Gypsum-Related Impact on Antibiotic-Loaded Composite Based on Highly Porous Hydroxyapatite-Advantages and Disadvantages

Highly porous hydroxyapatite is sometimes considered toxic and useless as a biomaterial for bone tissue regeneration because of the high adsorption of calcium and phosphate ions from cell culture media. This negatively affects the osteoblast's growth in such ion-deprived media and suggests "false cytotoxicity" of tested hydroxyapatite. In our recent study, we showed that a small addition of calcium sulfate dihydrate (CSD) may compensate for this adsorption without a negative effect on other properties of hydroxyapatite-based biomaterials. This study was designed to verify whether such CSD-supplemented biomaterials may serve as antibiotic carriers. FTIR, roughness, mechanical strength analysis, drug release, hemocompatibility, cytotoxicity against human osteoblasts, and antibacterial activity were evaluated to characterize tested biomaterials. The results showed that the addition of 1.75% gypsum and gentamicin caused short-term calcium ion compensation in media incubated with the composite. The combination of both additives also increased antibacterial activity against bacteria representative of bone infections without affecting osteoblast proliferation, hemocompatibility, and mechanical parameters. Thus, gypsum and antibiotic supplementation may provide advanced functionality for bone-regeneration materials based on hydroxyapatite of a high surface area and increasingly high Ca2+ sorption capacity.

Non-invasive characterization of pancoronary inflammation by computed tomography angiography in patients with recent spontaneous coronary dissection

Background

Spontaneous coronary artery dissection (SCAD) is a non-atherosclerotic cause of myocardial infarction of unclear aethiology. Histopathological analyses have identified increased coronary inflammation in patients with SCAD [1]. Recently the peri-coronary adipose tissue attenuation (PCAT) derived from standard computed tomography angiography (CTA) has been established as a reproducible method for measuring vascular inflammation which enhances risk stratification in patients with coronary atherosclerosis [2].

Purpose

To characterize the pancoronary and vessel-specific inflammation by means of CTA-derived PCAT in patients with recent SCAD compared with individuals without prior SCAD.

Methods

Patients with confirmed SCAD referred to a tertiary center between 2017 and 2021 who underwent CTA as a routine cardiac evaluation were included in this retrospective study. Subjects were matched 1:1 with individuals with no prior SCAD who underwent CTA within the same timespan, using the same scanner and imaging protocol, with coronary arteries free of obstructive disease and similar clinical characteristics (Table 1). PCAT was analyzed on end-diastolic CTA reconstructions with a semi-automated software using standard methodology (Figure 1A) [3]. Proximal 40 mm of all major coronary vessels >2 mm in diameter as well as the SCAD-related vessel were included. The primary outcome was pancoronary PCAT defined as mean PCAT in the right (RCA), left anterior descending (LAD) and circumflex (LCX) artery. Secondary outcome was vessel-specific PCAT defined as PCAT in RCA and averaged PCAT in LAD and LCX (PCAT LCA).

Results

The final cohort comprised 35 patients with recent SCAD (median 6.1 mo. [4.0–16.8] since SCAD, 94.3% female) and 35 patients in the non-SCAD group. Pancoronary PCAT was higher in patients with SCAD compared with non-SCAD group (−80.1 [IQR: −74.5, −84.6] vs. −83.4 HU [−78.7, −88.0], P=0.008) suggestive of increased coronary inflammation. Vessel-specific PCAT was higher for the RCA (−80.7 [−70.4, −86.9] vs. −85.3 [−80.4, −90.6] HU, P<0.001) and borderline higher for the LCA (−79.2 [−73.9, −83.2] vs. −83.4 [−78.0, −88.3] HU, P=0.056) in patients with SCAD compared with non-SCAD respectively (Figure 1B). In patients with SCAD, PCAT in previously dissected vessel was not significantly different from averaged PCAT in unaffected vessels (−78.4 [−73.7, −89.0] vs. −80.9 [−74.9, −83.3], P=0.77; Figure 1C). While PCAT numerically decreased with time since SCAD, the association was not statistically significant when patients were stratified into tertiles according to time from SCAD (Figure 1D).

Conclusions

Patients with recent SCAD have higher pericoronary adipose tissue attenuation compared with non-SCAD patients suggesting increased perivascular inflammatory activity. This association is not restricted to the dissected vessel, nor reflected in routine serum inflammatory analysis and persists over time.

Funding Acknowledgement

Type of funding sources: None.

