Human Lung Stem Cells Research Articles

Abstract 859: Development of non-smoking lung cancers by indoor carcinogenic aerosols through epigenetic reprogramming of lung stem cells: Bioinformatics and artificial intelligence analysis

Abstract Several scientific studies discovered the toxic effects of indoor aerosols on different organs’ adult stem cells of the human body. The most importantly, the indoor toxic aerosols comprised of numerous carcinogens namely, sodium dodecyl sulfate, phthalic acids from floor cleaners, formaldehyde, acetaldehyde, benzene, toluene, ethyl benzene, xylenes, from air fresheners, Hydramethylnon, Pyrethrins, imiprothrin, cypermethrin, tetramethrin, prallethrin and permethrin from ant and roach Killer. However, there was a lack of analysis revealing the mechanism of toxic effects and epigenetic reprogramming of human lung stem cells and development of non-smoking lung cancers. In this study, we analyzed the toxic effects of these chemicals and the mechanism of epigenetic reprograming on lung epithelial cells using Comparative Toxico-genomics Database (CTD), database of Environmental Health Perspectives (EHP), National Institute of Environmental Health Sciences (NIEHS), Google search browser with generative artificial intelligence (AI) and other biological informatics methods (Reactome, Cytoscape PSICQUIC services, and ChEMBL database). We observed from CTD analysis that the chemical gene interactions as risk factors from indoor aerosols showed transcriptionally highly expressed of 31 common genes, by phthalic acids, sodium dodecyl sulfate, from the total of 1347 genes, 107 common genes by formaldehyde, acetaldehyde from the total of 4193 genes and all other toxic ingredients of indoor aerosols. The epigenetic mechanism of histone modifications (H3K4me3, H3K9me3, H3K27me3, H3K27ac, H3K36me3, H3K4me1, Hsa-mir-1301 of lung epithelial, and miRNAs have been revealed by NIH Roadmap Epigenomics Mapping Consortium and the lung tissue arrays were analyzed with AI and matplotlib program. The heterogenic adult stem cell reprogramming is regulated by epigenetic bivalent histone modifications at transcript starts sequences (TSS) of target genes and our current study revealed that CD44, CD80, ALDH2, ALDH3A1, ALDH3B2 are epigenetically reprogrammed with close interaction of other genes by these toxic ingredients of indoor aerosols. Therefore, our results are significant for the carcinogenic effects of indoor aerosols causing for development of lung cancer epigenetically, which may give a clue for the prevention and treatment of nonsmoking lung cancer. Citation Format: Juan Anderson, Mariah Delgado, Malcolm Lovett, Maya Saunders, Geovannie Lake, Samuel Darko, Rose M. Stiffin, Ayivi Huisso, Marilyn Sherman, Latoya Appleton, Amalya Mihnea, Swarnava Das, Mohammad M. Algahtani, Ravi Vadapalli, Biswarup Basu, Arunima Biswas, Noor Neha, Madhumita Das, Marco A. Ruiz, Mayur Doke, Jayanta K. Das. Development of non-smoking lung cancers by indoor carcinogenic aerosols through epigenetic reprogramming of lung stem cells: Bioinformatics and artificial intelligence analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 859.

Green and rapid and instrumental one-pot method for the synthesis of imidazolines having potential anti-SARS-CoV-2 main protease activity

The Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) is responsible for ongoing epidemics in humans and some other mammals and has been declared a public health emergency of international concern. In this project, several small non-peptide molecules were synthesized to inhibit the major proteinase (Mpro) of SARS-CoV-2 using rational strategies of drug design and medicinal chemistry. Mpro is a key enzyme of coronaviruses and plays an essential role in mediating viral replication and transcription in human lung epithelial and stem cells, making it an attractive drug target for SARS-CoV. The antiviral potential of imidazoline derivatives as inhibitors of (SARS-CoV-2) Mpro was evaluated using in-silico techniques such as molecular docking simulation, molecular dynamics (MD), and ADMET prediction. The docking scores of these imidazoline derivatives were compared to that of the N3 crystal inhibitor and showed that most of these compounds, particularly compound E07, interacted satisfactorily in the active site of the coronavirus and strongly interacted with the residues (Met 165, Gln 166, Met 165, His 41, and Gln 189). Furthermore, the results were confirmed by MD simulations after exposure to long-term MD simulations and ADMET predictions.

