Digital health technologies and machine learning augment patient reported outcomes to remotely characterise rheumatoid arthritis.

Digital measures of health status captured during daily life could greatly augment current in-clinic assessments for rheumatoid arthritis (RA), to enable better assessment of disease progression and impact. This work presents results from weaRAble-PRO, a 14-day observational study, which aimed to investigate how digital health technologies (DHT), such as smartphones and wearables, could augment patient reported outcomes (PRO) to determine RA status and severity in a study of 30 moderate-to-severe RA patients, compared to 30 matched healthy controls (HC). Sensor-based measures of health status, mobility, dexterity, fatigue, and other RA specific symptoms were extracted from daily iPhone guided tests (GT), as well as actigraphy and heart rate sensor data, which was passively recorded from patients' Apple smartwatch continuously over the study duration. We subsequently developed a machine learning (ML) framework to distinguish RA status and to estimate RA severity. It was found that daily wearable sensor-outcomes robustly distinguished RA from HC participants (F1, 0.807). Furthermore, by day 7 of the study (half-way), a sufficient volume of data had been collected to reliably capture the characteristics of RA participants. In addition, we observed that the detection of RA severity levels could be improved by augmenting standard patient reported outcomes with sensor-based features (F1, 0.833) in comparison to using PRO assessments alone (F1, 0.759), and that the combination of modalities could reliability measure continuous RA severity, as determined by the clinician-assessed RAPID-3 score at baseline (r2, 0.692; RMSE, 1.33). The ability to measure the impact of the disease during daily life-through objective and remote digital outcomes-paves the way forward to enable the development of more patient-centric and personalised measurements for use in RA clinical trials.

Cost-Effectiveness Modeling of Prostate-Specific Membrane Antigen Positron Emission Tomography with Piflufolastat F 18 for the Initial Diagnosis of Patients with Prostate Cancer in the United States.

BACKGROUND AND OBJECTIVES: Piflufolastat F 18 is a novel prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET) radiotracer that is superior to standard of care (SOC) imaging for the initial staging of prostate cancer and the detection of biochemical recurrence. As piflufolastat F 18 has been approved in the United States (US) for this indication, this modeling study assessed the cost effectiveness of piflufolastat F 18 versus fluciclovine F-18, gallium68-PSMA-11 (PSMA 11), and SOC imaging (a mix of bone scans, computed tomography, and magnetic resonance imaging) for the diagnosis and staging of prostate cancer from a US healthcare system perspective. PERSPECTIVE: A US third-party payer perspective was used, which for this population reflects a mix of commercial and Medicare, considering only direct healthcare costs. SETTING: This study utilized a tertiary healthcare setting. METHODS: A decision tree was used to map the diagnostic/treatment pathway, consisting of the proportion of patients with local, regional, distant, or no disease; prostate-specific antigen (PSA) ≤ 1.0 or > 1.0; and accuracy of imaging modalities. A Markov model predicted the long-term outcomes of disease progression according to treatment decisions. Inputs to the model were informed by data from the OSPREY and CONDOR clinical trials, public data, and the literature. Treatment mix included active surveillance, radiation therapy, prostatectomy, androgen deprivation therapy (ADT), and radiation therapy + ADT, informed by expert opinion. Outcomes included life-years (LY), quality-adjusted life-years (QALY), and the incremental cost-effectiveness ratio (ICER). All costs were reported in 2021 US dollars, using the US Bureau of Labor Statistics Consumer Price Index. A willingness-to-pay (WTP) threshold of $150,000 was considered cost effective, consistent with the upper range used as the standard for price benchmarks by the Institute for Clinical and Economic Review. The robustness of the base-case results was assessed in deterministic and probabilistic sensitivity analyses. RESULTS: Over a lifetime horizon, piflufolastat F 18 had the greatest effectiveness in terms of LYs (6.80) and QALYs (5.33); for the comparators, LYs ranged from 6.58 (SOC) to 6.76 (PSMA 11) and QALYs ranged from 5.12 (SOC) and 5.30 (PSMA 11). Piflufolastat F 18 was more cost effective compared with fluciclovine F 18, PSMA 11, and SOC, with ICERs of $21,122, $55,836, and $124,330 per QALY gained, respectively. Piflufolastat F 18 was associated with the greatest net monetary benefit ($627,918) compared with the other options at a WTP threshold of $150,000. The results of the deterministic and probabilistic sensitivity analyses supported the robustness of the base-case results. CONCLUSIONS: This study suggests that piflufolastat F 18 is a cost-effective diagnostic option for men with prostate cancer in the US, with higher associated LY, QALY, and greater net monetary benefit than fluciclovine F 18, PSMA 11, and SOC imaging.

