A Versatile Open-Source Printhead for Low-Cost 3D Microextrusion-Based Bioprinting.

Three-dimensional (3D) bioprinting promises to be essential in tissue engineering for solving the rising demand for organs and tissues. Some bioprinters are commercially available, but their impact on the field of Tissue engineering (TE) is still limited due to their cost or difficulty to tune. Herein, we present a low-cost easy-to-build printhead for microextrusion-based bioprinting (MEBB) that can be installed in many desktop 3D printers to transform them into 3D bioprinters. We can extrude bioinks with precise control of print temperature between 2-60 °C. We validated the versatility of the printhead, by assembling it in three low-cost open-source desktop 3D printers. Multiple units of the printhead can also be easily put together in a single printer carriage for building a multi-material 3D bioprinter. Print resolution was evaluated by creating representative calibration models at different temperatures using natural hydrogels such as gelatin and alginate, and synthetic ones like poloxamer. Using one of the three modified low-cost 3D printers, we successfully printed cell-laden lattice constructs with cell viabilities higher than 90% after 24-h post printing. Controlling temperature and pressure according to the rheological properties of the bioinks was essential in achieving optimal printability and great cell viability. The cost per unit of our device, which can be used with syringes of different volume, is less expensive than any other commercially available product. These data demonstrate an affordable open-source printhead with the potential to become a reliable alternative to commercial bioprinters for any laboratory.

Potential Therapeutic Effects of the Neural Stem Cell-Targeting Antibody Nilo1 in Patient-Derived Glioblastoma Stem Cells.

Glioblastoma (GBM) is the most devastating and least treatable brain tumor with median survival <15 months and extremely high recurrence rates. Promising results of immune checkpoint blockade obtained from pre-clinical studies in mice did not translate to clinic, and new strategies are urgently needed, particularly those targeting GBM stem cells (GSCs) that are held responsible for drug resistance and tumor recurrence. Patient-derived GSC cultures are critical for finding effective brain tumor therapies. Here, we investigated the ability of the recently described monoclonal antibody Nilo1 to specifically recognize GSCs isolated from GBM surgical samples. We employed five patient-derived GSC cultures with different stemness marker expression and differentiation potential, able to recapitulate original tumors when xenotransplanted in vivo. To answer whether Nilo1 has any functional effects in patient-derived GSCs lines, we treated the cells with Nilo1 in vitro and analyzed cell proliferation, cell cycle, apoptosis, sphere formation, as well as the expression of stem vs. differentiation markers. All tested GSCs stained positively for Nilo1, and the ability of Nilo1 to recognize GSCs strongly relied on their stem-like phenotype. Our results showed that a subset of patient-derived GSCs were sensitive to Nilo1 treatment. In three GSC lines Nilo1 triggered differentiation accompanied by the induction of p21. Most strikingly, in one GSC line Nilo1 completely abrogated self-renewal and led to Bax-associated apoptosis. Our data suggest that Nilo1 targets a molecule functionally relevant for stemness maintenance and pinpoint Nilo1 as a novel antibody-based therapeutical strategy to be used either alone or in combination with cytotoxic drugs for GSC targeting. Further pre-clinical studies are needed to validate the effectiveness of GSC-specific Nilo1 targeting in vivo.

Efficient Fabrication of Polycaprolactone Scaffolds for Printing Hybrid Tissue-Engineered Constructs.

Hybrid constructs represent substantial progress in tissue engineering (TE) towards producing implants of a clinically relevant size that recapitulate the structure and multicellular complexity of the native tissue. They are created by interlacing printed scaffolds, sacrificial materials, and cell-laden hydrogels. A suitable biomaterial is a polycaprolactone (PCL); however, due to the higher viscosity of this biopolymer, three-dimensional (3D) printing of PCL is slow, so reducing PCL print times remains a challenge. We investigated parameters, such as nozzle shape and size, carriage speed, and print temperature, to find a tradeoff that speeds up the creation of hybrid constructs of controlled porosity. We performed experiments with conical, cylindrical, and cylindrical shortened nozzles and numerical simulations to infer a more comprehensive understanding of PCL flow rate. We found that conical nozzles are advised as they exhibited the highest shear rate, which increased the flow rate. When working at a low carriage speed, conical nozzles of a small diameter tended to form-flatten filaments and became highly inefficient. However, raising the carriage speed revealed shortcomings because passing specific values created filaments with a heterogeneous diameter. Small nozzles produced scaffolds with thin strands but at long building times. Using large nozzles and a high carriage speed is recommended. Overall, we demonstrated that hybrid constructs with a clinically relevant size could be much more feasible to print when reaching a tradeoff between temperature, nozzle diameter, and speed.

