Short-circuit Current Measurements Research Articles

Towards in vivo Bronchoscopic Functional CFTR Assessment using a Short Circuit Current Measurement Probe.

The epithelial lining of luminal organs provides an immune barrier against external factors and regulates transport of nutrients, ions, and water into the body. Several conditions are associated with a breakdown or dysfunction of the epithelial lining. Short circuit current (Isc) measurement using a bulky, expensive, and hard to deploy system known as the Ussing chamber is the gold standard for evaluation of epithelial transport function but requires tissue excision. We demonstrated the ability of the Isc probe to measure Isc in normal wild type (WT) versus reduced CFTR function knockout (KO) rats as a relevant animal model for testing ion channel function.

Ivacaftor ameliorates mucus burden, bacterial load, and inflammation in acute but not chronic P. aeruginosa infection in hG551D rats

BackgroundNewly approved highly effective modulation therapies (HEMT) have been life-changing for people with CF. Although these drugs have resulted in significant improvements in lung function and exacerbation rate, bacterial populations in the lung have not been eradicated. The mechanisms behind the continued colonization are not completely clear.MethodsWe used a humanized rat to assess the effects of ivacaftor therapy on infection outcomes. Rats harbor an insert expressing humanized CFTR cDNA, including the G551D mutation. hG551D rats were treated with ivacaftor either during or before infection with P. aeruginosa. The response to infection was assessed by bacterial burden in the lung and mucus burden in the lung.ResultsWe found that hG551D rats treated with ivacaftor had reduced bacteria present in the lung in the acute phase of the infection but were not different than vehicle control in the chronic phase of the infection. Similarly, the percentage of neutrophils in the airways were reduced at the acute, but not chronic, timepoints. Overall weight data indicated that the hG551D rats had significantly better weight recovery during the course of infection when treated with ivacaftor. Potentiation of the G551D mutation with ivacaftor resultant in short-circuit current measurements equal to WT, even during the chronic phase of the infection. Despite the persistent infection, hG551D rats treated with ivacaftor had fewer airways with mucus plugs during the chronic infection.ConclusionsThe data indicate that the hG551D rats have better outcomes during infection when treated with ivacaftor compared to the vehicle group. Rats have increased weight gain, increased CFTR protein function, and decreased mucus accumulation, despite the persistence of infection and inflammation. These data suggest that ivacaftor improves tolerance of infection, rather than eradication, in this rat model.

Establishment of a conditionally reprogrammed primary eccrine sweat gland culture for evaluation of tissue-specific CFTR function

BackgroundSweat chloride concentration is used both for CF diagnosis and for tracking CFTR modulator efficacy over time, but the relationship between sweat chloride and lung health is heterogeneous and informed by CFTR genotype. Here, we endeavored to characterize ion transport in eccrine sweat glands (ESGs). MethodsFirst, ESGs were microdissected from a non-CF skin donor to analyze individual glands. We established primary cultures of ESG cells via conditional reprogramming for functional testing of ion transport by short circuit current measurement and examined cell composition by single-cell RNA-sequencing (scRNA-seq) comparing with whole dissociated ESGs. Secondly, we cultured nasal epithelial (NE) cells and ESGs from two people with CF (pwCF) to assess modulator efficacy. Finally, NEs and ESGs were grown from one person with the CFTR genotype F312del/F508del to explore genotype-phenotype heterogeneity. ResultsESG primary cells from individuals without CF demonstrated robust ENaC and CFTR function. scRNA-seq demonstrated both secretory and ductal ESG markers in cultured ESG cells. In both NEs and ESGs from pwCF homozygous for F508del, minimal baseline CFTR function was observed, and treatment with CFTR modulators significantly enhanced function. Notably, NEs from an individual bearing F312del/F508del exhibited significant baseline CFTR function, whereas ESGs from the same person displayed minimal CFTR function, consistent with observed phenotype. ConclusionsThis study has established a novel primary culture technique for ESGs that allows for functional ion transport measurement to assess modulator efficacy and evaluate genotype-phenoytpe heterogeneity. To our knowledge, this is the first reported application of conditional reprogramming and scRNA-seq of microdissected ESGs.

