Anders Tolstrup Christiansen

Subretinal Implantation of Electrospun, Short Nanowire, and Smooth Poly(ε-caprolactone) Scaffolds to the Subretinal Space of Porcine Eyes

Biodegradable scaffolds play an important adjunct role in transplantation of retinal progenitor cells (RPCs) to the subretinal space. Poly(ε-Caprolactone) (PCL) scaffolds with different modifications were subretinally implanted in 28 porcine eyes and evaluated by multifocal electroretinography (mfERG) and histology after 6 weeks of observation. PCL Short Nanowire, PCL Electrospun, and PCL Smooth scaffolds were well tolerated in the subretinal space in pigs and caused no inflammation and limited tissue disruption. PCL Short Nanowire had an average rate of preserved overlying outer retina 17% higher than PCL Electrospun and 25% higher than PCL Smooth. Furthermore, PCL Short Nanowire was found to have the most suitable degree of stiffness for surgical delivery to the subretinal space. The membrane-induced photoreceptor damage could be shown on mfERG, but the reductions in P1 amplitude were only significant for the PCL Smooth. We conclude that of the tested scaffolds, PCL Short Nanowire is the best candidate for subretinal implantation.

Melanopsin expressing human retinal ganglion cells: Subtypes, distribution and intraretinal connectivity

Intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin belong to a heterogenic population of RGCs which regulate the circadian clock, masking behavior, melatonin suppression, the pupillary light reflex, and sleep/wake cycles. The different functions seem to be associated to different subtypes of melanopsin cells. In rodents, subtype classification has associated subtypes to function. In primate and human retina such classification has so far, not been applied. In the present study using antibodies against N‐ and C‐terminal parts of human melanopsin, confocal microscopy and 3D reconstruction of melanopsin immunoreactive (‐ir) RGCs, we applied the criteria used in mouse on human melanopsin‐ir RGCs. We identified M1, displaced M1, M2, and M4 cells. We found two other subtypes of melanopsin‐ir RGCs, which were named “gigantic M1 (GM1)” and “gigantic displaced M1 (GDM1).” Few M3 cells and no M5 subtypes were labeled. Total cell counts from one male and one female retina revealed that the human retina contains 7283 ± 237 melanopsin‐ir (0.63–0.75% of the total number of RGCs). The melanopsin subtypes were unevenly distributed. Most significant was the highest density of M4 cells in the nasal retina. We identified input to the melanopsin‐ir RGCs from AII amacrine cells and directly from rod bipolar cells via ribbon synapses in the innermost ON layer of the inner plexiform layer (IPL) and from dopaminergic amacrine cells and GABAergic processes in the outermost OFF layer of the IPL. The study characterizes a heterogenic population of human melanopsin‐ir RGCs, which most likely are involved in different functions.

A systematic review of breath analysis and detection of volatile organic compounds in COPD

Chronic obstructive pulmonary disease (COPD) is, according to the WHO, the fifth leading cause of death worldwide, and is expected to increase to rank third in 2030. Few robust biomarkers for COPD exist, and several attempts have been made to find suitable molecular marker candidates. One rising research area is breath analysis, with several published attempts to find exhaled compounds as diagnostic markers. The field is broad and no review of published COPD breath analysis studies exists yet. We have conducted a systematic review examining the state of art and identified 12 suitable papers, which we investigated in detail to extract a list of potential COPD breath marker molecules. First, we observed that no candidate markers were detected in all 12 studies. Only three were reported in more than one paper, thus reliable exhaled markers are still missing. A major challenge is the heterogeneity in breath sampling technologies, the selection of appropriate control groups, and a lack of sophisticated (and standardized) statistical data analysis methods. No cross-hospital/study comparisons have been published yet. We conclude that future efforts should (also) concentrate on making breath data analysis more comparable through standardization of sampling, data processing, and reporting.

The Influence of Brightness on Functional Assessment by mfERG: A Study on Scaffolds Used in Retinal Cell Transplantation in Pigs

To determine the effect of membrane brightness on multifocal electroretinograms (mfERGs), we implanted poly lactic-co-glycolic acid (PLGA) membranes in the subretinal space of 11 porcine eyes. We compared membranes with their native shiny white color with membranes that were stained with a blue dye (Brilliant Blue). Histological and electrophysiological evaluation of the overlying retina was carried out 6 weeks after implantation. Histologically, both white and blue membranes degraded in a spongiform manner leaving a disrupted outer retina with no preserved photoreceptor segments. Multifocal ERG revealed the white membranes to have a significantly higher P1-amplitude ratio than the blue (P = 0.027), and a correlation between brightness ratio and P1-amplitude ratio was found (r = 0.762). Based on our findings, we conclude that bright subretinal objects can produce normal mfERG amplitude ratios even when the adjacent photoreceptors are missing. Functional assessment with mfERG in scaffold implant studies should therefore be evaluated with care.

