Evaluation of the use of human Mesenchymal Stem Cells for acute toxicity tests

SAEDC: Development of a technological solution for exploratory data analysis and statistics in cytotoxicity

INTRODUCTION

The intergovernmental organizations Organisation for Economic Co-operation and Development (OECD) and Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) have developed guidelines for the use of in vitro models for toxicological evaluation of chemicals. However, the presence of manual steps and the requirement of multiple tools for data analysis, apart from being costly and time-consuming, can inadvertently introduce errors by researchers.

OBJECTIVES

We have developed the SAEDC platform (Technological Solution for Exploratory Data Analysis and Statistics for Cytotoxicity, in Portuguese), which enables analysis of cytotoxicity data from assays following OECD Guideline No. 129.

METHODOLOGY

In vitro experimental data were used to compare with the analysis methodology suggested in the Guideline. We analyzed 117 data sets covering chemicals from Category I to Unclassified according to GHS classification.

RESULTS

The four-parameters of non-linear regression (4PL) calculated by the SAEDC platform showed no significant differences compared to standard methodology in any of the data sets (p > 0.05). The coefficient of determination (R-squared) also demonstrated not only a good fit of the 4PL model to the data but also significant similarity to values obtained by the conventional methodology. Finally, the SAEDC platform predicted LD50 values for the chemicals from IC50, using the Registry of Cytotoxicity (RC) regression models.

CONCLUSION

The comparison with the standard data analysis methodology revealed that SAEDC platform fulfills the requirements for cytotoxicity data analysis, generating reliable and accurate results with fewer steps performed by researchers. The use of SAEDC platform for obtaining toxicity values can reduce analysis time compared to the standard methodology proposed by regulatory agencies. Thus, automation of the analysis using the SAEDC platform has the potential to save time and resources for cytotoxicity researchers and laboratories while generating reliable results.

Comparative Study of Spheroids (3D) and Monolayer Cultures (2D) for the In Vitro Assessment of Cytotoxicity Induced by the Mycotoxins Sterigmatocystin, Ochratoxin A and Patulin

Mycotoxins are secondary metabolites produced by filamentous fungi associated with a variety of acute and chronic foodborne diseases. Current toxicology studies mainly rely on monolayer cell cultures and animal models, which are undeniably affected by several limitations. To bridge the gap between the current in vitro toxicology approach and the in vivo predictability of the data, we here investigated the cytotoxic effects induced by the mycotoxins sterigmatocystin (STE), ochratoxin A (OTA) and patulin (PAT) on different 2D and 3D cell cultures. We focused on human tumours (neuroblastoma SH-SY5Y cells and epithelial breast cancer MDA-MB-213 cells) and healthy cells (bone marrow-derived mesenchymal stem cells, BM-MSC, and umbilical vein endothelial cells, HUVECs). The cytotoxicity of STE, OTA, and PAT was determined after 24, 48 and 72 h of exposure using an ATP assay in both culture models. Three-dimensional spheroids' morphology was also analysed using the MATLAB-based open source software AnaSP 1.4 version. Our results highlight how each cell line and different culture models showed specific sensitivities, reinforcing the importance of using more complex models for toxicology studies and a multiple cell line approach for an improved and more comprehensive risk assessment.

Human Stem Cells for Cardiac Disease Modeling and Preclinical and Clinical Applications-Are We on the Road to Success?

Cardiovascular diseases (CVDs) are pointed out by the World Health Organization (WHO) as the leading cause of death, contributing to a significant and growing global health and economic burden. Despite advancements in clinical approaches, there is a critical need for innovative cardiovascular treatments to improve patient outcomes. Therapies based on adult stem cells (ASCs) and embryonic stem cells (ESCs) have emerged as promising strategies to regenerate damaged cardiac tissue and restore cardiac function. Moreover, the generation of human induced pluripotent stem cells (iPSCs) from somatic cells has opened new avenues for disease modeling, drug discovery, and regenerative medicine applications, with fewer ethical concerns than those associated with ESCs. Herein, we provide a state-of-the-art review on the application of human pluripotent stem cells in CVD research and clinics. We describe the types and sources of stem cells that have been tested in preclinical and clinical trials for the treatment of CVDs as well as the applications of pluripotent stem-cell-derived in vitro systems to mimic disease phenotypes. How human stem-cell-based in vitro systems can overcome the limitations of current toxicological studies is also discussed. Finally, the current state of clinical trials involving stem-cell-based approaches to treat CVDs are presented, and the strengths and weaknesses are critically discussed to assess whether researchers and clinicians are getting closer to success.

Human Stem Cells for Cardiac Disease Modeling and Preclinical and Clinical Applications—Are We on the Road to Success?

Cardiovascular diseases (CVDs) are pointed out by the World Health Organization (WHO) as the leading cause of death, contributing to a significant and growing global health and economic burden. Despite advancements in clinical approaches, there is a critical need for innovative cardiovascular treatments to improve patient outcomes. Therapies based on adult stem cells (ASCs) and embryonic stem cells (ESCs) have emerged as promising strategies to regenerate damaged cardiac tissue and restore cardiac function. Moreover, the generation of human induced pluripotent stem cells (iPSCs) from somatic cells has opened new avenues for disease modeling, drug discovery, and regenerative medicine applications, with fewer ethical concerns than those associated with ESCs. Herein, we provide a state-of-the-art review on the application of human pluripotent stem cells in CVD research and clinics. We describe the types and sources of stem cells that have been tested in preclinical and clinical trials for the treatment of CVDs as well as the applications of pluripotent stem-cell-derived in vitro systems to mimic disease phenotypes. How human stem-cell-based in vitro systems can overcome the limitations of current toxicological studies is also discussed. Finally, the current state of clinical trials involving stem-cell-based approaches to treat CVDs are presented, and the strengths and weaknesses are critically discussed to assess whether researchers and clinicians are getting closer to success.

Cell surface markers for mesenchymal stem cells related to the skeletal system: A scoping review

Multipotent mesenchymal stromal cells (MSCs) have been described as bone marrow stromal cells, which can form cartilage, bone or hematopoietic supportive stroma. In 2006, the International Society for Cell Therapy (ISCT) established a set of minimal characteristics to define MSCs. According to their criteria, these cells must express CD73, CD90 and CD105 surface markers; however, it is now known they do not represent true stemness epitopes. The objective of the present work was to determine the surface markers for human MSCs associated with skeletal tissue reported in the literature (1994-2021). To this end, we performed a scoping review for hMSCs in axial and appendicular skeleton. Our findings determined the most widely used markers were CD105 (82.9%), CD90 (75.0%) and CD73 (52.0%) for studies performed in vitro as proposed by the ISCT, followed by CD44 (42.1%), CD166 (30.9%), CD29 (27.6%), STRO-1 (17.7%), CD146 (15.1%) and CD271 (7.9%) in bone marrow and cartilage. On the other hand, only 4% of the articles evaluated in situ cell surface markers. Even though most studies use the ISCT criteria, most publications in adult tissues don't evaluate the characteristics that establish a stem cell (self-renewal and differentiation), which will be necessary to distinguish between a stem cell and progenitor populations. Collectively, MSCs require further understanding of their characteristics if they are intended for clinical use.