Patient-centric assessment of rheumatoid arthritis using a smartwatch and bespoke mobile app in a clinical setting.

Rheumatoid arthritis (RA) is a fluctuating progressive disease requiring frequent symptom assessment for appropriate management. Continuous tracking using digital technologies may provide greater insights of a patient's experience. This prospective study assessed the feasibility, reliability, and clinical utility of using novel digital technologies to remotely monitor participants with RA. Participants with moderate to severe RA and non-RA controls were monitored continuously for 14 days using an iPhone with an integrated bespoke application and an Apple Watch. Participants completed patient-reported outcome measures and objective guided tests designed to assess disease-related impact on physical function. The study was completed by 28 participants with RA, 28 matched controls, and 2 unmatched controls. Completion rates for all assessments were > 97% and were reproducible over time. Several guided tests distinguished between RA and control cohorts (e.g., mean lie-to-stand time [seconds]: RA: 4.77, control: 3.25; P < 0.001). Participants with RA reporting greater stiffness, pain, and fatigue had worse guided test performances (e.g., wrist movement [P < 0.001] and sit-to-stand transition time [P = 0.009]) compared with those reporting lower stiffness, pain, and fatigue. This study demonstrates that digital technologies can be used in a well-controlled, remote clinical setting to assess the daily impact of RA.

Comparative Effectiveness of Pegcetacoplan Versus Ravulizumab and Eculizumab in Complement Inhibitor-Naïve Patients with Paroxysmal Nocturnal Hemoglobinuria: A Matching-Adjusted Indirect Comparison.

INTRODUCTION: In the absence of head-to-head trials, this study compared treatment outcomes with the C3 complement inhibitor pegcetacoplan versus the C5 complement inhibitor eculizumab or ravulizumab in complement inhibitor-naïve patients with paroxysmal nocturnal hemoglobinuria (PNH). METHODS: A matching-adjusted indirect comparison was conducted using individual patient data from the pegcetacoplan arm of the PRINCE trial (NCT04085601; n = 34) and aggregate data from the ravulizumab (n = 125) and eculizumab (n = 121) arms of the ALXN1210-PNH-301 trial (NCT03056040). Clinical and quality of life endpoints were evaluated after matching patients in the two trials on baseline characteristics. The weighted Wald test with 95% confidence interval was used to compare categorical and continuous variables (i.e., weighted chi-squared and z tests, respectively). Bias factor analysis was performed to quantify the extent of residual bias from unmeasured confounders. RESULTS: After weighting, treatment with pegcetacoplan was associated with statistically significant improvements in most clinical endpoints compared with ravulizumab or eculizumab treatment. These included: greater absolute and percent reductions in lactate dehydrogenase (LDH) level and increase in hemoglobin level from baseline; shorter time to first occurrence of LDH normalization; larger proportions of patients achieving hemoglobin stabilization and avoiding transfusion, with fewer packed red blood cell units transfused; and a smaller proportion of patients experiencing breakthrough hemolysis (all p < 0.05). Patients receiving pegcetacoplan also had a greater increase in general health status score from baseline compared with those receiving C5 complement inhibitors. CONCLUSION: Pegcetacoplan provides clinical benefits as first-line treatment for complement inhibitor-naïve patients with PNH. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT04085601.

Treatment patterns and overall survival of patients with double-class and triple-class refractory multiple myeloma: a US electronic health record database study.

Patients with relapsed/refractory multiple myeloma (RRMM) resistant to multiple drug classes remain a high unmet need population. This longitudinal retrospective cohort study assessed real-world treatment patterns and outcomes in adults with RRMM. Patients who had three or more prior lines of therapy including a proteasome inhibitor (PI) and an immunomodulatory agent (double-exposed) were further categorized as refractory to a PI and an immunomodulatory agent (double-class refractory, n = 381) or additionally to an anti-CD38 monoclonal antibody (triple-class refractory, n = 173). Treatment options are limited for patients with double-class or triple-class refractory disease. Retreatment is a part of standard of care. Bortezomib and lenalidomide had the highest retreatment rates among double-class and triple-class refractory patients. Survival outcomes remain poor among RRMM patients with median overall survival (OS) of 22.3 and 11.6 months for double-class refractory and triple-class refractory patients, respectively. This study highlights the need for novel efficacious therapies in this heavily pretreated RRMM population.

