A preliminary analysis of volatile metabolites of human induced pluripotent stem cells along the in vitro differentiation

On-Field Test of Tuberculosis Diagnosis through Exhaled Breath Analysis with a Gas Sensor Array

Tuberculosis (TB) is among the more frequent causes of death in many countries. For pulmonary TB, early diagnosis greatly increases the efficiency of therapies. Although highly sensitive tests based on nucleic acid amplification tests (NAATs) and loop-mediated isothermal amplification (TB-LAMP) are available, smear microscopy is still the most widespread diagnostics method in most low-middle-income countries, and the true positive rate of smear microscopy is lower than 65%. Thus, there is a need to increase the performance of low-cost diagnosis. For many years, the use of sensors to analyze the exhaled volatile organic compounds (VOCs) has been proposed as a promising alternative for the diagnosis of several diseases, including tuberculosis. In this paper, the diagnostic properties of an electronic nose (EN) based on sensor technology previously used to identify tuberculosis have been tested on-field in a Cameroon hospital. The EN analyzed the breath of a cohort of subjects including pulmonary TB patients (46), healthy controls (38), and TB suspects (16). Machine learning analysis of the sensor array data allows for the identification of the pulmonary TB group with respect to healthy controls with 88% accuracy, 90.8% sensitivity, 85.7% specificity, and 0.88 AUC. The model trained with TB and healthy controls maintains its performance when it is applied to symptomatic TB suspects with a negative TB-LAMP. These results encourage the investigation of electronic noses as an effective diagnostic method for future inclusion in clinical practice.

Non-Invasive Staging of In Vitro Mice Embryos by Means of Volatolomics

Current methods for embryo selection are limited. This study assessed a novel method for the prediction of embryo developmental potential based on the analysis of volatile organic compounds (VOCs) emitted by embryo samples. The study included mice embryos monitored during the pre-implantation period. Four developmental stages of the embryos were tested, covering the period from 1 to 4 days after fecundation. In each stage, the VOCs released by the embryos were collected and examined by employing two different volatolomic techniques, gas-chromatography coupled to mass-spectrometry (GC-MS) and a nanoarray of chemical gas sensors. The GC-MS study revealed that the VOC patterns emanating from embryo samples had statistically different values at different stages of embryo development. The sensor nanoarray was capable of classifying the developmental stages of the embryos. The proposed volatolomics analysis approach for embryos presents a promising potential for predicting their developmental stage. In combination with conventional morphokinetic parameters, it could be effective as a predictive model for detecting metabolic shifts that affect embryo quality before preimplantation.

Simultaneous Proton Transfer Reaction-Mass Spectrometry and electronic nose study of the volatile compounds released by Plasmodium falciparum infected red blood cells in vitro

The discovery that Volatile Organic Compounds (VOCs) can be biomarkers for several diseases has led to the conception of their possible application as diagnostic tools. In this study, we aimed at defining of diagnostic signatures for the presence of malaria transmissible stages in infected individuals. To do this, we compared VOCs released by asexual and sexual stage cultures of Plasmodium falciparum, the deadliest species of malaria, with those emitted by uninfected red blood cells (RBCs). VOC analysis was carried out with an innovative set-up, where each sample was simultaneously analysed by proton transfer reaction time of flight mass spectrometry (PTR-ToF-MS) and an electronic nose. PTR-Tof-MS results show that sexual stages are characterized by a larger emission of hexanal, compared with uninfected or asexual stage-infected RBCs, which makes them clearly identifiable. PTR-Tof-MS analysis also detected differences in VOC composition between asexual stages and uninfected RBCs. These results have been substantially replicated by the electronic nose analysis and may open the possibility to develop sensitive and easy-to-use devices able to detect sexual parasite stages in infected individuals. This study also demonstrates that the combination of mass spectrometry with electronic noses is a useful tool to identify markers of diseases and to support the development of optimized sensors.

