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Background: Hypoplastic left heart syndrome (HLHS) is defined as “a spectrum of congenital cardiovascular malformations with normally aligned great arteries without a common atrioventricular junction, characterized by underdevelopment of the left heart with significant hypoplasia of the left ventricle including atresia, stenosis, or hypoplasia of the aortic or mitral valve, or both valves, and hypoplasia of the ascending aorta and aortic arch”. Without treatment, HLHS is usually lethal in the neonate. Many hypotheses have been advanced to explain the etiology of HLHS; however, no single theory appears to fully explain the phenotypic variability seen in HLHS. Furthermore, many of these theories offer no explanations regarding the precipitating events which lead to the development of HLHS. Objective: This review considers and critically evaluates the strengths and weaknesses of the leading theories proposed to explain the pathogenesis of HLHS—including hemodynamic disturbances, primary myocardial structural defects, valvar malformations, and genetic or epigenetic alterations that may provoke developmental and anatomic abnormalities. After presenting each model, we propose a novel, comprehensive, and data-driven framework which may assist researchers in developing models for the pathogenesis of the various subtypes of HLHS. Methods: Key findings from human fetal imaging, histopathology, genetic studies, and animal models were considered, as well as the hypothetical contribution of each in observed HLHS phenotypes. The rationales for these findings as causal factors initiating individual HLHS patterns, as well as how they might contribute to HLHS in general, were critically analyzed. Results: The flow theory is strongly supported by animal models and in utero interventions that demonstrate the impact of altered hemodynamics on cardiac morphogenesis. However, the flow theory fails to identify initial causes of disturbed flow or related histological features of HLHS like endocardial fibroelastosis. The myocardial and valve-first models suggest an important role in developmental defects, but do not necessarily have a strong experimental basis that provides explanations for how they mediate HLHS. Genetic studies in patients with HLHS have identified several candidate causal mutations. However, such genetic causes of HLHS exhibit incomplete phenotypic penetrance and clinical impact. A multifactorial framework attempts to integrate these diverse mechanisms and may provide the most coherent explanation that can accommodate the heterogeneity and variable presentation of HLHS. Such a framework may identify multiple forces that drive disease but does not provide useful pathways for future research about HLHS. Conclusions: No single hypothesis has fully explained how HLHS is initiated, progresses, and presents with the clinical conditions that are encountered by cardiac surgeons and cardiologists. The most current models suggest that the spectrum of HLHS reflects acomplex interaction between genetic susceptibility, flow-dependent cardiac remodeling, and environmental factors in utero. A multifactorial model integrates these diverse mechanisms and may provide the most coherent explanation for the various phenotypic variations in HLHS. Based on our analysis of the most current data and the strengths and weaknesses of the current theoretical frameworks, we propose a novel research strategy aimed at identifying specific cardiac progenitor cell populations whose dysregulation may represent a unifying explanation for the etiology of the various phenotypes of HLHS. Based on the arguments made throughout this manuscript that evaluate the various genetic, structural, and hemodynamic models of initiation of disease, we believe that the significant phenotypic variability across the spectrum of HLHS (i.e., the different anatomic subtypes for “classic” HLHS) most likely reflects different underlying etiologies and mechanisms. At the very least, it is very likely that the timing of the insult is critical in determining anatomic subtype. Based on the published data and the arguments within this manuscript, it seems naive to think that there is a single unifying mechanism explain all forms of HLHLS.

