L-Wnk1 Deletion in Smooth Muscle Cells Causes Aortitis and Inflammatory Shift.

BACKGROUND: The long isoform of the Wnk1 (with-no-lysine [K] kinase 1) is a ubiquitous serine/threonine kinase, but its role in vascular smooth muscle cells (VSMCs) pathophysiology remains unknown. METHODS: AngII (angiotensin II) was infused in Apoe-/- to induce experimental aortic aneurysm. Mice carrying an Sm22-Cre allele were cross-bred with mice carrying a floxed Wnk1 allele to specifically investigate the functional role of Wnk1 in VSMCs. RESULTS: Single-cell RNA-sequencing of the aneurysmal abdominal aorta from AngII-infused Apoe-/- mice revealed that VSMCs that did not express Wnk1 showed lower expression of contractile phenotype markers and increased inflammatory activity. Interestingly, WNK1 gene expression in VSMCs was decreased in human abdominal aortic aneurysm. Wnk1-deficient VSMCs lost their contractile function and exhibited a proinflammatory phenotype, characterized by the production of matrix metalloproteases, as well as cytokines and chemokines, which contributed to local accumulation of inflammatory macrophages, Ly6Chi monocytes, and γδ T cells. Sm22Cre+Wnk1lox/lox mice spontaneously developed aortitis in the infrarenal abdominal aorta, which extended to the thoracic area over time without any negative effect on long-term survival. AngII infusion in Sm22Cre+Wnk1lox/lox mice aggravated the aortic disease, with the formation of lethal abdominal aortic aneurysms. Pharmacological blockade of γδ T-cell recruitment using neutralizing anti-CXCL9 (anti-CXC motif chemokine ligand 9) antibody treatment, or of monocyte/macrophage using Ki20227, a selective inhibitor of CSF1 receptor, attenuated aortitis. Wnk1 deletion in VSMCs led to aortic wall remodeling with destruction of elastin layers, increased collagen content, and enhanced local TGF-ß (transforming growth factor-beta) 1 expression. Finally, in vivo TGF-ß blockade using neutralizing anti-TGF-ß antibody promoted saccular aneurysm formation and aorta rupture in Sm22 Cre+ Wnk1lox/lox mice but not in control animals. CONCLUSION: Wnk1 is a key regulator of VSMC function. Wnk1 deletion promotes VSMC phenotype switch toward a pathogenic proinflammatory phenotype, orchestrating deleterious vascular remodeling and spontaneous severe aortitis in mice.

Endothelial S1P1 Signaling Counteracts Infarct Expansion in Ischemic Stroke.

RATIONALE: Cerebrovascular function is critical for brain health, and endogenous vascular protective pathways may provide therapeutic targets for neurological disorders. S1P (Sphingosine 1-phosphate) signaling coordinates vascular functions in other organs, and S1P1 (S1P receptor-1) modulators including fingolimod show promise for the treatment of ischemic and hemorrhagic stroke. However, S1P1 also coordinates lymphocyte trafficking, and lymphocytes are currently viewed as the principal therapeutic target for S1P1 modulation in stroke. OBJECTIVE: To address roles and mechanisms of engagement of endothelial cell S1P1 in the naive and ischemic brain and its potential as a target for cerebrovascular therapy. METHODS AND RESULTS: Using spatial modulation of S1P provision and signaling, we demonstrate a critical vascular protective role for endothelial S1P1 in the mouse brain. With an S1P1 signaling reporter, we reveal that abluminal polarization shields S1P1 from circulating endogenous and synthetic ligands after maturation of the blood-neural barrier, restricting homeostatic signaling to a subset of arteriolar endothelial cells. S1P1 signaling sustains hallmark endothelial functions in the naive brain and expands during ischemia by engagement of cell-autonomous S1P provision. Disrupting this pathway by endothelial cell-selective deficiency in S1P production, export, or the S1P1 receptor substantially exacerbates brain injury in permanent and transient models of ischemic stroke. By contrast, profound lymphopenia induced by loss of lymphocyte S1P1 provides modest protection only in the context of reperfusion. In the ischemic brain, endothelial cell S1P1 supports blood-brain barrier function, microvascular patency, and the rerouting of blood to hypoperfused brain tissue through collateral anastomoses. Boosting these functions by supplemental pharmacological engagement of the endothelial receptor pool with a blood-brain barrier penetrating S1P1-selective agonist can further reduce cortical infarct expansion in a therapeutically relevant time frame and independent of reperfusion. CONCLUSIONS: This study provides genetic evidence to support a pivotal role for the endothelium in maintaining perfusion and microvascular patency in the ischemic penumbra that is coordinated by S1P signaling and can be harnessed for neuroprotection with blood-brain barrier-penetrating S1P1 agonists.