Embroidery Triboelectric Nanogenerator for Energy Harvesting.

Triboelectric nanogenerators (TENGs) are devices that efficiently transform mechanical energy into electrical energy by utilizing the triboelectric effect and electrostatic induction. Embroidery triboelectric nanogenerators (ETENGs) offer a distinct prospect to incorporate energy harvesting capabilities into textile-based products. This research work introduces an embroidered triboelectric nanogenerator that is made using polyester and nylon 66 yarn. The ETENG is developed by using different embroidery parameters and its characteristics are obtained using a specialized tapping and friction device. Nine ETENGs were made, each with different stitch lengths and line spacings for the polyester yarn. Friction and tapping tests were performed to assess the electrical outputs, which included measurements of short circuit current, open circuit voltage, and capacitor charging. One sample wearable embroidered energy harvester collected 307.5 μJ (24.8 V) of energy under a 1.5 Hz sliding motion over 300 s and 72 μJ (12 V) of energy through human walking over 120 s. Another ETENG sample generated 4.5 μJ (3 V) into a 1 μF capacitor using a tapping device with a 2 Hz frequency and a 50 mm separation distance over a duration of 520 s. Measurement of the current was also performed at different pressures to check the effect of pressure and validate the different options of the triboelectric/electrostatic characterization device. In summary, this research explains the influence of embroidery parameters on the performance of ETENG (Embroidery Triboelectric Nanogenerator) and provides valuable information for energy harvesting applications.

Activation of farnesoid X receptor retards expansion of renal collecting duct cell-derived cysts via inhibition of CFTR-mediated Cl- secretion.

The transcription factor farnesoid X receptor (FXR) regulates energy metabolism. Specifically, FXR functions to regulate cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl- secretion in intestinal epithelial cells. Therefore, this study aimed to investigate the role of FXR in CFTR-mediated Cl- secretion in renal tubular cells and to further elucidate its effects on renal cyst formation and growth. CFTR-mediated Cl- transport was evaluated via short-circuit current (ISC) measurements in Madin-Darby canine kidney (MDCK) cell monolayers and primary rat inner medullary collecting duct cells. The role of FXR in renal cyst formation and growth was determined by the MDCK cell-derived cyst model. Incubation with synthesized (GW4064) and endogenous (CDCA) FXR ligands reduced CFTR-mediated Cl- secretion in a concentration- and time-dependent manner. The inhibitory effect of FXR ligands was not due to the result of reduced cell viability and was attenuated by cotreatment with an FXR antagonist. FXR activation significantly decreased CFTR protein but not its mRNA. In addition, FXR activation inhibited CFTR-mediated Cl- secretion in primary renal collecting duct cells. FXR activation decreased ouabain-sensitive ISC without altering Na+-K+-ATPase mRNA and protein levels. Furthermore, FXR activation significantly reduced the number of cysts and renal cyst expansion. These inhibitory effects were correlated with a decrease in the expression of protein synthesis regulators mammalian target of rapamycin/S6 kinase. This study shows that FXR activation inhibits Cl- secretion in renal cells via inhibition of CFTR expression and retards renal cyst formation and growth. The discoveries point to a physiological role of FXR in the regulation of CFTR and a potential therapeutic application in polycystic kidney disease treatment.NEW & NOTEWORTHY The present study reveals that farnesoid X receptor (FXR) activation reduces microcyst formation and enlargement. This inhibitory effect of FXR activation is involved with decreased cell proliferation and cystic fibrosis transmembrane conductance regulator-mediated Cl- secretion in renal collecting duct cells. FXR might represent a novel target for the treatment of autosomal dominant polycystic kidney disease.

Theratyping of the Rare CFTR Genotype A559T in Rectal Organoids and Nasal Cells Reveals a Relevant Response to Elexacaftor (VX-445) and Tezacaftor (VX-661) Combination.

