The pathology of the foreign body reaction against biomaterials

The healing process after implantation of biomaterials involves the interaction of many contributing factors. Besides their in vivo functionality, biomaterials also require characteristics that allow their integration into the designated tissue without eliciting an overshooting foreign body reaction (FBR). The targeted design of biomaterials with these features, thus, needs understanding of the molecular mechanisms of the FBR. Much effort has been put into research on the interaction of engineered materials and the host tissue. This elucidated many aspects of the five FBR phases, that is protein adsorption, acute inflammation, chronic inflammation, foreign body giant cell formation, and fibrous capsule formation. However, in practice, it is still difficult to predict the response against a newly designed biomaterial purely based on the knowledge of its physical-chemical surface features. This insufficient knowledge leads to a high number of factors potentially influencing the FBR, which have to be analyzed in complex animal experiments including appropriate data-based sample sizes. This review is focused on the current knowledge on the general mechanisms of the FBR against biomaterials and the influence of biomaterial surface topography and chemical and physical features on the quality and quantity of the reaction. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 927-940, 2017.

Hypoxic regulation of inducible nitric oxide synthase via hypoxia inducible factor-1 in cardiac myocytes

The relationship between hypoxia and regulation of nitric oxide synthase (NOS) in myocardial tissue is not well understood. We investigated the role of hypoxia inducible factor-1 (HIF-1) on expression of the inducible NOS (iNOS) in myocardial cells in vivo and in vitro. In situ hybridization in myocardial tissue from rats exposed to hypoxia for 3 weeks demonstrated increased iNOS mRNA expression. Northern analysis of RNA from hearts of those animals and from cells exposed to hypoxia for 12 hours in vitro demonstrated an increase of HIF-1 RNA expression. Electrophoretic mobility shift assays using oligonucleotides containing the iNOS HIF-1 DNA binding site and nuclear extracts from cardiac myocytes showed induction of specific DNA binding in cells subjected to hypoxia. Transient transfection of cardiac myocytes using the murine iNOS promoter resulted in a 3.43-fold increase in promoter activity under hypoxia compared with normoxia. Mutation or deletion of the HIF-1 site eliminated the hypoxic response. As cytokines have been shown to regulate iNOS expression in myocardial cells, cultured neonatal cardiac myocytes were stimulated with interleukin-1beta causing a dramatic induction of iNOS protein expression under normoxia, with further augmentation under hypoxia. Transient transfection of cells stimulated with interleukin-1beta showed an increased iNOS promoter activity under normoxic conditions compared with unstimulated cells, with a further increase in response to hypoxia, which was dependent on HIF-1. These results demonstrate that hypoxia causes an increase in iNOS expression in cardiac myocytes and that HIF-1 is essential for the hypoxic regulation of iNOS gene expression.

Retinal microcirculation in patients with diabetes mellitus: dynamic and morphological analysis of perifoveal capillary network

The new scanning laser technique allows one to quantify the retinal microcirculation. A digital image analysing system was used to study capillary blood flow velocities and morphological parameters of perifoveal intercapillary areas and foveal avascular zones in normal and diabetic subjects. Diabetic patients showed a significant reduction in capillary blood cell velocities in comparison with normal subjects. Perifoveal intercapillary areas and foveal avascular zones were significantly increased in all stages of diabetic retinopathy, and both parameters increased with progressing diabetic retinopathy. Significant changes in the perifoveal intercapillary areas were observed between normal subjects and patients with no retinopathy.

A faecal microbiota signature with high specificity for pancreatic cancer

BACKGROUND

Recent evidence suggests a role for the microbiome in pancreatic ductal adenocarcinoma (PDAC) aetiology and progression.

OBJECTIVE

To explore the faecal and salivary microbiota as potential diagnostic biomarkers.

METHODS

We applied shotgun metagenomic and 16S rRNA amplicon sequencing to samples from a Spanish case-control study (n=136), including 57 cases, 50 controls, and 29 patients with chronic pancreatitis in the discovery phase, and from a German case-control study (n=76), in the validation phase.

