Automatic quantitation of cell growth and determination of mitotic index using DAPI nuclear staining

Photodynamic therapy with curcumin and near-infrared radiation as an antitumor strategy to glioblastoma cells

Glioblastoma is a malignant neoplasm that develops in the central nervous system and is characterized by high rates of cell proliferation and invasion, presenting resistance to treatments and a poor prognosis. Photodynamic therapy (PDT) is a therapeutic modality that can be applied in oncological cases and stands out for being less invasive. Photosensitizers (PS) of natural origin gained prominence in PDT. Curcumin (CUR) is a natural compound that has been used in PDT, considered a promising PS. In this work, we evaluated the effects of PDT-mediated CUR and near-infrared radiation (NIR) in glioblastoma cells. Through trypan blue exclusion analysis, we chose the concentration of 5 μM of CUR and the dose of 2 J/cm2 of NIR that showed better responses in reducing the viable cell number in the C6 cell line and did not show cytotoxic/cytostatic effects in the HaCat cell line. Our results show that there is a positive interaction between CUR and NIR as a PDT model since there was an increase in ROS levels, a decrease in cell proliferation, increase in cytotoxicity with cell death by autophagy and necrosis, in addition to the presence of oxidative damage to proteins. These results suggest that the use of CUR and NIR is a promising strategy for the antitumor application of PDT.

D-MAINS: A Deep-Learning Model for the Label-Free Detection of Mitosis, Apoptosis, Interphase, Necrosis, and Senescence in Cancer Cells

BACKGROUND

Identifying cells engaged in fundamental cellular processes, such as proliferation or living/death statuses, is pivotal across numerous research fields. However, prevailing methods relying on molecular biomarkers are constrained by high costs, limited specificity, protracted sample preparation, and reliance on fluorescence imaging.

METHODS

Based on cellular morphology in phase contrast images, we developed a deep-learning model named Detector of Mitosis, Apoptosis, Interphase, Necrosis, and Senescence (D-MAINS).

RESULTS

D-MAINS utilizes machine learning and image processing techniques, enabling swift and label-free categorization of cell death, division, and senescence at a single-cell resolution. Impressively, D-MAINS achieved an accuracy of 96.4 ± 0.5% and was validated with established molecular biomarkers. D-MAINS underwent rigorous testing under varied conditions not initially present in the training dataset. It demonstrated proficiency across diverse scenarios, encompassing additional cell lines, drug treatments, and distinct microscopes with different objective lenses and magnifications, affirming the robustness and adaptability of D-MAINS across multiple experimental setups.

CONCLUSIONS

D-MAINS is an example showcasing the feasibility of a low-cost, rapid, and label-free methodology for distinguishing various cellular states. Its versatility makes it a promising tool applicable across a broad spectrum of biomedical research contexts, particularly in cell death and oncology studies.

Vincamine, a safe natural alkaloid, represents a novel anticancer agent

Vincamine, a well-known plant alkaloid, has been used as a dietary supplement and as a peripheral vasodilator to combat aging in humans. In this study, for the very first time, we demonstrated that vincamine can function as an anticancer agent in a human alveolar basal epithelial cell line A549 (IC₅₀ = 309.7 μM). The anticancer potential of vincamine in A549 cells was assessed by molecular assays to determine cell viability, generation of intracellular ROS, nuclear condensation, caspase-3 activity and inhibition, and change in mitochondrial membrane potential (ΔΨm). In silico studies predicted that the anti-proliferative potential of vincamine is enhanced by its interaction with the apoptotic protein caspase-3, and that this interaction is driven by two hydrogen bonds and has a high free energy of binding (-5.64 kcal/mol) with an estimated association constant (K_a) of 73.67 μM. We found that vincamine stimulated caspase-3-dependent apoptosis and lowered mitochondrial membrane potential, which ultimately led to cytochrome C release. Vincamine was also found to quench hydroxyl free radicals and deplete iron ions in cancer cells. As a dietary supplement, vincamine is almost non-toxic in BEAS-2B and 3T3-L1 cells. Therefore, we propose that vincamine represents a safe anticancer agent in lung cancer cells. Its role in other cancers has yet to be explored.

