Three-Dimensional In vivo Magnetic Resonance Imaging (MRI) of Mouse Facial Nerve Regeneration

MRI (magnetic resonance imaging) is an indispensable tool in the diagnosis of centrals nervous system (CNS) disorders such as spinal cord injury and multiple sclerosis (MS). In contrast, diagnosis of peripheral nerve injuries largely depends on clinical and electrophysiological parameters. Thus, currently MRI is not regularly used which in part is due to small nerve calibers and isointensity with surrounding tissue such as muscles. In this study we performed translational MRI research in mice to establish a novel MRI protocol visualizing intact and injured peripheral nerves in a non-invasive manner without contrast agents. With this protocol we were able to image even very small nerves and nerve branches such as the mouse facial nerve (diameter 100–300 μm) at highest spatial resolution. Analysis was performed in the same animal in a longitudinal study spanning 3 weeks after injury. Nerve injury caused hyperintense signal in T2-weighted images and an increase in nerve size of the proximal and distal nerve stumps were observed. Further hyperintense signal was observed in a bulb-like structure in the lesion site, which correlated histologically with the production of fibrotic tissue and immune cell infiltration. The longitudinal MR representation of the facial nerve lesions correlated well with physiological recovery of nerve function by quantifying whisker movement. In summary, we provide a novel protocol in rodents allowing for non-invasive, non-contrast agent enhanced, high-resolution MR imaging of small peripheral nerves longitudinally over several weeks. This protocol might further help to establish MRI as an important diagnostic and post-surgery follow-up tool to monitor peripheral nerve injuries in humans

Keratin 17 Gene Expression during the Murine Hair Cycle

Keratin 17 (K17) expression is currently considered to be associated with hyperplastic or malignant growth of epithelial cells. The functions of this keratin in normal skin physiology and the regulation of its gene expression, however, are still unclear. As one possible approach to further explore K17 functions, we have studied the differential patterns of mouse K17 (MK17) transcription during the murine hair cycle by means of in situ hybridization, using a digoxigenin-labeled riboprobe. Cycling hair follicles in the skin of C57BL/6 mice were found to be the only skin structures expressing MK17 under physiologic conditions. MK17 transcripts were constantly observed throughout all hair cycle stages in the suprainfundibular outer root sheath (ORS). The MK17 expression was also evident in the isthmus part of the ORS, where it was expressed weakly and was spatially restricted during telogen, with an increase in early anagen and stable expression during mid- and late anagen, localizing to the zone of so-called trichilemmal keratinization. In addition, in early anagen, a group of epithelial cells in or next to the bulge region stained weakly for MK17. With progressing anagen development, MK17 expression in this region increased and was consistently localized to keratinocytes at the advancing front of the emerging epithelial hair bulb. In mid- and late anagen, this zone of MK17 expression spread along the proximal ORS, with a maximal level of expression in the innermost cell layer of the ORS. Overall, these findings provide data on the MK17 expression profile of normal murine skin and demonstrate hair-cycle–dependent regulation of MK17 expression

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) Affects Keratin 1 and Keratin 17 Gene Expression and Differentially Induces Keratinization in Hairless Mouse Skin

The environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes chloracne in humans by mechanisms that are as yet poorly understood. Because TCDD is known to affect keratinocyte differentiation in vitro, we have studied TCDD-dependent morphologic changes and the expression of murine keratin I (MK1; differentiation associated) and keratin 17 (MK17; presumably hyperproliferation associated) in HRS/J hr/hr hairless mouse skin. TCDD (0.2 μg in acetone) applied topically to the dorsal skin caused epidermal acanthosis and hyperkeratosis of the dermal cysts as well as an involution of the utricles and the sebaceous glands. By means of in situ hybridization with digoxigenin-labeled riboprobes of sections from untreated and vehicle (control)-treated skin, we localized MK1 mRNA to the epidermal spinous cell compartment. MK17 transcripts were detected only in the derivatives of the hair follicleutricle epithelium and dermal cysts. No spatial overlap was observed between MK1 and MK17 expression. After TCDD application, MK17 was newly expressed in the upper spinous cell layers of the interfollicular epidermis, although it was suppressed in the involuting utricles. In contrast, MK1 expression in the interfollicular epidermis was not affected by TCDD. Furthermore, MK1 expression was induced in the epithelium of the utricle remnants and in some dermal cysts. These data suggest that increased keratinization of the part of the follicular epithelium corresponding to the dermal cyst epithelium of hairless mice most probably explains the pathogenesis of TCDD-induced chloracne. The results demonstrate, furthermore, that TCDD can differentially affect keratinocyte differentiation in vivo as well as in vitro

