical characteristics of chitosan used in some studies and its combinations with other biomaterials, making it difficult to compare results and standardize its properties. The current systematic review of literature on the use of chitosan for tissue regeneration consisted of a study of 478 articles in the PubMed database, which resulted, after applying inclusion criteria, in the selection of 61 catalogued, critically analysed works. The results demonstrated the effectiveness of chitosan-based biomaterials in 93.4% of the studies reviewed, whether or not combined with cells and growth factors, in the regeneration of various types of tissues in animals. However, the absence of clinical studies in humans, the inadequate experimental designs, and the lack of information concerning chitosan's characteristics limit the reproducibility and relevance of studies and the clinical applicability of chitosan.

Adipose-derived stem cell therapies for bone regeneration

INTRODUCTION

Cell-based therapies exploit the heterogeneous and self-sufficient biological environment of stem cells to restore, maintain and improve tissue functions. Adipose-derived stem cells (ASCs) are, to this aim, promising cell types thanks to advantageous isolation procedures, growth kinetics, plasticity and trophic properties. Specifically, bone regeneration represents a suitable, though often challenging, target setting to test and apply ASC-based therapeutic strategies. Areas covered: ASCs are extremely plastic and secrete bioactive peptides that mediate paracrine functions, mediating their trophic actions in vivo. Numerous preclinical studies demonstrated that ASCs improve bone healing. Clinical trials are ongoing to validate the clinical feasibility of these approaches. This review is intended to define the state-of-the-art on ASCs, encompassing the biological features that make them suitable for bone regenerative strategies, and to provide an update on existing preclinical and clinical applications. Expert opinion: ASCs offer numerous advantages over other stem cells in terms of feasibility of clinical translation. Data obtained from in vivo experimentation are encouraging, and clinical trials are ongoing. More robust validations are thus expected to be achieved during the next few years, and will likely pave the way to optimized patient-tailored treatments for bone regeneration.

Human DPSCs fabricate vascularized woven bone tissue: a new tool in bone tissue engineering

Human dental pulp stem cells (hDPSCs) are mesenchymal stem cells that have been successfully used in human bone tissue engineering. To establish whether these cells can lead to a bone tissue ready to be grafted, we checked DPSCs for their osteogenic and angiogenic differentiation capabilities with the specific aim of obtaining a new tool for bone transplantation. Therefore, hDPSCs were specifically selected from the stromal–vascular dental pulp fraction, using appropriate markers, and cultured. Growth curves, expression of bone-related markers, calcification and angiogenesis as well as an in vivo transplantation assay were performed. We found that hDPSCs proliferate, differentiate into osteoblasts and express high levels of angiogenic genes, such as vascular endothelial growth factor and platelet-derived growth factor A. Human DPSCs, after 40 days of culture, give rise to a 3D structure resembling a woven fibrous bone. These woven bone (WB) samples were analysed using classic histology and synchrotron-based, X-ray phase-contrast microtomography and holotomography. WB showed histological and attractive physical qualities of bone with few areas of mineralization and neovessels. Such WB, when transplanted into rats, was remodelled into vascularized bone tissue. Taken together, our data lead to the assumption that WB samples, fabricated by DPSCs, constitute a noteworthy tool and do not need the use of scaffolds, and therefore they are ready for customized regeneration.

Enhanced Mandibular Bone Repair by Combined Treatment of Bone Morphogenetic Protein 2 and Small-Molecule Phenamil

Growth factor-based therapeutics using bone morphogenetic protein 2 (BMP-2) presents a promising strategy to reconstruct craniofacial bone defects such as mandible. However, clinical applications require supraphysiological BMP doses that often increase inappropriate adipogenesis, resulting in well-documented, cyst-like bone formation. Here we reported a novel complementary strategy to enhance osteogenesis and mandibular bone repair by using small-molecule phenamil that has been shown to be a strong activator of BMP signaling. Phenamil synergistically induced osteogenic differentiation of human bone marrow mesenchymal stem cells with BMP-2 while suppressing their adipogenic differentiation induced by BMP-2 in vitro. The observed pro-osteogenic and antiadipogenic activity of phenamil was mediated by expression of tribbles homolog 3 (Trb3) that enhanced BMP-smad signaling and inhibited expression of peroxisome proliferator-activated receptor gamma (PPARγ), a master regulator of adipogenesis. The synergistic effect of BMP-2+phenamil on bone regeneration was further confirmed in a critical-sized rat mandibular bone defect by implanting polymer scaffolds designed to slowly release the therapeutic molecules. These findings indicate a new complementary osteoinductive strategy to improve clinical efficacy and safety of current BMP-based therapeutics.

