Tissue engineered bone grafts based on biomimetic nanocomposite PLGA/amorphous calcium phosphate scaffold and human adipose-derived stem cells

Pro-angiogenic and antibacterial copper containing nanoparticles in PLGA/amorphous calcium phosphate bone nanocomposites

Large bone defects after trauma demand for adequate bone substitutes. Bone void fillers should be antibacterial and pro-angiogenic. One viable option is the use of composite materials like the combination of PLGA and amorphous calcium phosphate (aCaP). Copper stimulates angiogenesis and has antibacterial qualities. Either copper oxide (CuO) nanoparticles (NPs) were therefore added to PLGA/aCaP/CuO in different concentrations (1, 5 and 10 w/w %) or copper-doped tricalcium phosphate NPs (TCP with 2% of copper) were electrospun into PLGA/CuTCP nanocomposites. Bi-layered nanocomposites of PLGA/aCaP with different copper NPs (CuO or TCP) and a second layer of pristine PLGA were fabricated. Two clinical bacterial isolates (Staphylococcus aureus and Staphylococcus epidermidis) were used to assess antibacterial properties of the copper-containing materials. For angiogenesis, the chorioallantoic membrane (CAM) assay of the chicken embryo was performed. The higher the CuO content, the higher were the antibacterial properties, with 10 % CuO reducing bacterial adhesion most effectively. Vessel and cell densities were highest in the 5 % CuO containing scaffolds, while tissue integration was more pronounced at lower CuO content. The PLGA/aCaP/CuO (1 % CuO) behaved similar like PLGA/CuTCP in all angiogenic and antibacterial readouts, based on the same copper fraction. We conclude that CuO NPs or CuTCP NPs are useful components to increase angiogenic properties of nanocomposites and at the same time exhibiting antibacterial characteristics.

In Vitro Enhanced Osteogenic Potential of Human Mesenchymal Stem Cells Seeded in a Poly (Lactic-co-Glycolic) Acid Scaffold: A Systematic Review

Study Design

Human bone marrow stem cells (hBMSCs) and human adipose-derived stem cells (hADSCs) have demonstrated the capability to regenerate bone once they have differentiated into osteoblasts.

Objective

This systematic review aimed to evaluate the in vitro osteogenic differentiation potential of these cells when seeded in a poly (lactic-co-glycolic) acid (PLGA) scaffold.

Methods

A literature search of 4 databases following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted in January 2021 for studies evaluating the osteogenic differentiation potential of hBMSCs and hADSCs seeded in a PLGA scaffold. Only in vitro models were included. Studies in languages other than English were excluded.

Results

A total of 257 studies were identified after the removal of duplicates. Seven articles fulfilled our inclusion and exclusion criteria. Four of these reviews used hADSCs and three used hBMSCs in the scaffold. Upregulation in osteogenic gene expression was seen in all the cells seeded in a 3-dimensional scaffold compared with 2-dimensional films. High angiogenic gene expression was found in hADSCs. Addition of inorganic material to the scaffold material affected cell performance.

Conclusions

Viability, proliferation, and differentiation of cells strongly depend on the environment where they grow. There are several factors that can enhance the differentiation capacity of stem cells. A PLGA scaffold proved to be a biocompatible material capable of boosting the osteogenic differentiation potential and mineralization capacity in hBMSCs and hADSCs.

SAXS imaging reveals optimized osseointegration properties of bioengineered oriented 3D-PLGA/aCaP scaffolds in a critical size bone defect model

Healing large bone defects remains challenging in orthopedic surgery and is often associated with poor outcomes and complications. A major issue with bioengineered constructs is achieving a continuous interface between host bone and graft to enhance biological processes and mechanical stability. In this study, we have developed a new bioengineering strategy to produce oriented biocompatible 3D PLGA/aCaP nanocomposites with enhanced osseointegration. Decellularized scaffolds -containing only extracellular matrix- or scaffolds seeded with adipose-derived mesenchymal stromal cells were tested in a mouse model for critical size bone defects. In parallel to micro-CT analysis, SAXS tensor tomography and 2D scanning SAXS were employed to determine the 3D arrangement and nanostructure within the critical-sized bone. Both newly developed scaffold types, seeded with cells or decellularized, showed high osseointegration, higher bone quality, increased alignment of collagen fibers and optimal alignment and size of hydroxyapatite minerals.

Cerium oxide nanoparticles disseminated chitosan gelatin scaffold for bone tissue engineering applications

Cell-free and cell-loaded constructs are used to bridge the critical-sized bone defect. Oxidative stress at the site of the bone defects is a major interference that slows bone healing. Recently, there has been an increase in interest in enhancing the properties of three-dimensional scaffolds with free radical scavenging materials. Cerium oxide nanoparticles (CNPs) can scavenge free radicals due to their redox-modulating property. In this study, freeze-drying was used to fabricate CG-CNPs nanocomposite scaffolds using gelatin (G), chitosan (C), and cerium oxide nanoparticles. Physico-chemical, mechanical, and biological characterization of CG-CNPs scaffolds were studied. CG-CNPs scaffolds demonstrated better results in terms of physicochemical, mechanical, and biological properties as compared to CG-scaffold. CG-CNPs scaffolds were cyto-friendly to MC3T3-E1 cells studied by performing in-vitro and in-ovo studies. The scaffold's antimicrobial study revealed high inhibition zones against Gram-positive and Gram-negative bacteria. With 79 % porosity, 45.99 % weight loss, 178.25 kPa compressive modulus, and 1.83 Ca/P ratio, the CG-CNP₂ scaffold displays the best characteristics. As a result, the CG-CNP₂ scaffolds are highly biocompatible and could be applied to repair bone defects.

Chorioallantoic Membrane Assay at the Cross-Roads of Adipose-Tissue-Derived Stem Cell Research

With a history of more than 100 years of different applications in various scientific fields, the chicken chorioallantoic membrane (CAM) assay has proven itself to be an exceptional scientific model that meets the requirements of the replacement, reduction, and refinement principle (3R principle). As one of three extraembryonic avian membranes, the CAM is responsible for fetal respiration, metabolism, and protection. The model provides a unique constellation of immunological, vascular, and extracellular properties while being affordable and reliable at the same time. It can be utilized for research purposes in cancer biology, angiogenesis, virology, and toxicology and has recently been used for biochemistry, pharmaceutical research, and stem cell biology. Stem cells and, in particular, mesenchymal stem cells derived from adipose tissue (ADSCs) are emerging subjects for novel therapeutic strategies in the fields of tissue regeneration and personalized medicine. Because of their easy accessibility, differentiation profile, immunomodulatory properties, and cytokine repertoire, ADSCs have already been established for different preclinical applications in the files mentioned above. In this review, we aim to highlight and identify some of the cross-sections for the potential utilization of the CAM model for ADSC studies with a focus on wound healing and tissue engineering, as well as oncological research, e.g., sarcomas. Hereby, the focus lies on the combination of existing evidence and experience of such intersections with a potential utilization of the CAM model for further research on ADSCs.

