Cystic Fibrosis Transmembrane Conductance Regulator Research Articles

Cardiac structure and function in people with cystic fibrosis

Abstract Background Cystic fibrosis (CF) is an autosomal recessive disease affecting multiple organs, however the extent of cardiac involvement in CF is yet to be determined. The remarkable therapeutic advancements with new highly effective CF transmembrane conductance regulator (CFTR) modulator treatment and subsequent increase in life expectancy substantiates further research. Purpose We aimed to explore the prevalence of abnormalities and potential subclinical alterations in cardiac structure and function in adults with CF compared to matched controls and investigate potential cardiovascular risk factors in people with CF (pwCF). Methods In this cross-sectional study, 104 adult pwCF in Denmark underwent clinical and echocardiographic examination. All participants were matched 1:1 with controls from the general population on age and sex. Uni- and multivariable linear regression models with adjustment for heart rate, FEV1, smoking status, hypertension and CF-related diabetes (CFRD) were used to test for differences in echocardiographic parameters between cases and controls. Abnormal cardiac function was defined as left ventricular ejection fraction (LVEF) <50%, left ventricular (LV) global longitudinal strain (GLS) < 16% or presence of diastolic dysfunction. Uni- and multivariable logistic regression models adjusted for age, sex, homozygous genotype, FEV1/FVC, BMI, smoking status, CFRD, pancreatic insufficiency, hypertension, and ischemic heart disease were performed to assess associations between potential risk factors and cardiac dysfunction in CF. Forest plots were constructed to visually represent the findings. Results Of 104 pwCF, 44% were female, mean age was 34 years, 93% received CFTR modulator treatment, and 91% had mutations with only minimal CFTR function (mutation class I-III). The prevalence of abnormal cardiac function in pwCF was 44% versus 22% in controls. Compared to controls, pwCF were found to have smaller LV dimensions, worse LV diastolic function, and more impaired right ventricle (RV) as well as LV systolic function (Table). After multivariable adjustment, LV diastolic function as well as LV and RV systolic function remained impaired in pwCF as compared to controls. Male sex and decreasing FEV1/FVC ratio remained independently associated with abnormal cardiac function in pwCF (male sex: OR 3.94 (1.56; 9.95), p=0.004 and FEV1/FVC ratio: OR 2.05 per 0.1 unit decrease (1.21; 3.52), p=0.008, respectively) (Figure). Conclusion Both left- and right-sided cardiac alterations were found in pwCF. After adjustments for potential risk factors, both RV and LV systolic measures remained altered in pwCF, compared to controls. Male sex and decreasing pulmonary function evaluated by FEV1/FVC-ratio were identified as factors associated with abnormal cardiac function in pwCF.Figure

Study of the genetic and molecular epidemiology of cystic fibrosis based on the patient registry for planning targeted therapy in Russian Federation

Cystic fibrosis (CF) is a genetically inherited disorder characterized by a wide range of clinical manifestations and genetic variations. This study focuses on the genetic and molecular epidemiology of CF in the Russian population, utilizing data from the national CF registry. The birth prevalence of CF in Russia has been analyzed over a span of years, revealing variations in frequency. The study delves into the genetic landscape of CFTR gene variants in Russian patients, showcasing a diverse spectrum with a predominance of severe variants, some of which are rare and distinct from global populations. A total of 233 variants have been documented, exhibiting frequencies ranging from 0.01% to 51.5%, with 47 of these variants remaining uncharted within international genetic databases. As of 2021, CFTR modulator therapy has been introduced for patients under 19 years, heightening the importance of genetic diagnosis. In 2023, more than 1,850 patients under 19 received CFTR modulator therapy. Notably, the impact of complex alleles on disease progression and response to targeted therapies is gaining recognition. Comparisons with European registries highlight distinctive features of the Russian population, such as differences in age distribution among patients. Additionally, the study emphasizes the need to ascertain clinical significance and pathogenicity of newly identified genetic variants, along with exploring their suitability for targeted therapies. The integration of genetic insights into the management of CF offers potential for enhanced personalized therapeutic interventions. In conclusion, this thorough analysis provides a comprehensive understanding of the genetic nuances within the Russian CF population. By illuminating the intricate relationship between genetic variations and disease manifestation, the study underscores the essential role of genetics in shaping therapeutic strategies and improving patient outcomes. Further research and ongoing genetic exploration are crucial for optimizing the care of individuals with CF in the era of evolving therapeutic options.

