Natural killer cells attenuate cytomegalovirus-induced hearing loss in mice

<div><p>Congenital cytomegalovirus (CMV) infection is the most common non-hereditary cause of sensorineural hearing loss (SNHL) yet the mechanisms of hearing loss remain obscure. Natural Killer (NK) cells play a critical role in regulating murine CMV infection via NK cell recognition of the Ly49H cell surface receptor of the viral-encoded m157 ligand expressed at the infected cell surface. This Ly49H NK receptor/m157 ligand interaction has been found to mediate host resistance to CMV in the spleen, and lung, but is much less effective in the liver, so it is not known if this interaction is important in the context of SNHL. Using a murine model for CMV-induced labyrinthitis, we have demonstrated that the Ly49H/m157 interaction mediates host resistance in the temporal bone. BALB/c mice, which lack functional Ly49H, inoculated with mCMV at post-natal day 3 developed profound hearing loss and significant outer hair cell loss by 28 days of life. In contrast, C57BL/6 mice, competent for the Ly49H/m157 interaction, had minimal hearing loss and attenuated outer hair cell loss with the same mCMV dose. Administration of Ly49H blocking antibody or inoculation with a mCMV viral strain deleted for the m157 gene rendered the previously resistant C57BL/6 mouse strain susceptible to hearing loss to a similar extent as the BALB/c mouse strain indicating a direct role of the Ly49H/m157 interaction in mCMV-dependent hearing loss. Additionally, NK cell recruitment to sites of infection was evident in the temporal bone of inoculated susceptible mouse strains. These results demonstrate participation of NK cells in protection from CMV-induced labyrinthitis and SNHL in mice.</p></div

A conscious mouse model of gastric ileus using clinically relevant endpoints

BACKGROUND: Gastric ileus is an unsolved clinical problem and current treatment is limited to supportive measures. Models of ileus using anesthetized animals, muscle strips or isolated smooth muscle cells do not adequately reproduce the clinical situation. Thus, previous studies using these techniques have not led to a clear understanding of the pathophysiology of ileus. The feasibility of using food intake and fecal output as simple, clinically relevant endpoints for monitoring ileus in a conscious mouse model was evaluated by assessing the severity and time course of various insults known to cause ileus. METHODS: Delayed food intake and fecal output associated with ileus was monitored after intraperitoneal injection of endotoxin, laparotomy with bowel manipulation, thermal injury or cerulein induced acute pancreatitis. The correlation of decreased food intake after endotoxin injection with gastric ileus was validated by measuring gastric emptying. The effect of endotoxin on general activity level and feeding behavior was also determined. Small bowel transit was measured using a phenol red marker. RESULTS: Each insult resulted in a transient and comparable decrease in food intake and fecal output consistent with the clinical picture of ileus. The endpoints were highly sensitive to small changes in low doses of endotoxin, the extent of bowel manipulation, and cerulein dose. The delay in food intake directly correlated with delayed gastric emptying. Changes in general activity and feeding behavior were insufficient to explain decreased food intake. Intestinal transit remained unchanged at the times measured. CONCLUSION: Food intake and fecal output are sensitive markers of gastric dysfunction in four experimental models of ileus. In the mouse, delayed gastric emptying appears to be the major cause of the anorexic effect associated with ileus. Gastric dysfunction is more important than small bowel dysfunction in this model. Recovery of stomach function appears to be simultaneous to colonic recovery

β-catenin is selectively required for the expansion and regeneration of mature pancreatic acinar cells in mice

The size of the pancreas is determined by intrinsic factors, such as the number of progenitor cells, and by extrinsic signals that control the fate and proliferation of those progenitors. Both the exocrine and endocrine compartments of the pancreas undergo dramatic expansion after birth and are capable of at least partial regeneration following injury. Whether the expansion of these lineages relies on similar mechanisms is unknown. Although we have shown that the Wnt signaling component β-catenin is selectively required in mouse embryos for the generation of exocrine acinar cells, this protein has been ascribed various functions in the postnatal pancreas, including proliferation and regeneration of islet as well as acinar cells. To address whether β-catenin remains important for the maintenance and expansion of mature acinar cells, we have established a system to follow the behavior and fate of β-catenin-deficient cells during postnatal growth and regeneration in mice. We find that β-catenin is continuously required for the establishment and maintenance of acinar cell mass, extending from embryonic specification through juvenile and adult self-renewal and regeneration. This requirement is not shared with islet cells, which proliferate and function normally in the absence of β-catenin. These results make distinct predictions for the relative role of Wnt–β-catenin signaling in the etiology of human endocrine and exocrine disease. We suggest that loss of Wnt–β-catenin activity is unlikely to drive islet dysfunction, as occurs in type 2 diabetes, but that β-catenin is likely to promote human acinar cell proliferation following injury, and might therefore contribute to the resolution of acute or chronic pancreatitis