Hybrid nanocomposite as a chest wall graft with improved vascularization by copper oxide nanoparticles

Chest wall repair can be necessary after tumor resection or chest injury. In order to cover or replace chest wall defects, autologous tissue or different synthetic materials are commonly used, among them the semi-rigid gold standard Gore-Tex® and prolene meshes. Synthetic tissues include composite materials with an organic and an inorganic component. On the basis of previously reported hybrid nanocomposite poly-lactic-co-glycolic acid amorphous calcium phosphate nanocomposite (PLGA/aCaP), a CuO component was incorporated to yield (60%/35%/5%). This graft was tested in vitro by seeding with murine adipose-derived stem cells (ASCs) for cell attachment and migration. The graft was compared to PLGA/CaCO3 and PLGA/hydroxyapatite, each providing the inorganic phase as nanoparticles. Further characterization of the graft was performed using scanning electron microscopy. Furthermore, PLGA/aCaP/CuO was implanted as a chest wall graft in mice. After 4 weeks, total cell density, graft integration, extracellular matrix components such as fibronectin and collagen I, the cellular inflammatory response (macrophages, F4/80 and lymphocytes, CD3) as well as vascularization (CD31) were quantitatively assessed. The nanocomposite PLGA/aCaP/CuO showed a good cell attachment and cells migrated well into the pores of the electrospun meshes. Cell densities did not differ between PLGA/aCaP/CuO and PLGA/CaCO3 or PLGA/hydroxyapatite, respectively. When applied as a chest wall graft, adequate stability for suturing into the thoracic wall could be achieved. Four weeks post-implantation, there was an excellent tissue integration without relevant fibrotic changes and a predominating collagen I matrix deposition within the graft. Slightly increased inflammation, reflected by increased infiltration of macrophages could be observed. Vascularization of the graft was significantly enhanced when compared with PLGA/aCaP (no CuO). We conclude that the hybrid nanocomposite PLGA/aCaP/CuO is a viable option to be used as a chest wall graft. Surgical implantation of the material is feasible and provides stability and enough flexibility. Proper tissue integration and an excellent vascularization are characteristics of this biodegradable material.

Controlled Release of Caffeic Acid and Pinocembrin by Use of nPSi-βCD Composites Improves Their Antiangiogenic Activity

Although polyphenols have great pharmacological potential, the main disadvantage is that they have low bioavailability at the desired site. Thus, the use of biocompatible systems for drug delivery is a strategy that is currently gaining great interest. The objective of this study is to evaluate the effect of microencapsulation of caffeic acid and pinocembrin on the antioxidant and antiangiogenic activity of both polyphenols, by the use of nPSi-βCD composite microparticles. For this HUVEC, cells were exposed to H₂O₂ and to treatments with polyphenols in solution and loaded in the composite microparticle. The polyphenols were incorporated into a microparticle using nanoporous silicon, chitosan and a β-cyclodextrin polymer as the biomaterial. The evaluation of the antiangiogenic effect of the treatments with polyphenols in solution and microencapsulated was carried out through functional tests, and the changes in the expression of target genes associated with the antioxidant pathway and angiogenesis was performed through qPCR. The results obtained show that the caffeic acid and pinocembrin have an antioxidant and antiangiogenic activity, both in solution as microencapsulated. In the caffeic acid, a greater biological effect was observed when it was incorporated into the nPSi-βCD composite microparticle. Our results suggest that the nPSi-βCD composite microparticle could be used as an alternative oral drug administration system.

Adipose-Derived Stem Cell-Incubated HA-Rich Sponge Matrix Implant Modulates Oxidative Stress to Enhance VEGF and TGF-β Secretions for Extracellular Matrix Reconstruction In Vivo

This study demonstrated both adipose-derived stem cells (ASCs) in vitro and in vivo combined with three-dimensional (3D) porous sponge matrices on implant wound healing. Sponge matrices were created from hyaluronic acid (HA), collagen (Col), and gelatin (Gel), constructing two types: HA-L (low content) and HA-H (high content), to be cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Fourier transform infrared spectroscopy method verified carboxyl groups of HA and amino groups of Col and Gel reacting between the raw materials and scaffolds to identify the successive cross-linking. The swelling ratios of two types of sponge matrices were analyzed by water absorption capabilities, and the results displayed both over 30-fold dry scaffold weight enhancements. In biodegradation tests, matrices were hydrolyzed over time by three cutaneous enzymes, hyaluronidase, lysozyme, and collagenase I. ASCs from rats were cultured within the HA-H scaffold, demonstrating higher antioxidative abilities and secretions on related genes and proteins compared to the other two groups. The ASC HA-H matrix promoted cell proliferation to stimulate capillary angiogenesis inducer secretions, including vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGF-β). In vivo histological examinations showed ASCs from implanted HA-H implant transported into the subcutis, and rat skin cells also infiltrated into the original matrix zone to increase the extracellular matrix (ECM) reconstructions. Our experimental data revealed that the ASC HA-H sponge implant was effective in improving wound repair.

Impact of Electrospun Piezoelectric Core-Shell PVDFhfp/PDMS Mesh on Tenogenic and Inflammatory Gene Expression in Human Adipose-Derived Stem Cells: Comparison of Static Cultivation with Uniaxial Cyclic Tensile Stretching

Specific microenvironments can trigger stem cell tenogenic differentiation, such as specific substrates or dynamic cell cultivation. Electrospun meshes composed by core–shell fibers (random or aligned; PDMS core; piezoelectric PVDFhfp shell) were fabricated by coaxial electrospinning. Elastic modulus and residual strain were assessed. Human ASCs were seeded on such scaffolds either under static conditions for 1 week or with subsequent 10% dynamic stretching for 10,800 cycles (1 Hz, 3 h), assessing load elongation curves in a Bose^® bioreactor system. Gene expression for tenogenic expression, extracellular matrix, remodeling, pro-fibrotic and inflammatory marker genes were assessed (PCR). For cell-seeded meshes, the E modulus increased from 14 ± 3.8 MPa to 31 ± 17 MPa within 3 h, which was not observed for cell-free meshes. Random fibers resulted in higher tenogenic commitment than aligned fibers. Dynamic cultivation significantly enhanced pro-inflammatory markers. Compared to ASCs in culture flasks, ASCs on random meshes under static cultivation showed a significant upregulation of Mohawk, Tenascin-C and Tenomodulin. The tenogenic commitment expressed by human ASCs in contact with random PVDFhfp/PDMS paves the way for using this novel highly elastic material as an implant to be wrapped around a lacerated tendon, envisioned as a functional anti-adhesion membrane.

Synthetic amorphous calcium phosphates (ACPs): preparation, structure, properties, and biomedical applications

Amorphous calcium phosphates (ACPs) represent a metastable amorphous state of other calcium orthophosphates (abbreviated as CaPO₄) possessing variable compositional but rather identical glass-like physical properties, in which there are neither translational nor orientational long-range orders of the atomic positions. In nature, ACPs of a biological origin are found in the calcified tissues of mammals, some parts of primitive organisms, as well as in the mammalian milk. Manmade ACPs can be synthesized in a laboratory by various methods including wet-chemical precipitation, in which they are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing dissolved ions of Ca²⁺ and PO₄^3- in sufficient amounts. Due to the amorphous nature, all types of synthetic ACPs appear to be thermodynamically unstable and, unless stored in dry conditions or doped by stabilizers, they tend to transform spontaneously to crystalline CaPO₄, mainly to ones with an apatitic structure. This intrinsic metastability of the ACPs is of a great biological relevance. In particular, the initiating role that metastable ACPs play in matrix vesicle biomineralization raises their importance from a mere laboratory curiosity to that of a reasonable key intermediate in skeletal calcifications. In addition, synthetic ACPs appear to be very promising biomaterials both for manufacturing artificial bone grafts and for dental applications. In this review, the current knowledge on the occurrence, structural design, chemical composition, preparation, properties, and biomedical applications of the synthetic ACPs have been summarized.

