The respiratory tract (i.e., airways and alveoli) is in close contact with the milieu that is outside the human body and thus, in addition to its role in exchange of gases, it is needed to protect the human being from outside threats such as microbes and pollution. Respiratory tract diseases can have major detrimental effects on human health with increased risks for morbidity and mortality. An example of this dilemma is the orphan disease, primary ciliary dyskinesia (PCD), a complex genetic disorder linked with myriad genetic mutations involving over 50 genes and over 2000 pathogenic variants that lead to dysfunction of vital human components including the respiratory tract, auditory system, mechanisms of fertility and others. The core defect involves abnormal function and motion of microscopic organelles called cilia found throughout the human body with abnormal mucociliary clearance (i.e., aberrant mucociliary escalator). The regulation of motile cilia that are involved in various aspects of physiology such as respiration and reproduction is via thousands of genes. PCD pathophysiology, genetic underpinnings, diagnosis and principles of treatment are considered in this review of primary ciliary dyskinesia in pediatric persons (i.e., newborns, children and adolescents). Primary ciliary dyskinesia (PCD) is one of many ciliopathies that is identified as a condition with remarkable phenotypic and genetic variability. In this fluid fluctuation phenomenon, some PCD patients exhibit classic features such as chronic respiratory disease, situs abnormalities, and infertility, while others may present with milder or atypical disease. In certain cases, ultrastructural analysis of cilia may appear normal despite underlying dysfunction. Disease severity can range from early-onset bronchiectasis to relatively preserved pulmonary function into adulthood, reflecting perplexing genotype-phenotype diversity. Testing for PCD requires an experienced team with expertise in sophisticated technology that includes nasal nitric oxide (nNO) analysis, transmission electron microscopy (TEM), immunofluorescence analysis (IFA), high-speed video-microscopy analysis (HSVMA), three-dimensional explant spheroid formation (3D-E; ex vivo technique), genetic studies and others. Genetic testing is recommended for those suspected of having PCD, as for example in certain neonates (i.e., persistent respiratory distress, unexplained rhinorrhea with chronic cough, situs inversus), at-risk children (i.e., having persistent wet cough, chronic sinusitis, unexplained bronchiectasis, recurrent otitis media with airway symptomatology) and adults with early childhood respiratory symptoms often associated with infertility. The medical evaluation is complicated by various factors including the absence of a gold standard for a precise diagnosis. Also, as the clinician or clinical team considers a patient with possible PCD, the testing that is done should keep in mind the differential diagnoses of PCD; these conditions include cystic fibrosis (CF), various immune disorders, numerous infections (i.e., tuberculosis, aspergillosis, others), alpha-1-antitrypsin deficiency (AATD) and others as noted in this article. As emerging cutting-edge 21st century research seeks treatment of PCD via gene therapy, current management involves intense therapy of upper and lower respiratory tract infections (i.e., rhinosinusitis, otitis media, pneumonia) as well as bronchiectasis with focused efforts at dealing with impaired mucus clearance. Primary ciliary dyskinesia is a classic example of how microscopic (electron microscopic) maladies can lead to major macroscopic maladies in newborns, children, adolescents and adults.

Poor gut health, characterized by persistent immune activation and increased intestinal permeability, is considered a significant underlying cause of impaired child growth. This study aimed to investigate effects of environmental enteric dysfunction (EED) and systemic inflammation on plasma insulin-like growth factor (IGF)-1 and linear growth among Indonesian infants. In this longitudinal cohort study (Action Against Stunting Hub), faecal and plasma samples were collected at six months of age, and anthropometry assessment was conducted at six and twelve months of age. EED markers included faecal myeloperoxidase, alpha-1 antitrypsin and plasma intestinal fatty acid binding protein (IFABP). Systemic inflammation markers included C-reactive protein, alpha-1 acid glycoprotein and cluster of differentiation-14 (CD14). IGF-1 was measured as a growth biomarker. Correlation and multivariable regression analyses assessed association with length-for-age z-score (LAZ). Structural equation modelling explored potential pathways. Elevated EED markers were common among the infants (>80%). Maternal height, birth weight and IGF-1 were significant determinants of LAZ at 12 months. Pathway analysis showed IGF-1 was negatively associated with CD14, whereas CD14 was positively associated with IFABP. EED influences linear growth indirectly through systemic inflammation and altered growth signalling. Studies to further address gut integrity and systemic inflammation to improve linear growth are recommended. This article is part of the theme issue 'Biological, biomedical and environmental drivers of stunting'.