The endoplasmic reticulum Ca2+ -ATPase SERCA2b is upregulated in activated microglia and its inhibition causes opposite effects on migration and phagocytosis

Activation of microglia is an early immune response to damage in the brain. Although a key role for Ca²⁺ as trigger of microglial activation has been considered, little is known about the molecular scenario for regulating Ca²⁺ homeostasis in these cells. Taking into account the importance of the endoplasmic reticulum as a cellular Ca²⁺ store, the sarco(endo)plasmic reticulum Ca²⁺ -ATPase (SERCA2b) is an interesting target to modulate intracellular Ca²⁺ dynamics. We found upregulation of SERCA2b in activated microglia of human brain with Alzheimer's disease and we further studied the participation of SERCA2b in microglial functions by using the BV2 murine microglial cell line and primary microglia isolated from mouse brain. To trigger microglia activation, we used the bacterial lipopolysaccharide (LPS), which is known to induce an increase of cytosolic Ca²⁺ . Our results showed an upregulated expression of SERCA2b in LPS-induced activated microglia likely associated to an attempt to restore the increased cytosolic Ca²⁺ concentration. We analyzed SERCA2b contribution in microglial migration by using the specific SERCA inhibitor thapsigargin in scratch assays. Microglial migration was strongly stimulated with thapsigargin, even more than with LPS-induction, but delayed in time. However, phagocytic capacity of microglia was blocked in the presence of the SERCA inhibitor, indicating the importance of a tight control of cytosolic Ca²⁺ in these processes. All together, these results provide for the first time compelling evidence for SERCA2b as a major player regulating microglial functions, affecting migration and phagocytosis in an opposite manner.

Chromosomal Heterogeneity of the G-401 Rhabdoid Tumor Cell Line: Unusual Partial 7p Trisomy

Rhabdoid tumor is a very aggressive and hardly curable pediatric malignancy. It commonly starts in the kidneys but also can occur in the brain, liver, and other organs. The treatment of this tumor usually involves a combination of surgery, radiation, and chemotherapy. Because this tumor is rare, there is still limited experience with a defined standard of care. Cytogenetic analysis is an important routine method to monitor chromosomal aberrations. We have analyzed metaphases of the G-401 rhabdoid tumor cell line. In these cells we have observed metaphases with derivative chromosome 12 arising from partial trisomy 7p. With increasing passage number the numbers of metaphases having this derivative chromosome 12 were found to be higher. In passage number 2 only one metaphase had this pathological chromosome 12. By passage number 10 and passage number 15 about 25 and 95% of this derivative chromosome 12 were found, respectively. We were able to subclone G-401 cells by limiting dilutions and successfully separated cells having apparently normal karyotypes from cells having derivative chromosome 12. Using the cell proliferation assay we showed that clones possessing the derivative chromosome 12 grew more rapidly than clones with normal chromosomes. The cell cycle analysis confirmed this observation. Overall, in this study we describe for the first time a 7p triplication in a rare rhabdoid tumor of kidney. Both types of clones described in this study could be used as a preclinical model to study the involvement of partial chromosome 7 alterations in the development of rhabdoid tumors.

A safe and efficient method to retrieve mesenchymal stem cells from three-dimensional fibrin gels

Mesenchymal stem cells (MSCs) display multipotent characteristics that make them ideal for potential therapeutic applications. MSCs are typically cultured as monolayers on tissue culture plastic, but there is increasing evidence suggesting that they may lose their multipotency over time in vitro and eventually cease to retain any resemblance to in vivo resident MSCs. Three-dimensional (3D) culture systems that more closely recapitulate the physiological environment of MSCs and other cell types are increasingly explored for their capacity to support and maintain the cell phenotypes. In much of our own work, we have utilized fibrin, a natural protein-based material that serves as the provisional extracellular matrix during wound healing. Fibrin has proven to be useful in numerous tissue engineering applications and has been used clinically as a hemostatic material. Its rapid self-assembly driven by thrombin-mediated alteration of fibrinogen makes fibrin an attractive 3D substrate, in which cells can adhere, spread, proliferate, and undergo complex morphogenetic programs. However, there is a significant need for simple cost-effective methods to safely retrieve cells encapsulated within fibrin hydrogels to perform additional analyses or use the cells for therapy. Here, we present a safe and efficient protocol for the isolation of MSCs from 3D fibrin gels. The key ingredient of our successful extraction method is nattokinase, a serine protease of the subtilisin family that has a strong fibrinolytic activity. Our data show that MSCs recovered from 3D fibrin gels using nattokinase are not only viable but also retain their proliferative and multilineage potentials. Demonstrated for MSCs, this method can be readily adapted to retrieve any other cell type from 3D fibrin gel constructs for various applications, including expansion, bioassays, and in vivo implantation.