One-Step Colloidal Synthesis of Non-Toxic Electroactive Carbon Dots with a Better Threshold Cytotoxicity and Cytocompatibility

Carbon dots (CDs), because of their characteristic size (<10 nm) and highly fluorescent nature, can be internalized in biological cells or can be tagged to the key components of a living system. While these attributes can be potentially exploited for biomedical applications, the toxicity of CDs remains an important issue to be addressed. Both the synthesis approach and morphological attributes critically determine the dose-dependent toxicity and cytocompatibility of CDs. Against this perspective, we report herein a one-step colloidal synthesis of CDs using different reaction solvents that lead to the formation of three types of CDs (type I, type II, and type III CDs). The cytocompatibility and cellular uptake of CDs in human mesenchymal stem cells (hMSCs) are dependent on the nature of functionalization and concomitantly on the type of precursors. In particular, type I CDs are synthesized using citric acid, hexadecylamine, and octadecene that are immiscible in culture media. The type II CDs synthesized using citric acid and octadecene emit green fluorescence at a 488 nm excitation and were found to be agglomerated when internalized in hMSCs, whereas the type III CDs, synthesized using citric acid and deionized water, exhibit an agglomeration-free behavior. Further, type III CDs show a wide particle distribution, wide emission bandwidth range of 280-700 nm, threshold toxicity of 1 mg/mL, and good cytocompatibility with hMSCs, much better than those in the published reports. When benchmarked against commercial graphene quantum dots, the as-synthesized type III CDs have better electrical conductivity and cytocompatibility at a given dosage. Thus, the electroactive nature of synthesized type III CDs along with their inherent fluorescent property and less cytotoxicity would enable their potential applications in bio-imaging, directional lineage commitment, and cell-based therapy.

First evaluation of the anxiolytic-like effects of a bromazepam‑palladium complex in mice

A significant fraction of patients are affected by persistent fear and anxiety. Currently, there are several anxiolytic drug options, however their clinical outcomes do not fully manage the symptoms. Here, we evaluated the effects of a bromazepam‑palladium derivative [2-{(7-bromo-2-oxo-1,3-dihydro-2H-1,4-benzodiazepin-5-il)pyridinyl-κ²-N,N}chloropalladium(II)], [(BMZ)PdCl₂], on fear/anxiety and memory-related behavior in mice. For this, female Swiss mice were treated intraperitoneally (i.p.) with saline (NaCl 0.9%) or [(BMZ)PdCl₂] (0.5, 5.0, or 50 μg/kg). After 30 min, different tests were performed to evaluate anxiety, locomotion, and memory. We also evaluated the acute toxicity of [(BMZ)PdCl₂] using a cell viability assay (neutral red uptake assay), and whether the drugs mechanism of action involves the γ-aminobutyric acid type A (GABA_A) receptor complex by pre-treating animals with flumazenil (1.0 mg/kg, i.p., a competitive antagonist of GABA_A-binding site). Our results demonstrate that [(BMZ)PdCl₂] induces an anxiolytic-like phenotype in the elevated plus-maze test and that this effect can be blocked by flumazenil. Furthermore, there were no behavioral alterations induced by [(BMZ)PdCl₂], as evaluated in the light-dark box, open field, and step-down passive avoidance tests. In the acute toxicity assay, [(BMZ)PdCl₂] presented IC₅₀ and LD₅₀ values of 218 ± 60 μg/mL and 780 ± 80 mg/kg, respectively, and GSH category 4. Taken together, our results show that the anxiolytic-like effect of acute treatment with [(BMZ)PdCl₂] occurs through the modulation of the benzodiazepine site in the GABA_A receptor complex. Moreover, we show indications that [(BMZ)PdCl₂] does not promote sedation and amnesia and presents the same toxicity as the bromazepam prototype.

Harnessing rat derived model cells to assess the toxicity of TiO2 nanoparticles

Until now, a few studies have been conducted on the destructive effects of TiO₂ NPs in living organisms, and studies on the toxicity of TiO₂ NPs are still in the beginning phases. Because of the widespread use of TiO₂ NPs in all areas of human life, it is essential to study their profound and fundamental toxic effects on each organ and body cell. Herein, we evaluate the effect of exposure to TiO₂ NPs on in vitro models derived from the rat bone marrow and adipose tissues. Exposure to TiO₂ NPs at 100 and 200 μg/ml exhibited cytotoxicity for the rat bone marrow mesenchymal stem cells (rBMSCs) and rat adipose mesenchymal stem cells (rATSC), respectively. Additionally, reduced rBMSCs and rATSCs frequencies in the S phase of the cell cycle. Moreover, TiO₂ NPs enhanced the activity of cellular senescence-associated β-galactosidase in both model cells. Significantly higher relative expression of aging-related genes P53 and NF-kB (p < 0.05) and lower expression levels of anti-aging-related genes Nanog and SIRT1 were found in the treated cells (p < 0.05). Colony-forming and DAPI staining showed the reduction of cell growth and DNA damage in both rBMSCs and rATSCs. Our findings along with other similar findings showed that TiO₂ NPs probably have negative effects on the cell growth, prompt the cells for entry into proliferation stop, DNA damage, and trigger the aging process. Graphical abstract.

Suitability of Human Mesenchymal Stem Cells Derived from Fetal Umbilical Cord (Wharton’s Jelly) as an Alternative In Vitro Model for Acute Drug Toxicity Screening

Preclinical toxicity screening is the first and most crucial test that assesses the safety of new candidate drugs before their consideration for further evaluation in clinical trials. In vitro drug screening using stem cells has lately arisen as a promising alternative to the “gold standard” of animal testing, but their suitability and performance characteristics in toxicological studies have so far not been comprehensively investigated. In this study, we focused on the evaluation of human mesenchymal stem cells isolated from the matrix (Wharton’s jelly) of fetal umbilical cord (WJSCs), which bear enhanced in vitro applicability due to their unique biological characteristics. In order to determine their suitability for drug-related cytotoxicity assessment, we adopted a high-throughput methodology that evaluated their sensitivity to a selected panel of chemicals in different culture environments. Cytotoxicity was measured within 48 h by means of MTS and/or NRU viability assays, and was compared directly (in vitro) or indirectly (in silico) to adult human mesenchymal stem cells and to reference cell lines of human and murine origin. Our data clearly suggest that human WJSCs can serve as a robust in vitro alternative for acute drug toxicity screening by uniquely combining rapid and versatile assay setup with high-throughput analysis, good representation of human toxicology, high reproducibility, and low cost.