Abstract 6584: Potential carcinogenic effects of electronic nicotine delivery systems through epigenetic reprogramming in oral, brain, and lung stem cells

Abstract Recent scientific studies exhibited that the electronic nicotine delivery systems (ENDS) aerosols comprise numerous carcinogens namely propylene glycol, diacetyl, formaldehyde, acetaldehyde, crotonaldehyde (2-butenal), acetone, acetyl propionyl (2,3-pentanedione), acrolein, nicotine, arsenic, cadmium and radioisotopes, such as Polonium-210 and lead-210. However, there was no such investigation for clarifying the mechanism of carcinogenic effects and epigenetic reprogramming of human oral, brain, and lung stem cells. In this study, we investigated the carcinogenic effects of ENDS aerosols, and the mechanism of epigenetic reprogramming using the Comparative Toxico-genomics Database (CTD), NIH Toxicology Data Network (TOXNET), the database of the National Institute of Environmental Health Sciences (NIEHS), AACR Genomics Evidence Neoplasia Information Exchange (GENIE) database, and other bioinformatics databases. We found from CTD analysis that the chemical gene interactions showed approximately 3% of genes highly expressed by propylene glycol and diacetyl from a total of 98 genes. The AACR GENIE database analysis showed EGFR, is associated with gliomas (191 clinical data, DFCI glioma cohort), found among 98 genes regulated by propylene glycol and diacetyl. The CTD analysis also exhibited the chemical gene interactions of highly expressed 9 common genes (with miR140 by propylene glycol, and formaldehyde from a total of 3983 genes; 5 common genes by propylene glycol, acetaldehyde, from a total of 275 genes; 1 common gene by propylene glycol, crotonaldehyde (2-butenal), from a total of 227 genes; 7 common genes by propylene glycol, acrolein from total 2185 genes; 18 common genes by propylene glycol, and nicotine from total 1244 genes; 11 common genes by propylene glycol, and arsenic from total 4983 genes; 9 common genes with HDAC4, CD86, miR21 by propylene glycol, and cadmium from total 5242 genes. The ENDs aerosols contain Polonium-210 and lead-210 (concentration; 13 ± 2 Bq/kg), which have been reported as Group 1 human carcinogens and emit alpha particles. We found that alpha particles caused DNA lesions, and gene mutations in human oral, brain, and lung stem cells and resulted in long-term chromosomal instability in primary human T lymphocytes by analyzing recent works of literature. The epigenetic mechanisms of histone modifications and these potential carcinogens have been revealed by the database of NIH Roadmap Epigenomics Mapping Consortium and our analysis discovered that Mitogen-activated protein kinase 1(MAPK1) is epigenetically reprogrammed with close interaction of teen genes. Therefore, it is important to find the actual epigenetic mechanism of transcriptional regulation by these potential carcinogens on oral, lung, and brain stem cells, and our current study revealed this important relationship. Citation Format: Akilah Shepard, Oneilia Yearde, Juan Sanchez, Ryan Amador, Gabriel Xirinachs, Erika Hernandez, Elizabeth Corrales, Swarnava Das, Marco Ruiz, Madhumita Das, Rose M. Stiffin, Marilyn Sherman, Alessandra Manzon, Ayivi Huisso, Jayanta K. Das. Potential carcinogenic effects of electronic nicotine delivery systems through epigenetic reprogramming in oral, brain, and lung stem cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6584.

NOTCH inhibition promotes bronchial stem cell renewal and epithelial barrier integrity after irradiation.