Despite the promising results of new CFTR targeting drugs designed for the recovery of F508del- and class III variants activity, none of them have been approved for individuals with selected rare mutations, because uncharacterized CFTR variants lack information associated with the ability of these compounds in recovering their molecular defects. Here we used both rectal organoids (colonoids) and primary nasal brushed cells (hNEC) derived from a CF patient homozygous for A559T (c.1675G>A) variant to evaluate the responsiveness of this pathogenic variant to available CFTR targeted drugs that include VX-770, VX-809, VX-661 and VX-661 combined with VX-445. A559T is a rare mutation, found in African-Americans people with CF (PwCF) with only 85 patients registered in the CFTR2 database. At present, there is no treatment approved by FDA (U.S. Food and Drug Administration) for this genotype. Short-circuit current (Isc) measurements indicate that A559T-CFTR presents a minimal function. The acute addition of VX-770 following CFTR activation by forskolin had no significant increment of baseline level of anion transport in both colonoids and nasal cells. However, the combined treatment, VX-661-VX-445, significantly increases the chloride secretion in A559T-colonoids monolayers and hNEC, reaching approximately 10% of WT-CFTR function. These results were confirmed by forskolin-induced swelling assay and by western blotting in rectal organoids. Overall, our data show a relevant response to VX-661-VX-445 in rectal organoids and hNEC with CFTR genotype A559T/A559T. This could provide a strong rationale for treating patients carrying this variant with VX-661-VX-445-VX-770 combination.

Probenecid slows disease progression in a murine model of autosomal dominant polycystic kidney disease.

Development of autosomal dominant polycystic kidney disease (ADPKD) involves renal epithelial cell abnormalities. Cystic fluid contains a high level of ATP that, among other effects, leads to a reduced reabsorption of electrolytes in cyst-lining cells, and thus results in cystic fluid accumulation. Earlier, we demonstrated that Pkd1RC/RC mice, a hypomorphic model of ADPKD, exhibit increased expression of pannexin-1, a membrane channel capable of ATP release. In the current study, we found that human ADPKD cystic epithelia have higher pannexin-1 abundance than normal collecting ducts. We hypothesized that inhibition of pannexin-1 function with probenecid can be used to attenuate ADPKD development. Renal function in male and female Pkd1RC/RC and control mice was monitored between 9 and 20 months of age. To test the therapeutic effects of probenecid (a uricosuric agent and a pannexin-1 blocker), osmotic minipumps were implanted in male and female Pkd1RC/RC mice, and probenecid or vehicle was administered for 42 days until 1 year of age. Probenecid treatment improved glomerular filtration rates and slowed renal cyst formation in male mice (as shown in histopathology). The mechanistic effects of probenecid on sodium reabsorption and fluid transport were tested on polarized mpkCCDcl4 cells subjected to short-circuit current measurements, and in 3D cysts grown in Matrigel. In the mpkCCDcl4 epithelial cell line, probenecid elicited higher ENaC currents and attenuated in vitro cyst formation, indicating lower sodium and less fluid retention in the cysts. Our studies open new avenues of research into targeting pannexin-1 in ADPKD pathology.

An improved Fractional MPPT Method by Using a Small Circle Approximation of the P–V Characteristic Curve

This paper presents an analytical solution to the maximum power point tracking (MPPT) problem for photovoltaic (PV) applications in the form of an improved fractional method. The proposal makes use of a mathematical function that describes the relationship between power and voltage in a PV module in a neighborhood including the maximum power point (MPP). The function is generated by using only three points of the P–V curve. Next, by using geometrical relationships, an analytical value for the MPP can be obtained. The advantage of the proposed technique is that it provides an explicit mathematical expression for calculation of the voltage at the maximum power point (vMPP) with high accuracy. Even more, complex calculations, manufacturer data, the measurements of short circuit current (iSC) and open-circuit voltage (vOC) are not required, making the proposal less invasive than other solutions. The proposed method is validated using the P–V curve of one PV module. Experimental work demonstrates the speed in the calculation of vMPP and the feasibility of the proposed solution. In addition, this MPPT proposal requires only the typical and available measurements, namely, PV voltage and current. Consequently, the proposed method could be implemented in most PV applications.