Vapor-based coatings for antibacterial and osteogenic functionalization and the immunological compatibility

The immobilization of biofunctional molecules to biomaterial surfaces has enabled and expanded the versatility of currently available biomaterials to a wider range of applications. In addition, immobilized biomolecules offer modified surfaces that allow the use of smaller amounts of potentially harmful substances or prevent overdose, while the exhibited biological functions remain persistently effective. Surface concentrations of chlorhexidine (CHX) (1.40±0.08×10(-9)mol·cm(-2)) and bone morphogenetic protein 2 (BMP-2) (1.51±0.08×10(-11)mol·cm(-2)) immobilized molecules were determined in this study, and their specific biological functions in terms of antibacterial activity and osteogenesis potency, respectively, were demonstrated to be unambiguously effective. Immobilization exploits the use of vapor-based poly-p-xylylenes, which exhibit excellent biocompatibility and wide applicability for various substrate materials. This technique represents a practical and economical approach for the manufacture of certain industrial products. Furthermore, a minimal degree of macrophage activation was indicated on the modified surfaces via insignificant morphological changes and low levels of adverse inflammatory signals, including suppressed production of the pro-inflammatory cytokines IL-1β and TNF-α as well as nitric oxide (NO). The results and the modification strategy illustrate a concept for designing prospective biomaterial surfaces such that the manipulation employed to elicit targeted biological responses does not compromise immunological compatibility.

Enhanced Osteogenesis of Adipose-Derived Stem Cells by Regulating Bone Morphogenetic Protein Signaling Antagonists and Agonists

Although adipose-derived stem cells (ASCs) are an attractive cell source for bone tissue engineering, direct use of ASCs alone has had limited success in the treatment of large bone defects. Although bone morphogenetic proteins (BMPs) are believed to be the most potent osteoinductive factors to promote osteogenic differentiation of ASCs, their clinical applications require supraphysiological dosage, leading to high medical burden and adverse side effects. In the present study, we demonstrated an alternative approach that can effectively complement the BMP activity to maximize the osteogenesis of ASCs without exogenous application of BMPs by regulating levels of antagonists and agonists to BMP signaling. Treatment of ASCs with the amiloride derivative phenamil, a positive regulator of BMP signaling, combined with gene manipulation to suppress the BMP antagonist noggin, significantly enhanced osteogenic differentiation of ASCs through increased BMP-Smad signaling in vitro. Furthermore, the combination approach of noggin suppression and phenamil stimulation enhanced the BMP signaling and bone repair in a mouse calvarial defect model by adding noggin knockdown ASCs to apatite-coated poly(lactic-coglycolic acid) scaffolds loaded with phenamil. These results suggest novel complementary osteoinductive strategies that could maximize activity of the BMP pathway in ASC bone repair while reducing potential adverse effects of current BMP-based therapeutics.

SIGNIFICANCE

Although stem cell-based tissue engineering strategy offers a promising alternative to repair damaged bone, direct use of stem cells alone is not adequate for challenging healing environments such as in large bone defects. This study demonstrates a novel strategy to maximize bone formation pathways in osteogenic differentiation of mesenchymal stem cells and functional bone formation by combining gene manipulation with a small molecule activator toward osteogenesis. The findings indicate promising stem cell-based therapy for treating bone defects that can effectively complement or replace current osteoinductive therapeutics.

An Effective and Reliable Xeno-free Cryopreservation Protocol for Single Human Pluripotent Stem Cells

Efficient cryopreservation of human pluripotent stem cells (hPSCs) in chemically defined, xeno-free conditions is highly desirable for medical research and clinical applications such as cell-based therapies. Here we present a simple and effective slow freezing-rapid thawing protocol for the cryopreservation of feeder-free, single hPSCs. This cryopreservation protocol involves the supplementation of 10 % dimethyl sulfoxide (DMSO) and 10 μM Rho-associated kinase inhibitor Y-27632 into two types of xeno-free, defined media supplements (Knockout Serum Replacement and TeSR2). High post-thaw cell recovery (~90 %) and cell expansion (~70 %) can be achieved using this protocol. The cryopreserved single cells retain the morphological characteristics of hPSCs and differentiation capabilities of pluripotent stem cells.

