Toward Tailoring the Degradation Rate of Magnesium-Based Biomaterials for Various Medical Applications: Assessing Corrosion, Cytocompatibility and Immunological Effects

Magnesium (Mg)-based biomaterials hold considerable promise for applications in regenerative medicine. However, the degradation of Mg needs to be reduced to control toxicity caused by its rapid natural corrosion. In the process of developing new Mg alloys with various surface modifications, an efficient assessment of the relevant properties is essential. In the present study, a WE43 Mg alloy with a plasma electrolytic oxidation (PEO)-generated surface was investigated. Surface microstructure, hydrogen gas evolution in immersion tests and cytocompatibility were assessed. In addition, a novel in vitro immunological test using primary human lymphocytes was introduced. On PEO-treated WE43, a larger number of pores and microcracks, as well as increased roughness, were observed compared to untreated WE43. Hydrogen gas evolution after two weeks was reduced by 40.7% through PEO treatment, indicating a significantly reduced corrosion rate. In contrast to untreated WE43, PEO-treated WE43 exhibited excellent cytocompatibility. After incubation for three days, untreated WE43 killed over 90% of lymphocytes while more than 80% of the cells were still vital after incubation with the PEO-treated WE43. PEO-treated WE43 slightly stimulated the activation, proliferation and toxin (perforin and granzyme B) expression of CD8⁺ T cells. This study demonstrates that the combined assessment of corrosion, cytocompatibility and immunological effects on primary human lymphocytes provide a comprehensive and effective procedure for characterizing Mg variants with tailorable degradation and other features. PEO-treated WE43 is a promising candidate for further development as a degradable biomaterial.

B cell analysis in SARS-CoV-2 versus malaria: Increased frequencies of plasmablasts and atypical memory B cells in COVID-19

B cells play a central role in antiviral and antiparasitic immunity, not only as producers of antibodies, but also as APCs and mediators of inflammation. In this study, we used 16-color flow cytometry analysis to investigate the frequency, differentiation, and activation status of peripheral B cells of patients with SARS-CoV-2 infection or acute Plasmodium falciparum malaria compared with the healthy individuals. As a main result, we observed an increase of the frequency of (CD27^-, CD21^-) atypical memory B cells and (CD19⁺, CD27⁺, CD38⁺) plasmablasts in malaria and COVID-19 patients. Additionally, CD86, PD-1, CXCR3, and CD39 expression was up-regulated, whereas CD73 was down-regulated on plasmablasts of COVID-19 and malaria patients compared with the bulk B cell population. In particular, there was a more pronounced loss of CD73⁺ B cells in malaria. The frequency of plasmablasts positively correlated with serum levels of CRP, IL-6, and LDH of COVID-19 patients. In the longitudinal course of COVID-19, a rapid normalization of the frequency of atypical memory B cells was observed. The role and function of plasmablasts and atypical memory B cells in COVID-19 and other acute infections remain to be further investigated. The role of B cells as either "driver or passenger" of hyperinflammation during COVID-19 needs to be clarified.

Two simple and inexpensive methods for preparing DNA suitable for digital PCR from a small number of cells in 96-well plates

Background

Although DNA of high quality can be easily prepared from cultured cells with commercially available kits, many studies involve a large number of samples which increases the cost drastically. We optimized two simple and inexpensive methods for preparing DNA suitable for digital PCR from a small number of cells directly from wells of 96‐well plates.

Methods

Cells (number: 10³‐10⁴) were lysed with a Direct PCR^® lysis buffer or a 10% Chelex100® solution. The lysates were further purified and concentrated by means of DNA precipitation with a blue‐colored glycogen as a carrier. PCR and digital PCR were used to evaluate the efficiency of the two methods.

Results

For 1000 cells from one primary culture and two tumor cell lines, DNA was reproducible and obtained with recovery rate (obtained/expected amount of DNA) in the range of 50%‐90% as measured by the fluorometer dyes instrument Qubit. Using 8 out of a total of 10 µL DNA solution for 1000 cells, both conventional PCR and digital PCR were successful. For digital PCR, more than 1600 positive droplets were obtained for DNA from 1000 cells using the Direct PCR^® method, corresponding to a yield efficiency of approximately 80%. Further reducing the number of cells down to 100 would be possible with 160 positive droplets expected. Both reagents are inexpensive (0.08€/sample).