Identifying a Heart Rate Recovery Criterion After a 6-Minute Walk Test in COPD.

BACKGROUND: Slow heart rate recovery (HRR) after exercise is associated with autonomic dysfunction and increased mortality. What HRR criterion at 1-minute after a 6-minute walk test (6MWT) best defines pulmonary impairment?. STUDY DESIGN AND METHODS: A total of 5008 phase 2 COPDGene (NCT00608764) participants with smoking history were included. A total of 2127 had COPD and, of these, 385 were followed-up 5-years later. Lung surgery, transplant, bronchiectasis, atrial fibrillation, heart failure and pacemakers were exclusionary. HR was measured from pulse oximetry at end-walk and after 1-min seated recovery. A receiver operator characteristic (ROC) identified optimal HRR cut-off. Generalized linear regression determined HRR association with spirometry, chest CT, symptoms and exacerbations. RESULTS: HRR after 6MWT (bt/min) was categorized in quintiles: ≤5 (23.0% of participants), 6-10 (20.7%), 11-15 (18.9%), 16-22 (18.5%) and ≥23 (18.9%). Compared to HRR≤5, HRR≥11 was associated with (p<0.001): lower pre-walk HR and 1-min post HR; greater end-walk HR; greater 6MWD; greater FEV1%pred; lower airway wall area and wall thickness. HRR was positively associated with FEV1%pred and negatively associated with airway wall thickness. An optimal HRR ≤10 bt/min yielded an area under the ROC curve of 0.62 (95% CI 0.58-0.66) for identifying FEV1<30%pred. HRR≥11 bt/min was the lowest HRR associated with consistently less impairment in 6MWT, spirometry and CT variables. In COPD, HRR≤10 bt/min was associated with (p<0.001): ≥2 exacerbations in the previous year (OR=1.76[1.33-2.34]); CAT≥10 (OR=1.42[1.18-1.71]); mMRC≥2 (OR=1.42[1.19-1.69]); GOLD 4 (OR=1.98[1.44-2.73]) and GOLD D (OR=1.51[1.18-1.95]). HRR≤10 bt/min was predicted COPD exacerbations at 5-year follow-up (RR=1.83[1.07-3.12], P=0.027). CONCLUSION: HRR≤10 bt/min after 6MWT in COPD is associated with more severe expiratory flow limitation, airway wall thickening, worse dyspnoea and quality of life, and future exacerbations, suggesting that an abnormal HRR≤10 bt/min after a 6MWT may be used in a comprehensive assessment in COPD for risk of severity, symptoms and future exacerbations.

Comparative effectiveness of pegcetacoplan versus ravulizumab in patients with paroxysmal nocturnal hemoglobinuria previously treated with eculizumab: a matching-adjusted indirect comparison.

OBJECTIVE: In the absence of a head-to-head study, we assessed the comparative effectiveness of pegcetacoplan, a targeted C3 complement inhibitor, vs. ravulizumab, a C5 complement inhibitor, among patients with paroxysmal nocturnal hemoglobinuria (PNH) previously treated with eculizumab using matching-adjusted indirect comparison methodology. METHODS: Individual patient data from the PEGASUS study (NCT03500549) comparing pegcetacoplan and eculizumab enabled adjustment for baseline differences compared with published results from the ALXN1210-PNH-302 study (NCT03056040), comparing ravulizumab and eculizumab. Adjusted differences and 95% confidence intervals (CIs) were computed via weighted Wald tests for comparisons of pegcetacoplan vs. ravulizumab, anchored to the common comparator eculizumab. RESULTS: Sixty-eight patients from PEGASUS (36 pegcetacoplan; 32 eculizumab) and 195 from ALXN1210-PNH-302 (97 ravulizumab; 98 eculizumab) were included. Compared with ravulizumab, treatment with pegcetacoplan was associated with more transfusion avoidance (adjusted difference [95% CI] = +71.4% [53.5%, 89.3%]), hemoglobin level stabilization (+75.5% [56.4%, 94.6%]), lactate dehydrogenase (LDH) level normalization (+64.0% [41.8%, 86.1%]), and fewer blood transfusions (-5.7 units [-7.2, -4.2]). Additionally, patients who received pegcetacoplan experienced clinically meaningful improvements in fatigue (+8.2 points [3.8, 12.6]), global health status (+9.6 points [0.1, 19.0]), physical functioning (+11.5 points [3.6, 19.5]), and fatigue symptoms (-13.3 points [-23.7, -3.0]), compared with ravulizumab. Mean change from baseline in LDH level was not significantly different for pegcetacoplan vs. ravulizumab. CONCLUSIONS: Results suggest that among patients previously treated with eculizumab, clinical, hematological, and quality of life endpoints were better for patients who received the C3 complement inhibitor pegcetacoplan vs. patients who received ravulizumab, a C5 complement inhibitor.