Genetic and clinical factors influencing CF-associated liver disease: the impact of SERPINA1 variants and CFTR genotypes in Romanian pediatric cystic fibrosis patients

Background. Hepatic disease represents a significant complication in children with cystic fibrosis (CF), yet its relationship with specific genetic factors, including CFTR (Cystic fibrosis transmembrane conductance regulator) mutations and SERPINA1 alleles, is not well understood. This study aims to clarify these associations within a Romanian pediatric CF population. Methods. In this cross-sectional, prospective study, we examined 71 children with CF, comparing those with hepatic disease (n=25) to those without (n=46). We collected comprehensive clinical, biochemical, and genetic data, focusing on CFTR genotypes and SERPINA1 alleles. Key outcomes included the prevalence of hepatic disease in relation to specific genotypes, fibrosis markers, and liver function tests. Results. The DF508/DF508 genotype was the most prevalent, occurring in 49% of the cohort. No significant associations were found between hepatic disease and specific CFTR genotypes or SERPINA1 alleles. However, children with hepatic disease exhibited significantly higher fibrosis scores (APRI and FIB-4), suggesting more advanced liver involvement. Additionally, a slight delay in CF diagnosis was observed in those with hepatic disease, though this difference did not reach statistical significance. Conclusion. This pioneering study in Romania underscores the complexity of hepatic disease in CF. While specific CFTR genotypes and SERPINA1 alleles were not significantly associated with hepatic complications, the findings emphasize the importance of early diagnosis and monitoring using fibrosis markers to identify children at risk for liver involvement.

Case Report: A delicate equilibrium of exocrine pancreatic recovery and hepatotoxicity with elexacaftor/tezacaftor/ivacaftor therapy in a pediatric patient with cystic fibrosis

This case report presents a comprehensive evaluation of the complex balance of therapeutic benefits and potential risks associated with the cystic fibrosis transmembrane conductance regulator (CFTR) modulator elexacaftor/tezacaftor/ivacaftor (ETI) therapy in managing an eight-year-old male with cystic fibrosis (CF) and exocrine pancreatic insufficiency (EPI). While ETI therapy significantly enhanced exocrine pancreatic function, it led to hepatotoxicity, necessitating therapy discontinuation. Attempts to restart ETI at reduced doses were unsuccessful due to persistent hepatic dysfunction. Reduced ETI dosing frequency, implemented due to hepatic dysfunctions, did not result in substantial therapeutic benefits. Clinical markers showed a resurgence of severe EPI and sustained need for gastrostomy tube feeds, with only modest improvement in hepatic function compared to the period following ETI cessation or during prior use of CFTR modulator therapy with lumacaftor/ivacaftor. This case underscores the importance of personalized therapeutic approaches, biomarker-guided monitoring, and multidisciplinary insights to optimize CF management while also highlighting the ongoing need for research to mitigate hepatotoxicity risks and ensure long-term therapeutic efficacy.

Phenotypic Evaluation of Rare Cystic Fibrosis Transmembrane Conductance Regulator Mutation Combinations in People with Cystic Fibrosis in Queensland, Australia.

Background: Cystic fibrosis (CF) is a multisystem disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. We describe the distribution of CFTR mutation profiles in sub-tropical Queensland, Australia, and characterise the phenotypes associated with 'rare' CFTR mutation combinations. Methods: We conducted a retrospective observational study to analyse the CFTR mutation profiles of 322 people with CF (pwCF) under the care of a large adult CF centre in Queensland, Australia. Molecular pathology results were available for all identifiable CFTR mutations. The CFTR2 database was utilised to characterise the less common CFTR mutations to define mutation classes and explore associated phenotypic sequelae. Results: In total, eighty-seven different genotypes were identified within our CF cohort, with the most abundant mutation being the F508del mutation, 298/322 (92.5%). Thirty-six pwCF with CFTR mutations are considered to have 'rare' CFTR mutations, and eleven with previously undefined phenotypes. For these eleven pwCF, late diagnosis in adulthood was confirmed in 5/11 pwCF (45.5%) with CFTR modulator therapy only initiated in 5/11 (45.5%). Conclusions: The profile of more common CFTR genotypes within our cohort of adult pwCF living in Queensland, Australia, generally reflects the global predominance of F508del, G542X, G551D, N1303K, and R117H. The phenotypic heterogeneity of disease seen within the eleven pwCF in our cohort with previously undefined CFTR genotypes highlights that rare mutations can also be associated with severe disease and continue to be at risk of delayed diagnosis. Access to CFTR modulator therapies for this group of pwCF remains limited and should remain a research priority.