Suspension of Amorphous Calcium Phosphate Nanoparticles Impact Commitment of Human Adipose-Derived Stem Cells In Vitro

Amorphous calcium phosphate (aCaP) nanoparticles may trigger the osteogenic commitment of adipose-derived stem cells (ASCs) in vitro. The ASCs of three human donors are investigated using basal culture medium DMEM to either 5 or 50 µg/mL aCaP nanoparticles suspension (control: no nanoparticles). After 7 or 14 days, stem cell marker genes, as well as endothelial, osteogenic, chondrogenic, and adipogenic genes, are analyzed by qPCR. Free calcium and phosphate ion concentrations are assessed in the cell culture supernatant. After one week and 5 µg/mL aCaP, downregulation of osteogenic markers ALP and Runx2 is found, and averaged across the three donors. Our results show that after two weeks, ALP is further downregulated, but Runx2 is upregulated. Endothelial cell marker genes, such as CD31 and CD34, are upregulated with 50 µg/mL aCaP and a 2-week exposure. Inter-donor variability is high: Two out of three donors show a significant upregulation of ALP and Runx2 at day 14 with 50 µg/mL aCaP compared to 5 µg/mL aCaP. Notably, all changes in stem cell commitment are obtained in the absence of an osteogenic medium. While the chemical composition of the culture medium and the saturation status towards calcium phosphate phases remain approximately the same for all conditions, gene expression of ASCs changes considerably. Hence, aCaP nanoparticles show the potential to trigger osteogenic and endothelial commitment in ASCs.

The use of the chick embryo CAM assay in the study of angiogenic activiy of biomaterials

The chick embryo chorioallantoic membrane (CAM) is a highly vascularized extraembryonic membrane, which carries out several functions during embryonic development, including exchange of respiratory gases, calcium transport from the eggshell, acid-base homeostasis in the embryo, and ion and water reabsorption from the allantoic fluid. Due to its easy accessibility, affordability and given that it constitutes an immunodeficient environment, CAM has been used as an experimental model for >50 years and in particular it has been broadly used to study angiogenesis and anti-angiogenesis. This review article describes the use of the CAM assay as a valuable assay to test angiogenic activity of biomaterials in vivo before they are further investigated in animal models. In this context, the use of CAM has become an integral part of the biocompatibility testing process for developing potential biomaterials.

Directing Stem Cell Commitment by Amorphous Calcium Phosphate Nanoparticles Incorporated in PLGA: Relevance of the Free Calcium Ion Concentration

The microenvironment of mesenchymal stem cells (MSCs) is responsible for the modulation in MSC commitment. Nanocomposites with an inorganic and an organic component have been investigated, and osteogenesis of MSCs has been attributed to inorganic phases such as calcium phosphate under several conditions. Here, electrospun meshes and two-dimensional films of poly(lactic-co-glycolic acid) (PLGA) or nanocomposites of PLGA and amorphous calcium phosphate nanoparticles (PLGA/aCaP) seeded with human adipose-derived stem cells (ASCs) were analyzed for the expression of selected marker genes. In a two-week in vitro experiment, osteogenic commitment was not found to be favored on PLGA/aCaP compared to pure PLGA. Analysis of the medium revealed a significant reduction of the Ca²⁺ concentration when incubated with PLGA/aCaP, caused by chemical precipitation of hydroxyapatite (HAp) on aCaP seeds of PLGA/aCaP. Upon offering a constant Ca²⁺ concentration, however, the previously observed anti-osteogenic effect was reversed: alkaline phosphatase, an early osteogenic marker gene, was upregulated on PLGA/aCaP compared to pristine PLGA. Hence, in addition to the cell–material interaction, the material–medium interaction was also important for the stem cell commitment here, affecting the cell–medium interaction. Complex in vitro models should therefore consider all factors, as coupled impacts might emerge.

3D microtissue-derived human stem cells seeded on electrospun nanocomposites under shear stress: Modulation of gene expression

OBJECTIVE

Different microenvironments trigger distinct differentiation of stem cells. Even without chemical supplementation, mechanical stimulation by shear stress may help to induce the desired differentiation. The cell format, such as three-dimensional (3D) microtissues (MTs), MT-derived cells or single cells (SCs), may have a pivotal impact as well. Here, we studied modulation of gene expression in human adipose-derived stem cells (ASCs) exposed to shear stress and/or after MT formation.

MATERIALS AND METHODS

Electrospun meshes of poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) at a weight ratio of 60:40 were seeded with human ASCs as MTs or as SCs and cultured in Dulbecco's modified Eagle's medium without chemical supplementation. After 2 weeks of static culture, the scaffolds were cultured statically for another 2 weeks or placed in a Bose® bioreactor with a flow rate per area of 0.16 mL cm^-2 min^-1. Stiffness of the scaffolds was assessed as a function of time. After 4 weeks, minimum stem cell criteria markers and selected markers of osteogenesis, endothelial cell differentiation, adipogenesis and chondrogenesis were analysed by quantitative real-time polymerase chain reaction. Additionally, cell distribution within the scaffolds and the allocation of the yes-associated protein (YAP) in the cells were assessed by immunohistochemistry.

RESULTS

MTs decayed completely within 2 weeks after seeding on PLGA/aCaP. The osteogenic marker gene alkaline phosphatase and the endothelial cell marker gene CD31 were upregulated in MT-derived ASCs compared with SCs. Shear stress realised by fluid flow perfusion upregulated peroxisome proliferator-activated receptor gamma 2 expression in MT-derived ASCs and in SCs. The nuclear-to-cytoplasmic ratio of YAP expression was doubled under perfusion compared with that under static culture for MT-derived ASCs and SCs.

CONCLUSIONS

Osteogenic and angiogenic commitments were more pronounced in MT-derived ASCs seeded on bone biomimetic electrospun nanocomposite PLGA/aCaP than in SCs seeded without induction medium. Furthermore, the static culture was superior to the perfusion regimen used here, as shear stress resulted in adipogenic commitment for MT-derived ASCs and SCs, although the YAP nuclear-to-cytoplasmic ratio indicated higher cell tensions under perfusion, usually associated with preferred osteogenic differentiation.

