Quantification of fluorescence intensity of labeled human mesenchymal stem cells and cell counting of unlabeled cells in phase-contrast imaging: an open-source-based algorithm

Microenvironment-responsive DNA-conjugated albumin nanocarriers for targeted therapy

Drug delivery with accurate targeting and efficient treatment has become an essential strategy for cancer therapy. Two nanocarriers based on bovine serum albumin (BSA) and DNA were synthesized via click chemistry and DNA hybridization reactions (DNA-BSA1 and DNA-BSA2). One of the hybridized oligonucleotides, Linker1, in DNA-BSA1 included a pH-sensitive i-motif sequence and a cancer cell-targeted guanine-quadruplex-structured AS1411 aptamer sequence, and the other, Linker2, in DNA-BSA2 had only the same pH-sensitive i-motif sequence. Doxorubicin (DOX) molecules could be quickly and preferentially intercalated into double-stranded DNA via non-covalent interactions, and the encapsulation efficiency of DNA-BSA1 and DNA-BSA2 was almost 100% and 87.5%, respectively. As a mimic of the cancer cell microenvironment, a pH-trigger and a deoxyribonuclease I (DNase I)-trigger release mechanism was individually proposed to explain the dynamic release of the DNA-BSA@DOX under acidic conditions and the presence of DNase I in vitro. Intracellular uptake and cytotoxicity experiments confirmed that the nanocarrier DNA-BSA1@DOX had accurate targeting and efficient treatment towards cancer cells due to the high affinity and specificity of AS1411 to nucleolin, which is overexpressed in cancer cells. Furthermore, in vivo studies showed that the nanocarrier system could efficiently inhibit tumor growth. Therefore, the entire bio-based nanocarrier DNA-BSA is a promising candidate for the loading and release of anti-cancer drugs for accurate delivery and efficient treatment.

Thermoinduced Crystallization-Driven Self-Assembly of Bioinspired Block Copolymers in Aqueous Solution

Delicate control over architectures via crystallization-driven self-assembly (CDSA) in aqueous solution, particularly combined with external stimuli, is rare and challenging. Here, we report a stepwise CDSA process thermally initiated from amphiphilic poly(N-allylglycine)-b-poly(N-octylglycine) (PNAG-b-PNOG) conjugated with thiol-terminated triethylene glycol monomethyl ethers ((PNAG-g-EG₃)-b-PNOG) in aqueous solution. The diblock copolymers show a reversible thermoresponsive behavior with nearly identical cloud points in both heating and cooling runs. In contrast, the morphology transition of the assemblies is irreversible upon a heating-cooling cycle because of the presence of a confined domain arising from crystalline PNOG, which allows for the achievement of different nanostructured assemblies by the same polymer. We demonstrated that the thermoresponsive property of PNAG-g-EG₃ initiates assembly kinetically that is subsequently promoted by crystallization of PNOG thermodynamically. The irreversible morphology transition behavior provides a convenient platform for comparing the cellular uptake efficiency of nanostructured assemblies with various morphologies that are otherwise similar.

In Vitro Studies on a Microfluidic Sensor with Embedded Obstacles Using New Antibacterial Synthetic Compounds (1-TDPPO) Mixed Prop-2-en-1-one with Difluoro Phenyl

This paper describes the use of an analytical microfluidic sensor for accelerating chemo-repellent response and strong anti-bacterial 1-(Thien-2-yl)-3-(2, 6-difluoro phenyl) prop-2-en-1-one (1-TDPPO). The chemically-synthesized antimicrobial agent, which included prop-2-en-1-one and difluoro phenyl groups, was moving through an optically transparent polydimethylsiloxane (PDMS) microfluidic sensor with circular obstacles arranged evenly. The response, growth and distribution of fluorescent labeling Pseudomonas aeruginosa PAO1 against the antimicrobial agent were monitored by confocal laser scanning microscope (CLSM). The microfluidic sensor along with 1-TDPPOin this study exhibits the following advantages: (i) Real-time chemo-repellent responses of cell dynamics; (ii) Rapid eradication of biofilm by embedded obstacles and powerful antibacterial agents, which significantly reduce the response time compared to classical methods; (iii) Minimal consumption of cells and antimicrobial agents; and (iv) Simplifying the process of the normalization of the fluorescence intensity and monitoring of biofilm by captured images and datasets.