Hyperactivity of the NOTCH pathway is associated with tumor growth and radiotherapy resistance in lung cancer, and NOTCH/γ‐secretase inhibitors (GSIs) are a potential therapeutic target. The therapeutic outcome, however, is often restricted by the dose‐limiting toxicity of combined treatments on the surrounding healthy tissue. The NOTCH signaling pathway is also crucial for homeostasis and repair of the normal airway epithelium. The effects of NOTCH/γ‐secretase inhibition on the irradiation of normal lung epithelium are unknown and may counteract antitumor activity. Here we, therefore, investigated whether normal tissue toxicity to radiation is altered upon NOTCH pathway inhibition. We established air‐liquid interface pseudostratified and polarized cultures from primary human bronchial epithelial cells and blocked NOTCH signaling alone or after irradiation with small‐molecule NOTCH inhibitor/GSI. We found that the reduction in proliferation and viability of bronchial stem cells (TP63+) in response to irradiation is rescued with concomitant NOTCH inhibition. This correlated with reduced activation of the DNA damage response and accelerated repair by 24 hours and 3 days postirradiation. The increase in basal cell proliferation and viability in GSI‐treated and irradiated cultures resulted in an improved epithelial barrier function. Comparable results were obtained after in vivo irradiation, where the combination of NOTCH inhibition and irradiation increased the percentage of stem cells and ciliated cells ex vivo. These encourage further use of normal patient tissue for toxicity screening of combination treatments and disclose novel interactions between NOTCH inhibition and radiotherapy and opportunities for tissue repair after radiotherapy.

Retraction: Kajstura J et al. Evidence for Human Lung Stem Cells. N Engl J Med 2011;364:1795-806.

We have been contacted by several authors of the article by Kajstura J et al., Evidence for Human Lung Stem Cells, N Engl J Med 2011;364:1795-1806.1 An investigation by Harvard Medical School and Brigham and Women’s Hospital has determined that some of the images in the article were manipulated. The authors tell us that “a review of the original data affirms this conclusion and has led us to conclude that we no longer have faith in the veracity of these images. As we were not aware of this manipulation of the data until long after the paper had been published, .

PO-107 Notch signalling pathway is required for proliferation, repair and differentiation of primary human lung stem cells upon irradiation

IntroductionLung cancer is the leading cause of cancer death in western countries. While significant progress has been made in terms of treatment, radiotherapy is limited by dose-limiting side-effects. Reducing side-effects may improve tumour control by dose-escalation and treatment-time. The NOTCH signalling pathway plays an important role in differentiation of the airway epithelium and its deregulation is associated with lung cancer. However, the mechanism by which NOTCH inhibition integrates with airway repair is unknown. What is currently lacking are primary human lung tissue models that enable robust evaluation of the effects of treatment which can guide the selection of combination treatments for lung cancer.Material and methodsWe therefore investigated the effects of inhibiting NOTCH in human basal stem cells from normal primary bronchial epithelial cells isolated from lung cancer patients undergoing lobectomy. Basal stem cells isolated from 3 different patients were treated with the pan NOTCH inhibitor (DBZ) and irradiated with 2–4 Gy. Incucyte experiment, Edu/PI staining and clonogenic assay were used to evaluate proliferation and clonal capacity. To evaluate DNA damage response 53 bp1 staining was performed. To study Notch inhibition in basal cells differentiation the tracheal epithelium of 2–5 Gy irradiated mice was seeded in ALI system and confocal stainings were performed.Results and discussionsIncucyte experiment revealed a reduced proliferation of stem cells upon NOTCH inhibition which is further reduced upon irradiation. NOTCH inhibition induces accumulation of the cells in GO-G1 phase and a significant reduction in S phase which was exacerbated upon irradiation. The reduction in proliferation also led to a reduction in long term survival. We observed activation of the DNA damage response pathway by expression of pCHK2, pATM upon NOTCH inhibition which was enhanced by radiation. 53 BP1 foci 24 hours after RT was higher when NOTCH was inhibited demonstrating that NOTCH is required for the DNA damage response. In cultured primary stem cells from irradiated murine tracheas NOTCH inhibition induced a fate change by blocking mucous differentiation and inducing cillilary differentiation and enhancing progenitor p63 +cells. However, overall proliferation was reduced.ConclusionNOTCH pathway is needed for stem cell survival and DNA damage response upon irradiation of undifferentiated progenitors. These studies underscore the importance of studying the effect of targeted anti-cancer drugs for normal tissue effects.

