Regeneration of functional alveoli by adult human SOX9+ airway basal cell transplantation

Targeted therapy for idiopathic pulmonary fibrosis: a bibliometric analysis of 2004-2024

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible interstitial lung disease characterized by high mortality rates. An expanding body of evidence highlights the critical role of targeted therapies in the management of IPF. Nevertheless, there is a paucity of bibliometric studies that have comprehensively assessed this domain. This study seeks to examine global literature production and research trends related to targeted therapies for IPF.

Method

A literature search was conducted using the Web of Science Core Collection, encompassing publications from 2004 to 2024, focusing on targeted therapies for IPF. The bibliometric analysis utilized tools such as VOSviewer, CiteSpace, and the "bibliometrix" package in R.

Results

A total of 2,779 papers were included in the analysis, demonstrating a general trend of continuous growth in the number of publications over time. The United States contributed the highest number of publications, totaling 1,052, while France achieved the highest average citation rate at 75.74. The University of Michigan Medical School was the leading institution in terms of publication output, with 88 papers. Principal Investigator Naftali Kaminski was identified as the most prolific researcher in the field. The American Journal of Respiratory Cell and Molecular Biology emerged as the journal with the highest number of publications, featuring 98 articles. In recent years, the research has emerged surrounding targeted therapies for IPF, particularly focusing on agents such as TGF-β, pathogenesis, and autotaxin inhibitor.

Conclusion

In this bibliometric study, we systematically analyze research trends related to targeted therapies for IPF, elucidating recent research frontiers and emerging directions. The selected keywords-idiopathic pulmonary fibrosis, targeted therapy, bibliometric analysis, transforming growth factor β, and autotaxin inhibitor-capture the essential aspects of this research domain. This analysis serves as a reference point for future investigations into targeted therapies.

Airway basal stem cell-derived extracellular vesicles modulate proliferation, migration and collagen deposition of fibroblasts

BACKGROUND

Human bronchial epithelial cell-derived extracellular vesicles have demonstrated the ability to attenuate fibroblasts activation. However, the specific key effector cell populations mediating this inhibitory effect remain unidentified. Airway basal stem cells (BSCs), which serve as progenitor cells for bronchial epithelial cells, play a critical role in fibrotic remodeling processes and possess significant therapeutic potential. This study aimed to characterize BSC-derived extracellular vesicles (BSC-EVs) and investigate their regulatory influence on fibroblasts behavior.

METHODS

Airway BSCs were collected through bronchoscopic brushing and differential centrifugation. Fibroblasts were subsequently treated with BSC-EVs at various concentrations to evaluate their dose- and time-dependent effects in vitro. The proteomic composition of BSC-EVs was analyzed using four-dimensional data-independent acquisition quantitative mass spectrometry (4D-DIA). Moreover, a bleomycin-induced pulmonary fibrosis model was established to evaluate the safety and preliminary efficacy of BSC-EVs.

RESULTS

We successfully isolated and identified BSC-EVs, which expressed the nucleus-specific marker TP63, indicative of BSCs, but lacked the BSC marker KRT5. Our findings demonstrated that BSC-EVs enhanced fibroblasts proliferation and migration in a dose-dependent manner. Importantly, BSC-EVs significantly attenuated fibroblasts activation and promoted fibroblasts senescence. Utilizing 4D-DIA quantitative proteomics, we revealed that BSC-EVs modulate extracellular matrix remodeling processes and regulate the expression of key proteins, including collagen I/III and matrix metalloproteinases. Animal models utilizing intratracheal administration of BSC-EVs demonstrate efficient reduction of collagen deposition.

CONCLUSION

This study offers an extensive characterization of BSC-EVs, adhering to the guidelines set forth by MISEV2023. The findings underscore the significant therapeutic potential of BSC-EVs in the management of fibrotic diseases.

Autologous P63+ lung progenitor cell transplantation in idiopathic pulmonary fibrosis: a phase 1 clinical trial

Background

In idiopathic pulmonary fibrosis (IPF) patients, alveolar architectures are lost and gas transfer function would decline, which cannot be rescued by conventional anti-fibrotic therapy. P63+ lung basal progenitor cells are reported to have potential to repair damaged lung epithelium in animal models, which need further investigation in clinical trials.

Methods

We cloned and expanded P63+ progenitor cells from IPF patients to manufacture cell product REGEND001, which were further characterized by morphology and single-cell transcriptomic analysis. Subsequently, an open-label, dose-escalation autologous progenitor cell transplantation clinical trial was conducted. We treated 12 patients with ascending doses of cells: 0.6x, 1x, 2x and 3.3x106 cells/kg bodyweight. The primary outcome was the incidence and severity of cell therapy-related adverse events (AEs); secondary outcome included other safety and efficacy evaluations.

Results

P63+ basal progenitor cell was safe and tolerated at all doses, with no dose-limiting toxicity or cell therapy-related severe adverse events observed. Patients in three higher dose groups showed significant improvement of lung gas transfer function as well as exercise ability. Resolution of honeycomb lesion was observed in patients of higher dose groups.

Conclusions

REGEND001 has high safety profile and meanwhile encourages further efficacy exploration in IPF patients.

Funding

National High Level Hospital Clinical Research Funding (2022-PUMCH-B-108), National Key Research and Development Plan (2024YFA1108900, 2024YFA1108500), Jiangsu Province Science and Technology Special Project Funding (BE2023727), National Biopharmaceutical Technology Research Project Funding (NCTIB2023XB01011), Non-profit Central Research Institute Fund of Chinese Academy of Medical Science (2020-PT320-005), and Regend Therapeutics.

Clinical trial number

Chinese clinical trial registry: CTR20210349.

Epithelialized chimeric repairing patch supports in situ healing of tracheal fistula

Tracheal fistula (TF) is a severe thoracic disease characterized by high mortality rates, and current treatment methods present substantial risks while presenting challenges in reepithelialization. In this study, we developed a chimeric repairing patch (CRP) featuring a double-disc structure, designed to seal TF defects and promote organized tissue regeneration. The CRP incorporates a double-cross-linking silk fibroin network and hierarchical micropores, resulting in a flexible, hydrophilic, and biocompatible patch with tissue-matching mechanical properties. The CRP could effectively seal defects and encourage tissue ingrowth, successfully repairing TF. A tissue-engineered epithelialized CRP (E-CRP) was further developed to enhance in situ reepithelialization. The CRP demonstrated reliable structural stability and facilitated effective tissue regeneration and functional reconstruction of TF defects in a large animal model. Furthermore, the customized CRPs might be preloaded into a bronchoscope and precisely delivered to TF defects via noninvasive implantation. Consequently, the proposed CRP/E-CRP represents a promising scaffold for TF treatment, with substantial transformative potential in clinical practice.

Advancements in lung regeneration: from bench to bedside

Lung disorders rank among the leading causes of mortality worldwide, presenting a critical challenge in healthcare. The underlying limited regenerative capacity of the lung makes this an unmet clinical need, often necessitating lung transplantation for patients with severe lung disease. However, the lack of viable donor organs underscores the urgent need for alternative therapeutic strategies. Addressing this challenge requires a comprehensive understanding of the structure of lung tissue and the complexities inherent in its regeneration. In this review, we explore recent breakthroughs in lung regenerative medicine, highlighting innovative approaches aimed at tackling lung and tracheal diseases. From stem cell and cell-based therapies to the utilization of biological and synthetic materials, as well as the strategic deployment of growth factors, a diverse array of strategies is being explored to rejuvenate lung function. By critical analysis of in vitro, preclinical, and clinical studies, this review aims to provide a comprehensive overview of the emerging technology of lung regeneration research, shedding light on promising avenues for future therapeutic interventions.

