细胞生物学

Pseudomonas aeruginosa is a human pathogen capable to form robust biofilms. P. aeruginosa biofilms represent a serious problem because of the adverse effects on human health and industry, from sanitary and economic points of view. Typical strategies to break down biofilms have been long used, such as the use of disinfectants or antibiotics, but also, according to their high resistance to standard antimicrobial approaches, alternative strategies employing photocatalysis or control of biofilm formation by modifying surfaces, have been proposed. Colony forming units (cfu) counting and live/dead staining, two classic techniques used for biofilm quantification, are detailed in this work. Both methods assess cell viability, a key factor to analyze the microbial susceptibility to given treatment, then, they represent a good approach for evaluation of an antibiofilm strategy.

Malaria remains a major cause of morbidity and mortality globally. Clinical symptoms of the disease arise from the growth and multiplication of Plasmodium parasites within the blood of the host. Thus in vitro assays to determine how drug, antibody and genetic perturbations affect the growth rate of Plasmodium parasites are essential for the development of new therapeutics and improving our understanding of parasite biology. As both P. falciparum and P. knowlesi can be maintained in culture with human red blood cells, the effect of antimalarial drugs and inhibitory antibodies that target the invasion or growth capacity of Plasmodium parasites are routinely investigated by using multiplication assays or growth inhibition activity (GIA) assays against these two species. This protocol gives detailed step-by-step procedures to carry out flow cytometry-based multiplication assays and growth inhibition activity assays to test neutralizing antibodies based on the activity of the parasite enzyme lactate dehydrogenase of Plasmodium knowlesi adapted to human red blood cell culture. Whilst similar assays are well established for P. falciparum, P. knowlesi is more closely related to all other human infective species (Pacheco et al., 2018) and so can be used as a surrogate for testing drugs and vaccines for other malaria species such as P. vivax, which is the most widespread cause of malaria outside of Africa, but cannot yet be cultured under laboratory conditions.

Metastasis accounts for the majority of cancer related deaths. The genetically engineered mouse (GEM) models and cell line-based subcutaneous and orthotopic mouse xenografts have been developed to study the metastatic process. By using lung cancer cell line A549 as an example, we present a modified protocol to establish the cell line-based xenograft. Our protocol ensures sufficient establishment of the mouse xenografts and allows us to monitor tumor growth and spontaneous metastasis. This protocol could be adapted to other types of established cancer cell lines or primary cancer cells to study the mechanism of metastatic process as well as to test the effect of the potential anti-cancer agents on tumor growth and metastatic capacity.

Extracellular matrix (ECM)-based tissue engineering scaffolds have an essential role in promoting tissue regeneration. Nerve tissue engineering aims at facilitating the repair of permanent damage to the peripheral and central nervous systems, which are difficult to heal. For this purpose, a variety of biomaterials are being developed consisting of numerous synthetic and/or natural polymers to provide axonal reinnervation and to direct the growth of axons. Here, we present a novel protocol that enables to fabricate a 3-dimensional (3D) decellularized scaffold derived from the bovine spinal cord (BSC) ECM (3D-dCBS) for neural tissue engineering applications. In this protocol, a viscous ECM-derived gel from BSC is prepared, molded, and chemically crosslinked with EDC/NHS (3D-CBS) before decellularization process. Decellularization of 3D-CBS is performed with 1% SDS to attain 3D-dCBS. As compared with other available methods, our protocol is a novel decellularization method that preserves a more significant part of the ECM. We believe that the mentioned protocol has the potential to produce a bioengineered scaffold from spinal cord tissue with desired geometry for regenerative medicine applications related to neural tissue engineering.

Pituitary adenomas are among the more frequent intracranial tumors usually treated with both surgical and pharmacological–based on somatostatin and dopamine agonists–approaches. Although mostly benign tumors, the occurrence of invasive behaviors is often detected resulting in poorer prognosis. The use of primary cultures from human pituitary adenomas represented a significant advancement in the knowledge of the mechanisms of their development and in the definition of the determinants of their pharmacological sensitivity. Moreover, recent studies identified also in pituitary adenomas putative tumor stem cells representing, according to the current hypothesis, the real cellular targets to eradicate most malignancies. In this protocol, we describe the procedure to establish primary cultures from human pituitary adenomas, and how to select, in vitro expand, and phenotypically characterize putative pituitary adenoma stem cells.