Restoring CFTR function with Orkambi decreases the severity of alcohol-induced acute pancreatitis.

Heavy alcohol intake is one of the most common causes of acute pancreatitis (AP). We have previously shown that ethanol (EtOH) decreases the expression and activity of the cystic fibrosis transmembrane conductance regulator (CFTR), which plays a key role in alcohol-induced AP development. The prescription drug, Orkambi (a combination of ivacaftor and lumacaftor) can correct impaired CFTR function and expression in cystic fibrosis (CF) patients. Thus, the present study aimed to investigate whether Orkambi can mitigate alcohol-induced AP. Intact guinea-pig pancreatic ducts were pre-treated with different concentrations of ethanol (EtOH; 30, 50 and 100mm) for 12h alone or in combination with ivacaftor (VX770) and/or lumacaftor (VX-809), and CFTR expression and activity were evaluated by immunostaining and by the patch clamp technique, respectively. Alcoholic AP was induced in Orkambi-treated guinea-pigs, and standard laboratory and histological parameters were measured. Ivacaftor and lumacaftor alone or in combination dose-dependently restored the apical expression and activity of CFTR after EtOH treatment in vitro. Oral administration of Orkambi reduced the severity of alcohol-induced AP and restored impaired CFTR activity and expression. Orkambi is able to restore the CFTR defect caused by EtOH and decreases the severity of alcohol-induced pancreatitis. This is the first in vivo pre-clinical evidence of Orkambi efficacy in the treatment of alcohol-induced AP. KEY POINTS: Acute pancreatitis is one of the leading causes of hospital admission among gastrointestinal diseases in which the lack of a specific drug therapy plays a crucial role. The cystic fibrosis transmembrane conductance regulator (CFTR) plays an essential role in pancreatic ductal HCO3 - secretion; inappropriate CFTR function, as seen in heavy alcohol consumption, increases the risk of pancreatitis development. CFTR modulators are able to prevent the inhibitory effect of ethanol and reduce pancreatic ductal injury and the severity of alcohol-induced pancreatitis. CFTR modulators present a novel option in the pharmacotherapy of alcohol-induced pancreatitis by enhancing pancreatic functions or preventing recurrence.

The RNA Binding Protein Tristetraprolin Contributes to CFTR mRNA Stability in Cystic Fibrosis.

Cystic Fibrosis (CF) is the most common inherited disorder and is characterized by an inflammatory phenotype. Here, we found that in bronchial epithelium reconstituted form lung tissue biopsies from patients with CF, the RNA-binding protein tristetraprolin (TTP), a key regulator of inflammation, is dysregulated in cells that strongly express cytokines and interleukins. TTP activity is regulated by extensive post-translational modifications, particularly phosphorylation. We found that in addition to mRNA downregulation, phosphorylated TTP (which cannot bind to mRNA) accumulated in CF cultures, suggesting that the imbalance in TTP phosphorylation status could contribute to the inflammatory phenotype in CF. We confirmed TTP destabilizing role on IL8 mRNA through its 3'UTR sequence in CF cells. We next demonstrated that TTP phosphorylation is mainly regulated by MK2 through activation of ERK, which also was hyperphosphorylated. TTP is considered a mRNA decay factor with some exception, and we present a new positive role of TTP in CF cultures. We determined that TTP binds to specific ARE motifs on the 3'UTR of mRNA sequences and also, for the first time, to the 3'UTR of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) where TTP binding stabilizes the mRNA level. This study identified new partners that can be targeted in CF and proposes a new way to control CFTR gene expression.