The poly (l-lactid-co-glycolide; PLGA) fiber component of brushite-forming calcium phosphate cement induces the osteogenic differentiation of human adipose tissue-derived stem cells

A brushite-forming calcium phosphate cement (CPC) was mechanically stabilized by addition of poly (l-lactid-co-glycolide; PLGA) fibers (≤10% w/w). It proved highly biocompatible and its fiber component enhanced bone formation in a sheep lumbar vertebroplasty model. However, possible effects on the osteogenic differentiation of resident mesenchymal stem cells (MSCs) remained unexplored. The present study used a novel approach, simultaneously analyzing the influence of a solid CPC scaffold and its relatively low PLGA proportion (a mimicry of natural bone) on osteogenic, chondrogenic, and adipogenic differentiation, as well as the pluripotency of human adipose tissue-derived mesenchymal stem cells (hASCs). hASCs were cultured on CPC discs with/without PLGA fibers (5% and 10%) in the absence of osteogenic medium for 3, 7, and 14 d. Gene expression of osteogenic markers (Runx2, osterix, alkaline phosphatase, collagen I, osteonectin, osteopontin, osteocalcin), chondrogenic markers (collagen II, Sox9, aggrecan), adipogenic markers (PPARG, Leptin, and FABP4), and pluripotency markers (Nanog, Tert, Rex) was analyzed by RT-PCR. The ability of hASCs to synthesize alkaline phosphatase was also evaluated. Cell number and viability were determined by fluorescein diacetate/propidium iodide staining. Compared to pure CPC, cultivation of hASCs on fiber-reinforced CPC transiently induced the gene expression of Runx2 and osterix (day 3), and long-lastingly augmented the expression of alkaline phosphatase (and its enzyme activity), collagen I, and osteonectin (until day 14). In contrast, augmented expression of all chondrogenic, adipogenic, and pluripotency markers was limited to day 3, followed by significant downregulation. Cultivation of hASCs on fiber-reinforced CPC reduced the cell number, but not the proportion of viable cells (viability > 95%). The PLGA component of fiber-reinforced, brushite-forming CPC supports long-lasting osteogenic differentiation of hASCs, whereas chondrogenesis, adipogenesis, and pluripotency are initially augmented, but subsequently suppressed. In view of parallel animal results, PLGA fibers may represent an interesting clinical target for future improvement of CPC- based bone regeneration.

Hybrid nanocomposite as a chest wall graft with improved integration by adipose-derived stem cells

Surgery of the chest wall is potentially required to cover large defects after  removal of malignant tumours. Usually, inert and non-degradable Gore-Tex serves to replace the missing tissue. However, novel biodegradable materials combined with stem cells are available that stimulate the healing. Based on poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) and pure PLGA, a dual layer biodegradable hybrid nanocomposite was generated. Mouse adipose-derived stem cells were cultered on electrospun disks (ASCs of C57BL/6), and biomechanical tests were performed. The cell-seeded scaffolds were engrafted in C57BL/LY5.1 mice to serve as a chest wall substitute. Cell invasion into the bi-layered material, extent of CD45⁺ cells, inflammatory response, neo-vascularization and ECM composition were determined at 1 and 2 months post-surgery, respectively. The bi-layered hybrid nanocomposite was stable after a 2-week in vitro culture, in contrast to PLGA/aCaP without a PLGA layer. There was a complete biointegration and good vascularization in vivo. The presence of ASCs attracted more CD45⁺ cells (hematopoietic origin) compared to cell-free scaffolds. Inflammatory reaction was similar for both groups (±ASCs) at 8 weeks. A bi-layered hybrid nanocomposite fabricated of electrospun PLGA/aCaP and a reinforcing layer of pristine PLGA is an ideal scaffold for chest wall reconstruction. It is stable and allows a proper host tissue integration. If ASCs are seeded, they attract more CD45⁺ cells, supporting the regeneration process.

Osteogenic Enhancement Between Icariin and Bone Morphogenetic Protein 2: A Potential Osteogenic Compound for Bone Tissue Engineering

Icariin, a typical flavonol glycoside, is the main active component of Herba Epimedii, which was used to cure bone-related diseases in China for centuries. It has been reported that Icariin can be delivered locally by biomaterials and it has an osteogenic potential for bone tissue engineering. Biomimetic calcium phosphate (BioCaP) bone substitute is a novel drug delivery carrier system. Our study aimed to evaluate the osteogenic potential when Icariin was internally incorporated into the BioCaP granules. The BioCaP combined with Icariin and bone morphogenetic protein 2 (BMP-2) was investigated in vitro using an MC3T3-E1 cell line. We also investigated its efficacy to repair 8 mm diameter critical size bone defects in the skull of SD male rats. BioCaP was fabricated according to a well-established biomimetic mineralization process. In vitro, the effects of BioCaP alone or BioCaP with Icariin and/or BMP-2 on cell proliferation and osteogenic differentiation of MC3T3-E1 cells were systematically evaluated. In vivo, BioCaP alone or BioCaP with Icariin and/or BMP-2 were used to study the bone formation in a critical-sized bone defect created in a rat skull. Samples were retrieved for Micro-CT and histological analysis 12 weeks after surgery. The results indicated that BioCaP with or without the incorporation of Icariin had a positive effect on the osteogenic differentiation of MC3T3-E1. BioCaP with Icariin had better osteogenic efficiency, but had no influence on cell proliferation. BioCap + Icariin + BMP-2 showed better osteogenic potential compared with BioCaP with BMP-2 alone. The protein and mRNA expression of alkaline phosphatase and osteocalcin and mineralization were higher as well. In vivo, BioCaP incorporate internally with both Icariin and BMP-2 induced significantly more newly formed bone than the control group and BioCaP with either Icariin or BMP-2 did. Micro-CT analysis revealed that no significant differences were found between the bone mineral density induced by BioCaP with icariin and that induced by BioCaP with BMP-2. Therefore, co-administration of Icariin and BMP-2 was helpful for bone tissue engineering.

The fabrication of biomineralized fiber-aligned PLGA scaffolds and their effect on enhancing osteogenic differentiation of UCMSC cells

The key factor of scaffold design for bone tissue engineering is to mimic the microenvironment of natural bone extracellular matrix (ECM) and guide cell osteogenic differentiation. The biomineralized fiber-aligned PLGA scaffolds (a-PLGA/CaPs) was developed in this study by mimicking the structure and composition of native bone ECM. The aligned PLGA fibers was prepared by wet spinning and then biomineralized via an alternate immersion method. Introduction of a bioceramic component CaP onto the PLGA fibers led to changes in surface roughness and hydrophilicity, which showed to modulate cell adhesion and cell morphology of umbilical cord mesenchymal stem cells (UCMSCs). It was found that organized actin filaments of UCMSCs cultured on both a-PLGA and a-PLGA/CaP scaffolds appeared to follow contact guidance along the aligned fibers, and those cells grown on a-PLGA/CaP scaffolds exhibited a more polarized cellular morphology. The a-PLGA/CaP scaffold with multicycles of mineralization facilitated the cell attachment on the fiber surfaces and then supported better cell adhesion and contact guidance, leading to enhancement in following proliferation and osteogenic differentiation of UCMSCs. Our results give some insights into the regulation of cell behaviors through design of ECM-mimicking structure and composition and provide an alternative wet-spun fiber-aligned scaffold with HA-mineralized layer for bone tissue engineering application.