Vitamin C enhances epigenetic modifications induced by 5-azacytidine and cell cycle arrest in the hepatocellular carcinoma cell lines HLE and Huh7

Background

5-Azacytidine (5-AZA), a DNA methyl transferase inhibitor, is a clinically used epigenetic drug for cancer therapy. Recently, we have shown that 5-AZA upregulates ten-eleven translocation (TET) protein expression in hepatocellular carcinoma (HCC) cells, which induce active demethylation. Vitamin C facilitates TET activity and enhances active demethylation. The aim of this study is to investigate whether vitamin C is able to enhance the effect of 5-AZA on active demethylation and to evaluate its consequence in HCC cell lines.

Methods

HCC cell lines (Huh7 and HLE) were treated with 5-AZA and vitamin C. After 48 h of treatment, viability (resazurin conversion), toxicity (lactose dehydrogenase (LDH) release), and proliferation ((proliferating cell nuclear antigen (PCNA)) of single- and combined-treated cells were assessed. The effect of the treatment on 5-hydroxymethylcytosine (5hmC) intensity (immunofluorescence (IF) staining), TET, Snail, GADD45B, and P21 mRNA (real-time PCR) and protein expression (Western blot) were investigated.

Results

Our results indicated that vitamin C enhances the anti-proliferative and apoptotic effect of 5-AZA in HCC cell lines. By further analyzing the events leading to cell cycle arrest, we have shown for the first time in HCC that the combination of 5-AZA and vitamin C leads to an enhanced downregulation of Snail expression, a key transcription factor governing epithelial-mesenchymal transition (EMT) process, and cell cycle arrest.

Conclusions

We conclude that when combined with 5-AZA, vitamin C enhances TET activity in HCC cells, leading to induction of active demethylation. An increase in P21 expression as a consequence of downregulation of Snail accompanied by the induction of GADD45B expression is the main mechanism leading to cell cycle arrest in HCCs.

Dynamic In Vivo SPECT Imaging of Neural Stem Cells Functionalized with Radiolabeled Nanoparticles for Tracking of Glioblastoma

There is strong clinical interest in using neural stem cells (NSCs) as carriers for targeted delivery of therapeutics to glioblastoma. Multimodal dynamic in vivo imaging of NSC behaviors in the brain is necessary for developing such tailored therapies; however, such technology is lacking. Here we report a novel strategy for mesoporous silica nanoparticle (MSN)-facilitated NSC tracking in the brain via SPECT.

METHODS

(111)In was conjugated to MSNs, taking advantage of the large surface area of their unique porous feature. A series of nanomaterial characterization assays was performed to assess the modified MSN. Loading efficiency and viability of NSCs with (111)In-MSN complex were optimized. Radiolabeled NSCs were administered to glioma-bearing mice via either intracranial or systemic injection. SPECT imaging and bioluminescence imaging were performed daily up to 48 h after NSC injection. Histology and immunocytochemistry were used to confirm the findings.

RESULTS

(111)In-MSN complexes show minimal toxicity to NSCs and robust in vitro and in vivo stability. Phantom studies demonstrate feasibility of this platform for NSC imaging. Of significance, we discovered that decayed (111)In-MSN complexes exhibit strong fluorescent profiles in preloaded NSCs, allowing for ex vivo validation of the in vivo data. In vivo, SPECT visualizes actively migrating NSCs toward glioma xenografts in real time after both intracranial and systemic administrations. This is in agreement with bioluminescence live imaging, confocal microscopy, and histology.

CONCLUSION

These advancements warrant further development and integration of this technology with MRI for multimodal noninvasive tracking of therapeutic NSCs toward various brain malignancies.