Comparing perceptions of professionalism by pharmacy students, faculty, and staff during didactic education.

INTRODUCTION: The objectives were to describe pharmacy students' perceptions of professionalism and to compare students and faculty/staff perceptions of professionalism during the didactic years at Touro University California College of Pharmacy in California (TUC COP). METHODS: A two-part online survey was administered to the TUC COP faculty/staff and first-year (P1) and second-professional year (P2) students in May 2016. The first part of the survey collected demographic information, assessment of faculty/staff and students' overall opinions on behavior and conduct displayed by P1 and P2 students, students' responses about the average of missed lectures per month, and the average number of days of late arrival to lecture per week. The second part assessed professionalism perceptions responses to 20 scenarios using a 4-point Likert rating. RESULTS: The study included 37 (88.4%) faculty/staff and 181 (96.4%) P1 and P2 students, for a 98% response rate. Of the faculty/staff, 59.5% perceived the students' overall behaviors and conduct as acceptable whereas 35.3% of students perceived the overall behavior of P1 and P2 students as acceptable, with the majority of students self-reporting missing on average fewer than five lectures per month (65.2%) and arriving late to lecture fewer than one day each week (71.8%). There were statistically significant differences between faculty/staff and students' responses in 9 of the 20 scenarios. CONCLUSIONS: Differences in responses between faculty/staff and students regarding what is considered professional suggest that there is a gap in professionalism perceptions that should be addressed during didactic years.

Predictors of chemoradiotherapy versus single modality therapy and overall survival among patients with unresectable, stage III non-small cell lung cancer.

INTRODUCTION: Concurrent chemoradiotherapy (cCRT) was the standard of care for patients with unresectable stage III non-small cell lung cancer (NSCLC) prior to the PACIFIC trial, however, patients also received single modality therapy. This study identified predictors of therapy and differences in overall survival (OS). METHODS: This retrospective study included stage III NSCLC patients aged ≥65 years, with ≥1 claim for systemic therapy (ST) or radiotherapy (RT) within 90 days of diagnosis, identified in SEER-Medicare data (2009-2014). Patients who had overlapping claims for chemotherapy and RT ≤90 days from start of therapy were classified as having received cCRT. Patients who received sequential CRT or surgical resection of tumor were excluded. Predictors of cCRT were analyzed using logistic regression. OS was compared between therapies using adjusted Cox proportional hazards models. RESULTS: Of 3,799 patients identified, 21.7% received ST; 26.3% received RT; and 52.0% received cCRT. cCRT patients tended to be younger (p <0.001), White (p = 0.002), and have a good predicted performance status (p<0.001). Patients who saw all three specialist types (medical oncologist, radiation oncologist, and surgeon) had increased odds of receiving cCRT (p<0.001). ST and RT patients had higher mortality risk versus cCRT patients (hazard ratio [95% CI]: ST: 1.38 [1.26-1.51]; RT: 1.75 [1.61, 1.91]); p<0.001). CONCLUSIONS: Several factors contributed to treatment selection, including patient age and health status, and whether the patient received multidisciplinary care. Given the survival benefit of receiving cCRT over single-modality therapy, physicians should discuss treatment within a multidisciplinary team, and be encouraged to pursue cCRT for patients with unresectable stage III NSCLC.

A Data-Driven Approach to Predicting Septic Shock in the Intensive Care Unit.