Non-viral gene delivery systems for tissue repair and regeneration

Critical tissue defects frequently result from trauma, burns, chronic wounds and/or surgery. The ideal treatment for such tissue loss is autografting, but donor sites are often limited. Tissue engineering (TE) is an inspiring alternative for tissue repair and regeneration (TRR). One of the current state-of-the-art methods for TRR is gene therapy. Non-viral gene delivery systems (nVGDS) have great potential for TE and have several advantages over viral delivery including lower immunogenicity and toxicity, better cell specificity, better modifiability, and higher productivity. However, there is no ideal nVGDS for TRR, hence, there is widespread research to improve their properties. This review introduces the basic principles and key aspects of commonly-used nVGDSs. We focus on recent advances in their applications, current challenges, and future directions.

PEG hydrogel containing calcium-releasing particles and mesenchymal stromal cells promote vessel maturation

The use of human mesenchymal stromal cells (hMSC) for treating diseased tissues with poor vascularization has received significant attention, but low cell survival has hampered its translation to the clinic. Bioglasses and glass-ceramics have also been suggested as therapeutic agents for stimulating angiogenesis in soft tissues, but these effects need further evaluation in vivo. In this study, calcium-releasing particles and hMSC were combined within a hydrogel to examine their vasculogenic potential in vitro and in vivo. The particles provided sustained calcium release and showed proangiogenic stimulation in a chorioallantoic membrane (CAM) assay. The number of hMSC encapsulated in a degradable RGD-functionalized PEG hydrogel containing particles remained constant over time and IGF-1 release was increased. When implanted in the epidydimal fat pad of immunocompromised mice, this composite material improved cell survival and stimulated vessel formation and maturation. Thus, the combination of hMSC and calcium-releasing glass-ceramics represents a new strategy to achieve vessel stabilization, a key factor in the revascularization of ischemic tissues.

STATEMENT OF SIGNIFICANCE

Increasing blood vessel formation in diseased tissues with poor vascularization is a current clinical challenge. Cell therapy using human mesenchymal stem cells has received considerable interest, but low cell survival has hampered its translation to the clinic. Bioglasses and glass-ceramics have been explored as therapeutic agents for stimulating angiogenesis in soft tissues, but these effects need further evaluation in vivo. By incorporating both human mesenchymal stem cells and glass-ceramic particles in an implantable hydrogel, this study provides insights into the vasculogenic potential in soft tissues of the combined strategies. Enhancement of vessel formation and maturation supports further investigation of this strategy.

Effects of seeding adipose-derived stem cells on electrospun nanocomposite used as chest wall graft in a murine model

Malignant neoplasms infiltrating the chest wall often requires resection of the thoracic wall. To replace the defect, Gore-Tex^® is usually employed as the gold standard material, however, Gore-Tex^® is inert and not degradable. Novel materials are nowadays available which allow a full bio-integration due to their non-toxic degradability. Additionally, stem cell seeding has the capacity to reduce inflammatory response towards such grafts, thus integrating it better into the host organism.

Response of human dental pulp cells to a silver-containing PLGA/TCP-nanofabric as a potential antibacterial regenerative pulp-capping material

Background

Damage or exposure of the dental pulp requires immediate therapeutic intervention.

Methods

This study assessed the biocompatibility of a silver-containing PLGA/TCP-nanofabric scaffold (PLGA/Ag-TCP) in two in vitro models, i.e. the material adapted on pre-cultured cells and cells directly cultured on the material, respectively. Collagen saffolds with and without hyaluronan acid (Coll-HA; Coll) using both cell culturing methods and cells growing on culture plates served as reference. Cell viability and proliferation were assessed after 24, 48, and 72 h based on formazan formation and BrdU incorporation. Scaffolds were harvested. Gene expression of interleukin(IL)-6, tumor necrosis factor (TNF)-alpha, and alkaline phosphatase (AP) was assessed 24 h after stimulation.

Results

In both models formazan formation and BrdU incorporation was reduced by PLGA/Ag-TCP on dental pulp cells, while no significant reduction was found in cells with Coll and Coll-HA. Cells with PLGA/Ag-TCP for 72 h showed similar relative BrdU incorporation than cells stimulated with Coll and Coll-HA. A prominent increase in the pro-inflammatory genes IL-6 and TNF-α was observed when cells were cultured with PLGA/Ag-TCP compared to the other groups. This increase was parallel with a slight increase in AP expression. Overall, no differences between the two culture methods were observed.

Conclusions

PLGA/Ag-TCP decreased viability and proliferation rate of human dental pulp cells and increased the pro-inflammatory capacity and alkaline phosphatase expression. Whether these cellular responses observed in vitro translate into pulp regeneration in vivo will be assessed in further studies.

Biodegradable mesoporous delivery system for biomineralization precursors

Scaffold supplements such as nanoparticles, components of the extracellular matrix, or growth factors have been incorporated in conventional scaffold materials to produce smart scaffolds for tissue engineering of damaged hard tissues. Due to increasing concerns on the clinical side effects of using large doses of recombinant bone-morphogenetic protein-2 in bone surgery, it is desirable to develop an alternative nanoscale scaffold supplement that is not only osteoinductive, but is also multifunctional in that it can perform other significant bone regenerative roles apart from stimulation of osteogenic differentiation. Because both amorphous calcium phosphate (ACP) and silica are osteoinductive, a biodegradable, nonfunctionalized, expanded-pore mesoporous silica nanoparticle carrier was developed for loading, storage, and sustained release of a novel, biosilicification-inspired, polyamine-stabilized liquid precursor phase of ACP for collagen biomineralization and for release of orthosilicic acid, both of which are conducive to bone growth. Positively charged poly(allylamine)-stabilized ACP (PAH-ACP) could be effectively loaded and released from nonfunctionalized expanded-pore mesoporous silica nanoparticles (pMSN). The PAH-ACP released from loaded pMSN still retained its ability to infiltrate and mineralize collagen fibrils. Complete degradation of pMSN occurred following unloading of their PAH-ACP cargo. Because PAH-ACP loaded pMSN possesses relatively low cytotoxicity to human bone marrow-derived mesenchymal stem cells, these nanoparticles may be blended with any osteoconductive scaffold with macro- and microporosities as a versatile scaffold supplement to enhance bone regeneration.

Effects of Sr-HT-Gahnite on osteogenesis and angiogenesis by adipose derived stem cells for critical-sized calvarial defect repair

Tissue engineering strategies to construct vascularized bone grafts are now attracting much attention. Strontium-hardystonite-Gahnite (Sr-HT-Gahnite) is a strong, highly porous, and biocompatible calcium silicate based bio-ceramic that contains strontium and zinc ions. Adipose derived stem cells (ASCs) have been demonstrated to have the ability in promoting osteogenesis and angiogenesis. In this study, the effects of Sr-HT-Gahnite on cell morphology, cell proliferation, and osteogenic differentiation of ASCs were systematically investigated. The cell proliferation, migration and angiogenic differentiation of human umbilical vein endothelial cell (HUVECs) were studied. Beta-tricalcium phosphate/hydroxyapatite (TCP/HA) bioceramic scaffolds were set as the control biomaterial. Both bio-ceramics exhibited no adverse influence on cell viability. The Sr-HT-Gahnite scaffolds promoted cell attachment and alkaline phosphatase (ALP) activity of ASCs. The Sr-HT-Gahnite dissolution products enhanced ALP activity, matrix mineralization, and angiogenic differentiation of ASCs. They could also improve cell proliferation, migration, and angiogenic differentiation of HUVECs. Levels of in vivo bone formation with Sr-HT Gahnite were significantly higher than that for TCP/HA. The combination of Sr-HT-Gahnite and ASCs promoted both osteogenesis and angiogenesis in vivo study, compared to Sr-HT-Gahnite and TCP/HA bio-ceramics when administered alone, suggesting Sr-HT-Gahnite can act as a carrier for ASCs for construction of vascularized tissue-engineered bone.