Retrospective analysis of radial EBUS outcome for the diagnosis of peripheral pulmonary lesion: sensitivity and complications

Background The purpose of the current study was to clarify the sensitivity and complication rate of the radial (endobronchial ultrasound, EBUS) without the use of guide-sheath (GS) and fluoroscopy for lung cancer (LC), by measuring the distance from the orifice of the bronchus to the pulmonary lesion, as well as to analyze factors that can predict the diagnostic outcome. Materials and methods A total of 147 patients with peripheral pulmonary lesions (PPL) underwent radial EBUS-guided transbronchial biopsy (TBB) in between August 1, 2013, and August 31, 2014. We analyzed retrospectively radiological data, diagnostic work-up in everyday clinical settings, final diagnosis and complication rates, as well as factors influencing the diagnostic outcome. Results Around 63.9% of PPLs were visualized by ultrasound. A definitive malignant diagnosis was established in 39 patients (26.5%) using radial EBUS. In the remaining 108 patients, additional procedures were performed. We missed LC diagnosis in 40 cases that results in a sensitivity of 49%. For malignant lesions visualized by radial EBUS, the sensitivity was 60%, compared with 24% for not visualized lesions. For malignant lesions, logistic regression was performed to identify the factors that had significant influence on visualization of the lesion and on diagnostic yield. Logistic regression analysis showed significant odds ratios (OR) for visualization depending on location of the lesion; upper lobe lesions were identified more frequent with OR of 3.85 (95% CI 1.42 – 10.98, p=0.009). Size above 30 mm had a non-significant OR of 2.11 (95% CI 0.80−5.73, p=0.134) for visualization. Diagnostic yield was only significantly influenced by visualization with the radial EBUS, OR 3.70 (95% CI 1.35−11.02, p=0.014). Location (p=0.745) and size above 30 mm (p=0.308) showed no significant increase in diagnostic yield. Other lesion characteristics defined on computed tomography, such as distance to carina and pleura, did not show any significant influence on the diagnostic yield. The complications rate was low with three cases of pneumothorax. Conclusion Radial EBUS has definitely its place in the diagnostic work-up of PPL, especially for the lesions that can be visualized by radial ultrasound. However, prospective randomized controlled studies are necessary to raise the diagnostic yield and to define factors that can predict the outcome, which will consequently enable selection of the ‘right’ patients for this diagnostic procedure.

Time-Dependent Decline in Multifocal Electroretinogram Requires Faster Recording Procedures in Anesthetized Pigs

Purpose The time-dependent effect of anesthetics on the retinal function is debated. We hypothesize that in anesthetized animals there is a time-dependent decline that requires optimized multifocal electroretinogram (mfERG) recording procedures. Methods Conventional and four-frame global-flash mfERG recordings were obtained approximately 15, 60, and 150 minutes after the induction of propofol anesthesia (20 pigs) and isoflurane anesthesia (nine pigs). In six of the propofol-anesthetized pigs, the mfERG recordings were split in 3-minute segments. Two to 4 weeks after initial recordings, an intraocular injection of tetrodotoxin (TTX) was given and the mfERG was rerecorded as described above. Data were analyzed using mixed models in SAS statistical software. Results Propofol significantly decreases the conventional and global-flash amplitudes over time. The only significant effect of isoflurane is a decrease in the global-flash amplitudes. At 15 minutes after TTX injection several of the mfERG amplitudes are significantly decreased. There is a linear correlation between the conventional P1 and the global-flash DR mfERG-amplitude (R2 = 0.82, slope = 0.72, P < 0.0001). There is no significant difference between the 3-minute and the prolonged mfERG recordings for conventional amplitudes and the global-flash direct response. The global flash–induced component significantly decreases with prolonged mfERG recordings. Conclusions A 3-minute mfERG recording and a single stimulation protocol is sufficient in anesthetized pigs. Recordings should be obtained immediately after the induction of anesthesia. The effect of TTX is significant 15 minutes after injection, but is contaminated by the effect of anesthesia 90 minutes after injection. Therefore, the quality of mfERG recordings can be further improved by determining the necessary time-of-delay from intraocular injection of a drug to full effect. Translational Relevance General anesthesia is a possible source of error in mfERG recordings. Therefore, it is important to investigate the translational relevance of the results to mfERG recordings in children in general anesthesia.