RESULTS

Faecal metagenomic classifiers performed much better than saliva-based classifiers and identified patients with PDAC with an accuracy of up to 0.84 area under the receiver operating characteristic curve (AUROC) based on a set of 27 microbial species, with consistent accuracy across early and late disease stages. Performance further improved to up to 0.94 AUROC when we combined our microbiome-based predictions with serum levels of carbohydrate antigen (CA) 19-9, the only current non-invasive, Food and Drug Administration approved, low specificity PDAC diagnostic biomarker. Furthermore, a microbiota-based classification model confined to PDAC-enriched species was highly disease-specific when validated against 25 publicly available metagenomic study populations for various health conditions (n=5792). Both microbiome-based models had a high prediction accuracy on a German validation population (n=76). Several faecal PDAC marker species were detectable in pancreatic tumour and non-tumour tissue using 16S rRNA sequencing and fluorescence in situ hybridisation.

CONCLUSION

Taken together, our results indicate that non-invasive, robust and specific faecal microbiota-based screening for the early detection of PDAC is feasible.

[Cap image--a new kind of computer-assisted video image analysis system for dynamic capillary microscopy]

We describe a newly developed multi-function video image analysis system for the computer-aided evaluation of capillaroscopic findings in microcirculation research. The Cap image analysis system comprises an IBM-compatible PC with a Matrox image processing card and real-time video tape digitalization. The video recorder is driven by a personal computer to which it is connected via an RS-232 interface. In contrast to currently available systems, the program presented here makes it possible to select any of several integrated image analysis functions, depending on the quality of the video image. Some examples of the analysis functions available are measurements of erythrocyte flow velocity using the line shift diagram method, the spatial correlation method, and the auto flying spot method. The standard features of the new program include a number of special functions and automatic movement correction. The system thus makes it possible not only to measure numerous morphological parameters such as capillary diameter, length, torquation index and capillary density, but also to perform video densitometric analysis, for example using fluorescent dyes.

A universal approach to the expression of human and rabbit cytochrome P450s of the 2C subfamily in Escherichia coli

Human cytochrome P450s 2C8, 2C9, 2C18, and 2C19 and rabbit cytochrome P450s 2C1, 2C2, 2C4, 2C5, and 2C16 were expressed from their respective cDNAs in Escherichia coli as chimeric enzymes in which a portion of the N-terminal membrane anchor sequence was replaced with a modified sequence derived from P450 17A. For 2C1 and 2C2 removal of the extraneous 3'-untranslated sequence allowed the successful expression of constructs that were unproductive in its presence. The levels of expression varied from 180 to 1500 nmol/liter of culture and the addition of delta-aminolevulinic acid to the culture media increased the amount of spectrally detectable P450 for several of these enzymes 2- to 10-fold. The catalytic properties of the modified human 2C P450s expressed in E. coli were concordant with previously published data for several marker substrates including (S)-mephenytoin for P450 2C19, tolbutamide and tetrahydrocannabinol (THC) for P450 2C9, and taxol for P450 2C8. Interestingly, P450 2C19 catalyzed the 21-hydroxylation of progesterone and, to a lesser extent, catalyzed the formation of 16 alpha-hydroxyprogesterone. The rabbit enzyme P450 2C16 catalyzed the formation of 17 alpha- and 16 alpha-hydroxyprogesterone in addition to 21-hydroxylation. P450 2C19 also catalyzed the methylhydroxylation of tolbutamide and the 7-hydroxylation of THC at rates that were similar to or greater than that of P450 2C9. This work has identified important factors required for the high-level expression of 2C subfamily P450s in E. coli. The availability of these enzymes will facilitate detailed kinetic measurements for known and yet to be identified substrates.

Retinal capillary blood flow measurement with a scanning laser ophthalmoscope. Preliminary results

The scanning laser technique in combination with digital image analysis allows direct objective measurement of flow velocities in perimacular capillaries. In addition, the complete macular network of capillaries can be observed. By means of digital frame-to-frame picture analysis of digital recordings, blood flow velocities and morphologic data have been measured. The mean flow velocity in perimacular capillaries observed with the scanning laser ophthalmoscope in healthy subjects (n = 21) amounted to 3.28 +/- 0.45 mm/second. In patients (n = 13) with diabetes mellitus (no or background retinopathy), the mean flow velocity was significantly reduced (2.89 +/- 0.57 mm/seconds) compared with healthy subjects. Morphologic data of the perifoveal capillary bed showed a significant reduction of capillaries in patients with diabetes mellitus when compared with healthy subjects.

