Complete spatiotemporal quantification of cardiac motion in mice through enhanced acquisition and super-resolution reconstruction.

The quantification of cardiac motion using cardiac magnetic resonance imaging (CMR) has shown promise as an early-stage marker for cardiovascular diseases. Despite the growing popularity of CMR-based myocardial strain calculations, measures of complete spatiotemporal strains (i.e., three-dimensional strains over the cardiac cycle) remain elusive. Complete spatiotemporal strain calculations are primarily hampered by poor spatial resolution, with the rapid motion of the cardiac wall also challenging the reproducibility of such strains. We hypothesize that a super-resolution reconstruction (SRR) framework that leverages combined image acquisitions at multiple orientations will enhance the reproducibility of complete spatiotemporal strain estimation. Two sets of CMR acquisitions were obtained for five wild-type mice, combining short-axis scans with radial and orthogonal long-axis scans. Super-resolution reconstruction, integrated with tissue classification, was performed to generate full four-dimensional (4D) images. The resulting enhanced and full 4D images enabled complete quantification of the motion in terms of 4D myocardial strains. Additionally, the effects of SRR in improving accurate strain measurements were evaluated using an in-silico heart phantom. The SRR framework revealed near isotropic spatial resolution, high structural similarity, and minimal loss of contrast, which led to overall improvements in strain accuracy. In essence, a comprehensive methodology was generated to quantify complete and reproducible myocardial deformation, aiding in the much-needed standardization of complete spatiotemporal strain calculations.

Single-cell sequencing dissects the transcriptional identity of activated fibroblasts and identifies novel persistent distal tubular injury patterns in kidney fibrosis.

Examining kidney fibrosis is crucial for mechanistic understanding and developing targeted strategies against chronic kidney disease (CKD). Persistent fibroblast activation and tubular epithelial cell (TEC) injury are key CKD contributors. However, cellular and transcriptional landscapes of CKD and specific activated kidney fibroblast clusters remain elusive. Here, we analyzed single cell transcriptomic profiles of two clinically relevant kidney fibrosis models which induced robust kidney parenchymal remodeling. We dissected the molecular and cellular landscapes of kidney stroma and newly identified three distinctive fibroblast clusters with "secretory", "contractile" and "vascular" transcriptional enrichments. Also, both injuries generated failed repair TECs (frTECs) characterized by decline of mature epithelial markers and elevation of stromal and injury markers. Notably, frTECs shared transcriptional identity with distal nephron segments of the embryonic kidney. Moreover, we identified that both models exhibited robust and previously unrecognized distal spatial pattern of TEC injury, outlined by persistent elevation of renal TEC injury markers including Krt8 and Vcam1, while the surviving proximal tubules (PTs) showed restored transcriptional signature. We also found that long-term kidney injuries activated a prominent nephrogenic signature, including Sox4 and Hox gene elevation, which prevailed in the distal tubular segments. Our findings might advance understanding of and targeted intervention in fibrotic kidney disease.

Therapeutic Targeting of the GSK3ß-CUGBP1 Pathway in Myotonic Dystrophy.

Myotonic Dystrophy type 1 (DM1) is a neuromuscular disease associated with toxic RNA containing expanded CUG repeats. The developing therapeutic approaches to DM1 target mutant RNA or correct early toxic events downstream of the mutant RNA. We have previously described the benefits of the correction of the GSK3ß-CUGBP1 pathway in DM1 mice (HSALR model) expressing 250 CUG repeats using the GSK3 inhibitor tideglusib (TG). Here, we show that TG treatments corrected the expression of ~17% of genes misregulated in DM1 mice, including genes involved in cell transport, development and differentiation. The expression of chloride channel 1 (Clcn1), the key trigger of myotonia in DM1, was also corrected by TG. We found that correction of the GSK3ß-CUGBP1 pathway in mice expressing long CUG repeats (DMSXL model) is beneficial not only at the prenatal and postnatal stages, but also during adulthood. Using a mouse model with dysregulated CUGBP1, which mimics alterations in DM1, we showed that the dysregulated CUGBP1 contributes to the toxicity of expanded CUG repeats by changing gene expression and causing CNS abnormalities. These data show the critical role of the GSK3ß-CUGBP1 pathway in DM1 muscle and in CNS pathologies, suggesting the benefits of GSK3 inhibitors in patients with different forms of DM1.