Acceleration of myofiber formation in culture by a digitized synaptic signal

Developing myofibers require chemical and electrical stimulation to induce functional muscle tissue. Tissue engineering protocols utilize either or both of these to initiate differentiation ex vivo. Current methodologies typically deliver multi-volt electrical signals, which may be hazardous to developing tissues. In attempts to mimic in vivo muscle development, we stimulated cultured muscle precursor cells with a low-voltage (1 mV) digitized synaptic signal derived from cultured cortical neurons. This synaptic signal induced larger and more adherent myofibers, along with markers of myoblast differentiation, compared to those induced following stimulation with a conventional (28 V) square signal. These findings suggest that stimulation with a digitized synaptic signal may be useful in tissue engineering and physical therapy.

14-3-3 σ expression effects G2/M response to oxygen and correlates with ovarian cancer metastasis

BACKGROUND

In vitro cell culture experiments with primary cells have reported that cell proliferation is retarded in the presence of ambient compared to physiological O₂ levels. Cancer is primarily a disease of aberrant cell proliferation, therefore, studying cancer cells grown under ambient O₂ may be undesirable. To understand better the impact of O₂ on the propagation of cancer cells in vitro, we compared the growth potential of a panel of ovarian cancer cell lines under ambient (21%) or physiological (3%) O₂.

PRINCIPAL FINDINGS

Our observations demonstrate that similar to primary cells, many cancer cells maintain an inherent sensitivity to O₂, but some display insensitivity to changes in O₂ concentration. Further analysis revealed an association between defective G2/M cell cycle transition regulation and O₂ insensitivity resultant from overexpression of 14-3-3 σ. Targeting 14-3-3 σ overexpression with RNAi restored O₂ sensitivity in these cell lines. Additionally, we found that metastatic ovarian tumors frequently overexpress 14-3-3 σ, which in conjunction with phosphorylated RB, results in poor prognosis.

CONCLUSIONS

Cancer cells show differential proliferative sensitivity to changes in O₂ concentration. Although a direct link between O₂ insensitivity and metastasis was not determined, this investigation showed that an O₂ insensitive phenotype in cancer cells to correlate with metastatic tumor progression.

Synergistic neurotoxic effects of arsenic and dopamine in human dopaminergic neuroblastoma SH-SY5Y cells

Parkinson's disease is an environmentally influenced, neurodegenerative disease of unknown origin that is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta of the brain. Arsenic is an environmental contaminant found naturally in ground water, industrial waste, and fertilizers. The initial goal of the present study was to determine if a mixture of arsenite (As(+3)) and dopamine (DA) could cause enhanced degeneration of dopaminergic neuronal cells. Additional goals were to determine the mechanism (apoptosis or necrosis) of As- and DA-induced cell death and if death could be attenuated by antioxidants. The cell culture model employed was the SH-SY5Y neuroblastoma cell line that has been shown to possess differentiated characteristics of dopaminergic neurons. The results demonstrated that a mixture of As(+3) and DA was synergistic in producing the death of the SH-SY5Y cells when compared with exposure to either agent alone. A mixture of 10muM As(+3) and 100muM DA produced almost a complete loss of cell viability over a 24-h period of exposure, whereas, each agent alone had minimal toxicity. It was shown that necrosis, and not apoptosis, was the mechanism of cell death produced by exposure of the SH-SY5Y cells to the mixture of As(+3) and DA. It was also demonstrated that the antioxidants, N-acetylcysteine, and Sulforaphane, attenuated the toxicity of the mixture of As(+3) and DA to the SH-SY5Y cells. This study provides initial evidence that As(+3) and DA synergistically can cause enhanced toxicity in cultured neuronal cells possessing dopaminergic differentiation.