Development of 3D Printed Biodegradable Mesh with Antimicrobial Properties for Pelvic Organ Prolapse

To address the increasing demand for safe and effective treatment options for pelvic organ prolapse (POP) due to the worldwide ban of the traditional polypropylene meshes, this study introduced degradable polycaprolactone (PCL)/polyethylene glycol (PEG) composite meshes fabricated with melt-electrowriting (MEW). Two PCL/PEG mesh groups: 90:10 and 75:25 (PCL:PEG, wt%) were fabricated and characterized for their degradation rate and mechanical properties, with PCL meshes used as a control. The PCL/PEG composites showed controllable degradation rates by adjusting the PEG content and produced mechanical properties, such as maximal forces, that were higher than PCL alone. The antibacterial properties of the meshes were elicited by coating them with a commonly used antibiotic: azithromycin. Two dosage levels were used for the coating: 0.5 mg and 1 mg per mesh, and both dosage levels were found to be effective in suppressing the growth of S. aureus bacteria. The biocompatibility of the meshes was assessed using human immortalized adipose derived mesenchymal stem cells (hMSC). In vitro assays were used to assess the cell viability (LIVE/DEAD assay), cell metabolic activity (alamarBlue assay) and cell morphology on the meshes (fluorescent and electron microscopy). The cell attachment was found to decrease with increased PEG content. The freshly drug-coated meshes showed signs of cytotoxicity during the cell study process. However, when pre-released for 14 days in phosphate buffered saline, the initial delay in cell attachment on the drug-coated mesh groups showed full recovery at the 14-day cell culture time point. These results indicated that the PCL/PEG meshes with antibiotics coating will be an effective anti-infectious device when first implanted into the patients, and, after about 2 weeks of drug release, the mesh will be supporting cell attachment and proliferation. These meshes demonstrated a potential effective treatment option for POP that may circumvent the issues related to the traditional polypropylene meshes.

Using inhibition of the adipogenesis of adipose-derived stem cells in vitro for toxicity prediction

In vitro stem cell models are used as alternatives to animal models and are important tools for cytotoxicity studies. Researchers can determine the effects of test substances on human cells by evaluating cell viability and differentiation. Here, we describe an in vitro model to quantify adipogenesis based on the Nile red staining of specific lipid droplets and the emission of basic lipids from human adipose tissue-derived mesenchymal stromal cells (AD-MSCs) in the presence of test substances. This assay allows for the prediction of toxicity based on the inhibition of adipogenesis in vitro in a 96-well format. The differentiation of a progenitor cell into a specialized cell, the adipocyte, is easy to monitor and quantify, making this a simple assay. The fluorescence staining of nuclei and lipid droplets is measured after 14 days of cell differentiation to determine cell number and assess cell differentiation using high-content imaging analysis, thus allowing for the identification of chemicals that impact differentiation. We also describe a protocol to assess adipocyte differentiation by fluorescence intensity using a multiplate reader.•

Researchers can utilize the protocol described here for many purposes to evaluate in vitro adipogenesis.

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With this method, it is possible to reduce the use of animals.

3D printed personalized magnetic micromachines from patient blood-derived biomaterials

While recent wireless micromachines have shown increasing potential for medical use, their potential safety risks concerning biocompatibility need to be mitigated. They are typically constructed from materials that are not intrinsically compatible with physiological environments. Here, we propose a personalized approach by using patient blood–derivable biomaterials as the main construction fabric of wireless medical micromachines to alleviate safety risks from biocompatibility. We demonstrate 3D printed multiresponsive microswimmers and microrollers made from magnetic nanocomposites of blood plasma, serum albumin protein, and platelet lysate. These micromachines respond to time-variant magnetic fields for torque-driven steerable motion and exhibit multiple cycles of pH-responsive two-way shape memory behavior for controlled cargo delivery and release applications. Their proteinaceous fabrics enable enzymatic degradability with proteinases, thereby lowering risks of long-term toxicity. The personalized micromachine fabrication strategy we conceptualize here can affect various future medical robots and devices made of autologous biomaterials to improve biocompatibility and smart functionality.

BiOClBr-coated fabrics with enhanced antimicrobial properties under ambient light

This study demonstrates the fabrication of ambient light enabled antimicrobial functional fabrics by coating flower-like bismuth oxyhalide i.e. BiOCl_0.875Br_0.125, with the use of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) as binders for improved coating robustness and durability. The uniformity of the microparticles was ensured with simultaneous probe sonication during the stages of crystal nucleation and growth. The polymeric binders not only strongly anchor the particle on the fabric, but also serve as an ultra-thin protective layer on the BiOClBr that mitigates bismuth leaching. The efficacy of inhibiting bacteria was investigated over the BiOClBr-coated fabrics i.e. cotton and polyester, and the results showed that the coated fabrics could effectively inhibit both Gram-positive and Gram-negative bacteria, i.e. S. aureus and E. coli. In comparison with fabrics coated with other photocatalytic materials including bismuth oxide (Bi₂O₃) and zinc oxide (ZnO), an exceptionally better antimicrobial efficacy was observed for BiOClBr-coated fabrics. The BiOClBr-coated cotton showed ∼5.0 and ∼6.8 times higher disinfection efficacy towards E. coli compared to that of ZnO and Bi₂O₃-coated cotton with the same particle weight percentage, respectively. Further elucidation of the probable mechanism by BiOClBr-coated fabrics is related to the excess amount of reactive oxygen species (ROS). Overall, BiOClBr has been shown to be a promising material to fabricate cost-effective antimicrobial functional surfaces for both environmental and biomedical applications e.g. protective laboratory and factory clothing.

Dichloroacetate and Pyruvate Metabolism: Pyruvate Dehydrogenase Kinases as Targets Worth Investigating for Effective Therapy of Toxoplasmosis

Toxoplasmosis, a protozoan infection caused by Toxoplasma gondii, is estimated to affect around 2.5 billion people worldwide. Nevertheless, the side effects of drugs combined with the long period of therapy usually result in discontinuation of the treatment. New therapies should be developed by exploring peculiarities of the parasite's metabolic pathways, similarly to what has been well described in cancer cell metabolism. An example is the switch in the metabolism of cancer that blocks the conversion of pyruvate into acetyl coenzyme A in mitochondria. In this context, dichloroacetate (DCA) is an anticancer drug that reverts the tumor proliferation by inhibiting the enzymes responsible for this switch: the pyruvate dehydrogenase kinases (PDKs). DCA has also been used in the treatment of certain symptoms of malaria; however, there is no evidence of how this drug affects apicomplexan species. In this paper, we studied the metabolism of T. gondii and demonstrate that DCA also inhibits T. gondii's in vitro infection with no toxic effects on host cells. DCA caused an increase in the activity of pyruvate dehydrogenase followed by an unbalanced mitochondrial activity. We also observed morphological alterations frequently in mitochondria and in a few apicoplasts, essential organelles for parasite survival. To date, the kinases that potentially regulate the activity of pyruvate metabolism in both organelles have never been described. Here, we confirmed the presence in the genome of two putative kinases (T. gondii PDK [TgPDK] and T. gondii branched-chain α-keto acid dehydrogenase kinase [TgBCKDK]), verified their cellular localization in the mitochondrion, and provided in silico data suggesting that they are potential targets of DCA.IMPORTANCE Currently, the drugs used for toxoplasmosis have severe toxicity to human cells, and the treatment still lacks effective and safer alternatives. The search for novel drug targets is timely. We report here that the treatment of T. gondii with an anticancer drug, dichloroacetate (DCA), was effective in decreasing in vitro infection without toxicity to human cells. It is known that PDK is the main target of DCA in mammals, and this inactivation increases the conversion of pyruvate into acetyl coenzyme A and reverts the proliferation of tumor cells. Moreover, we verified the mitochondrial localization of two kinases that possibly regulate the activity of pyruvate metabolism in T. gondii, which has never been studied. DCA increased pyruvate dehydrogenase (PDH) activity in T. gondii, followed by an unbalanced mitochondrial activity, in a manner similar to what was previously observed in cancer cells. Thus, we propose the conserved kinases as potential regulators of pyruvate metabolism and interesting targets for new therapies.

