For the research of stem cells, various tool are necessary. Among them, immunocytochemistry is a powerful tool for detection and visualization of specific molecules in living or fixed cells, their localization and their relative abundance. One of the most commonly used fluorescent DNA dyes in immunocytochemistry applications is 4',6-diamidino-2-phenylindole dihydrochloride, known as DAPI. DAPI binds strongly to DNA and is used extensively for visualizing cell nuclei. It is excited by UV light and emits characteristic blue fluorescence. Here, we report a phenomenon based on an apparent photoconversion of DAPI that results in detection of a DAPI signal using a standard filter set for detection of green emission due to blue excitation. When a sample stained with DAPI only was first imaged with the green filter set (FITC/GFP), only a weak cytoplasmic autofluorescence was observed. Next, we imaged the sample with a DAPI filter set, obtaining a strong nuclear DAPI signal as expected. Upon reimaging the same samples with a FITC/GFP filter set, robust nuclear fluorescence was observed. We conclude that excitation with UV results in a photoconversion of DAPI that leads to detection of DAPI due to excitation and emission in the FITC/GFP channel. Thisphenomenon can affect data interpretation and lead to false-positive results when used together with fluorochrome-labeled nuclear proteins detectedwith blue excitation and green emission. In order to avoid misinterpretations, extra precaution should be taken to prepare staining solutions with low DAPI concentration and DAPI (UV excitation) images should be acquired after all other higher wavelength images. Of various DNA dyes tested, Hoechst 33342 exhibited the lowest photoconversion while that for DAPIand Hoechst 33258 was much stronger. Different fixation methods did not substantially affect the strength of photoconversion. (Abs. trunc. at 2000 ch.)
COBISS.SI-ID: 30233561
Immune phenomena in stem cell transplantation are not yet completely known. One of these are the TLR receptors on immune cells. Toll-like receptor 4 (TLR4) in complex with its accessory protein MD-2 represents an emerging target for the treatment of severe sepsis and neuropathic pain. We performed structure-based and ligand-based virtual screening targeting the TLR4-MD-2 interface. Three in silico hit compounds showed promising TLR4 antagonistic activities with micromolar IC50 values. These compounds also suppressed cytokine secretion by human peripheral blood mononuclear cells. The specific affinity of the most potent hit was confirmed by surface plasmon resonance direct-binding experiments. The results of our study represent a very promising starting point for the development of potent small-molecule antagonists of TLR4.
COBISS.SI-ID: 3538289
Differentiation of stem cells can be evaluated by the expression of their genes. The POU5F1 gene codes for the OCT4 transcription factor, which is one of the key regulators of pluripotency. Its transcription, alternative splicing, and alternative translation leading to the synthesis of the active, nuclear localized OCT4A has been described in detail. Much less, however, is known about actively transcribed OCT4 pseudogenes, several of which display high homology to OCT4A and can be expressed and translated into proteins. Using RT-PCR followed by pseudogene-specific restriction digestion, cloning, and sequencing we discriminate between OCT4A and transcripts for pseudogenes 1, 3 and 4. We show that expression of OCT4 and its pseudogenes follows a developmentally-regulated pattern in differentiating hESCs, indicating a tight regulatory relationship between them. We further demonstrate that differentiated human cells from a variety of tissues express exclusively pseudogenes. Expression of OCT4A can, however be triggered in adult differentiated cells by oxygen and FGF2-dependent mechanisms.
COBISS.SI-ID: 31179993
After the transplantation of stem cells, various immune effects take place. During the discovery of mechanisms that govern immune activation and suppression, immune tolerance always came second in the scientific timeline. This has subsequently shaped the advances in the clinical translation of DC therapy protocols used for immunostimulation or immunosuppression. With several hundred clinical trials already registered within the U.S. National Institutes of Health for the use of DCs in cancer vaccination, only a few involve TolDCs for use as negative vaccines. However, as a result of the strong scientific rationale from preclinical and clinical trials, the use of negative vaccination in organ transplantation is likely on its way to reach the extent of the use of positive cancer vaccines in the future. As the underlying mechanisms emerge, the role of DCs in the induction of transplant tolerance is recognized unambiguously as central in the bidirectional communication with various types of immune cells. This is achieved by a complex interplay of numerous tolerogenic signals involving regulatory cytokines and other surface-bound or soluble inhibitory molecules associated with corresponding inhibitory signaling cascades. A detailed understanding of these processes will accelerate the advances of clinical immunologists in translating their knowledge from bench to bedside. In this review, we present the role of TolDCs as well as the most recent findings concerning associated molecular and cellular mechanisms that shape the balance between regulatory and effector immune responses during organ transplantation.
COBISS.SI-ID: 3534449
INTRODUCTION: Stem cells are extensively used for treatment of dental disorders. Bone tissue regeneration requires a source of viable, proliferative cells with osteogenic differentiation capacity. Periodontal surgeries represent an opportunity to procure small amounts of autologous tissues for primary cell isolation. Our objective was to assess the potential of human alveolar bone as a source of autologous osteogenic cells for tissue engineering and biomaterials and drug testing studies. MATERIALS AND METHODS: Alveolar bone tissue was obtained from 37 patients undergoing routine periodontal surgery. Tissue harvesting and cell isolation procedures were optimized to isolate viable cells. Primary cells were subcultured and characterized with respect to their growth characteristics, gene expression of osteogenic markers, alkaline phosphatase activity and matrix mineralization, under osteogenic stimulation. RESULTS: Alveolar bone cells were successfully isolated from 28 of the 30 samples harvested with bone forceps, and from 2 of the 5 samples obtained by bone drilling. The yield of cells in primary cultures was variable between the individual samples, but was not related to the site of tissue harvesting and the patient age. In 80% of samples (n = 5), the primary cells proliferated steadily for eight subsequent passages, reaching cumulative numbers over 10(10) cells. Analyses confirmed stable gene expression of alkaline phosphatase, osteopontin and osteocalcin in early and late cell passages. In osteogenic medium, the cells from late passages increased alkaline phosphatase activity and accumulated mineralized matrix, indicating a mature osteoblastic phenotype. CONCLUSIONS: Primary alveolar bone cells exhibited robust proliferation and retained osteogenic phenotype during in vitro expansion, suggesting that they can be used as an autologous cell source for bone regenerative therapies and various in vitro studies.
COBISS.SI-ID: 513984119