An Osteosarcoma Model by 3D Printed Polyurethane Scaffold and In Vitro Generated Bone Extracellular Matrix.

Osteosarcoma is a primary bone tumor characterized by a dismal prognosis, especially in the case of recurrent disease or metastases. Therefore, tools to understand in-depth osteosarcoma progression and ultimately develop new therapeutics are urgently required. 3D in vitro models can provide an optimal option, as they are highly reproducible, yet sufficiently complex, thus reliable alternatives to 2D in vitro and in vivo models. Here, we describe 3D in vitro osteosarcoma models prepared by printing polyurethane (PU) by fused deposition modeling, further enriched with human mesenchymal stromal cell (hMSC)-secreted biomolecules. We printed scaffolds with different morphologies by changing their design (i.e., the distance between printed filaments and printed patterns) to obtain different pore geometry, size, and distribution. The printed PU scaffolds were stable during in vitro cultures, showed adequate porosity (55-67%) and tunable mechanical properties (Young's modulus ranging in 0.5-4.0 MPa), and resulted in cytocompatible. We developed the in vitro model by seeding SAOS-2 cells on the optimal PU scaffold (i.e., 0.7 mm inter-filament distance, 60° pattern), by testing different pre-conditioning factors: none, undifferentiated hMSC-secreted, and osteo-differentiated hMSC-secreted extracellular matrix (ECM), which were obtained by cell lysis before SAOS-2 seeding. Scaffolds pre-cultured with osteo-differentiated hMSCs, subsequently lysed, and seeded with SAOS-2 cells showed optimal colonization, thus disclosing a suitable biomimetic microenvironment for osteosarcoma cells, which can be useful both in tumor biology study and, possibly, treatment.

Piezoelectric Signals in Vascularized Bone Regeneration.

The demand for bone substitutes is increasing in Western countries. Bone graft substitutes aim to provide reconstructive surgeons with off-the-shelf alternatives to the natural bone taken from humans or animal species. Under the tissue engineering paradigm, biomaterial scaffolds can be designed by incorporating bone stem cells to decrease the disadvantages of traditional tissue grafts. However, the effective clinical application of tissue-engineered bone is limited by insufficient neovascularization. As bone is a highly vascularized tissue, new strategies to promote both osteogenesis and vasculogenesis within the scaffolds need to be considered for a successful regeneration. It has been demonstrated that bone and blood vases are piezoelectric, namely, electric signals are locally produced upon mechanical stimulation of these tissues. The specific effects of electric charge generation on different cells are not fully understood, but a substantial amount of evidence has suggested their functional and physiological roles. This review summarizes the special contribution of piezoelectricity as a stimulatory signal for bone and vascular tissue regeneration, including osteogenesis, angiogenesis, vascular repair, and tissue engineering, by considering different stem cell sources entailed with osteogenic and angiogenic potential, aimed at collecting the key findings that may enable the development of successful vascularized bone replacements useful in orthopedic and otologic surgery.

Raman spectroscopy of osteosarcoma cells.

Osteosarcoma is the most common primary malignant bone tumor. In the last years, several studies have demonstrated that the increase of Hydroxyapatite (HA) and Interleukin-6 (IL-6) syntheses compared to those expressed by normal osteoblasts could be used to detect the degree of malignancy of osteosarcoma cells. Conventional biochemical methods widely employed to evaluate bone cell differentiation, including normal and cancerous phenotypes, are time consuming and may require a large amount of cells. HA is a mineral form of calcium phosphate whose presence increases with maturation of osteosarcoma cells. Analogously, IL-6 is a fundamental cytokine whose production is highly increased in osteosarcoma cells. In this study, we employ Raman spectroscopy to the identification and discrimination of osteosarcoma cells from osteo-differentiated mesenchymal stromal cells (MSCs) by detecting the presence of HA and IL-6. However, while the identification of HA is facilitated by the characteristic peak at 960 cm-1, corresponding to symmetric stretching (P-O) mode, the quantification of IL-6 it is much more elusive, being its Raman signal characterized by cysteine, but also by phenylalanine, amide I II and III whose signals are common to other proteins. Supported by an accurate multivariate analysis, the results show that Raman spectroscopy is a high sensitivity technique dealing out a direct and quantitative measurement of specific mineralization levels of osteosarcoma cells. In turn, by exploiting the Surface-Enhanced Raman Scattering stimulated by internalized Gold Nanoshells (AuNSs) and combined with scanning probe microscopies, we were able to employ Raman spectroscopy to study subcellular components locally.