Nanohybrids with Magnetic and Persistent Luminescence Properties for Cell Labeling, Tracking, In Vivo Real-Time Imaging, and Magnetic Vectorization.

Once injected into a living organism, cells diffuse or migrate around the initial injection point and become impossible to be visualized and tracked in vivo. The present work concerns the development of a new technique for therapeutic cell labeling and subsequent in vivo visualization and magnetic retention. It is hypothesized and subsequently demonstrated that nanohybrids made of persistent luminescence nanoparticles and ultrasmall superparamagnetic iron oxide nanoparticles incorporated into a silica matrix can be used as an effective nanoplatform to label therapeutic cells in a nontoxic way in order to dynamically track them in real-time in vitro and in living mice. As a proof-of-concept, it is shown that once injected, these labeled cells can be visualized and attracted in vivo using a magnet. This first step suggests that these nanohybrids represent efficient multifunctional nanoprobes for further imaging guided cell therapies development.

Assessment of Placental Perfusion in the Preeclampsia L-NAME Rat Model with High-Field Dynamic Contrast-Enhanced MRI.

PURPOSE: To evaluate placental function and perfusion in a rat model of preeclampsia infused with L-nitro-arginine methyl ester (L-NAME) by dynamic contrast-enhanced (DCE) MRI using gadolinium chelates. METHODS: Pregnant female Sprague-Dawley rats were fitted on embryonic day 16 (E16) with subcutaneous osmotic minipumps loaded to deliver, continuously, L-NAME (50 mg/day per rat; case group) or saline solution (control group). DCE MRI was performed on E19 using gadolinium chelates and a 4.7-T MRI apparatus for small animals. Quantitative analysis was performed using an image software program: placental blood flow (perfusion in mL/min/100 mL of placenta) and fractional volume of the maternal vascular placental compartment (ratio between the placental blood volume and the placental volume, Vb in %) were calculated by compartmental analysis. RESULTS: A total of 176 placentas (27 rats) were analyzed by DCE MRI (97 cases and 79 controls). The model was effective, inducing intrauterine growth retardation, as there was a significant difference between the two groups for placental weight (p < 0.01), fetal weight (p = 0.019), and fetal length (p < 0.01). There was no significant difference in placental perfusion between the L-NAME and control groups (140.1 ± 74.1 vs. 148.9 ± 97.4, respectively; p = 0.496). There was a significant difference between the L-NAME and control groups for Vb (53 ± 12.9 vs. 46.7 ± 9%, respectively; p < 0.01). CONCLUSION: In the L-NAME preeclampsia model, placental perfusion is normal and the fractional blood volume is increased, suggesting that preeclampsia is not always expressed as a result of decreased placental perfusion. This highlights the usefulness of MRI for investigating the physiopathology of preeclampsia.

RODES software for dose assessment of rats and mice contaminated with radionuclides.

In order to support animal experiments of chronic radionuclides intake with realistic dosimetry, voxel-based three-dimensional computer models of mice and rats of both sexes and three ages were built from magnetic resonance imaging. Radiation transport of mono-energetic photons of 11 energies and electrons of 7 energies was simulated with MCNPX 2.6c to assess specific absorbed fractions (SAFs) of energy emitted from 13 source regions and absorbed in 28 target regions. RODES software was developed to combine SAF with radiation emission spectra and user-supplied biokinetic data to calculate organ absorbed doses per nuclear transformation of radionuclides in source regions (S-factors) and for specific animal experiments with radionuclides. This article presents the design of RODES software including the simulation of the particles in the created rodent voxel phantoms. SAF and S-factor values were compared favourably with published results from similar studies. The results are discussed for rodents of different ages and sexes.

