In vivo proton MR spectroscopy of pancreatic neuroendocrine tumors in a multiple endocrine neoplasia type 1 conditional knockout mouse model

Corrected cerebral blood flow and reduced cerebral inflammation in berk sickle mice with higher fetal hemoglobin

Fetal hemoglobin (HbF) is known to lessen the severity of sickle cell disease (SCD), through reductions in peripheral vaso-occlusive disease and reduced risk for cerebrovascular events. However, the influence of HbF on oxygen delivery to high metabolism tissues like the brain, or its influence on cerebral perfusion, metabolism, inflammation or function have not been widely studied. We employed a Berkley mouse model (BERK) of SCD with gamma transgenes q3 expressing exclusively human α- and β^S-globins with varying levels of γ globin expression to investigate the effect of HbF expression on the brain using magnetic resonance imaging (MRI), MRI diffusion tensor imaging (DTI) and spectroscopy (MRS) and hematological parameters. Hematological parameters improved with increasing γ level expression, as did markers for brain metabolism, perfusion and inflammation. Brain microstructure assessed by DTI fractional anisotropy improved, while myo-inositol levels increased, suggesting improved microstructural integrity and reduced cell loss. Our results suggest that increasing γ levels not only improves sickle peripheral disease, but also improves brain perfusion and oxygen delivery while reducing brain inflammation while protecting brain microstructural integrity.

Water and Collagen Content Are High in Pancreatic Cancer: Implications for Quantitative Metabolic Imaging

In magnetic resonance metabolic imaging, signal from the water content is frequently used for normalization to derive quantitative or semi-quantitative values of metabolites in vivo or ex vivo tumors and tissues. Ex vivo high-resolution metabolic characterization of tumors with magnetic resonance spectroscopy (MRS) provides valuable information that can be used to drive the development of noninvasive MRS biomarkers and to identify metabolic therapeutic targets. Variability in the water content between tumor and normal tissue can result in over or underestimation of metabolite concentrations when assuming a constant water content. Assuming a constant water content can lead to masking of differences between malignant and normal tissues both in vivo and ex vivo. There is a critical need to develop biomarkers to detect pancreatic cancer and to develop novel treatments. Our purpose here was to determine the differences in water content between pancreatic tumors and normal pancreatic tissue as well as other organs to accurately quantify metabolic differences when using the water signal for normalization. Our data identify the importance of factoring the differences in water content between tumors and organs. High-resolution proton spectra of tumors and pancreatic tissue extracts normalized to the water signal, assuming similar water content, did not reflect the significantly increased total choline observed in tumors in vivo without factoring the differences in water content. We identified significant differences in the collagen 1 content between Panc1 and BxPC3 pancreatic tumors and the pancreas that can contribute to the differences in water content that were observed.

AAVP displaying octreotide for ligand-directed therapeutic transgene delivery in neuroendocrine tumors of the pancreas

Patients with inoperable or unresectable pancreatic neuroendocrine tumors (NETs) have limited treatment options. These rare human tumors often express somatostatin receptors (SSTRs) and thus are clinically responsive to certain relatively stable somatostatin analogs, such as octreotide. Unfortunately, however, this tumor response is generally short-lived. Here we designed a hybrid adeno-associated virus and phage (AAVP) vector displaying biologically active octreotide on the viral surface for ligand-directed delivery, cell internalization, and transduction of an apoptosis-promoting tumor necrosis factor (TNF) transgene specifically to NETs. These functional attributes of AAVP-TNF particles displaying the octreotide peptide motif (termed Oct-AAVP-TNF) were confirmed in vitro, in SSTR type 2-expressing NET cells, and in vivo using cohorts of pancreatic NET-bearing Men1 tumor-suppressor gene KO mice, a transgenic model of functioning (i.e., insulin-secreting) tumors that genetically and clinically recapitulates the human disease. Finally, preclinical imaging and therapeutic experiments with pancreatic NET-bearing mice demonstrated that Oct-AAVP-TNF lowered tumor metabolism and insulin secretion, reduced tumor size, and improved mouse survival. Taken together, these proof-of-concept results establish Oct-AAVP-TNF as a strong therapeutic candidate for patients with NETs of the pancreas. More broadly, the demonstration that a known, short, biologically active motif can direct tumor targeting and receptor-mediated internalization of AAVP particles may streamline the potential utility of myriad other short peptide motifs and provide a blueprint for therapeutic applications in a variety of cancers and perhaps many nonmalignant diseases as well.

Brain maturation in neonatal rodents is impeded by sevoflurane anesthesia

BACKGROUND

A wealth of data shows neuronal demise after general anesthesia in the very young rodent brain. Herein, the authors apply proton magnetic resonance spectroscopy (1HMRS), testing the hypothesis that neurotoxic exposure during peak synaptogenesis can be tracked via changes in neuronal metabolites.

METHODS

1HMRS spectra were acquired in the brain (thalamus) of neonatal rat pups 24 and 48 h after sevoflurane exposure on postnatal day (PND) 7 and 15 and in unexposed, sham controls. A repeated measure ANOVA was performed to examine whether changes in metabolites were different between exposed and unexposed groups. Sevoflurane-induced neurotoxicity on PND7 was confirmed by immunohistochemistry.

RESULTS

In unexposed PND7 pups (N = 21), concentration of N-acetylaspartate (NAA; [NAA]) increased by 16% from PND8 to PND9, whereas in exposed PND7 pups (N = 19), [NAA] did not change and concentration of glycerophosphorylcholine and phosphorylcholine ([GPC + PCh]) decreased by 25%. In PND15 rats, [NAA] increased from PND16 to PND17 for both the exposed (N = 14) and the unexposed (N = 16) groups. Two-way ANOVA for PND7 pups demonstrated that changes over time observed in [NAA] (P = 0.031) and [GPC + PCh] (P = 0.024) were different between those two groups.

CONCLUSIONS

The authors demonstrated that normal [NAA] increase from PND8 to PND9 was impeded in sevoflurane-exposed rats when exposed at PND7; however, not impeded when exposed on PND15. Furthermore, the authors showed that noninvasive 1HMRS is sufficiently sensitive to detect subtle differences in developmental time trajectory of [NAA]. This is potentially clinically relevant because 1HMRS can be applied across species and may be useful in providing evidence of neurotoxicity in the human neonatal brain.