Population Characteristics of the Spectrum and Frequencies of CFTR Gene Mutations in Patients with Cystic Fibrosis from the Republic of Bashkortostan (Russia).

Cystic fibrosis (CF) is one of the most common autosomal-recessive disorders worldwide. The incidence of CF depends on the prevalence of cystic fibrosis transmembrane conductance regulator gene (CFTR) mutations in the population, which is determined by genetic diversity and ethnicity. The search for the causes of mutations in the transmembrane conductance regulator gene (CFTR) was carried out using targeted next-generation sequencing (NGS) on the Illumina platform in patients with cystic fibrosis from the Republic of Bashkortostan (Russia), taking into account the ethnic structure of the sample. A total of 35 distinct causal variants were found in 139 cases from 129 families. Five (F508del, E92K, 3849+10kbC>T, CFTRdele2.3, L138ins) explain 78.7% of identified CF causal alleles. Variants N13103K and 394delTT were found in four families each. Variants 2143delT, S1196X, W1282X, Y84X, G194R, and 1525-1G>A, as well as the two previously described complex alleles-c. [S466X; R1070Q] and str.[G509D;E217G]-were found in two or three families each. Twenty additional variants occurred only once. Variant c.3883_3888dup has not been described previously. Thus, regional and ethnic features were identified in the spectrum of frequencies of pathogenic variants of the CFTR gene in the three major sub-groups of patients-Russians, Tatars, and Bashkirs. Taking into account these results, highlighting the genetic specificity of the region, a more efficient search for CFTR mutations in patients can be performed. In particular it is possible to choose certain test kits for quick and effective genetic screening before use of NGS sequencing.

Mycobacterium avium inhibits protein kinase C and MARCKS phosphorylation in human cystic fibrosis and non-cystic fibrosis cells.

In cystic fibrosis (CF), there is abnormal translocation and function of the cystic fibrosis transmembrane conductance regulator (CFTR) and an upregulation of the epithelial sodium channel (ENaC). This leads to hyperabsorption of sodium and fluid from the airway, dehydrated mucus, and an increased risk of respiratory infections. In this study, we performed a proteomic assessment of differentially regulated proteins from CF and non-CF small airway epithelial cells (SAEC) that are sensitive to Mycobacterium avium. CF SAEC and normal non-CF SAEC were infected with M. avium before the cells were harvested for protein. Protein kinase C (PKC) activity was greater in the CF cells compared to the non-CF cells, but the activity was significantly attenuated in both cell types after infection with M. avium compared to vehicle. Western blot and densitometric analysis showed a significant increase in cathepsin B protein expression in M. avium infected CF cells. Myristoylated alanine rich C-kinase substrate (MARCKS) protein was one of several differentially expressed proteins between the groups that was identified by mass spectrometry-based proteomics. Total MARCKS protein expression was greater in CF cells compared to non-CF cells. Phosphorylation of MARCKS at serine 163 was also greater in CF cells compared to non-CF cells after treating both groups of cells with M. avium. Taken together, MARCKS protein is upregulated in CF cells and there is decreased phosphorylation of the protein due to a decrease in PKC activity and presumably increased cathepsin B mediated proteolysis of the protein after M. avium infection.

Molecular basis for the transcriptional regulation of an epoxide-based virulence circuit in Pseudomonas aeruginosa.

The opportunistic pathogen Pseudomonas aeruginosa infects the airways of people with cystic fibrosis (CF) and produces a virulence factor Cif that is associated with worse outcomes. Cif is an epoxide hydrolase that reduces cell-surface abundance of the cystic fibrosis transmembrane conductance regulator (CFTR) and sabotages pro-resolving signals. Its expression is regulated by a divergently transcribed TetR family transcriptional repressor. CifR represents the first reported epoxide-sensing bacterial transcriptional regulator, but neither its interaction with cognate operator sequences nor the mechanism of activation has been investigated. Using biochemical and structural approaches, we uncovered the molecular mechanisms controlling this complex virulence operon. We present here the first molecular structures of CifR alone and in complex with operator DNA, resolved in a single crystal lattice. Significant conformational changes between these two structures suggest how CifR regulates the expression of the virulence gene cif. Interactions between the N-terminal extension of CifR with the DNA minor groove of the operator play a significant role in the operator recognition of CifR. We also determined that cysteine residue Cys107 is critical for epoxide sensing and DNA release. These results offer new insights into the stereochemical regulation of an epoxide-based virulence circuit in a critically important clinical pathogen.

