Abstract
Fire-related smoke inhalation-induced acute lung injury (SI-ALI) is a prevalent condition in modern fires, characterized by high mortality and a lack of targeted therapeutic options. Previous research has been hindered by instability in smoke generation and modeling methods, limiting the investigation of SI-ALI mechanisms. This study, for the first time, utilized organ-on-a-chip and organoid technologies, optimizing chip design and precisely controlling smoke generation from non-metallic materials to establish a human-relevant, physiologically accurate model of fire-related SI-ALI. The results demonstrate that this model effectively simulates the alveolar-capillary barrier and replicates key pathological features of lung injury, including oxidative stress, apoptosis, immune cell adhesion, inflammatory responses, capillary leakage, and mitochondrial damage. Injury responses of endothelial and epithelial cells to smoke exposure were thoroughly assessed at the organ level. Integrating proteomics and molecular biology techniques, along with comparisons to animal models, identified disease-specific pathways related to the spliceosome and carbon metabolism, as well as pathogenic molecules such as catechol-O-methyltransferase (COMT) and nitrilase 1 (NIT1). Furthermore, molecular docking of COMT revealed potential therapeutic candidates from the FDA-approved drug library, including Ractopamine HCl and Bimatoprost. The efficacy of intravenous vitamin C combined with nebulized budesonide was validated on the chip model, establishing a foundation for clinical applications. This study provides a robust model for investigating fire-related SI-ALI and offers novel insights into underlying mechanisms and therapeutic development.
Keywords : Organ-on-a-Chip; Organoids; Acute Lung Injury; Fire Incidents; Molecular Docking; Drug Screening
Introduction
Fire-related smoke inhalation-induced acute lung injury (SI-ALI) is among the most prevalent clinical injuries. The combustion of non-metallic materials indoors during a fire releases significant amounts of toxic substances, which can cause severe damage to the respiratory tract. In extreme cases, this can progress to acute respiratory distress syndrome (ARDS) or even multiple organ dysfunction syndrome (MODS)[1]. Studies have shown that burn patients with concurrent inhalation lung injury have a 40% higher mortality rate[2].
Unlike other forms of SI-ALI, such as those induced by cigarette smoke, wood burning, or exposure to single toxic gases[3, 4], fire-related SI-ALI is considerably more complex, especially in the modern era, due to the new composite materials used in modern wood manufacturing. Traditional wood, once the primary material for indoor furnishings, has largely been replaced by synthetic rubbers, resins, and other high-molecular-weight non-metallic materials. The combustion of these mixed materials during a fire releases large quantities of toxic gases, including hydrogen cyanide (HCN), carbon monoxide (CO), and benzene[5]. These toxic gases, along with hazardous particulates, enter the respiratory system, triggering a cascade of pathological events such as oxidative stress, immune cell infiltration, inflammatory responses, and disruption of the alveolar-vascular barrier[6]. Unfortunately, no targeted therapies are currently available for fire-related SI-ALI, with treatment primarily relying on mechanical ventilation and supportive care. An appropriate model is essential for investigating the mechanisms of fire-related SI-ALI and developing effective therapeutics.
However, current models of fire-related SI-ALI face two significant challenges: the inhomogeneity of smoke generation and the inherent limitations of traditional animal and cell models. First, the composition and concentration of smoke can vary greatly depending on fire conditions, such as temperature and material composition[7], leading to the lack of reproducibility in these models. Moreover, traditional animal models, although commonly employed to investigate the mechanisms and replicate the pathological processes of SI-ALI[8, 9], are inherently limited due to physiological and genetic differences between animals and humans. These models are further constrained by ethical considerations, adherence to the 3R principles (Reduction, Replacement, Refinement), and the high costs and time demands associated with their use. Additionally, understanding the complex interactions between different cell types and elucidating their specific roles in SI-ALI is challenging in these models.
On the other hand, single-cell line models, frequently used in toxicity screening and mechanistic studies, also fail to accurately represent the complexity of SI-ALI[10, 11]. The lung comprises a diverse array of cell types—including epithelial, vascular, stromal and immune cells—that interact in complex pathophysiological processes. Furthermore, exposing lung epithelial cells to smoke extract in liquid form does not adequately simulate actual smoke exposure, as certain hydrophobic components of smoke are insoluble. Therefore, there is an urgent need to develop a stable, reproducible, human-derived model that is versatile and physiologically relevant, capable of faithfully replicating the pathological processes of fire-related SI-ALI.
Organ-on-a-chip technology offers a promising solution to the limitations inherent in traditional models[12]. Microengineered breathing lung chips have been developed to simulate human airway responses to cigarette smoke, particularly within the context of chronic obstructive pulmonary disease (COPD)[13]. These lung-on-chips (LOCs) have also been employed to study the nanotoxicity of TiO₂ and ZnO nanoparticles on lung epithelial and endothelial cells, demonstrating the cytotoxicity, reactive oxygen species (ROS) production, and apoptosis induced by these nanoparticles[14]. Advanced LOCs serve as highly efficient platforms for drug screening, enabling the use of techniques such as transcriptomics, proteomics, and computational molecular biology to investigate disease pathology and facilitate drug development[15]. Additionally, lung organoids, which retain the unique cellular components and genetic characteristics of lung tissue, allow for the creation of more physiologically relevant disease models, thereby improving the accuracy of drug screening[16]. The integration of lung-on-a-chip and organoid technologies holds significant potential for simulating the pathological processes of fire-related SI-ALI, elucidating underlying mechanisms, and identifying effective treatments.
This study pioneers the integration of organ-on-a-chip and organoid technologies, enhancing the organ-on-a-chip system based on previous research. Materials were carefully blended to reflect the proportions of non-metallic components typically found in modern yachts, with precise control over the combustion process. The composition and concentration of smoke were monitored in real-time using Fourier-transform infrared spectroscopy (FTIR), effectively simulating the smoke production process during actual fires. Building on this foundation, a lung-on-a-chip model for fire-related SI-ALI was developed, successfully replicating key pathological processes in vitro and examining the responses of various cell types to smoke-induced damage. The study, combined with animal models, molecular biology techniques, proteomics, and molecular docking, explored the unique pathogenic mechanisms of fire-related SI-ALI and identified potential therapeutic drugs. Furthermore, the chip platform was utilized to evaluate the therapeutic potential of nebulized budesonide combined with intravenous vitamin C, with these findings validated in the organoid chip model. This research establishes a new paradigm for studying fire-related SI-ALI, providing valuable insights into its pathology and potential treatments.
Materials and methods