POS0253 PERSONALIZED RISK EVALUATION FOR OUTCOME PREDICTION IN ANCA ASSOCIATED VASCULITIS (AAV) USING LATENT CLASS ANALYSIS AND MACHINE LEARNING

Background

ANCA associated vasculitides (AAV) are a heterogeneous group of rare diseases with unknown etiology. In the most severe cases AAV can lead to end stage kidney disease or death. Since etiology and detailed pathogenesis of AAV is not known, the prediction of disease outcome at the time of diagnosis is challenging. Thus, there is an unmet need for tools to identify patients with the highest risk of organ dysfunction and death and apply effective personalized therapy.

Objectives

The aim of this work was to search for tools allowing outcome prediction at the time of AAV diagnosis. Early identification of patients, who are likely to develop severe organ dysfunction and death is crucial for appropriate disease management. Induction therapy in AAV relays on immunosuppressive drugs characterized by a high risk of severe side effects. Thus, their administration in high doses should be limited only to individual patients with an especially high risk of poor outcome.

Methods

We applied here two methods of identification of AAV patients at risk to develop severe organ dysfunction and death. First method (latent class analysis [LCA] followed by logistic regression) was meant to subcategorize patients and identify a subgroup at subjects at risk to develop chronic renal replacement therapy (CRRT) and death [1]. Second, served to assess individual poor outcome risk and was based on two machine learning (ML) classifiers, which by analyzing clinical information allow assigning computed risk for CRRT and death in an individual patient allowing to identify subjects with high risk of chronic replacement therapy (CRRT) and death. We have evaluated a number of different approaches to build the ML models (including logistic regression, support vector machines, random forests), and obtained the best results for the gradient boosting algorithm implementation called LightGBM [2]. It works as a sequential ensemble of so-called weak learners (decision trees) finally combined in a one prediction model. Both analyses were based on retrospective data from Polish national AAV registry (POLVAS) [3] including presently 565 GPA and 135 MPA patients. The parameters used were: demographic data and laboratory parameters, specific organ involvement, ANCA specificity and time between selected stages of the disease.

Results

LCA used on our AAV cohort identified four subphenotypes – three already previously proposed - and revealing a fourth clinically relevant subphenotype. This new subphenotype includes only GPA patients, usually diagnosed at a younger age as compared to other groups, and characterized by multiorgan involvement, high relapse rate, relatively high risk of death, but no end-stage kidney disease. Logistic regression analysis revealed significant differences in the risk of CRRT and death between those subphenotypes – the worst prognosis was found for severe MPO AAV. On the other hand, using ML approach we obtained an individual prediction model with potentially relevant clinical performance (ROC AUC of 0.85 for CRRT and 0.82 for death).

Conclusion

We consider results obtained encouraging. They may offer a new insight into AAV course based on data available at diagnosis, and create a solid foundation for potential clinical decision support system.

References

[1]Wójcik K et al. Subphenotypes of ANCA-associated vasculitis identified by latent class analysis. Clin Exp Rheumatol. 2021 Mar-Apr;39 Suppl 129(2):62-68.

[2]Ke G, at al. Light GBM: A Highly Efficient Gradient Boosting Decision Tree. Advances in Neural Information Processing Systems 30 (NIPS 2017), pp. 3149-3157.

[3]Wójcik K et al. Clinical characteristics of Polish patients with ANCA-associated vasculitides-retrospective analysis of POLVAS registry. Clin Rheumatol. 2019 Sep;38(9):2553-2563.

Acknowledgements

This work was supported by a grant from Polish National Science Center UMO-2018/31/B/NZ6/03898

Disclosure of Interests

None declared

Metal TiO2 Nanotube Layers for the Treatment of Dental Implant Infections

Titanium oxide nanotube layers with silver and zinc nanoparticles are attracting increasing attention in the design of bone and dental implants due to their antimicrobial potential and their ability to control host cell adhesion, growth, and differentiation. However, recent reports indicate that the etiology of dental infections is more complex than has been previously considered. Therefore, the antimicrobial potential of dental implants should be evaluated against at least several different microorganisms cooperating in human mouth colonization. In this study, Ag and Zn nanoparticles incorporated into titanium oxide nanotubular layers were studied with regard to how they affect Candida albicans, Candida parapsilosis, and Streptococcus mutans. Layers of titanium oxide nanotubes with an average diameter of 110 nm were fabricated by electrochemical anodization, annealed at 650 °C, and modified with approx. 5 wt % Ag or Zn nanoparticles. The surfaces were examined with the scanning electron microscopy-energy dispersive X-ray analysis, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy techniques and subjected to evaluation of microbial-killing and microbial adhesion-inhibiting potency. In a 1.5 h long adhesion test, the samples were found more effective toward yeast strains than toward S. mutans. In a release-killing test, the microorganisms were almost completely eliminated by the samples, either within 3 h of contact (for S. mutans) or 24 h of contact (for both yeast strains). Although further improvement is advisable, it seems that Ag and Zn nanoparticles incorporated into TiO₂ nanotubular surfaces provide a powerful tool for reducing the incidence of bone implant infections. Their high bidirectional activity (against both Candida species and S. mutans) makes the layers tested particularly promising for the design of dental implants.