Differences in the Emission of Volatile Organic Compounds (VOCs) between Non-Differentiating and Adipogenically Differentiating Mesenchymal Stromal/Stem Cells from Human Adipose Tissue

Metabolic characterization of human adipose tissue-derived mesenchymal stromal/stem cells (ASCs) is of importance in stem cell research. The monitoring of the cell status often requires cell destruction. An analysis of volatile organic compounds (VOCs) in the headspace above cell cultures might be a noninvasive and nondestructive alternative to in vitro analysis. Furthermore, VOC analyses permit new insight into cellular metabolism due to their view on volatile compounds. Therefore, the aim of our study was to compare VOC profiles in the headspace above nondifferentiating and adipogenically differentiating ASCs. To this end, ASCs were cultivated under nondifferentiating and adipogenically differentiating conditions for up to 21 days. At different time points the headspace samples were preconcentrated by needle trap micro extraction and analyzed by gas chromatography/mass spectrometry. Adipogenic differentiation was assessed at equivalent time points. Altogether the emissions of 11 VOCs showed relevant changes and were analyzed in more detail. A few of these VOCs, among them acetaldehyde, were significantly different in the headspace of adipogenically differentiating ASCs and appeared to be linked to metabolic processes. Furthermore, our data indicate that VOC headspace analysis might be a suitable, noninvasive tool for the metabolic monitoring of (mesenchymal stem) cells in vitro.

Volatile compounds emission from teratogenic human pluripotent stem cells observed during their differentiation in vivo

Several investigations point out that the volatile fraction of metabolites, often called volatilome, might signal the difference processes occurring in living beings, both in vitro and in vivo. These studies have been recently applied to stem cells biology, and preliminary results show that the composition of the volatilome of stem cells in vitro changes along the differentiation processes leading from pluripotency to full differentiation. The identification of pluripotent stem cells is of great importance to improve safety in regenerative medicine avoiding the formation of teratomas. In this paper, we applied gas chromatography and gas sensor array to the study of the volatilome released by mice transplanted with human induced pluripotent stem cells (hiPSCs) or embryoid bodies (EBs) derived from hiPSCs at 5 days and spontaneously differentiated cells at 27 day. Gas chromatography analysis finds that, in mice transplanted with hiPSCs, the abundance of 13 volatile compounds increases four weeks after the implant and immediately before the formation of malignant teratomas (grade 3) become observable. The same behaviour is also followed by the signals of the gas sensors. Besides this event, the gas-chromatograms and the sensors signals do not show any appreciable variation related neither among the groups of transplanted mice nor respect to a placebo population. This is the first in vivo observation of the change of volatile metabolites released by human induced pluripotent stem cells and hiPSCs-derived cells during the differentiation process. These results shed further light on the differentiation mechanisms of stem cells and suggest possible applications for diagnostic purposes for an early detection of tumor relapse after surgery.

Versatile set-up for non-invasive in vitro analysis of headspace VOCs

Volatile organic compound (VOC) profiles emitted in trace concentrations from bacteria or cells has gained increasing importance over the decades. Analysis of VOCs in the headspace does not interfere with in vitro systems and, therefore, offers new options for non-invasive monitoring of cultures. Currently there is not any available standardized in vitro sampling system which considers effects of dilution and contamination onto ppbV to pptV VOC concentrations during. In this study a new in vitro system for online and offline headspace measurement of biological cultures was designed. The system was built from inert materials, equipped with universal sampling ports and easily adjustable volume options. Standard VOC mixtures in the system were analyzed by means of proton-transfer-reaction time-of-flight mass spectrometry and needle-trap-microextraction coupled with gas chromatography/mass spectrometry with a variance of 5%-14% and 10%-15%, respectively. In a proof of concept setup volatile emissions over cell cultures and pure media were assessed. The newly developed system enabled reliable and reproducible headspace analyses of in vitro cultures. As parallel application of different analytical methods is possible and confounding factors could be minimized, this set-up represents an important step towards standardization of headspace analysis over biological cultures.

IL-1β promotes the migration of olfactory epithelium neural stem cells through activating matrix metalloproteinase expressions

BACKGROUND

To investigate the effects of IL-1β on the migration of olfactory epithelium neural stem cells (OENSCs), and to assess the mechanisms.