Design, Properties, and In Vivo Behavior of Super-paramagnetic Persistent Luminescence Nanohybrids.

With the fast development of noninvasive diagnosis, the design of multimodal imaging probes has become a promising challenge. If many monofunctional nanocarriers have already proven their efficiency, only few multifunctional nanoprobes have been able to combine the advantages of diverse imaging modalities. An innovative nanoprobe called mesoporous persistent luminescence magnetic nanohybrids (MPNHs) is described that shows both optical and magnetic resonance imaging (MRI) properties intended for in vivo multimodal imaging in small animals. MPNHs are based on the assembly of chromium-doped zinc gallate oxide and ultrasmall superparamagnetic iron oxide nanoparticles embedded in a mesoporous silica shell. MPNHs combine the optical advantages of persistent luminescence, such as real time imaging with highly sensitive and photostable detection, and MRI negative contrast properties that ensure in vivo imaging with rather high spatial resolution. In addition to their imaging capabilities, these MPNHs can be motioned in vitro with a magnet, which opens multiple perspectives in magnetic vectorization and cell therapy research.

Multiparametric optical and MR imaging demonstrate inhibition of tumor angiogenesis natural history by mural cell therapy.

PURPOSE: To determine whether functional imaging using MRI and fibered confocal fluorescence microscopy (FCFM) could be used to monitor cell therapy by mural progenitor cells (MPC). METHODS: Fifty mice bearing TC1 murine xenograft tumors were allocated into: control (n = 17), sham (phosphate buffer saline, n = 16), and MPC-treated (MPC, n = 17) groups. MRI was performed before (D0 ) and 7 days (D7 ) after injection measuring tumor size, R2 * under air, oxygen, and carbogen using blood oxygen level dependent (BOLD) and f (fraction linked to microcirculation), D* (perfusion related coefficient) and Dr (restricted diffusion coefficient) using diffusion-weighted sequences based on the IVIM (intravoxel incoherent motion) method. FCFM was performed at D7 measuring "index leakage" (capillary permeability). RESULTS: Tumor growth was significantly slowed down in the MPC-treated animals (P = 0.002) on D7 . R2 *air significantly decreased in controls between D0 and D7 (P = 0.03), reflecting a decrease in tumor oxygenation. ΔR2 *O2CO2 significantly increased in controls between D0 and D7 (P = 0.01) reflecting loss of vessel response to carbogen. D* significantly decreased in controls between D0 and D7 (P = 0.03). Finally, "index leakage" was lower in the MPC-treated tumors (P = 0,009). CONCLUSION: Treatment by MPC resulted in slowing down of tumor growth, capillary permeability decrease, and stabilization of tumor angiogenesis.

Oncogene-Driven Induction of Orthotopic Cholangiocarcinoma in Mice.

Cholangiocarcinoma (CCA) is a malignancy affecting the epithelial cells that line the bile ducts. This cancer shows a poor prognosis and current treatments remain inefficient. Orthotopic CCA mouse models are useful for the development of innovative therapeutic strategies. Here, we describe an orthotopic model of intrahepatic CCA that can be easily induced in mice within 5 weeks at a high incidence. It is achieved by expressing two oncogenes, namely, (i) the intracellular domain of the Notch1 receptor (NICD) and (ii) AKT, in hepatocytes by means of the sleeping beauty transposon system. These plasmid vectors are delivered by hydrodynamic injection into the tail vein. The present chapter also describes how to perform magnetic resonance imaging (MRI) of the livers to visualize intrahepatic CCA nodules.

Dynamic contrast enhanced MRI demonstrate altered placental perfusion in the STOX1A preeclampsia mouse model.