Pooled human serum: A new culture supplement for bioreactor-based cell therapies. Preliminary results.

BACKGROUND: Bone Marrow MSCs are an appealing source for several cell-based therapies. Many bioreactors, as the Quantum Cell Expansion System, have been developed to generate a large number of MSCs under Good Manufacturing Practice conditions by using Human Platelet Lysate (HPL). Previously we isolated in the human bone marrow a novel cell population, named Mesodermal Progenitor Cells (MPCs), which we identified as precursors of MSCs. MPCs could represent an important cell source for regenerative medicine applications. As HPL gives rise to a homogeneus MSC population, limiting the harvesting of other cell types, in this study we investigated the efficacy of pooled human AB serum (ABS) to provide clinically relevant numbers of both MSCs and MPCs for regenerative medicine applications by using the Quantum System. METHODS: Bone marrow aspirates were obtained from healthy adult individuals undergoing routine total hip replacement surgery and used to generate primary cultures in the bioreactor. HPL and ABS were tested as supplements to culture medium. Morphological observations, cytofluorimetric analysis, lactate and glucose level assessment were performed. RESULTS: ABS gave rise to both heterogeneous MSC and MPC population. About 95% of cells cultured in HPL showed a fibroblast-like morphology and typical mesenchymal surface markers, but MPCs were scarcely represented. DISCUSSION: The use of ABS appeared to sustain a large scale MSC production, as well as the recovery of a subset of MPCs, and resulted a suitable alternative to HPL in the cell generation based on the Quantum System.

CD18-mediated adhesion is required for the induction of a proinflammatory phenotype in lung epithelial cells by mononuclear cell-derived extracellular vesicles.

Extracellular vesicles are submicron vesicles that upregulate the synthesis of proinflammatory mediators by lung epithelial cells. We investigated whether these structures adhere to lung epithelial cells, and whether adhesion is a prerequisite for their proinflammatory activity. Extracellular vesicles were generated by stimulation of normal human mononuclear cells with the calcium ionophore A23187, and labelled with carboxyfluorescein diacetate succinimidyl ester. Adhesion of vesicles to monolayers of immortalized bronchial epithelial (16HBE) and alveolar (A549) cells was analyzed by fluorescence microscopy. The role of candidate adhesion receptors was evaluated with inhibitory monoclonal antibodies and soluble peptides. The synthesis of proinflammatory mediators was assessed by ELISA. Transmission electron microscopy confirmed the generation of closed vesicles with an approximate size range between 50 and 600 nm. Adhesion of extracellular vesicles to epithelial cells was upregulated upon stimulation of the latter with tumor necrosis factor-α. Adhesion was blocked by an anti-CD18 antibody, by peptides containing the sequence RGD and, to a lesser extent, by an antibody to ICAM-1. The same molecules also blocked the upregulation of the synthesis of interleukin-8 and monocyte chemotactic protein-1 induced by extracellular vesicles. CD18-mediated adhesion of extracellular vesicles is a prerequisite for their proinflammatory activity.

Bovine bone matrix/poly(l-lactic-co-ε-caprolactone)/gelatin hybrid scaffold (SmartBone®) for maxillary sinus augmentation: A histologic study on bone regeneration.

The ideal scaffold for bone regeneration is required to be highly porous, non-immunogenic, biostable until the new tissue formation, bioresorbable and osteoconductive. This study aimed at investigating the process of new bone formation in patients treated with granular SmartBone® for sinus augmentation, providing an extensive histologic analysis. Five biopsies were collected at 4-9 months post SmartBone® implantation and processed for histochemistry and immunohistochemistry. Histomorphometric analysis was performed. Bone-particle conductivity index (BPCi) was used to assess SmartBone® osteoconductivity. At 4 months, SmartBone® (12%) and new bone (43.9%) were both present and surrounded by vascularized connective tissue (37.2%). New bone was grown on SmartBone® (BPCi=0.22). At 6 months, SmartBone® was almost completely resorbed (0.5%) and new bone was massively present (80.8%). At 7 and 9 months, new bone accounted for a large volume fraction (79.3% and 67.4%, respectively) and SmartBone® was resorbed (0.5% and 0%, respectively). Well-oriented lamellae and bone scars, typical of mature bone, were observed. In all the biopsies, bone matrix biomolecules and active osteoblasts were visible. The absence of inflammatory cells confirmed SmartBone® biocompatibility and non-immunogenicity. These data indicate that SmartBone® is osteoconductive, promotes fast bone regeneration, leading to mature bone formation in about 7 months.

