Krzysztof Jasiński

Magnetic Resonance Microscopy for Assessment of Morphological Changes in Hydrating Hydroxypropylmethyl Cellulose Matrix Tablets In Situ

ABSTRACTPurposeTo resolve contradictions found in morphology of hydrating hydroxypropylmethyl cellulose (HPMC) matrix as studied using Magnetic Resonance Imaging (MRI) techniques. Until now, two approaches were used in the literature: either two or three regions that differ in physicochemical properties were identified.MethodsMultiparametric, spatially and temporally resolved T2 MR relaxometry in situ was applied to study the hydration progress in HPMC matrix tablets using a 11.7 T MRI system. Two spin-echo based pulse sequences—one of them designed to specifically study short T2 signals—were used.ResultsTwo components in the T2 decay envelope were estimated and spatial distributions of their parameters, i.e. amplitudes and T2 values, were obtained. Based on the data, five different regions and their temporal evolution were identified: dry glassy, hydrated solid like, two interface layers and gel layer. The regions were found to be separated by four evolving fronts identified as penetration, full hydration, total gelification and apparent erosion.ConclusionsThe MRI results showed morphological details of the hydrating HPMC matrices matching compound theoretical models. The proposed method will allow for adequate evaluation of controlled release polymeric matrix systems loaded with drug substances of different solubility.

A volume microstrip RF coil for MRI microscopy.

Quantitative magnetic resonance imaging (MRI) studies of small samples such as a single cell or cell clusters require application of radiofrequency (RF) coils that provide homogenous B(1) field distribution and high signal-to-noise ratio (SNR). We present a novel design of an MRI RF volume microcoil based on a microstrip structure. The coil consists of two parallel microstrip elements conducting RF currents in the opposite directions, thus creating homogenous RF field within the space between the microstrips. The construction of the microcoil is simple, efficient and cost-effective. Theoretical calculations and finite element method simulations were used to optimize the coil geometry to achieve optimal B(1) and SNR distributions within the sample and predict parameters of the coil. The theoretical calculations were confirmed with MR images of a 1-mm-diameter capillary and a plant obtained with the double microstrip RF microcoil at 11.7 T. The in-plane resolution of MR images was 24 μm × 24 μm.

Retrospectively gated MRI for in vivo assessment of endothelium-dependent vasodilatation and endothelial permeability in murine models of endothelial dysfunction

Endothelial dysfunction is linked to impaired endothelial‐dependent vasodilatation and permeability changes. Here, we quantify both of these phenomena associated with endothelial dysfunction by MRI in vivo in mice.

MRI-based assessment of endothelial function in mice in vivo

While a healthy endothelium serves to maintain vascular haemostasis, a malfunctioning endothelium leads to various cardiovascular diseases, including atherothrombosis. Endothelial dysfunction is characterized by increased vascular permeability, impaired endothelium-dependent responses and various pro-inflammatory and pro-thrombotic changes in endothelial phenotype, all of which could provide the basis for an in vivo diagnosis of endothelial dysfunction. In the present review, we briefly summarize the magnetic resonance imaging (MRI)-based methods available for assessing endothelial function in animal models, especially in mice. These methods are aimed to assess biochemical phenotype using molecular imaging, endothelium-dependent responses or changes in endothelial permeability. All these approaches provide a complementary insight into the endothelial dysfunction in vivo and may offer a unique opportunity to study endothelium-based mechanisms of diseases and endothelial response to treatment.

Uptake and bioreactivity of charged chitosan-coated superparamagnetic nanoparticles as promising contrast agents for magnetic resonance imaging

Bioreactivity of superparamagnetic iron oxide nanoparticles (SPION) coated with thin layers of either cationic or anionic chitosan derivatives and serving as contrast agents in magnetic resonance imaging (MRI) was studied in vivo using BALB/c mouse model. Synthesized dual-modal fluorescing SPION were tracked in time using both fluorescent imaging and MRI. Although SPION started to be excreted by kidneys relatively shortly after administration they were uptaken by liver enhancing MRI contrast even up to 7 days. Importantly, chitosan-coated SPION caused only mild activation of acute phase response not affecting biochemical parameters of blood. Liver histology indicated the presence of SPION and modest increase in the number of Kupffer cells. The overall results indicated that SPION coated with ultrathin layers of chitosan ionic derivatives can serve as T2 contrast agents for diagnosis of liver diseases or imaging of other organs assuming the dose is optimized according to the need.