Accurate Calibration in Multi-Material 3D Bioprinting for Tissue Engineering.

Most of the studies in three-dimensional (3D) bioprinting have been traditionally based on printing a single bioink. Addressing the complexity of organ and tissue engineering, however, will require combining multiple building and sacrificial biomaterials and several cells types in a single biofabrication session. This is a significant challenge, and, to tackle that, we must focus on the complex relationships between the printing parameters and the print resolution. In this paper, we study the influence of the main parameters driven multi-material 3D bioprinting and we present a method to calibrate these systems and control the print resolution accurately. Firstly, poloxamer hydrogels were extruded using a desktop 3D printer modified to incorporate four microextrusion-based bioprinting (MEBB) printheads. The printed hydrogels provided us the particular range of printing parameters (mainly printing pressure, deposition speed, and nozzle z-offset) to assure the correct calibration of the multi-material 3D bioprinter. Using the printheads, we demonstrated the excellent performance of the calibrated system extruding different fluorescent bioinks. Representative multi-material structures were printed in both poloxamer and cell-laden gelatin-alginate bioinks in a single session corroborating the capabilities of our system and the calibration method. Cell viability was not significantly affected by any of the changes proposed. We conclude that our proposal has enormous potential to help with advancing in the creation of complex 3D constructs and vascular networks for tissue engineering.

Distinct prostate cancer-related mRNA cargo in extracellular vesicle subsets from prostate cell lines.

BACKGROUND: Multiple types of extracellular vesicles (EVs), including microvesicles (MVs) and exosomes (EXOs), are released by all cells constituting part of the cellular EV secretome. The bioactive cargo of EVs can be shuffled between cells and consists of lipids, metabolites, proteins, and nucleic acids, including multiple RNA species from non-coding RNAs to messenger RNAs (mRNAs). In this study, we hypothesized that the mRNA cargo of EVs could differ based on the EV cellular origin and subpopulation analyzed. METHODS: We isolated MVs and EXOs from PC-3 and LNCaP prostate cancer cells by differential centrifugation and compared them to EVs derived from the benign PNT2 prostate cells. The relative mRNA levels of 84 prostate cancer-related genes were investigated and validated using quantitative reverse transcription PCR arrays. RESULTS: Based on the mRNA abundance, MVs rather than EXOs were enriched in the analyzed transcripts, providing a snapshot of the tumor transcriptome. LNCaP MVs specifically contained significantly increased mRNA levels of NK3 Homeobox 1 (NKX3-1), transmembrane protease serine 2 (TMPRSS2), and tumor protein 53 (TP53) genes, whereas PC-3 MVs carried increased mRNA levels of several genes including, caveolin-2 (CAV2), glutathione S-transferase pi 1 (GSTP1), pescadillo ribosomal biogenesis factor 1 (PES1), calmodulin regulated spectrin associated protein 1 (CAMSAP1), zinc-finger protein 185 (ZNF185), and others compared to PNT2 MVs. Additionally, ETS variant 1 (ETV1) and fatty acid synthase (FASN) mRNAs identified in LNCaP- and PC-3- derived MVs highly correlated with prostate cancer progression. CONCLUSIONS: Our study provides new understandings of the variability of the mRNA cargo of MVs and EXOs from different cell lines despite same cancer origin, which is essential to better understand the the proportion of the cell transcriptome that can be detected within EVs and to evaluate their role in disease diagnosis.

DNA sequences within glioma-derived extracellular vesicles can cross the intact blood-brain barrier and be detected in peripheral blood of patients.