Mesenchymal Stromal Cell Culture and Delivery in Autologous Conditions: A Smart Approach for Orthopedic Applications.

Human Mesenchymal Stromal Cells (hMSCs) are cultured in vitro with different media. Limits on their use in clinical settings, however, mainly depend on potential biohazard and inflammation risks exerted by xenogeneic nutrients for their culture. Human derivatives or recombinant materials are the first choice candidates to reduce these reactions. Therefore, culture supplements and materials of autologous origin represent the best nutrients and the safest products. Here, we describe a new protocol for the isolation and culture of bone marrow hMSCs in autologous conditions - namely, patient-derived serum as a supplement for the culture medium and fibrin as a scaffold for hMSC administration. Indeed, hMSC/fibrin clot constructs could be extremely useful for several clinical applications. In particular, we focus on their use in orthopedic surgery, where the fibrin clot derived from the donor's own blood allowed effective cell delivery and nutrient/waste exchanges. To ensure optimal safety conditions, it is of the utmost importance to avoid the risks of hMSC transformation and tissue overgrowth. For these reasons, the approach described in this paper also indicates a minimally ex vivo hMSC expansion, to reduce cell senescence and morphologic changes, and short-term osteo-differentiation before implantation, to induce osteogenic lineage specification, thus decreasing the risk of subsequent uncontrolled proliferation.

Multiscale fabrication of biomimetic scaffolds for tympanic membrane tissue engineering.

The tympanic membrane (TM) is a thin tissue able to efficiently collect and transmit sound vibrations across the middle ear thanks to the particular orientation of its collagen fibers, radiate on one side and circular on the opposite side. Through the combination of advanced scaffolds and autologous cells, tissue engineering (TE) could offer valuable alternatives to autografting in major TM lesions. In this study, a multiscale approach based on electrospinning (ES) and additive manufacturing (AM) was investigated to fabricate scaffolds, based on FDA approved copolymers, resembling the anatomic features and collagen fiber arrangement of the human TM. A single scale TM scaffold was manufactured using a custom-made collector designed to confer a radial macro-arrangement to poly(lactic-co-glycolic acid) electrospun fibers during their deposition. Dual and triple scale scaffolds were fabricated combining conventional ES with AM to produce poly(ethylene oxide terephthalate)/poly(butylene terephthalate) block copolymer scaffolds with anatomic-like architecture. The processing parameters were optimized for each manufacturing method and copolymer. TM scaffolds were cultured in vitro with human mesenchymal stromal cells, which were viable, metabolically active and organized following the anisotropic character of the scaffolds. The highest viability, cell density and protein content were detected in dual and triple scale scaffolds. Our findings showed that these biomimetic micro-patterned substrates enabled cell disposal along architectural directions, thus appearing as promising substrates for developing functional TM replacements via TE.

Boron nitride nanotube-functionalised myoblast/microfibre constructs: a nanotech-assisted tissue-engineered platform for muscle stimulation.

In this communication, we introduce boron nitride nanotube (BNNT)-functionalised muscle cell/microfibre mesh constructs, obtained via tissue engineering, as a three-dimensional (3D) platform to study a wireless stimulation system for electrically responsive cells and tissues. Our stimulation strategy exploits the piezoelectric behaviour of some classes of ceramic nanoparticles, such as BNNTs, able to polarize under mechanical stress, e.g. using low-frequency ultrasound (US). In the microfibre scaffolds, C2C12 myoblasts were able to differentiate into viable myotubes and to internalize BNNTs, also upon US irradiation, so as to obtain a nanotech-assisted 3D in vitro model. We then tested our stimulatory system on 2D and 3D cellular models by investigating the expression of connexin 43 (Cx43), as a molecule involved in cell crosstalk and mechanotransduction, and myosin, as a myogenic differentiation marker. Cx43 gene expression revealed a marked model dependency. In control samples (without US and/or BNNTs), Cx43 was upregulated under 2D culture conditions (10.78 ± 1.05-fold difference). Interactions with BNNTs increased Cx43 expression in 3D samples. Cx43 mRNA dropped in 2D under the 'BNNTs + US' regimen, while it was best enhanced in 3D samples (3.58 ± 1.05 vs 13.74 ± 1.42-fold difference, p = 0.0001). At the protein level, the maximal expressions of Cx43 and myosin were detected in the 3D model. In contrast with the 3D model, in 2D cultures, BNNTs and US exerted a synergistic depletive effect upon myosin synthesis. These findings indicate that model dimensionality and stimulatory regimens can strongly affect the responses of signalling and differentiation molecules, proving the importance of developing proper in vitro platforms for biological modelling.