Early postnatal microglial ablation in the Ccdc39 mouse model reveals adverse effects on brain development and in neonatal hydrocephalus.

BACKGROUND: Neonatal hydrocephalus is a congenital abnormality resulting in an inflammatory response and microglial cell activation both clinically and in animal models. Previously, we reported a mutation in a motile cilia gene, Ccdc39 that develops neonatal progressive hydrocephalus (prh) with inflammatory microglia. We discovered significantly increased amoeboid-shaped activated microglia in periventricular white matter edema, reduced mature homeostatic microglia in grey matter, and reduced myelination in the prh model. Recently, the role of microglia in animal models of adult brain disorders was examined using cell type-specific ablation by colony-stimulating factor-1 receptor (CSF1R) inhibitor, however, little information exists regarding the role of microglia in neonatal brain disorders such as hydrocephalus. Therefore, we aim to see if ablating pro-inflammatory microglia, and thus suppressing the inflammatory response, in a neonatal hydrocephalic mouse line could have beneficial effects. METHODS: In this study, Plexxikon 5622 (PLX5622), a CSF1R inhibitor, was subcutaneously administered to wild-type (WT) and prh mutant mice daily from postnatal day (P) 3 to P7. MRI-estimated brain volume was compared with untreated WT and prh mutants P7-9 and immunohistochemistry of the brain sections was performed at P8 and P18-21. RESULTS: PLX5622 injections successfully ablated IBA1-positive microglia in both the WT and prh mutants at P8. Of the microglia that are resistant to PLX5622 treatment, there was a higher percentage of amoeboid-shaped microglia, identified by morphology with retracted processes. In PLX-treated prh mutants, there was increased ventriculomegaly and no change in the total brain volume was observed. Also, the PLX5622 treatment significantly reduced myelination in WT mice at P8, although this was recovered after full microglia repopulation by P20. Microglia repopulation in the mutants worsened hypomyelination at P20. CONCLUSIONS: Microglia ablation in the neonatal hydrocephalic brain does not improve white matter edema, and actually worsens ventricular enlargement and hypomyelination, suggesting critical functions of homeostatic ramified microglia to better improve brain development with neonatal hydrocephalus. Future studies with detailed examination of microglial development and status may provide a clarification of the need for microglia in neonatal brain development.

Single-cell sequencing dissects the transcriptional identity of activated fibroblasts and identifies novel persistent distal tubular injury patterns in kidney fibrosis.

Examining kidney fibrosis is crucial for mechanistic understanding and developing targeted strategies against chronic kidney disease (CKD). Persistent fibroblast activation and tubular epithelial cell (TEC) injury are key CKD contributors. However, cellular and transcriptional landscapes of CKD and specific activated kidney fibroblast clusters remain elusive. Here, we analyzed single cell transcriptomic profiles of two clinically relevant kidney fibrosis models which induced robust kidney parenchymal remodeling. We dissected the molecular and cellular landscapes of kidney stroma and newly identified three distinctive fibroblast clusters with "secretory", "contractile" and "vascular" transcriptional enrichments. Also, both injuries generated failed repair TECs (frTECs) characterized by decline of mature epithelial markers and elevation of stromal and injury markers. Notably, frTECs shared transcriptional identity with distal nephron segments of the embryonic kidney. Moreover, we identified that both models exhibited robust and previously unrecognized distal spatial pattern of TEC injury, outlined by persistent elevation of renal TEC injury markers including Krt8, while the surviving proximal tubules (PTs) showed restored transcriptional signature. Furthermore, we found that long-term kidney injuries activated a prominent nephrogenic signature, including Sox4 and Hox gene elevation, which prevailed in the distal tubular segments. Our findings might advance understanding of and targeted intervention in fibrotic kidney disease.

Short-term fasting lowers glucagon levels under euglycemic and hypoglycemic conditions in healthy humans.