Tumor-cell-secreted extracellular vesicles (EVs) can cross the disrupted blood-brain barrier (BBB) into the bloodstream. However, in certain gliomas, the BBB remains intact, which might limit EVs release. To evaluate the ability of tumor-derived EVs to cross the BBB, we used an orthotopic xenotransplant mouse model of human glioma-cancer stem cells featuring an intact BBB. We demonstrated that all types of tumor cells-derived EVs-apoptotic bodies, shedding microvesicles and exosomes-cross the intact BBB and can be detected in the peripheral blood, which provides a minimally invasive method for their detection compared to liquid biopsies obtained from cerebrospinal fluid (CSF). Furthermore, these EVs can be readily distinguished from total murine EVs, since they carry human-specific DNA sequences relevant for GBM biology. In a small cohort of glioma patients, we finally demonstrated that peripheral blood EVs cargo can be successfully used to detect the presence of IDH1G395A, an essential biomarker in the current management of human glioma.

Cancer stem cells from human glioblastoma resemble but do not mimic original tumors after in vitro passaging in serum-free media.

Human gliomas harbour cancer stem cells (CSCs) that evolve along the course of the disease, forming highly heterogeneous subpopulations within the tumour mass. These cells possess self-renewal properties and appear to contribute to tumour initiation, metastasis and resistance to therapy. CSC cultures isolated from surgical samples are considered the best preclinical in vitro model for primary human gliomas. However, it is not yet well characterized to which extent their biological and functional properties change during in vitro passaging in the serum-free culture conditions. Here, we demonstrate that our CSC-enriched cultures harboured from one to several CSC clones from the human glioma sample. When xenotransplanted into mouse brain, these cells generated tumours that reproduced at least three different dissemination patterns found in original tumours. Along the passages in culture, CSCs displayed increased expression of stem cell markers, different ratios of chromosomal instability events, and a varied response to drug treatment. Our findings highlight the need for better characterization of CSC-enriched cultures in the context of their evolution in vitro, in order to uncover their full potential as preclinical models in the studies aimed at identifying molecular biomarkers and developing new therapeutic approaches of human gliomas.

Human stem cell decorated nanocellulose threads for biomedical applications.

Upon surgery, local inflammatory reactions and postoperative infections cause complications, morbidity, and mortality. Delivery of human adipose mesenchymal stem cells (hASC) into the wounds is an efficient and safe means to reduce inflammation and promote wound healing. However, administration of stem cells by injection often results in low cell retention, and the cells deposit in other organs, reducing the efficiency of the therapy. Thus, it is essential to improve cell delivery to the target area using carriers to which the cells have a high affinity. Moreover, the application of hASC in surgery has typically relied on animal-origin components, which may induce immune reactions or even transmit infections due to pathogens. To solve these issues, we first show that native cellulose nanofibers (nanofibrillated cellulose, NFC) extracted from plants allow preparation of glutaraldehyde cross-linked threads (NFC-X) with high mechanical strength even under the wet cell culture or surgery conditions, characteristically challenging for cellulosic materials. Secondly, using a xenogeneic free protocol for isolation and maintenance of hASC, we demonstrate that cells adhere, migrate and proliferate on the NFC-X, even without surface modifiers. Cross-linked threads were not found to induce toxicity on the cells and, importantly, hASC attached on NFC-X maintained their undifferentiated state and preserved their bioactivity. After intradermal suturing with the hASC decorated NFC-X threads in an ex vivo experiment, cells remained attached to the multifilament sutures without displaying morphological changes or reducing their metabolic activity. Finally, as NFC-X optionally allows facile surface tailoring if needed, we anticipate that stem-cell-decorated NFC-X opens a versatile generic platform as a surgical bionanomaterial for fighting postoperative inflammation and chronic wound healing problems.

Growth of Human Pluripotent Stem Cells Using Functional Human Extracellular Matrix.

The use of animal products in the derivation and maintenance of human pluripotent stem cells (hPSCs) limits their possible applications in research and in clinics. Thus, one of the major goals in regenerative medicine is the establishment of animal-free conditions to support the culture and differentiation of human stem cells. Human fibroblasts produce an extracellular matrix (ECM) which can be extracted without the use of detergents, sterilized, and then used to coat tissue culture plates. We have shown that human embryonic stem cells (hESCs) grown on this matrix maintain their pluripotency in the presence of medium conditioned by fibroblast cells, and that these cells maintain expression of surface proteins (SSEA4, Tra1-60, Tra1-81), alkaline phosphatase activity, and specific intracellular markers (Nanog, Oct-4, Tert, FoxD3) in hESCs. This growth system reduces exposure of hPSCs to feeder layers and animal ingredients, thereby limiting the risk of pathogenic contamination and additionally, facilitating their manipulation. Herein we present an improved version of our previous protocol for extracting ECM from human foreskin fibroblast using a different buffer. Our new hypotonic shock method is detergent-free, reduces costs, and preserves the integrity of the extracted ECM. This improved protocol has been validated for undifferentiated-state hPSC maintenance (more than 40 passages), stem cell differentiation, and for cell migration assays.