Human neutrophil elastase (HNE) is a key driver of inflammatory lung disorders, promoting extracellular matrix degradation and tissue damage. Although inhibitors such as Sivelestat and Alvelestat are clinically relevant, their performance within the oxidative microenvironment of diseased lungs remains poorly understood. Here, we employed an integrated in vitro and in silico approach to investigate their behavior under physiological and oxidative conditions and to provide a molecular-level interpretation. Under physiological conditions, enzymatic assays and steady-state kinetics confirmed that both compounds act as competitive inhibitors, with Sivelestat displaying higher baseline potency. Under oxidative stress, however, Sivelestat exhibited a marked reduction in inhibitory potency, whereas Alvelestat retained its efficacy. Molecular modeling and molecular dynamics simulations of native and oxidized HNE variants provided a structural rationale for this divergence. Alvelestat, as a non-covalent inhibitor, maintains stable binding despite increased flexibility of the active site, whereas Sivelestat, acting via a reversible covalent mechanism, requires a precise pre-acylation geometry. Oxidation-induced remodeling of the S1 pocket disrupts the near-attack configuration required for covalent bond formation, thereby impairing inhibition. Overall, these findings indicate that oxidative stress may selectively compromise covalent inhibition while preserving enzymatic activity, and suggest that context-dependent redox-related structural effects may represent a consideration for the design of next-generation HNE inhibitors.

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder characterized by reduced circulating levels and/or impaired function of alpha-1 antitrypsin (AAT), a key serine protease inhibitor, in which loss of effective antiprotease protection results in unchecked neutrophil elastase activity and progressive lung tissue destruction. Although AATD accounts for approximately 1% of chronic obstructive pulmonary disease (COPD) cases and up to 2% of emphysema, AATD-related COPD remains largely underdiagnosed, despite guideline recommendations for systematic evaluation in patients with COPD, particularly in high-risk clinical settings. Pathologically, AATD-related COPD is not limited to the typical early-onset, lower-lobe-predominant emphysema, also including upper-lobe or mixed emphysema patterns, airway-predominant disease, small airways dysfunction, and bronchiectasis. Clinically, AATD-related COPD is distinguished from smoking-related COPD by its earlier onset, physiological impairment that is often disproportionate to smoking exposure, and its potential presence of certain extrapulmonary manifestations. Diagnosis and monitoring are also challenged by the frequent discordance between airflow limitation and gas transfer impairment, as well as the early involvement of small airways, limiting reliance on spirometry alone. A multimodal assessment incorporating more sensitive functional techniques and CT densitometry may provide a more precise evaluation of disease burden, progression, and prognosis. Management generally follows standard COPD principles, with intravenous AAT augmentation therapy remaining currently the only established disease-modifying therapy for selected patients with severe deficiency. The advent of new pharmacological and gene-based therapies emphasizes the importance of developing personalized management strategies that integrate genotype and longitudinal disease behavior. This narrative review summarizes current evidence on AATD-associated COPD, focusing on its genetic basis and pathophysiological features, clinical and functional heterogeneity, current and emerging diagnostic and monitoring approaches, and disease-specific management considerations.

Alpha-1 antitrypsin deficiency (AATD) is an inherited disorder characterized by intracellular retention of mutant Z (Pi*Z) alpha-1 antitrypsin (AAT) within hepatocytes, resulting in progressive liver disease. Currently, no approved pharmacological therapies exist for AATD-associated hepatic injury. Emerging preclinical evidence indicates that inhibition of mammalian target of rapamycin (mTOR) ameliorates liver pathology in AATD; however, the status of mTOR activity and its regulatory mechanisms under Pi*Z AAT-induced cellular stress remains incompletely understood. In this study, we investigated alterations in mTOR signaling and its upstream regulatory pathways using a gene-edited human hepatocyte model harboring the Pi*Z mutation (Huh7.5Z cells) and a Pi*Z AAT transgenic mouse model. Attenuation of mTORC1 activity was observed in both cellular and murine Pi*Z models. In vitro analyses demonstrated activation of AMP-activated protein kinase (AMPKα), a key inhibitory regulator of mTORC1, accompanied by paradoxical activation of Akt and the unfolded protein response (UPR) branch ATF6α. Pharmacological inhibition of mTOR significantly reduced intracellular Pi*Z AAT accumulation, alleviated ER stress, and suppressed apoptotic signaling through enhancement of autophagy. These findings reveal that hepatocytes adapt to Pi*Z AAT-induced stress through coordinated regulation of mTOR by AMPK, Akt, and ATF6α pathways. This study provides mechanistic insight into metabolic and stress-response signaling in AATD and identifies mTOR modulation as a promising therapeutic strategy for AATD-associated liver disease.