Fasting is associated with increased susceptibility to hypoglycemia in people with type 1 diabetes, thereby making it a significant health risk. To date, the relationship between fasting and insulin-induced hypoglycemia has not been well characterized, so our objective was to determine whether insulin-independent factors, such as counterregulatory hormone responses, are adversely impacted by fasting in healthy control individuals. Counterregulatory responses to insulin-induced hypoglycemia were measured in 12 healthy people during 2 metabolic studies. During one study, participants ate breakfast and lunch, after which they underwent a 2-hour bout of insulin-induced hypoglycemia (FED). During the other study, participants remained fasted prior to hypoglycemia (FAST). As expected, hepatic glycogen concentrations were lower in FAST, and associated with diminished peak glucagon levels and reduced endogenous glucose production (EGP) during hypoglycemia. Accompanying lower EGP in FAST was a reduction in peripheral glucose utilization, and a resultant reduction in the amount of exogenous glucose required to maintain glycemia. These data suggest that whereas a fasting-induced lowering of glucose utilization could potentially delay the onset of insulin-induced hypoglycemia, subsequent reductions in glucagon levels and EGP are likely to encumber recovery from it. As a result of this diminished metabolic flexibility in response to fasting, susceptibility to hypoglycemia could be enhanced in patients with type 1 diabetes under similar conditions.

Upregulation of acid ceramidase contributes to tumor progression in tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is characterized by multisystem, low-grade neoplasia involving the lung, kidneys, brain, and heart. Lymphangioleiomyomatosis (LAM) is a progressive pulmonary disease affecting almost exclusively women. TSC and LAM are both caused by mutations in TSC1 and TSC2 that result in mTORC1 hyperactivation. Here, we report that single-cell RNA sequencing of LAM lungs identified activation of genes in the sphingolipid biosynthesis pathway. Accordingly, the expression of acid ceramidase (ASAH1) and dihydroceramide desaturase (DEGS1), key enzymes controlling sphingolipid and ceramide metabolism, was significantly increased in TSC2-null cells. TSC2 negatively regulated the biosynthesis of tumorigenic sphingolipids, and suppression of ASAH1 by shRNA or the inhibitor ARN14976 (17a) resulted in markedly decreased TSC2-null cell viability. In vivo, 17a significantly decreased the growth of TSC2-null cell-derived mouse xenografts and short-term lung colonization by TSC2-null cells. Combined rapamycin and 17a treatment synergistically inhibited renal cystadenoma growth in Tsc2+/- mice, consistent with increased ASAH1 expression and activity being rapamycin insensitive. Collectively, the present study identifies rapamycin-insensitive ASAH1 upregulation in TSC2-null cells and tumors and provides evidence that targeting aberrant sphingolipid biosynthesis pathways has potential therapeutic value in mechanistic target of rapamycin complex 1-hyperactive neoplasms, including TSC and LAM.

Diphtheria toxin induced but not CSF1R inhibitor mediated microglia ablation model leads to the loss of CSF/ventricular spaces in vivo that is independent of cytokine upregulation.

BACKGROUND: Two recently developed novel rodent models have been reported to ablate microglia, either by genetically targeting microglia (via Cx3cr1-creER: iDTR + Dtx) or through pharmacologically targeting the CSF1R receptor with its inhibitor (PLX5622). Both models have been widely used in recent years to define essential functions of microglia and have led to high impact studies that have moved the field forward. METHODS: Using either Cx3cr1-iDTR mice in combination with Dtx or via the PLX5622 diet to pharmacologically ablate microglia, we compared the two models via MRI and histology to study the general anatomy of the brain and the CSF/ventricular systems. Additionally, we analyzed the cytokine profile in both microglia ablation models. RESULTS: We discovered that the genetic ablation (Cx3cr1-iDTR + Dtx), but not the pharmacological microglia ablation (PLX5622), displays a surprisingly rapid pathological condition in the brain represented by loss of CSF/ventricles without brain parenchymal swelling. This phenotype was observed both in MRI and histological analysis. To our surprise, we discovered that the iDTR allele alone leads to the loss of CSF/ventricles phenotype following diphtheria toxin (Dtx) treatment independent of cre expression. To examine the underlying mechanism for the loss of CSF in the Cx3cr1-iDTR ablation and iDTR models, we additionally investigated the cytokine profile in the Cx3cr1-iDTR + Dtx, iDTR + Dtx and the PLX models. We found increases of multiple cytokines in the Cx3cr1-iDTR + Dtx but not in the pharmacological ablation model nor the iDTR + Dtx mouse brains at the time of CSF loss (3 days after the first Dtx injection). This result suggests that the upregulation of cytokines is not the cause of the loss of CSF, which is supported by our data indicating that brain parenchyma swelling, or edema are not observed in the Cx3cr1-iDTR + Dtx microglia ablation model. Additionally, pharmacological inhibition of the KC/CXCR2 pathway (the most upregulated cytokine in the Cx3cr1-iDTR + Dtx model) did not resolve the CSF/ventricular loss phenotype in the genetic microglia ablation model. Instead, both the Cx3cr1-iDTR + Dtx ablation and iDTR + Dtx models showed increased activated IBA1 + cells in the choroid plexus (CP), suggesting that CP-related pathology might be the contributing factor for the observed CSF/ventricular shrinkage phenotype. CONCLUSIONS: Our data, for the first time, reveal a robust and global CSF/ventricular space shrinkage pathology in the Cx3cr1-iDTR genetic ablation model caused by iDTR allele, but not in the PLX5622 ablation model, and suggest that this pathology is not due to brain edema formation but to CP related pathology. Given the wide utilization of the iDTR allele and the Cx3cr1-iDTR model, it is crucial to fully characterize this pathology to understand the underlying causal mechanisms. Specifically, caution is needed when utilizing this model to interpret subtle neurologic functional changes that are thought to be mediated by microglia but could, instead, be due to CSF/ventricular loss in the genetic ablation model.