Interfacing polymeric scaffolds with primary pancreatic ductal adenocarcinoma cells to develop 3D cancer models.

We analyzed the interactions between human primary cells from pancreatic ductal adenocarcinoma (PDAC) and polymeric scaffolds to develop 3D cancer models useful for mimicking the biology of this tumor. Three scaffold types based on two biocompatible polymeric formulations, such as poly(vinyl alcohol)/gelatin (PVA/G) mixture and poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT) copolymer, were obtained via different techniques, namely, emulsion and freeze-drying, compression molding followed by salt leaching, and electrospinning. In this way, primary PDAC cells interfaced with different pore topographies, such as sponge-like pores of different shape and size or nanofiber interspaces. The aim of this study was to investigate the influence played by the scaffold architecture over cancerous cell growth and function. In all scaffolds, primary PDAC cells showed good viability and synthesized tumor-specific metalloproteinases (MMPs) such as MMP-2, and MMP-9. However, only sponge-like pores, obtained via emulsion-based and salt leaching-based techniques allowed for an organized cellular aggregation very similar to the native PDAC morphological structure. Differently, these cell clusters were not observed on PEOT/PBT electrospun scaffolds. MMP-2 and MMP-9, as active enzymes, resulted to be increased in PVA/G and PEOT/PBT sponges, respectively. These findings suggested that spongy scaffolds supported the generation of pancreatic tumor models with enhanced aggressiveness. In conclusion, primary PDAC cells showed diverse behaviors while interacting with different scaffold types that can be potentially exploited to create stage-specific pancreatic cancer models likely to provide new knowledge on the modulation and drug susceptibility of MMPs.

Plasticity of human dental pulp stromal cells with bioengineering platforms: a versatile tool for regenerative medicine.

In recent years, human dental pulp stromal cells (DPSCs) have received growing attention due to their characteristics in common with other mesenchymal stem cells, in addition to the ease with which they can be harvested. In this study, we demonstrated that the isolation of DPSCs from third molar teeth of healthy individuals allowed the recovery of dental mesenchymal stem cells that showed self-renewal and multipotent differentiation capability. DPSCs resulted positive for CD73, CD90, CD105, STRO-1, negative for CD34, CD45, CD14 and were able to differentiate into osteogenic and chondrogenic cells. We also assayed the angiogenic potential of DPSCs, their capillary tube-like formation was assessed using an in vitro angiogenesis assay and the uptake of acetylated low-density lipoprotein was measured as a marker of endothelial function. Based on these results, DPSCs were capable of differentiating into cells with phenotypic and functional features of endothelial cells. Furthermore, this study investigated the growth and differentiation of human DPSCs under a variety of bioengineering platforms, such as low frequency ultrasounds, tissue engineering and nanomaterials. DPSCs showed an enhanced chondrogenic differentiation under ultrasound application. Moreover, DPSCs were tested on different scaffolds, poly(vinyl alcohol)/gelatin (PVA/G) sponges and human plasma clots. We showed that both PVA/G and human plasma clot are suitable scaffolds for adhesion, growth and differentiation of DPSCs toward osteoblastic lineages. Finally, we evaluated the interactions of DPSCs with a novel class of nanomaterials, namely boron nitride nanotubes (BNNTs). From our investigation, DPSCs have appeared as a highly versatile cellular tool to be employed in regenerative medicine.

Processing large-diameter poly(L-lactic acid) microfiber mesh/mesenchymal stromal cell constructs via resin embedding: an efficient histologic method.

