Preclinical MR fingerprinting (MRF) at 7 T: effective quantitative imaging for rodent disease models.

High-field preclinical MRI scanners are now commonly used to quantitatively assess disease status and the efficacy of novel therapies in a wide variety of rodent models. Unfortunately, conventional MRI methods are highly susceptible to respiratory and cardiac motion artifacts resulting in potentially inaccurate and misleading data. We have developed an initial preclinical 7.0-T MRI implementation of the highly novel MR fingerprinting (MRF) methodology which has been described previously for clinical imaging applications. The MRF technology combines a priori variation in the MRI acquisition parameters with dictionary-based matching of acquired signal evolution profiles to simultaneously generate quantitative maps of T1 and T2 relaxation times and proton density. This preclinical MRF acquisition was constructed from a fast imaging with steady-state free precession (FISP) MRI pulse sequence to acquire 600 MRF images with both evolving T1 and T2 weighting in approximately 30 min. This initial high-field preclinical MRF investigation demonstrated reproducible and differentiated estimates of in vitro phantoms with different relaxation times. In vivo preclinical MRF results in mouse kidneys and brain tumor models demonstrated an inherent resistance to respiratory motion artifacts as well as sensitivity to known pathology. These results suggest that MRF methodology may offer the opportunity for the quantification of numerous MRI parameters for a wide variety of preclinical imaging applications.

Differential regulation of high glucose-induced glyceraldehyde-3-phosphate dehydrogenase nuclear accumulation in Müller cells by IL-1beta and IL-6.

PURPOSE: This study determined the role of the proinflammatory cytokines known to be elevated in the diabetic retina, namely IL-1beta, TNFalpha, and IL-6, in a high glucose-induced nuclear accumulation of GAPDH in retinal Müller cells, an event considered crucial for the induction of cell death. METHODS: With use of the transformed rat Müller cell line (rMC-1) and isolated human Müller cells (HMCs), the authors examined the effect of high glucose (25 mM), IL-1beta, TNFalpha, IL-6, and high glucose (25 mM) plus inhibitors of the caspase-1/IL-1beta signaling pathway on GAPDH nuclear accumulation, which was evaluated by immunofluorescence analysis. RESULTS: High glucose induced IL-1beta, weak IL-6, and no TNFalpha production by rMC-1 and HMCs. IL-1beta (1-10 ng/mL) significantly increased GAPDH nuclear accumulation in Müller cells in a concentration-dependent manner within 24 hours. Further, high glucose-induced GAPDH nuclear accumulation in Müller cells was mediated by IL-1beta. Inhibition of the IL-1 receptor using an IL-1 receptor antagonist (IL-1ra; 50 ng/mL) or inhibition of IL-1beta production using a specific caspase-1 inhibitor (YVAD-fmk; 100 microM) significantly decreased high glucose-induced GAPDH nuclear accumulation. In contrast, IL-6 (2 ng/mL) had a strong protective effect attenuating high glucose and IL-1beta-induced GAPDH nuclear accumulation in Müller cells. TNFalpha (1-10 ng/mL) did not have any effect on GAPDH nuclear accumulation. CONCLUSIONS: These results revealed a novel mechanism for high glucose-induced GAPDH nuclear accumulation in Müller cells through production and autocrine stimulation by IL-1beta. The protective role of IL-6 in high glucose- and IL-1beta-induced toxicity indicates that changes in the balance of these cytokines might contribute to cellular damage mediated by elevated glucose levels.

Inhibition of caspase-1/interleukin-1beta signaling prevents degeneration of retinal capillaries in diabetes and galactosemia.

The proinflammatory cytokine, interleukin (IL)-1beta, is known to induce vascular dysfunction and cell death. We investigated the role of IL-1beta and caspase-1 (the enzyme that produces it) in diabetes-induced degeneration of retinal capillaries. Caspase-1 activity is increased in retinas of diabetic and galactosemic mice and diabetic patients. First, we investigated the effect of agents known to inhibit caspase-1 (minocycline and tetracycline) on IL-1beta production and retinal capillary degeneration in diabetic and galactose-fed mice. Second, we examined the effect of genetic deletion of the IL-1beta receptor on diabetes-induced caspase activities and retinal capillary degeneration. Diabetic and galactose-fed mice were injected intraperitoneally with minocycline or tetracycline (5 mg/kg). At 2 months of diabetes, minocycline inhibited hyperglycemia-induced caspase-1 activity and IL-1beta production in the retina. Long-term administration of minocycline prevented retinal capillary degeneration in diabetic (6 months) and galactose-fed (13 months) mice. Tetracycline inhibited hyperglycemia-induced caspase-1 activity in vitro but not in vivo. Mice deficient in the IL-1beta receptor were protected from diabetes-induced caspase activation and retinal pathology at 7 months of diabetes. These results indicate that the caspase-1/IL-1beta signaling pathway plays an important role in diabetes-induced retinal pathology, and its inhibition might represent a new strategy to inhibit capillary degeneration in diabetic retinopathy.