We performed an assay to test the ability of different E. coli strains to survive inside amoebal cells after ingestion. In the assay we incubated bacteria together with cells of Dictyostelium discoideum for six hours. After co-incubation most of the uningested bacteria were removed by centrifugation and the remaining uningested bacteria were killed by gentamicin. Gentamicin is used because it does not penetrate into eukaryotic cells allowing the ingested bacteria to survive the antibiotic treatment, whereas bacteria outside the amoebal cells are killed.

Coating tissue culture vessels with the components of the extracellular matrix such as fibronectin and collagens provides a more natural environment for primary cells in vitro and stimulates their proliferation. However, the effects of such protein layers are usually rather modest, which might be explained by the loss immobilized proteins due to their weak non-covalent association with the tissue culture plastic. Here we describe a simple protocol for a controlled fixation of fibronectin, vitronectin and collagen IV layers by formaldehyde, which substantially enhances the stimulation of primary cell proliferation by these extracellular proteins.

The SRB assay has been used since its development in 1990 (Skehan et al., 1990) to inexpensively conduct various screening assays to investigate cytotoxicity in cell based studies (Vichai and Kirtikara, 2006). This method relies on the property of SRB, which binds stoichiometrically to proteins under mild acidic conditions and then can be extracted using basic conditions; thus, the amount of bound dye can be used as a proxy for cell mass, which can then be extrapolated to measure cell proliferation.

The protocol can be divided into four main steps: preparation of treatment, incubation of cells with treatment of choice, cell fixation and SRB staining, and absorbance measurement. This assay is limited to manual or semiautomatic screening, and can be used in an efficient and sensitive manner to test chemotherapeutic drugs or small molecules in adherent cells. It also has applications in evaluating the effects of gene expression modulation (knockdown, gene expression upregulation), as well as to study the effects of miRNA replacement on cell proliferation (Kasinski et al., 2015).

TGFβ is part of a growth factor superfamily which modulates cell growth, differentiation, adhesion, migration, ECM synthesis and apoptosis (Massague, 1998; Siegel and Massague, 2003). Free TGFβ binds to its high affinity TGFβ receptor, a receptor serine/threonine kinase, inducing phosphorylation of Smad2/3 which subsequently forms a complex with Smad4 to translocate to the nucleus where it interacts with multiple co-activators and repressors generating distinct transcriptional responses.

Indeed, TGFβ signaling shows a remarkable cellular context dependency and apparent multifunctionality: e.g. TGFβ is able to inhibit cell proliferation in many epithelial cells but can also enhance proliferation in fibroblasts and cell growth in endothelial cells (Guasch et al., 2007; Xiao et al., 2012); it enhances stem cell pluripotency, but promotes differentiation in other cells (Park, 2011); in cancer development it suppresses pre-malignant cell proliferation, but at the same time promotes conversion to a metastatic phenotype (Chaudhury and Howe, 2009).

The TGFβ stimulation assay monitors the responsiveness of cells to TGFβ. Upon TGFβ stimulation short-term effects such as Smad2 phosphorylation and long-term effects such as cell proliferation can be analyzed. The assay will be described for murine keratinocytes, where TGFβ strongly inhibits cell proliferation, but both assays are applicable for other cell types as well.

In the past years, a subset of regulatory T cells (Tregs) expressing CD4, CD25 and the transcription factor FoxP3 has gained considerable attention as key regulators of T-cell tolerance and homeostasis (Sakaguchi, 2004). This population of T cells is specifically engaged in the maintenance of immune self-tolerance and the control of aberrant immune responses to foreign antigens. Remarkably, regulatory T cells have been implicated in tumor cell evasion of immune responses (Curiel et al., 2004; Zou, 2006) by suppressing T cell mediated antitumor immunity. The study of the signals that promote the differentiation of this suppressive population in the tumor microenvironment has become a central issue. Here we described a detailed method to in vitro differentiate Tregs using tumor cells conditioned media from mouse naïve T cells and to identify them based on their specifics markers (Dalotto-Moreno et al., 2013).