In this study, we performed a complete histologic analysis of constructs based on large diameter ( >100 µm) poly-L-lactic acid (PLLA) microfibers obtained via dry-wet spinning and rat Mesenchymal Stromal Cells (rMSCs) differentiated towards the osteogenic lineage, using acrylic resin embedding. In many synthetic polymer-based microfiber meshes, ex post processability of fiber/cell constructs for histologic analysis may face deterring difficulties, leading to an incomplete investigation of the potential of these scaffolds. Indeed, while polymeric nanofiber (fiber diameter = tens of nanometers)/cell constructs can usually be embedded in common histologic media and easily sectioned, preserving the material structure and the antigenic reactivity, histologic analysis of large polymeric microfiber/cell constructs in the literature is really scant. This affects microfiber scaffolds based on FDA-approved and widely used polymers such as PLLA and its copolymers. Indeed, for such constructs, especially those with fiber diameter and fiber interspace much larger than cell size, standard histologic processing is usually inefficient due to inhomogeneous hardness and lack of cohesion between the synthetic and the biological phases under sectioning. In this study, the microfiber/MSC constructs were embedded in acrylic resin and the staining/reaction procedures were calibrated to demonstrate the possibility of successfully employing histologic methods in tissue engineering studies even in such difficult cases. We histologically investigated the main osteogenic markers and extracellular matrix molecules, such as alkaline phosphatase, osteopontin, osteocalcin, TGF-ß1, Runx2, Collagen type I and the presence of amorphous, fibrillar and mineralized matrix. Biochemical tests were employed to confirm our findings. This protocol permitted efficient sectioning of the treated constructs and good penetration of the histologic reagents, thus allowing distribution and expression of almost all the tested molecules to be revealed. Our results demonstrated that it is possible to perform histologic analyses of large-diameter PLLA-based microfiber scaffold/MSC constructs that face the failure of standard histologic procedures.

Boron nitride nanotubes and primary human osteoblasts: in vitro compatibility and biological interactions under low frequency ultrasound stimulation.

In this paper we investigated a novel and non-invasive approach for an endogenous osteoblast stimulation mediated by boron nitride nanotubes (BNNTs). Specifically, following the cellular uptake of the piezoelectric nanotubes, cultures of primary human osteoblasts (hOBs) were irradiated with low frequency ultrasound (US), as a simple method to apply a mechanical input to the cells loaded with BNNTs. This in vitro study was aimed at investigating the main interactions between hOBs and BNNTs and to study the effects of the 'BNNTs + US' stimulatory method on the osteoblastic function and maturation.A non-cytotoxic BNNT concentration to be used in vitro with hOB cultures was established. Moreover, investigation with transmission electron microscopy/electron energy loss spectroscopy (TEM/EELS) confirmed that BNNTs were internalized in membranal vesicles. The panel of investigated osteoblastic markers disclosed that BNNTs were capable of fostering the expression of late-stage bone proteins in vitro, without using any mineralizing culture supplements. In our samples, the maximal osteopontin expression, with the highest osteocalcin and Ca(2+) production, in the presence of mineral matrix with nodular morphology, was observed in the samples treated with BNNTs + US. In this group was also shown a significantly enhanced synthesis of TGF-ß1, a molecule sensitive to electric stimulation in bone. Finally, gene deregulations of the analyzed osteoblastic genes leading to depletive cellular effects were not detected. Due to their piezoelectricity, BNNT-based therapies might disclose advancements in the treatment of bone diseases.

Use of autologous human mesenchymal stromal cell/fibrin clot constructs in upper limb non-unions: long-term assessment.

BACKGROUND: Tissue engineering appears to be an attractive alternative to the traditional approach in the treatment of fracture non-unions. Mesenchymal stromal cells (MSCs) are considered an appealing cell source for clinical intervention. However, ex vivo cell expansion and differentiation towards the osteogenic lineage, together with the design of a suitable scaffold have yet to be optimized. Major concerns exist about the safety of MSC-based therapies, including possible abnormal overgrowth and potential cancer evolution. AIMS: We examined the long-term efficacy and safety of ex vivo expanded bone marrow MSCs, embedded in autologous fibrin clots, for the healing of atrophic pseudarthrosis of the upper limb. Our research work relied on three main issues: use of an entirely autologous context (cells, serum for ex vivo cell culture, scaffold components), reduced ex vivo cell expansion, and short-term MSC osteoinduction before implantation. METHODS AND FINDINGS: Bone marrow MSCs isolated from 8 patients were expanded ex vivo until passage 1 and short-term osteo-differentiated in autologous-based culture conditions. Tissue-engineered constructs designed to embed MSCs in autologous fibrin clots were locally implanted with bone grafts, calibrating their number on the extension of bone damage. Radiographic healing was evaluated with short- and long-term follow-ups (range averages: 6.7 and 76.0 months, respectively). All patients recovered limb function, with no evidence of tissue overgrowth or tumor formation. CONCLUSIONS: Our study indicates that highly autologous treatment can be effective and safe in the long-term healing of bone non-unions. This tissue engineering approach resulted in successful clinical and functional outcomes for all patients.