Early diagnosis of sepsis and septic shock has been unambiguously linked to lower mortality and better patient outcomes. Despite this, there is a strong unmet need for a reliable clinical tool that can be used for large-scale automated screening to identify high-risk patients. We addressed the following questions: Can a novel algorithm to identify patients at high risk of septic shock 24 hours before diagnosis be discovered using available clinical data? What are performance characteristics of this predictive algorithm? Can current metrics for evaluation of sepsis be improved using novel algorithm? Publicly available data from the intensive care unit setting was used to build septic shock and control patient cohorts. Using Bayesian networks, causal relationships between diagnosis groups, procedure groups, laboratory results, and demographic data were inferred. Predictive model for septic shock 24 hours prior to digital diagnosis was built based on inferred causal networks. Sepsis risk scores were augmented by de novo inferred model and performance was evaluated. A novel predictive model to identify high-risk patients 24 hours ahead of time, with area under curve of 0.81, negative predictive value of 0.87, and a positive predictive value as high as 0.65 was built. The specificity of quick sequential organ failure assessment, systemic inflammatory response syndrome, and modified early warning score was improved when augmented with the novel model, whereas no improvements were made to the sequential organ failure assessment score. We used a data-driven, expert knowledge agnostic method to build a screening algorithm for early detection of septic shock. The model demonstrates strong performance in the data set used and provides a basis for expanding this work toward building an algorithm that is used to screen patients based on electronic medical record data in real time.

Cardiac arrhythmia detection outcomes among patients monitored with the Zio patch system: a systematic literature review.

Objective: Cardiac arrhythmias can be serious and life threatening, and can impose a significant burden on healthcare systems. Recent technological advances in ambulatory electrocardiogram recorders have led to the development of unobtrusive wearable biosensors which allow physicians to study patients' continuous cardiac rhythm data collected over multiple weeks. The objective of this systematic literature review was to summarize evidence on the clinical effectiveness of the Zio 1 patch, a long-term, continuous, uninterrupted cardiac monitoring system. Methods: Findings from searches of MEDLINE, Embase and the Cochrane Central Register of Controlled Trials, as well as grey literature, were screened by two reviewers to identify studies reporting cardiac arrhythmia detection outcomes among patients monitored with Zio for an intended duration ≥7 days. Results: Twenty-three publications (22 unique studies) were identified. The unweighted mean wear time was 10.4 days (median ranging from 5 to 14 days). The rate of arrhythmia detection increased with monitoring durations >48 h and continued to increase beyond 7 days of monitoring. Across the 22 studies, unweighted mean detection rates for atrial fibrillation (AF; n = 15), supraventricular tachycardia or supraventricular ectopy (n = 15), and ventricular tachycardia (n = 15) were 12.2%, 45.5% and 17.3%, respectively. Unweighted mean detection rates for chronic/sustained AF (n = 5) and paroxysmal AF (n = 5) were 5.6% and 23.3%, respectively. Conclusion: Findings from the review suggest that long-term, continuous, uninterrupted monitoring with Zio results in longer patient wear times and higher cardiac arrhythmia detection rates compared with outcomes reported in previous reviews of short-duration (24-48 h) cardiac rhythm recording studies.

Maintenance of the bladder cancer precursor urothelial hyperplasia requires FOXA1 and persistent expression of oncogenic HRAS.

Tumorigenesis requires accumulation of genetic and epigenetic alterations, some of which drive tumor initiation. "Oncogene addiction" describes the phenomenon that (1) well-established cancers are dependent on one mutated oncogene or pathway for the maintenance of a malignant phenotype and that (2) withdrawal of the single oncogenic event leads to growth arrest and/or cancer regression. While oncogene addiction has been experimentally validated in advanced tumor models, its role in tumor precursors has not been investigated. We utilized the requirement of Forkhead box A1 (Foxa1) for transcriptional activation of the Upk2-promoter to temporally control the expression of Upk2-HRAS* oncogene, an inducer of urothelial hyperplasia in transgenic mice. Inducible homozygous knockout of Foxa1 in Upk2-HRAS*/UBC-CreERT2/Foxa1loxp/loxp mice results in reduced HRAS* levels. This led to a marked reduction of urothelial proliferation as evidenced by urothelial thinning, degenerative changes such as intracellular vacuole formation, and reduced Ki67 expression. Reduced proliferation did not affect basal, Krt14-positive cells, supporting the fact that Foxa1-regulated Upk2-HRAS* expression occurs primarily in supra-basal cells. Our results indicate that maintenance of urothelial hyperplasia in Upk2-HRAS* mice depends on continuous expression of Foxa1 and activated HRAS, and that mutated receptor tyrosine kinases, FOXA1 and/or other downstream effectors may mediate oncogene addiction in urothelial hyperplasia.