Synthesis and in vitro antiproliferative and antibacterial activity of new thiazolidine-2,4-dione derivatives

In our present research, we synthesised new thiazolidine-2,4-diones (12-28). All the newly synthesised compounds were evaluated for antiproliferative and antibacterial activity. Antiproliferative evaluation was carried out using normal human skin fibroblasts and tumour cell lines: A549, HepG2, and MCF-7. The IC₅₀ values were determined for tested compounds revealing antiproliferative activity. Moreover, safety index (SI) was calculated. Among all tested derivatives, the compound 18 revealed the highest antiproliferative activity against human lung, breast, and liver cancer cells. More importantly, the derivative 18 showed meaningfully lower IC₅₀ values when compared to the reference substance, irinotecan, and relatively high SI values. Moreover, newly synthesised compounds were screened for the bacteria growth inhibition in vitro. According to our screening results, most active compound was the derivative 18 against Gram-positive bacteria. Therefore, it may be implied that the novel compound 18 appears to be a very promising agent for anticancer treatment.

Covalent coating of hydroxyapatite by keratin stabilizes gentamicin release

A novel hybrid hydroxyapatite (HAP) matrix, covalently coated with rarely applied, hardly degradable keratin and effectively modified by gentamicin immobilized in mixed-type mode (via interactions of diverse strength), was created. This hybrid showed a remarkably high drug immobilization yield and the most sustainable antibiotic release among all tested composites. It was also able to inhibit bacterial growth, both in surrounding liquid and on matrix surface, much longer (for at least 121 days of experiment) than analogous gelatin-modified and nonmodified matrices. Gentamicin-keratin-coated-HAP granules were nontoxic to human osteoblasts and enabled their proliferation with a rate similar as noncoated HAP. Presence of keratin on HAP granules seemed to slightly enhance the osteoblast proliferation. The results indicate that newly created HAP hybrid with covalently immobilized keratin and gentamicin--nontoxic and osteoblast-friendly--is a promising biomaterial of significantly prolonged antibacterial activity.

The responsiveness of alpha 2-adrenergic receptors in hypothalamus of vasopressin-hypertensive rats

Administration of clonidine produced biphasic changes in the type II inhibitor activity (endogenous inhibitor of protein kinases which specifically regulates phosphorylation mediated by cGMP-dependent system). Small doses of clonidine (10-50 micrograms/kg) produced an increase while large doses (200-1000 micrograms/kg) induced a decrease in the type II inhibitor activity. The both actions of clonidine were greatly reduced in vasopressin hypertensive rats suggesting subsensitivity of alpha 2-adrenergic receptors. Subsensitivity of postsynaptic alpha 2-receptors was also observed in anterior hypothalamus in in vitro experiments. Incubation of anterior and posterior hypothalamic slices with clonidine resulted in concentration-dependent increase in cGMP content and a decrease in the type II inhibitor activity. The clonidine action in anterior hypothalamus of vasopressin-hypertensive rats was greatly reduced. In contrast, the clonidine action in posterior hypothalamus was the same in vasopressin-hypertensive as in the control rats.

The responsiveness of the endogenous inhibitor of cAMP-dependent protein kinase to apomorphine in rat striatum after prolonged treatment with nomifensin

Apomorphine produced biphasic changes in the activity of an endogenous, specific inhibitor of cAMP-dependent protein kinase (type I inhibitor). Small doses of apomorphine (50-100 micrograms/kg) induced an increase while high doses (1-10 mg/kg) produced a dose-dependent decrease of the type I inhibitor activity in the striatum of control rats. Prolonged treatment with nomifensin markedly reduced the response of the type I inhibitor both to low and high doses of apomorphine and shifted the dose-response curves to the right. The apomorphine-induced increase of the type I inhibitor activity in nomifensin-pretreated rats was blocked by aminophylline and by small, presynaptically active doses of haloperidol. This suggests that small doses of apomorphine stimulate presynaptic D2 receptor. The apomorphine-induced decrease of the type I inhibitor activity in nomifensin pretreated animals was enhanced by aminophylline and by presynaptically active dose of haloperidol. In contrast, this action of apomorphine was blocked by high, postsynaptically active, dose of haloperidol. It suggested postsynaptic site of action of high doses of apomorphine. Prolonged pretreatment with nomifensin resulted in subsensitivity of both presynaptic D2 and postsynaptic D1 receptors.