Bioprocess forces and their impact on cell behavior: implications for bone regeneration therapy

Chitosan nanoparticle applications in dentistry: a sustainable biopolymer

The epoch of Nano-biomaterials and their application in the field of medicine and dentistry has been long-lived. The application of nanotechnology is extensively used in diagnosis and treatment aspects of oral diseases. The nanomaterials and its structures are being widely involved in the production of medicines and drugs used for the treatment of oral diseases like periodontitis, oral carcinoma, etc. and helps in maintaining the longevity of oral health. Chitosan is a naturally occurring biopolymer derived from chitin which is seen commonly in arthropods. Chitosan nanoparticles are the latest in the trend of nanoparticles used in dentistry and are becoming the most wanted biopolymer for use toward therapeutic interventions. Literature search has also shown that chitosan nanoparticles have anti-tumor effects. This review highlights the various aspects of chitosan nanoparticles and their implications in dentistry.

Large-Scale Microcarrier Culture of Chinese Perch Brain Cell for Viral Vaccine Production in a Stirred Bioreactor

Mandarin fish (Siniperca chuatsi) is one of the important cultured fish species in China. Infectious spleen and kidney necrosis virus (ISKNV) and Siniperca Chuatsi rhabdovirus (SCRV) have hindered the development of mandarin fish farming industry. Vaccination is the most effective method for control of viral diseases, however viral vaccine production requires the large-scale culture of cells. Herein, a suspension culture system of Chinese perch brain cell (CPB) was developed on Cytodex 1 microcarrier in a stirred bioreactor. Firstly, CPB cells were cultured using Cytodex 1 microcarrier in 125 mL stirring flasks. With the optimum operational parameters, CPB cells grew well, distributed uniformly, and could fully cover the microcarriers. Then, CPB cells were digested with trypsin and expanded step-by-step with different expansion ratios from the 125 mL stirring bottle to a 500 mL stirring bottle, and finally to a 3-L bioreactor. Results showed that with an expansion ratio of 1:3, we achieved a high cell density level (2.25 × 10⁶ cells/mL) with an efficient use of the microcarriers, which also confirmed the data obtained from the 125 mL stirring flask. Moreover, obvious cytopathic effects (CPE) were observed in the suspended CPB cells post-infection with ISKNV and SCRV. This study provided a large-scale culture system of CPB cells for virus vaccine production.

Designing and validation of an automated ex-vivo bioreactor system for long term culture of bone

Several different bioreactors have been developed to study bone biology. Keeping a bone viable for long-term studies is still a challenge. We have developed an ex-vivo bone bioreactor that can keep the ex-vivo live bone viable for more than 4 weeks. Keeping a bone viable for over a month can be used as an alternative model for in-vivo experiments in animals. We hypothesize that the perfusion flow and mechanical load on the bone provide a real-time environment for the bone to survive. Cancellous bones were harvested from the bovine metatarsals and were placed in the dynamic culture with cyclic loading at regular intervals. After a period of week 4, the bone cores were retrieved from the bioreactor and tested for viability using calcein-AM and ethidium homodimer -1 fluorescent dyes and were compared with the cores that were placed in static culture with and without any loads on them and Day 0 bone core that acted as a positive control. The bone blocks were then fixed in 10% formalin, and bone mineral density was evaluated using a DXA scanner before staining them for H&E to study the morphological changes. Results revealed that the bone cultured in the bioreactor was viable as compared to the one in the static culture with and without constant load. Bone cores cultured in our ex-vivo bioreactor system also maintained their morphology and no statistical difference was found in the bone mineral density compared to positive controls and the statistical difference was found when compared with the cores cultured in static culture. This tool can be used to study bone biology for various applications such as bone ingrowth studies, to study the effect of drugs, hormones, or any growth factors, and much more.