Heart valve tissue engineering: how far is the bedside from the bench?

Heart disease, including valve pathologies, is the leading cause of death worldwide. Despite the progress made thanks to improving transplantation techniques, a perfect valve substitute has not yet been developed: once a diseased valve is replaced with current technologies, the newly implanted valve still needs to be changed some time in the future. This situation is particularly dramatic in the case of children and young adults, because of the necessity of valve growth during the patient's life. Our review focuses on the current status of heart valve (HV) therapy and the challenges that must be solved in the development of new approaches based on tissue engineering. Scientists and physicians have proposed tissue-engineered heart valves (TEHVs) as the most promising solution for HV replacement, especially given that they can help to avoid thrombosis, structural deterioration and xenoinfections. Lastly, TEHVs might also serve as a model for studying human valve development and pathologies.

Different gDNA content in the subpopulations of prostate cancer extracellular vesicles: apoptotic bodies, microvesicles, and exosomes.

BACKGROUND: Extracellular vesicles (EVs) are cell-derived membrane vesicles. EVs contain several RNAs such as mRNA, microRNAs, and ncRNAs, but less is known of their genomic DNA (gDNA) content. It is also unknown whether the DNA cargo is randomly sorted or if it is systematically packed into specific EV subpopulations. The aim of this study was to analyze whether different prostate cancer (PCa) cell-derived EV subpopulations (apoptotic bodies, microvesicles, and exosomes) carry different gDNA fragments. METHODS: EV subpopulations were isolated from three PCa cell lines (LNCaP, PC-3, and RC92a/hTERT) and the plasma of PCa patients and healthy donors, and characterized by transmission electron microscopy, nanoparticle tracking analysis and total protein content. gDNA fragments of different genes were detected by real time quantitative PCR and confirmed by DNA sequencing. RESULTS: We report that the concentration of EVs was higher in the cancer patients than in the healthy controls. EV subpopulations differed from each other in terms of total protein and DNA content. Analysis of gDNA fragments of MLH1, PTEN, and TP53 genes from the PCa cell-derived EV subpopulations showed that different EVs carried different gDNA content, which could even harbor specific mutations. Altogether, these results suggest that both nucleic acids and proteins are selectively and cell-dependently packed into the EV subtypes. CONCLUSIONS: EVs derived from PCa cell lines and human plasma samples contain double-stranded gDNA fragments which could be used to detect specific mutations, making EVs potential biomarkers for cancer diagnostics and prognostics.

SOX2+ cell population from normal human brain white matter is able to generate mature oligodendrocytes.

OBJECTIVES: A number of neurodegenerative diseases progress with a loss of myelin, which makes them candidate diseases for the development of cell-replacement therapies based on mobilisation or isolation of the endogenous neural/glial progenitor cells, in vitro expansion, and further implantation. Cells expressing A2B5 or PDGFRA/CNP have been isolated within the pool of glial progenitor cells in the subcortical white matter of the normal adult human brain, all of which demonstrate glial progenitor features. However, the heterogeneity and differentiation potential of this pool of cells is not yet well established. METHODS: We used diffusion tensor images, histopathology, and immunostaining analysis to demonstrate normal cytoarchitecture and the absence of abnormalities in human temporal lobe samples from patients with mesial temporal sclerosis. These samples were used to isolate and enrich glial progenitor cells in vitro, and later to detect such cells in vivo. RESULTS: We have identified a subpopulation of SOX2+ cells, most of them co-localising with OLIG2, in the white matter of the normal adult human brain in vivo. These cells can be isolated and enriched in vitro, where they proliferate and generate immature (O4+) and mature (MBP+) oligodendrocytes and, to a lesser extent, astrocytes (GFAP+). CONCLUSION: Our results demonstrate the existence of a new glial progenitor cell subpopulation that expresses SOX2 in the white matter of the normal adult human brain. These cells might be of use for tissue regeneration procedures.