A New Method for Triggering Lithium-Ion Cell Internal Short Circuit (ISC) While Monitoring the ISC Current

Internal short circuit (ISC) is a critical failure mechanism for lithium-ion cells that can lead to disastrous thermal runaway. Therefore, great effort has been made to understand its mechanisms by purposefully triggering ISC through various methods1, 2, such as embedding a nickel particle3 or a wax covered copper pad4 inside lithium-ion cells. While these methods have been successful in triggering ISC, none of them allows measurement of ISC current, a critical parameter that influences heat generation and risk of thermal runaway. Alternatively, Feng et al.5 reported a method of placing a resistor between two parallel-connected cells and using the resistor to externally short circuit the cells. This method could allow measurement of short circuit current, but the resistor is placed between two cells rather than between electrode layers to create different types of ISC6. Inspired by this method5 and the established ISC methods3, 4, here we report a new method that not only triggers lithium-ion cell ISC but also monitors ISC current.As shown schematically in Figure 1, the method works by inserting a pair of small nickel pads inside a lithium-ion cell. One pad is between cathode and separator. The other is between anode and separator. Then the pads are connected electronically outside the cell through insulated metal wires, a switch and a current sensor. Once the switch is closed, the anode and cathode will be shorted at the pad region to form an Anode-Cathode type ISC. The ISC current is forced to flow through the external circuit to be measured by the current sensor. The resistance of the external circuit is much lower than the resistance between nickel pads and their corresponding electrode, so heat generation is focused inside the cell at the pad region as in an ISC scenario. By adjusting dimension of the nickel pads and/or the pressure applied to the pad region, the ISC resistance can be adjusted for investigation of its effects. Furthermore, by connecting one of the pads electronically to the opposite tab, the Anode-Aluminum type ISC and the Cathode-Copper type ISC, can be created. Alternatively, these types of ISC can be created by removing part of electrode coating and placing one of the Ni pads to be in direct contact with current collector. In addition, by embedding thermocouples inside the cell7, temperature distributions can be simultaneously measured for understanding of electrochemically-thermally coupled phenomena during ISC.Figure 2 shows preliminary results obtained from a prototype lithium-ion cell using this new method. The cell has a single unit of electrodes and a nominal capacity of 0.02 Ah. Three types of ISC were created, including Anode-Cathode, Anode-Aluminum and Cathode-Copper. As expected, the Anode-Cathode type ISC had the smallest current while the Anode-Aluminum type ISC had the highest current6, which can be attributed to the high resistance of cathode and the contact resistance between nickel pad and electrode. More results and analysis will be presented. References X. Lai, C. Jin, W. Yi, X. Han, X. Feng, Y. Zheng and M. Ouyang, Energy Storage Materials, 35, 470 (2021).G. Zhang, X. Wei, X. Tang, J. Zhu, S. Chen and H. Dai, Renewable and Sustainable Energy Reviews, 141, 110790 (2021).IEEE, IEEE Std 1625-2008 (Revision of IEEE Std 1625-2004), 1 (2008).E. Darcy and M. Keyser, On-Demand Cell Internal Short Circuit Device, in Power Sources Conference 2014; 9-12 Jun. 2014; , Orlando, FL; United States (2014).X. Feng, X. He, L. Lu and M. Ouyang, Journal of The Electrochemical Society, 165, A155 (2018).S. Santhanagopalan, P. Ramadass and J. Zhang, Journal of Power Sources, 194, 550 (2009).S. Huang, Z. Du, Q. Zhou, K. Snyder, S. Liu and G. Zhang, Journal of The Electrochemical Society, 168, 090510 (2021). Figure 1

Hericium caput-medusae (Bull.:Fr.) Pers. fermentation concentrate polysaccharides improves intestinal bacteria by activating chloride channels and mucus secretion