Native bovine hemoglobin reduces differentiation capacity of mesenchymal stromal cells in vitro

We have tested in vitro effects of hemoglobin from bovine slaughterhouse blood (BHb) on stromal cells of mesodermal origin, with an aim to explore its use as a component of cell culture media. Human peripheral blood mesenchymal stromal cells (PB-MSCs) and three mouse cell lines (ATDC5, MC3T3-E1 and 3T3-L1) were employed to study BHb effects on their growth and migration. The cells multilineage differentiation capacity in the presence of BHb was evaluated after induced differentiation, by histochemical staining and by RT-PCR analysis of the expression of genes specific for chondrogenic, adipogenic and osteogenic lineages. The effects of BHb on the cell proliferation and motility were dependent on both, cell type and BHb concentration (0.1 μM, 1 μM and 10 μM). In the lowest concentration (0.1 µM) BHb showed the least prominent effect on the cell proliferation and migration. In this concentration BHb reduced the differentiation capacity of all tested cells and its effect was dependent of composition of induction medium and the culture period. Obtained data suggest that BHb has the potential to be used as a component of cell culture media through maintaining proliferation and reducing differentiation capacity of mesenchymal stromal cells.

Surface water extracts impair gene profiles and differentiation in human mesenchymal stem cells

Low concentrations of pollutants in surface water challenge the assessment of chronic effects on human health. Human bone mesenchymal stem cells (hBMSCs) were employed as a sensitive and relevant in vitro model to evaluate the potential biological effects caused by mixtures of pollutants in surface water. Organic extracts of surface water collected from Hun River inhibited cell viability in a dose-dependent manner. Surface water extracts at noncytotoxic concentrations induced 533 to 1055 differentially expressed genes (DEGs) in hBMSCs after 48 h of exposure. Total of 370 genes were commonly affected by surface water from different sites and accounted for 35-69% of DEGs impaired by individual sample. Pathways related to human diseases, genetic information processing and organismal systems were enriched based on DEGs. Interleukins (IL1B, IL6 and IL8) were affected and involved in most human diseases related pathways. The significantly downregulation of COL1A1 and the variation of rheumatoid arthritis pathway suggested that surface water potentially inhibited osteogenic differentiation of hBMSCs. Clustering analysis and principle component analysis with DEGs distinguish the surface water from tributary and mainstream. The crossing-species comparison of transcriptomic changes identified 923 and 2715 differentially expressed orthologs in hBMSCs and zebrafish, respectively. After the exposure ceased, the followed osteogenic and adipogenic differentiation in hBMSCs for 14 days were inhibited by the treatment of surface water during undifferentiated period, whereas the non-polar fraction exhibited stronger potency in affecting differentiation than the mid to polar fractions. hBMSCs, combining unsupervised transcriptomic technique and specific endpoints test, are promising in screening the health effects of environmental mixtures in surface water.

The inhibition of adipogenesis via an in vitro assay can reduce animal use by more precisely estimating the starting dose for the acute toxic class method

In the present work, we established an adipogenesis inhibition assay as an adequate and sensitive in vitro model for reducing animal use by estimating the starting dose for the acute toxic class (ATC) method. First, human adipose-derived stem cells (ADSCs) underwent adipogenic differentiation induction for 14 days. Then, by high-content imaging analysis, we determined the percentage and area of cell differentiation that we considered suitable for negative and positive internal control according to the quality control criteria strictly standardized mean difference (SSMD) and robust SSMD. Moreover, we established sodium dodecyl sulfate (SDS) as an external positive control in this assay. To measure reduction in animal use to estimate the starting dose for the ATC method, we evaluated 10 chemicals representing Globally Harmonized System of Classification and Labeling of Chemicals (GHS) toxicity categories 1-5 and unclassified toxicity and determined the dose-response curves for percentage and area of cell differentiation by using the Hill function with an R² ≥ 0.85. The resulting IC₅₀ values were used for LD₅₀ prediction and for estimating the starting dose for the ATC method. Our results indicated that use of the inhibition of adipogenesis assay to estimate the starting dose for the ATC method would decrease animal use for 7 out of 10 tested substances, possibly all substances if we consider the more toxic test substances in GHS categories 1, 2, and 3. We can conclude that the present assay is a suitable alternative to reduce animal testing in the first steps of predicting highly toxic substances. Moreover, this method also presents internal and external controls as differentials, which guarantee the quality of the assay as well as the results. These features are important for suggesting a methodology for regulatory purposes.

Functionalisation of TiO2 nanoparticles with a fluorescent organosilane: A synergy enabling their visualisation in biological cells and an enhanced photocatalytic activity

Nanoparticles, such as TiO₂ particles, have a great potential for biomedical applications due to their ultra-small size and large specific surface area. However, their detection within cells is to date more than challenging. Thus, implementing fluorescence properties to nanoparticles via their controlled functionalisation with an organic chromophore is an original and efficient strategy to enable their visualization. In this work, a silylated coupling agent bearing a luminescent rhodamine B group was synthesised and grafted on the surface of anatase nanoparticles. The successful functionalisation was demonstrated via zeta potential, dynamic light scattering and diffuse reflectance infrared Fourier transform analyses. Remarkably, the obtained luminescent TiO₂ particles showed an improved photocatalytic activity compared to the pristine nanoparticles. Both, as-synthesised and functionalised TiO₂ nanoparticles samples appear to be non-toxic towards malignant and non-malignant cells. Moreover, the detection of the functionalised particles within cultured cells was proven to be easy and efficient via confocal fluorescence microscopy.