An image registration framework to estimate 3D myocardial strains from cine cardiac MRI in mice.

Accurate and efficient quantification of cardiac motion offers promising biomarkers for non-invasive diagnosis and prognosis of structural heart diseases. Cine cardiac magnetic resonance imaging remains one of the most advanced imaging tools to provide image acquisitions needed to assess and quantify in-vivo heart kinematics. The majority of cardiac motion studies are focused on human data, and there remains a need to develop and implement an image-registration pipeline to quantify full three-dimensional (3D) cardiac motion in mice where ideal image acquisition is challenged by the subject size and heart rate and the possibility of traditional tagged imaging is hampered. In this study, we used diffeomorphic image registration to estimate strains in the left ventricular wall in two wild-type mice and one diabetic mouse. Our pipeline resulted in a continuous and fully 3D strain map over one cardiac cycle. The estimation of 3D regional and transmural variations of strains is a critical step towards identifying mechanistic biomarkers for improved diagnosis and phenotyping of structural left heart diseases including heart failure with reduced or preserved ejection fraction.

Creatine transporter deficiency impairs stress adaptation and brain energetics homeostasis.

The creatine transporter (CrT) maintains brain creatine (Cr) levels, but the effects of its deficiency on energetics adaptation under stress remain unclear. There are also no effective treatments for CrT deficiency, the second most common cause of X-linked intellectual disabilities. Herein, we examined the consequences of CrT deficiency in brain energetics and stress-adaptation responses plus the effects of intranasal Cr supplementation. We found that CrT-deficient (CrT-/y) mice harbored dendritic spine and synaptic dysgenesis. Nurtured newborn CrT-/y mice maintained baseline brain ATP levels, with a trend toward signaling imbalance between the p-AMPK/autophagy and mTOR pathways. Starvation elevated the signaling imbalance and reduced brain ATP levels in P3 CrT-/y mice. Similarly, CrT-/y neurons and P10 CrT-/y mice showed an imbalance between autophagy and mTOR signaling pathways and greater susceptibility to cerebral hypoxia-ischemia and ischemic insults. Notably, intranasal administration of Cr after cerebral ischemia increased the brain Cr/N-acetylaspartate ratio, partially averted the signaling imbalance, and reduced infarct size more potently than intraperitoneal Cr injection. These findings suggest important functions for CrT and Cr in preserving the homeostasis of brain energetics in stress conditions. Moreover, intranasal Cr supplementation may be an effective treatment for congenital CrT deficiency and acute brain injury.

MRI Measures of Murine Liver Fibrosis.