Growth factor-induced phosphoinositide 3-OH kinase/Akt phosphorylation in smooth muscle cells: induction of cell proliferation and inhibition of cell death

OBJECTIVE

The signaling pathways mediating proliferation and apoptosis in vascular smooth muscle cells (VSMC) are not well established. It has previously been shown that activation of the phosphoinositide 3-OH kinase (PI3K)/Akt pathway or the ERK 1/2 pathway can mediate anti-apoptotic function in different cell types. This study determined the specific contribution of the PI3K/Akt and ERK pathway in the regulation of apoptosis and proliferation of VSMC.

METHODS AND RESULTS

Incubation of rat VSMC with FCS, insulin or IGF-1 time-dependently stimulated the phosphorylation of Akt, however FCS but not insulin or IGF-1 activated the MAP-kinase ERK 1/2. Moreover, insulin inhibited H(2)O(2)-induced apoptosis via the Akt pathway as demonstrated by pharmacological inhibition of the PI3K or overexpression of a dominant negative Akt mutant. In contrast, FCS inhibited H(2)O(2)-induced apoptosis via the Akt and also the ERK pathway. FCS, but not insulin or IGF-1 induced VSMC proliferation, suggesting that Akt activation is necessary but not sufficient for VSMC proliferation. FCS-induced proliferation of VSMC was only mediated via the Akt pathway and not the ERK pathway.

CONCLUSIONS

These results define a link between cell proliferation and programmed cell death in VSMC via the same signal transduction pathway, namely activation of the serine/threonine kinase Akt, which may have significant implication for the development of vascular diseases or remodeling.

Rat proximal tubule cell line transformed with origin-defective SV40 DNA: autocrine ANG II feedback

The renal proximal tubule (PT) is a major site for a complete tissue renin-angiotensin system (RAS) and produces endogenous angiotensin II (ANG II). The present studies demonstrate autocrine RAS feedback in a line of origin-defective SV40 plasmid transformed immortalized rat PT cells (IRPTC) designated as line 93-p-2-1, which are highly differentiated and express all RAS components. Receptor competition assays and Southern blot following RT-PCR demonstrated that these IRPTC express AT1 and AT2 angiotensin receptor subtypes. Autocrine RAS feedback was examined following exposure to ANG II (10(-8) M), and it was noted that angiotensinogen mRNA increases significantly by 1 h and remains elevated through 24 h. The AT1 blocker losartan prevents this increase. Moreover, ANG II upregulates expression of ANG II receptor mRNA (both AT1 and AT2). Thus the present studies demonstrate positive ANG II feedback with angiotensinogen and ANG II receptors in PTC, suggesting that the main site of such intrarenal feedback in vivo is within PT. ANG II secreted by line 93-p-2-1 is increased by isoproterenol, suggesting beta-adrenergic regulation in IRPTC.

COVID-19 and the endothelium

There is growing evidence that COVID-19 not only affects the lungs but beyond that the endothelial system. Recent studies showed that this can lead to microcirculatory impairments and in consequence to functional disorders of all inner organs. The combination of endothelial dysfunction with a generalized inflammatory state and complement elements may together contribute to the overall pro-coagulative state described in COVID-19 patients leading to venular as well as to arteriolar occlusions.

Video fluorescein angiography: method and clinical application

Video fluorescein angiography, combined with a picture analyzing system, is a clinically applicable, objective method of evaluating the retinal blood-flow parameters. Optical density measurements were performed on videorecordings of fluorescence angiograms by means of a picture-analyzing system in order to determine the circulation parameters of the retina. These included: the arm-retina time (ART), the arteriovenous passage time (AVP), and the mean arterial dye-bolus velocity (MDV). Normal values for these parameters were derived from measurements in 75 healthy volunteers. The mean arm-retina time (ART) was 11.2 +/- 3.3 s, the mean arteriovenous passage time (AVP) 1.45 +/- 0.4 s and the mean arterial dye-bolus velocity (MDV) 6.39 +/- 1.7 mm/s. No significant correlation could be shown between pulse or blood pressure and one of the retinal circulation parameters. A group of ten healthy volunteers was examined twice in order to obtain the intraindividual variation for the measuring parameters. The coefficient of variation for the ART was 18%, 10% for the AVP, and 26% for the MDV.

