A Frameless Stereotaxic MRI Technique for Macaque Neuroscience Studies

MRI has achieved widespread use for preplanning neuroscience procedures for non-human primate studies. However, orienting imaging studies in stereotaxic space has relied primarily on using a stereotaxic frame or co-registering fiducial markers with the neuroimaging. In this study, we present a simple approach in which the MRI dataset is aligned to the bony landmarks that define the Frankfurt stereotaxic baseline plane, without the need for a stereotaxic frame or additional external fiducials. To facilitate localizing the bony landmarks (infraorbital margin, external bony auditory meatus) on the MRI scans additional imaging landmarks (mid ocular plane, temporomandibular joint) are discussed that provide supplementary and readily visible points of reference

Skeletal myofiber vascular endothelial growth factor is required for the exercise training-induced increase in dentate gyrus neuronal precursor cells

Exercise signals neurogenesis in the dentate gyrus of the hippocampus. This phenomenon requires vascular endothelial growth factor (VEGF) originating from outside the blood–brain barrier, but no cellular source has been identified. Thus, we hypothesized that VEGF produced by skeletal myofibers plays a role in regulating hippocampal neuronal precursor cell proliferation following exercise training. This was tested in adult conditional skeletal myofiber‐specific VEGF gene‐ablated mice (VEGFHSA−/−) by providing VEGFHSA−/− and non‐ablated (VEGFf/f) littermates with running wheels for 14 days. Following this training period, hippocampal cerebral blood flow (CBF) was measured by functional magnetic resonance imaging (fMRI), and neuronal precursor cells (BrdU+/Nestin+) were detected by immunofluorescence. The VEGFf/f trained group showed improvements in both speed and endurance capacity in acute treadmill running tests (P < 0.05). The VEGFHSA−/− group did not. The number of proliferating neuronal precursor cells was increased with training in VEGFf/f (P < 0.05) but not in VEGFHSA−/− mice. Endothelial cell (CD31+) number did not change in this region with exercise training or skeletal myofiber VEGF gene deletion. However, resting blood flow through the hippocampal region was lower in VEGFHSA−/− mice, both untrained and trained, than untrained VEGFf/f mice (P < 0.05). An acute hypoxic challenge decreased CBF (P < 0.05) in untrained VEGFf/f, untrained VEGFHSA−/− and trained VEGFHSA−/− mice, but not trained VEGFf/f mice. VEGFf/f, but not VEGFHSA−/−, mice were able to acutely run on a treadmill at an intensity sufficient to increase hippocampus VEGF levels. These data suggest that VEGF expressed by skeletal myofibers may directly or indirectly regulate both hippocampal blood flow and neurogenisis

Magnetic Resonance Imaging of Tumors Colonized with Bacterial Ferritin-Expressing Escherichia coli

Background: Recent studies have shown that human ferritin can be used as a reporter of gene expression for magnetic resonance imaging (MRI). Bacteria also encode three classes of ferritin-type molecules with iron accumulation properties. Methods and Findings: Here, we investigated whether these bacterial ferritins can also be used as MRI reporter genes and which of the bacterial ferritins is the most suitable reporter. Bacterial ferritins were overexpressed in probiotic E. coli Nissle 1917. Cultures of these bacteria were analyzed and those generating highest MRI contrast were further investigated in tumor bearing mice. Among members of three classes of bacterial ferritin tested, bacterioferritin showed the most promise as a reporter gene. Although all three proteins accumulated similar amounts of iron when overexpressed individually, bacterioferritin showed the highest contrast change. By site-directed mutagenesis we also show that the heme iron, a unique part of the bacterioferritin molecule, is not critical for MRI contrast change. Tumor-specific induction of bacterioferritin-expression in colonized tumors resulted in contrast changes within the bacteria-colonized tumors. Conclusions: Our data suggest that colonization and gene expression by live vectors expressing bacterioferritin can be monitored by MRI due to contrast change

p75 neurotrophin receptor regulates energy balance in obesity

Obesity and metabolic syndrome reflect the dysregulation of molecular pathways that control energy homeostasis. Here, we show that the p75 neurotrophin receptor (p75NTR) controls energy expenditure in obese mice on a high-fat diet (HFD). Despite no changes in food intake, p75NTR-null mice were protected from HFD-induced obesity and remained lean as a result of increased energy expenditure without developing insulin resistance or liver steatosis. p75NTR directly interacts with the catalytic subunit of protein kinase A (PKA) and regulates cAMP signaling in adipocytes, leading to decreased lipolysis and thermogenesis. Adipocyte-specific depletion of p75NTR or transplantation of p75NTR-null white adipose tissue (WAT) into wild-type mice fed a HFD protected against weight gain and insulin resistance. Our results reveal that signaling from p75NTR to cAMP/PKA regulates energy balance and suggest that non-CNS neurotrophin receptor signaling could be a target for treating obesity and the metabolic syndrome