Induction of osteogenic differentiation of bone marrow stromal cells on 3D polyester-based scaffolds solely by subphysiological fluidic stimulation in a laminar flow bioreactor

The fatal determination of bone marrow mesenchymal stem/stromal cells (BMSC) is closely associated with mechano-environmental factors in addition to biochemical clues. The aim of this study was to induce osteogenesis in the absence of chemical stimuli using a custom-designed laminar flow bioreactor. BMSC were seeded onto synthetic microporous scaffolds and subjected to the subphysiological level of fluid flow for up to 21 days. During the perfusion, cell proliferation was significantly inhibited. There were also morphological changes, with F-actin polymerisation and upregulation of ROCK1. Notably, in BMSC subjected to flow, mRNA expression of osteogenic markers was significantly upregulated and RUNX2 was localised in the nuclei. Further, under perfusion, there was greater deposition of collagen type 1 and calcium onto the scaffolds. The results confirm that an appropriate level of fluid stimuli preconditions BMSC towards the osteoblastic lineage on 3D scaffolds in the absence of chemical stimulation, which highlights the utility of flow bioreactors in bone tissue engineering.

Stem Cell Based Exosomes: Are They Effective in Disease or Health?

Exosomes are nano-sized vesicles involved in intercellular communication via delivery of molecules including lipids, nucleic acids, proteins, or other cellular components to distant or neighboring sites. Their ability to pass biological barriers, stability in physiological fluids without degradation, and distinctive affinity to target cells make exosomes very remarkable therapeutic vehicles. Virus-based approaches are some of the most widely used gene therapy methods; however, there are many issues need to be clarified such as high immunogenicity. Using of the exosomes procures the functional transfer of their cargo with minimal intervention from the immune system and it has been reported to be secure and well-tolerated. When the regenerative medicine is taken into consideration, stem cell-based approaches have been aimed to utilize but the general efficacy and safety profile of stem cell therapy has still not been enlightened. At this point, stem cell-derived exosomes exhibit a way to procure cell-free regenerative medicine with their unique characteristics. Exosomes are considered as appropriate and highly stable biological nano-vectors taking part in a wide variety of healthy and pathological processes for advanced targeted therapies. However, there are still crucial obstacles to achieve efficient isolation of large amount of specific and pure exosomes. Thus, large-scale exosome production under good manufacturing practice is required. The purpose of this review is to focus on stem cell-based exosomes for gene delivery and to introduce synthetic exosome-mimics as a potential alternative in the field of targeted gene therapies. Further, we aim to highlight the biobanking and large-scale manufacturing methods of exosomes.

Differentiation Potential of Early- and Late-Passage Adipose-Derived Mesenchymal Stem Cells Cultured under Hypoxia and Normoxia

With an increasing focus on the large-scale expansion of mesenchymal stem cells (MSCs) required for clinical applications for the treatment of joint and bone diseases such as osteoarthritis, the optimisation of conditions for in vitro MSC expansion requires careful consideration to maintain native MSC characteristics. Physiological parameters such as oxygen concentration, media constituents, and passage numbers influence the properties of MSCs and may have major impact on their therapeutic potential. Cells grown under hypoxic conditions have been widely documented in clinical use. Culturing MSCs on large scale requires bioreactor culture; however, it is challenging to maintain low oxygen and other physiological parameters over several passages in large bioreactor vessels. The necessity to scale up the production of cells in vitro under normoxia may affect important attributes of MSCs. For these reasons, our study investigated the effects of normoxic and hypoxic culture condition on early- and late-passage adipose-derived MSCs. We examined effect of each condition on the expression of key stem cell marker genes POU5F1, NANOG, and KLF4, as well as differentiation genes RUNX2, COL1A1, SOX9, COL2A1, and PPARG. We found that expression levels of stem cell marker genes and osteogenic and chondrogenic genes were higher in normoxia compared to hypoxia. Furthermore, expression of these genes reduced with passage number, with the exception of PPARG, an adipose differentiation marker, possibly due to the adipose origin of the MSCs. We confirmed by flow cytometry the presence of cell surface markers CD105, CD73, and CD90 and lack of expression of CD45, CD34, CD14, and CD19 across all conditions. Furthermore, in vitro differentiation confirmed that both early- and late-passage adipose-derived MSCs grown in hypoxia or normoxia could differentiate into chondrogenic and osteogenic cell types. Our results demonstrate that the minimal standard criteria to define MSCs as suitable for laboratory-based and preclinical studies can be maintained in early- or late-passage MSCs cultured in hypoxia or normoxia. Therefore, any of these culture conditions could be used when scaling up MSCs in bioreactors for allogeneic clinical applications or tissue engineering for the treatment of joint and bone diseases such as osteoarthritis.