The FTLD Risk Factor TMEM106B Regulates the Transport of Lysosomes at the Axon Initial Segment of Motoneurons

Genetic variations in TMEM106B, coding for a lysosomal membrane protein, affect frontotemporal lobar degeneration (FTLD) in GRN- (coding for progranulin) and C9orf72-expansion carriers and might play a role in aging. To determine the physiological function of TMEM106B, we generated TMEM106B-deficient mice. These mice develop proximal axonal swellings caused by drastically enlarged LAMP1-positive vacuoles, increased retrograde axonal transport of lysosomes, and accumulation of lipofuscin and autophagosomes. Giant vacuoles specifically accumulate at the distal end and within the axon initial segment, but not in peripheral nerves or at axon terminals, resulting in an impaired facial-nerve-dependent motor performance. These data implicate TMEM106B in mediating the axonal transport of LAMP1-positive organelles in motoneurons and axonal sorting at the initial segment. Our data provide mechanistic insight into how TMEM106B affects lysosomal proteolysis and degradative capacity in neurons.status: publishe

The FTLD Risk Factor TMEM106B Regulates the Transport of Lysosomes at the Axon Initial Segment of Motoneurons

Genetic variations in TMEM106B, coding for a lysosomal membrane protein, affect frontotemporal lobar degeneration (FTLD) in GRN- (coding for progranulin) and C9orf72-expansion carriers and might play a role in aging. To determine the physiological function of TMEM106B, we generated TMEM106B-deficient mice. These mice develop proximal axonal swellings caused by drastically enlarged LAMP1-positive vacuoles, increased retrograde axonal transport of lysosomes, and accumulation of lipofuscin and autophagosomes. Giant vacuoles specifically accumulate at the distal end and within the axon initial segment, but not in peripheral nerves or at axon terminals, resulting in an impaired facial-nerve-dependent motor performance. These data implicate TMEM106B in mediating the axonal transport of LAMP1-positive organelles in motoneurons and axonal sorting at the initial segment. Our data provide mechanistic insight into how TMEM106B affects lysosomal proteolysis and degradative capacity in neurons

The effect of spironolactone on diastolic function in haemodialysis patients

Heart failure with preserved ejection fraction (HFpEF) is highly prevalent in patients on maintenance haemodialysis (HD) and lacks effective treatment. We investigated the effect of spironolactone on cardiac structure and function with a specific focus on diastolic function parameters. The MiREnDa trial examined the effect of 50 mg spironolactone once daily versus placebo on left ventricular mass index (LVMi) among 97 HD patients during 40 weeks of treatment. In this echocardiographic substudy, diastolic function was assessed using predefined structural and functional parameters including E/e'. Changes in the frequency of HFpEF were analysed using the comprehensive 'HFA-PEFF score'. Complete echocardiographic assessment was available in 65 individuals (59.5 ± 13.0 years, 21.5% female) with preserved left ventricular ejection fraction (LVEF > 50%). At baseline, mean E/e' was 15.2 ± 7.8 and 37 (56.9%) patients fulfilled the criteria of HFpEF according to the HFA-PEFF score. There was no significant difference in mean change of E/e' between the spironolactone group and the placebo group (+ 0.93 ± 5.39 vs. + 1.52 ± 5.94, p = 0.68) or in mean change of left atrial volume index (LAVi) (1.9 ± 12.3 ml/