Stem cell therapies for chronic obstructive pulmonary disease: current status of pre-clinical studies and clinical trials.

Chronic obstructive pulmonary disease (COPD) is a respiratory disease that has a major impact worldwide. The currently-available drugs mainly focus on relieving the symptoms of COPD patients. Novel regenerative therapeutic approaches have been investigated with the aim of repairing or replacing the injured functional structures of the respiratory system. We summarized the progress made by regenerative therapies for COPD by analyzing results from both pre-clinical studies and completed clinical trials. These approaches include the application of exogenous stem cells or small molecules to stimulate the regeneration by endogenous lung stem/progenitor cells. Exogenous mesenchymal stem cells (MSCs) have been reported to repair the structure and improve the function of the injured respiratory system in COPD models. However, the studies that used MSCs in patients with moderate-to-severe COPD patients did not lead to clear respiratory functional improvements. Exogenous human lung stem cells applied to cryo-injured (CI) lungs of mice have been shown to organize into human-like pulmonary structures, indicating a new property of stem cells that is potentially capable of curing COPD patients. Small molecules like retinoic acid has been shown to lead to regeneration and repair of the damaged lung structures in COPD mouse models probably by activation of endogenous lung stem/progenitor cells. However, retinoic acid or agonists of retinoic acid receptor administered to moderate or severe COPD patients did not improve the density and function of the damaged lung. These novel regenerative approaches have failed in preliminary clinical trials, possibly due to the advanced severity of the disease. Further work should be done to develop the current regenerative approaches for curing patients at different stages of COPD. We suggest that some modifications of the approach in the clinical studies may lead to more successful outcomes of regenerative therapy for COPD.

Stem Cell Therapy for COPD: Where are we?

Over the last year I have had several patients ask me about stem cell therapy for chronic obstructive pulmonary disease (COPD). There are clinics currently offering this therapy, (typically at exorbitant out of pocket cost to the patient), even though there are no phase III randomized controlled trials or Food and Drug Administration approval. There have been several phase I clinical trials, mostly looking at safety, and a handful of small phase II clinical trials that essentially have been negative. Despite this, there remains keen interest in continuing to study so-called “regenerative therapy” for COPD. Indeed, current standard therapies including bronchodilators and inhaled corticosteroids and the phosphodiesterase-4 inhibitor, roflumilast, show modest efficacy at best in reducing exacerbations and improving lung function. There has been no definitive evidence that they impact mortality. Lung volume reduction surgery is reserved often for those with severe disease and has only modest benefits. Lung transplantation is limited by availability, age restrictions, complications and rejection issues. With these limitations of standard modalities of therapy, it is attractive to pursue novel regenerative therapies that may be capable of restoring pulmonary function and structures such as airways, terminal bronchioles and alveoli. It is also postulated that by replacing these damaged cells there can be a restoration of normal immune function and a reduction in the inflammatory response to variable exposures such as cigarette smoke, air pollution and airway pathogens in susceptible individuals who develop COPD. Stem cells can differentiate into several different lung cell types such as the alveolar epithelial cells that are destroyed by cigarette smoke leading to emphysematous changes and reduced tethering of small airways causing hyperinflation and gas exchange abnormalities. Pre-clinical trials in animal models have suggested regeneration of alveolar-like structures, repair of emphysematous lungs, and reduction of inflammatory responses. The greatest success has been in acute lung injury models, however. Currently, regenerative therapies are divided into extrinsic therapeutic strategies and intrinsic cell therapy methods. There has been some work looking at the potential to bioengineer fully intact 3-D lung units that could be transplanted but this is not a likely prospect for the near future. Extrinsic cell therapy refers to infusing (or endotracheal installation) of stem cells including embryonic stem cells (ESCs), induced pleuripotent stem cells (iPSs), mesenchymal stem cells (MSCs), and human lung stem cells (hLSCs). Intrinsic therapy refers to the delivery of small molecules (retinoid compounds have been the most studied) that can stimulate the endogenous lung stem/progenitor cells to regenerate and replace damaged structures (See Sun et al review paper below). As mentioned above, human trials to date have largely failed in showing any benefit but there remain questions about appropriate candidates for such therapy, type of therapy, timing of therapy, dosing issues and a host of other variables that require further study. One of the salient questions is whether these therapies need to be started earlier in less severe stages of the disease process. Of course, if that is found to be the case then a major issue will be whether early identification, smoking cessation, adherence to conventional treatments and addressing comorbid conditions may be as or more effective. The papers presented in this Journal Club include an excellent, comprehensive state of the art review of the studies to date and the important future lines of research. The other recent papers address some of the questions raised in the review article. Note: Abstracts are presented in their original, published format and have not been edited to match JCOPDF style.