Mesenchymal Stromal Cell-Based Bone Regeneration Therapies: From Cell Transplantation and Tissue Engineering to Therapeutic Secretomes and Extracellular Vesicles

Effective regeneration of bone defects often presents significant challenges, particularly in patients with decreased tissue regeneration capacity due to extensive trauma, disease, and/or advanced age. A number of studies have focused on enhancing bone regeneration by applying mesenchymal stromal cells (MSCs) or MSC-based bone tissue engineering strategies. However, translation of these approaches from basic research findings to clinical use has been hampered by the limited understanding of MSC therapeutic actions and complexities, as well as costs related to the manufacturing, regulatory approval, and clinical use of living cells and engineered tissues. More recently, a shift from the view of MSCs directly contributing to tissue regeneration toward appreciating MSCs as "cell factories" that secrete a variety of bioactive molecules and extracellular vesicles with trophic and immunomodulatory activities has steered research into new MSC-based, "cell-free" therapeutic modalities. The current review recapitulates recent developments, challenges, and future perspectives of these various MSC-based bone tissue engineering and regeneration strategies.

Spiral microfluidic devices for cell separation and sorting in bioprocesses

Inertial microfluidic systems have been arousing interest in medical applications due to their simple and cost-efficient use. However, comparably small sample volumes in the microliter and milliliter ranges have so far prevented efficient applications in continuous bioprocesses. Nevertheless, recent studies suggest that these systems are well suited for cell separation in bioprocesses because of their facile adaptability to various reactor sizes and cell types. This review will discuss potential applications of inertial microfluidic cell separation systems in downstream bioprocesses and depict recent advances in inertial microfluidics for bioprocess intensification. This review thereby focusses on spiral microchannels that separate particles at a moderate Reynolds number in a laminar flow (Re < 2300) according to their size by applying lateral hydrodynamic forces. Spiral microchannels have already been shown to be capable of replacing microfilters, extracting dead cells and debris in perfusion processes, and removing contaminant microalgae species. Recent advances in parallelization made it possible to process media on a liter-scale, which might pave the way toward industrial applications.

Intercellular Crosstalk Via Extracellular Vesicles in Tumor Milieu as Emerging Therapies for Cancer Progression

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Increasing evidence has suggested that extracellular vesicles (EV) mediated bidirectional transfer of functional molecules (such as proteins, different types of RNA, and lipids) between cancer cells and tumor stromal cells (immune cells, endothelial cells, fibroblasts, stem cells) and strongly contributed to the reinforcement of cancer progression. Thus, intercellular EV-mediated signaling in tumor microenvironment (TME) is essential in the modulation of all processes that support and promote tumor development like immune suppression, angiogenesis, invasion and metastasis, and resistance of tumor cells to anticancer treatments.

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Besides EV potential to revolutionize our understanding of the cancer cell-stromal cells crosstalk in TME, their ability to selectively transfer different cargos to recipient cells has created excitement in the field of tumortargeted delivery of specific molecules for anticancer treatments. Therefore, in tight connection with previous findings, this review brought insight into the dual role of EV in modulation of TME. Thus, on one side EV create a favorable phenotype of tumor stromal cells for tumor progression; however, as a future new class of anticancer drug delivery systems EV could re-educate the TME to overcome main supportive processes for malignancy progression.

Scaffolds with a High Surface Area-to-Volume Ratio and Cultured Under Fast Flow Perfusion Result in Optimal O2 Delivery to the Cells in Artificial Bone Tissues