Cloned airway basal progenitor cells to repair fibrotic lung through re-epithelialization

Irreversible damage of the lung epithelium in idiopathic pulmonary fibrosis (IPF) patients causes high mortality worldwide, with no lung repair approaches available currently. Here we show that in murine and monkey models, the KRT5+ P63+ progenitor cells in airway basal layer can enter the alveolar area post fibrotic injury. Aided with an automated culture system, we clone and characterize airway basal progenitor cells from 44 donors with various lung conditions. Transplantation of human progenitor cells into the mouse lung efficiently re-epithelializes the injured alveolar area, forms new respiratory tract and saccule-like structures, which ameliorates fibrotic lesions and improves survival of mice. Mechanistically, the engrafted human progenitor cells do not function by differentiating into mature alveolar cells in mouse lung; instead, they differentiate into saccular cells expressing multiple tight junction proteins such as CLDN4, which help the lung to re-establish epithelial barriers. Furthermore, by cloning P63+ airway basal progenitors from larger mammals and birds, we construct multiple lung-chimerism animals and uncover the evolutionarily conserved roles of these progenitor cells in lung repair. Overall, our data highlight the fate of airway basal progenitor cells in fibrotic lung and provide a potential therapeutic strategy for pulmonary diseases that lack inherent recovery mechanisms.

Airway basal stem cell therapy for lung diseases: an emerging regenerative medicine strategy

Chronic pulmonary diseases pose a prominent health threat globally owing to their intricate pathogenesis and lack of effective reversal therapies. Nowadays, lung transplantation stands out as a feasible treatment option for patients with end-stage lung disease. Unfortunately, the use of this this option is limited by donor organ shortage and severe immunological rejection reactions. Recently, airway basal stem cells (BSCs) have emerged as a novel therapeutic strategy in pulmonary regenerative medicine because of their substantial potential in repairing lung structure and function. Airway BSCs, which are strongly capable of self-renewal and multi-lineage differentiation, can effectively attenuate airway epithelial injury caused by environmental factors or genetic disorders, such as cystic fibrosis. This review comprehensively explores the efficacy and action mechanisms of airway BSCs across various lung disease models and describes potential strategies for inducing pluripotent stem cells to differentiate into pulmonary epithelial lineages on the basis of the original research findings. Additionally, the review also discusses the technical and biological challenges in translating these research findings into clinical applications and offers prospective views on future research directions, therefore broadening the landscape of pulmonary regenerative medicine.

Promoting epithelial regeneration in chemically induced acute lung injury through Sox9-positive alveolar type 2 epithelial cells

BACKGROUND

Chemical-induced acute lung injury is characterized by impaired epithelial regenerative capacity, leading to acute pulmonary edema. Numerous studies have investigated the therapeutic potential of endogenous stem cells with particular emphasis on alveolar type 2 epithelial (AEC2) cells owing to their involvement in lung cell renewal. Sox9, a transcription factor known for its role in maintaining stem cell properties and guiding cell differentiation, marks a subset of AEC2 cells believed to contribute to epithelial repair. However, the role of Sox9+AEC2 cells in the distal lung alveolar cells and the potential roles in chemically induced acute lung injury have never been explored.

METHODS

In this study, we generated Sox9flox/flox;SftpcCre-ERT2 mice and examined the effects of Sox9+AEC2 cells on the pathophysiology of epithelial damage during chemical-induced acute lung injury. Subsequently, Sox9-CreERT2 Ai9 mice were used for lineage tracing to elucidate the repair mechanisms.

RESULTS

Our findings revealed that Sox9+AEC2 cells endowed with stem cell properties induced cell proliferation during lung injury, predominantly in the damaged alveolar region. This process is accompanied by the regulation of inflammatory responses and orderly differentiation, thereby promoting epithelial regeneration.

CONCLUSION

These results provide compelling in vivo genetic evidence supporting the characterization of Sox9+AEC2 cells as bona fide lung epithelial stem cells, demonstrating their multipotency and self-renewal capabilities during lung repair and regeneration. The identification of Sox9+AEC2 cells as crucial contributors to the promotion of epithelial repair underscores their potential as therapeutic targets in chemical-induced acute lung injury.

Targeting Fibrosis: From Molecular Mechanisms to Advanced Therapies

As the final stage of disease-related tissue injury and repair, fibrosis is characterized by excessive accumulation of the extracellular matrix. Unrestricted accumulation of stromal cells and matrix during fibrosis impairs the structure and function of organs, ultimately leading to organ failure. The major etiology of fibrosis is an injury caused by genetic heterogeneity, trauma, virus infection, alcohol, mechanical stimuli, and drug. Persistent abnormal activation of "quiescent" fibroblasts that interact with or do not interact with the immune system via complicated signaling cascades, in which parenchymal cells are also triggered, is identified as the main mechanism involved in the initiation and progression of fibrosis. Although the mechanisms of fibrosis are still largely unknown, multiple therapeutic strategies targeting identified molecular mechanisms have greatly attenuated fibrotic lesions in clinical trials. In this review, the organ-specific molecular mechanisms of fibrosis is systematically summarized, including cardiac fibrosis, hepatic fibrosis, renal fibrosis, and pulmonary fibrosis. Some important signaling pathways associated with fibrosis are also introduced. Finally, the current antifibrotic strategies based on therapeutic targets and clinical trials are discussed. A comprehensive interpretation of the current mechanisms and therapeutic strategies targeting fibrosis will provide the fundamental theoretical basis not only for fibrosis but also for the development of antifibrotic therapies.

Innovative approaches in lung tissue engineering: the role of exosome-loaded bioscaffolds in regenerative medicine

Lung diseases account for over four million premature deaths every year, and experts predict that this number will increase in the future. The top cause of death globally is diseases which include conditions like lung cancer asthma and COPD. Treating severe acute lung injury is a complex task because lungs struggle to heal themselves in the presence of swelling inflammation and scarring caused by damage, to the lung tissues. Though achieving lung regeneration, in controlled environments is still an ambition; ongoing studies are concentrating on notable progress, in the field of lung tissue engineering and methods for repairing lung damage. This review delves into methods, for regenerating lungs with a focus on exosome carry bioscaffolds and mesenchymal stem cells among others. It talks about how these new techniques can help repair lung tissue and improve lung function in cases of damage. Also noted is the significance of ex vivo lung perfusion (EVLP), for rejuvenating donor lungs and the healing properties of exosomes in supporting lung regeneration.

Autologous transplantation of lung progenitor cells comes into reality for bronchiectasis

Stem and progenitor cell-based regenerative therapies have the potential to cure chronic respiratory diseases. Yan et al.1 reported a clinical trial of autologous P63+ progenitor cell transplantation in bronchiectasis patients, highlighting autologous transplantation of P63+ progenitor cells as a novel candidate therapeutic option to improve pulmonary gas exchange function and quality of life.