Development of a genetically modifiable epithelial in-vitro culture system from human embryonic lung epithelial stem cells: towards human lung regeneration in end-stage respiratory failure

BackgroundRegeneration of healthy lung tissue in patients with end-stage respiratory disease would cure disease. Therefore, a detailed understanding of lung development is needed. The most important epithelial stem-cell population in developing lungs is found in distal branching tips, and these Sox9+ lung epithelial stem cells (LESCs) generate all epithelial lineages. Our objective was to develop a self-renewing, genetically modifiable epithelial in-vitro culture system from human embryonic LESCs. MethodsHuman embryonic LESCs were characterised using genome-wide transcriptional analysis (RNA-seq, Illumina, San Diego, CA, USA) and immunohistochemistry at 5–20 weeks postconception. LESCs were microdissected, and self-renewing expansion in three-dimensional (3D) organoid culture was established empirically. We assessed similarity between cultured and fresh LESCs via RNA-seq and immunohistochemistry. Organoids were differentiated in vitro, or in vivo by xenotransplantation into bleomycin-injured mouse lungs or kidney capsule. SOX9 was deleted with CRISPR–Cas9. FindingsRNA-seq of LESCs identified broad-scale transcriptional differences between mouse and human embryonic lung stem cells. Human LESCs were successfully expanded for more than 10 months as karyotypically stable 3D organoids using a combination of seven signalling molecules. The LESC stem-cell markers, transcriptome, and organoid morphology were maintained throughout the culture period. Bronchiolar and alveolar differentiation was achieved in vitro and in vivo. Moreover, xenotransplantation of organoids into bleomycin-injured adult mouse lungs was extremely efficient. Knocking out SOX9 led to a loss-of-self-renewing phenotype. InterpretationOur novel genetically modifiable human embryonic lung culture system enables for the first time, to our knowledge, the in-vitro study of human lung development and disease. We anticipate that this system will transform lung regenerative medicine by guiding development of improved protocols for induced pluripotent stem-cell differentiation and adult stem-cell manipulation in vivo, benefiting patients with end-stage respiratory disease. Furthermore, our lung injury–xenotransplantation protocol provides the first method for efficient future cell therapy. FundingWellcome Trust (PhD programme for clinicians), Medical Research Council, Addenbrooke's Charitable Trust.

Stem/progenitor cells in endogenous repairing responses: new toolbox for the treatment of acute lung injury.

The repair of organs and tissues has stepped into a prospective era of regenerative medicine. However, basic research and clinical practice in the lung regeneration remains crawling. Owing to the complicated three dimensional structures and above 40 types of pulmonary cells, the regeneration of lung tissues becomes a great challenge. Compelling evidence has showed that distinct populations of intrapulmonary and extrapulmonary stem/progenitor cells can regenerate epithelia as well as endothelia in various parts of the respiratory tract. Recently, the discovery of human lung stem cells and their relevant studies has opened the door of hope again, which might put us on the path to repair our injured body parts, lungs on demand. Herein, we emphasized the role of endogenous and exogenous stem/progenitor cells in lungs as well as artificial tissue repair for the injured lungs, which constitute a marvelous toolbox for the treatment of acute lung injury. Finally, we further discussed the potential problems in the pulmonary remodeling and regeneration.