Tissue engineering has the potential for repairing large bone defects, which impose a heavy financial burden on the public health. However, difficulties with O2 delivery to the cells residing in the interior of tissue engineering scaffolds make it challenging to grow artificial tissues of clinically-relevant sizes. This study uses image-based simulation in order to provide insight into how to better optimize the scaffold manufacturing parameters, and the culturing conditions, in order to resolve the O2 bottleneck. To do this, high resolution 3D X-ray images of two common scaffold types (salt leached foam and non-woven fiber mesh) are fed into Lattice Boltzmann Method fluid dynamics and reactive Lagrangian Scalar Tracking mass transfer solvers. The obtained findings indicate that the scaffolds should have maximal surface area-to-solid volume ratios for higher chances of the molecular collisions with the cells. Furthermore, the cell culture media should be flown through the scaffold pores as fast as practically possible (without detaching or killing the cells). Finally, we have provided a parametric sweep that maps how the molecular transport within the scaffolds is affected by variations in rates of O2 consumption by the cells. Ultimately, the results of this study are expected to benefit the computer-assisted design of tissue engineering scaffolds and culturing experiments.

Exosome manufacturing status

Exosomes are secreted by mammalian cells and are widely distributed in cellular systems. They are a medium of information and material transmission. The complexity of exosome nature and function is not thoroughly understood. Nevertheless, they are being confirmed as mediators of intercellular communication and play significant roles in many physiological and pathological processes. Significant obstacles to the efficient and robust isolation of large quantities of pure and specific exosomes still exist. These include a lack of understanding of the relationship between exosome characteristics and function, and a shortage of scalable solutions to separate specific exosomes from other large entities remain. Hence, generic production platforms are desired. While solutions suitable for exosome manufacturing under GMP are available, most have been developed for other purposes.

Extracellular Vesicle-Mediated Immune Regulation of Tissue Remodeling and Angiogenesis After Myocardial Infarction

Myocardial ischemia-related disorders constitute a major health problem, being a leading cause of death in the world. Upon ischemia, tissue remodeling processes come into play, comprising a series of inter-dependent stages, including inflammation, cell proliferation and repair. Neovessel formation during late phases of remodeling provides oxygen supply, together with cellular and soluble components necessary for an efficient myocardial reconstruction. Immune system plays a central role in processes aimed at repairing ischemic myocardium, mainly in inflammatory and angiogenesis phases. In addition to cellular components and soluble mediators as chemokines and cytokines, the immune system acts in a paracrine fashion through small extracellular vesicles (EVs) release. These vesicular structures participate in multiple biological processes, and transmit information through bioactive cargoes from one cell to another. Cell therapy has been employed in an attempt to improve the outcome of these patients, through the promotion of tissue regeneration and angiogenesis. However, clinical trials have shown variable results, which put into question the actual applicability of cell-based therapies. Paracrine factors secreted by engrafted cells partially mediate tissue repair, and this knowledge has led to the hypothesis that small EVs may become a useful tool for cell-free myocardial infarction therapy. Current small EVs engineering strategies allow delivery of specific content to selected cell types, thus revealing the singular properties of these vesicles for myocardial ischemia treatment.

A novel multicolor flow-cytometry application for quantitative detection of receptors on vascular smooth muscle cells

There is a need to develop new techniques for quantitative measurement of receptors expression on particular vasculature cells types. Here, we describe and demonstrate a novel method to measure quantitatively and simultaneously the expression of endothelin B receptor (ETB) on vascular smooth muscle cells (VSMC). We isolated cells from male rat tissues such as: brain pial, brain intraparenchymal and retina vessels. To analyze solid tissues, a single-cell suspension was prepared by a combined mechanic and enzymatic process. The cells were stained with Fixable Viability Dye, followed by fixation, permeabilization and antibodies staining. The expression of ETB receptors on VSMC was measured by flow-cytometry and visualized by fluorescence microscopy. We obtained a high percentage of viable cells 87.6% ± 1.5% pial; 84.6% ± 4.3% parenchymal and 90.6% ± 4% retina after isolation of single cells. We performed a quantitative measurement of ETB receptor expression on VSMC and we identified two subpopulations of VSMC based on their expression of smooth muscle cells marker SM22α. The results obtained from pial vessels are statistically significant (38.4% ± 4% vs 9.8% ± 3.32%) between the two subpopulations of VSMC. The results obtained from intraparenchymal and retina vessels were not statistically significant. By specific gating on two subpopulations, we were able to quantify the expression of ETB receptors. The two subpopulation expressed the same level of ETB receptor (p = 0.45; p = 0.3; p = 0.42) in pial, parenchymal and retina vessels, respectively. We applied our method to the animals after induction of subarachnoid hemorrhage (SAH). There was statistically significant expression of ETB receptor (p = 0.02) on VSMC between sham 61.4% ± 4% and SAH 77.4% ± 4% rats pial vessels. The presented technique is able to quantitatively and selectively measure the level of protein expression on VSMC. The entire technique is optimized for rat tissue; however the protocol can also be adapted for other species.