Hippo pathway effectors control cardiac progenitor cell fate by acting as dynamic sensors of substrate mechanics and nanostructure.

Stem cell responsiveness to extracellular matrix (ECM) composition and mechanical cues has been the subject of a number of investigations so far, yet the molecular mechanisms underlying stem cell mechano-biology still need full clarification. Here we demonstrate that the paralog proteins YAP and TAZ exert a crucial role in adult cardiac progenitor cell mechano-sensing and fate decision. Cardiac progenitors respond to dynamic modifications in substrate rigidity and nanopattern by promptly changing YAP/TAZ intracellular localization. We identify a novel activity of YAP and TAZ in the regulation of tubulogenesis in 3D environments and highlight a role for YAP/TAZ in cardiac progenitor proliferation and differentiation. Furthermore, we show that YAP/TAZ expression is triggered in the heart cells located at the infarct border zone. Our results suggest a fundamental role for the YAP/TAZ axis in the response of resident progenitor cells to the modifications in microenvironment nanostructure and mechanics, thereby contributing to the maintenance of myocardial homeostasis in the adult heart. These proteins are indicated as potential targets to control cardiac progenitor cell fate by materials design.

A xenogeneic-free protocol for isolation and expansion of human adipose stem cells for clinical uses.

Human adipose stem cells (HASCS) play a crucial role in the fields of regenerative medicine and tissue engineering for different reasons: the abundance of adipose tissue, their easy harvesting, the ability to multipotent differentiation and the fact that they do not trigger allogeneic blood response or secrete cytokines that act as immunosuppressants. The vast majority of protocols use animal origin reagents, with the underlying risk of transmitting infections by non-human pathogens. We have designed a protocol to isolate and maintain the properties of hASCs avoiding xenogeneic reagents. These changes not only preserve hASCs morphology, but also increase cell proliferation and maintain their stem cell marker profile. On the other hand, human serum albumin (HSA), Tryple® and human Serum (HS), do not affect hASCs multipotent differentiation ability. The amendments introduced do not trigger modifications in the transcriptional profile of hASCs, alterations in key biochemical pathways or malignization. Thus, we have proven that it is possible to isolate and maintain hASCs avoiding animal reagents and, at the same time, preserving crucial culture parameters during long term culture. Thereby we have revealed a novel and effective tool for the improvement of clinical, cell-based therapies.

Substrate stiffness modulates gene expression and phenotype in neonatal cardiomyocytes in vitro.

Biomaterials to be used as cell delivery systems for cardiac tissue engineering should be able to comply with cardiac muscle contractile activity, while favoring cell survival and neo-angiogenesis in a hostile environment. Biocompatible synthetic materials can be tailored to mimic cardiac tissue three-dimensional organization in the micro- and nanoscales. Nonetheless, they usually display mechanical properties that are far from those of the native myocardium and thus could affect host cell survival and activity. In the present investigation, inert poly-ε-caprolactone planar layers were manufactured to change the surface stiffness (with Young's modulus ranging from 1 to 133 MPa) without changing matrix chemistry. These substrates were challenged with neonatal murine cardiomyocytes to study the possible effect of substrate stiffness on such cell behavior without changing biological cues. Interestingly, softer substrates (0.91±0.08 and 1.53±0.16 MPa) were found to harbor mostly mature cardiomyocytes having assembled sarcomeres, as shown by the expression of alpha actinin and myosin heavy chain in typical striations and the upregulation of sarcomeric actin mRNA. On the other hand, a preferential expression of immature cardiac cell genes (Nkx-2.5) and proteins (GATA-4) in cardiac cells grown onto stiffer materials (49.67±2.56 and 133.23±8.67 MPa) was detected. This result could not be ascribed to significant differences in cell adhesion or proliferation induced by the substrates, but to the stabilization of cardiomyocyte differentiated phenotype induced by softer layers. In fact, cardiac cell electromechanical coupling was shown to be more organized on softer surfaces, as highlighted by connexin 43 distribution. Moreover, a differential regulation of genes involved in extracellular matrix remodeling was detected on soft films (0.91±0.08 MPa) as compared with the stiffest (133.23±8.67 MPa). Finally, the upregulation of a number of genes involved in inflammatory processes was detected when the stiffest polymer is used. These events highlight the differences in cell mechanosensitivity in a heterogeneous cell preparation and are likely to contribute to the differences encountered in cardiac cell phenotype induced by substrate stiffness.