Genetic diagnosis and outcomes of intracytoplasmic sperm injection in South Chinese patients with congenital bilateral aplasia of the vas deferens

BackgroundObstructive azoospermia commonly is caused by CBAVD(Congenital Bilateral Aplasia of the Vas Deferens), mainly due to the cystic fibrosis transmembrane conductance regulator (CFTR) and adhesion G protein-coupled receptor G2(ADGRG2) mutations. The genetic landscape for Chinese CBAVD patients is unclear, leading to debates over genetic screening, counseling, and assisted reproduction strategies. This study investigates the prevalence of CFTR and ADGRG2 mutations in a southern Chinese cohort of CBAVD patients and evaluates the impact of CFTR mutations on intracytoplasmic sperm injection (ICSI) outcomes.ResultsCFTR mutations were identified in 71.4% (30/42) of CBAVD patients, with a total of 36 CFTR mutation sites across 13 types identified, including two novel mutations. A novel ADGRG2 mutation was also detected. Betweenthe CFTR mutation-CBAVD group and the non-CBAVD OA group, a significant difference was observed only in the 2 Pronuclei(2PN) rate (79.5% vs 86.2%, P = 0.0065), while fertilization rates, pregnancy rates, miscarriage rates, and live birth rates showed no significant differences. Between the CFTR mutation-CBAVD group and the CBAVD group without CFTR mutation, there were no significant differences in fertilization rates, 2PN rates, pregnancy rates, miscarriage rates, or live birth rates.ConclusionChinese CBAVD patients primarily exhibit mutations in the CFTR and ADGRG2 genes. Therefore, targeted gene testing for CFTR and ADGRG2 is more suitable compared to WES for CBAVD patients. Considering that the genetic factors of approximately 30% of CBAVD patients remain unknown, it is recommended to perform massive parallel sequencing for patients who test negative for CFTR and ADGRG2 gene screening. Despite these genetic factors, ICSI outcomes were not adversely affected, except for the 2PN rate. However, genetic counseling remains crucial for Chinese CBAVD patients before undergoing assisted reproduction.

Ribosomal frameshifting selectively modulates the assembly, function, and pharmacological rescue of a misfolded CFTR variant

The cotranslational misfolding of the cystic fibrosis transmembrane conductance regulator chloride channel (CFTR) plays a central role in the molecular basis of CF. The misfolding of the most common CF variant (ΔF508) remodels both the translational regulation and quality control of CFTR. Nevertheless, it is unclear how the misassembly of the nascent polypeptide may directly influence the activity of the translation machinery. In this work, we identify a structural motif within the CFTR transcript that stimulates efficient -1 ribosomal frameshifting and triggers the premature termination of translation. Though this motif does not appear to impact the interactome of wild-type CFTR, silent mutations that disrupt this RNA structure alter the association of nascent ΔF508 CFTR with numerous translation and quality control proteins. Moreover, disrupting this RNA structure enhances the functional gating of the ΔF508 CFTR channel at the plasma membrane and its pharmacological rescue by the CFTR modulators contained in the CF drug Trikafta. The effects of the RNA structure on ΔF508 CFTR appear to be attenuated in the absence of the ER membrane protein complex, which was previously found to modulate ribosome collisions during "preemptive quality control" of a misfolded CFTR homolog. Together, our results reveal that ribosomal frameshifting selectively modulates the assembly, function, and pharmacological rescue of a misfolded CFTR variant. These findings suggest that interactions between the nascent chain, quality control machinery, and ribosome may dynamically modulate ribosomal frameshifting in order to tune the processivity of translation in response to cotranslational misfolding.

