Stem cell therapy in the inner ear: recent achievements and prospects

Because of its high prevalence and social impact, hearing impairment is a major public health problem. Whatever the cause--heredity, acoustic trauma, aminoglycoside antibiotics, noise exposure or aging--the hearing impairment is often caused by an irreversible loss of sensory hair cells. So far, hearing aids and cochlear implants are the only possibility to "treat" profound deafness. With the advent of regenerative medicine, extensive studies aimed to repair, regenerate or replace lost hair cells have been initiated. Recently, Stefan Heller and colleagues described a guidance protocol to induce mouse embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) to differentiate into mechanosensitive hair cells. The resulting hair cells hold promise as a tool for hair cell molecular physiology and physiopathology, drug discovery, and possibly also hair cell replacement. The next challenges, alternative strategies, their limitations and prospects are also discussed.     

Characterization of ochratoxin A-induced apoptosis in primary rat hepatocytes

The main target organ of the mycotoxin ochratoxin A (OTA) in mammals is the kidney but OTA has also been shown to be hepatotoxic in rats and to induce tumors in mouse liver. Even at very low concentrations, OTA causes perturbations of cellular signaling pathways as well as enhanced apoptosis. OTA has been extensively studied in kidney cell systems. Since this substance also affects liver health, we focused our work on apoptosis-related events induced by OTA in primary rat hepatocytes. We performed pathway-specific polymerase chain reaction arrays to assess the expression of genes involved in apoptosis. Treatment with 1 μM OTA for 24 h caused marked changes in apoptosis-related gene expression. Genes as apaf1, bad, caspase 7, polb (DNA polymerase beta, performs base excision repair), and p53, which are marker genes for DNA damage, were upregulated. FAS and faslg were also markedly induced by treatment with OTA. Treatment of hepatocytes with OTA led to a concentration-dependent inhibition of protein biosynthesis. Apoptosis-inducing factor was released from mitochondria following OTA treatment; the mycotoxin induced the activity of caspases 8, 9, and 3/7 and caused chromatin condensation and fragmentation. Caspase inhibition led to a significant but not complete reduction of OTA-induced apoptosis. Our data suggest that not only OTA leads to p53-dependent apoptosis in rat hepatocytes but it also hints to other mechanisms, independent of caspase activation or protein biosynthesis, being involved.     

Urinary tract abnormalities in Chinese rural children who consumed melamine-contaminated dairy products: a population-based screening and follow-up study

Background

Kidney damage related to consumption of melamine-contaminated dairy products by young children in China has been described. However, no studies have reported on the population-based prevalence of kidney damage among exposed children or on the condition of affected children after follow-up.

Methods

We conducted an ultrasound-based screening in September 2008 of 7933 children younger than 36 months of age who lived in a rural area in China where the dairy products most highly contaminated with melamine were sold. We monitored children who had evidence of nephrolithiasis or hydronephrosis at screening using renal ultrasonography after one, three and six months. We also collected information from the mothers of affected children about consumption of melamine-contaminated products between June and August 2008.

Results

The overall prevalence of urinary tract abnormalities among screened children was 0.61% (95% confidence interval [CI] 0.45%–0.80%). The mean exposure dose of melamine was estimated to be 116 (range 36–220) mg per day. Of the 48 affected children, 43 (89.6%) were asymptomatic, 2 had symptoms and were hospitalized, and 3 had symptoms but treatment had been not sought for them. Of the 46 children for whom six-month follow-up information was available, renal abnormalities persisted in 5 children and resolved in the remaining 41.

Interpretation

Among children who underwent screening, 0.61% showed ultrasonographic evidence of nephrolithiasis or hydronephrosis. Most of the affected children were asymptomatic. The majority of the affected children recovered from the toxic effects of melamine over time without specific treatment. Renal abnormalities remained in 12% of the affected children.Contamination of dairy products with melamine in China has resulted in a widespread outbreak of serious kidney damage in children.^1–4 On Sept. 12, 2008, the Chinese government announced to the public that the outbreak had occurred and initiated various emergency responses, including the set-up of a high-level national coordinating group, free screening and treatment of affected children, thorough inspection of all dairy products and producers, timely release of information to the public, recalls of contaminated products, suspension of production of the contaminated milk and compensation to the families of affected children. More than 50 000 children have been hospitalized and six have died because of kidney damage.⁵Melamine is a nitrogen-containing compound commonly used in chemical industry. Because its addition to milk elevates apparent protein content, raw milk was intentionally adulterated with melamine in the production-chain, leading to contamination of dairy products and high-level exposure of thousands of children.⁶Melamine is known to cause formation of calculi in weanling rats and has led to acute renal failure in cats and dogs consuming melamine-contaminated pet foods.^7,8 In humans, melamine-related disease has been recognized only recently, and the full adverse effects of exposure remain unknown.^4,9 A clinicopathologic study suggests that the size of urinary stones is related to melamine concentration.⁹ A recent hospital-based study in Beijing reported the prevalence of nephrolithiasis was 8.5% among children who were exposed and referred by other hospitals.¹⁰However, no studies have reported on the population-based prevalence of kidney disease among exposed children, nor have follow-up reports been released about affected children. We performed a population-based screening and follow-up study involving residents of a rural area situated close to the manufacturer of Sanlu dairy products, which was the source of the most severely melamine-contaminated products in the mainland of China.¹¹ The study was approved by the Institutional Review Board of Peking University.     