Long-term xeno-free culture of human pluripotent stem cells on hydrogels with optimal elasticity

The tentative clinical application of human pluripotent stem cells (hPSCs), such as human embryonic stem cells and human induced pluripotent stem cells, is restricted by the possibility of xenogenic contamination resulting from the use of mouse embryonic fibroblasts (MEFs) as a feeder layer. Therefore, we investigated hPSC cultures on biomaterials with different elasticities that were grafted with different nanosegments. We prepared dishes coated with polyvinylalcohol-co-itaconic acid hydrogels grafted with an oligopeptide derived from vitronectin (KGGPQVTRGDVFTMP) with elasticities ranging from 10.3 to 30.4 kPa storage moduli by controlling the crosslinking time. The hPSCs cultured on the stiffest substrates (30.4 kPa) tended to differentiate after five days of culture, whereas the hPSCs cultured on the optimal elastic substrates (25 kPa) maintained their pluripotency for over 20 passages under xeno-free conditions. These results indicate that cell culture matrices with optimal elasticity can maintain the pluripotency of hPSCs in culture.

Bone Morphogenetic Protein-2 Induces Donor-Dependent Osteogenic and Adipogenic Differentiation in Human Adipose Stem Cells

Bone morphogenetic protein-2 (BMP-2) is a growth factor used to stimulate bone regeneration in clinical applications. However, there are contradicting reports on the functionality of BMP-2 in human adipose stem cells (hASCs), which are frequently used in tissue engineering. In this study, we analyzed the effects of BMP-2 on SMAD1/5 signaling, proliferation, and differentiation in hASCs. Our results indicated that BMP-2 induced dose-dependent (25-100 ng/ml) activation of SMAD signaling. Furthermore, the cell proliferation analysis revealed that BMP-2 (100 ng/ml) consistently decreased the proliferation in all the cell lines studied. However, the analysis of the differentiation potential revealed that BMP-2 (100 ng/ml) exhibited a donor-dependent dual role, inducing both osteogenic and adipogenic differentiation in hASCs. The quantitative alkaline phosphatase (qALP) activity and mineralization levels were clearly enhanced in particular donor cell lines by BMP-2 stimulus. On the contrary, in other cell lines, qALP and mineralization levels were diminished and the lipid formation was enhanced. The current study also suggests that hASCs have accelerated biochemical responsiveness to BMP-2 stimulus in human serum-supplemented culture medium compared with fetal bovine serum. The production origin of the BMP-2 growth factor is also important for its response: BMP-2 produced in mammalian cells enhanced signaling and differentiation responses compared with BMP-2 produced in Escherichia coli. These results explain the existing contradiction in the reported BMP-2 studies and indicate the variability in the functional end mechanism of BMP-2-stimulated hASCs.

SIGNIFICANCE

This study examined how bone morphogenetic protein-2 (BMP-2) modulates the SMAD signaling mechanism and the proliferation and differentiation outcome of human adipose stem cells (hASCs) derived from several donors. The results indicate that BMP-2 triggers molecular SMAD signaling mechanisms in hASCs and regulates differentiation processes in human serum-culture conditions. Importantly, BMP-2 has dual activity, inducing osteogenic and adipogenic differentiation, subject to hASC donor line studied. These findings explain contradictory previous results and highlight the importance of further studies to understand how signaling pathways guide mesenchymal stem cell functions at the molecular level.

Delivery of siRNA via cationic Sterosomes to enhance osteogenic differentiation of mesenchymal stem cells

Noggin is a specific antagonist of bone morphogenetic proteins (BMPs) that can prevent the interaction of BMPs with their receptors. RNA interfering molecules have been used to downregulate noggin expression and thereby stimulate BMP signaling and osteogenesis. Cationic liposomes are considered one of the most efficient non-viral systems for gene delivery. In the past decade, non-phospholipid liposomes (Sterosomes) formulated with single-chain amphiphiles and high content of sterols have been developed. In particular, Sterosomes composed of stearylamine (SA) and cholesterol (Chol) display distinct properties compared with traditional phospholipid liposomes, including increased positive surface charges and enhanced particle stability. Herein, we report SA/Chol Sterosome and small interfering RNA (siRNA) complexes that significantly enhanced cellular uptake and gene knockdown efficiencies in adipose derived mesenchymal stem cells with minimal cytotoxicity compared with commercially available lipofectamine 2000. Furthermore, we confirmed osteogenic efficacy of these Sterosomes loaded with noggin siRNA in in vitro two- and three-dimensional settings as well as in a mouse calvarial defect model. The delivery of siRNA via novel SA/Chol Sterosomes presents a powerful method for efficient gene knockdown. These distinct nanoparticles may present a promising alternative approach for gene delivery.