BACKGROUND: An imaging method that allows quantitative fibrosis estimates is needed to facilitate the diagnosis of chronic liver disease. Amide proton transfer (APT) and tissue sodium concentration (TSC) estimates could meet this need. HYPOTHESIS: APT and TSC estimates correlate with fibrosis in a mouse model of chronic liver disease. STUDY TYPE: Prospective. PHANTOMS/ANIMAL MODEL: Male C57Bl/6 mice given CCl4 or vehicle (N = 8 each) twice weekly for 16 weeks. FIELD STRENGTH/SEQUENCE: Liver T1 (Look-Locker gradient recalled echo [GRE] sequence), T2 (multiecho spin echo sequence), T1rho (fast spin echo sequence with 500 Hz spin locking pulse), and APT (GRE sequence with off-resonance pulses) data were acquired at 7 T at 12 and 16 weeks. Liver sodium data (multiple echo GRE sequence) were acquired at 12 weeks at 9.4 T. ASSESSMENT: Liver proton T1 , T2 , T1rho , APT, sodium T2 *, and TSC were calculated. Histological measures included Sirius Red, hematoxylin and eosin, liver hydroxyproline content, and serum alanine transaminase (ALT). STATISTICAL TESTS: Welch's two-sided t-test was used to test for differences between control and CCl4 -treated groups for serum ALT, hydroxyproline, Sirius Red staining, T1 , T2 , T1rho , APT, TSC, and sodium T2 *. Pearson's correlations between liver T1 , APT, TSC, or sodium T2 * with Sirius Red staining and hydroxyproline levels were calculated. RESULTS: APT was significantly different (P < 0.05) between groups in the left liver lobe at 16 weeks (CCl4 : 8.0% ± 1.2%, controls: 6.2% ± 1.0%), as were average liver TSC at 12 weeks (CCl4 : 38 mM ± 5 mM, controls: 27 mM ± 2 mM), and average sodium liver T2 * at 12 weeks (CCl4 : 10 msec ± 1.0 msec, controls: 12 msec ± 1.9 msec). APT, TSC, and sodium T2 * correlated significantly (P < 0.05) with Sirius Red staining and hydroxyproline levels. DATA CONCLUSION: Liver TSC and APT significantly correlated with histopathologic markers of fibrosis in this mouse model. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 3.

Ablation of polyamine catabolic enzymes provokes Purkinje cell damage, neuroinflammation, and severe ataxia.

BACKGROUND: Polyamine catabolism plays a key role in maintaining intracellular polyamine pools, yet its physiological significance is largely unexplored. Here, we report that the disruption of polyamine catabolism leads to severe cerebellar damage and ataxia, demonstrating the fundamental role of polyamine catabolism in the maintenance of cerebellar function and integrity. METHODS: Mice with simultaneous deletion of the two principal polyamine catabolic enzymes, spermine oxidase and spermidine/spermine N1-acetyltransferase (Smox/Sat1-dKO), were generated by the crossbreeding of Smox-KO (Smox-/-) and Sat1-KO (Sat1-/-) animals. Development and progression of tissue injury was monitored using imaging, behavioral, and molecular analyses. RESULTS: Smox/Sat1-dKO mice are normal at birth, but develop progressive cerebellar damage and ataxia. The cerebellar injury in Smox/Sat1-dKO mice is associated with Purkinje cell loss and gliosis, leading to neuroinflammation and white matter demyelination during the latter stages of the injury. The onset of tissue damage in Smox/Sat1-dKO mice is not solely dependent on changes in polyamine levels as cerebellar injury was highly selective. RNA-seq analysis and confirmatory studies revealed clear decreases in the expression of Purkinje cell-associated proteins and significant increases in the expression of transglutaminases and markers of neurodegenerative microgliosis and astrocytosis. Further, the α-Synuclein expression, aggregation, and polyamination levels were significantly increased in the cerebellum of Smox/Sat1-dKO mice. Finally, there were clear roles of transglutaminase-2 (TGM2) in the cerebellar pathologies manifest in Smox/Sat1-dKO mice, as pharmacological inhibition of transglutaminases reduced the severity of ataxia and cerebellar injury in Smox/Sat1-dKO mice. CONCLUSIONS: These results indicate that the disruption of polyamine catabolism, via coordinated alterations in tissue polyamine levels, elevated transglutaminase activity and increased expression, polyamination, and aggregation of α-Synuclein, leads to severe cerebellar damage and ataxia. These studies indicate that polyamine catabolism is necessary to Purkinje cell survival, and for sustaining the functional integrity of the cerebellum.

Preclinical hyperpolarized 129 Xe MRI: ventilation and T2 * mapping in mouse lungs at 7 T using multi-echo flyback UTE.