Conclusions

Two methods are efficient, especially the Direct PCR^® reagent‐based method provides a simple and inexpensive method for preparing DNA suitable for digital PCR from small number of cells.

The association between infection burden in Iranian patients with acute myocardial infarction and unstable angina

AIM

to evaluate the association of ischemic heart disease (IHD) with the number of pathogens (infection burden) among individuals with infection.

METHODS

a total of 120 patients with IHD as the acute myocardial infarction (AMI; n=60) or unstable angina (UA; n=60) group and 60 healthy subjects with sex- and age-matched as control group were enrolled in this study. Serum samples of all participants were tested for the presence of antibodies to Helicobacter pylori (H. pylori), cytomegalovirus (CMV), type-1 herpes simplex virus (HSV-1) and type- 2 HSV (HSV-2) by using ELISA.

RESULTS

Regarding the association of the infection burden with IHD, the prevalence ratios and 95% confidence intervals (CI) were 3.18 (CI: 1.50-6.72; P<0.001) for 3 seropositivities and 3.83 (CI: 0.84-17.43; P<0.05) for 4 seropositivities. The rate of subjects with high infection burden (3 seropositivities) was significantly higher in IHD group as compared to control group (53.4% vs 21.6%; P<0.01). Moreover, the mean number of seropositivities was also significantly higher in patients with IHD in comparison to control group (2.47 vs 1.68; P<0.01). The seroprevalence of anti-H. pylori antibodies in AMI and UA groups was significantly higher compared to control group (P<0.0001). The seroprevalence of anti-CMV antibodies in AMI and UA group was also significantly higher than those observed in control group (P<0.01). Moreover, the seroprevalence of anti-HSV-1 antibodies was significantly higher in AMI and UA groups in comparison to control group (P<0.001). The seroprevalence of anti-HSV-2 antibodies was similarly expressed in patients and healthy control group.

CONCLUSION

the infection burden was significantly higher in patients with IHD, which represent that the parameter should also be considered as an independent risk factor for development of IHD. The seroprevalence of H. pylori, CMV and HSV-1 were also higher in patients with IHD.

Serum concentrations of Helicobacter pylori IgG and the virulence factor CagA in patients with ischaemic heart disease

To compare the serum concentrations of IgG to Helicobacter pylori and its virulence factor CagA in patients with ischaemic heart disease (IHD), we recruited 120 patients with IHD [acute myocardial infarction (AMI) (n = 60); unstable angina (UA) (n = 60)] and 60 sex- and age-matched healthy controls in this study. The seroprevalence of anti-H. pylori IgG was 86.7% in AMI, 91.7% in UA patients and 58.3% in the control group with mean titres of 33.2 U/ml [standard error (SE) 4.76], 57.96 U/ml (SE 7.54) and 25.72 U/ml (SE 4.01) respectively. The seroprevalence of anti-H. pylori in the patient groups was significantly higher than the control group. The mean levels of anti-H. pylori in the AMI and UA groups were also significantly higher than in the control group. The seroprevalence and mean titre of anti-CagA IgG did not differ significantly between patient and control groups.

Exploring the phase space of the quantum delta-kicked accelerator

We experimentally explore the underlying pseudoclassical phase space structure of the quantum delta-kicked accelerator. This was achieved by exposing a Bose-Einstein condensate to the spatially corrugated potential created by pulses of an off-resonant standing light wave. For the first time quantum accelerator modes were realized in such a system. By utilizing the narrow momentum distribution of the condensate we were able to observe the discrete momentum state structure of a quantum accelerator mode and also to directly measure the size of the structures in the phase space.