Effects of HAp and TCP in constructing tissue engineering scaffolds for bone repair

TCP possesses superior long-term effects in structuring tissue engineering scaffold for bone repair compared to HAp, though TCP lags behind HAp in the early repair period.

The use of rats and mice as animal models in ex vivo bone growth and development studies

In vivo animal experimentation has been one of the cornerstones of biological and biomedical research, particularly in the field of clinical medicine and pharmaceuticals. The conventional in vivo model system is invariably associated with high production costs and strict ethical considerations. These limitations led to the evolution of an ex vivo model system which partially or completely surmounted some of the constraints faced in an in vivo model system. The ex vivo rodent bone culture system has been used to elucidate the understanding of skeletal physiology and pathophysiology for more than 90 years. This review attempts to provide a brief summary of the historical evolution of the rodent bone culture system with emphasis on the strengths and limitations of the model. It encompasses the frequency of use of rats and mice for ex vivo bone studies, nutritional requirements in ex vivo bone growth and emerging developments and technologies. This compilation of information could assist researchers in the field of regenerative medicine and bone tissue engineering towards a better understanding of skeletal growth and development for application in general clinical medicine.Cite this article: A. A. Abubakar, M. M. Noordin, T. I. Azmi, U. Kaka, M. Y. Loqman. The use of rats and mice as animal models in ex vivo bone growth and development studies. Bone Joint Res 2016;5:610-618. DOI: 10.1302/2046-3758.512.BJR-2016-0102.R2.

The chorioallantoic membrane (CAM) assay for the study of human bone regeneration: a refinement animal model for tissue engineering

Biomaterial development for tissue engineering applications is rapidly increasing but necessitates efficacy and safety testing prior to clinical application. Current in vitro and in vivo models hold a number of limitations, including expense, lack of correlation between animal models and human outcomes and the need to perform invasive procedures on animals; hence requiring new predictive screening methods. In the present study we tested the hypothesis that the chick embryo chorioallantoic membrane (CAM) can be used as a bioreactor to culture and study the regeneration of human living bone. We extracted bone cylinders from human femoral heads, simulated an injury using a drill-hole defect, and implanted the bone on CAM or in vitro control-culture. Micro-computed tomography (μCT) was used to quantify the magnitude and location of bone volume changes followed by histological analyses to assess bone repair. CAM blood vessels were observed to infiltrate the human bone cylinder and maintain human cell viability. Histological evaluation revealed extensive extracellular matrix deposition in proximity to endochondral condensations (Sox9+) on the CAM-implanted bone cylinders, correlating with a significant increase in bone volume by μCT analysis (p < 0.01). This human-avian system offers a simple refinement model for animal research and a step towards a humanized in vivo model for tissue engineering.

A Long-Acting BMP-2 Release System Based on Poly(3-hydroxybutyrate) Nanoparticles Modified by Amphiphilic Phospholipid for Osteogenic Differentiation

We explored a novel poly(3-hydroxybutyrate) (PHB) nanoparticle loaded with hydrophilic recombinant human BMP-2 with amphiphilic phospholipid (BPC-PHB NP) for a rapid-acting and long-acting delivery system of BMP-2 for osteogenic differentiation. The BPC-PHB NPs were prepared by a solvent evaporation method and showed a spherical particle with a mean particle size of 253.4 nm, mean zeta potential of −22.42 mV, and high entrapment efficiency of 77.18%, respectively. For BPC-PHB NPs, a short initial burst release of BMP-2 from NPs in 24 h was found and it has steadily risen to reach about 80% in 20 days for in vitro test. BPC-PHB NPs significantly reduced the burst release of BMP-2, as compared to that of PHB NPs loading BMP-2 without PL (B-PHB NPs). BPC-PHB NPs maintained the content of BMP-2 for a long-term osteogenic differentiation. The OCT-1 cells with BPC-PHB NPs have high ALP activity in comparison with others. The gene markers for osteogenic differentiation were significantly upregulated for sample with BPC-PHB NPs, implying that BPC-PHB NPs can be used as a rapid-acting and long-acting BMP-2 delivery system for osteogenic differentiation.

Carbon nanotube (CNT) and nanofibrillated cellulose (NFC) reinforcement effect on thermoplastic polyurethane (TPU) scaffolds fabricated via phase separation using dimethyl sulfoxide (DMSO) as solvent

Although phase separation is a simple method of preparing tissue engineering scaffolds, it suffers from organic solvent residual in the scaffold. Searching for nontoxic solvents and developing effective solvent removal methods are current challenges in scaffold fabrication. In this study, thermoplastic polyurethane (TPU) scaffolds containing carbon nanotubes (CNTs) or nanofibrillated cellulose fibers (NFCs) were prepared using low toxicity dimethyl sulfoxide (DMSO) as a solvent. The effects of two solvent removal approaches on the final scaffold morphology were studied. The freeze drying method caused large pores, with small pores on the pore walls, which created connections between the pores. Meanwhile, the leaching and freeze drying method led to interconnected fine pores with smaller pore diameters. The nucleation effect of CNTs and the phase separation behavior of NFCs in the TPU solution resulted in significant differences in the microstructures of the resulting scaffolds. The mechanical performance of the nanocomposite scaffolds with different morphologies was investigated. Generally, the scaffolds with a fine pore structure showed higher compressive properties, and both the CNTs and NFCs improved the compressive properties of the scaffolds, with greater enhancement found in TPU/NFC nanocomposite scaffolds. In addition, all scaffolds showed good sustainability under cyclical load bearing, and the biocompatibility of the scaffolds was verified via 3T3 fibroblast cell culture.