Impaired wound healing is a major cause of morbidity among patients with diabetes. Human α1-antitrypsin (hAAT) promotes the resolution of injured tissues. In hyperglycemic conditions, circulating hAAT is likely to undergo glycation, yet it is unknown whether its reparative properties are preserved. We hypothesized that clinical-grade hAAT treatment, but not deliberately glycated hAAT (gly-hAAT), would promote wound repair under hyperglycemic conditions. Mice were rendered hyperglycemic, excisional wounding was performed, and wounds were treated with topical albumin or hAAT every three days. The wound area was assessed, and samples were collected for histology and gene expression analysis. Gly-hAAT was generated from clinical-grade hAAT, after which in vitro RAW 264.7 macrophage responses and re-epithelialization of A549 cells were assessed. Gap closure was further assessed using sera from a human cohort (prospective samples from 10 patients with poorly controlled diabetes at Soroka University Medical Center, Beer-Sheva, Israel, 2018). Group comparisons were performed using one-way ANOVA with Tukey's post hoc test. hAAT accelerated in vivo wound closure and in vitro A549 cell gap closure, accompanied by an anti-inflammatory IL-1Ra/IL-1β gene expression profile. In contrast, gly-hAAT inhibited normoglycemic mouse wound closure, evoked an inflammatory response in macrophages, and interfered with A549 cell gap closure; concomitant hAAT treatment improved gap closure. Similarly, patient serum inhibited A549 gap closure, and concomitant hAAT treatment improved gap closure. Importantly, inferential statistical analysis was not performed on this outcome due to the small and heterogeneous human cohort. In conclusion, hAAT accelerated wound closure in hyperglycemic mice and in A549 cells, whereas gly-hAAT promoted inflammatory responses and impaired wound closure, a trend reversed by native hAAT. These findings support the concept that glycation undermines the beneficial functions of circulating hAAT and provides a mechanistic insight into the pathophysiology of diabetic wound healing. Further studies are warranted to evaluate clinical-grade hAAT as a potential therapeutic for hyperglycemia-associated impaired wound healing.

Ferroptosis is a critical contributor to various cardiomyopathies; however, broad-spectrum endogenous inhibitors remain largely undefined. Although human alpha-1-antitrypsin (hAAT) exhibits cytoprotective properties, its involvement in cardiac ferroptosis remains unexplored. To directly assess endogenous hAAT function in vivo, we generated CRISPR/Cas9-mediated humanized knock-in mouse models expressing either functional (SERPINA1WT) or loss-of-function (SERPINA1Q129⁎) hAAT, and subjected them to doxorubicin-induced cardiomyopathy and myocardial infarction. SERPINA1WT mice exhibited robust protection against cardiac dysfunction, fibrosis, and remodeling, whereas SERPINA1Q129⁎ mice conferred no benefit, establishing that protection is strictly dependent on functional protein integrity. This protective effect was mediated through potent suppression of ferroptosis, as evidenced by reduced lipid peroxidation and iron accumulation. Mechanistically, endogenous hAAT activated the Nrf2 signaling pathway, upregulating key anti-ferroptotic effectors including GPX4, HO-1, and xCT; this protection was abolished by the Nrf2 inhibitor ML385. Our findings identify functional hAAT as a novel, broad-spectrum ferroptosis inhibitor operating through the Nrf2/GPX4 axis, highlighting its potential as a therapeutic target for diverse ferroptosis-driven cardiomyopathies.