Hypoxia promotes efficient differentiation of human embryonic stem cells to functional endothelium.

Early development of mammalian embryos occurs in an environment of relative hypoxia. Nevertheless, human embryonic stem cells (hESC), which are derived from the inner cell mass of blastocyst, are routinely cultured under the same atmospheric conditions (21% O(2)) as somatic cells. We hypothesized that O(2) levels modulate gene expression and differentiation potential of hESC, and thus, we performed gene profiling of hESC maintained under normoxic or hypoxic (1% or 5% O(2)) conditions. Our analysis revealed that hypoxia downregulates expression of pluripotency markers in hESC but increases significantly the expression of genes associated with angio- and vasculogenesis including vascular endothelial growth factor and angiopoitein-like proteins. Consequently, we were able to efficiently differentiate hESC to functional endothelial cells (EC) by varying O(2) levels; after 24 hours at 5% O(2), more than 50% of cells were CD34+. Transplantation of resulting endothelial-like cells improved both systolic function and fractional shortening in a rodent model of myocardial infarction. Moreover, analysis of the infarcted zone revealed that transplanted EC reduced the area of fibrous scar tissue by 50%. Thus, use of hypoxic conditions to specify the endothelial lineage suggests a novel strategy for cellular therapies aimed at repair of damaged vasculature in pathologies such as cerebral ischemia and myocardial infarction.

Growth of human embryonic stem cells using derivates of human fibroblasts.

The majority of human embryonic stem cell (hESC) lines have been derived and grown using mouse or human feeder cells, or using Matrigel, an animal derivative rich in extracellular matrix (ECM) proteins. However, reliance on feeder layers and animal products limits the manipulation and clinical application of hESC. Alternatively, human fibroblasts produce an ECM which could be employed to coated plates and be easily sterilized. We have shown that hESC grown on this matrix and in the presence of medium conditioned by fibroblast cells maintain markers of pluripotency, including expression of cell surface proteins (SSEA3, SSEA4, TRA-1-60, TRA-1-81), alkaline phosphatase activity, and specific intracellular markers (NANOG, OCT, REX1). Moreover, hESC cultured on this novel human-derived ECM display a normal karyotype. This growth system reduces exposure of hESC to feeder layers and animal ingredients, thereby limiting the risk of pathogenic contamination and additionally facilitating manipulation of hESCs.

Ultrastructure of preimplantation genetic diagnosis-derived human blastocysts grown in a coculture system after vitrification.

OBJECTIVE: To evaluate ultrastructural features of preimplantation genetic diagnosis (PGD) blastocysts before and after vitrification. DESIGN: Descriptive study of both vitrified and fresh hatching blastocysts. SETTING: PGD program at the Instituto Universitario, Instituto Valenciano de Infertilidad. PATIENT(S): Patients undergoing PGD donated their abnormal embryos for research (n = 26). INTERVENTION(S): Biopsied embryos were cultured in the presence of human endometrial cells until day 6. Sixteen blastocysts were vitrified. A total of 11 high-scored hatching blastocysts, 6 warmed and 5 fresh, were fixed for ultrastructure. MAIN OUTCOME MEASURE(S): The cytoskeleton structure, type of intercellular junctions, and basic intracellular organelles in trophoectoderm cells and the inner cell mass were analyzed. RESULT(S): Ten of 16 blastocysts (62%) survived the warming process. Six of these showed no signs of cell degeneration and light microscopy revealed similar ultrastructural characteristics to those of controls. However, in trophoectoderm cells from both fresh and cryopreserved blastocysts, a reduced number of tight junctions and the presence of degradation bodies were detected. CONCLUSION(S): The particular ultrastructural features observed in PGD-derived blastocysts could be related to embryo manipulation and culture conditions. Vitrification does not seem to alter blastocysts, as those that survive hatching do not display detectable cellular alterations when observed through electron microscopy.