The Role of Cystic Fibrosis Transmembrane Conductance Regulator in Skeletal Muscle Contractile Function

Purpose: Genetic mutations in cystic fibrosis (CF) result in CF transmembrane conductance regulator (CFTR) dysfunction. CFTR is expressed in human skeletal muscle; its effect on skeletal muscle abnormalities is unknown. The study objective is to investigate the role of CFTR in skeletal muscle contractile function. Methods: We conducted a prospective, cross-sectional study comparing 34 adults with minimal and 18 with residual function CFTR mutations, recruited from Toronto Adult CF Centre, St. Michael's Hospital, Unity Health Toronto. Quadriceps, biceps brachii, and handgrip strength was measured with dynamometers; leg muscle power with the stair climb power test. Quadriceps muscle contractility was determined by quadriceps muscle strength normalized to quadriceps muscle size, measured with ultrasound images. Multivariable regression was used for analysis. Results: People with residual function CFTR mutations had higher quadriceps muscle torque normalized to quadriceps layer thickness and to rectus femoris cross-sectional area by 27.5 Nm/cm [95% CI (2.2, 52.8) Nm/cm, P = .034] and 5.6 Nm/cm2 [95% CI (0.3, 10.9) Nm/cm2, P = .041], respectively, compared with those with minimal function CFTR mutations. There were no differences in quadriceps muscle torque (P = .58), leg muscle power (P = .47), biceps brachii muscle force (P = .14), or handgrip force (P = .12) between the 2 mutation groups. Conclusions: CFTR protein may play a role in muscle contractility, implying a limited capacity to exert muscle force per unit of muscle size in people with CF. This suggests that building a greater muscle mass through resistance exercises focusing on muscle hypertrophy in exercise prescription may improve muscle strength in people with CF.

Current landscape of cystic fibrosis gene therapy.

Cystic fibrosis is a life-threatening disease that is caused by mutations in CFTR, a gene which encodes an ion channel that supports proper function of several epithelial tissues, most critically the lung. Without CFTR, airway barrier mechanisms are impaired, allowing for chronic, recurrent infections that result in airway remodeling and deterioration of lung structure and function. Small molecule modulators can rescue existing, defective CFTR protein; however, they still leave a subset of people with CF with no current disease modifying treatments, aside from lung transplantation. Gene therapy directed to the lung is a promising strategy to modify CF disease in the organ most associated with morbidity and mortality. It is accomplished through delivery of a CFTR transgene with an airway permissive vector. Despite more than threedecades of research in this area, a lung directed gene therapy has yet to be realized. There is hope that with improved delivery vectors, sufficient transduction of airway cells can achieve therapeutic levels of functional CFTR. In order to do this, preclinical programs need to meet a certain level of CFTR protein expression in vitro and in vivo through improved transduction, particularly in relevant airway cell types. Furthermore, clinical programs must be designed with sensitive methods to detect CFTR expression and function as well as methods to measure meaningful endpoints for lung structure, function and disease. Here, we discuss the current understanding of how much and where CFTR needs to be expressed, the most advanced vectors for CFTR delivery and clinical considerations for detecting CFTR protein and function in different patient subsets.

Reporting three rare pathogenic variants at the CFTR gene in two unrelated Iranian Azeri children with cystic fibrosis

BackgroundCystic fibrosis (CF) is an autosomal recessive inherited life-threatening disease that causes changes in the electrolyte transport system, leading to high absorption of sodium and water. Disease-causing variants of the CFTR gene are responsible for this disease. In the present study, three rare pathogenic variants were identified in two unrelated Iranian Azeri children with CF.Case presentationOne child affected with CF was found to have two rare variants, c.1545_1546delTA and c.3196C > T, detected through Sanger sequencing of the entire coding region and promoter of the CFTR gene. Another patient was identified as compound heterozygous for the variant c.1545_1546delTA and a rare variant, c.2998delA, which has not been previously reported. The variants were found to be in trans, as both parents were heterozygous for the variants.ConclusionThe rare variant c.1545_1546delTA has been previously reported as a known variant in certain populations, including Azeris in northwest Iran. Our results, along with previous findings, suggest that this variant may be considered a founder mutation in specific geographical regions. The variant c.2998delA has not been previously reported as pathogenic. Following the guidelines of the American College of Genetics and Genomics and considering the proband's symptoms, we classified this variant as pathogenic based on criteria PVS1, PS4, PM3, PP1, and PM2. The identified variants in the CFTR gene as well as the previously reported variants could serve as a basis for future genetic counseling and prenatal diagnosis in Iran.