INTRODUCTION: Preeclampsia, a hypertensive disorder of pregnancy triggered by placental dysfunction, is reproduced in the murine STOX1A model, with hypertension, proteinuria, and abnormalities in umbilical and uterine Dopplers. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is an innovative technique that provides insights into tissue perfusion. The present study aims at analyzing placental perfusion using DCE-MRI to further characterize placental defects in the STOX1A model. METHODS: Two study groups were formed: the "TgSTOX13 pregnancy group" from mating TgSTOX13 genotype males with wild-type females, and the "wild-type pregnancy group" from mating wild-type males with wild-type females. Blood pressure, urinary albumin to creatinine ratio, and fetal weights were measured and compared between the groups, while perfusion parameters were analyzed using both conventional compartmental (1C) and free-time point-Hermite (FTPH) models in the DCE analysis. RESULTS: Seventeen pregnant mice in the "TgSTOX13 pregnancy group" and thirteen in the "wild-type pregnant group" were included in the analysis. During late gestation, the TgSTOX13 pregnancy group exhibited higher blood pressure, elevated albumin/creatinine ratio, and decreased fetal weights compared to the wild-type pregnancy group. In the DCE analysis utilizing the 1C model, blood flow (Fb) was significantly reduced by approximately 31.8 % in the TgSTOX13 pregnancy group compared to the wild-type pregnancy group (p < 0.01), a finding corroborated by the FTPH model with a reduction estimated at 31.5 % (p < 0.01). DISCUSSION: Our investigation successfully utilized DCE MRI to assess placental perfusion in a mouse model of preeclampsia, revealing a significant reduction of approximately 30 % in the preeclamptic mice, mirroring human pathophysiology.

Targeted therapy for capillary-venous malformations.

Sporadic venous malformations are genetic conditions primarily caused by somatic gain-of-function mutation of PIK3CA or TEK, an endothelial transmembrane receptor signaling through PIK3CA. Venous malformations are associated with pain, bleedings, thrombosis, pulmonary embolism, esthetic deformities and, in severe cases, life-threatening situations. No authorized medical treatment exists for patients with venous malformations. Here, we created a genetic mouse model of PIK3CA-related capillary venous malformations that replicates patient phenotypes. We showed that these malformations only partially signal through AKT proteins. We compared the efficacy of different drugs, including rapamycin, a mTORC1 inhibitor, miransertib, an AKT inhibitor and alpelisib, a PI3Kα inhibitor at improving the lesions seen in the mouse model. We demonstrated the effectiveness of alpelisib in preventing vascular malformations' occurrence, improving the already established ones, and prolonging survival. Considering these findings, we were authorized to treat 25 patients with alpelisib, including 7 children displaying PIK3CA (n = 16) or TEK (n = 9)-related capillary venous malformations resistant to usual therapies including sirolimus, debulking surgical procedures or percutaneous sclerotherapies. We assessed the volume of vascular malformations using magnetic resonance imaging (MRI) for each patient. Alpelisib demonstrated improvement in all 25 patients. Vascular malformations previously considered intractable were reduced and clinical symptoms were attenuated. MRI showed a decrease of 33.4% and 27.8% in the median volume of PIK3CA and TEK malformations respectively, over 6 months on alpelisib. In conclusion, this study supports PI3Kα inhibition as a promising therapeutic strategy in patients with PIK3CA or TEK-related capillary venous malformations.

Fetoplacental oxygenation in an intrauterine growth restriction rat model by using blood oxygen level-dependent MR imaging at 4.7 T.