Atypical Expression and Activation of GluN2A- and GluN2B-Containing NMDA Receptors at Ganglion Cells during Retinal Degeneration.

Cellular communication through chemical synapses is determined by the nature of the neurotransmitter and the composition of postsynaptic receptors. In the excitatory synapse between bipolar and ganglion cells of the retina, postsynaptic AMPA receptors mediate resting activity. During evoked response, however, more abundant and sustained levels of glutamate also activate GluN2B-containing NMDA receptors (NMDARs). This phasic recruitment of distinct glutamate receptors is essential for visual discrimination; however, the fidelity of this basic mechanism under elevated glutamate levels due to aberrant activity, a common pathophysiology, is not known. Here, in both male and female mice with retinal degeneration (rd10), a condition associated with elevated synaptic activity, we reveal that changes in synaptic input to ganglion cells altered both composition and activation of NMDARs. We found that, in contrast to wild type, the spontaneous activity of rd10 cells was largely NMDAR-dependent. Surprisingly, this activity was driven primarily by atypical activation of GluN2A -containing NMDARs, not GluN2B-NMDARs. Indeed, immunohistochemical analyses and Western blot showed greater levels of the GluN2A-NMDAR subunit expression in rd10 retina compared to wild type. Overall, these results demonstrate how aberrant signaling leads to pathway-specific alterations in NMDAR expression and function.

Pannexin 1 sustains the electrophysiological responsiveness of retinal ganglion cells.

Pannexin 1 (Panx1) forms ATP-permeable membrane channels that play a key role in purinergic signaling in the nervous system in both normal and pathological conditions. In the retina, particularly high levels of Panx1 are found in retinal ganglion cells (RGCs), but the normal physiological function in these cells remains unclear. In this study, we used patch clamp recordings in the intact inner retina to show that evoked currents characteristic of Panx1 channel activity were detected only in RGCs, particularly in the OFF-type cells. The analysis of pattern electroretinogram (PERG) recordings indicated that Panx1 contributes to the electrical output of the retina. Consistently, PERG amplitudes were significantly impaired in the eyes with targeted ablation of the Panx1 gene in RGCs. Under ocular hypertension and ischemic conditions, however, high Panx1 activity permeated cell membranes and facilitated the selective loss of RGCs or stably transfected Neuro2A cells. Our results show that high expression of the Panx1 channel in RGCs is essential for visual function in the inner retina but makes these cells highly sensitive to mechanical and ischemic stresses. These findings are relevant to the pathophysiology of retinal disorders induced by increased intraocular pressure, such as glaucoma.

Leveraging Optogenetic-Based Neurovascular Circuit Characterization for Repair.

Optogenetic techniques are a powerful tool for determining the role of individual functional components within complex neural circuits. By genetically targeting specific cell types, neural mechanisms can be actively manipulated to gain a better understanding of their origin and function, both in health and disease. The potential of optogenetics is not limited to answering biological questions, as it is also a promising therapeutic approach for neurological diseases. An important prerequisite for this approach is to have an identified target with a uniquely defined role within a given neural circuit. Here, we examine the retinal neurovascular unit, a circuit that incorporates neurons and vascular cells to control blood flow in the retina. We highlight the role of a specific cell type, the cholinergic amacrine cell, in modulating vascular cells, and demonstrate how this can be targeted and controlled with optogenetics. A better understanding of these mechanisms will not only extend our understanding of neurovascular interactions in the brain, but ultimately may also provide new targets to treat vision loss in a variety of retinal diseases.

Disruption in dopaminergic innervation during photoreceptor degeneration.