Optimisation of a murine splenocyte mycobacterial growth inhibition assay using virulent Mycobacterium tuberculosis

In the absence of a validated correlate of protection or robust animal models for human tuberculosis, Mycobacterial growth inhibition assays (MGIAs) aim to assess vaccines ability to inhibit mycobacterial growth in-vitro. We optimised a reproducible murine splenocyte MGIA based on in-vitro infection with virulent Mycobacterium tuberculosis (M.tb) Erdman. We identified splenocyte viability as a problem in state-of-art MGIA protocols, which can be improved by simple changes in culture conditions (viability increase from 21% to 46% at last day of culture). The growth inhibitory potential in mice immunised with either BCG, H56:CAF01 or H56:CAF01 administered side-by-side with BCG was significantly better compared to placebo in all groups (0.3 log10 CFU [±0.2, p = 0.049], 0.5 [±0.2, p = 0.016] and 0.6 [±0.1, p = 0.0007], respectively) corresponding to the levels of in-vivo protection. Unexpectedly the CAF01 adjuvant control group also induced significant growth inhibition of 0.3 log10 CFU (±0.2, p = 0.047). Finally, we explored vaccine-associated T cell effector functions. Despite presence of high levels of vaccine-specific T cells, we found no increase in CD4+ T cell number or cytokine expression profile, nor a difference in cytokine levels in the supernatant after four days culture with or without M.tb. Spontaneous IFN-γ release correlated with growth inhibition levels (p = 0.02), however the cellular source was not found.

Three-dimensional tissues using human pluripotent stem cell spheroids as biofabrication building blocks

A recently emerged approach for tissue engineering is to biofabricate tissues using cellular spheroids as building blocks. Human pluripotent stem cells (hPSCs), including human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), can be cultured to generate large numbers of cells and can presumably be differentiated into all the cell types of the human body in vitro, thus are an ideal cell source for biofabrication. We previously developed a hydrogel-based cell culture system that can economically produce large numbers of hPSC spheroids. With hPSCs and this culture system, there are two potential methods to biofabricate a desired tissue. In Method 1, hPSC spheroids are first utilized to biofabricate an hPSC tissue that is subsequently differentiated into the desired tissue. In Method 2, hPSC spheroids are first converted into tissue spheroids in the hydrogel-based culture system and the tissue spheroids are then utilized to biofabricate the desired tissue. In this paper, we systematically measured the fusion rates of hPSC spheroids without and with differentiation toward cortical and midbrain dopaminergic neurons and found spheroids' fusion rates dropped sharply as differentiation progressed. We found Method 1 was appropriate for biofabricating neural tissues.

An Integrated Miniature Bioprocessing for Personalized Human Induced Pluripotent Stem Cell Expansion and Differentiation into Neural Stem Cells

Human induced pluripotent stem cells (iPSCs) are ideal cell sources for personalized cell therapies since they can be expanded to generate large numbers of cells and differentiated into presumably all the cell types of the human body in vitro. In addition, patient specific iPSC-derived cells induce minimal or no immune response in vivo. However, with current cell culture technologies and bioprocessing, the cost for biomanufacturing clinical-grade patient specific iPSCs and their derivatives are very high and not affordable for majority of patients. In this paper, we explored the use of closed and miniature cell culture device for biomanufacturing patient specific neural stem cells (NSCs) from iPSCs. We demonstrated that, with the assist of a thermoreversible hydrogel scaffold, the bioprocessing including iPSC expansion, iPSC differentiation into NSCs, the subsequent depletion of undifferentiated iPSCs from the NSCs, and concentrating and transporting the purified NSCs to the surgery room, could be integrated and completed within two closed 15 ml conical tubes.