Summary Achalasia is a motility condition defined by failure of relaxation of the lower esophageal sphincter and loss of peristalsis in the distal esophagus. Per-oral endoscopic myotomy (POEM) is a technique to reduce lower esophageal sphincter pressure. We performed a systematic review and meta-analysis to assess the association between POEM and the clinical outcomes. We performed a systematic review and a meta-analysis (CRD420251052240). Literature search was done on PubMed and Embase (up to 8 June 2025). Original studies involving achalasia patients who underwent esophageal POEM with impedance planimetry using 8-cm balloon at 30 or 40 mL filling volumes with 325 catheter only (not the 322-N catheter) were included. The outcomes of interest were the clinical response groups (responders’ Eckardt score [ES] < 3 and non-responders’ ES > 3), reflux esophagitis, cross-sectional area (CSA), distensibility index (DI), and diameter. Nineteen studies with 1215 patients were included. The responders (ES < 3) showed a statistically significantly greater increase in DI due to POEM (post-op minus pre-op) (mean difference [MD] = 1.92 mm2/mmHg [0.32, 3.53], P = 0.02) as well as a higher postoperative DI (MD = 1.87 mm2/mmHg [0.04, 3.70], P = 0.05) (40 mL). Reflux esophagitis group had statistically significantly higher CSA and diameter values (CSA MD = 15.68 mm2 [6.91, 24.24], P = 0.0005) (diameter MD = 0.96 mm [0.58, 1.33], P < 0.00001) but no statistically significant difference for DI as compared to the non-reflux esophagitis group (DI MD = 0.19 mm2/mmHg [−0.51, 0.89], P = 0.59). In achalasia patients undergoing esophageal POEM, a greater interval increase in the DI as well as a higher post-procedural DI absolute value predicts a favorable clinical response. Higher postoperative CSA and diameter were linked to reflux esophagitis.

Abstract Rationale Acute cellular rejection (ACR) within first-year post-lung transplantation has important implications for prognosis. Calcineurin inhibitors (CNI), including tacrolimus or cyclosporine, along with cell cycle inhibitors (CCI) and steroids, remain the standard immunosuppression regimen post-transplant. Although tacrolimus is used as the primary CNI, target therapeutic levels vary across recipients due to adverse effects and tolerability, sometimes requiring switching over to Cyclosporine. We hypothesized that ACR within the first year is associated with switching CNI from Tacrolimus to Cyclosporine. Methods We performed a cross-sectional study of 255 adult lung transplant recipients between June 2019 to November 2024 at Mayo Clinic, Florida. Demographics, induction regimens, CNI type and their levels (average low and high levels) were compared between the 2 groups. The institutional maintenance immunosuppression regimen is Tacrolimus, Mycophenolate Mofetil (MMF) and prednisone, but could be switched to Cyclosporine if the previous regimen is not tolerated. The primary outcome was ACR <1 year diagnosed based on biopsy and/or clinical criteria. Comparisons between groups were performed using Chi-Square test for categorical variables and t-test or Wilcoxon Rank sum test for continuous variables. Multivariable regression analysis was performed with ACR <1 year as the outcome to adjust for the confounders. Results Our cohort included 255 lung transplant recipients with median age of 63 years, 61% Male, 84% Caucasians, 88% bilateral lung transplant (Further details elucidated in Table 1). A total of 173 (67%) out of 255 patients had ACR <1 year. The group with ACR < 1 year had higher proportion of Interstitial Lung Disease (ILD) (81% vs 68%, p = 0.044), use of Basiliximab for induction (70% vs 55%, p = 0.018), and cyclosporine instead of tacrolimus (23% vs 11%, p = 0.027). Group with ACR <1 year also had higher Antibody Mediated Rejection (AMR) < 1year (15% vs 6.1%, p = 0.041) and higher CLAD (BOS 0p-3: 43% vs 25.6%, p = 0.033) compared to the group without ACR < 1 year (Table 1.1). Multivariate regression analysis showed ILD (adjusted odds ratio, aOR 2.84, 95% CI 1.31 - 6.27, p = 0.008) and use of cyclosporine (aOR 2.55, 95% CI 1.07 - 6.78, p = 0.034) as independent predictors of ACR < 1 year (Table 2). Conclusions The presence of ACR < 1 year was associated with the use of Cyclosporine over Tacrolimus as a maintenance regimen. Also, ACR < 1year was associated with higher AMR and CLAD. Further prospective studies are needed to study this long-term given its significant prognostic implications. This abstract is funded by: Not Applicable