Induction of active demethylation and 5hmC formation by 5-azacytidine is TET2 dependent and suggests new treatment strategies against hepatocellular carcinoma

BACKGROUND

Global deregulation of DNA methylation is one of the crucial causes of hepato cellular carcinoma (HCC). It has been reported that the anti-cancer drug 5-azacytidine (5-AZA) mediates the activation of tumor suppressor genes through passive demethylation by inhibiting DNMT1. Recent evidence suggests that active demethylation which is mediated by ten-eleven translocation (TET) proteins may also be an important step to control global methylation. However, there exists a controversial discussion in which TET proteins are involved in the demethylation process in HCC. Therefore, we firstly wanted to identify which of the TETs are involved in demethylation and later to study whether or not 5-AZA could trigger the TET-dependent active demethylation process in HCC. HCC cell lines (Huh-7, HLE, HLF), primary human hepatocytes (hHeps), and tissues from both healthy (55 patients) and HCC patients (55 patients) were included in this study; mRNA levels of isocitrate dehydrogenase (IDH1, 2) and TETs (TET1-3) were studied via qPCR and confirmed by Western blot. The expression of 5hmC/5mC was determined by immunohistochemistry in human HCC tissues and the corresponding adjacent healthy liver. HCC cell lines were stimulated with 5-AZA (0-20 μM) and viability (Resazurin conversion), toxicity (LDH release), proliferation (PCNA), and 5hmC/5mC distribution were assessed. In addition, knockdown experiments on TET proteins in HCC cell lines using short interference RNAs (siRNAs), in the presence and absence of 5-AZA, were performed.

RESULTS

Our data applying qPCR, immunofluorescence, and Western blotting clearly show that TET2 and TET3 but not TET1 were significantly decreased in HCC tissue and different HCC cell lines compared to non-tumor liver tissues and hHeps. In addition, we show here for the first time applying knockdown experiments that 5-AZA is able to trigger an active TET2-dependent demethylation process with concomitant significant changes in 5hmC/5mC in HCC cell lines and hHeps.

CONCLUSIONS

Our data clearly show that the expression and activity of TET2 and TET3 proteins but not TET1 are impaired in hepatocellular carcinoma leading to the reduction of 5hmC in HCCs. Furthermore, this study identified a novel function of 5-azacytidine in promoting a TET-mediated generation of 5hmC suggesting that the availability of 5-AZA in cancer cells will have various effects on different epigenetic targets. These findings may open new therapeutic strategies for epigenetic drugs to treat HCC.

Impairment of hypoxia-induced HIF-1α signaling in keratinocytes and fibroblasts by sulfur mustard is counteracted by a selective PHD-2 inhibitor

Skin exposure to sulfur mustard (SM) provokes long-term complications in wound healing. Similar to chronic wounds, SM-induced skin lesions are associated with low levels of oxygen in the wound tissue. Normally, skin cells respond to hypoxia by stabilization of the transcription factor hypoxia-inducible factor 1 alpha (HIF-1α). HIF-1α modulates expression of genes including VEGFA, BNIP3, and MMP2 that control processes such as angiogenesis, growth, and extracellular proteolysis essential for proper wound healing. The results of our studies revealed that exposure of primary normal human epidermal keratinocytes (NHEK) and primary normal human dermal fibroblasts (NHDF) to SM significantly impaired hypoxia-induced HIF-1α stabilization and target gene expression in these cells. Addition of a selective inhibitor of the oxygen-sensitive prolyl hydroxylase domain-containing protein 2 (PHD-2), IOX2, fully recovered HIF-1α stability, nuclear translocation, and target gene expression in NHEK and NHDF. Moreover, functional studies using a scratch wound assay demonstrated that the application of IOX2 efficiently counteracted SM-mediated deficiencies in monolayer regeneration under hypoxic conditions in NHEK and NHDF. Our findings describe a pathomechanism by which SM negatively affects hypoxia-stimulated HIF-1α signaling in keratinocytes and fibroblasts and thus possibly contributes to delayed wound healing in SM-injured patients that could be treated with PHD-2 inhibitors.

Improving reliability of live/dead cell counting through automated image mosaicing

Cell counting is one of the basic needs of most biological experiments. Numerous methods and systems have been studied to improve the reliability of counting. However, at present, manual cell counting performed with a hemocytometer still represents the gold standard, despite several problems limiting reproducibility and repeatability of the counts and, at the end, jeopardizing their reliability in general. We present our own approach based on image processing techniques to improve counting reliability. It works in two stages: first building a high-resolution image of the hemocytometer's grid, then counting the live and dead cells by tagging the image with flags of different colours. In particular, we introduce GridMos (http://sourceforge.net/p/gridmos), a fully-automated mosaicing method to obtain a mosaic representing the whole hemocytometer's grid. In addition to offering more significant statistics, the mosaic "freezes" the culture status, thus permitting analysis by more than one operator. Finally, the mosaic achieved can thus be tagged by using an image editor, thus markedly improving counting reliability. The experiments performed confirm the improvements brought about by the proposed counting approach in terms of both reproducibility and repeatability, also suggesting the use of a mosaic of an entire hemocytometer's grid, then labelled trough an image editor, as the best likely candidate for the new gold standard method in cell counting.