Dopaminergic amacrine cells (DACs) release dopamine in response to light-driven synaptic inputs, and are critical to retinal light adaptation. Retinal degeneration (RD) compromises the light responsiveness of the retina and, subsequently, dopamine metabolism is impaired. As RD progresses, retinal neurons exhibit aberrant activity, driven by AII amacrine cells, a primary target of the retinal dopaminergic network. Surprisingly, DACs are an exception to this physiological change; DACs exhibit rhythmic activity in healthy retina, but do not burst in RD. The underlying mechanism of this divergent behavior is not known. It is also unclear whether RD leads to structural changes in DACs, impairing functional regulation of AII amacrine cells. Here we examine the anatomical details of DACs in three mouse models of human RD to determine how changes to the dopaminergic network may underlie physiological changes in RD. By using rd10, rd1, and rd1/C57 mice we were able to dissect the impacts of genetic background and the degenerative process on DAC structure in RD retina. We found that DACs density, soma size, and primary dendrite length are all significantly reduced. Using a novel adeno-associated virus-mediated technique to label AII amacrine cells in mouse retina, we observed diminished dopaminergic contacts to AII amacrine cells in RD mice. This was accompanied by changes to the components responsible for dopamine synthesis and release. Together, these data suggest that structural alterations of the retinal dopaminergic network underlie physiological changes during RD.

Aberrant activity in retinal degeneration impairs central visual processing and relies on Cx36-containing gap junctions.

In retinal degenerative disease (RD), the diminished light signal from dying photoreceptors has been considered the sole cause of visual impairment. Recent studies show a 10-fold increase in spontaneous activity in the RD network, challenging this paradigm. This aberrant activity forms a new barrier for the light signal, and not only exacerbates the loss of vision, but also may stand in the way of visual restoration. This activity originates in AII amacrine cells and relies on excessive activation of gap junctions. However, it remains unclear whether aberrant activity affects central visual processing and what mechanisms lead to this excessive activation of gap junctions. By combining genetic manipulation with electrophysiological recordings of light-induced activity in both living mice and isolated wholemount retina, we demonstrate that aberrant activity extends along retinotectal projections to alter activity in higher brain centers. Next, to selectively eliminate Cx36-containing gap junctions, which are the primary type expressed by AII amacrine cells, we crossed rd10 mice, a slow-degenerating model of RD, with Cx36 knockout mice. We found that retinal aberrant activity was reduced in the rd10/Cx36KO mice compared to rd10 controls, a direct evidence for involvement of Cx36-containing gap junctions in generating aberrant activity in RD. These data provide an essential support for future experiments to determine if selectively targeting these gap junctions could be a valid strategy for reducing aberrant activity and restoring light responses in RD.

Increased phosphorylation of Cx36 gap junctions in the AII amacrine cells of RD retina.

Retinal degeneration (RD) encompasses a family of diseases that lead to photoreceptor death and visual impairment. Visual decline due to photoreceptor cell loss is further compromised by emerging spontaneous hyperactivity in inner retinal cells. This aberrant activity acts as a barrier to signals from the remaining photoreceptors, hindering therapeutic strategies to restore light sensitivity in RD. Gap junctions, particularly those expressed in AII amacrine cells, have been shown to be integral to the generation of aberrant activity. It is unclear whether gap junction expression and coupling are altered in RD. To test this, we evaluated the expression and phosphorylation state of connexin36 (Cx36), the gap junction subunit predominantly expressed in AII amacrine cells, in two mouse models of RD, rd10 (slow degeneration) and rd1 (fast degeneration). Using Ser293-P antibody, which recognizes a phosphorylated form of connexin36, we found that phosphorylation of connexin36 in both slow and fast RD models was significantly greater than in wildtype controls. This elevated phosphorylation may underlie the increased gap junction coupling of AII amacrine cells exhibited by RD retina.

Aberrant synaptic input to retinal ganglion cells varies with morphology in a mouse model of retinal degeneration.

Retinal degeneration describes a group of disorders which lead to progressive photoreceptor cell death, resulting in blindness. As this occurs, retinal ganglion cells (RGCs) begin to develop oscillatory physiological activity. Here we studied the morphological and physiological properties of RGCs in rd1 mice, aged 30-60 days, to determine how this aberrant activity correlates with morphology. Patch-clamp recordings of excitatory and inhibitory currents were performed, then dendritic structures were visualized by infusion of fluorescent dye. Only RGCs with oscillatory activity were selected for further analysis. Oscillatory frequency and power were calculated using power spectral density analysis of recorded currents. Dendritic arbor stratification, total length, and area were measured from confocal microscope image stacks. These measurements were used to sort RGCs by cluster analysis using Ward's Method. This resulted in a total of 10 clusters, with monostratified and bistratified cells having five clusters each. Both populations exhibited correlations between arbor stratification and aberrant inhibitory input, while excitatory input did not vary with arbor distribution. These findings illustrate the relationship between aberrant activity and RGC morphology at early stages of retinal degeneration.