Autologous transplantation of P63+ lung progenitor cells in patients with bronchiectasis: A randomized, single-blind, controlled trial

Non-cystic fibrosis bronchiectasis is a progressive respiratory disease with limited treatment options, prompting the exploration of regenerative therapies. This study investigates the safety and efficacy of autologous P63+ progenitor cell transplantation in a randomized, single-blind, controlled, phase 1/2 trial. Thirty-seven patients receive bronchoscopic airway clearance (B-ACT) (n = 19) or B-ACT plus P63+ progenitor cells (n = 18). Results show that compared to the control group, the change in DLCO levels from baseline to 24 weeks post therapy is significantly higher in the cell treatment group (p value = 0.039). Furthermore, the patients in the cell treatment group demonstrate significantly reduced lung damaged area, improved SGRQ score, and ameliorated BSI and FACED scores within 4-12 weeks post therapy. Transcriptomic analysis reveals that progenitor cells with higher expression of P63 gene have better therapeutic efficacy. These findings suggest that P63+ progenitor cells may offer a promising therapeutic approach for bronchiectasis. This study was registered at ClinicalTrials.gov(NCT03655808).

Targeted pre-conditioning and cell transplantation in the murine lower respiratory tract

Transplantation of airway basal stem cells could achieve a durable cure for genetic diseases of the airway, such as cystic fibrosis and primary ciliary dyskinesia. Recent work demonstrated the potential of primary- and pluripotent stem cell (PSC)-derived basal cells to efficiently engrai into the mouse trachea aier injury. However, there are many hurdles to overcome in translating these approaches to humans including developing safe and efficient methods for delivery in larger animal models. We propose a model which targets preconditioning and cell-delivery to the intrapulmonary airways utilizing a micro- bronchoscope for delivery. The detergent polidocanol was adapted for distal lung pre-conditioning, inducing intrapulmonary airway epithelial denudation by 5 and 24-hours post-delivery. While initial re- epithelialization of airways occurred later than tracheas, complete repair was observed within 7-days. Both PSC-derived and primary basal cells delivered via micro-bronchoscope post-polidocanol injury engraied in tracheas and intrapulmonary airways, respectively. Transplanted cells differentiated into ciliated and secretory lineages while maintaining a population of basal cells. These findings demonstrate the utility of bronchoscopically targeted pre-conditioning and cell delivery to the conducting intra- pulmonary airways, providing an important framework for pre-clinical translation of approaches for engineered airway epithelial regeneration.

High-parametric protein maps reveal the spatial organization in early-developing human lung

The respiratory system, including the lungs, is essential for terrestrial life. While recent research has advanced our understanding of lung development, much still relies on animal models and transcriptome analyses. In this study conducted within the Human Developmental Cell Atlas (HDCA) initiative, we describe the protein-level spatiotemporal organization of the lung during the first trimester of human gestation. Using high-parametric tissue imaging with a 30-plex antibody panel, we analyzed human lung samples from 6 to 13 post-conception weeks, generating data from over 2 million cells across five developmental timepoints. We present a resource detailing spatially resolved cell type composition of the developing human lung, including proliferative states, immune cell patterns, spatial arrangement traits, and their temporal evolution. This represents an extensive single-cell resolved protein-level examination of the developing human lung and provides a valuable resource for further research into the developmental roots of human respiratory health and disease.

Notch signaling regulates pulmonary fibrosis

Pulmonary fibrosis is a progressive interstitial lung disease associated with aging. The pathogenesis of pulmonary fibrosis remains unclear, however, alveolar epithelial cell injury, myofibroblast activation, and extracellular matrix (ECM) accumulation are recognized as key contributors. Moreover, recent studies have implicated cellular senescence, endothelial-mesenchymal transition (EndMT), and epigenetic modifications in the pathogenesis of fibrotic diseases. Various signaling pathways regulate pulmonary fibrosis, including the TGF-β, Notch, Wnt, Hedgehog, and mTOR pathways. Among these, the TGF-β pathway is extensively studied, while the Notch pathway has emerged as a recent research focus. The Notch pathway influences the fibrotic process by modulating immune cell differentiation (e.g., macrophages, lymphocytes), inhibiting autophagy, and promoting interstitial transformation. Consequently, inhibiting Notch signaling represents a promising approach to mitigating pulmonary fibrosis. In this review, we discuss the role of Notch signaling pathway in pulmonary fibrosis, aiming to offer insights for future therapeutic investigations.

Identifying prothrombin and bone sialoprotein as potential drug targets for idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic Pulmonary Fibrosis (IPF) is a fatal disease with scarce therapeutic alternatives, which imposes a significant economic burden on society. The identification of novel drug targets is thus critically essential. Plasma proteins with discernible causal evidence hold promise as viable drug targets for this condition.

METHODS

We performed a proteome-wide Mendelian randomization (MR) analysis to assess the causal effects of 4,907 circulating proteins from the deCODE study on the risk of IPF from the Finngen Database (2,018 cases vs. 373,064 controls). We further replicated the MR analysis in 1426 proteins from the ARIC study and IPF from the UK Biobank (1,369 cases vs. 435,866 controls). Then a series of analyses including Bayesian colocalization, Steiger filtering, and phenotype scanning were conducted to validate the credibility of the MR results. Subsequently, protein-protein interaction (PPI) analysis, pathway enrichment analysis, and druggability assessment were executed to elucidate the underlying mechanisms. Finally, the findings were corroborated using a bleomycin-induced pulmonary fibrosis mouse model.

RESULTS

The MR analysis bolstered by robust evidence of colocalization, indicated a significant positive association between Prothrombin and increased IPF risk (OR = 3.26,95%CI 1.75-6.07). Conversely, Bone Sialoprotein (IBSP) demonstrated an inverse association with IPF susceptibility (OR = 0.27,95%CI 0.14-0.55).

CONCLUSIONS

The integrative analysis suggests that Prothrombin and IBSP are promising candidates as potential drug targets for IPF. Additional clinical investigations are warranted to substantiate these findings.

Multi-Tissue Integrated Tissue-Engineered Trachea Regeneration Based on 3D Printed Bioelastomer Scaffolds

Functional segmental trachea reconstruction is a critical concern in thoracic surgery, and tissue-engineered trachea (TET) holds promise as a potential solution. However, current TET falls short in fully restoring physiological function due to the lack of the intricate multi-tissue structure found in natural trachea. In this research, a multi-tissue integrated tissue-engineered trachea (MI-TET) is successfully developed by orderly assembling various cells (chondrocytes, fibroblasts and epithelial cells) on 3D-printed PGS bioelastomer scaffolds. The MI-TET closely resembles the complex structures of natural trachea and achieves the integrated regeneration of four essential tracheal components: C-shaped cartilage ring, O-shaped vascularized fiber ring, axial fiber bundle, and airway epithelium. Overall, the MI-TET demonstrates highly similar multi-tissue structures and physiological functions to natural trachea, showing promise for future clinical advancements in functional TETs.

Connexin 25 maintains self-renewal and functions of airway basal cells for airway regeneration

BACKGROUND

The formation of stem cell clones enables close contact of stem cells inside. The gap junctions in such clone spheres establish a microenvironment that allows frequent intercellular communication to maintain self-renewal and functions of stem cells. Nevertheless, the essential gap junction protein for molecular signaling in clones is poorly known.

METHODS

Primary human airway basal cells (hBCs) were isolated from brushing samples through bronchoscopy and then cultured. A tightly focused femtosecond laser was used to excite the local Ca2+ in an individual cell to initiate an internal Ca2+ wave in a clone to screen gap junction proteins. Immunoflourescence staining and clonogenicity assay were used to evaluate self-renewal and functions. RNA and protein levels were assessed by PCR and Western blot. Air-liquid interface assay was conducted to evaluate the differentiation potential. A Naphthalene injury mouse model was used to assess the regeneration potential.

RESULTS

Herein, we identify Connexin 25 (Cx25) dominates intercellular Ca2+ communications in clones of hBCs in vitro to maintain the self-renewal and pluripotency of them. The self-renewal and in vitro differentiation functions and in vivo regeneration potential of hBCs in an airway damage model are both regulated by Cx25. The abnormal expression of Cx25 is validated in several diseases including IPF, Covid-19 and bronchiectasis.