METHODS

The effects of different concentrations of IL-1β on cell proliferation, apoptosis and migration were evaluated by cell counting assay, flow cytometry and transwell migration assay, respectively. Matrix metalloproteinase (MMP)-2 and MMP-9 expression in both protein and mRNA levels were detected. Small interfering RNA (siRNA) technique was employed to knockdown MMP-2 and MMP-9 expression. Additionally, c-Jun N-terminal kinase (JNK) and nuclear factor-κB (NF-κB) inhibitors were applied to assess the potential signaling pathways involved in the effects of IL-1β on cell migration.

RESULTS

IL-1β promoted cell migration of OENSCs in a concentration-dependent manner at the concentration range of 0-80 ng/ml, but did not affect cell proliferation and apoptosis. Mechanically, IL-1β promoted MMP-2 and MMP-9 expressions. Knockdown of MMP-2 or MMP-9 could significantly reduce IL-1β-induced cell migration. IL-1β activated JNK, NF-κB, Extracellular Signal-Regulated Kinase (ERK) and p-65 phosphorylation. Finally, we evidenced that inhibition of JNK or NF-κB significantly inhibited cell migration.

CONCLUSION

Our study demonstrated that IL-1β promoted the migration of OENSCs through activating MMP expression. Moreover, JNK and NF-κB signaling pathways were involved in the regulation. This study provides important experimental evidence for the application of OENSCs in the transplantation therapy.

Smell of cells: Volatile profiling of stem- and non-stem cell proliferation

Bacterial and cell cultures are known to emit a large number of volatile organic compounds (VOCs). Conventional biochemical methods are often destructive, time-consuming and expensive. In contrast, VOC analysis of headspace over cultures may offer a non-destructive alternative for the monitoring of cell proliferation and metabolism. VOC profiles from cultures of murine pluripotent stem cells and fibroblasts were assessed every 24 h for 3 days. Pure cell media were measured as parallel controls. VOC analysis was highly standardized with respect to time of measurement and phases of cell growth. Cultures were grown in custom-made inert boxes. In order to determine the effects of fresh media supply on VOC emissions, both cell types were cultured with and without daily media exchange. VOCs from headspace were preconcentrated by means of needle trap micro-extraction and analysed by gas chromatography-mass spectrometry (GC-MS). Murine pluripotent stem cells emitted increasing concentrations of thiirane and methyl-methoxy-hydroxy-methyl-amine (MMHA). Substance concentration correlated with cell numbers. Murine fibroblasts did not emit thiirane or MMHA. Concentrations of aldehydes, especially benzaldehyde, were lower in both cell cultures than in pure media samples. Daily media exchange resulted in higher cell numbers, but had no major effects on VOC concentrations emitted from the cells. Investigation and monitoring of volatile substances such as thiirane and MMHA may enhance the understanding of stem cell properties and lead to a destruction-free characterization of pluripotent stem cells.

GC/MS-based Analysis of Volatile Metabolic Profile Along in vitro Differentiation of Human Induced Pluripotent Stem Cells

Human induced pluripotent stem cells (hiPSCs) are a promising tool in cell-based therapies for degenerative diseases. A safe application of hiPSCs in vivo, requires the detection of the presence of residual undifferentiated pluripotent cells that can potentially cause the insurgence of teratomas. Several studies point out that metabolic products may provide an alternative method to identify the different steps of cells differentiation. In particular, the analysis of volatile organic compounds (VOCs) is gaining a growing interest in this context, thanks to its inherent noninvasiveness. Here, a protocol for VOCs analysis from human induced pluripotent stem cells (hiPSCs) is illustrated. It is based on Solid-Phase Microextraction (SPME) technique coupled with gas chromatography-mass spectrometry (GC/MS). The method is applied to measure the volatile metabolite modifications in cells headspace during cell reprogramming from chorionic villus samples (CVS) to hiPSCs, and along hiPSCs in vitro differentiation into early neural progenitors (NPs), passing through embryoid bodies (EBs) formation.