7522 Effects of Trikafta On Bone Mineral Density And Body Composition In Patients With Cystic Fibrosis

Abstract Disclosure: N. Mon: None. S.S. Krishnasamy: None. G. Bakeerathan: None. L. Healy: None. E. Favier: None. S. Foushee: None. Background: Cystic fibrosis related bone disease (CFBD) is a common complication of adult Cystic fibrosis (CF) patients due to calcium, vitamin D and K malabsorption from exocrine pancreatic insufficiency, increased inflammatory cytokines, glucocorticoid therapy, delayed puberty, physical inactivity, and hypogonadism. Newer CF transmembrane conductance regulator (CFTR) modulator therapy elexacaftor/tezacaftor/ivacaftor (Trikafta) has proven benefit in pulmonary and nutritional outcomes. There is limited data on effects of Trikafta on bone health and body composition. The aim is to examine the effects of Trikafta on bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN), and body composition in terms of fat free mass index (FFMI) and fat mass index (FMI) in our CF patients. Method: We conducted a cross sectional and retrospective review of 38 adults with CF (Ages 20-59, 28 males and 10 females) in our CF clinic. Body Mass Index (BMI), Body composition measured by bioelectric impedance analysis, BMD of LS and FN by Dual-energy X-ray absorptiometry, Vitamin D level, and forced expiratory volume in one second (FEV1 % predicted) in patients taking Trikafta were analyzed and compared with control CF group who were not on Trikafta. Results: 38 subjects on Trikafta, aged 33.29 ± 10.36 years with FEV1 % predicted 65.11± 28.14% were studied. Serum 25-hydroxyvitamin D level was 35.92 ± 18.52 ng/dL. Of the 38 study patients, 23 (60.53%) had a diagnosis of CF related diabetes (CFRD). Among the Trikafta cohort, 18 (50%) had low BMD with Z-scores ≤ -2.0 and 7 (19.44%) of them had Z score ≤ -1.0 and > -2.0. Compared with the control group, LS BMD 0.93 ± 0.16 g/cm2 and FN BMD 0.73± 0.13g/cm2 (p >0.05) were not improved significantly. BMI of study population 23.09 ± 4.21 kg/m2 (p <0.05) and FMI 6.11 ± 4.25 kg/m2 (p <0.05) increased significantly; however, there was a decrease in FFMI 9.60 ± 1.44 kg/m2 (p <0.05). Conclusion: Treatment with Trikafta in CF patients was associated with increases in BMI and fat mass index but decrease in fat free mass index. There was no statistically significant difference in BMD at LS and FN in our study cohort. This study has limitations in terms of gender differences within the study cohort, duration of Trikafta use in relation to bone mass, and also extent of glucocorticoid use among the study subjects. Larger prospective clinical trials are needed to study efficacy of Trikafta on CFBD. Presentation: 6/3/2024

A Three-year Longitudinal Assessment of Pseudomonas aeruginosa Antibiotic Susceptibility in Children With Cystic Fibrosis in the Era of Cystic Fibrosis Transmembrane Conductance Regulator Modulator Therapy

fibrosis is a genetic disease characterized by chronic lung infection, often with Pseudomonas aeruginosa, requiring repeated antibiotic treatment for pulmonary exacerbations. In the era of cystic fibrosis transmembrane conductance regulator modulator therapy, we assessed susceptibility to antipseudomonal antibiotics in modulator-eligible and modulator-ineligible children over 3 years and found that P. aeruginosa isolates largely remained susceptible to standard parenteral but not oral antimicrobial agents.

Inflammation-induced loss of CFTR-expressing airway ionocytes in non-eosinophilic asthma.