Enhanced Expansion and Sustained Inductive Function of Skin-Derived Precursor Cells in Computer-Controlled Stirred Suspension Bioreactors

Endogenous dermal stem cells (DSCs) reside in the adult hair follicle mesenchyme and can be isolated and grown in vitro as self‐renewing colonies called skin‐derived precursors (SKPs). Following transplantation into skin, SKPs can generate new dermis and reconstitute the dermal papilla and connective tissue sheath, suggesting they could have important therapeutic value for the treatment of skin disease (alopecia) or injury. Controlled cell culture processes must be developed to efficiently and safely generate sufficient stem cell numbers for clinical use. Compared with static culture, stirred‐suspension bioreactors generated fivefold greater expansion of viable SKPs. SKPs from each condition were able to repopulate the dermal stem cell niche within established hair follicles. Both conditions were also capable of inducing de novo hair follicle formation and exhibited bipotency, reconstituting the dermal papilla and connective tissue sheath, although the efficiency was significantly reduced in bioreactor‐expanded SKPs compared with static conditions. We conclude that automated bioreactor processing could be used to efficiently generate large numbers of autologous DSCs while maintaining their inherent regenerative function. Stem Cells Translational Medicine2017;6:434–443

Accelerated Biofluid Filling in Complex Microfluidic Networks by Vacuum-Pressure Accelerated Movement (V-PAM)

Rapid fluid transport and exchange are critical operations involved in many microfluidic applications. However, conventional mechanisms used for driving fluid transport in microfluidics, such as micropumping and high pressure, can be inaccurate and difficult for implementation for integrated microfluidics containing control components and closed compartments. Here, a technology has been developed termed Vacuum-Pressure Accelerated Movement (V-PAM) capable of significantly enhancing biofluid transport in complex microfluidic environments containing dead-end channels and closed chambers. Operation of the V-PAM entails a pressurized fluid loading into microfluidic channels where gas confined inside can rapidly be dissipated through permeation through a thin, gas-permeable membrane sandwiched between microfluidic channels and a network of vacuum channels. Effects of different structural and operational parameters of the V-PAM for promoting fluid filling in microfluidic environments have been studied systematically. This work further demonstrates the applicability of V-PAM for rapid filling of temperature-sensitive hydrogels and unprocessed whole blood into complex irregular microfluidic networks such as microfluidic leaf venation patterns and blood circulatory systems. Together, the V-PAM technology provides a promising generic microfluidic tool for advanced fluid control and transport in integrated microfluidics for different microfluidic diagnosis, organs-on-chips, and biomimetic studies.

Agitation increases expansion of cord blood hematopoietic cells and promotes their differentiation into myeloid lineage

Mechanical stress caused by agitation is one of the factors that can affect hematopoietic stem cell expansion in suspension bioreactors. Therefore, we have investigated the effects of agitation on umbilical cord blood hematopoietic stem cell (UCB-HSC) growth and differentiation. A comparison was made between various agitation rates (20, 40 and 60 rpm) in spinner-flask and cells cultured in glass petri dish as a static culture. Moreover, the fluid dynamic at various agitation rates of spinner-flask was analyzed to determine shear stress. The spinner-flask contained a rotational moving mixer with glass ball and was kept in tissue culture incubator. To reduce consumption of cytokines, UCB-serum was used which widely decreased the costs. Our results determined that, agitation rate at 40 rpm promoted UCB-HSCs expansion and their colony forming potential. Myeloid progenitors were the main type of cells at 40 rpm agitation rate. The results of glucose consumption and lactic acid production were in complete agreement with colony assay and expansion data and indicated the superiority of culture in spinner-flask when agitated at 40 rpm over to other agitation speeds and also static culture. Cell viability and colony count was affected by changing the agitation speed. We assume that changes in cell growth resulted from the effect of shear stress directly on cell viability, and indirectly on signaling pathways that influence the cells to differentiate.