CONCLUSION

Cx25 is essential for hBC clones in maintaining self-renewal and functions of hBCs via gap junctions.

Lung cell transplantation for pulmonary fibrosis

Idiopathic pulmonary fibrosis is a major cause of death with few treatment options. Here, we demonstrate the therapeutic efficacy for lung fibrosis of adult lung cell transplantation using a single-cell suspension of the entire lung in two distinct mouse systems: bleomycin treatment and mice lacking telomeric repeat-binding factor 1 expression in alveolar type 2 (AT2) cells (SPC-Cre TRF1fl/fl), spontaneously developing fibrosis. In both models, the progression of fibrosis was associated with reduced levels of host lung progenitors, enabling engraftment of donor progenitors without any additional conditioning, in contrast to our previous studies. Two months after transplantation, engrafted progenitors expanded to form numerous donor-derived patches comprising AT1 and AT2 alveolar cells, as well as donor-derived mesenchymal and endothelial cells. This lung chimerism was associated with attenuation of fibrosis, as demonstrated histologically, biochemically, by computed tomography imaging, and by lung function measurements. Our study provides a strong rationale for the treatment of lung fibrosis using lung cell transplantation.

Airway basal cell‑derived exosomes suppress epithelial‑mesenchymal transition of lung cells by inhibiting the expression of ANO1

Disruption of the epithelial-mesenchymal transition (EMT) of activated lung cells is an important strategy to inhibit the progression of idiopathic pulmonary fibrosis (IPF). The present study investigated the role of exosomes derived from airway basal cells on EMT of lung cells and elucidate the underlying mechanism. Exosomes were characterized by nanoparticle tracking analysis, transmission electron microscopy imaging and markers detection. The role of exosome on the EMT of lung epithelial cells and lung fibroblasts induced by TGF-β1 was detected. RNA sequencing screened dysregulated genes in exosome-treated group, followed by the bioinformatical analysis. One of the candidates, anoctamin-1 (ANO1), was selected for further gain-and-loss phenotype assays. A bleomycin-induced pulmonary fibrosis model was used to evaluate the treatment effect of exosomes. Exosomes were round-like and positively expressed CD63 and tumor susceptibility gene 101 protein. Treatment with exosomes inhibited the EMT of lung cells activated by TGF-β1. 4158 dysregulated genes were identified in exosome-treated group under the threshold of |log2 fold-change| value >1 and they were involved in the metabolism of various molecules, as well as motility-related biological processes. A key gene, ANO1, was verified by reverse transcription-quantitative PCR, whose overexpression induced the EMT of lung cells. By contrast, ANO1 knockdown reversed the EMT induced by TGF-β1. In vivo assay indicated that exosome treatment ameliorated pulmonary fibrosis and inhibited the upregulation of ANO1 induced by bleomycin. In conclusion, airway basal cell-derived exosomes suppressed the EMT of lung cells via the downregulation of ANO1. These exosomes represent a potential therapeutic option for patients with IPF.

The novel molecular mechanism of pulmonary fibrosis: insight into lipid metabolism from reanalysis of single-cell RNA-seq databases

Pulmonary fibrosis (PF) is a severe pulmonary disease with limited available therapeutic choices. Recent evidence increasingly points to abnormal lipid metabolism as a critical factor in PF pathogenesis. Our latest research identifies the dysregulation of low-density lipoprotein (LDL) is a new risk factor for PF, contributing to alveolar epithelial and endothelial cell damage, and fibroblast activation. In this study, we first integrative summarize the published literature about lipid metabolite changes found in PF, including phospholipids, glycolipids, steroids, fatty acids, triglycerides, and lipoproteins. We then reanalyze two single-cell RNA-sequencing (scRNA-seq) datasets of PF, and the corresponding lipid metabolomic genes responsible for these lipids' biosynthesis, catabolism, transport, and modification processes are uncovered. Intriguingly, we found that macrophage is the most active cell type in lipid metabolism, with almost all lipid metabolic genes being altered in macrophages of PF. In type 2 alveolar epithelial cells, lipid metabolic differentially expressed genes (DEGs) are primarily associated with the cytidine diphosphate diacylglycerol pathway, cholesterol metabolism, and triglyceride synthesis. Endothelial cells are partly responsible for sphingomyelin, phosphatidylcholine, and phosphatidylethanolamines reprogramming as their metabolic genes are dysregulated in PF. Fibroblasts may contribute to abnormal cholesterol, phosphatidylcholine, and phosphatidylethanolamine metabolism in PF. Therefore, the reprogrammed lipid profiles in PF may be attributed to the aberrant expression of lipid metabolic genes in different cell types. Taken together, these insights underscore the potential of targeting lipid metabolism in developing innovative therapeutic strategies, potentially leading to extended overall survival in individuals affected by PF.

SOX9 promotes stemness in the CAL27 cell line of tongue squamous cell carcinoma

Tongue squamous cell carcinoma (TSCC) is a prevalent form of oral malignancy, with increasing incidence. Unfortunately, the 5-year survival rate for patients has not exceeded 50%. Studies have shown that sex-determining region Y box 9 (SOX9) correlates with malignancy and tumor stemness in a variety of tumors. To investigate the role of SOX9 in TSCC stemness, we analyzed its influence on various aspects of tumor biology, including cell proliferation, migration, invasion, sphere and clone formation, and drug resistance in TSCC. Our data suggest a close association between SOX9 expression and both the stemness phenotype and drug resistance in TSCC. Immunohistochemical experiments revealed a progressive increase of SOX9 expression in normal oral mucosa, paracancerous tissues, and tongue squamous carcinoma tissues. Furthermore, the expression of SOX9 was closely linked to the TNM stage, but not to lymph node metastasis or tumor diameter. SOX9 is a crucial gene in TSCC responsible for promoting the stemness function of cancer stem cells. Developing drugs that target SOX9 is extremely important in clinical settings.

Viral airway injury promotes cell engraftment in an in vitro model of cystic fibrosis cell therapy

Cell therapy is a potential treatment for cystic fibrosis (CF). However, cell engraftment into the airway epithelium is challenging. Here, we model cell engraftment in vitro using the air-liquid interface (ALI) culture system by injuring well-differentiated CF ALI cultures and delivering non-CF cells at the time of peak injury. Engraftment efficiency was quantified by measuring chimerism by droplet digital PCR and functional ion transport in Ussing chambers. Using this model, we found that human bronchial epithelial cells (HBECs) engraft more efficiently when they are cultured by conditionally reprogrammed cell (CRC) culture methods. Cell engraftment into the airway epithelium requires airway injury, but the extent of injury needed is unknown. We compared three injury models and determined that severe injury with partial epithelial denudation facilitates long-term cell engraftment and functional CFTR recovery up to 20% of wildtype function. The airway epithelium promptly regenerates in response to injury, creating competition for space and posing a barrier to effective engraftment. We examined competition dynamics by time-lapse confocal imaging and found that delivered cells accelerate airway regeneration by incorporating into the epithelium. Irradiating the repairing epithelium granted engrafting cells a competitive advantage by diminishing resident stem cell proliferation. Intentionally, causing severe injury to the lungs of people with CF would be dangerous. However, naturally occurring events like viral infection can induce similar epithelial damage with patches of denuded epithelium. We found that viral preconditioning promoted effective engraftment of cells primed for viral resistance.NEW & NOTEWORTHY Cell therapy is a potential treatment for cystic fibrosis (CF). Here, we model cell engraftment by injuring CF air-liquid interface cultures and delivering non-CF cells. Successful engraftment required severe epithelial injury. Intentionally injuring the lungs to this extent would be dangerous. However, naturally occurring events like viral infection induce similar epithelial damage. We found that viral preconditioning promoted the engraftment of cells primed for viral resistance leading to CFTR functional recovery to 20% of the wildtype.