Fast apparent transverse relaxation (short T2 *) is a common obstacle when attempting to perform quantitative 1 H MRI of the lungs. While T2 * times are longer for pulmonary hyperpolarized (HP) gas functional imaging (in particular for gaseous 129 Xe), T2 * can still lead to quantitative inaccuracies for sequences requiring longer echo times (such as diffusion weighted images) or longer readout duration (such as spiral sequences). This is especially true in preclinical studies, where high magnetic fields lead to shorter relaxation times than are typically seen in human studies. However, the T2 * of HP 129 Xe in the most common animal model of human disease (mice) has not been reported. Herein, we present a multi-echo radial flyback imaging sequence and use it to measure HP 129 Xe T2 * at 7 T under a variety of respiratory conditions. This sequence mitigates the impact of T1 relaxation outside the animal by using multiple gradient-refocused echoes to acquire images at a number of effective echo times for each RF excitation. After validating the sequence using a phantom containing water doped with superparamagnetic iron oxide nanoparticles, we measured the 129 Xe T2 * in vivo for 10 healthy C57Bl/6 J mice and found T2 * ~ 5 ms in the lung airspaces. Interestingly, T2 * was relatively constant over all experimental conditions, and varied significantly with sex, but not age, mass, or the O2 content of the inhaled gas mixture. These results are discussed in the context of T2 * relaxation within porous media.

A phase I study of AT-101, a BH3 mimetic, in combination with paclitaxel and carboplatin in solid tumors.

Background AT-101 is a BH3 mimetic that inhibits the heterodimerization of Bcl-2, Bcl-xL, Bcl-W, and Mcl-1 with pro-apoptotic proteins, thereby lowering the threshold for apoptosis. This phase I trial investigated the MTD of AT-101 in combination with paclitaxel and carboplatin in patients with advanced solid tumors. Methods Patients were treated with AT-101 (40 mg) every 12 h on days 1, 2 and 3 of each cycle combined with varying dose levels (DL) of paclitaxel and carboplatin [DL1: paclitaxel (150 mg/m2) and carboplatin (AUC 5) on day 1 of each cycle; DL2: paclitaxel (175 mg/m2) and carboplatin (AUC 6) on day 1 of each cycle]. Secondary objectives included characterizing toxicity, efficacy, pharmacokinetics, and pharmacodynamics of the combination. Results Twenty-four patients were treated across two DLs with a planned expansion cohort. The most common tumor type was prostate (N = 11). Two patients experienced DLTs: grade 3 abdominal pain at DL1 and grade 3 ALT increase at DL2; however, the MTD was not determined. Moderate hematologic toxicity was observed. One CR was seen in a patient with esophageal cancer and 4 patients achieved PRs (1 NSCLC, 3 prostate). PD studies did not yield statistically significant decreases in Bcl-2 and caspase 3 protein levels, or increased apoptotic activity induced by AT-101. Conclusion The combination of AT-101 at 40 mg every 12 h on days 1, 2 and 3 combined with paclitaxel and carboplatin was safe and tolerable. Based on the modest clinical efficacy seen in this trial, this combination will not be further investigated. Clinical Trial Registration: NCT00891072, CTEP#: 8016.

Impaired neural differentiation and glymphatic CSF flow in the Ccdc39 rat model of neonatal hydrocephalus: genetic interaction with L1cam.