A Murine Model of Inflammation-Induced Cerebral Microbleeds

Background: Cerebral microhemorrhages (CMH) are tiny deposits of blood degradation products in the brain and are pathological substrates of cerebral microbleeds. The existing CMH animal models are β-amyloid-, hypoxic brain injury-, or hypertension-induced. Recent evidence shows that CMH develop independently of hypoxic brain injury, hypertension, or amyloid deposition and CMH are associated with normal aging, sepsis, and neurodegenerative conditions. One common factor among the above pathologies is inflammation, and recent clinical studies show a link between systemic inflammation and CMH. Hence, we hypothesize that inflammation induces CMH development and thus, lipopolysaccharide (LPS)-induced CMH may be an appropriate model to study cerebral microbleeds. Methods: Adult C57BL/6 mice were injected with LPS (3 or 1 mg/kg, i.p.) or saline at 0, 6, and 24 h. At 2 or 7 days after the first injection, brains were harvested. Hematoxylin and eosin (H&E) and Prussian blue (PB) were used to stain fresh (acute) hemorrhages and hemosiderin (sub-acute) hemorrhages, respectively. Brain tissue ICAM-1, IgG, Iba1, and GFAP immunohistochemistry were used to examine endothelium activation, blood-brain barrier (BBB) disruption, and neuroinflammation. MRI and fluorescence microscopy were used to further confirm CMH development in this model. Results: LPS-treated mice developed H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. No surface and negligible H&E-positive CMH were observed in saline-treated mice (n = 12). LPS (3 mg/kg; n = 10) produced significantly higher number, size, and area of H&E-positive CMH at 2 days. LPS (1 mg/kg; n = 9) produced robust development of PB-positive CMH at 7 days, with significantly higher number and area compared with saline (n = 9)-treated mice. CMH showed the highest distribution in the cerebellum followed by the sub-cortex and cortex. LPS-induced CMH were predominantly adjacent to cerebral capillaries, and CMH load was associated with indices of brain endothelium activation, BBB disruption, and neuroinflammation. Fluorescence microscopy confirmed the extravasation of red blood cells into the brain parenchyma, and MRI demonstrated the presence of cerebral microbleeds. Conclusions: LPS produced rapid and robust development of H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. The ease of development of both H&E- and PB-positive CMH makes the LPS-induced mouse model suitable to study inflammation-induced CMH

Targeting LIF-mediated paracrine interaction for pancreatic cancer therapy and monitoring.

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis largely owing to inefficient diagnosis and tenacious drug resistance. Activation of pancreatic stellate cells (PSCs) and consequent development of dense stroma are prominent features accounting for this aggressive biology1,2. The reciprocal interplay between PSCs and pancreatic cancer cells (PCCs) not only enhances tumour progression and metastasis but also sustains their own activation, facilitating a vicious cycle to exacerbate tumorigenesis and drug resistance3-7. Furthermore, PSC activation occurs very early during PDAC tumorigenesis8-10, and activated PSCs comprise a substantial fraction of the tumour mass, providing a rich source of readily detectable factors. Therefore, we hypothesized that the communication between PSCs and PCCs could be an exploitable target to develop effective strategies for PDAC therapy and diagnosis. Here, starting with a systematic proteomic investigation of secreted disease mediators and underlying molecular mechanisms, we reveal that leukaemia inhibitory factor (LIF) is a key paracrine factor from activated PSCs acting on cancer cells. Both pharmacologic LIF blockade and genetic Lifr deletion markedly slow tumour progression and augment the efficacy of chemotherapy to prolong survival of PDAC mouse models, mainly by modulating cancer cell differentiation and epithelial-mesenchymal transition status. Moreover, in both mouse models and human PDAC, aberrant production of LIF in the pancreas is restricted to pathological conditions and correlates with PDAC pathogenesis, and changes in the levels of circulating LIF correlate well with tumour response to therapy. Collectively, these findings reveal a function of LIF in PDAC tumorigenesis, and suggest its translational potential as an attractive therapeutic target and circulating marker. Our studies underscore how a better understanding of cell-cell communication within the tumour microenvironment can suggest novel strategies for cancer therapy

Feature-interaction detection based on feature-based specifications

A Gd3+-coordinated polymerizable analogue of the MRI contrast agent Gd-DOTA was used to prepare amphiphilic block copolymers, with hydrophilic blocks composed entirely of the polymerized contrast agent. The resulting amphiphilic block copolymers assemble into nanoparticles (NPs) of spherical- or fibril-shape, each demonstrating enhanced relaxivity over Gd-DOTA. As an initial examination of their behavior in vivo, intraperitoneal (IP) injection of NPs into live mice was performed, showing long IP residence times, observed by MRI. Extended residence times for particles of well-defined morphology may represent a valuable design paradigm for treatment or diagnosis of peritoneal malignances