PURPOSE: To investigate blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging in an intrauterine growth restriction (IUGR) rat model as a noninvasive in vivo tool to evaluate the response of the fetoplacental units (FPUs) to oxygenation MATERIALS AND METHODS: All procedures were approved by the animal care committee. The study was performed between February and July 2010. The IUGR model based on the ligation of the left uterine vascular pedicle at embryonic day 17 of gestation was validated by weighing placentas and fetuses after MR imaging. FPUs in the left and right uterine horns were IUGR cases and controls, respectively. A small-animal 4.7-T MR imager was used. Multiple gradient-echo sequence (repetition time msec/echo time msec, 800/1.8-49.8) was performed at embryonic day 19. T2* relaxation time was measured before and after maternal hyperoxygenation for live FPUs in placenta, fetal liver, and brain. The effect of hyperoxygenation on BOLD MR imaging was analyzed with change in T2* between hyperoxygenation and ambient air. After dissection, live fetuses from both horns were identified and weighed. Changes in T2* were compared based on Student t tests. A mixed model was used to compare BOLD effect among horns and organs. RESULTS: Sixteen rats were studied. There was a significant fetal weight decrease in the IUGR FPUs (-21.9%; P < .001). Change in T2* differed significantly between IUGR cases and controls for placenta (5.25 msec vs 11.25 msec; P < .001) and fetal brain (3.7 msec vs 7.17 msec; P = .02), whereas there was no significant difference in the fetal liver (2.72 msec vs 3.18 msec; P = .47). CONCLUSION: BOLD MR imaging at 4.7 T can be used to evaluate the response to oxygenation in normal and IUGR FPUs. This technique has a potential role in the assessment of human pregnancy.

Evaluation of rat heart microvasculature with high-spatial-resolution susceptibility-weighted MR imaging.

PURPOSE: To demonstrate that strandlike hypointense signals seen in the myocardium of normal rat hearts correspond to myocardial microvessels with high-spatial-resolution susceptibility-weighted (SW) magnetic resonance (MR) imaging without injection of contrast medium. MATERIALS AND METHODS: Animal experiments were performed with institutional animal care committee approval. Ex vivo cardiac MR imaging was performed in 10 normal Wistar rats with a 4.7-T imager and a cryogenic probe. The hypothesis that thin tubular hypointense signals in the myocardium of rat hearts at SW MR imaging sequences (group 1, n = 6; in-plane resolution, 39 µm) represent intramyocardial microvessels was tested. A superparamagnetic intravascular contrast agent (ferumoxsil; Lumirem) was used to explore the distribution of the intramyocardial microvessels (group 2, n = 4; three-dimensional fast imaging with steady-state free precession sequences). Nonparametric Mann-Whitney tests were performed to compare groups 1 and 2 both for microvascular densities (MVD) on histologic sections and for MR imaging signal intensities (SIs). Wilcoxon signed rank tests were used for paired comparison of subepicardial and subendocardial MVD and SI within groups. RESULTS: Ferumoxsil opacified the coronary microvasculature (group 2) on MR-matched histologic sections. No statistically significant difference was found between groups 1 and 2 for either MVD or MR imaging SI expressed as ratios between subendocardium and subepicardium (P = .40 and P = .46, respectively). The comparison of mean subendocardial and subepicardial SI within groups revealed significantly more microvessels in the subepicardium with MR (group 1: P = .01; group 2: P = .004). CONCLUSION: Myocardial microvessels appear as strandlike structures on high-spatial-resolution SW MR images without the aid of contrast medium injection.

Therapeutic potential of extracellular vesicles derived from cardiac progenitor cells in rodent models of chemotherapy-induced cardiomyopathy.

Background: Current treatments of chemotherapy-induced cardiomyopathy (CCM) are of limited efficacy. We assessed whether repeated intravenous injections of human extracellular vesicles from cardiac progenitor cells (EV-CPC) could represent a new therapeutic option and whether EV manufacturing according to a Good Manufacturing Practices (GMP)-compatible process did not impair their bioactivity. Methods: Immuno-competent mice received intra-peritoneal injections (IP) of doxorubicin (DOX) (4 mg/kg each; cumulative dose: 12 mg/kg) and were then intravenously (IV) injected three times with EV-CPC (total dose: 30 billion). Cardiac function was assessed 9-11 weeks later by cardiac magnetic resonance imaging (CMR) using strain as the primary end point. Then, immuno-competent rats received 5 IP injections of DOX (3 mg/kg each; cumulative dose 15 mg/kg) followed by 3 equal IV injections of GMP-EV (total dose: 100 billion). Cardiac function was assessed by two dimensional-echocardiography. Results: In the chronic mouse model of CCM, DOX + placebo-injected hearts incurred a significant decline in basal (global, epi- and endocardial) circumferential strain compared with sham DOX-untreated mice (p = 0.043, p = 0.042, p = 0.048 respectively) while EV-CPC preserved these indices. Global longitudinal strain followed a similar pattern. In the rat model, IV injections of GMP-EV also preserved left ventricular end-systolic and end-diastolic volumes compared with untreated controls. Conclusions: Intravenously-injected extracellular vesicles derived from CPC have cardio-protective effects which may make them an attractive user-friendly option for the treatment of CCM.