Leg oedema protection from a buckwheat herb tea in patients with chronic venous insufficiency: a single-centre, randomised, double-blind, placebo-controlled clinical trial

OBJECTIVES

The efficacy of a buckwheat herb tea was determined in patients with chronic venous insufficiency (CVI) in a single-centre, randomised, double-blind, placebo-controlled clinical trial.

METHODS

Sixty-seven male and female patients (22-74 years) with CVI were randomly divided into two groups after a 2-week run-in period. They received either buckwheat herb tea (Fagopyrum esculentum) or a placebo tea for a period of 3 months. The main outcome measure was the lower leg volume determined by ultrasound. Subjective symptoms were assessed by a clinical symptom score system. The femoral vein diameters were measured by B-scan sonography. In a subgroup of patients capillary permeability was determined by cutaneous fluorescence angiography.

RESULTS

Although the mean partial leg volume did not change in the treatment group (from 2041 to 2073 ml), it increased in the placebo group by 110 ml (from 1972 to 2082 ml) according to intent to treat. The difference between the groups was significant. The subjective clinical symptoms were significantly reduced in both groups. The mean diameters of the femoral veins were reduced and capillary permeability was improved, but neither change was statistically significant. No drug-related adverse effects were observed.

CONCLUSION

CVI is a very placebo-sensitive condition. The treatment with buckwheat herb tea is safe and could have a favourable influence on patients with CVI such that further oedema development is prevented.

Effect of garlic on platelet aggregation in patients with increased risk of juvenile ischaemic attack

A platelet-inhibiting effect is described for garlic. In this double-blind, placebo-controlled study on 60 voluntary subjects with cerebrovascular risk factors and constantly increased platelet aggregation it was demonstrated that the daily ingestion of 800 mg of powdered garlic (in the form of coated tablets) over 4 weeks led to a significant inhibition of the pathologically increased ratio of circulating platelet aggregates and of spontaneous platelet aggregation. The ratio of circulating platelet aggregates decreased by 10.3%, from 1.17 +/- 0.08 to 1.05 +/- 0.11 (P < 0.01), and spontaneous platelet aggregation by 56.3%, from 40.7 +/- 23.3 to 17.8 +/- 23.2 degrees (P < 0.01) during the garlic phase. There were no significant changes in the placebo group. The parallel group comparison (garlic versus placebo) revealed a significantly different ratio of circulating platelet aggregates after 4 weeks of treatment (P < 0.05). After the 4-week wash-out phase the values increased again to 1.19 +/- 0.32 and 34.9 +/- 28.7 degrees, reaching the initial values (run-in phase prior to the ingestion of garlic). Since garlic is well tolerated it would be worth testing it in a controlled clinical trial for usefulness in preventing disease manifestations associated with platelet aggregation.

In vivo spin trapping of glyceryl trinitrate-derived nitric oxide in rabbit blood vessels and organs

BACKGROUND

The objectives of this study were (1) to assess glyceryl trinitrate (GTN)-derived nitric oxide (NO) formation in vascular tissues and organs of anesthetized rabbits in vivo, (2) to establish a correlation between tissue NO levels and a biological response, and (3) to verify biotransformation of GTN to NO by cytochrome P-450.

METHODS AND RESULTS

NO was trapped in tissues in vivo as a stable paramagnetic mononitrosyl-iron-diethyldithiocarbamate complex [NOFe(DETC)2]. After removal of the tissues, NO was determined by cryogenic electron spin resonance spectroscopy. NO formation in vitro was assessed by spin trapping and by activation of soluble guanylyl cyclase. The GTN-elicited decrease in coronary perfusion pressure was monitored in isolated, constant-flow perfused rabbit hearts. NO was not detected in control tissues. In GTN-treated rabbits, NO formation was higher in organs than in vascular tissues and higher in venous than in arterial vessels. In isolated hearts, ventricular NO levels and decreases in coronary perfusion pressure achieved by GTN were closely correlated. Purified cytochrome P-450 catalyzed NO formation from GTN in a P-450-NADPH reductase- and NADPH-dependent fashion.