2,4-D causes oxidative stress induction and apoptosis in human dental pulp stem cells (hDPSCs)

2,4-Dicholorophenoxy acetic acid (2,4-D) is a worldwide used hormone herbicide. Human dental pulp stem cells (hDPSCs) as a potential source of mesenchymal stem cells provide a confident model system for the assessments of chemicals in vitro. The main objective of this study was to examine the biological effects and damages attributed to 2,4-D on hDPSCs. hDPSCs were isolated from third molar pulp tissues and their mesenchymal identity were evaluated. Then, hDPSCs were treated with increasing concentrations of 2,4-D (0.1 μM-10 mM). Cell viability assay and cumulative cell counting were carried out to address 2,4-D effects on biological parameters of hDPSCs. Cell cycle distribution, ROS level and ALP activity were measured before and after treatment. AO/EB staining and caspase 3/7 activity were investigated to detect the possible mechanisms of cell death. Flow-cytometric immunophenotyping and differentiation data confirmed the mesenchymal identity of cultivated hDPSCs. 2,4-D treatment caused a hormetic response in the viability and growth rate of hDPSCs. G0/G1 cell cycle arrest, enhanced ROS level, and reduced ALP activity were detected in hDPSCs treated with EC50 dose of 2,4-D. AO/EB staining showed a higher percentage of alive cells in lower concentrations of the herbicide. The increment in 2,4-D dose and the number of early and late apoptotic cells were increased. DAPI staining and caspase 3/7 assay validated the induction of apoptosis. 2,4-D concentrations up to 100 μM did not affect hDPSCs viability and proliferation. The intense cellular oxidative stress and apoptosis were observed at higher concentration.

In vitro evaluation of magnetite nanoparticles in human mesenchymal stem cells: comparison of different cytotoxicity assays

This work was aimed at defining the suitable test for evaluating Fe₃O₄ NPs cytotoxicity after short-term exposure in human mesenchymal stem cells (hMSCs) using different viability tests, namely NRU, MTT and TB assays, paralleled by cell morphology analyses for cross checking. MTT and NRU data (culture medium with/without hMSCs plus Fe₃O₄NPs) indicated artificial/false increments in cell viability after Fe₃O₄NPs. These observations did not fit with the morphological analyses showing reduced cell density, loss of monolayer features, and morphological alterations at Fe₃O₄NPs ≥50 μg/ml. Fe₃O₄NPs alone induced a substantial increased absorbance at the wavelength required for MTT and NRU. A significant death (25%) of hMSC at Fe₃O₄NPs ≥10 μg/ml, with a maximum effect (45%) at 300 μg/ml after 24 h, exacerbated after 48 h, was observed when applying TB test. These results paralleled the effects on cell morphology. The optical properties and stability of Fe₃O₄NP suspension (tendency to agglomerate in a specific culture medium) represent factors that limit in vitro result interpretation. These findings suggest the non applicability of the spectrophotometric assays for hMSC culture conditions, while TB is an accurate method for determining cell viability after Fe₃O₄NP exposure in this model. In relation to NPs safety assessment: cell-based assays must be considered on case-by-case basis; selection of relevant cell models is also important for predictive toxicological studies; application of a testing strategy is fundamental for understanding the toxicity pathways driving cellular responses.

In vitro toxicity screening of magnetite nanoparticles by applying mesenchymal stem cells derived from human umbilical cord lining

Despite the growing interest in nanoparticles (NPs), their toxicity has not yet been defined and the development of new strategies and predictive models are required. Human stem cells (SCs) offer a promising and innovative cell-based model. Among SCs, mesenchymal SCs (MSCs) derived from cord lining membrane (CL) may represent a new species-specific tool for establishing efficient platforms for primary screening and toxicity/safety testing of NPs. Superparamagnetic iron oxide NPs, including magnetite (Fe₃ O₄ NPs), have aroused great public health and scientific concerns despite their extensive uses. In this study, CL-MSCs were characterized and applied for in vitro toxicity screening of Fe₃ O₄ NPs. Cytotoxicity, internalization/uptake, differentiation and proliferative capacity were evaluated after exposure to different Fe₃ O₄ NP concentrations. Data were compared with those obtained from bone marrow (BM)-MSCs. We observed, at early passages (P3), that: (1) cytotoxicity occurred at 10 μg/mL in CL-MSCs and 100 μg/mL in BM-MSCs (no differences in toxicity, between CL- and BM-MSCs, were observed at higher dosage, 100-300 μg/mL); (2) cell density decrease and monolayer features loss were affected at ≥50 μg/mL in CL-MSCs only; and (3) NP uptake was concentration-dependent in both MSCs. After 100 μg/mL Fe₃ O₄ NP exposures, the capacity of proliferation was decreased (P5-P9) in CL-MSCs without morphology alteration. Moreover, a progressive decrease of intracellular Fe₃ O₄ NPs was observed over culture time. Antigen surface expression and multilineage differentiation were not influenced. These findings suggest that CL-MSCs could be used as a reliable cell-based model for Fe₃ O₄ NP toxicity screening evaluation and support the use of this approach for improving the confidence degree on the safety of NPs to predict health outcomes.

The variable toxicity of silver ions in cell culture media

The elevated interest in silver ions (Ag⁺) as a broad spectrum antimicrobial for use on medical devices has increased the number and importance of in vitro biocompatibility testing, however little consideration is given to the culture environment in which the assessments are performed. The current investigation assessed the viability of mouse fibroblasts (L929) exposed to different concentrations of Ag⁺ in both Dulbecco's modified Eagle's medium (DMEM) and minimal essential medium Eagle, alpha modification (αMEM). We identified a significant increase in the EC₅₀ of L929 cells exposed to Ag⁺ in αMEM compared to DMEM, which was matched by a corresponding decrease in Ag⁺ availability in αMEM at concentrations ≤400 μM, as detected by inductively coupled plasma mass spectrometry (ICP-MS). The reduced availability was not observed for Ag⁺ > 400 μM, the concentration above which caused in vitro cytotoxicity in L929 cells in αMEM; while linear quantification of Ag⁺ was observed in DMEM. Equilibration of the chloride and glucose components between media did not affect cytotoxicity on primary test cells; mesenchymal stromal cells (MSCs). Overall, our results present evidence of the importance of culture conditions on the in vitro evaluation of silver, with DMEM providing a reliable basal media in which to conduct assessments.

Effect of ZnO Nanoparticles on Human Bone Marrow Mesenchymal Stem Cells: Viability, Morphology, Particles Uptake, Cell Cycle and Metabolites

Despite the growing interest in nanoparticles (NPs), the evaluation of their safety use has to be deeply considered, but standardized procedures for the evaluation of their toxicity have not been defined. In vitro methods are ideal in toxicology research because they can rapidly provide reproducible results while preventing the use of animals. Primary cells are considered a better option as model systems for predicting toxicological behavior, although several cell types do not survive enough in culture and isolated cells can have substantial variability when obtained from different donors. Recently, a new test for acute toxicity based on the use of human bone marrow mesenchymal stem cells (hBMMSCs) has been developed and successfully tested in our laboratory following the ICCVAM (Interagency Coordinating Committee on the Validation of Alternative Methods) guidelines [1]. Along these lines, the aim of this study is to evaluate the acute cytotoxicity of ZnO nanoparticles using the new toxicity test based on hBMMSCs, while comparing their behavior with respect to the toxicity of ZnO micrometer ones. For this reason, we assessed the citotoxicity by performing Neutral Red assay, the cellular uptake by transmission electron microscopy and the effects on hBMMSCs cycle by FACS analysis. Furthermore, we also analyzed by means of GC-MS the polar metabolite profile of hBMMSCs samples treated with ZnO micro- and nanoparticles. Our results show that despite the slight differences in terms of cytotoxicity, nano and microparticles show a very different behavior with respect to their effects on hBMMSCs cycle, metabolite profile and cellular uptake.