Semi-quantitative monitoring of confluence of adherent mesenchymal stromal cells on calcium-phosphate granules by using widefield microscopy images

The analysis of cell confluence and proliferation is essential to design biomaterials and scaffolds to use as bone substitutes in clinical applications. Accordingly, several approaches have been proposed in the literature to estimate the area of the scaffold covered by cells. Nevertheless, most of the approaches rely on sophisticated equipment not employed for routine analyses, while the rest of them usually do not provide significant statistics about the cell distribution. This research aims at studying confluence and proliferation of mesenchymal stromal cells (MSC) adherent on OSPROLIFE(®), a commercial biomaterial in the form of granules. In particular, we propose a Computer Vision approach that can routinely be employed to monitor the surface of the single granules covered by cells because only a standard widefield fluorescent microscope is required. In order to acquire significant statistics data, we analyse wide-area images built by using MicroMos v2.0, an updated version of a previously published software specific for stitching brightfield and phase-contrast images manually acquired via a widefield microscope. In particular, MicroMos v2.0 permits to build accurate "mosaics" of fluorescent images, after correcting vignetting and photo-bleaching effects, providing a consistent representation of a sample region containing numerous granules. Then, our method allows to make automatically a statistically significant estimate of the percentage of the area of the single granules covered by cells. Finally, by analysing hundreds of granules at different time intervals we also obtained reliable data regarding cell proliferation, confirming that not only MSC adhere onto the OSPROLIFE(®) granules, but even proliferate over time.

5-azacytidine improves the osteogenic differentiation potential of aged human adipose-derived mesenchymal stem cells by DNA demethylation

The therapeutic value of adipose-derived mesenchymal stem cells (Ad-MSCs) for bone regeneration is critically discussed. A possible reason for reduced osteogenic potential may be an age-related deterioration of the Ad-MSCs. In long term in vitro culture, epigenomic changes in DNA methylation are known to cause gene silencing, affecting stem cell growth as well as the differentiation potential. In this study, we observed an age-related decline in proliferation of primary human Ad-MSCs. Decreased Nanog, Oct4 and Lin28A and increased Sox2 gene-expression was accompanied by an impaired osteogenic differentiation potential of Ad-MSCs isolated from old donors (>60 a) as compared to Ad-MSCs isolated from younger donors (<45 a). 5-hydroxymethylcytosine (5 hmC) and 5-methylcytonsine (5 mC) distribution as well as TET gene expression were evaluated to assess the evidence of active DNA demethylation. We observed a decrease of 5 hmC in Ad-MSCs from older donors. Incubation of these cells with 5-Azacytidine induced proliferation and improved the osteogenic differentiation potential in these cells. The increase in AP activity and matrix mineralization was associated with an increased presence of 5 hmC as well as with an increased TET2 and TET3 gene expression. Our data show, for the first time, a decrease of DNA hydroxymethylation in Ad-MSCs which correlates with donor-age and that treatment with 5-Azacytidine provides an approach which could be used to rejuvenate Ad-MSCs from aged donors.

Comparison of different strategies for in vivo seeding of prevascularized scaffolds