A paracrine network regulates the cross-talk between human lung stem cells and the stroma

The signals that regulate stem cell self-renewal and differentiation in the lung remain elusive. Lung stem cells undergo self-renewal or lineage commitment to replenish tissue, depending on cross-talk with their environment. This environment, also known as the niche, includes mesenchymal and endothelial tissues. Here we define molecular mechanisms involved in the interaction between human lung Lgr6+ stem cells (LSCs) and fibroblasts in a functional microenvironment. We reveal a central role for p38α MAPK in establishing and maintaining such cross-talk, acting in both cell types. In LSCs, p38α induces the expression of SDF-1, which activates the stroma. p38α is essential for fibroblast activation and induction of cytokine expression, in particular TNFα. This paracrine network induces a hierarchical activation leading to the recruitment of endothelium, establishing a functional microenvironment. Disruption of this cross-talk abrogates proper LSC differentiation in vivo and may lead to lung dysfunction and disease.

Isolation of Cancer Stem Like Cells from Human Adenosquamous Carcinoma of the Lung Supports a Monoclonal Origin from a Multipotential Tissue Stem Cell

There is increasing evidence that many solid tumors are hierarchically organized with the bulk tumor cells having limited replication potential, but are sustained by a stem-like cell that perpetuates the tumor. These cancer stem cells have been hypothesized to originate from transformation of adult tissue stem cells, or through re-acquisition of stem-like properties by progenitor cells. Adenosquamous carcinoma (ASC) is an aggressive type of lung cancer that contains a mixture of cells with squamous (cytokeratin 5+) and adenocarcinoma (cytokeratin 7+) phenotypes. The origin of these mixtures is unclear as squamous carcinomas are thought to arise from basal cells in the upper respiratory tract while adenocarcinomas are believed to form from stem cells in the bronchial alveolar junction. We have isolated and characterized cancer stem-like populations from ASC through application of selective defined culture medium initially used to grow human lung stem cells. Homogeneous cells selected from ASC tumor specimens were stably expanded in vitro. Primary xenografts and metastatic lesions derived from these cells in NSG mice fully recapitulate both the adenocarcinoma and squamous features of the patient tumor. Interestingly, while the CSLC all co-expressed cytokeratins 5 and 7, most xenograft cells expressed either one, or neither, with <10% remaining double positive. We also demonstrated the potential of the CSLC to differentiate to multi-lineage structures with branching lung morphology expressing bronchial, alveolar and neuroendocrine markers in vitro. Taken together the properties of these ASC-derived CSLC suggests that ASC may arise from a primitive lung stem cell distinct from the bronchial-alveolar or basal stem cells.

Regulation of human lung alveolar multipotent cells by a novel p38α MAPK/miR-17-92 axis

The cellular and molecular mechanisms that control lung homeostasis and regeneration are still poorly understood. It has been proposed that a population of cells exists in the mouse lung with the potential to differentiate into all major lung bronchioalveolar epithelium cell types in homeostasis or in response to virus infection. A new population of E-Cad/Lgr6(+) putative stem cells has been isolated, and indefinitely expanded from human lungs, harbouring both, self-renewal capacity and the potency to differentiate in vitro and in vivo. Recently, a putative population of human lung stem cells has been proposed as being c-Kit(+). Unlike Integrin-α6(+) or c-Kit(+) cells, E-Cad/Lgr6(+) single-cell injections in the kidney capsule produce differentiated bronchioalveolar tissue, while retaining self-renewal, as they can undergo serial transplantations under the kidney capsule or in the lung. In addition, a signalling network involving the p38α pathway, the activation of p53 and the regulation of the miR-17-92 cluster has been identified. Disruption of the proper cross-regulation of this signalling axis might be involved in the promotion of human lung diseases.