Procaspase-activating compound-1 induces apoptosis in Trypanosoma cruzi

Some therapeutics for parasitic, cardiac and neurological diseases activate apoptosis. Therefore, the study of apoptotic proteins in pathogenic organisms is relevant. However, the molecular mechanism of apoptosis in unicellular organisms remain elusive, despite morphological evidence of its occurrence. In Trypanosoma cruzi, the causative agent of Chagas disease, metacaspase 3 (TcMCA3), seems to have a key role in parasite apoptosis. Accordingly, this work provides data concerning TcMCA3 regulation through its interaction with procaspase-activating compound 1 (PAC-1), a procaspase 3 activator. Indeed, PAC-1 reduced T. cruzi epimastigote viability with an IC₅₀ of 14.12 µM and induced loss of mitochondrial potential and exposure of phosphatidylserine, features of the apoptotic process. Notwithstanding, those PAC-1-inducible effects were not conserved in metacyclic trypomastigotes. Moreover, PAC-1 reduced the viability of mammalian cells with a greater IC₅₀ (25.70 µM) compared to T. cruzi epimastigotes, indicating distinct modes of binding between caspases and metacaspases. To shed light on the selectivity of metacaspases and caspases, we determined the structural features related to the PAC-1 binding sites in both types of proteins. These data are important for improving the understanding of the apoptosis pathway in T. cruzi so that TcMCA3 could be better targeted with future pharmaceuticals.

Dose-dependent cytotoxicity of bismuth nanoparticles produced by LASiS in a reference mammalian cell line BALB/c 3T3

Nanoparticles (NPs) have emerged as new potential tools for many applications in previous years. Among all types of NPs, bismuth NPs (BiNPs) have a very low cost and potential for many applications, ranging from medicine to industry. Although the toxic effects of bismuth have been studied, little is known about its toxicity at the nanoscale level. Therefore, in this study, we aimed to investigate the cytotoxic effects of BiNPs produced by laser ablation synthesis in solution (LASiS) in a reference mammalian cell line to evaluate their cytotoxicity (BALB/c 3 T3 cells). We also stabilized BiNPs in two different solutions: culture medium supplemented with fetal bovine serum (FBS) and bovine serum albumin (BSA). The cytotoxicity of BiNPs in culture medium (IC₅₀:28.51 ± 9.96 μg/ml) and in BSA (IC₅₀:25.54 ± 8.37 μg/ml) was assessed, and they were not significantly different. Second, the LD₅₀ was predicted, and BiNPs were estimated as GHS class 4. We also found that cell death occurs due to apoptosis. By evaluating the interaction between BiNPs and cells at ultrastructural level, we suggest that cell death occurs once BiNPs are internalized. Additionally, we suggest that BiNPs cause cell damage because myelin figures were found inside cells that had internalized BiNPs. To date, this is the first study to assess the cytotoxicity of BiNPs produced by LASiS and to predict the possible LD₅₀ and GHS class of BiNPs.

Effects of the novel polyphenol conjugate DPP-23 on head and neck squamous cell carcinoma cells in vitro

Despite partial advances in therapy for patients suffering from head and neck squamous cell carcinomas (HNSCC), prognosis still remains poor with minimal improvement in survival for over the last several decades. Some agents found are known to cause cancer cell death in vitro by promoting cellular reactive oxygen species (ROS) accumulation. This is particularly of interest as some cancer cells are more sensitive to ROS than normal cells. It could be shown that the novel polyphenol conjugate (E)-3-(3',5'-Dimethoxyphenyl)-1-(2'-methoxyphenyl)prop-2-en-1-one (DPP-23) offers antitumor effects by the selective generation of ROS without an indication of toxicity in normal tissues in vitro and in vivo. In order to further evaluate the role of DPP-23 as a potential agent in head and neck oncology, the present study investigated its cytotoxic effects on well-established HNSCC cell lines such as HLaC 78 and FaDu, as well as primary human bone marrow stem cells (hBMSCs) and human peripheral blood lymphocytes in vitro. As DPP-23 is not commercially available, it was synthesized via a 'cold' procedure of the Claisen-Schmidt condensation. Following cell treatment with DPP-23 for 24 h, viability and apoptosis were measured via a MTT assay and the Annexin V-propidium iodide test. The results suggest a dose-dependent cytotoxicity in the tested HNSCC tumor cell lines, as well as in hBMSC and lymphocytes. In contrast to previous findings, these preliminary results indicate that the cytotoxic effects of DPP-23 in benign cells may be notably greater than previously suspected. This may indicate a limitation for in the feasibility, or at least of the systemic application, of DPP-23 for patients with HNSCC.

Omics-Based Platform for Studying Chemical Toxicity Using Stem Cells

The new strategy for chemical toxicity testing and modeling is to use in vitro human cell-based assays in conjunction with quantitative high-throughput screening (qHTS) technology, to identify molecular mechanisms and predict in vivo responses. Stem cells are more physiologically relevant than immortalized cell lines because of their unique proliferation and differentiation potentials. We established a robust two stem cells-two lineages assay system, encompassing human mesenchymal stem cells (hMSCs) along osteogenesis and human induced pluripotent stem cells (hiPSCs) along hepatogenesis. We performed qHTS phenotypic screening of LOPAC1280 and identified 38 preliminary hits for hMSCs. This was followed by validation of a selected number of hits and determination of their IC50 values and mechanistic studies of idarubicin and cantharidin treatments using proteomics and bioinformatics. In general, hiPSCs were more sensitive than hMSCs to chemicals, and differentiated progenies were less sensitive than their progenitors. We showed that chemical toxicity depends on both stem cell types and their differentiation stages. Proteomics identified and quantified over 3000 proteins for both stem cells. Bioinformatics identified apoptosis and G2/M as the top pathways conferring idarubicin toxicity. Our Omics-based assays of stem cells provide mechanistic insights into chemical toxicity and may help prioritize chemicals for in-depth toxicological evaluations.

Harvesting multipotent progenitor cells from a small sample of tonsillar biopsy for clinical applications

Background

Human adult stem cells hold the potential for the cure of numerous conditions and degenerative diseases. They possess major advantages over pluripotent stem cells as they can be derived from donors at any age, and therefore pose no ethical concerns or risk of teratoma tumor formation in vivo. Furthermore, they have a natural ability to differentiate and secrete factors that promote tissue healing without genetic manipulation. However, at present, clinical applications of adult stem cells are limited by a shortage of a reliable, standardized, and easily accessible tissue source which does not rely on specimens discarded from unrelated surgical procedures.

Method

Human tonsil-derived mesenchymal progenitor cells (MPCs) were isolated from a small sample of tonsillar tissue (average 0.88 cm³). Our novel procedure poses a minimal mechanical and enzymatic insult to the tissue, and therefore leads to high cell viability and yield. We characterized these MPCs and demonstrated robust multipotency in vitro. We further show that these cells can be propagated and maintained in xeno-free conditions.