Abstract Inflammatory bowel diseases (IBD), principally Crohn’s disease (CD) and ulcerative colitis (UC), are common chronic disorders involving inflammation and often progressive tissue damage. Genome-wide association studies have mapped many risk signals, but the causal variants, effector genes and relevant cellular contexts remain difficult to resolve, limiting mechanistic interpretation and therapeutic translation. Here we performed a multi-ancestry GWAS meta-analysis of 125,992 individuals with IBD and more than 1.2 million controls, identifying 619 independent association signals (374 novel) at 420 IBD regions that account for 77–80% of SNP-based heritability. Fine-mapping resolved 81 high-confidence variants, 41 not previously reported. Although most signals were shared between CD and UC, 39% showed IBD subtype specificity, with UC signals showing stronger enrichment in functional annotations from intestinal epithelial, secretory and enteroendocrine cells, and CD showing stronger genetic correlations with circulating inflammatory biomarkers, including C-reactive protein and glycoprotein acetylation. Latent causal modelling supported a causal effect of decreased high-density lipoprotein on CD risk. By integrating bulk and single-cell eQTL and pQTL resources using colocalisation and Mendelian randomisation, together with coding-variant evidence from exome sequencing, we prioritised 664 candidate effector genes across 341 signals, including 390 newly implicated IBD genes, revealing new biological mechanisms and candidate therapeutic targets supported by human genetics.

Abstract Rationale Pulmonary hypertension (PH) develops in up to 50% of patients with advanced interstitial lung disease (ILD) and is associated with increased morbidity, mortality, and impaired quality of life. Early recognition is essential, as available therapy for ILD-PH has been shown to improve outcomes. Identifying physiologic markers of PH may facilitate earlier referral for right heart catheterization (RHC) and initiation of targeted treatment. Thus, this study aimed to (1) compare functional parameters between ILD patients with and without RHC-confirmed PH, and (2) assess the applicability of previously proposed ILD-PH screening criteria. Methods We retrospectively analyzed ILD transplant candidates with available pre-transplant pulmonary function tests (FVC%, DLCO%), echocardiographic right-ventricular systolic pressure (RVSP), six-minute walk distance (6MWD) with oxygen requirement, and RHC data. PH was defined according to the 2022 ESC/ERS criteria. Functional parameters were compared between patients with and without PH. Among those without a prior PH diagnosis, screening thresholds derived from previously published tools were applied (RVSP ≥ 35 mmHg, DLCO < 40%, FVC/DLCO > 1.6, 6MWD < 350 m, or oxygen use during 6MWD). Results Of 107 ILD patients evaluated, 90 had complete RHC data (48 ILD-PH, 42 ILD without PH). Group comparisons are summarized in Table 1. Patients with PH had lower DLCO% (median 18.5 [11.5-26.7] vs 26.5 [20.0-34.7], p = 0.08), higher FVC/DLCO ratios (2.68 [2.1-3.4] vs 1.7 [1.4-2.6], p = 0.08), and higher RVSP (55 [39.7-63.2] vs 39.5 [29-48] mmHg, p = 0.002). Oxygen requirement during 6MWD was more frequent in ILD-PH (79.2% vs 61.9%, p = 0.08). Among patients with PH, 38 (79.16%) had no formal diagnosis prior to pre-transplant RHC. Of these cases, all (100%) met ≥3 screening criteria, most commonly DLCO < 40% (n = 38, 100%), FVC/DLCO > 1.6 (n = 37, 97.3%), and 6MWD < 350 m (n = 33, 86.8%). Additionally, 32 patients (84.21%) met ≥4 criteria and 8 (21.05%) met all five criteria. Conclusion In ILD transplant candidates, patients with PH had worse functional profiles when compared to those without PH, and nearly 80% of PH cases were previously undiagnosed. Systematic application of validated PH screening tools in ILD populations may facilitate earlier recognition, potentially improving patient outcomes. This abstract is funded by: None

Abstract Introduction Pulmonary arterial hypertension (PAH) is a progressive and deadly disease characterized by pulmonary vascular remodeling and eventual right heart failure. A mainstay of treatment for PAH is prostacyclin therapy which can be delivered via continuous subcutaneous (SQ) or intravenous (IV) infusion. Infusion site reactions are a common occurrence with SQ Treprostinil resulting in discontinuation in approximately 10% of patients. Given that switching from SQ to IV prostacyclin therapy contains risks associated with long-term central venous access such as blood stream infections and deep venous thrombosis, the development of better strategies to improve SQ Treprostinil tolerability are needed. Case Report We report two patients with PAH who developed delayed infusion site reactions to SQ Treprostinil. Both patients were