Small airway dysfunction in well-treated never-smoking HIV-infected individuals

Global projections from the World Health Organization rank chronic obstructive pulmonary disease (COPD) and HIV as the third and eighth leading causes of death by 2030, respectively [1]. An increasingly large number of individuals will consequently face a double burden of disease. The incidence of COPD is relatively high in the HIV-infected population [2], and HIV has been shown to be an independent risk factor [3, 4]. Well preserved spirometry but evidence of small-airway dysfunction in never-smoking HIV-infected individuals http://ow.ly/oZCC308iUpo

Localization, distribution, and connectivity of neuropeptide Y in the human and porcine retinas-A comparative study

Neuropeptide Y (NPY) is a peptide neurotransmitter abundantly expressed in the mammalian retina. Since its discovery, NPY has been studied in retinas of several species, but detailed characterization of morphology, cell‐type, and connectivity has never been conducted in larger mammals including humans and pigs. As the pig due to size and cellular composition is a well‐suited animal for retinal research, we chose to compare the endogenous NPY system of the human retina to that of pigs to support future research in this field. In the present study, using immunohistochemistry, confocal microscopy and 3D reconstructions, we found NPY to be expressed in GABAergic and calretinin‐immunoreactive (‐ir) amacrine cells of both species as well as parvalbumin‐ir amacrine cells of humans. Furthermore, we identified at least two different types of medium‐ to wide‐field NPY‐ir amacrine cells. Finally, we detected likely synaptic appositions between the NPY‐ir amacrine cells and melanopsin‐ and nonmelanopsin‐ir ganglion cells, GABAergic and dopaminergic amacrine cells, rod bipolar cells, and horizontal cells, suggesting that NPY‐ir cells play diverse roles in modulation of both image and non‐image forming retinal signaling. These findings extend existing knowledge on NPY and NPY‐expressing cells in the human and porcine retina showing a high degree of comparability. The extensive distribution and connectivity of NPY‐ir cells described in the present study further highlights the potential importance of NPY signaling in retinal function.

Increased endothelin-1-mediated vasoconstriction after organ culture in rat and pig ocular arteries can be suppressed with MEK/ERK1/2 inhibitors

Even though retinal vascular changes following ischaemia have been poorly understood, the upregulation of vasoconstrictive endothelin‐1 (ET‐1) receptors (ETA/ETB) following global cerebral ischaemia has been described. The aim of this study was to investigate whether or not the MEK/ERK1/2 pathway is involved in the observed upregulation and whether specific MEK/ERK1/2 inhibitors U0126 and trametinib can prevent it.

Early Discontinuation of Montelukast Treatment: A Danish Nationwide Utilization Study

Montelukast, a leukotriene receptor antagonist, was marketed in 1998 as an oral supplementary treatment to patients with mild to moderate asthma. The aim of this study was to describe the early discontinuation pattern among montelukast users in Denmark in the period of 1 March 1998 to 31 December 2016, and to identify demographic characteristics possibly associated with early discontinuation. This nationwide drug utilization study was based on data collected from three nationwide Danish registers. All montelukast users who redeemed at least one prescription in the study period were identified. Early discontinuation was defined as failing to fill a second prescription for montelukast within at least a year after the initial montelukast prescription. Among 135,271 included montelukast users, 47,480 (35%) discontinued the use of montelukast after a single redeemed prescription. The trend in early discontinuation increased throughout the years. The most predominant demographic risk factors for early discontinuation were prescription for only nasal topical anti‐allergic treatment up to a year prior to montelukast initiation [adjusted odds ratio (OR) 2.25; 95% confidence interval (CI) 2.13–2.38], as well as suspected off‐label use (adjusted OR 2.02; 95% CI 1.97–2.08). Several risk factors were associated with a decreased risk of early discontinuation; most pronounced was a prescription of inhaled corticosteroids within a year up to montelukast initiation [adjusted OR 0.47 (95% CI 0.46–0.49)]. Early discontinuation was more pronounced after patent expiry in 2012 [adjusted OR 1.42 (95% CI 1.38–1.45)]. In conclusion, we found that early montelukast discontinuation increased during the last 19 years. Appropriateness of the treatment indication as estimated by concomitant prescription of adequate inhalation therapy was associated with a low risk of early discontinuation. A more pronounced early discontinuation was observed after patent expiry in 2012, which could reflect a more liberal approach to montelukast prescription.