Scaffolds seeded with multipotent precursor cells were hypothesized to heal critically sized bone defects. However, the success of this concept was limited by low cell survival after transplantation due to a lack of nutrients and oxygen. In vivo prevascularization of scaffolds before cell seeding may improve cell survival, yet the best seeding technique and time point of cell application remain elusive. Thus, the aim of this study was to compare different strategies. Demineralized bone matrix scaffolds were implanted around the saphenous arteriovenous (AV) bundle in nude mice. In vivo seeding was performed 0, 5, or 21 days after implantation using enhanced green fluorescent protein (eGFP)-expressing mesenchymal stem cells (MSCs). Cells were applied either by injection or the repetitive dripping technique. In vitro seeded and subcutaneously implanted scaffolds served as controls. Fourteen days after cell application, the fluorescence intensity of transplanted cells and the extent of newly formed vessels were quantified. We found that the AV flow through model as well as cell application increased vessel formation. In vitro seeding resulted in significantly higher cell numbers than in vivo seeding. With increasing time of prevascularization, the number of cells declined dramatically. In vivo seeding by cell injection was superior to the repetitive dripping protocol. On subcutaneously implanted scaffolds, significantly, more cells were found than on axially perfused scaffolds. We conclude that in vitro seeding is more efficient compared to the two novel in vivo seeding techniques of prevascularized scaffolds. With increasing time of prevascularization, the seeding efficiency for the in vivo methods further decreases, presumably due to the ingrowth of connective tissue. Even though, the presence of MSCs and the longer period of prevascularization enhances vessel formation, this conceivable advantage is limited supposedly by the inferior seeding efficiency.

Long-term detection of fluorescently labeled human mesenchymal stem cell in vitro and in vivo by semi-automated microscopy

The use of seeded scaffolds in regenerative medicine is limited by the low survival of transplanted mesenchymal stem cells (MSC). Current approaches aim at improving cell viability but require an adequate long-term detection of the transplanted cells. Unfortunately, commonly performed labeling techniques have not been validated for this purpose, and studies often reveal inconclusive results. Consequently, we intended to identify the most suitable method for long-term detection of human MSC (hMSC) in vitro and in vivo. hMSC were labeled using the vital stainings PKH26 and carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) as well as enhanced green fluorescent protein (eGFP) transduction. Metabolic activity and relative fluorescence intensity (RFI) were quantified in vitro over 21 days at 8 time points using standardized semi-automated microscopy and flow cytometry. In vivo, cell seeded scaffolds were subcutaneously implanted in nude mice, and RFI was analyzed over 42 days at 5 time points. In vitro, PKH26 and CFDA-SE significantly reduced metabolic activity. RFI of both stainings significantly decreased after 1 day and further faded to <1% after 7 days. In contrast, labeling with eGFP showed no metabolic effect on hMSC, and no significant reduction of RFI over the total period of 21 days. In vivo, RFI of eGFP labeled cells reached a plateau phase after 21 days and displayed a 3.8-fold higher RFI compared with PKH26 and CFDA-SE on day 42 evaluated in 280 field of views per scaffold using three scaffolds for each labeling technique and time point. We conclude that PKH26 and CFDA-SE are unsuitable for long-term detection of hMSC. eGFP transduction, in turn, allows long-term detection of hMSC in vitro and in vivo. Our results suggest that eGFP is currently the best option among the fluorescent labeling techniques to follow the fate of transplanted hMSC.

Modulation of embryonic mesenchymal progenitor cell differentiation via control over pure mechanical modulus in electrospun nanofibers

As the potential range of stem cell applications in tissue engineering continues to grow, the appropriate scaffolding choice is necessary to create tightly defined artificial microenvironments for each target organ. These microenvironments determine stem cell fate via control over differentiation. In this study we examined the specific effects of scaffold stiffness on embryonic mesenchymal progenitor cell behavior. Mechanically distinct scaffolds having identical microstructures and surface chemistries were produced utilizing core-shell electrospinning. The modulus of core-shell poly(ether sulfone)-poly(ε-caprolactone) (PES-PCL) fibers (30.6 MPa) was more than four times that of pure PCL (7.1 MPa). The results for chondrogenic and osteogenic differentiation of progenitor cells on each scaffold indicate that the lower modulus PCL fibers provided more appropriate microenvironments for chondrogenesis, evident by a marked up-regulation of chondrocytic Sox9, collagen type 2, and aggrecan gene expression and chondrocyte-specific extracellular matrix glycosaminoglycan production. In contrast, the stiffer core-shell PES-PCL fibers supported enhanced osteogenesis by promoting osteogenic Runx2, alkaline phosphatase, and osteocalcin gene expression, as well as alkaline phosphatase activity. The findings demonstrate that the microstructural stiffness/modules of a scaffold and the pliability of individual fibers may play a critical role in controlling stem cell differentiation. Regulation of cytoskeletal organization may occur via a "dynamic scaffold" leading to the subsequent intracellular signaling events that control differentiation-specific gene expression.