Results

We have generated tonsillar biopsy-derived MPC (T-MPC) lines from multiple donors across a spectrum of age, sex, and race, and successfully expanded them in culture. We characterized them by cell surface markers, as well as in vitro expansion and differentiation potential. Our procedure provides a robust yield of tonsillar biopsy-derived T-MPCs.

Conclusions

Millions of MPCs can be harvested from a sample smaller than 1 g, which can be collected from a fully awake donor in an outpatient setting without the need for general anesthesia or hospitalization. Our study identifies tonsillar biopsy as an abundant source of adult MPCs for regenerative medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0619-x) contains supplementary material, which is available to authorized users.

In vitro assessment of deferoxamine on mesenchymal stromal cells from tumor and bone marrow

Deferoxamine (DFO), an iron chelator, is commonly used to remove excess iron from the body. DFO has also been demonstrated to have anti-tumor effect. However, there is no available report on the effect of deferoxamine on mesenchymal stromal cells (MSCs). In this study, we first isolated tumor-associated MSCs (TAMSCs) from EG-7 tumors, which were positive for CD29, CD44, CD73, CD90 and CD105. Ex vivo cultured stem cells derived from tumor and bone marrow compartment were exposed to DFO. We demonstrated that DFO had growth-arresting and apoptosis-inducing effect on TAMSCs and bone marrow MSCs (BMMSCs). DFO also influenced the expression pattern of adhesion molecule VCAM-1 on both TAMSCs and BMMSCs. Notwithstanding its widespread use, our results here warrants caution in the application of DFO, and also highlights the need for careful evaluation of the bone marrow compartment in patients receiving DFO treatment.

Stem cell toxicology: a powerful tool to assess pollution effects on human health

Environmental pollution is a global problem; the lack of comprehensive toxicological assessments may lead to increased health risks. To fully understand the health effects of pollution, it is paramount to implement fast, efficient and specific toxicity screening that relies on human models rather than on time-consuming, expensive and often inaccurate tests involving live animals. Human stem cell toxicology represents a valid alternative to traditional toxicity assays because it takes advantage of the ability of stem cells to differentiate into multiple cell types and tissues of the human body. Thus, this branch of toxicology provides a possibility to assess cellular, embryonic, developmental, reproductive and functional toxicity in vitro within a single system highly relevant to human physiology. In this review, we describe the development, performance and future perspectives of stem cell toxicology, with an emphasis on how it can meet the increasing challenges posed by environmental pollution in the modern world.

Fe3 O4 nanoparticle redox system modulation via cell-cycle progression and gene expression in human mesenchymal stem cells

The use of engineered nanoparticles (NPs) across multiple fields and applications has rapidly increased over the last decade owing to their unusual properties. However, there is an increased need in understanding their toxicological effect on human health. Particularly, iron oxide (Fe3 O4 ) have been used in various sectors, including biomedical, food, and agriculture, but the current understanding of their impact on human health is inadequate. In this investigation, we assessed the toxic effect of Fe3 O4 NPs on human mesenchymal stem cells (hMSCs) adopting cell viability, cellular morphological changes, mitochondrial transmembrane potential, and cell-cycle progression assessment methodologies. Furthermore, the expression of oxidative stress, cell death, and cell-cycle regulatory genes was assessed using quantitative polymerase chain reaction. The Fe3 O4 NPs induced cytotoxicity and nuclear morphological changes in hMSCs by dose and time exposure. Cell-cycle analysis indicated that Fe3 O4 NPs altered the cell-cycle progression through a decrease in the proportion of cells in the G0 -G1 phase. The hMSC mitochondrial membrane potential loss increased with an increase in the concentration of Fe3 O4 NPs exposure. The observed expression levels of the CYP1A, TNF3, TNFSF10, E2F1, and CCNC genes were significantly upregulated in hMSCs in response to Fe3 O4 NPs exposure. Our findings suggest that Fe3 O4 NPs caused metabolic stress through altered cell cycle, oxidative stress, and cell death regulatory gene expression in hMSCs. The results of this investigation revealed that Fe3 O4 NPs exhibited moderate toxicity on hMSCs and that Fe3 O4 NPs may have biomedical applications at low concentrations. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 901-912, 2016.

2,5-hexanedione induced apoptosis of rat bone marrow mesenchymal stem cells by reactive oxygen species

Objectives:

n-Hexane, a common industrial organic solvent, causes multiple organ damage, especially neurotoxicity, which is proved to be caused by its metabolite 2,5-hexanedione (2,5-HD). We previously showed that 2,5-HD induced apoptosis of rat bone marrow mesenchymal stem cells (BMSCs). In the current study, we explored the mechanism of 2,5-HD-induced apoptosis, especially the role played by reactive oxygen species (ROS).

Methods:

Intracellular ROS levels after 2,5-HD treatment were measured by the dichloro-dihydro-fluorescein diacetate (DCFH-DA) method, and the antioxidant N-acetyl cysteine (NAC) was used to scavenge ROS. Apoptosis, mitochondrial membrane potential (MMP), and caspase-3 activity were measured after 2,5-HD exposure with or without NAC pretreatment.

Results:

In rat BMSCs, 20 mM 2,5-HD significantly increased ROS levels and apoptosis. In addition, MMP activity was decreased and caspase-3 activity was increased. With NAC pretreatment, ROS increases were prevented, cells were rescued from apoptosis, and both MMP and caspase-3 activity returned to normal levels. Western blotting analysis of malondialdehyde-modified proteins and superoxide dismutase (SOD) 1 showed that after 2,5-HD exposure, BMSCs had oxidative damage and abnormal SOD1 expression. These returned to normal when cells were pretreated with NAC in addition to 20 mM 2,5-HD. Furthermore, the expressions of NF-κB p65/RelA and phospho-NF-κB p65/RelA (Ser536) were suppressed after 2,5-HD exposure and restored by NAC pretreatment.

Conclusions:

2,5-HD-induced apoptosis in rat BMSCs is potentially mediated by excessive ROS production.

Carbon nanoparticle induced cytotoxicity in human mesenchymal stem cells through upregulation of TNF3, NFKBIA and BCL2L1 genes

Carbon based nanomaterials, including carbon nanotubes, graphene, nanodiamond and carbon nanoparticles, have emerged as potential candidates for a wide variety of applications because of their unusual electrical, mechanical, thermal and optical properties. However, our understanding of how increased usage of carbon based nanomaterials could lead to harmful effects in humans and other biological systems is inadequate. Our present investigation is focused on the cellular toxicity of carbon nanoparticles (CNPs) on human mesenchymal stem cells (hMSCs). Following exposure to CNPs, cell viability, nuclear morphological changes, apoptosis and cell cycle progression were monitored. Furthermore, the expression of genes involved in both cell death (e.g., P53, TNF3, CDKN1A, TNFRSF1A, TNFSF10, NFKBIA, BCL2L1) and cell cycle regulation (e.g., PCNA, EGR1, E2F1, CCNG1, CCND1, CCNC, CYCD3) were assessed using qPCR. Our results indicated that CNPs reduce cell viability and cause chromatin condensation and DNA fragmentation. Cell cycle analysis indicated that CNPs affect the cell cycle progression. However, the gene expression measurements confirmed that CNPs significantly upregulated the P53, TNF3, CDKNIA, and NFKBIA genes and downregulated the EGR1 gene in hMSCs. Our findings suggest that CNPs reduce cell viability by disrupting the expression of cell death genes in human mesenchymal stem cell (hMSC). The results of this investigation revealed that CNPs exhibited moderate toxicity on hMSCs.