Human induced pluripotent stem cells (hiPSCs) possess broad differentiation potential; however, efficient maturation into functional hepatocytes remains challenging, in part because conventional differentiation strategies rely on 2D culture or partially defined 3D systems that fail to recapitulate key developmental microenvironmental cues. Although 3D culture has been shown to promote hepatic specification and maturation, a fully defined platform that supports the entire differentiation process from hiPSCs in 3D has not been established. Here, we report a scalable synthetic peptide hydrogel (PepGel) platform that enables hiPSCs to self-organize into long-term, proliferative luminal cavity (LC) architectures within 3D colonies (LC-hiPSCs). These LC-hiPSCs exhibited markedly enhanced differentiation efficiency compared to hiPSC aggregates generated via scaffold-free suspension methods. Using a shear-thinning, self-healing hydrogel configuration optimized for suspension culture, we produced large quantities of LC-hiPSCs and directed their differentiation into PepGel-derived hiPSC-derived hepatocyte-like cells (PG-hiHs). PG-hiHs formed polarized, multi-luminal organoid-like structures and exhibited robust expression of hepatocyte-specific genes and proteins, high cytochrome P450 activity, and in vitro metabolic functions comparable to primary human hepatocytes (PHHs). Following live shipment and transplantation into immunocompromised mouse livers, PG-hiHs engrafted efficiently and maintained human-specific albumin and alpha-1 antitrypsin secretion at PHH-equivalent levels. Furthermore, both LC-hiPSCs and PG-hiHs retained viability, structural organization, and phenotype in complex 3D bioprinted constructs for at least 14 days. Together, this work establishes a fully defined, reproducible, and scalable 3D platform that supports the entire differentiation process, overcoming limitations in hiPSC-derived hepatic maturation and enables physiologically relevant hepatocyte-like tissues for disease modeling, regenerative medicine, and biofabrication.

Individuals homozygous for the SERPINA1 "Z" mutation with alpha-1 antitrypsin deficiency (AATD) are highly susceptible to emphysema. This predisposition has classically been attributed to a relative deficiency of circulating alpha-1 antitrypsin (AAT) reaching the lungs and associated protease-antiprotease imbalance. Accumulating evidence suggests that the presence of misfolded Z-AAT protein either in the circulation, the lung interstitium, or within resident lung cells could contribute to emphysema pathogenesis. We have shown that type 2 alveolar epithelial cells (AT2s), progenitor cells of the lung alveolus, heterogeneously retain Z-AAT and exhibit a transcriptional disease signature in AATD patient samples. However, a lack of model systems that faithfully recapitulate AT2 biology and associated Z-AAT expression has limited our ability to study this phenomenon. Here, we apply syngeneic induced pluripotent stem cell-derived AT2s (iAT2s) and a novel mouse model featuring AT2-specific inducible human SERPINA1 expression to interrogate the cell-instrinsic consequences of Z-AAT expression, validating findings in an independent dataset of human COPD lung tissue comparing ZZ to MM SERPINA1 genotypes. We find further evidence of Z-AAT retention within AT2s and identify shared AT2 transcriptomic disease signatures conserved across model systems, characterized by innate immune and inflammatory signaling, NF-κB activation, and endoplasmic reticulum stress. Mice with AT2-specific Z-AAT expression additionally demonstrate increased susceptibility to elastase-induced emphysema, providing functional evidence for AT2-intrinsic contributions to AATD-associated lung disease. Within iAT2s, a subpopulation of Z-AAT expressing cells exhibits activation of the PERK-eIF2α signaling axis and markers of an alveolar basal intermediate (ABI) state, emerging cell-autonomously in the absence of mesenchymal co-culture. Together, these data provide evidence that Z-AAT expression in AT2s induces heterogenous cell-intrinsic stress responses including proteotoxic stress, inflammatory signaling, and aberrant cell fate adoption, and is sufficient to result in predisposition to injury, supporting a potential contribution of AT2-intrinsic Z-AAT toxicity to human AATD-associated emphysema pathogenesis.

The use of percutaneous microwave ablation has been established as a treatment for early-stage hepatocellular carcinoma (HCC). HCC can often arise in the setting of cirrhosis and often requires locoregional therapy to ablate the area as a bridge for the ultimate treatment of liver transplantation. The challenge is its use in patients with decompensated cirrhosis and hypercoagulable states, as these high-risk populations can lead to other major complications, requiring anticoagulation, which remains challenging. In this case report, a 60-year-old woman with a history of alpha-1 antitrypsin deficiency-related cirrhosis presented with Child-Pugh class B (score 9) liver disease, thrombocytopenia, portal hypertension with esophageal varices, and factor V Leiden mutation. She underwent successful image-guided microwave ablation of a segment 7/8 Liver Imaging Reporting and Data System (LI-RADS) 5 HCC lesion as a bridge to liver transplantation, performed by interventional radiology. In this ablation, she had significant procedural risk factors, but with multidisciplinary planning, there was only a minor non-distressing hematoma noted, and overall allowed effective tumor treatment without major complications. This case highlights the practicality of microwave ablation in high-risk patients and emphasizes the critical role of interventional radiology in expanding therapeutic options for transplant candidates with limited alternatives.