Early Life Inflammation and the Developing Hematopoietic and Immune Systems: The Cochlea as a Sensitive Indicator of Disruption

Emerging evidence indicates that perinatal infection and inflammation can influence the developing immune system and may ultimately affect long-term health and disease outcomes in offspring by perturbing tissue and immune homeostasis. We posit that perinatal inflammation influences immune outcomes in offspring by perturbing (1) the development and function of fetal-derived immune cells that regulate tissue development and homeostasis, and (2) the establishment and function of developing hematopoietic stem cells (HSCs) that continually generate immune cells across the lifespan. To disentangle the complexities of these interlinked systems, we propose the cochlea as an ideal model tissue to investigate how perinatal infection affects immune, tissue, and stem cell development. The cochlea contains complex tissue architecture and a rich immune milieu that is established during early life. A wide range of congenital infections cause cochlea dysfunction and sensorineural hearing loss (SNHL), likely attributable to early life inflammation. Furthermore, we show that both immune cells and bone marrow hematopoietic progenitors can be simultaneously analyzed within neonatal cochlear samples. Future work investigating the pathogenesis of SNHL in the context of congenital infection will therefore provide critical information on how perinatal inflammation drives disease susceptibility in offspring

Global expression profiling identifies a novel biosignature for protein aggregation R120GCryAB cardiomyopathy in mice

Protein aggregation cardiomyopathy is a life-threatening manifestation of a multisystem disorder caused by the exchange mutation in the gene encoding the human small heat shock protein αB-crystallin (hR120GCryAB). Genetic studies in mice have established cardiac hR120GCryAB expression causes increased activity of glucose 6-phosphate dehydrogenase (G6PD) and “reductive stress” (Rajasekaran et al., Cell 130: 427–439, 2007). However, the initiating molecular events in the pathogenesis of this novel toxic gain-of-function mechanism remain poorly defined. In an integrated systems approach using gene expression profiling, we identified a “biosignature,” whose features can be validated to predict the onset, rate of progression, and clinical outcome of R120GCryAB cardiomyopathy. At the 3 mo disease-related but compensated stage, we demonstrate that transcripts were only upregulated in three distinct pathways: stress response (e.g., Hsp70, Hsp90), glutathione metabolism (Gpx1, Gpx3, glutathione S-transferase), and complement and coagulation cascades in hR120GCryAB transgenic mouse hearts compared with either hCryAB WT transgenic mice or nontransgenic controls. In 6 mo old myopathic hearts, ribosomal synthesis and cellular remodeling associated with increased cardiac hypertrophy were additional upregulated pathways. In contrast, the predominant downregulated pathways were for oxidative phosphorylation, fatty acid metabolism, intermediate metabolism, and energetic balance, supporting their primary pathogenic roles by which G6PD-dependent reductive stress causes cardiac decompensation and overt heart failure in hR120GCryAB cardiomyopathy. This study extends and confirms our previous findings that reductive stress is a causal mechanism for hR120G CryAB cardiomyopathy and demonstrates that alteration in glutathione pathway gene expression is an early biosignature with utility for presymptomatic detection

An Evaluation of the Drug Permeability Properties of Human Cadaveric In Situ Tympanic and Round Window Membranes

It is estimated that hearing loss currently affects more than 1.5 billion people, or approximately 20% of the global population; however, presently, there are no Food and Drug Administration-approved therapeutics or prophylactics for this condition. While continued research on the development of otoprotective drugs to target this clear unmet need is an obvious path, there are numerous challenges to translating promising therapeutic candidates into human clinical testing. The screening of promising drug candidates relies exclusively on preclinical models. Current models do not permit the rapid high-throughput screening of promising drug candidates, and their relevance to clinical scenarios is often ambiguous. With the current study, we seek to understand the drug permeability properties of the cadaveric tympanic and round window membranes with the goal of generating knowledge that could inform the design and/or evaluation of in vitro organotypic models. The development of such models could enable the early high-throughput screening of topical therapeutic candidates and should address some of the limitations of currently used animal models