Self-assessment of cochlear health by cochlear implant recipients.

Recent technological advances in cochlear implant (CI) telemetry have enabled, for the first time, CI users to perform cochlear health (CH) measurements through self-assessment for prolonged periods of time. This is important to better understand the influence of CH on CI outcomes, and to assess the safety and efficacy of future novel treatments for deafness that will be administered as adjunctive therapies to cochlear implantation. We evaluated the feasibility of using a CI to assess CH and examined patterns of electrode impedances, electrically-evoked compound action potentials (eCAPs) and electrocochleography (ECochGs), over time, in a group of adult CI recipients. Fifteen subjects were trained to use the Active Insertion Monitoring tablet by Advanced Bionics, at home for 12 weeks to independently record impedances twice daily, eCAPs once weekly and ECochGs daily in the first week, and weekly thereafter. Participants also completed behavioral hearing and speech assessments. Group level measurement compliance was 98.9% for impedances, 100% for eCAPs and 99.6% for ECochGs. Electrode impedances remained stable over time, with only minimal variation observed. Morning impedances were significantly higher than evening measurements, and impedances increased toward the base of the cochlea. eCAP thresholds were also highly repeatable, with all subjects showing 100% measurement consistency at, at least one electrode. Just over half of all subjects showed consistently absent thresholds at one or more electrodes, potentially suggesting the existence of cochlear dead regions. All subjects met UK NICE guidelines for cochlear implantation, so were expected to have little residual hearing. ECochG thresholds were, unsurprisingly, highly erratic and did not correlate with audiometric thresholds, though lower ECochG thresholds showed more repeatability over time than higher thresholds. We conclude that it is feasible for CI users to independently record CH measurements using their CI, and electrode impedances and eCAPs are promising measurements for objectively assessing CH.

Assessment of arrhythmia mechanism and burden of the infarcted ventricles following remuscularization with pluripotent stem cell-derived cardiomyocyte patches using patient-derived models.

AIMS: Direct remuscularization with pluripotent stem cell-derived cardiomyocytes (PSC-CMs) seeks to address the onset of heart failure post-myocardial infarction (MI) by treating the persistent muscle deficiency that underlies it. However, direct remuscularization with PSC-CMs could potentially be arrhythmogenic. We investigated two possible mechanisms of arrhythmogenesis-focal vs. re-entrant-arising from direct remuscularization with PSC-CM patches in two personalized, human ventricular computer models of post-MI. Moreover, we developed a principled approach for evaluating arrhythmogenicity of direct remuscularization that factors in the VT propensity of the patient-specific post-MI fibrotic substrate and use it to investigate different conditions of patch remuscularization. METHODS AND RESULTS: Two personalized, human ventricular models of post-MI (P1 and P2) were constructed from late gadolinium enhanced (LGE)-magnetic resonance images (MRIs). In each model, remuscularization with PSC-CM patches was simulated under different treatment conditions that included patch engraftment, patch myofibril orientation, remuscularization site, patch size (thickness and diameter), and patch maturation. To determine arrhythmogenicity of treatment conditions, VT burden of heart models was quantified prior to and after simulated remuscularization and compared. VT burden was quantified based on inducibility (i.e. weighted sum of pacing sites that induced) and severity (i.e. the number of distinct VT morphologies induced). Prior to remuscularization, VT burden was significant in P1 (0.275) and not in P2 (0.0, not VT inducible). We highlight that re-entrant VT mechanisms would dominate over focal mechanisms; spontaneous beats emerging from PSC-CM grafts were always a fraction of resting sinus rate. Moreover, incomplete patch engraftment can be particularly arrhythmogenic, giving rise to particularly aberrant electrical activation and conduction slowing across the PSC-CM patches along with elevated VT burden when compared with complete engraftment. Under conditions of complete patch engraftment, remuscularization was almost always arrhythmogenic in P2 but certain treatment conditions could be anti-arrhythmogenic in P1. Moreover, the remuscularization site was the most important factor affecting VT burden in both P1 and P2. Complete maturation of PSC-CM patches, both ionically and electrotonically, at the appropriate site could completely alleviate VT burden. CONCLUSION: We identified that re-entrant VT would be the primary VT mechanism in patch remuscularization. To evaluate the arrhythmogenicity of remuscularization, we developed a principled approach that factors in the propensity of the patient-specific fibrotic substrate for VT. We showed that arrhythmogenicity is sensitive to the patient-specific fibrotic substrate and remuscularization site. We demonstrate that targeted remuscularization can be safe in the appropriate individual and holds the potential to non-destructively eliminate VT post-MI in addition to addressing muscle deficiency underlying heart failure progression.

Objective assessment of electrode discrimination with the auditory change complex in adult cochlear implant users.

The spatial auditory change complex (ACC) is a cortical response elicited by a change in place of stimulation. There is growing evidence that it provides a useful objective measure of electrode discrimination in cochlear implant (CI) users. To date, the spatial ACC has only been measured in relatively experienced CI users with one type of device. Early assessment of electrode discrimination could allow auditory stimulation to be optimized during a potentially sensitive period of auditory rehabilitation. In this study we used a direct stimulation paradigm to measure the spatial ACC in both pre- and post-lingually deafened adults. We show that it is feasible to measure the spatial ACC in different CI devices and as early as 1 week after CI switch-on. The spatial ACC has a strong relationship with performance on a behavioural discrimination task and in some cases provides information over and above behavioural testing. We suggest that it may be useful to measure the spatial ACC to guide auditory rehabilitation and improve hearing performance in CI users.