Acute stress induces long-term metabolic, functional, and structural remodeling of the heart.

Takotsubo cardiomyopathy is a stress-induced cardiovascular disease with symptoms comparable to those of an acute coronary syndrome but without coronary obstruction. Takotsubo was initially considered spontaneously reversible, but epidemiological studies revealed significant long-term morbidity and mortality, the reason for which is unknown. Here, we show in a female rodent model that a single pharmacological challenge creates a stress-induced cardiomyopathy similar to Takotsubo. The acute response involves changes in blood and tissue biomarkers and in cardiac in vivo imaging acquired with ultrasound, magnetic resonance and positron emission tomography. Longitudinal follow up using in vivo imaging, histochemistry, protein and proteomics analyses evidences a continued metabolic reprogramming of the heart towards metabolic malfunction, eventually leading to irreversible damage in cardiac function and structure. The results combat the supposed reversibility of Takotsubo, point to dysregulation of glucose metabolic pathways as a main cause of long-term cardiac disease and support early therapeutic management of Takotsubo.

Hemifacial myohyperplasia is due to somatic muscular PIK3CA gain-of-function mutations and responds to pharmacological inhibition.

Hemifacial myohyperplasia (HFMH) is a rare cause of facial asymmetry exclusively involving facial muscles. The underlying cause and the mechanism of disease progression are unknown. Here, we identified a somatic gain-of-function mutation of PIK3CA in five pediatric patients with HFMH. To understand the physiopathology of muscle hypertrophy in this context, we created a mouse model carrying specifically a PIK3CA mutation in skeletal muscles. PIK3CA gain-of-function mutation led to striated muscle cell hypertrophy, mitochondria dysfunction, and hypoglycemia with low circulating insulin levels. Alpelisib treatment, an approved PIK3CA inhibitor, was able to prevent and reduce muscle hypertrophy in the mouse model with correction of endocrine anomalies. Based on these findings, we treated the five HFMH patients. All patients demonstrated clinical, esthetical, and radiological improvement with proof of target engagement. In conclusion, we show that HFMH is due to somatic alteration of PIK3CA and is accessible to pharmacological intervention.

Adipose tissue macrophages: MR tracking to monitor obesity-associated inflammation.

PURPOSE: To investigate whether cellular imaging by using ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance (MR) imaging can allow detection and quantification of adipose tissue macrophage-related inflammation within adipose tissue in a mouse model. MATERIALS AND METHODS: Experimental protocols were conducted in accordance with French government policies. Adipose tissue macrophages were detected and quantified with a 4.7-T MR imager in ob/ob obese mice on the basis of the signal variance of adipose tissue triggered by injection of P904 iron oxide nanoparticles (USPIO). Mice were either intravenously injected with 1000 µmol of iron per kilogram of body weight of P904 (10 ob/ob and 11 ob/+) or used as noninjected control animals (seven ob/ob and six ob/+). Three-dimensional T2*-weighted gradient-echo MR images were acquired 10 days after intravenous injection. MR imaging signal variance in mice was correlated to adipose tissue macrophage quantification by using monoclonal antibody to F4/80 immunostaining, to proinflammatory marker quantification by using reverse transcription polymerase chain reaction (CCl2, Tnfα, Emr1), and to P904 quantification by using electron paramagnetic resonance imaging. Quantitative data were compared by using the Mann-Whitney or Student t test, and correlations were performed by using the Pearson correlation test. RESULTS: MR imaging measurements showed a significant increase in adipose tissue signal variance in ob/ob mice compared with ob/+ controls or noninjected animals (P < .0001), which was consistent with increased P904 uptake by adipose tissue in ob/ob mice. There was a significant and positive correlation between adipose tissue macrophage quantification at MR imaging and P904 iron oxide content (r = 0.87, P < .0001), adipose tissue macrophage-related inflammation at immunohistochemistry (r = 0.60, P < .01), and adipose tissue proinflammatory marker expression (r = 0.55, 0.56, and 0.58 for CCl2, Tnfα, and Emr1, respectively; P < .01). CONCLUSION: P904 USPIO-enhanced MR imaging is potentially a tool for noninvasive assessment of adipose tissue inflammation during experimental obesity. These results provide the basis for translation of MR imaging into clinical practice as a marker of patients at risk for metabolic syndrome.