Effect of Metformin on Viability, Morphology, and Ultrastructure of Mouse Bone Marrow-Derived Multipotent Mesenchymal Stromal Cells and Balb/3T3 Embryonic Fibroblast Cell Line

Metformin, a popular drug used to treat diabetes, has recently gained attention as a potentially useful therapeutic agent for treating cancer. In our research metformin was added to in vitro cultures of bone marrow-derived multipotent mesenchymal stromal cells (BMSCs) and Balb/3T3 fibroblast at concentration of 1 mM, 5 mM, and 10 mM. Obtained results indicated that metformin negatively affected proliferation activity of investigated cells. The drug triggered the formation of autophagosomes and apoptotic bodies in all tested cultures. Additionally, we focused on determination of expression of genes involved in insulin-like growth factor 2 (IGF2) signaling pathway. The most striking finding was that the mRNA level of IGF2 was constant in both BMSCs and Balb/3T3. Further, the analysis of IGF2 concentration in cell supernatants showed that it decreased in BMSC cultures after 5 and 10 mM metformin treatments. In case of Balb/3T3 the concentration of IGF2 in culture supernatants decreased after 1 and 5 mM and increased after 10 mM of metformin. Our results suggest that metformin influences the cytophysiology of somatic cells in a dose- and time-dependent manner causing inhibition of proliferation and abnormalities of their morphology and ultrastructure.

2,5-hexanedione induced apoptosis in mesenchymal stem cells from rat bone marrow via mitochondria-dependent caspase-3 pathway

2,5-hexanedione (HD) induces apoptosis of nerve cells. However,the mechanism of HD-induced apoptosis remains unknown. Mesenchymal stem cells (MSCs) are multipotential stem cells with the ability to differentiate into various cell types. This study is designed to investigate the apoptosis induced by HD in rat bone marrow MSCs (BMSCs) and the related underlying mechanisms. The fifth generation of MSCs was treated with 0, 10, 20 and 40 mM HD respectively. The viability of BMSCs was observed by MTT. Apoptosis were estimated by Hoechst 33342 staining and TUNEL assay. The disruption of mitochondrial transmembrane potential (MMP) was examined by JC-1 staining. Moreover, the expression of Bax and Bcl-2, cytochrome c release, and caspase-3 activity were determined by real-time RT-PCR, Western blot and Spectrophotometry. Our results showed that HD induced apoptosis in MSCs in a dose dependent manner. Moreover, HD downregulated the Bcl-2 expression,upregulated the Bax expression and the Bax/Bcl-2 ratio, promoted the disruption of MMP, induced the release of cytochrome c from mitochondria to cytosol, and increased the activity of caspase-3 in MSCs. These results indicate that HD induces apoptosis in MSCs and the activated mitochondria-dependent caspase-3 pathway may be involved in the HD-induced apoptosis.

Silica nanoparticles induced metabolic stress through EGR1, CCND, and E2F1 genes in human mesenchymal stem cells

The SiO2 synthesized in bulk form, adopting the conventional methods for application in food industry applications, may also contain nano-sized particles. On account of the unique physico-chemical properties, the SiO2 particulates, such as size and shape, cause metabolic toxicity in cells. Poor understanding of the molecular level nanotoxicity resulting from high-volume synthetic SiO2 exposures in humans is a serious issue, since these particles may also contribute to metabolic stress-mediated chronic diseases. In the present study, we examined the structural characteristics of these nano-sized silica particles adopting SEM and dynamic light scattering (DLS) and assessed the alterations in the cell cycle induced by these silica particles in human mesenchymal stem cells (hMSCs) adopting 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay, morphological changes in the cells adopting fluorescent microscopy, cell cycle analysis adopting flow cytometry, and the expression of genes linked to cell cycle (i.e., proliferating cell nuclear antigen (PCNA), early growth response protein (EGR1), E2F transcription factor (E2F1), cyclin D1, cyclin C, and cyclin D3) adopting qPCR. The SEM and DLS studies indicated that the commercial grade SiO2-NPs were in the nano-scale range. Alterations in the cytoplasmic organization, nuclear morphology, cell cycle progression, and expression of genes linked to cell cycle-dependent metabolic stress through EGR1, CCND, and E2F1 genes were the primary indicators of metabolic stress. Overall, the results of this study demonstrate that synthetic SiO2 acutely affects hMSC through cell cycle-dependent oxidative stress gene network. The toxicity mechanisms (both acute and chronic) of food grade silica should be investigated in greater depth with special reference to food safety.

An in vitro evaluation of the cytotoxicity of varying concentrations of sodium hypochlorite on human mesenchymal stem cells

AIM

To evaluate and compare the cytotoxicity of various concentrations of sodium hypochlorite on immortalized human bone marrow mesenchymal stem cells (MSCs).

MATERIALS AND METHODS

The 5.25 percent sodium hypochlo-rite (NaOCl) at concentrations of 0.5, 0.1, 0.025, 0.0125, and 0.005 mg/ml were used to assess the cytotoxic effect on MSCs. Immortalized human bone marrow mesenchymal stem cells (hTERT-MSCs) were exposed to NaOCl at 5 different concentrations. Cell viability was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alamarBlue assays. The cell morphology changes were assessed with scanning electron microscopy (SEM) after exposure to 2, 4, and 24 hour incubation. The ethidium bromide/acridine orange (EB/ AO) fuorescent stain was applied to the cells in the 8-chamber slides after they were incubated with the testing agents for 2 and 4 hours to detect live and dead cells. The observations were quantitatively and qualitatively analyzed.

RESULTS

The cell viability study using MTT assay and AB assay showed significant reduction with varying concentration at 2 and 4 hours incubation period. The cell viability decreased with the higher percentage of NaOCl. The exposure time also revealed an inverse relation to the cell viability. The SEM analysis showed reduction in the number of cells and morphological alterations with 0.5 mg/ml at 2 and 4 hours compared to 0.025 mg/ml NaOCl. Destruction of the cells with structural alterations and lysis was evident under fuorescence microscope when the cells were exposed to 0.5 mg/ml NaOCl.

CONCLUSION

Within the limitations of this in vitro study it can be concluded that NaOCl is toxic to the human bone marrow MSCs. The cell lysis was evident with higher concentration of sodium hypochlorite. From the observations, it can be concluded that a lower concentration of NaOCl may be used as endodontic irrigant due to its cytotoxic properties. Further studies are mandatory to evolve a consensus on the optimal concentration of sodium hypochlorite to be used as endodontic irrigant.