Ethnopharmacological relevanceAs a traditional edible fungus in China and many other Asian countries, Hericium caput-medusae (Bull. Fr.) Pers. is widely used to improve the health of the gastrointestinal tract. For example, the drug “Weilexin Granules” is mainly composed of H. caput-medusae (Bull. Fr.) Pers. fermentation concentrate. However, the mechanism of action remains to be elucidated. Aims of the studyThe purpose of this study was to assess whether polysaccharides from H. caput-medusae (Bull. Fr.) Pers. fermentation concentrate (HFP) exerts a gut protective effect and a regulatory effect on the intestinal microbiota through the chloride channels and mucus secretion. Materials and methodsHFP was extracted, characterized and different concentrations of HFP (100, 200, 400 mg/kg) were administered to mice for 14 days. The changes in gut microbiota were observed via 16S high throughput sequencing. Short-chain fatty acids (SCFAs) was detected by GC-MS. AB-PAS staining was used to observe the secretion of mucus. The chloride channel activity and protein expression were verified by short-circuit current measurement and Western blot. ResultsHFP regulated the abundance of gut microbiota in mice, with increased levels of Ruminococcaceae and Lachnospiraceae and reduced proportions of Staphylococcus and Enterobacter. HFP enhanced mucus volume as well as increased intestinal fluid secretion by activating the chloride channels. In addition, short-circuit current experiments also proved that HFP activates Cl⁻ currents targeting cystic fibrosis transmembrane conductance regulator (CFTR) and Anoamin1 (ANO1). ConclusionIn conclusion, HFP might increase intestinal fluid secretion by promoting Cl⁻ secretion, which in turn advanced mucus hydration as well as regulated gut microbiota to improve intestinal health. Therefore, H. caput-medusae (Bull. Fr.) Pers. could be potentially used in the regulation of intestinal secretion and microbes.

Analysis of the Operation of Cascade Current Transformers for Measurements of Short-Circuit Currents with a Non-Periodic Component with a Large Time Constant of Its Decay

Simulations of emergency states and tests of resistance of electrical devices to emergencies are performed in specialized high-power laboratories, the so-called short-circuit laboratories. For most electrical power devices, such measurements are required by international standards. The basic equipment of short-circuit testing laboratories consists of current transformers for measuring short-circuit currents. These transformers should not only enable the accurate conversion of sinusoidal currents—which is typical for conventional current transformers, but also asymmetrical short-circuit currents containing an aperiodic component, which classic current transformers cannot reproduce. Therefore, manufacturers and designers try to meet the market demands and design these special class 0.2 current transformers. To meet the high technical requirements, the field-circuit method with three-dimensional space–time analysis of electromagnetic fields was used during design, considering physical phenomena in ferromagnetic cores (i.e., hysteresis and eddy current losses) and the load of the secondary winding of the current transformer by the measurement system. The article presents simulations of secondary currents for the short-circuit current transformer model, and the results were confirmed by measurements and oscillograms of the currents flowing in the windings of the real model. The prototype of the designed short-circuit transformer meets the IEC/EN standard requirements. When measuring harmonic currents, the transformation errors meet the requirements of class 0.2. During the short-circuit current waveforms, the maximum instantaneous peak error does not exceed 1% of the error for all the subsequent maxima of the current waveform during the specified transient switching cycle. In comparison, the standard allows this error to be 10%.

Molecular dynamics and functional characterization of I37R-CFTR lasso mutation provide insights into channel gating activity

SummaryCharacterization of I37R, a mutation located in the lasso motif of the CFTR chloride channel, was conducted by theratyping several CFTR modulators from both potentiator and corrector classes. Intestinal current measurements in rectal biopsies, forskolin-induced swelling (FIS) in intestinal organoids, and short circuit current measurements in organoid-derived monolayers from an individual with I37R/F508del CFTR genotype demonstrated that the I37R-CFTR results in a residual function defect amenable to treatment with potentiators and type III, but not type I, correctors. Molecular dynamics of I37R using an extended model of the phosphorylated, ATP-bound human CFTR identified an altered lasso motif conformation which results in an unfavorable strengthening of the interactions between the lasso motif, the regulatory (R) domain, and the transmembrane domain 2 (TMD2). Structural and functional characterization of the I37R-CFTR mutation increases understanding of CFTR channel regulation and provides a potential pathway to expand drug access to CF patients with ultra-rare genotypes.