female, in their 30s, with severe group 1 PAH (mean pulmonary artery pressures of 44 and 81 mmHg on right heat catheterization at diagnosis), who had been on SQ Treprostinil for approximately 6 years on a dose around 60 ng/kg/min. Within two weeks of starting a new SQ infusion site, each patient developed a raised, hyperemic site reaction in the area of the infusion catheter draining yellow fluid (Figure 1). Skin patch testing was done from an ampule of preservative-free Treprostinil demonstrating a type 1 hypersensitivity reaction. There was no skin reaction to the Tegaderm dressing alone. Dupilumab 300 mg weekly SQ injections were started for these type 1 hypersensitivity reactions with resolution of the site reactions and pain. Because of this, both patients were able to remain on their SQ Treprostinil infusions. Discussion Infusion site reactions to SQ Treprostinil are common and can necessitate discontinuation of the medication. SQ Treprostinil infusion site reactions typically occur within 48 hours of establishing a new SQ infusion site and are thought to be a local vasodilatory reaction to the Treprostinil itself. These reactions can be minimized by analgesic pain medication and by increasing the Treprostinil infusion concentration. Here we describe two infusion site reactions that occurred two weeks after establishing a new site and were consistent with a type 1 hypersensitivity reaction. These reactions were successfully treated with Dupilumab which allowed the patients to remain on SQ Treprostinil. This abstract is funded by: None

Abstract Background Prostaglandin E2 (PGE2) exerts paradoxical effects in asthma, acting as both a protective mediator and a contributor to pathology depending on context. Its role is shaped by type 2 (T2)-status, eosinophilia, and exacerbation frequency. In epithelial cell cultures from asthmatic and healthy individuals, interleukin (IL)-13 suppresses PGE2 synthesis genes (PTGS2 and PGES) while upregulating HPGD, which encodes for the PGE2 catabolic enzyme 15-prostaglandin dehydrogenase (15-PGDH) (PMID:16751012), suggesting diminished PGE2 availability during T2 inflammation. Similarly, in aspirin-exacerbated respiratory disease (AERD), impaired cyclooxygenase disrupts PGE2 biosynthesis, fueling unchecked leukotriene production and eosinophilic inflammation (PMID: 30516547), underscoring PGE2’s protective role in limiting disease progression. Conversely, in nasal polyps, tuft cells are activated by IL-13 to produce PGE2 (PMID: 35608904), highlighting PGE2’s potential pathogenicity. Objective To assess associations between PGE2-pathway gene expression in bronchial brushings and asthma severity, and to determine how nasal polyp history modifies these relationships. Methods We analyzed bronchial epithelial brushings from 109 adults with asthma (mean age 42.4±12.1, 64% female, 52% severe asthma, 18% nasal polyps) using normalized and batch-corrected RNA-seq data from the baseline visit in the Severe Asthma Research Program (SARP)3 (PMID: 36796454). Age-adjusted and nasal polyp-adjusted relationships were calculated between ratios of PGE2 synthesis and metabolism genes and clinical outcomes (ASSESS score, FEV1 %predicted). The composite PGE2 score (PMID: 35608904), derived from nasal polyp analysis, was calculated from the average scaled log-normalized expression of six PGE2-responsive genes. All data were analyzed using a linear regression mixed model with a random effect for site. Results Ratios of PGE2 synthesis genes (PTGS1/2, PTGES2) to HPGD were significantly associated with greater disease severity (change in ASSESS Score) (Fig.1A, solid lines) and lower lung function (change in FEV1 %predicted) (Fig.1B, solid lines). These relationships persisted after adjusting for nasal polyps (Fig.1, dashed lines). The composite PGE2 score was also related to disease severity (Fig.1A, black solid line) but attenuated when nasal polyps were accounted for (Fig.1A, black dashed lines). Interestingly, lower lung function remained associated with the PGE2 score even after nasal polyp adjustment (Fig.1B, dashed black lines). Conclusions Our analysis demonstrates that the balance between PGE2 synthesis and degradation in the bronchial epithelium is closely linked to asthma severity and lung function, independent of nasal polyp status. Future work will integrate transcriptomic and clinical data longitudinally to establish whether PGE2 could serve as a biomarker for asthma trajectory. This abstract is funded by: HL115118 (LCD), U10HL109152 (S.E.W.), U10HL109172 (to E.I. and B.D.L), U10HL109168 (N.N.J.), U10HL109250 (S.C.E), U10HL109164 (W.C.M), U10HL109257 (M.C), and U10HL109146 (to P.G.W. and S.A.C.)