Delivery of Phenamil Enhances BMP-2-Induced Osteogenic Differentiation of Adipose-Derived Stem Cells and Bone Formation in Calvarial Defects

Bone morphogenetic proteins (BMPs) have been widely used for bone repair in the craniofacial region. However, its high dose requirement in clinical applications revealed adverse effects and inefficient bone formation, along with high cost. Here, we report a novel osteoinductive strategy to effectively complement the osteogenic activity of BMP-2 using phenamil, a small molecule that can induce osteogenic differentiation via stimulation of BMP signaling. Treatment of adipose-derived stem cells (ASCs) with BMP-2 in combination with phenamil significantly promoted the in vitro osteogenic differentiation of ASCs. The efficacy of the combination strategy of phenamil+BMP-2 was further confirmed in a mouse calvarial defect model using scaffolds consisting of poly(lactic-co-glycolic acid) and apatite layer on their surfaces designed to slowly release phenamil and BMP-2. Six weeks after implantation, the scaffolds treated with phenamil+BMP-2 significantly promoted mouse calvarial regeneration as demonstrated by micro-computerized tomography and histology, compared with the groups treated with phenamil or BMP-2 alone. Moreover, the combination treatment reduced the BMP-2 dose without compromising calvarial healing efficacy. These results suggest promising complementary therapeutic strategies for bone repair in more efficient and cost-effective manners.

Impact of surgical innovation on tissue repair in the surgical patient

BACKGROUND

Throughout history, surgeons have been prolific innovators, which is hardly surprising as most surgeons innovate daily, tailoring their intervention to the intrinsic uniqueness of each operation, each patient and each disease. Innovation can be defined as the application of better solutions that meet new requirements, unarticulated needs or existing market needs. In the past two decades, surgical innovation has significantly improved patient outcomes, complication rates and length of hospital stay. There is one key area that has great potential to change the face of surgical practice and which is still in its infancy: the realm of regenerative medicine and tissue engineering.

METHODS

A literature review was performed using PubMed; peer-reviewed publications were screened for relevance in order to identify key surgical innovations influencing regenerative medicine, with a focus on osseous, cutaneous and soft tissue reconstruction.

RESULTS

This review describes recent advances in regenerative medicine, documenting key innovations in osseous, cutaneous and soft tissue regeneration that have brought regenerative medicine to the forefront of the surgical imagination.

CONCLUSION

Surgical innovation in the emerging field of regenerative medicine has the ability to make a major impact on surgery on a daily basis.

Effect of activated autologous platelet-rich plasma on proliferation and osteogenic differentiation of human adipose-derived stem cells in vitro

To investigate whether activated autologous platelet-rich plasma (PRP) can promote proliferation and osteogenic differentiation of human adipose-derived stem cells (hASCs) in vitro. hASCs were isolated from lipo-aspirates, and characterized by specific cell markers and multilineage differentiation capacity after culturing to the 3(rd) passage. PRP was collected and activated from human peripheral blood of the same patient. Cultured hASCs were treated with normal osteogenic inductive media alone (group A, control) or osteogenic inductive media plus 5%, 10%, 20%, 40%PRP (group B, C, D, E, respectively). Cell proliferation was assessed by CCK-8 assay. mRNA expression of osteogenic marker genes including alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OCN) and core binding factor alpha 1 (Cbfa1) were determined by Real-Time Quantitative PCR Analysis (qPCR). Data revealed that different concentrations of activated autologous PRP significantly promoted hASCs growth in the proliferation phase compared to the without PRP group and resulted in a dose-response relationship. At 7-d and 14-d time point of the osteogenic induced stage, ALP activity in PRP groups gradually increased with the increasing of concentrations of PRP and showed that dose-response relationship. At 21-d time point of the osteogenic induced stage, PRP groups make much more mineralization and mRNA relative expression of ALP, OPN, OCN and Cbfa1 than that without PRP groups and show that dose-response relationship. This study indicated that different concentrations of activated autologous PRP can promote cell proliferation at earlier stage and promote osteogenic differentiation at later stage of hASCs in vitro. Moreover, it displayed a dose-dependent effect of activated autologous PRP on cell proliferation and osteogenic differentiation of hASCs in vitro.