Growing bone tissue-engineered niches with graded osteogenicity: an in vitro method for biomimetic construct assembly.

The traditional bone tissue-engineering approach exploits mesenchymal stem cells (MSCs) to be seeded once only on three-dimensional (3D) scaffolds, hence, differentiated for a certain period of time and resulting in a homogeneous osteoblast population at the endpoint. However, after achieving terminal osteodifferentiation, cell viability is usually markedly compromised. On the other hand, naturally occurring osteogenesis results from the coexistence of MSC progenies at distinct differentiative stages in the same microenvironment. This diversification also enables long-term viability of the mature tissue. We report an easy and tunable in vitro method to engineer simple osteogenic cell niches in a biomimetic fashion. The niches were grown via periodic reseeding of undifferentiated MSCs on MSC/scaffold constructs, the latter undergoing osteogenic commitment. Time-fractioning of the seeded cell number during differentiation time of the constructs allowed graded osteogenic cell populations to be grown together on the same scaffolds (i.e., not only terminally differentiated osteoblasts). In such cell-dynamic systems, the overall differentiative stage of the constructs could also be tuned by varying the cell density seeded at each inoculation. In this way, we generated two different biomimetic niche models able to host good reservoirs of preosteoblasts and other osteoprogenitors after 21 culture days. At that time, the niche type resulting in 40.8% of immature osteogenic progenies and only 59.2% of mature osteoblasts showed a calcium content comparable to the constructs obtained with the traditional culture method (i.e., 100.03 ± 29.30 vs. 78.51 ± 28.50 pg/cell, respectively; p=not significant), the latter colonized only by fully differentiated osteoblasts showing exhausted viability. This assembly method for tissue-engineered constructs enabled a set of important parameters, such as viability, colonization, and osteogenic yield of the MSCs to be balanced on 3D scaffolds, thus achieving biomimetic in vitro models with graded osteogenicity, which are more complex and reliable than those currently used by tissue engineers.

Effects of barium titanate nanoparticles on proliferation and differentiation of rat mesenchymal stem cells.

Nanomaterials hold great promise in the manipulation and treatments of mesenchymal stem cells, since they allow the modulation of their properties and differentiation. However, systematic studies have to be carried out in order to assess their potential toxicological effects. The present study reports on biocompatibility evaluation of glycol-chitosan coated barium titanate nanoparticles (BTNPs) on rat mesenchymal stem cells (MSCs). BTNPs are a class of ceramic systems which possess interesting features for biological applications thanks to their peculiar dielectric and piezoelectric properties. Viability was evaluated up to 5 days of incubation (concentrations in the range 0-100 µg/ml) both quantitatively and qualitatively with specific assays. Interactions cells/nanoparticles were further investigated with analysis of the cytoskeleton conformation, with SEM and TEM imaging, and with AFM analysis. Finally, differentiation in adipocytes and osteocytes was achieved in the presence of high doses of BTNPs, thus highlighting the safety of these nanostructures towards mesenchymal stem cells.

Histologic characterization of human ear ossicles for the development of tissue-engineered replacements.