Predicting Early EVA Degradation in Photovoltaic Modules From Short Circuit Current Measurements

One of the common failures in photovoltaic modules is the degradation of the ethylene-vinyl acetate (EVA) encapsulant due to prolonged ultraviolet exposure and other environmental stress factors, such as temperature and humidity. Experimental studies have shown that significant reduction in the optical transmission due to EVA degradation leads to loss in the available power by more than 50%. In this article, a novel approach to predict the early degradation of EVA encapsulant is proposed by correlating EVA degradation with short-circuit current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</sub> ). An electrical circuit simulator, simulation program with integrated circuit emphasis (SPICE), is used to evaluate the short-circuit current obtained under varying optical transmission caused by EVA discoloration. The simulation follows three steps: simulation of the transmitted solar spectrum; simulation of the spectral short-circuit current density; and simulation of the current-voltage (I-V) curve to obtain short-circuit current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</sub> ), maximum power output (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ), open-circuit voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> ) and fill factor. Results show that the reduction in short-circuit current due to EVA degradation differs from the reductions expected due to a spectrally-uniform reduction of intensity of the solar irradiance. Both types of variation are linear, however, the slope due to EVA degradation is larger than the slope obtained for normal intensity variations in the solar irradiance. This model, when applied in conjunction with solar irradiance measurements, can predict early onset of EVA encapsulant failure, thereby enabling preventative measures to be taken.

Abstract MP35: Pharmacological Inhibition And Knockout Of K ir 7.1 Does Not Affect The Development Of Salt-Sensitive Hypertension In The Dahl SS Rat

Ion channels play a vital role in the kidney’s ability to maintain electrolyte homeostasis, and mutations of certain inwardly rectifying K + channels (K ir ) have been associated with various tubulopathies that can cause salt-wasting and as a consequence, low blood pressure. K ir 7.1 is a member of the K ir family, that helps maintain resting membrane potential; however, its role in the kidney is not well understood. Immunohistochemistry in the kidney confirmed that K ir 7.1 is expressed in both aquaporin 2 and sodium chloride co-transporter positive cells, suggesting it may affect distal tubule K + handling. We hypothesized that K ir 7.1 is involved in renal K + homeostasis and may influence the development of salt-sensitive (SS) hypertension. To examine the role of K ir 7.1 during the development of SS hypertension, we used both a genetic knockout of the gene encoding K ir 7.1, Kcnj13 , on the Dahl SS background and pharmacological inhibition; SS Kcnj13-/- was lethal and we used SS Kcnj13+/- . Mean arterial pressure (MAP) in response to a high salt diet was determined by telemetry or arterial catheter. In the genetic model, there was no difference in MAP development between wild type and SS Kcnj13+/- rats (153±6 vs. 159±7, mmHg; n=11 for each group) after 3 weeks on a 4% NaCl diet. Additionally, there were no differences in K + or Na + urinary excretion in WT vs. SS Kcnj13+/- . For the pharmacological studies, ML418, a novel and highly specific K ir 7.1 inhibitor, was administered daily by i.v. infusion during 2 weeks of 8% NaCl diet. While no significant differences in MAP or K + excretion were observed between vehicle or drug treated rats, administration of ML418 had significantly increased urinary Na + excretion (197±54 vs. 333±21, Na/Cre, vehicle vs. ML418; n≥3 for each group, p=0.02). Moreover, equivalent short circuit current measurements of polarized mCCD cells demonstrated that K ir 7.1 antagonism by ML418 reduced vectoral Na + transport. Overall, these results indicate that K ir 7.1 can impact renal Na + homeostasis, but loss of basolateral K ir 7.1 conductance is insufficient to alter development of hypertension, likely due to compensation by the primary basolateral K ir ’s in the distal nephron such as K ir 4.1 and K ir 5.1.