Functional and Biochemical Endothelial Profiling In Vivo in a Murine Model of Endothelial Dysfunction; Comparison of Effects of 1-Methylnicotinamide and Angiotensin-converting Enzyme Inhibitor

Although it is known that 1-methylnicotinamide (MNA) displays vasoprotective activity in mice, as yet the effect of MNA on endothelial function has not been demonstrated in vivo. Here, using magnetic resonance imaging (MRI) we profile the effects of MNA on endothelial phenotype in mice with atherosclerosis (ApoE/LDLR-/-) in vivo, in comparison to angiotensin (Ang) -converting enzyme (ACE) inhibitor (perindopril), with known vasoprotective activity. On a biochemical level, we analyzed whether MNA- or perindopril-induced improvement in endothelial function results in changes in ACE/Ang II-ACE2/Ang-(1–7) balance, and L-arginine/asymmetric dimethylarginine (ADMA) ratio. Endothelial function and permeability were evaluated in the brachiocephalic artery (BCA) in 4-month-old ApoE/LDLR-/- mice that were non-treated or treated for 1 month or 2 months with either MNA (100 mg/kg/day) or perindopril (10 mg/kg/day). The 3D IntraGate®FLASH sequence was used for evaluation of BCA volume changes following acetylcholine (Ach) administration, and for relaxation time (T1) mapping around BCA to assess endothelial permeability using an intravascular contrast agent. Activity of ACE/Ang II and ACE2/Ang-(1–7) pathways as well as metabolites of L-arginine/ADMA pathway were measured using liquid chromatography/mass spectrometry-based methods. In non-treated 6-month-old ApoE/LDLR-/- mice, Ach induced a vasoconstriction in BCA that amounted to –7.2%. 2-month treatment with either MNA or perindopril resulted in the reversal of impaired Ach-induced response to vasodilatation (4.5 and 5.5%, respectively) and a decrease in endothelial permeability (by about 60% for MNA-, as well as perindopril-treated mice). Improvement of endothelial function by MNA and perindopril was in both cases associated with the activation of ACE2/Ang-(1–7) and the inhibition of ACE/Ang II axes as evidenced by an approximately twofold increase in Ang-(1–9) and Ang-(1–7) and a proportional decrease in Ang II and its active metabolites. Finally, MNA and perindopril treatment resulted in an increase in L-arginine/ADMA ratio by 107% (MNA) and 140% (perindopril), as compared to non-treated mice. Functional and biochemical endothelial profiling in ApoE/LDLR-/- mice in vivo revealed that 2-month treatment with MNA (100 mg/kg/day) displayed a similar profile of vasoprotective effect as 2-month treatment with perindopril (10 mg/kg/day): i.e., the improvement in endothelial function that was associated with the beneficial changes in ACE/Ang II-ACE2/Ang (1–7) balance and in L-arginine/ADMA ratio in plasma.

Comprehensive MRI for the detection of subtle alterations in diastolic cardiac function in apoE/LDLR(-/-) mice with advanced atherosclerosis.

ApoE/LDLR–/– mice represent a reliable model of atherosclerosis. However, it is not clear whether cardiac performance is impaired in this murine model of atherosclerosis. Here, we used MRI to characterize cardiac performance in vivo in apoE/LDLR–/– mice with advanced atherosclerosis. Six‐month‐old apoE/LDLR–/– mice and age‐matched C57BL/6J mice (control) were examined using highly time‐resolved cine‐MRI [whole‐chamber left ventricle (LV) imaging] and MR tagging (three slices: basal, mid‐cavity and apical). Global and regional measures of cardiac function included LV volumes, kinetics, time‐dependent parameters, strains and rotations. Histological analysis was performed using OMSB (orceine with Martius, Scarlet and Blue) and ORO (oil red‐O) staining to demonstrate the presence of advanced coronary atherosclerosis. MR‐tagging‐based strain analysis in apoE/LDLR–/– mice revealed an increased frequency of radial and circumferential systolic stretch (25% and 50% of segments, respectively, p ≤ 0.012), increased radial post‐systolic strain index (45% of segments, p = 0.009) and decreased LV untwisting rate (−30.3° (11.6°)/cycle, p = 0.004) when compared with control mice. Maximal strains and LV twist were unchanged. Most of the cine‐MRI‐based LV functional and anatomical parameters also remained unchanged in apoE/LDLR–/–mice, with only a lower filling rate, longer filling time, shorter isovolumetric contraction time and slower heart rate observed in comparison with control mice. The coronary arteries displayed severe atherosclerosis, as evidenced by histological analysis. Using comprehensive MRI methods, we have demonstrated that, despite severe coronary atherosclerosis in six‐month‐old apoE/LDLR–/– mice, cardiac performance including global parameters, twist and strains, was well preserved. Only subtle diastolic alterations, possibly of ischemic background, were uncovered. Copyright

Activation pattern of ACE2/Ang-(1-7) and ACE/Ang II pathway in course of heart failure assessed by multiparametric MRI in vivo in Tgαq*44 mice