Impact of mechanical stretch on the cell behaviors of bone and surrounding tissues

Mechanical loading is recognized to play an important role in regulating the behaviors of cells in bone and surrounding tissues in vivo. Many in vitro studies have been conducted to determine the effects of mechanical loading on individual cell types of the tissues. In this review, we focus specifically on the use of the Flexercell system as a tool for studying cellular responses to mechanical stretch. We assess the literature describing the impact of mechanical stretch on different cell types from bone, muscle, tendon, ligament, and cartilage, describing individual cell phenotype responses. In addition, we review evidence regarding the mechanotransduction pathways that are activated to potentiate these phenotype responses in different cell populations.

Regeneration of a Compromized Masticatory Unit in a Large Mandibular Defect Caused by a Huge Solitary Bone Cyst: A Case Report and Review of the Regenerative Literature

The reconstructive options for large expansive cystic lesion affecting the jaws are many. The first stage of treatment may involve enucleation or marsupialization of the cyst. Attempted reconstruction of large osseous defects arising from the destruction of local tissue can present formidable challenges. The literature reports the use of bone grafts, free tissue transfer, bone morphogenic protein and reconstruction plates to assist in the healing and rehabilitation process. The management of huge mandibular cysts needs to take into account the preservation of existing intact structures, removal of the pathology and the reconstructive objectives which focus both on aesthetic and functional rehabilitation. The planning and execution of such treatment requires not only the compliance of the patient and family but also their assent as customers with a voice in determining their surgical destiny. The authors would like to report a unique case of a huge solitary bone cyst that had reduced the ramus, angle and part of the body of one side of the mandible to a pencil-thin-like strut of bone. A combination of decompression through marsupialization, serial packing, and the fabrication of a custom made obturator facilitated the regeneration of the myo-osseous components of the masticatory unit of this patient. Serial CT scans showed evidence of concurrent periosteal and endosteal bone formation and, quite elegantly, the regeneration of the first branchial arch components of the right myo-osseous masticatory complex. The microenvironmental factors that may have favored regeneration of these complex structures are discussed.

Thrombogenic potential of transcatheter aortic valve implantation with trivial paravalvular leakage

BACKGROUND

Significant paravalvular leakage after transcatheter aortic valve implantation (TAVI) correlates with increased morbidity and mortality, but adverse consequences of trivial paravalvular leakage have stimulated few investigations. Using a unique method distinctly different from other diagnostic approaches, we previously reported elevated backflow velocities of short duration (transients) in mechanical valve closure. In this study, similar transients were found in a transcatheter valve paravalvular leakage avatar.

METHODS

Paravalvular leakage rate (zero to 58 mL/second) and aortic valve incompetence (volumetric back flow/forward flow; zero to 32%) were made adjustable using a mock transcatheter aortic valve device and tested in quasi-steady and pulsatile flow test systems. Projected dynamic valve area (PDVA) from the back illuminated mock transcatheter aortic valve device was measured and regional backflow velocities were derived by dividing volumetric flow rate by the PDVA over the open and closing valve phase and the total closed valve area derived from backflow leakage.

RESULTS

Aortic incompetence from 1-32% generated negative backflow transients from 8 to 267 meters/second, a range not dissimilar to that measured in mechanical valves with zero paravalvular leakage. Optimal paravalvular leakage was identified; not too small generating high backflow transients, not too large considering volume overload and cardiac energy loss caused by defective valve behavior and fluid motion.

CONCLUSIONS

Thrombogenic potential of transcatheter aortic valves with trivial aortic incompetence and high magnitude regional backflow velocity transients was comparable to mechanical valves. This may have relevance to stroke rate, asymptomatic microembolic episodes and indications for anticoagulation therapy after transcatheter valve insertion.

Quantitative assessment of barriers to the clinical development and adoption of cellular therapies: A pilot study

There has been a large increase in basic science activity in cell therapy and a growing portfolio of cell therapy trials. However, the number of industry products available for widespread clinical use does not match this magnitude of activity. We hypothesize that the paucity of engagement with the clinical community is a key contributor to the lack of commercially successful cell therapy products. To investigate this, we launched a pilot study to survey clinicians from five specialities and to determine what they believe to be the most significant barriers to cellular therapy clinical development and adoption. Our study shows that the main concerns among this group are cost-effectiveness, efficacy, reimbursement, and regulation. Addressing these concerns can best be achieved by ensuring that future clinical trials are conducted to adequately answer the questions of both regulators and the broader clinical community.