Severe asthma is a heterogeneous disease with subtype classification according to dominant airway infiltrates, including eosinophilic (Type 2 high), or non-eosinophilic asthma. Non-eosinophilic asthma is further divided into paucigranulocytic or neutrophilic asthma characterized by elevated neutrophils, and mixed Type 1 and Type 17 cytokines in the airways. Severe non-eosinophilic asthma has few effective treatments and many patients do not qualify for biologic therapies. The cystic fibrosis transmembrane conductance regulator (CFTR) is dysregulated in multiple respiratory diseases including cystic fibrosis and chronic obstructive pulmonary disease and has proven a valuable therapeutic target. We hypothesized that the CFTR may also play a role in non-eosinophilic asthma. Patient-derived human bronchial epithelial cells (hBECs) were isolated and differentiated at the air-liquid interface. Single cell RNA-sequencing (scRNAseq) was used to identify epithelial cell subtypes and transcriptional activity. Ion transport was investigated with Ussing chambers and immunofluorescent quantification of ionocyte abundance in human airway epithelial cells and murine models of asthma. We identified that hBECs from patients with non-eosinophilic asthma had reduced CFTR function, and did not differentiate into CFTR-expressing ionocytes compared to those from eosinophilic asthma or healthy donors. Similarly, ionocytes were also diminished in the airways of a murine model of neutrophilic-dominant but not eosinophilic asthma. Treatment of hBECs from healthy donors with a neutrophilic asthma-like inflammatory cytokine mixture led to a reduction in ionocytes. Inflammation-induced loss of CFTR-expressing ionocytes in airway cells from non-eosinophilic asthma may represent a key feature of disease pathogenesis and a novel drug target.

CFTR Exon 10 deleterious mutations in patients with congenital bilateral absence of vas deferens in a cohort of Pakistani patients.

Congenital bilateral absence of vas deferens (CBAVD) is a urological syndrome of Wolffian ducts and is responsible for male infertility and obstructive azoospermia. This study is designed to explore the integrity of exon 10 of CFTR and its role in male infertility in a cohort of CBVAD patients in Pakistan. Genomic DNA was extracted from 17 male patients with CBAVD having clinical symptoms, and 10 healthy controls via phenol-chloroform method. Exon 10 of the CFTR gene was amplified, using PCR with specific primers and DNA screening was done by Sanger sequencing. Sequencing results were analyzed using freeware Serial Cloner, SnapGene, BioEdit and FinchTV. Furthermore, bioinformatics tools were used to analyze the mutations and their impact on the protein function and stability. We have identified 4 mutations on exon 10 of CFTR in 6 out of 17 patients. Two of the mutations were missense variants V456A, K464E, and the other two were silent mutations G437G, S431S. The identified variant V456A was present in 4 of the studied patients. Whereas, the presence of K464E in our patients further weighs on the crucial importance for its strategic location to influence the gene function at post-transcriptional and protein level. Furthermore, Polyphen-2 and SIFT analyze the mutations as harmful and deleterious. The recurrence of V456A and tactically conserved locality of K464E are evidence of their potential role in CBAVD patients and in male infertility. The data can contribute in developing genetic testing and treatment of CBAVD.

Functional and radiological sinonasal outcomes of CFTR modulators for sinus disease in cystic fibrosis: A meta-analysis.

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators improve pulmonary outcomes in cystic fibrosis (CF) by stabilizing the CFTR protein on respiratory epithelial surfaces. To determine the efficacy of CFTR modulators on sinonasal outcomes in patients with CF, we performed a meta-analysis of clinical trials to date that include functional and radiographic evidence of sinus disease. English full-text articles were searched in PubMed, Embase, and Scopus databases. Two reviewers screened articles and a third reviewer resolved disagreements. Articles were included if they reported functional or radiological sinonasal outcomes in patients with CF before and after CFTR modulator therapies. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed, and the risk of bias in non-randomized studies of interventions tool was used for quality assessment. The generic inverse variance method with random effects model was used for meta-analysis. Standardized mean difference (SMD) and mean difference (MD) were used as effect measurements. Seven prospective and two retrospective studies representing 248 patients were included in this analysis. There was a significant improvement in sinonasal outcome test-22 scores on elexacaftor‒tezacaftor‒ivacaftor (MD=12.80, [95% confidence interval, CI: 10.46‒15.13], p<0.001, n=222), with no heterogeneity detected (I2=0%, p=0.820). There was also a significant improvement in Lund‒Mackay scores (SMD=1.25, [95% CI: 0.58‒1.91], p<0.001, n=88), with heterogeneity detected (I2=67%, p=0.030). CFTR modulators improve functional and radiologic sinonasal outcomes. Given the utility of CFTR modulators, the treatment paradigm for CF-related chronic rhinosinusitis promises to evolve.