Here, we analyzed systemic (plasma) and local (heart/aorta) changes in ACE/ACE-2 balance in Tgαq*44 mice in course of heart failure (HF). Tgαq*44 mice with cardiomyocyte-specific Gαq overexpression and late onset of HF were analyzed at different age for angiotensin pattern in plasma, heart, and aorta using liquid chromatography/mass spectrometry, for progression of HF by in vivo magnetic resonance imaging under isoflurane anesthesia, and for physical activity by voluntary wheel running. Six-month-old Tgαq*44 mice displayed decreased ventricle radial strains and impaired left atrial function. At 8-10 mo, Tgαq*44 mice showed impaired systolic performance and reduced voluntary wheel running but exhibited preserved inotropic reserve. At 12 mo, Tgαq*44 mice demonstrated a severe impairment of basal cardiac performance and modestly compromised inotropic reserve with reduced voluntary wheel running. Angiotensin analysis in plasma revealed an increase in concentration of angiotensin-(1-7) in 6- to 10-mo-old Tgαq*44 mice. However, in 12- to 14-mo-old Tgαq*44 mice, increased angiotensin II was noted with a concomitant increase in Ang III, Ang IV, angiotensin A, and angiotensin-(1-10). The pattern of changes in the heart and aorta was also compatible with activation of ACE2, followed by activation of the ACE pathway. In conclusion, mice with cardiomyocyte Gαq protein overexpression develop HF that is associated with activation of the systemic and the local ACE/Ang II pathway. However, it is counterbalanced by a prominent ACE2/Ang-(1-7) activation, possibly allowing to delay decompensation. NEW & NOTEWORTHY Changes in ACE/ACE-2 balance were analyzed based on measurements of a panel of nine angiotensins in plasma, heart, and aorta of Tgαq*44 mice in relation to progression of heart failure (HF) characterized by multiparametric MRI and exercise performance. The early stage of HF was associated with upregulation of the ACE2/angiotensin-(1-7) pathway, whereas the end-stage HF was associated with downregulation of ACE2/angiotensin-(1-7) and upregulation of the ACE/Ang II pathway. ACE/ACE-2 balance seems to determine the decompensation of HF in this model.

Novel nanostructural contrast for magnetic resonance imaging of endothelial inflammation: targeting SPIONs to vascular endothelium

This study aimed to develop superparamagnetic iron oxide nanoparticles (SPIONs) targeted to the areas of vascular endothelium changed in the initial inflammation process, a first step of numerous cardiovascular diseases. Iron oxide nanoparticles coated with a cationic derivative of chitosan (CCh) and having attached monoclonal antibodies (anti VCAM-1 and anti P-selectin) were successfully prepared. Owing to electrostatic stabilization, they form a stable colloidal dispersion in aqueous media. The superparamagnetic properties of the resulting SPION-CCh-anti-VCAM-1 maghemite nanoparticles were proved by magnetometric and Mossbauer measurements. In vitro studies confirmed the specific interaction of anti-VCAM-1 antibodies bound to the surface of SPIONs with endothelial cells of aorta of db/db mice, known to display endothelial inflammation associated with diabetes. The nanoparticles obtained were also visualized using MRI in the aortic arch of ApoE/LDLR−/− mice displaying endothelial inflammation associated with atherosclerosis.

Cerebrovascular reactivity and cerebral perfusion of rats with acute liver failure: role of L-glutamine and asymmetric dimethylarginine in L-arginine-induced response

Cerebral blood flow (CBF) is impaired in acute liver failure (ALF), however, the complexity of the underlying mechanisms has often led to inconclusive interpretations. Regulation of CBF depends at least partially on variations in the local brain L‐arginine concentration and/or its metabolic rate. In ALF, other factors, like an increased concentration of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor and elevated level of L‐glutamine, may contribute to CBF alteration. This study demonstrated strong differences in the reactivity of the middle cerebral arteries and their response to extravascular L‐arginine application between vessels isolated from rats with thioacetamide (TAA)‐induced ALF and control animals. Our results also showed the decrease in the cerebral perfusion in TAA rats measured by arterial spin labeling perfusion magnetic resonance. Subsequently, we aimed to investigate the importance of balance between the concentration of ADMA and L‐arginine in the CBF regulation. In vivo, intraperitoneal L‐arginine administration in TAA rats corrected: (i) decrease in cerebral perfusion, (ii) decrease in brain extracellular L‐arginine/ADMA ratio and (iii) increase in brain L‐glutamine concentration. Our study implicates that impaired vascular tone of cerebral arteries is most likely associated with exposure to high ADMA and L‐glutamine levels resulting in limited availability of L‐arginine and might be responsible for reduced cerebral perfusion observed in ALF.