The implementation of novel collaborative structures for the identification and resolution of barriers to pluripotent stem cell translation

Increased global connectivity has catalyzed technological development in almost all industries, in part through the facilitation of novel collaborative structures. Notably, open innovation and crowd-sourcing-of expertise and/or funding-has tremendous potential to increase the efficiency with which biomedical ecosystems interact to deliver safe, efficacious and affordable therapies to patients. Consequently, such practices offer tremendous potential in advancing development of cellular therapies. In this vein, the CASMI Translational Stem Cell Consortium (CTSCC) was formed to unite global thought-leaders, producing academically rigorous and commercially practicable solutions to a range of challenges in pluripotent stem cell translation. Critically, the CTSCC research agenda is defined through continuous consultation with its international funding and research partners. Herein, initial findings for all research focus areas are presented to inform global product development strategies, and to stimulate continued industry interaction around biomanufacturing, strategic partnerships, standards, regulation and intellectual property and clinical adoption.

A differential pressure laminar flow reactor supports osteogenic differentiation and extracellular matrix formation from adipose mesenchymal stem cells in a macroporous ceramic scaffold

We present a laminar flow reactor for bone tissue engineering that was developed based on a computational fluid dynamics model. The bioreactor design permits a laminar flow field through its specific internal shape. An integrated bypass system that prevents pressure build-up through bypass openings for pressure release allows for a constant pressure environment during the changing of permeability values that are caused by cellular growth within a porous scaffold. A macroporous ceramic scaffold, composed of zirconium dioxide, was used as a test biomaterial that studies adipose stem cell behavior within a controlled three-dimensional (3D) flow and pressure environment. The topographic structure of the material provided a basis for stem cell proliferation and differentiation toward the osteogenic lineage. Dynamic culture conditions in the bioreactor supported cell viability during long-term culture and induced cell cluster formation and extra-cellular matrix deposition within the porous scaffold, though no complete closure of the pores with new-formed tissue was observed. We postulate that our system is suitable for studying fluid shear stress effects on stem cell proliferation and differentiation toward bone formation in tissue-engineered 3D constructs.

Construction of mesenchymal stem cell-containing collagen gel with a macrochanneled polycaprolactone scaffold and the flow perfusion culturing for bone tissue engineering

A novel bone tissue-engineering construct was developed by using poly(ɛ-caprolactone) (PCL)-macrochanneled scaffolds combined with stem cell-seeded collagen hydrogels and then applying flow perfusion culture. Rat mesenchymal stem cells (MSCs) were loaded into collagen hydrogels, which were then combined with macrochanneled PCL scaffolds. Collagen hydrogels were demonstrated to provide favorable growth environments for MSCs and to foster proliferation. Cell number determination identified retention of substantially fewer (50–60%) cells when they were seeded directly onto macrochanneled PCL than of cells engineered within collagen hydrogels. Additionally, the cells actively proliferated within the combined scaffold for up to 7 days. MSC-loaded collagen–PCL scaffolds were subsequently cultured under flow perfusion to promote proliferation and osteogenic differentiation. Cells proliferated to levels significantly higher in flow perfusion culture than that under static conditions during 21 days. A quantitative polymerase chain reaction (QPCR) assay revealed significant alterations in the transcription of bone-related genes such as osteopontin (OPN), osteocalcin (OCN), and bone sialoprotein (BSP), such as 8-, 2.5-, and 3-fold induction, respectively, after 10 days of flow perfusion relative to those in static culture. OPN and OCN protein levels, as determined by Western blot, increased under flow perfusion. Cellular mineralization was significantly enhanced by the flow perfusion during 21 and 28 days. Analyses of mechanosensitive gene expression induced by flow perfusion shear stress revealed significant upregulation of c-fos and cyclooxygenase-2 (COX-2) during the initial culture period (3–5 days), suggesting that osteogenic stimulation was possible as a result of mechanical force-driven transduction. These results provide valuable information for the design of a new bone tissue-engineering system by combining stem cell-loaded collagen hydrogels with macrochanneled scaffolds in flow perfusion culture.