Remnants-preserving ACL reconstruction using direct tendinous graft fixation: a new rat model.

BACKGROUND: Anterior cruciate ligament (ACL) repair techniques are new emerging strategies prevailing, in selected cases, over standard reconstruction of the ACL with excision of its remnants. Mid-substance ACL tears represent a challenge for ACL repair techniques, and remnants-preserving ACL reconstruction (rp-ACLR) using an autograft remains the recommended treatment in this situation. However, morbidity associated with the autograft harvesting prompts the need for alternative surgical strategies based on the use of synthetic scaffolds. Relevant small animal models of mid-substance tears with ACL remnants preservation and reconstruction are necessary to establish the preliminary proof of concept of these new strategies. METHODS: A rat model of rp-ACLR using a tendinous autograft after complete mid-substance ACL transection was established. Twelve weeks following surgery, clinical outcomes and knee joints were assessed through visual gait analysis, Lachman tests, thigh perimeter measurements, magnetic resonance imaging, micro-computed tomography, and histology, to evaluate the morbidity of the procedure, accuracy of bone tunnel positioning, ACL remnants fate, osteoarthritis, and autograft bony integration. Results were compared with those obtained with isolated ACL transection without reconstruction and to right non-operated knees. RESULTS AND DISCUSSION: Most operated animals were weight-bearing the day following surgery, and no adverse inflammatory reaction has been observed for the whole duration of the study. Autograft fixation with cortical screws provided effective graft anchorage until sacrifice. Healing of the transected ACL was not observed in the animals in which no graft reconstruction was performed. rp-ACLR was associated with a reduced degeneration of the ACL remnants (p = 0.004) and cartilages (p = 0.0437). Joint effusion and synovitis were significantly lower in the reconstructed group compared to the transected ACL group (p = 0.004). Most of the bone tunnel apertures were anatomically positioned in the coronal and/or sagittal plane. The most deviated bone tunnel apertures were the tibial ones, located in median less than 1 mm posteriorly to anatomical ACL footprint center. CONCLUSION: This study presents a cost-effective, new relevant and objective rat model associated with low morbidity for the preliminary study of bio-implantable materials designed for remnants-preserving ACL surgery after mid-substance ACL tear.

Dynamic contrast enhanced - MRI efficiency in detecting embolization-induced perfusion defects in a rabbit model of critical-limb-ischemia.

Critical limb ischemia (CLI) is a severe disease which affects about 2 million people in the US. Its prevalence is assessed at 800/100,000 population. However, no reliable tools are currently available to assess perfusion defects at the muscle tissue level. DCE-MRI is a technique that holds the potential to be effective in achieving this goal. However, preclinical studies performed with DCE-MRI have indicated low sensitivity assessing perfusion at resting state. To improve these previous results, in this work we propose new methodologies for data acquisition and analysis and we also revisit the biological model used for evaluation. Eleven rabbits underwent embolization of a lower limb. They were imaged at day 7 after embolization using DCE-MRI, performed on a 4.7 T small imaging device. Among them, n = 4 rabbits were used for MRI sequence optimization and n = 6 for data analysis after one exclusion. Normalized Areas under the curve (AUCn), and kinetic parameters such as Ktrans and Vd resulting from the Tofts-Kety modeling (KTM) were calculated on the embolized and contralateral limbs. Average and heterogeneity features, consisting on standard-deviation and quantiles, were calculated on muscle groups and whole limbs. The Wilcoxon and Fisher-tests were performed to compare embolized and contralateral regions of interests. The Wilcoxon test was also used to compare features of parametric maps. Quantiles of 5 and 95% in the contralateral side were used to define low and high outliers. A P-value <0.05 was considered statistically significant. Average features were inefficient to identify injured muscles, in agreement with the low sensitivity of the technique previously reported by the literature. However, these findings were dramatically improved by the use of additional heterogeneity features (97% of total accuracy for group muscles, P < 0.01 and 100% of total accuracy for the total limbs). The mapping analysis and automatic outlier detection quantification improvement was explained by the presence of local hyperemia that impair the average calculations. The analysis with KTM did not provide any additional information compared to AUCn. The DCE technique can be effective in detecting embolization-induced disorders of limb muscles in a CLI model when heterogeneity is taken into account in the data processing, even without vascular stimulation. The simultaneous presence of areas of ischemia and hyperemia appeared as a signature of the injured limbs. These areas seem to reflect the simultaneous presence of infarcted areas and viable peripheral areas, characterized by a vascular response that is visible in DCE.