A Precision Medicine Approach to Optimize Modulator Therapy for Rare CFTR Folding Mutants

Trikafta, a triple-combination drug, consisting of folding correctors VX-661 (tezacaftor), VX-445 (elexacaftor) and the gating potentiator VX-770 (ivacaftor) provided unprecedented clinical benefits for patients with the most common cystic fibrosis (CF) mutation, F508del. Trikafta indications were recently expanded to additional 177 mutations in the CF transmembrane conductance regulator (CFTR). To minimize life-long pharmacological and financial burden of drug administration, if possible, we determined the necessary and sufficient modulator combination that can achieve maximal benefit in preclinical setting for selected mutants. To this end, the biochemical and functional rescue of single corrector-responsive rare mutants were investigated in a bronchial epithelial cell line and patient-derived human primary nasal epithelia (HNE), respectively. The plasma membrane density of P67L-, L206W- or S549R-CFTR corrected by VX-661 or other type I correctors was moderately increased by VX-445. Short-circuit current measurements of HNE, however, uncovered that correction comparable to Trikafta was achieved for S549R-CFTR by VX-661 + VX-770 and for P67L- and L206W-CFTR by the VX-661 + VX-445 combination. Thus, introduction of a third modulator may not provide additional benefit for patients with a subset of rare CFTR missense mutations. These results also underscore that HNE, as a precision medicine model, enable the optimization of mutation-specific modulator combinations to maximize their efficacy and minimize life-long drug exposure of CF patients.

CFTR function and clinical response to modulators parallel nasal epithelial organoid swelling.

In vitro biomarkers to assess cystic fibrosis transmembrane conductance regulator activity are desirable for precision modulator selection and as a tool for clinical trials. Here, we describe an organoid swelling assay derived from human nasal epithelia using commercially available reagents and equipment and an automated imaging process. Cells were collected in nasal brush biopsies, expanded in vitro, and cultured as spherical organoids or as monolayers. Organoids were used in a functional swelling assay with automated measurements and analysis, whereas monolayers were used for short-circuit current measurements to assess ion channel activity. Clinical data were collected from patients on modulators. Relationships between swelling data and short-circuit current, as well as between swelling data and clinical outcome measures, were assessed. The organoid assay measurements correlated with short-circuit current measurements for ion channel activity. The functional organoid assay distinguished individual responses as well as differences between groups. The organoid assay distinguished incremental drug responses to modulator monotherapy with ivacaftor and combination therapy with ivacaftor, tezacaftor, and elexacaftor. The swelling activity paralleled the clinical response. In conclusion, an in vitro biomarker derived from patients' cells can be used to predict responses to drugs and is likely to be useful as a preclinical tool to aid in the development of novel treatments and as a clinical trial outcome measure for a variety of applications, including gene therapy or editing.

Programmable spectral shaping demonstrated at the solar spectral irradiance distribution.

Highly accurate short-circuit current measurements of photovoltaic devices require spectrally adjustable radiation sources. This paper presents an optical setup, which is able to generate and adjust the spectral irradiance in the wavelength range from 355 nm to 1200 nm with an optical resolution of 7 nm to 15 nm. A grating light valve (GLV) is used as a spectral shaping tool. We prove the highly resolved spectral shaping capability by matching the spectral irradiance of the generated radiation to the AM1.5g reference solar spectral irradiance distribution, slightly smoothed to consider the limited bandwidth of the spectrometer. Remaining deviations are mostly lower than the spectral measurement noise of 0.5 % to 3 %.

Repurposing calcium-sensing receptor agonist cinacalcet for treatment of CFTR-mediated secretory diarrheas.