Comparison of viability and antioxidant capacity between canine adipose-derived mesenchymal stem cells and heme oxygenase-1-overexpressed cells after freeze-thawing

Allogenic adipose-derived mesenchymal stem cells (Ad-MSCs) are an alternative source for cytotherapy owing to their antioxidant and anti-inflammatory effects. Frozen-thawed allogenic Ad-MSCs can be used instantly for this purpose. However, the viability and function of frozen-thawed Ad-MSCs have not been clearly evaluated. The purpose of this study was to compare the viability and function of Ad-MSCs and heme oxygenase-1 (HO-1)-overexpressed Ad-MSCs in vitro after freeze-thawing. The viability, proliferation, antioxidant capacity and mRNA gene expression of growth factors were evaluated. Frozen-thawed cells showed significantly lower viability than fresh cells (77% for Ad-MSCs and 71% for HO-1 Ad-MSCs, P<0.01). However, the proliferation rate of frozen-thawed Ad-MSCs increased and did not differ from that of fresh Ad-MSCs after 3 days of culture. In contrast, the proliferation rate of HO-1-overexpressed Ad-MSCs was lower than that of Ad-MSCs. The mRNA expression levels of TGF-β, HGF and VEGF did not differ between fresh and frozen-thawed Ad-MSCs, but COX-2 and IL-6 had significantly higher mRNA expression in frozen cells than fresh cells (P<0.05). Fresh Ad-MSCs exhibited higher HO-1 mRNA expression than frozen-thawed Ad-MSCs, and fresh HO-1-overexpressed Ad-MSCs exhibited higher than fresh Ad-MSCs (P<0.05). However, there was no significant difference between fresh and frozen HO-1-overexpressed Ad-MSCs. The antioxidant capacity of HO-1-overexpressed Ad-MSCs was significantly higher than that of Ad-MSCs. Cryopreservation of Ad-MSCs negatively affects viability and antioxidant capacity, and HO-1-overexpressed Ad-MSCs might be useful to maximize the effect of Ad-MSCs for cytotherapy.

Autologous osteoblast transplantation, an innovative method of bone defect treatment: role of a tissue and cell bank in the process

BACKGROUND

The idea of cell treatment of various diseases and medical conditions has become very popular. Some procedures are well established, as is autologous chondrocyte implantation, whereas others are still in the process of early development, laboratory experiments, and some clinical trials.

METHODS

This report is devoted to an example of an emerging cell treatment: bone augmentation with the use of autologous cells and its legal and technical background. Various requirements set by law must be met by tissue banks performing cell seeding of grafts. In Europe, the requirements are described in directives 2004/23/EC, 2006/17/EC, 2006/86/EC, and in the regulation 2007/1394/EC.

RESULTS

Revitalization of biostatic allografts gives new, promising tools for creation of functional parts of organs; brings the methodology used in tissue banks closer to tissue engineering; places the enterprise in the mainstream of advanced biotechnology; allows the full potential of tissue allografts; and opens a new, large area for clinical and laboratory research. Cell and tissue processing also have a financial impact on the treatment: it produces additional expenditures.

CONCLUSIONS

Clinical effectiveness will be the most decisive factor of whether this innovative treatment will be applied in a particular type of medical condition. From a tissue establishment perspective, the most important issue is to develop a procedure that ensures safety for the patient in graft quality terms.

Smart scaffolds in bone tissue engineering: A systematic review of literature

AIM: To improve osteogenic differentiation and attachment of cells.

METHODS: An electronic search was conducted in PubMed from January 2004 to December 2013. Studies which performed smart modifications on conventional bone scaffold materials were included. Scaffolds with controlled release or encapsulation of bioactive molecules were not included. Experiments which did not investigate response of cells toward the scaffold (cell attachment, proliferation or osteoblastic differentiation) were excluded.

RESULTS: Among 1458 studies, 38 met the inclusion and exclusion criteria. The main scaffold varied extensively among the included studies. Smart modifications included addition of growth factors (group I-11 studies), extracellular matrix-like molecules (group II-13 studies) and nanoparticles (nano-HA) (group III-17 studies). In all groups, surface coating was the most commonly applied approach for smart modification of scaffolds. In group I, bone morphogenetic proteins were mainly used as growth factor stabilized on polycaprolactone (PCL). In group II, collagen 1 in combination with PCL, hydroxyapatite (HA) and tricalcium phosphate were the most frequent scaffolds used. In the third group, nano-HA with PCL and chitosan were used the most. As variable methods were used, a thorough and comprehensible compare between the results and approaches was unattainable.

CONCLUSION: Regarding the variability in methodology of these in vitro studies it was demonstrated that smart modification of scaffolds can improve tissue properties.

The role of pleiotrophin in bone repair

Bone has an enormous capacity for growth, regeneration, and remodelling, largely due to induction of osteoblasts that are recruited to the site of bone formation. Although the pathways involved have not been fully elucidated, it is well accepted that the immediate environment of the cells is likely to play a role via cell–matrix interactions, mediated by several growth factors. Formation of new blood vessels is also significant and interdependent to bone formation, suggesting that enhancement of angiogenesis could be beneficial during the process of bone repair. Pleiotrophin (PTN), also called osteoblast-specific factor 1, is a heparin-binding angiogenic growth factor, with a well-defined and significant role in both physiological and pathological angiogenesis. In this review we summarise the existing evidence on the role of PTN in bone repair.

Bone marrow mesenchymal stem cell aspirates from alternative sources: is the knee as good as the iliac crest?

INTRODUCTION

The most common method to obtain human mesenchymal stem cells (MSCs) is bone marrow aspiration from the iliac crest, but MSCs have also been isolated from different bones. The main purpose of this study was to compare bone marrow MSCs aspirated from the metaphysis of the distal femur and the proximal tibia with those obtained from the iliac crest, and to determine whether these locations represent potential alternative sources of MSCs for research and clinical application.

MATERIALS AND METHODS

Bone marrow was aspirated from the iliac crest and the metaphysis of the distal femur and the proximal tibia during total knee arthroplasty in 20 patients. The aspirates were centrifuged by density gradient, then mononucleated cell (MNC) concentration in the different aspirates was determined using a Coulter counter. MSCs were isolated, cultivated and characterised by their immunophenotype and by their in vitro potential for differentiation into osteoblasts, chondroblasts and adipocytes in specific media. Expansion and cell viability were quantified using trypan blue staining and cell counting with a haemocytometer (Neubauer chamber). The three sources were compared in terms of MNC concentration, viability of the cultures and presence of MSC using the Wilcoxon test.

RESULTS

MNC concentration was significantly higher in the iliac crest (10.05 Millions/ml) compared with the femur (0.67 Millions/ml) and tibia (1.7 Millions/ml). Culture success rates were 90%, 71% and 47% for MSCs from the iliac crest, femur and tibia, respectively. Flow cytometry analysis showed the presence of CD90+, CD105+, CD73+, VEGF+, CD71+, HLA-DR-, CD45-, CD34-, CD19-, and CD14- cells. The immunophenotype pattern of MSCs was similar for the three locations. Trilineage differentiation was achieved with all samples.

CONCLUSIONS

MSCs can be found in bone marrow from the metaphysis of both the distal femur and the proximal tibia. The phenotype and differentiation potential of these cells are similar to those of bone marrow MSCs from the iliac crest. Bone marrow aspiration from these locations is a relatively easy and safe alternative to that from the iliac crest for obtaining MSCs. Further study is required to assess whether the concentrations of MSCs obtained from these sources are sufficient for one-step therapeutic purposes.

Investigating a potential biological treatment to prevent pathological fractures caused by unicameral bone cysts in children under 8 years

INTRODUCTION

There is no consensus on when and how to treat unicameral bone cysts (UBCs), partly because of a lack of knowledge of the aetiology.

PURPOSE

To review the different treatment techniques for UBCs and to describe our results with a single injection of autogenous bone marrow (BM) mixed with demineralised bone matrix (DBM) in very young children.