Neonatal hydrocephalus affects about one child per 1000 births and is a major congenital brain abnormality. We previously discovered a gene mutation within the coiled-coil domain-containing 39 (Ccdc39) gene, which causes the progressive hydrocephalus (prh) phenotype in mice due to lack of ependymal-cilia-mediated cerebrospinal fluid (CSF) flow. In this study, we used CRISPR/Cas9 to introduce the Ccdc39 gene mutation into rats, which are more suitable for imaging and surgical experiments. The Ccdc39prh/prh mutants exhibited mild ventriculomegaly at postnatal day (P)5 that progressed into severe hydrocephalus by P11 (P<0.001). After P11, macrophage and neutrophil invasion along with subarachnoid hemorrhage were observed in mutant brains showing reduced neurofilament density, hypomyelination and increased cell death signals compared with wild-type brains. Significantly more macrophages entered the brain parenchyma at P5 before hemorrhaging was noted and increased expression of a pro-inflammatory factor (monocyte chemoattractant protein-1) was found in the cortical neural and endothelial cells in the mutant brains at P11. Glymphatic-mediated CSF circulation was progressively impaired along the middle cerebral artery from P11 as mutants developed severe hydrocephalus (P<0.001). In addition, Ccdc39prh/prh mutants with L1 cell adhesion molecule (L1cam) gene mutation, which causes X-linked human congenital hydrocephalus, showed an accelerated early hydrocephalus phenotype (P<0.05-0.01). Our findings in Ccdc39prh/prh mutant rats demonstrate a possible causal role of neuroinflammation in neonatal hydrocephalus development, which involves impaired cortical development and glymphatic CSF flow. Improved understanding of inflammatory responses and the glymphatic system in neonatal hydrocephalus could lead to new therapeutic strategies for this condition.This article has an associated First Person interview with the joint first authors of the paper.

Correction of Glycogen Synthase Kinase 3ß in Myotonic Dystrophy 1 Reduces the Mutant RNA and Improves Postnatal Survival of DMSXL Mice.

Myotonic dystrophy type 1 (DM1) is a multisystem neuromuscular disease without cure. One of the possible therapeutic approaches for DM1 is correction of the RNA-binding proteins CUGBP1 and MBNL1, misregulated in DM1. CUGBP1 activity is controlled by glycogen synthase kinase 3ß (GSK3ß), which is elevated in skeletal muscle of patients with DM1, and inhibitors of GSK3 were suggested as therapeutic molecules to correct CUGBP1 activity in DM1. Here, we describe that correction of GSK3ß with a small-molecule inhibitor of GSK3, tideglusib (TG), not only normalizes the GSK3ß-CUGBP1 pathway but also reduces the mutant DMPK mRNA in myoblasts from patients with adult DM1 and congenital DM1 (CDM1). Correction of GSK3ß in a mouse model of DM1 (HSALR mice) with TG also reduces the levels of CUG-containing RNA, normalizing a number of CUGBP1- and MBNL1-regulated mRNA targets. We also found that the GSK3ß-CUGBP1 pathway is abnormal in skeletal muscle and brain of DMSXL mice, expressing more than 1,000 CUG repeats, and that the correction of this pathway with TG increases postnatal survival and improves growth and neuromotor activity of DMSXL mice. These findings show that the inhibitors of GSK3, such as TG, may correct pathology in DM1 and CDM1 via several pathways.

Characterization of a novel rat model of X-linked hydrocephalus by CRISPR-mediated mutation in L1cam.

OBJECTIVE: Emergence of CRISPR/Cas9 genome editing provides a robust method for gene targeting in a variety of cell types, including fertilized rat embryos. The authors used this method to generate a transgenic rat L1cam knockout model of X-linked hydrocephalus (XLH) with human genetic etiology. The object of this study was to use diffusion tensor imaging (DTI) in studying perivascular white matter tract injury in the rat model and to characterize its pathological definition in histology. METHODS: Two guide RNAs designed to disrupt exon 4 of the L1cam gene on the X chromosome were injected into Sprague-Dawley rat embryos. Following embryo transfer into pseudopregnant females, rats were born and their DNA was sequenced for evidence of L1cam mutation. The mutant and control wild-type rats were monitored for growth and hydrocephalus phenotypes. Their macro- and microbrain structures were studied with T2-weighted MRI, DTI, immunohistochemistry, and transmission electron microscopy (TEM). RESULTS: The authors successfully obtained 2 independent L1cam knockout alleles and 1 missense mutant allele. Hemizygous male mutants from all 3 alleles developed hydrocephalus and delayed development. Significant reductions in fractional anisotropy and axial diffusivity were observed in the corpus callosum, external capsule, and internal capsule at 3 months of age. The mutant rats did not show reactive gliosis by then but exhibited hypomyelination and increased extracellular fluid in the corpus callosum. CONCLUSIONS: The CRISPR/Cas9-mediated genome editing system can be harnessed to efficiently disrupt the L1cam gene in rats for creation of a larger XLH animal model than previously available. This study provides evidence that the early pathology of the periventricular white matter tracts in hydrocephalus can be detected in DTI. Furthermore, TEM-based morphometric analysis of the corpus callosum elucidates the underlying cytopathological changes accompanying hydrocephalus-derived variations in DTI. The CRISPR/Cas9 system offers opportunities to explore novel surgical and imaging techniques on larger mammalian models.