CONCLUSIONS

Since GTN-derived NO formation in myocardial tissue correlates to the GTN-elicited vasodilator response, we conclude that GTN-derived NO detected in vivo correlates with the systemic effects of GTN. Therefore, the higher rate of NO formation detected in veins compared with arteries explains the preferential venodilator activity of GTN. High NO formation in cytochrome P-450-rich organs in vivo and efficient NO formation from GTN by cytochrome P-450 in vitro highlights the importance of this pathway for NO formation from GTN in the intact organism.

Contrast enhanced ultrasonography (CEUS) to detect abdominal microcirculatory disorders in severe cases of COVID-19 infection: First experience

In the hands of experienced examiners, the contrast enhanced sonography (CEUS) offers the possibility to analyze dynamic microcirculatory disturbances in real time dynamically without any risk for kidneys and thyroid gland even in severe progressing disease bedside. Based on severe COVID-19 infections, first experiences with abdominal CEUS examinations are presented. In the stage of an imminent organ failure with significantly reduced kidney and liver function, CEUS can be used to show a narrowing of the organ-supplying arteries, as well as a delayed capillary filling of vessels near the capsule, a regional reduced parenchymal perfusion or an inflammatory hyperemia with capillary hypercirculation. It is possible to quickly rule out organ infarction and to dynamically record the mesenteric arterial and venous blood flow.

Effects of garlic coated tablets in peripheral arterial occlusive disease

For the first time, a weak clinical efficacy of a 12-week therapy with garlic powder (daily dose, 800 mg) is demonstrated in patients with peripheral arterial occlusive disease stage II. The increase in walking distance in the verum group by 46 m (from 161.0 +/- 65.1 to 207.1 +/- 85.0 m) was significantly higher (P < 0.05) than in the placebo group (by 31 m, from 172.0 +/- 60.9 to 203.1 +/- 72.8). Both groups received physical therapy twice a week. The diastolic blood pressure, spontaneous thrombocyte aggregation, plasma viscosity, and cholesterol concentration also decreased significantly. Body weight was maintained. It is quite interesting that the garlic-specific increase in walking distance did not appear to occur until the 5th week of treatment, connected with a simultaneous decrease in spontaneous thrombocyte aggregation. Therefore, garlic may be an appropriate agent especially for the long-term treatment of an incipient intermittent claudication.

Evaluation of quantitative contrast harmonic imaging to assess malignancy of liver tumors: A prospective controlled two-center study

AIM: To establish the extent to which contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics facilitates the detection of hepatic tumors.

METHODS: One hundred patients with histologically confirmed malignant or benign hepatic tumor (maximum size 5 cm) were analyzed. Contrast-enhanced ultrasound (bolus injection 2.5 mL SonoVue) was carried out with intermittent breath-holding technique using a multifrequency transducer (2.5-4 MHz). Native vascularization was analyzed with power Doppler. The contrast-enhanced dynamic ultrasound investigation was carried out with contrast harmonic imaging in true detection mode during the arterial, portal venous and late phases. Mechanical index was set at 0.15. Perfusion analysis was performed by post-processing of the raw data [time intensity curve (TIC) analysis]. The cut-off of the gray value differences between tumor and normal liver tissue was established using Receiver Operating Characteristic (ROC) analysis 64-line multi-slice computed tomography served as reference method in all cases. Magnetic resonance tomography was used additionally in 19 cases.

RESULTS: One hundred patients with 59 malignant (43 colon, 5 breast, 2 endocrine metastases, 7 hepatocellular carcinomas and 2 kidney cancers) and 41 benign (15 hemangiomas, 7 focal nodular hyperplasias, 5 complicated cysts, 2 abscesses and 12 circumscribed fatty changes) tumors were included. The late venous phase proved to be the most sensitive for classification of the tumor type. Fifty-eight of the 59 malignant tumors were classified as true positive, and one as false negative. This resulted in a sensitivity of 98.3%. Of the 41 benign tumors, 37 were classified as true negative and 4 as false negative, which corresponds to a specificity of 90.2%. Altogether, 95.0% of the diagnoses were classified as correct on the basis of the histological classification. No investigator-dependency (P = 0.23) was noted.