PATIENTS AND METHODS

We reviewed five patients under the age of 8 years with UBCs treated by percutaneous aspiration and a single injection of BM associated with DBM. The cyst was located in the proximal humerus in four patients and in the proximal femur in one patient. Assessment of the need for surgery was based on the clinical and radiographic suspicion of new pathological fractures. The administration of a second injection, when necessary, was based on the surgeon's judgement regarding the risk of fracture. The mean follow-up after first injection was 41 months.

RESULTS

There were no complications related to the procedure, except a non-displaced fracture, which healed without problems. All patients were pain free and progressively resumed their activities without restriction until a new fracture occurred in two cases. According to Capanna's classification, only one case healed completely (grade 1), one lesion was classified as grade 2, and there were three recurrences at 11, 12 and 27 months after initial treatment (grade 3). The final outcome was treatment failure for three out of the five patients. Two patients were treated with a second injection and one patient is waiting for surgery.

CONCLUSION

A single injection of aspirated autogenous BM mixed with DBM in very young children with active UBCs at risk of fracture is very simple, comfortable and safe. Nevertheless, the results seem to be unpredictable and are probably more dependent on the natural evolution of the cyst than on the treatment. Further comparative studies with larger sample numbers are needed.

Application of adipose tissue-derived stem cells in a rat rotator cuff repair model

INTRODUCTION

Healing tissue of the rotator cuff does not regenerate the native enthesis; fibrovascular scar tissue is formed instead and this has less favourable biomechanical properties. The purpose of this study was to determine if the application of adipose tissue-derived stem cells (ASCs) could improve biomechanical and histological properties of the repair.

MATERIAL AND METHODS

Fifty Sprague-Dawley rats underwent detachment and repair of the supraspinatus tendon, 32 for the biomechanical study and 18 for the histological examination. Animals were randomised in two groups to receive either a collagen carrier alone (untreated group) or the carrier plus 2×10(6) ASCs (ASCs group). A control group (suture only) was also included for the histological examination. The animals were sacrificed at 2 and 4 weeks for the biomechanical study and at 24 hours, and 1 and 4 weeks for the histological study. Maximum load failure energy, elastic energy, mechanical deformation, stiffness and absorbed energy were measured. Immunofluorescence testing was conducted to show the presence of ASCs in the repair area.

RESULTS

There were no differences between the untreated group and the ASCs group in any of the biomechanical variables at the 2- and 4-week time points. The mechanical deformation before failure was higher for the ASCs group compared with the untreated group at 2 weeks and 4 weeks (p=0.09), as was the absorbed energy (p=0.06). Differences in maximum load to failure between 2 and 4 weeks were significant for the untreated group (p=0.04) but not for the ASCs group (p=0.17). Histological examination showed less acute inflammation with diminished presence of oedema and neutrophils in the ASCs group. There were no differences in the orientation of collagen fibres between groups at either time point. In the ASCs group, collagen was present only at the last time point.

CONCLUSION

The application of ASCs in a rat rotator cuff repair model did not improve the biomechanical properties of the tendon-to-bone healing. However, the ASCs group showed less inflammation, which may lead to a more elastic repair and less scarred healing.

Improved repair of bone defects with prevascularized tissue-engineered bones constructed in a perfusion bioreactor

Vascularization of tissue-engineered bones is critical to achieving satisfactory repair of bone defects. The authors investigated the use of prevascularized tissue-engineered bone for repairing bone defects. The new bone was greater in the prevascularized group than in the non-vascularized group, indicating that prevascularized tissue-engineered bone improves the repair of bone defects. [Orthopedics. 2014; 37(10):685-690.].

Tissue-engineered bone constructed in a bioreactor for repairing critical-sized bone defects in sheep

PURPOSE

Repair of bone defects, particularly critical-sized bone defects, is a considerable challenge in orthopaedics. Tissue-engineered bones provide an effective approach. However, previous studies mainly focused on the repair of bone defects in small animals. For better clinical application, repairing critical-sized bone defects in large animals must be studied. This study investigated the effect of a tissue-engineered bone for repairing critical-sized bone defect in sheep.

METHODS

A tissue-engineered bone was constructed by culturing bone marrow mesenchymal-stem-cell-derived osteoblast cells seeded in a porous β-tricalcium phosphate ceramic (β-TCP) scaffold in a perfusion bioreactor. A critical-sized bone defect in sheep was repaired with the tissue-engineered bone. At the eighth and 16th week after the implantation of the tissue-engineered bone, X-ray examination and histological analysis were performed to evaluate the defect. The bone defect with only the β-TCP scaffold served as the control.

RESULT

X-ray showed that the bone defect was successfully repaired 16 weeks after implantation of the tissue-engineered bone; histological sections showed that a sufficient volume of new bones formed in β-TCP 16 weeks after implantation. Eight and 16 weeks after implantation, the volume of new bones that formed in the tissue-engineered bone group was more than that in the β-TCP scaffold group (P < 0.05).

CONCLUSION

Tissue-engineered bone improved osteogenesis in vivo and enhanced the ability to repair critical-sized bone defects in large animals.

Proliferation of ASC-derived endothelial cells in a 3D electrospun mesh: impact of bone-biomimetic nanocomposite and co-culture with ASC-derived osteoblasts

BACKGROUND

Fractures with a critical size bone defect are associated with high rates of delayed- and non-union. The treatment of such complications remains a serious issue in orthopaedic surgery. Adipose derived stem cells (ASCs) combined with biomimetic materials can potentially be used to increase fracture healing. Nevertheless, a number of requirements have to be fulfilled; in particular, the insufficient vascularisation of the bone constructs. Here, the objectives were to study the impact of ASC-derived osteoblasts on ASC-derived endothelial cells in a 3D co-culture and the effect of 40wt% of amorphous calcium phosphate nanoparticles on the proliferation and differentiation of ASC-derived endothelial cells when present in PLGA.

MATERIALS AND METHODS

Five primary ASC lines were differentiated towards osteoblasts (OBs) and endothelial cells (ECs) and two of them were chosen based on quantitative PCR results. Either a mono-culture of ASC-derived EC or a co-culture of ASC-derived EC with ASC-derived OB (1:1) was seeded on an electrospun nanocomposite of poly-(lactic-co-glycolic acid) and amorphous calcium phosphate nanoparticles (PLGA/a-CaP; reference: PLGA). The proliferation behaviour was determined histomorphometrically in different zones and the expression of von Willebrand Factor (vWF) was quantified.

RESULTS

Independently of the fat source (biologic variability), ASC-derived osteoblasts decelerated the proliferation behaviour of ASC-derived endothelial cells in the co-culture compared to the mono-culture. However, expression of vWF was clearly stronger in the co-culture, indicating further differentiation of the ASC-derived EC into the EC lineage. Moreover, the presence of a-CaP nanoparticles in the scaffold slowed the proliferation behaviour of the co-culture cells, too, going along with a further differentiation of the ASC-derived OB, when compared to pure PLGA scaffolds.

CONCLUSIONS

This study revealed significant findings for bone tissue-engineering. Co-cultures of ASC-derived EC and ASC-derived OB stimulate each other's further differentiation. A nanocomposite with a-CaP nanoparticles offers higher mechanical stability, bioactivity and osteoconductivity compared to mere PLGA and can easily be seeded with pre-differentiated EC and OB.