Ultrastructural immunolocalization of basic fibroblast growth factor in mast cell secretory granules. Morphological evidence for bfgf release through degranulation

We previously reported that mast cells (MCs) serve as a source of basic fibroblast growth factor (bFGF), a potent angiogenic and mitogenic polypeptide, suggesting that bFGF may mediate MC-related neovascularization and fibroproliferation. Unlike many other growth factors, bFGF lacks a classic peptide sequence for its secretion, and the mechanism(s) for its release remains controversial. Because MCs release a wide spectrum of bioactive products via degranulation, we hypothesized that MC degranulation may be a mechanism of bFGF release and used ultrastructural immunohistochemistry to test the hypothesis. We reasoned that if bFGF is released through degranulation, it should be localized to MC secretory granules. Human tissues with chronic inflammation and rat/mouse tissues with anaphylaxis were studied. In all tissue samples examined, positive staining (or immunogold particle localization) for bFGF in MCs was predominantly in the cytoplasmic granules. Moderate bFGF immunoreactivity was also found in the nucleus, whereas the cytosol and other subcellular organelles exhibited minimal immunogold particle localization. In contrast, no immunogold particle localization for bFGF was observed in lymphocytes or plasma cells. In rat/mouse lingual tissue undergoing anaphylaxis, immunogold particle localization for bFGF was found not only in swollen cytoplasmic granules but also in the extruded granules of MCs. Three different anti-bFGF antibodies gave similar immunogold particle localization patterns, whereas all controls were negative. These results provide morphological evidence suggesting that, despite the lack of a classic secretory peptide in its structure, bFGF is localized to the secretory granules in MCs and may be released through degranulation.

Synthesis of basic fibroblast growth factor by murine mast cells. Regulation by transforming growth factor beta, tumor necrosis factor alpha, and stem cell factor

BACKGROUND

Mast cells (MC) are involved in a wide spectrum of disorders characterized by neovascularization and fibroproliferation. We and others recently reported that human MC are a source of basic fibroblast growth factor (b FGF-2), a potent angiogenic and mitogenic polypeptide, in several disease conditions, such as chronic inflammation, hemangioma, and benign cutaneous mastocytosis. These findings suggest that FGF-2 may be an important mediator of cell proliferation and angiogenesis associated with MC. Since MC are heterogeneous across species, it is unknown whether FGF-2 expression is a feature common to all MC, or whether FGF-2 expression by MC can be regulated. We therefore examined FGF-2 expression by MC in mouse tissue and MC lines.

METHODS

Immunostaining, RT-PCR, ELISA, immunoblot and Northern blot analyses were employed to study four murine MC lines for FGF-2 expression and its regulation by transforming growth factor-beta (TGF-beta), stem cell factor (SCF), and tumor necrosis factor-alpha (TNF-alpha).

RESULTS

Mouse tissue MC and three of four murine MC lines (CFTL-12, CFTL-15, ABFTL-3) express FGF-2 as judged by immunostaining, ELISA, Western blot and Northern blot analyses, and reverse transcription-polymerase chain reaction. While TNF-alpha appeared to downregulate FGF-2 mRNA levels, treatment with SCF or TGF-beta resulted in an increase in the expression of FGF-2 at mRNA level which can be attenuated by TNF-alpha. However, the concurrent increase in FGF-2 protein was negligible, possibly due to immaturity of these cell lines.

CONCLUSION

Expression of FGF-2 may be a ubiquitous feature of MC in other species in addition to humans, and can be selectively regulated by SCF, TGF-beta and TNF-alpha.

Mast cells are a major source of basic fibroblast growth factor in chronic inflammation and cutaneous hemangioma

Mast cells play an essential role during development of inflammation after chemical and immunological insults and have been implicated in tissue fibrosis and angiogenesis. The exact contribution of mast cells to these conditions is largely unknown. In this study, we found that a potent angiogenic and mitogenic polypeptide, basic fibroblast growth factor (bFGF), is localized to the majority of mast cells from normal skin and lung and in tissue samples characterized by fibrosis, hyperplasia, and neovascularization. Using specific antibodies to mast cell tryptase, tissue macrophage, and bFGF, we demonstrate that cytoplasmic bFGF immunoreactivity is localized to 96.8 +/- 9.6% of tryptase-positive cells in human fibrotic lung tissue (n = 10), 82.3 +/- 6.9% of tryptase-positive cells in rheumatoid synovia (n = 6), and 93.1 +/- 4.8% of tryptase-positive cells in skin hemangioma (n = 5). Moreover, these tryptase-positive cells comprise a major portion (86 to 97%) of nonvascular cells exhibiting cytoplasmic bFGF staining in these tissues. In contrast, macrophage-like cells contribute less than 10% of the bFGF-positive cells in the same samples. The specificity of the immunostaining results was supported by the finding that cultured human mast cells (HMC-1) express both bFGF mRNA and protein. Our data indicate that mast cells, a primary source of heparin, also serve as a significant source of a heparin-binding growth factor, bFGF, in these disease processes. These observations suggest that mast cells may contribute to these pathological conditions by releasing this polypeptide.