Omega-3 fatty acid deficiency impairs frontostriatal recruitment following repeated amphetamine treatment in rats: A 7 Tesla in vivo phMRI study.

Although attention deficit hyperactivity disorder is associated with deficits in docosahexaenoic acid (DHA), an omega-3 fatty acid implicated in dopamine and glutamate synaptic plasticity, its role in neuroplastic brain changes that occur following repeated amphetamine (AMPH) treatment are not known. This study used pharmacological magnetic resonance imaging to investigate the impact of repeated AMPH exposure and alterations in brain DHA levels on AMPH-induced brain activation patterns. Male rats were fed a diet with no n-3 fatty acids (Deficient, DEF, n = 20), a diet fortified with preformed DHA (fish oil, FO, n = 20), or a control diet fortified with alpha-linolenic acid (n = 20) from P21 to P90. During adolescence (P40-60), one-half of each diet group received daily AMPH injections escalated weekly (0.5, 1.0, 2.5, 5.0 mg/kg/d) or drug vehicle. Following a 30-d abstinence period blood oxygen level dependent (BOLD) responses were determined in a 7 T Bruker Biospec system following an AMPH challenge (7.5 mg/kg, i.v). Postmortem erythrocyte and forebrain DHA composition were determined by gas chromatography. Compared with control rats, forebrain and erythrocyte DHA levels were significantly lower in DEF rats and significantly higher in FO rats. Across AMPH doses DEF rats exhibited greater locomotor activity compared to control and FO rats. In AMPH-naïve rats, the AMPH challenge increased BOLD activity in the substantia nigra and basal forebrain and no diet group differences were observed. In AMPH-pretreated control and FO rats, the AMPH challenge similarly increased BOLD activation in the bilateral caudate putamen, thalamus, and motor and cingulate cortices. In contrast, BOLD activation in AMPH-pretreated DEF rats was similar to AMPH-naïve DEF animals, and AMPH-pretreated DEF rats exhibited attenuated frontostriatal BOLD activation compared with AMPH-pretreated control and FO rats. These findings demonstrate that chronic escalating AMPH treatment induces enduring frontostriatal recruitment and that peri-adolescent deficits in brain DHA accrual impair this response.

Deficits in Docosahexaenoic Acid Accrual during Adolescence Reduce Rat Forebrain White Matter Microstructural Integrity: An in vivo Diffusion Tensor Imaging Study.

Neuropsychiatric disorders that frequently initially emerge during adolescence are associated with deficits in the omega-3 (n-3) fatty acid docosahexaenoic acid (DHA), elevated proinflammatory signaling, and regional reductions in white matter integrity (WMI). This study determined the effects of altering brain DHA accrual during adolescence on WMI in the rat brain by diffusion tensor imaging (DTI), and investigated the potential mediating role of proinflammatory signaling. During periadolescent development, male rats were fed a diet deficient in n-3 fatty acids (DEF, n = 20), a fish oil-fortified diet containing preformed DHA (FO, n = 20), or a control diet (CON, n = 20). In adulthood, DTI scans were performed and brain WMI was determined using voxelwise tract-based spatial statistics (TBSS). Postmortem fatty acid composition, peripheral (plasma IL-1ß, IL-6, and C-reactive protein [CRP]) and central (IL-1ß and CD11b mRNA) proinflammatory markers, and myelin basic protein (MBP) mRNA expression were determined. Compared with CON rats, forebrain DHA levels were lower in DEF rats and higher in FO rats. Compared with CON rats, DEF rats exhibited greater radial diffusivity (RD) and mean diffusivity in the right external capsule, and greater axial diffusivity in the corpus callosum genu and left external capsule. DEF rats also exhibited greater RD than FO rats in the right external capsule. Forebrain MBP expression did not differ between groups. Compared with CON rats, central (IL-1ß and CD11b) and peripheral (IL-1ß and IL-6) proinflammatory markers were not different in DEF rats, and DEF rats exhibited lower CRP levels. These findings demonstrate that deficits in adolescent DHA accrual negatively impact forebrain WMI, independently of elevated proinflammatory signaling.