Statistical methods for estimating doubling time in in vitro cell growth

Doubling time has been widely used to represent the growth pattern of cells. A traditional method for finding the doubling time is to apply gray-scaled cells, where the logarithmic transformed scale is used. As an alternative statistical method, the log-linear model was recently proposed, for which actual cell numbers are used instead of the transformed gray-scaled cells. In this paper, I extend the log-linear model and propose the extended log-linear model. This model is designed for extra-Poisson variation, where the log-linear model produces the less appropriate estimate of the doubling time. Moreover, I compare statistical properties of the gray-scaled method, the log-linear model, and the extended log-linear model. For this purpose, I perform a Monte Carlo simulation study with three data-generating models: the additive error model, the multiplicative error model, and the overdispersed Poisson model. From the simulation study, I found that the gray-scaled method highly depends on the normality assumption of the gray-scaled cells; hence, this method is appropriate when the error model is multiplicative with the log-normally distributed errors. However, it is less efficient for other types of error distributions, especially when the error model is additive or the errors follow the Poisson distribution. The estimated standard error for the doubling time is not accurate in this case. The log-linear model was found to be efficient when the errors follow the Poisson distribution or nearly Poisson distribution. The efficiency of the log-linear model was decreased accordingly as the overdispersion increased, compared to the extended log-linear model. When the error model is additive or multiplicative with Gamma-distributed errors, the log-linear model is more efficient than the gray-scaled method. The extended log-linear model performs well overall for all three data-generating models. The loss of efficiency of the extended log-linear model is observed only when the error model is multiplicative with log-normally distributed errors, where the gray-scaled method is appropriate. However, the extended log-linear model is more efficient than log-linear model in this case.

Quantitation of fibroblast population growth rate in situ using computerized image analysis

The development of computer-assisted image analysis has provided the technology to rapidly determine the population size of cultured cell monolayers in situ. We have adapted this technology to determine the population growth rate of cultured fibroblasts for use in a high-replicate format. Human lung fibroblasts were seeded into 1/2 A 96-well plates that had one-half the culture area of standard 96-well plates. The cells were cultured in medium supplemented with different concentrations of FBS and on days 0, 1, 2, 3, 5, and 7, and their nuclei were stained with propidium iodide. A microscopic field representing one-quarter of a well of fluorescent nuclear images was captured onto a Macintosh computer, and the number of nuclei were counted using an image analysis software program. There were no significant differences between the number of nuclei counted manually and the number counted using computer-assisted software, until day 7 where the cells were multilayered (P < 0.05). This image analysis method was compared to other assays typically used to estimate cell proliferation or population size, namely hemocytometer counting, a rapid colorimetric staining assay using naphthol blue-black, and [3H]-thymidine incorporation. The growth rates derived using image analysis were in close agreement with results derived from hemocytometer counts and [3H]-thymidine incorporation. However, the growth rates of cells grown in high concentrations of FBS as determined using naphthol blue-black were substantially lower than results from image analysis. We conclude that this adaptation of computer-assisted image analysis provides a method to derive accurate growth curves by directly counting the number of cells in a large number of replicates.

Exposure of human proximal tubule cells to cytotoxic levels of CdCl2 induces the additional expression of metallothionein 1A mRNA

Humans, in contrast to animals, have a complex expression of metallothionein (MT) genes which involves many MT isoforms encoded by a family of genes containing an upper limit of 12 possible functional genes. It is unknown if these human isoforms of MT have distinct functions or if they simply represent a non-essential duplication of gene function. In the present study, MT protein and mRNA for the MT-2A, MT-1A, B, E, F, and G genes was determined for 3 isolates of human proximal tubule (HPT) cells having distinct sensitivities to cadmium. For all 3 HPT isolates, the expression of MT protein and mRNA for the MT-2A, MT-1E, MT-1F and MT-1G isoforms was similar among the isolates and demonstrated no correlation to lethality. However, each isoform mRNA was expressed at different levels when compared to one another. In contrast, the expression of MT-1A mRNA differed in expression and correlated with the differing lethalities displayed by each isolate. The finding of different profiles of mRNA expression provides evidence that the MT isoforms may have unique functions and that mRNA for the MT-1A gene could be a potential marker for heavy metal exposure and/or toxicity.