HYPOTHESIS: Precise knowledge of the expression and distribution of extracellular matrix (ECM) molecules and osteochondrogenic markers helps target the proper in vitro regeneration of novel ossicular chain (OC) replacements via tissue engineering (TE). BACKGROUND: We performed an extensive histologic analysis of human ear ossicles in healthy adults. A variety of OC prostheses are currently available, but extrusion of synthetic devices still represents an important clinical phenomenon. TE is a novel discipline combining stem cells, bioresorbable biomaterials, and stimulatory factors for the development of new living tissues in vitro, which might offer forefront opportunities to otologic surgery. However, to drive stem cell differentiation correctly, the final tissue target must be accurately known. METHODS: Malleus, incus, and stapes were collected from cadaveric temporal bones. TE PORPs were obtained via osteodifferentiation of human mesenchymal stromal cells on polymeric scaffolds. Histochemical and immunohistochemical analyses were performed to detect ECM molecules and osteochondrogenic markers. RESULTS: Malleus and incus showed the same histologic tissue type, with similar levels of expression and distributions for both ECM molecules and osteochondrogenic markers, whereas the stapes showed self-standing histologic patterns. In TE PORPs, mesenchymal ECM synthesis and early stage development of ossification sites could be observed, highlighting good cellular integration with the scaffold biomaterial. CONCLUSION: Detailed morphologic study of the ossicles provides data related to tissue dynamics involved in their development, defining features of tissue differentiation and maturation. Such findings underpin the future development of biomimetic ossicular replacement, data that can guide tissue-engineered ossiculoplasty.

Transferrin-conjugated boron nitride nanotubes: protein grafting, characterization, and interaction with human endothelial cells.

In this paper we report on a covalent grafting of boron nitride nanotubes with human transferrin. After silanization of the nanotube wall, transferrin was linked to the nanotubes through carbamide binding. The obtained transferrin-conjugated boron nitride nanotubes (tf-BNNTs) resulted stable in aqueous environments and were characterized in terms of scanning electron microscopy, transmission electron microscopy, size distribution analysis and Z-potential measurement. Effective covalent grafting of transferrin was demonstrated by Fourier transform infrared spectroscopy and UV-Vis spectrophotometry. The obtained tf-BNNTs were thereafter tested on human umbilical vein endothelial cells (HUVECs); in particular cellular up-take was investigated by confocal, scanning and transmission electron microscopy, demonstrating the key role of transferrin during the internalization process. Here reported for the first time in the literature, the covalent BNNT functionalization with a targeting ligand represents a fundamental step towards BNNT exploitation as smart and selective nanocarriers in a number of nanomedicine applications.

Pilot in vivo toxicological investigation of boron nitride nanotubes.

Boron nitride nanotubes (BNNTs) have attracted huge attention in many different research fields thanks to their outstanding chemical and physical properties. During recent years, our group has pioneered the use of BNNTs for biomedical applications, first of all assessing their in vitro cytocompatibility on many different cell lines. At this point, in vivo investigations are necessary before proceeding toward realistic developments of the proposed applications. In this communication, we report a pilot toxicological study of BNNTs in rabbits. Animals were injected with a 1 mg/kg BNNT solution and blood tests were performed up to 72 hours after injection. The analyses aimed at evaluating any acute alteration of hematic parameters that could represent evidence of functional impairment in blood, liver, and kidneys. Even if preliminary, the data are highly promising, as they showed no adverse effects on all the evaluated parameters, and therefore suggest the possibility of the realistic application of BNNTs in the biomedical field.

Good manufacturing practices--grade preformed ossicular prostheses from banked bone via computer numerically controlled micromilling.

OBJECTIVES: The aim of this study was the fabrication of ossicular replacement prostheses (ORPs) from decellularized banked cortical bone via computer numerically controlled (CNC) ultraprecision micromilling, in order to obtain preformed clinical-grade tissue products, reproducing shape, size, and details perfectly comparable to those of synthetic devices. METHODS: Banked femoral compact bone was used to fabricate partial and total ORPs via CNC micromilling according to Good Manufacturing Practices procedures. Drawings of ORPs with different shapes and sizes were uploaded to the computer interface, and different surface-finish parameters were tested. The obtained products underwent dimensional, weight, and surface characterizations. A histologic analysis was pursued to compare the bone matrix compactness of the produced ORPs to that of the ear ossicles. RESULTS: Banked-bone ORPs were produced with high dimensional accuracy. Partial ORP weights averaged (+/- SD) 31.2 +/- 0.6 mg, and total ORP weights averaged 69.3 +/- 0.7 mg. The best-finish mode allowed microscale or nanoscale roughness free from machinery textures to be obtained. Finally, the histologic analysis confirmed that the extracellular matrix compactness of the produced ORPs was suitable for ossicular chain replacement. CONCLUSIONS: This study assesses the fabrication feasibility of novel banked-bone ORPs of extremely high dimensional accuracy. Such devices are aimed at combining the most favorable aspects of both synthetic (reproducibility, convenience, and biosafety) and biological replacements (total biocompatibility).