CONCLUSION: The results show the possibility of accurate prediction of malignancy of hepatic tumors with a positive prognostic value of 93.5% using advanced contrast-enhanced ultrasound. Contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics is a valuable tool to discriminate hepatic tumors.

Treatment strategies for atrial fibrillation

Atrial fibrillation is the most common arrhythmia observed in clinical practice, occurring in 0.4% of the general population and in up to 4% of people greater than 60 years old. It is often associated with other cardiovascular disorders, such as hypertension, coronary artery disease, or cardiomyopathy. Critical evaluation and management of patients with atrial fibrillation requires knowledge of etiology, prognosis, and treatment options of this arrhythmia. On initial presentation, emergency electrical cardioversion should be performed if the patient is hemodynamically unstable. If the patient is stable, initial rate control is recommended, using atrioventricular nodal blocking agents. Further treatment mainly depends upon the duration of the episode. Patients who are in atrial fibrillation <48 hours can be safely cardioverted. Patients who are in atrial fibrillation for >48 hours are commonly anticoagulated for 3 to 4 weeks before and after cardioversion because of the risk of thromboembolism formation in the left atrial appendage. An alternate strategy, which is especially attractive when immediate cardioversion is desired, is transesophageal echocardiography to exclude left atrial thrombus followed by prompt cardioversion. After cardioversion, sinus rhythm can be maintained with class I and III drugs, such as flecainide and propafenone or amiodarone and sotalol. New treatment options, such as atrial defibrillation, atrioventricular junctional ablation, or modification of atrial pacing to prevent atrial fibrillation, are currently under investigation. Although atrial fibrillation is so common in clinical practice, it still remains difficult to treat. Conversion and maintenance to sinus rhythm with antiarrhythmic drug therapy has not shown any improvement in mortality, and some patients may benefit more from ventricular rate control. This review article discusses different treatment strategies for patients with atrial fibrillation.

Quantification of characteristic blood-flow parameters in the vessels of the retina with a picture analysis system for video-fluorescence angiograms: initial findings

Fluorescence angiograms of the retina were performed on 12 healthy, adult subjects between the ages of 20 and 52 years with a 30 degrees fundus camera (C. Zeiss), a low-light TV camera and a video recorder. Characteristic blood-flow parameters for the retina were obtained from the video recording using the picture-analysis system (Mikrovideomat 3, C. Zeiss). These included: the arm-retina time (ART), the arteriovenous passage time (AVP) and the arterial contrast-medium velocity (ACMV). Normal values for these parameters were derived for the four retinal quadrants and then discussed. In addition, the filling characteristics of venules were measured and discussed.

Identification of amino acid substitutions that confer a high affinity for sulfaphenazole binding and a high catalytic efficiency for warfarin metabolism to P450 2C19

Human cytochrome P450s 2C9 and 2C19 metabolize many important drugs including tolbutamide, phenytoin, and (S)-warfarin. Although they differ at only 43 of 490 amino acids, sulfaphenazole (SFZ) is a potent and selective inhibitor of P450 2C9 with an IC50 and a spectrally determined binding constant, KS, of <1 microM. P450 2C19 is not affected by SFZ at concentrations up to 100 microM. A panel of CYP2C9/2C19 chimeric proteins was constructed in order to identify the sequence differences that underlie this difference in SFZ binding. Replacement of amino acids 227-338 in 2C19 with the corresponding region of 2C9 resulted in high-affinity SFZ binding (KS approximately 4 microM) that was not seen when a shorter fragment of 2C9 was substituted (227-282). However, replacement of amino acids 283-338 resulted in extremely low holoenzyme expression levels in Escherichia coli, indicating protein instability. A single mutation, E241K, which homology modeling indicated would restore a favorable charge pair interaction between K241 in helix G and E288 in helix I, led to successful expression of this chimera that exhibited a KS < 10 microM for SFZ. Systematic replacement of the remaining differing amino acids revealed that two amino acid substitutions in 2C19 (N286S, I289N) confer high-affinity SFZ binding (KS < 5 microM). When combined with a third substitution, E241K, the resulting 2C19 triple mutant exhibited a high cataltyic efficiency for warfarin metabolism with the relaxed stereo- and regiospecificity of 2C19 and a lower KM for (S)-warfarin metabolism (<10 microM) typical of 2C9.