Optogenetics-enabled assessment of viral gene and cell therapy for restoration of cardiac excitability.

Multiple cardiac pathologies are accompanied by loss of tissue excitability, which leads to a range of heart rhythm disorders (arrhythmias). In addition to electronic device therapy (i.e. implantable pacemakers and cardioverter/defibrillators), biological approaches have recently been explored to restore pacemaking ability and to correct conduction slowing in the heart by delivering excitatory ion channels or ion channel agonists. Using optogenetics as a tool to selectively interrogate only cells transduced to produce an exogenous excitatory ion current, we experimentally and computationally quantify the efficiency of such biological approaches in rescuing cardiac excitability as a function of the mode of application (viral gene delivery or cell delivery) and the geometry of the transduced region (focal or spatially-distributed). We demonstrate that for each configuration (delivery mode and spatial pattern), the optical energy needed to excite can be used to predict therapeutic efficiency of excitability restoration. Taken directly, these results can help guide optogenetic interventions for light-based control of cardiac excitation. More generally, our findings can help optimize gene therapy for restoration of cardiac excitability.

Gel-free multiplexed reduced representation bisulfite sequencing for large-scale DNA methylation profiling.

Sequencing-based approaches have led to new insights about DNA methylation. While many different techniques for genome-scale mapping of DNA methylation have been employed, throughput has been a key limitation for most. To further facilitate the mapping of DNA methylation, we describe a protocol for gel-free multiplexed reduced representation bisulfite sequencing (mRRBS) that reduces the workload dramatically and enables processing of 96 or more samples per week. mRRBS achieves similar CpG coverage to the original RRBS protocol, while the higher throughput and lower cost make it better suited for large-scale DNA methylation mapping studies, including cohorts of cancer samples.

Managing type 2 diabetes: going beyond glycemic control.

BACKGROUND: Aggressive management of type 2 diabetes is necessary to achieve glycemic and nonglycemic treatment goals. Attainment of treatment goals is associated with a decreased risk of diabetes-related complications, costs, and health care utilization. OBJECTIVE: To review the advantages and disadvantages of different glucose-lowering agents, with an emphasis on the role of thiazolidinediones (TZDs). SUMMARY: Diabetes has become increasingly prevalent, particularly among younger age groups in the United States, accounting for approximately 15% of health care expenditures by managed care organizations. Reducing a patient's glycated hemoglobin (A1C) has been shown to decrease the risk of diabetes-related complications, as well as reduce medical costs and health care utilization. Despite this knowledge, achievement of the American Diabetes Association (ADA) goal A1C of < 7% is suboptimal, and < 1 in 10 patients also reach the ADA targets for cholesterol (low-density lipoprotein < 100 mg per dL) and blood pressure (< 130/80 mm Hg). To ensure that all ADA treatment goals are met, clinicians need to closely monitor patients and adjust therapy as needed, taking into consideration both a drug's glycemic and nonglycemic effects when selecting medication therapy. Four basic defects contribute to type 2 diabetes: insulin resistance, decreased insulin secretion, increased hepatic glucose production, and reduced glucagon-like peptide-1 levels. Unlike metformin, sulfonylureas, and insulin that address only 1 or 2 physiologic defects, TZDs uniquely address 3 of these defects at the adipocyte. Metformin is recommended for initial drug therapy; TZDs, sulfonylureas, and insulin are useful options as add-on therapy for patients whose A1C levels remain >or= 7% despite treatment with metformin and lifestyle interventions. It has been suggested that TZDs, when used either as add-on therapy or when appropriate as monotherapy, may conserve pancreatic beta-cell function over an observed 3- to 5-year period of time and sustain a decrease in A1C ranging from 0.5%-1.5%. Although rarely associated with hypoglycemia, TZDs may cause total body weight gain that is most commonly caused by volume expansion, which may manifest as new or worsened heart failure in susceptible individuals. Pioglitazone and rosiglitazone, the 2 TZDs available in the United States, contain black box label warnings about their potential to cause or exacerbate congestive heart failure; additional data have suggested a link to ischemic cardiac events. Recent data also suggest that TZDs may reduce bone density. Conversely, pioglitazone may have some vasculoprotective effect related to elevation of high-density lipoprotein and lessened progression of carotid intima-media thickness; however, any effect on macrovascular clinical outcomes is unknown. Other drug options are available for the treatment of type 2 diabetes, such as incretin-based therapies. Yet despite their favorable effects on glycemia, they have not been included to date in the ADA treatment algorithm. CONCLUSIONS: Proper glycemic control and attainment of other nonglycemic management targets (e.g., blood pressure, lipids, body weight) are essential to the prevention of long-term complications of diabetes and to reduction of overall disease management costs. Therefore, patients with diabetes should be followed closely to ensure that they achieve and maintain both glycemic and nonglycemic treatment goals. Most patients will not sustain an adequate level of control using nondrug or single-drug therapeutic approaches. When choosing among treatment options, consideration should be given to the nonglycemic as well as glycemic effects of various glucose-lowering agents.