Preclinical evaluation of targeted therapies in Sdhb-mutated tumors.

Therapies for metastatic SDHB-dependent pheochromocytoma and paraganglioma (PPGL) are limited and poorly efficient. New targeted therapies and identification of early non-invasive biomarkers of response are thus urgently needed for these patients. We characterized an in vivo allograft model of spontaneously immortalized murine chromaffin cells (imCC) with inactivation of the Sdhb gene by dynamic contrast-enhanced MRI (DCE-MRI) and 18FDG-PET. We evaluated the response to several therapies: IACS-010759 (mitochondrial respiratory chain complex I inhibitor), sunitinib (tyrosine kinase inhibitor with anti-angiogenic activity), talazoparib (poly ADP ribose polymerase (PARP) inhibitor) combined or not to temozolomide (alkylating agent), pharmacological inhibitors of HIF2a (PT2385 and PT2977 (belzutifan)) and molecular inactivation of HIF2a (imCC Sdhb-/- shHIF2a). Multimodal imaging was performed, including magnetic resonance spectroscopy (1H-MRS) to monitor the level of succinate in vivo. The allografted model of Sdhb-/- imCC reflected SDHB-deficient tumors, with increased angiogenesis and a particular avidity for 18FDG. After 14 days of treatment, IACS-010759, sunitinib and talazoparib at high doses allowed a significant reduction of the tumor volumes. In contrast to the tumor growth inhibition observed in Sdhb-/- shHIF2a imCC tumors, pharmacological inhibitors of HIF2a (PT2385 and belzutifan) showed no antitumor action in this model, alone or in combination with sunitinib. 1H-MRS, but not DCE-MRI, enabled the monitoring response to sunitinib, which was the best treatment in this study, promoting a decrease in succinate levels detected in vivo. This study paves the way for new therapeutic options and reveals a potential new early biomarker of response to treatment in SDHB-dependent PPGL.

PIK3CA gain-of-function mutation in adipose tissue induces metabolic reprogramming with Warburg-like effect and severe endocrine disruption.

PIK3CA-related overgrowth syndrome (PROS) is a genetic disorder caused by somatic mosaic gain-of-function mutations of PIK3CA. Clinical presentation of patients is diverse and associated with endocrine disruption. Adipose tissue is frequently involved, but its role in disease development and progression has not been elucidated. Here, we created a mouse model of PIK3CA-related adipose tissue overgrowth that recapitulates patient phenotype. We demonstrate that PIK3CA mutation leads to GLUT4 membrane accumulation with a negative feedback loop on insulin secretion, a burst of liver IGFBP1 synthesis with IGF-1 sequestration, and low circulating levels. Mouse phenotype was mainly driven through AKT2. We also observed that PIK3CA mutation induces metabolic reprogramming with Warburg-like effect and protein and lipid synthesis, hallmarks of cancer cells, in vitro, in vivo, and in patients. We lastly show that alpelisib is efficient at preventing and improving PIK3CA-adipose tissue overgrowth and reversing metabolomic anomalies in both animal models and patients.