Autologous transplantation of P63+ lung progenitor cells for chronic obstructive pulmonary disease therapy

Adult lung resident stem/progenitor cells, including P63+ progenitor cells, have demonstrated the capacity for regeneration of lung epithelium in preclinical models. Here, we report a clinical trial of intrapulmonary P63+ progenitor cell transplantation in 28 participants with stage II to IV chronic obstructive pulmonary disease (COPD). Autologous P63+ progenitor cells were isolated from the airway basal layer of participants in the intervention group via bronchoscopic brushing, cultured for 3 to 5 weeks, and then transplanted back into the lungs via bronchoscopy at 0.7 × 106 to 5.2 × 106 cells per kilogram of body weight. Twenty patients were evaluable at the end of the study (intervention group, n = 17; control group, n = 3). No grade 3 to 5 adverse events (AEs) or serious AEs occurred. Although bronchoscopy-associated AEs were recorded in participants in the intervention group, other AEs were not substantial different between groups. Twenty-four weeks after transplantation, participants in the intervention group displayed improvement in gas transfer capacity [diffusing capacity of the lung for carbon monoxide (DLCO) change from baseline: +18.2%], whereas the control group experienced a decrease (DLCO change from baseline: -17.4%; P = 0.008). Furthermore, participants in the intervention group showed >30-meter increase in walking distance within 6 minutes. Transcriptomic analysis of progenitor cells isolated from responding and nonresponding individuals in the intervention group showed that higher expression of P63 was associated with treatment efficacy. In conclusion, transplantation of cultured P63+ lung progenitor cells was safe and might represent a potential therapeutic strategy for COPD.

SOX on tumors, a comfort or a constraint?

The sex-determining region Y (SRY)-related high-mobility group (HMG) box (SOX) family, composed of 20 transcription factors, is a conserved family with a highly homologous HMG domain. Due to their crucial role in determining cell fate, the dysregulation of SOX family members is closely associated with tumorigenesis, including tumor invasion, metastasis, proliferation, apoptosis, epithelial-mesenchymal transition, stemness and drug resistance. Despite considerable research to investigate the mechanisms and functions of the SOX family, confusion remains regarding aspects such as the role of the SOX family in tumor immune microenvironment (TIME) and contradictory impacts the SOX family exerts on tumors. This review summarizes the physiological function of the SOX family and their multiple roles in tumors, with a focus on the relationship between the SOX family and TIME, aiming to propose their potential role in cancer and promising methods for treatment.

Physiological and immunological barriers in the lung

The lungs serve as the primary organ for respiration, facilitating the vital exchange of gases with the bloodstream. Given their perpetual exposure to external particulates and pathogens, they possess intricate protective barriers. Cellular adhesion in the lungs is robustly maintained through tight junctions, adherens junctions, and desmosomes. Furthermore, the pulmonary system features a mucociliary clearance mechanism that synthesizes mucus and transports it to the outside. This mucus is enriched with chemical barriers like antimicrobial proteins and immunoglobulin A (IgA). Additionally, a complex immunological network comprising epithelial cells, neural cells, and immune cells plays a pivotal role in pulmonary defense. A comprehensive understanding of these protective systems offers valuable insights into potential pathologies and their therapeutic interventions.

Airway epithelium regeneration by photoactivated basal cells

The airway epithelium is the footstone to maintain the structure and functions of lung, in which resident basal cells (BCs) maintain homeostasis and functional regeneration of epithelial barrier in response to injury. In recent clinical researches, transplanting BCs has shown great inspiring achievements in therapy of various lung diseases. In this study, we report a noninvasive optical method to activate BCs for airway epithelium regeneration in vivo by fast scanning of focused femtosecond laser on BCs of airway epithelium to active Ca2+ signaling and subsequent ERK and Wnt pathways. The photoactivated BCs present high proliferative capacity and maintain high pluripotency, which enables them to plant in the injured airway epithelium and differentiate to club cells for regeneration of epithelium. This optical method can also work in situ to activate localized BCs in airway tissue. Therefore, our results provide a powerful technology for noninvasive BC activation in stem-cell therapy of lung diseases.

Biomimetic scaffold-based stem cell transplantation promotes lung regeneration

Therapeutic options are limited for severe lung injury and disease as the spontaneous regeneration of functional alveolar is terminated owing to the weakness of the inherent stem cells and the dyscrasia of the niche. Umbilical cord mesenchymal-derived stem cells (UC-MSCs) have been applied to clinical trials to promote lung repair through stem cell niche restruction. However, the application of UC-MSCs is hampered by the effectiveness of cell transplantation with few cells homing to the injury sites and poor retention, survival, and proliferation in vivo. In this study, we constructed an artificial three-dimensional (3D) biomimetic scaffold-based MSCs implant to establish a beneficial regeneration niche for endogenous stem cells in situ lung regeneration. The therapeutic potential of 3D biomimetic scaffold-based MSCs implants was evaluated by 3D culture in vitro. And RNA sequencing (RNA-Seq) was mapped to explore the gene expression involved in the niche improvement. Next, a model of partial lung resection was established in rats, and the implants were implanted into the operative region. Effects of the implants on rat resected lung injury repair were detected. The results revealed that UC-MSCs loaded on biomimetic scaffolds exerted strong paracrine effects and some UC-MSCs migrated to the lung from scaffolds and had long-term retention to suppress inflammation and fibrosis in residual lungs and promoted vascular endothelial cells and alveolar type II epithelial cells to enter the scaffolds. Then, under the guidance of the ECM-mimicking structures of scaffolds and the stimulation of the remaining UC-MSCs, vascular and alveolar-like structures were formed in the scaffold region. Moreover, the general morphology of the operative lung was also restored. Taken together, the artificial 3D biomimetic scaffold-based MSCs implants induce in situ lung regeneration and recovery after lung destruction, providing a promising direction for tissue engineering and stem cell strategies in lung regeneration.

When GETomics meets aging and exercise in COPD

The term GETomics has been recently proposed to illustrate that human health and disease are actually the final outcome of many dynamic, interacting and cumulative gene (G) - environment (E) interactions that occur through the lifetime (T) of the individual. According to this new paradigm, the final outcome of any GxE interactions depends on both the age of the individual at which such GxE interaction occurs as well as on the previous, cumulative history of previous GxE interactions through the induction of epigenetic changes and immune memory (both lasting overtime). Following this conceptual approach, our understanding of the pathogenesis of chronic obstructive pulmonary disease (COPD) has changed dramatically. Traditionally believed to be a self-inflicted disease induced by tobacco smoking occurring in older men and characterized by an accelerated decline of lung function with age, now we understand that there are many other risk factors associated with COPD, that it occurs also in females and young individuals, that there are different lung function trajectories through life, and that COPD is not always characterized by accelerated lung function decline. In this paper we discuss how a GETomics approach to COPD may open new perspectives to better understand its relationship with exercise limitation and the ageing process.