Expression of basic fibroblast growth factor in synovial tissue from patients with rheumatoid arthritis and degenerative joint disease

BACKGROUND

Recent studies have implicated polypeptide growth factors in the development of rheumatoid arthritis (RA), which is characterized by synoviocyte hyperplasia and neovascularization. One such polypeptide, basic fibroblast growth factor (bFGF), is of particular interest because of its potent mitogenic and angiogenic activities. We have previously reported that cultured human synoviocytes synthesize and bind bFGF and also proliferate in response to it (1). Recently, we found a close association between increased bFGF expression and destructive changes in arthritic joints from rats (2). Now we extend our study by detecting in vivo expression of bFGF in human synovial tissues obtained from patients with RA.

EXPERIMENTAL DESIGN

Human synovial tissues from patients with RA, degenerative joint disease (DJD), and trauma were collected during joint surgery. The expression of bFGF protein and mRNA by the synovia was examined by immunolocalization, Western blot, Northern blot, and RNase protection assays. Synovium from patients with DJD and trauma was used to compare with rheumatoid synovium. Double immunostaining with cell type-specific antibodies was carried out to identify cellular sources of bFGF.

RESULTS

Both polypeptide and mRNA for bFGF were detected in the synovial samples examined. Increased bFGF staining was found in synovium-cartilage interface where joint destruction occurred and in hyperplastic synoviocytes of a subset of rheumatoid synovium. Strong cytoplasmic bFGF staining was localized in the majority of mast cells and vascular cells.

CONCLUSIONS

Synovial tissue from patients with RA, DJD, and trauma express bFGF. Increased bFGF staining in the hyperplastic lining synoviocytes and at the pannus-cartilage interface suggests that bFGF may play a role in synovial hyperplasia and joint destruction. Strong cytoplasmic bFGF staining found in mast cells and vascular cells indicates that these cells are the major sources of tissue bFGF.

Apoptosis in the thymus of developing Xenopus laevis

Metamorphosis in Xenopus laevis is a time when thyroxine and glucocorticoid levels rise, dramatic morphological and physiological changes take place, and tolerance is established to newly expressed adult antigens. In vitro exposure of thymocytes tested at different metamorphic stages, to the T-cell lectin, phytohemagglutinin (PHA), stimulates increased apoptosis, but incubation with the synthetic glucocorticoid, dexamethasone (DEX), fails in this regard. Altered-self antigenicity, following trinitrobenzene sulfonic acid (TNBS) treatment, increases apoptosis only in the late stages of metamorphosis. Developmentally blocked metamorphosing larvae demonstrate low thymic apoptotic rates that are also unaffected by in vitro exposure to DEX or by in vivo exposure to thyroxine, but are increased by PHA and in some individuals by TNBS. When released from blockade, their thymic apoptotic rates rise as progress through metamorphosis is renewed. Larval thymic apoptosis is glucocorticocoid- and thyroxine insensitive, but is lectin and altered-self antigen activated, particularly during postclimax stages.

Apoptosis in thymus of adult Xenopus laevis

Thymocyte apoptosis in adult Xenopus laevis is demonstrated on agarose gels and is quantified by propidium iodide incorporation using flow cytometry. Basal apoptotic levels are increased after in vitro exposure to a glucocorticoid, dexamethasone (DEX), and to the lectin, phytohemagglutinin (PHA). To determine the role that newly introduced antigenic determinants may play in this regard, a repertoire of altered-self antigens was created by exposing thymuses in vitro to trinitrobenzene sulfonic acid (TNBS) thereby derivatizing self-cells and proteins via 2,4,6-trinitrophenyl-acetic acid conjugation. An increase in apoptosis in TNBS-treated thymuses is observed. Thus, the thymocytes of adult Xenopus laevis are susceptible to apoptosis when induced by a glucocorticoid, a lectin, and by altered self, antigen activation.