Multicentre prospective validation of use of the Canadian C-Spine Rule by triage nurses in the emergency department

Objectives

The Canadian C-Spine Rule for imaging of the cervical spine was developed for use by physicians. We believe that nurses in the emergency department could use this rule to clinically clear the cervical spine. We prospectively evaluated the accuracy, reliability and acceptability of the Canadian C-Spine Rule when used by nurses.

Methods

We conducted this three-year prospective cohort study in six Canadian emergency departments. The study involved adult trauma patients who were alert and whose condition was stable. We provided two hours of training to 191 triage nurses. The nurses then assessed patients using the Canadian C-Spine Rule, including determination of neck tenderness and range of motion, reapplied immobilization and completed a data form.

Results

Of the 3633 study patients, 42 (1.2%) had clinically important injuries of the cervical spine. The kappa value for interobserver assessments of 498 patients with the Canadian C-Spine Rule was 0.78. We calculated sensitivity of 100.0% (95% confidence interval [CI] 91.0%–100.0%) and specificity of 43.4% (95% CI 42.0%–45.0%) for the Canadian C-Spine Rule as interpreted by the investigators. The nurses classified patients with a sensitivity of 90.2% (95% CI 76.0%–95.0%) and a specificity of 43.9% (95% CI 42.0%–46.0%). Early in the study, nurses failed to identify four cases of injury, despite the presence of clear high-risk factors. None of these patients suffered sequelae, and after retraining there were no further missed cases. We estimated that for 40.7% of patients, the cervical spine could be cleared clinically by nurses. Nurses reported discomfort in applying the Canadian C-Spine Rule in only 4.8% of cases.

Conclusion

Use of the Canadian C-Spine Rule by nurses was accurate, reliable and clinically acceptable. Widespread implementation by nurses throughout Canada and elsewhere would diminish patient discomfort and improve patient flow in overcrowded emergency departments.Each year, Canadian emergency departments treat 1.3 million patients who have suffered blunt trauma from falls or motor vehicle collisions and who are at risk for injury of the cervical spine.¹ Most of these cases involve adults who are alert and in stable condition, and less than 1% involve fracture of the cervical spine.² Most trauma patients who have been transported in ambulances are protected by a backboard, collar and neck supports. Nurses are responsible for initial triage in the emergency department and usually send such patients to high-acuity resuscitation rooms, where they may remain fully immobilized for hours until assessment by a physician and radiography are complete. This prolonged immobilization is often unnecessary and adds considerably to patient discomfort. The delay also adds to the burden of overcrowded Canadian emergency departments in an era when they are under unprecedented pressures.^3–5 These patients occupy valuable space in resuscitation rooms, and repeated efforts to obtain satisfactory radiographs or computed tomography scans of the cervical spine use valuable time on the part of physicians, nurses and technicians.A clinical decision rule is defined as a decision-making tool incorporating three or more variables from the patient’s history, a physical examination or simple tests. Such rules are derived from original research and help clinicians with diagnostic or therapeutic decisions at the bedside. We previously developed a clinical decision rule for evaluation of the cervical spine.^6,7 The Canadian C-Spine Rule comprises simple clinical variables (Figure 1) and was designed to allow clinicians to “clear” immobilization of the cervical spine (i.e., remove neck collar and other devices) without radiography and to decrease immobilization times.⁸ We also validated the accuracy of the rule when used by physicians.⁹ We recently completed an implementation trial at 12 Canadian hospitals to evaluate the impact on patient care and outcomes of the Canadian C-Spine Rule when used by physicians.¹⁰Open in a separate windowFigure 1The Canadian C-Spine Rule to rule out cervical spine injury, adapted for use by nurses. The rule is intended for patients who have experienced trauma, who are alert (score on Glasgow Coma Scale = 15) and whose condition is stable. *The following mechanisms of injury were defined as dangerous: fall from elevation of more than 3 ft (91 cm) or five stairs, axial load to the head (e.g., diving injury), motor vehicle collision at high speed (> 100 km/h), motor vehicle collision involving a rollover or ejection, injury involving a motorized recreational vehicle, bicycle-related injury (rider struck or collision). †Simple rear-end motor vehicle collisions exclude incidents in which the patient was pushed into oncoming traffic or was hit by a bus, large truck or vehicle travelling at high speed, as well as rollovers; all such incidents would be considered high risk. ‡Neck pain with delayed onset is any pain that did not occur immediately following the precipitating incident. Adapted, with permission, from Stiell IG, Wells GA, Vandemheen K, et al. The Canadian Cervical Spine Radiography Rule for alert and stable trauma patients. JAMA 2001;286:1841–8.⁸ Copyright © 2001 American Medical Association. All rights reserved.Nurses in the emergency department usually do not evaluate the cervical spine of trauma patients, and they routinely send all immobilized patients to the emergency department’s resuscitation room. We believe that nurses could safely evaluate alert patients who have arrived by ambulance and whose condition is stable and could “clear” immobilization of the cervical spine of low-risk patients upon arrival at the triage station.¹¹ Patients could then be much more rapidly, comfortably and efficiently managed in other areas of the emergency department. An expanded decision-making role for nurses has the potential to improve the efficiency of trauma care in all Canadian hospitals. Very little research has been done to determine the ability of nurses to clear immobilization of the cervical spine.^12–15 Our objective in this study was to prospectively evaluate the accuracy, reliability and acceptability of the Canadian C-Spine Rule when used by nurses to assess patients’ need for immobilization.     