Human lung organoid: Models for respiratory biology and diseases

The human respiratory system, consisting of the airway and alveoli, is one of the most complex organs directly interfaced with the external environment. The diverse epithelial cells lining the surface are usually the first cell barrier that comes into contact with pathogens that could lead to deadly pulmonary disease. There is an urgent need to understand the mechanisms of self-renewal and protection of these epithelial cells against harmful pathogens, such as SARS-CoV-2. Traditional models, including cell lines and mouse models, have extremely limited native phenotypic features. Therefore, in recent years, to mimic the complexity of the lung, airway and alveoli organoid technology has been developed and widely applied. TGF-β/BMP/SMAD, FGF and Wnt/β-catenin signaling have been proven to play a key role in lung organoid expansion and differentiation. Thus, we summarize the current novel lung organoid culture strategies and discuss their application for understanding the lung biological features and pathophysiology of pulmonary diseases, especially COVID-19. Lung organoids provide an excellent in vitro model and research platform.

Pulmonary endogenous progenitor stem cell subpopulation: Physiology, pathogenesis, and progress

Lungs are structurally and functionally complex organs consisting of diverse cell types from the proximal to distal axis. They have direct contact with the external environment and are constantly at risk of various injuries. Capable to proliferate and differentiate, pulmonary endogenous progenitor stem cells contribute to the maintenance of lung structure and function both under homeostasis and following injuries. Discovering candidate pulmonary endogenous progenitor stem cell types and underlying regenerative mechanisms provide insights into therapeutic strategy development for lung diseases. In this review, we reveal their compositions, roles in lung disease pathogenesis and injury repair, and the underlying mechanisms. We further underline the advanced progress in research approach and potential therapy for lung regeneration. We also demonstrate the feasibility and prospects of pulmonary endogenous stem cell transplantation for lung disease treatment.

NLRP3 Inflammasome Mediates Silica-induced Lung Epithelial Injury and Aberrant Regeneration in Lung Stem/Progenitor Cell-derived Organotypic Models

Silica-induced lung epithelial injury and fibrosis are vital pathogeneses of silicosis. Although the NOD-like receptor protein 3 (NLRP3) inflammasome contributes to silica-induced chronic lung inflammation, its role in epithelial injury and regeneration remains unclear. Here, using mouse lung stem/progenitor cell-derived organotypic systems, including 2D air-liquid interface and 3D organoid cultures, we investigated the effects of the NLRP3 inflammasome on airway epithelial phenotype and function, cellular injury and regeneration, and the potential mechanisms. Our data showed that silica-induced NLRP3 inflammasome activation disrupted the epithelial architecture, impaired mucociliary clearance, induced cellular hyperplasia and the epithelial-mesenchymal transition in 2D culture, and inhibited organoid development in 3D system. Moreover, abnormal expression of the stem/progenitor cell markers SOX2 and SOX9 was observed in the 2D and 3D organotypic models after sustained silica stimulation. Notably, these silica-induced structural and functional abnormalities were ameliorated by MCC950, a selective NLRP3 inflammasome inhibitor. Further studies indicated that the NF-κB, Shh-Gli and Wnt/β-catenin pathways were involved in NLRP3 inflammasome-mediated abnormal differentiation and dysfunction of the airway epithelium. Thus, prolonged NLRP3 inflammasome activation caused injury and aberrant lung epithelial regeneration, suggesting that the NLRP3 inflammasome is a pivotal target for regulating tissue repair in chronic inflammatory lung diseases.

Repairing Mechanisms for Distal Airway Injuries and Related Targeted Therapeutics for Chronic Lung Diseases

Chronic lung diseases, such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF), involve progressive and irreversible destruction and pathogenic remodeling of airways and have become the leading health care burden worldwide. Pulmonary tissue has extensive capacities to launch injury-responsive repairing programs (IRRPs) to replace the damaged or dead cells upon acute lung injuries. However, the IRRPs are frequently compromised in chronic lung diseases. In this review, we aim to provide an overview of somatic stem cell subpopulations within distal airway epithelium and the underlying mechanisms mediating their self-renewal and trans-differentiation under both physiological and pathological circumstances. We also compared the differences between humans and mice on distal airway structure and stem cell composition. At last, we reviewed the current status and future directions for the development of targeted therapeutics on defective distal airway regeneration and repairment in chronic lung diseases.

Exploiting the potential of lung stem cells to develop pro-regenerative therapies

Acute and chronic lung diseases are a leading cause of morbidity and mortality globally. Unfortunately, these diseases are increasing in frequency and we have limited treatment options for severe lung diseases. New therapies are needed that not only treat symptoms or slow disease progression, but also enable the regeneration of functional lung tissue. Both airways and alveoli contain populations of epithelial stem cells with the potential to self-renew and produce differentiated progeny. Understanding the mechanisms that determine the behaviour of these cells, and their interactions with their niches, will allow future generations of respiratory therapies that protect the lungs from disease onset, promote regeneration from endogenous stem cells or enable regeneration through the delivery of exogenous cells. This review summarises progress towards each of these goals, highlighting the challenges and opportunities of developing pro-regenerative (bio)pharmaceutical, gene and cell therapies for respiratory diseases.

Promises and Challenges of Cell-Based Therapies to Promote Lung Regeneration in Idiopathic Pulmonary Fibrosis

The lung epithelium is constantly exposed to harmful agents present in the air that we breathe making it highly susceptible to damage. However, in instances of injury to the lung, it exhibits a remarkable capacity to regenerate injured tissue thanks to the presence of distinct stem and progenitor cell populations along the airway and alveolar epithelium. Mechanisms of repair are affected in chronic lung diseases such as idiopathic pulmonary fibrosis (IPF), a progressive life-threatening disorder characterized by the loss of alveolar structures, wherein excessive deposition of extracellular matrix components cause the distortion of tissue architecture that limits lung function and impairs tissue repair. Here, we review the most recent findings of a study of epithelial cells with progenitor behavior that contribute to tissue repair as well as the mechanisms involved in mouse and human lung regeneration. In addition, we describe therapeutic strategies to promote or induce lung regeneration and the cell-based strategies tested in clinical trials for the treatment of IPF. Finally, we discuss the challenges, concerns and limitations of applying these therapies of cell transplantation in IPF patients. Further research is still required to develop successful strategies focused on cell-based therapies to promote lung regeneration to restore lung architecture and function.

Roles of airway basal stem cells in lung homeostasis and regenerative medicine

Airway basal stem cells (BSCs) in the proximal airways are recognized as resident stem cells capable of self-renewing and differentiating to virtually every pseudostratified epithelium cell type under steady-state and after acute injury. In homeostasis, BSCs typically maintain a quiescent state. However, when exposed to acute injuries by either physical insults, chemical damage, or pathogen infection, the remaining BSCs increase their proliferation rate apace within the first 24 h and differentiate to restore lung homeostasis. Given the progenitor property of airway BSCs, it is attractive to research their biological characteristics and how they maintain homeostatic airway structure and respond to injury. In this review, we focus on the roles of BSCs in lung homeostasis and regeneration, detail the research progress in the characteristics of airway BSCs, the cellular and molecular signaling communications involved in BSCs-related airway repair and regeneration, and further discuss the in vitro models for airway BSC propagation and their applications in lung regenerative medicine therapy.