Diarrhea is a major cause of global mortality, and outbreaks of secretory diarrhea such as cholera remain an important problem in the developing world. Current treatment of secretory diarrhea primarily involves supportive measures, such as fluid replacement. The calcium-sensing receptor (CaSR) regulates multiple biological activities in response to changes in extracellular Ca2+. The FDA-approved drug cinacalcet is an allosteric activator of CaSR used for treatment of hyperparathyroidism. Here, we found by short-circuit current measurements in human colonic T84 cells that CaSR activation by cinacalcet reduced forskolin-induced Cl– secretion by greater than 80%. Cinacalcet also reduced Cl– secretion induced by cholera toxin, heat-stable E. coli enterotoxin, and vasoactive intestinal peptide (VIP). The cinacalcet effect primarily involved indirect inhibition of cystic fibrosis transmembrane conductance regulator–mediated (CFTR-mediated) Cl– secretion following activation of CaSR and downstream phospholipase C and phosphodiesterases. In mice, cinacalcet reduced fluid accumulation by more than 60% in intestinal closed loop models of cholera and traveler’s diarrhea. The cinacalcet effect involved both inhibition of CFTR-mediated secretion and stimulation of sodium-hydrogen exchanger 3–mediated absorption. These findings support the therapeutic utility of the safe and commonly used drug cinacalcet in CFTR-dependent secretory diarrheas, including cholera, traveler’s diarrhea, and VIPoma.

A Novel G542X CFTR Rat Model of Cystic Fibrosis Is Sensitive to Nonsense Mediated Decay.

Nonsense mutations that lead to the insertion of a premature termination codon (PTC) in the cystic fibrosis transmembrane conductance regulator (CFTR) transcript affect 11% of patients with cystic fibrosis (CF) worldwide and are associated with severe disease phenotype. While CF rat models have contributed significantly to our understanding of CF disease pathogenesis, there are currently no rat models available for studying CF nonsense mutations. Here we created and characterized the first homozygous CF rat model that bears the CFTR G542X nonsense mutation in the endogenous locus using CRISPR/Cas9 gene editing. In addition to displaying severe CF manifestations and developmental defects such as reduced growth, abnormal tooth enamel, and intestinal obstruction, CFTR G542X knockin rats demonstrated an absence of CFTR function in tracheal and intestinal sections as assessed by nasal potential difference and transepithelial short-circuit current measurements. Reduced CFTR mRNA levels in the model further suggested sensitivity to nonsense-mediated decay, a pathway elicited by the presence of PTCs that degrades the PTC-bearing transcripts and thus further diminishes the level of CFTR protein. Although functional restoration of CFTR was observed in G542X rat tracheal epithelial cells in response to single readthrough agent therapy, therapeutic efficacy was not observed in G542X knockin rats in vivo. The G542X rat model provides an invaluable tool for the identification and in vivo validation of potential therapies for CFTR nonsense mutations.

Assessment of spectral effects on outdoor characterization of PV modules using silicon reference cells with spectral filters

This article describes outdoor temperature-controlled measurement of various photovoltaic (PV) modules fabricated using different technologies and using reference cells with spectral filters. Short-circuit current measurements of all PV modules and reference cells were recorded simultaneously using 16-bits Keysight digitizers and high-resolution Agilent multimeters. The spectral incompatibility factor was calculated considering the spectral response of each device and the spectrum measured outdoors. Corresponding spectra were also generated by the simple model of atmospheric radiative transfer of the sun SMARTS2 and were additionally used to compare the spectral incompatibility factors. The validation of the measurement method was demonstrated by comparing the incompatibility factor calculated with variation of the short-circuit current relationship between the device under test and the reference cell over time. Additionally, it was evaluated how the relationship between spectral variation of irradiance and the spectral response of different technologies affects the productivity in thin-film modules. Main observation from measurements (performed in Labsol) was that a-Si/μ-Si, CdTe, and triple a-Si junction converted 0.21%, 2.47%, and 3.65% more irradiation into electric current (in summer), respectively, compared to c-Si technology. The PV CIGS module converted on average 0.26% more irradiation into electric current in winter compared to c-Si technology. The results help to understand the spectral effects on the working of outdoor PV module and the relationships between measured and modeled spectra, as well as errors introduced by the spectral incompatibility factor.