Abstract Rationale The activity of fucosyltransferase 2 (FUT2) determines if mucin glycan structures in epithelial mucus include histo-blood group antigens (HBGAs). People with active FUT2 express HBGAs in epithelial mucus secretions and are terms “secretors”, while non-secretors lack HBGAs in their secretions because they have a FUT2 genotype that inactivates the glycosyl transferase. Prior research suggests that secretors who are blood type O (type O secretors) are susceptible to asthma exacerbations1 and that FUT2 knockout mice (functional non-secretors) are protected from mucus plugging in allergen challenge models2,3. We set out here to determine if secretor status influences mucus plug prevalence in asthma and to confirm if type O secretors are susceptible to asthma exacerbations. Methods We determined secretor status in asthma participants from the Severe Asthma Research Program-3 (SARP-3) cohort (N = 507) in two ways, a specific fucose lectin binding assay in sputum and FUT2 genotyping. Blood group type was determined using ABO genotyping. We analyzed mucus plug segment scores, asthma exacerbations rates and other clinical and biological features in patients stratified by secretor status and blood type (non-secretors, type O secretors, and non-type O secretors). Results Secretor status determined by lectin binding in sputum was strongly concordant with genotypic analysis. Within the SARP-3 cohort, 26.2% were non-secretors, 32.3% type were O secretors, and 41.4% were non-type O secretors. Mucus plug segment scores, annualized asthma exacerbation rates, and other measures of asthma severity were similar in non-secretors, type O secretors, and non-type O secretors (Table). Although type O secretors had increased values for fractional exhaled nitric oxide (FeNO) and higher expression of type 2 gene network genes in their sputum cells, measures of sputum eosinophil inflammation were not higher in this subgroup (Table). Conclusion Secretor status does not influence the prevalence of mucus plugging in asthma patients, and we did not confirm a prior report that type O secretors have an increased risk of asthma exacerbation. Although type O secretors have modestly increased FeNO levels and increased expression of type 2 immune genes in their sputum, it is not clear if this is a biologically important signal. 1. Innes et al. AJRCCM; 2011. 2. Saku et al. JACI; 2019. 3. Hara et al. AJRCMB; 2025 This abstract is funded by: The study was supported by the National Institutes of Health grants R01 HL080414 (JVF), P01 HL107202 (JVF), R01 HL164787 (JVF), U10 HL109172 (EI), U10 HL109152 (SEW), U10 HL109257 (MC), U10 HL109250 (SCE), U10 HL109146 (JVF), U10 HL109164 (ERB), U01 HL146002 (BDL), U10 HL109086 (DTM) and Sandler Asthma Basic Research Center at UCSF (JVF). The following companies provided financial support for study activities at the Coordinating and Clinical Centers beyond the third year of patient follow-up: AstraZeneca, Boehringer-Ingelheim, Genentech, GlaxoSmithKline, Sanofi–Genzyme Regeneron, and Teva. These companies had no role in study design or data analysis, and the only restriction on the funds was that they be used to support the SARP initiative.