A Combination of Fertility Signals and Aggression Regulates Reproduction in the Ant <Emphasis Type="Italic">Gnamptogenys striatula</Emphasis>

Approximately 150 ant species are facultatively or obligately queenless whereby mated workers assume the role of the queen. In many of these species a reproductive dominance hierarchy is established by way of aggressive interactions. Top-ranking workers, which are typically the most fecund, acquire a characteristic cuticular hydrocarbon profile. We studied the temporal dynamics of this chemical change and associated interplay with observed aggressive interactions in an experimentally orphaned colony of the facultatively queenless ant Gnamptogenys striatula. Our observations and chemical analyses demonstrate that chemical fertility signals played a major role in the establishment of a dominance hierarchy and aggression settled dominance relationships only when ants had identical hydrocarbon profiles. Moreover, individuals with a higher potential fertility, in this experiment reflected in a higher ovariole number, are shown to have a better chance of becoming a reproductive.     

Mitochondrial retention of Opa1 is required for mouse embryogenesis

Mitochondria are dynamic cellular organelles that balance fission and fusion to regulate organelle morphology, distribution, and activity, and Opa1 is one of three GTPases known to regulate mitochondrial fusion. In humans, loss of a single Opa1 allele causes dominant optic atrophy, a degenerative condition that leads to loss of vision. Here we demonstrate that the lilR3 mutant mouse phenotype is due to a point mutation in the Opa1 gene resulting in mislocalized Opa1 protein from the mitochondria to the cytosol. Importantly, the mutation is in the middle domain of the Opa1 protein, for which no function had been described. Lack of mitochondrial retention of Opa1 is sufficient to cause the cellular Opa1 loss-of-function phenotype as the mitochondria are fragmented, indicating an inability to fuse. Despite the normally ubiquitous expression of Opa1 and the essential nature of mitochondria, embryos with aberrant Opa1 survived through midgestation and died at E11.5. These mutants displayed growth retardation, exencephaly, and abnormal patterning along the anterior-posterior axis, although the A–P axis itself was intact. The complex relationship between mitochondrial dynamics and cell death is emphasized by apoptosis in specific cell populations of lilR3 embryos. Our results define, for the first time, a function of the middle domain of the Opa1 protein and demonstrate that mitochondrial retention of Opa1 protein is essential for normal embryogenesis.     

The BCCT family of carriers: from physiology to crystal structure

Increases in the environmental osmolarity are key determinants for the growth of microorganisms. To ensure a physiologically acceptable level of cellular hydration and turgor at high osmolarity, many bacteria accumulate compatible solutes. Osmotically controlled uptake systems allow the scavenging of these compounds from scarce environmental sources as effective osmoprotectants. A number of these systems belong to the BCCT family (betaine-choline-carnitine-transporter), sodium- or proton-coupled transporters (e.g. BetP and BetT respectively) that are ubiquitous in microorganisms. The BCCT family also contains CaiT, an L-carnitine/γ-butyrobetaine antiporter that is not involved in osmotic stress responses. The glycine betaine transporter BetP from Corynebacterium glutamicum is a representative for osmoregulated symporters of the BCCT family and functions both as an osmosensor and osmoregulator. The crystal structure of BetP in an occluded conformation in complex with its substrate glycine betaine and two crystal structures of CaiT in an inward-facing open conformation in complex with L-carnitine and γ-butyrobetaine were reported recently. These structures and the wealth of biochemical data on the activity control of BetP in response to osmotic stress enable a correlation between the sensing of osmotic stress by a transporter protein with the ensuing regulation of transport activity. Molecular determinants governing the high-affinity binding of the compatible solutes by BetP and CaiT, the coupling in symporters and antiporters, and the osmoregulatory properties are discussed in detail for BetP and various BCCT carriers.