SARS-CoV-2 Infection and Lung Regeneration

The lung is the primary site of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced immunopathology whereby the virus enters the host cells by binding to angiotensin-converting enzyme 2 (ACE2). Sophisticated regeneration and repair programs exist in the lungs to replenish injured cell populations. However, known resident stem/progenitor cells have been demonstrated to express ACE2, raising a substantial concern regarding the long-term consequences of impaired lung regeneration after SARS-CoV-2 infection. Moreover, clinical treatments may also affect lung repair from antiviral drug candidates to mechanical ventilation. In this review, we highlight how SARS-CoV-2 disrupts a program that governs lung homeostasis. We also summarize the current efforts of targeted therapy and supportive treatments for COVID-19 patients. In addition, we discuss the pros and cons of cell therapy with mesenchymal stem cells or resident lung epithelial stem/progenitor cells in preventing post-acute sequelae of COVID-19. We propose that, in addition to symptomatic treatments being developed and applied in the clinic, targeting lung regeneration is also essential to restore lung homeostasis in COVID-19 patients.

CoQ10 enhances the efficacy of airway basal stem cell transplantation on bleomycin-induced idiopathic pulmonary fibrosis in mice

Background

Recent studies have demonstrated that airway basal stem cells (BCs) transplantation can ameliorate bleomycin-induced idiopathic pulmonary fibrosis (IPF) through lung regeneration promotion. However, BCs under oxidative stress in the alveolar microenvironment are poor in survival, causing unsatisfied efficacy of BCs transplantation. In this study, we investigated whether Coenzyme Q10(CoQ10) counteracts oxidative stress in the alveolar microenvironment, thus improved the efficacy of BCs transplantation for IPF treatment.

Methods

The protective effects of CoQ10 on H₂O₂-induced BCs apoptosis and cytoplasmic reactive oxygen species (ROS) level were tested by flow cytometry in vitro. The therapeutic effects of BCs combined with CoQ10 were compared to a single BCs transplantation protocol in IPF treatment after 2 weeks and were evaluated by parameters including changes of body weight and survival rate, as well as various levels of pulmonary inflammation, α-SMA expression and hydroxyproline (HYP) in IPF mouse lung tissues.

Results

CoQ10 preincubation with BCs (10 mM, 24 h) significantly reduced the late apoptosis of BCs and the number of oxidative stressful BCs as a result of H₂O₂ stimulation (1 mM, 6 h) in vitro. IPF mouse model was constructed through bleomycin (5 mg/kg) intratracheal instillation. Bleomycin-induced IPF mice showed weight loss continuously and mortality increased progressively during modeling. Serious pulmonary inflammatory cell infiltration, collagen fiber proliferation, and collagen protein deposition were observed in lung tissues of IPF mice. Though BCs transplantation alone improved indicators above in bleomycin-induced IPF mice to some extent, the combination with CoQ10 improved the transplantation efficacy and obtained better therapeutic effects.

Conclusion

CoQ10 blocked H₂O₂-induced apoptosis of BCs and ROS production in vitro, and enhanced the efficacy of BCs transplantation against bleomycin-induced IPF in mice.

Abnormal respiratory progenitors in fibrotic lung injury

Recent advances in single-cell RNA sequencing (scRNA-seq) and epithelium lineage labeling have yielded identification of multiple abnormal epithelial progenitor populations during alveolar type 2 (ATII) cell differentiation into alveolar type 1 (ATI) cells during regenerative lung post-fibrotic injury. These abnormal cells include basaloid/basal-like cells, ATII transition cells, and persistent epithelial progenitors (PEPs). These cells occurred and accumulated during the regeneration of distal airway and alveoli in response to both chronic and acute pulmonary injury. Among the alveolar epithelial progenitors, PEPs express a distinct Krt8+ phenotype that is rarely found in intact alveoli. However, post-injury, the Krt8+ phenotype is seen in dysplastic epithelial cells. Fully understanding the characteristics and functions of these newly found, injury-induced abnormal behavioral epithelial progenitors and the signaling pathways regulating their phenotype could potentially point the way to unique therapeutic targets for fibrosing lung diseases. This review summarizes recent advances in understanding these epithelial progenitors as they relate to uncovering regenerative mechanisms.

Single-cell analysis defines the lineage plasticity of stem cells in cervix epithelium

Information about the dynamic change and post-injury regeneration of cervical epithelium is relatively rare, even though it is tightly related to gynecologic malignancy. Here, using a feeder cell-based culturing system, we stably cloned mouse and human P63 and KRT5 expressing cells from the adult cervix as putative cervical stem/progenitor cells (CVSCs). When subjected to differentiation, the cultured cells gave rise to mature cervical epithelium by differentiating into squamous or glandular cells. The ability of endogenous mouse CVSCs to reconstitute cervical epithelium after injury was also evident from the genetic lineage tracing experiments. Single-cell transcriptomic analysis further classified the CVSCs into three subtypes and delineated their bi-lineage differentiation roadmap by pseudo-time analysis. We also tracked the real-time differentiation routes of two representing single CVSC lines in vitro and found that they recapitulated the predicted roadmap in pseudo-time analysis. Signaling pathways including Wnt, TGF-beta, Notch and EGFR were found to regulate the cervical epithelial hierarchy and implicated the different roles of distinct types of cells in tissue homeostasis and tumorigenesis. Collectively, the above data provide a cloning system to achieve stable in vitro culture of a bi-lineage stem/progenitor cell population in the cervix, which has profound implications for our understanding of the cervix stem/progenitor cell function in homeostasis, regeneration, and disease and could be helpful for developing stem cell-based therapies in future.

Stable Long-Term Culture of Human Distal Airway Stem Cells for Transplantation

There is a population of p63⁺/Krt5⁺ distal airway stem cells (DASCs) quiescently located in the airway basal epithelium of mammals, responding to injury and airway epithelial regeneration. They hold the ability to differentiate into multiple pulmonary cell types and can repopulate the epithelium after damage. The current study aims at gaining further insights into the behavior and characteristics of the DASCs isolated from the patient lung and exploring their clinical translational potential. Human DASCs were brushed off through the bronchoscopic procedure and expanded under the pharmaceutical-grade condition. Their phenotype stability in long-term cell culture was analyzed, followed by safety evaluation and tumorigenic analysis using multiple animal models including rodents and nonhuman primate. The chimerism of the human-mouse lung model indicated that DASC pedigrees could give rise to multiple epithelial types, including type I alveolar cells as well as bronchiolar secretory cells, to regenerate the distal lung. Taken together, the results suggested that DASC transplantation could be a promising therapeutic approach for unmet needs in respiratory medicine including the COVID-19-related diseases.

Expression of Piwi, MMP, TIMP, and Sox during Gut Regeneration in Holothurian Eupentacta fraudatrix (Holothuroidea, Dendrochirotida)

Mesodermal cells of holothurian Eupentacta fraudatrix can transdifferentiate into enterocytes during the regeneration of the digestive system. In this study, we investigated the expression of several genes involved in gut regeneration in E. fraudatrix. Moreover, the localization of progenitor cells of coelomocytes, juvenile cells, and their participation in the formation of the luminal epithelium of the digestive tube were studied. It was shown that Piwi-positive cells were not involved in the formation of the luminal epithelium of the digestive tube. Ef-72 kDa type IV collagenase and Ef-MMP16 had an individual expression profile and possibly different functions. The Ef-tensilin3 gene exhibited the highest expression and indicates its potential role in regeneration. Ef-Sox9/10 and Ef-Sox17 in E. fraudatrix may participate in the mechanism of transdifferentiation of coelomic epithelial cells. Their transcripts mark the cells that plunge into the connective tissue of the gut anlage and give rise to enterocytes. Ef-Sox9/10 probably controls the switching of mesodermal cells to the enterocyte phenotype, while Ef-Sox17 may be involved in the regulation of the initial stages of transdifferentiation.

Lung Multipotent Stem Cells of Mesenchymal Nature: Cellular Basis, Clinical Relevance, and Implications for Stem Cell Therapy

Significance: Tissue-resident stem cells are essential for normal organ homeostasis as well as for functional tissue regeneration after severe injury. Herein, mesenchymal stem cells, also designated as mesenchymal stromal cells (MSCs), contribute to the maintenance of organ integrity by their ability to replace dysfunctional cells or secrete cytokines locally and thus support the repair and healing processes of affected tissues. Recent Advances: Besides epithelial stem and progenitor cells, substantial evidence exists that tissue-resident multipotent stem cells of mesenchymal nature also exist in adult human lungs. These lung MSCs may function to regulate pulmonary tissue repair and/or regeneration, inflammation, fibrosis, and tumor formation. Critical Issues: Although therapeutically applied MSCs turned out to be a valuable therapeutic option for the prevention of lung diseases and/or the regeneration of diseased lung tissue, the true function of tissue-resident MSCs within the lung, and identification of their niche, which presumably dictates function, remain elusive. Future Directions: A detailed understanding of lung MSC localization (in the potential vascular stem cell niche) as well as of the signaling pathways controlling stem cell fate is prerequisite to unravel how (i) endogenous MSCs contribute to lung diseases, (ii) exogenous MSCs affect the proliferation of endogenous stem cells to repair damaged tissue, and (iii) a potential on-site manipulation of these cells directly within their endogenous niche could be used for therapeutic benefits. This review focuses on the central role of lung-resident MSCs, which are closely associated with the pulmonary vasculature, in a variety of chronic and acute lung diseases. Antioxid. Redox Signal. 35, 204-216.

National Heart, Lung, and Blood Institute and Building Respiratory Epithelium and Tissue for Health (BREATH) Consortium Workshop Report: Moving Forward in Lung Regeneration

The National Heart, Lung, and Blood Institute of the National Institutes of Health, together with the Longfonds BREATH consortium, convened a working group to review the field of lung regeneration and suggest avenues for future research. The meeting took place on May 22, 2019, at the American Thoracic Society 2019 conference in Dallas, Texas, United States, and brought together investigators studying lung development, adult stem-cell biology, induced pluripotent stem cells, biomaterials, and respiratory disease. The purpose of the working group was 1) to examine the present status of basic science approaches to tackling lung disease and promoting lung regeneration in patients and 2) to determine priorities for future research in the field.

Repairing damaged lungs using regenerative therapy

There is an urgent need for better treatment of lung diseases that are a major cause of morbidity and mortality worldwide. This urgency is illustrated by the current COVID-19 health crisis. Moderate-to-extensive lung injury characterizes several lung diseases, and not only therapies that reduce such lung injury are needed but also those that regenerate lung tissue and repair existing lung injury. At present, such therapies are not available, but as a result of a rapid increase in our understanding of lung development and repair, lung regenerative therapies are on the horizon. Here, we discuss existing targets for treatment, as well as novel strategies for development of pharmacological and cell therapy-based regenerative treatment for a variety of lung diseases and clinical studies. We discuss how both patient-relevant in vitro disease models using innovative culture techniques and other advanced new technologies aid in the development of pulmonary regenerative medicine.

Stem Cell-derived Respiratory Epithelial Cell Cultures as Human Disease Models

Advances in stem cell biology and the understanding of factors that determine lung stem cell self-renewal have enabled long-term in vitro culture of human lung cells derived from airway basal and alveolar type II cells. Improved capability to expand and study primary cells long term, including in clonal cultures that are recently derived from a single cell, will allow experiments that address fundamental questions about lung homeostasis and repair, as well as translational questions in asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, and lung cancer research. Here, we provide a brief history of postnatal lung epithelial cell culture and describe recent methodological advances. We further discuss the applications of primary cultures in defining "normal" epithelium, in modeling lung disease, and in future cell therapies.

Implications for Extracellular Matrix Interactions With Human Lung Basal Stem Cells in Lung Development, Disease, and Airway Modeling

The extracellular matrix (ECM) is not simply a quiescent scaffold. This three-dimensional network of extracellular macromolecules provides structural, mechanical, and biochemical support for the cells of the lung. Throughout life, the ECM forms a critical component of the pulmonary stem cell niche. Basal cells (BCs), the primary stem cells of the airways capable of differentiating to all luminal cell types, reside in close proximity to the basolateral ECM. Studying BC-ECM interactions is important for the development of therapies for chronic lung diseases in which ECM alterations are accompanied by an apparent loss of the lung's regenerative capacity. The complexity and importance of the native ECM in the regulation of BCs is highlighted as we have yet to create an in vitro culture model that is capable of supporting the long-term expansion of multipotent BCs. The interactions between the pulmonary ECM and BCs are, therefore, a vital component for understanding the mechanisms regulating BC stemness during health and disease. If we are able to replicate these interactions in airway models, we could significantly improve our ability to maintain basal cell stemness ex vivo for use in in vitro models and with prospects for cellular therapies. Furthermore, successful, and sustained airway regeneration in an aged or diseased lung by small molecules, novel compounds or via cellular therapy will rely upon both manipulation of the airway stem cells and their immediate niche within the lung. This review will focus on the current understanding of how the pulmonary ECM regulates the basal stem cell function, how this relationship changes in chronic disease, and how replicating native conditions poses challenges for ex vivo cell culture.

Intrapulmonary distal airway stem cell transplantation repairs lung injury in chronic obstructive pulmonary disease

Objectives

Chronic obstructive pulmonary disease (COPD) is characterized by irreversible lung tissue damage including chronic bronchitis and emphysema, which could further develop into respiratory failure. Many studies have revealed a potential regenerative function of the distal airway stem/progenitor cells (DASCs) after lung injury.

Materials and Methods

Mouse and human DASCs were expanded, analysed, and engrafted into injured mouse lungs. Single‐cell analyses were performed to reveal the differentiation path of the engrafted cells. Finally, human DASCs were transplanted into COPD mice induced by porcine pancreatic elastase (PPE) and lipopolysaccharide (LPS) administration.

Results

We showed that isolated mouse and human DASCs could be indefinitely expanded and were able to further differentiate into mature alveolar structures in vitro. Single‐cell analysis indicated that the engrafted cells expressed typical cellular markers of type I alveolar cells as well as the specific secreted proteins. Interestingly, transplantation of human DASCs derived from COPD patients into the lungs of NOD‐SCID mice with COPD injury repaired the tissue damage and improved the pulmonary function.

Conclusions

The findings demonstrated that functional lung structure could be reconstituted by intrapulmonary transplantation of DASCs, suggesting a potential therapeutic role of DASCs transplantation in treatment for chronic obstructive pulmonary disease.

Multi-lineage Lung Regeneration by Stem Cell Transplantation across Major Genetic Barriers

Induction of lung regeneration by transplantation of lung progenitor cells is a critical preclinical challenge. Recently, we demonstrated that robust lung regeneration can be achieved if the endogenous stem cell niches in the recipient's lung are vacated by sub-lethal pre-conditioning. However, overcoming MHC barriers is an additional requirement for clinical application of this attractive approach. We demonstrate here that durable tolerance toward mis-matched lung progenitors and their derivatives can be achieved without any chronic immune suppression, by virtue of co-transplantation with hematopoietic progenitors from the same donor. Initial proof of concept of this approach was attained by transplantation of fetal lung cells comprising both hematopoietic and non-hematopoietic progenitors. Furthermore, an even higher rate of blood and epithelial lung chimerism was attained by using adult lung cells supplemented with bone marrow hematopoietic progenitors. These results lay the foundation for repair of lung injury through a procedure akin to bone marrow transplantation.