Mesenchymal stem cells and the stem cell niche: a new chapter

BONE MARROW-DERIVED mesenchymal stem/stromal cells (MSCs) are self-renewing multipotent cells with therapeutic effects in diverse models of tissue injury (27). In the rodent lung, MSCs reduce collagen deposition in the bleomycin model of pulmonary fibrosis (26) and reduce lung injury and improve survival following intrapulmonary delivery of endotoxin or Escherichia coli (10, 11) and following severe gram-negative peritonitis (18). In the hyperoxia model of bronchopulmonary dysplasia, exposure to high concentrations of oxygen during early postnatal life in rats and mice causes simplification of alveolar and lung capillary structure and reduced pulmonary capillary surface area, leading to pulmonary hypertension. Two groups reported simultaneously in 2009 that MSCs given by airway to rats (12) or by blood to mice (2) during prolonged hyperoxia in early postnatal life prevented arrested alveolar growth. However, engraftment of MSCs during hyperoxia and in other models has not accounted for the therapeutic effects, thus prompting a search for other mechanisms. MSCs are potent immunomodulators, suppressing several functions of lymphocytes, natural killer cells, and monocytes (1), and reduce inflammatory cell lung infiltrates and cytokines during sepsis and acute lung injury (11, 23, 25). In addition, MSCs have direct antibacterial effects (19), secrete epithelial growth factors (21), and can rescue epithelial cellular bioenergetics with mitochondrial transfer (14). MSCs and the Stem Cell Niche

Human Lung Stem Cells: Has the Future Arrived?

An intriguing paper was recently published that describes c-kit-positive human lung stem cells that self-renew and differentiate into multiple lineages. While these findings are potentially therapeutically exciting, several questions remain to be answered. We review the paper and the issues that have arisen.

Research Spotlight

Research Spotlight

Evidence for Human Lung Stem Cells

BACKGROUND Although progenitor cells have been described in distinct anatomical regions of the lung, description of resident stem cells has remained elusive. METHODS Surgical lung-tissue specimens were studied in situ to identify and characterize human lung stem cells. We defined their phenotype and functional properties in vitro and in vivo. RESULTS Human lungs contain undifferentiated human lung stem cells nested in niches in the distal airways. These cells are self-renewing, clonogenic, and multipotent in vitro. After injection into damaged mouse lung in vivo, human lung stem cells form human bronchioles, alveoli, and pulmonary vessels integrated structurally and functionally with the damaged organ. The formation of a chimeric lung was confirmed by detection of human transcripts for epithelial and vascular genes. In addition, the self-renewal and long-term proliferation of human lung stem cells was shown in serial-transplantation assays. CONCLUSIONS Human lungs contain identifiable stem cells. In animal models, these cells participate in tissue homeostasis and regeneration. They have the undemonstrated potential to promote tissue restoration in patients with lung disease. (Funded by the National Institutes of Health.).

Evidence for human lung stem cells.

Evidence for human lung stem cells.

Human Cardiac Stem Cells

The view of the heart as a static organ implies that myocyte death and formation play a negligible role in cardiac homeostasis. Although stem cells have been unexpectedly identified in several organs, including the brain, kidney, lung, and skeletal muscle, the search for a cardiac stem cell (CSC) has been perceived as a futile effort, given the acknowledged lack of regenerative potential of the myocardium. Nevertheless, in the past several years, the demonstration of myocyte renewal in the normal and diseased heart has revealed a new, dynamic, and lively picture of this organ. Components of the cell cycle machinery and markers of cell replication have been detected in cardiomyocytes. The demonstration that karyokinesis and cytokinesis involve cells expressing contractile proteins has provided evidence that cardiomyocyte division occurs in the adult heart.1 More recently, pulse-chase assays with thymidine analogs,2 lineage tracing protocols,3 and 14C birth dating of cells4 have shown the existence of myocyte turnover, a process that has been found to differ in magnitude according to the methods used for its documentation and quantification. Article see p 2559 Over the years, the heart has provided us with the evidence that solves the critical problem of the origin of cardiomyocytes. At this moment in time, paraphrasing Eugenio Montale, we could say that the human heart is “on the verge of betraying [its] final secret offering the opportunity to uncover…the still point of the world, the link that won't hold, the thread to untangle that will finally lead to the heart of a truth.”5 Newly generated myocytes may derive from division of preexisting parenchymal cells or from activation and differentiation of resident CSCs. Discriminating between these two possibilities is not an easy task. Fate-mapping strategies, which are commonly used to track the origin of cells and …

Immortalization of human small airway epithelial cells with characteristics of bronchioalveolar stem cells

Most of our current understanding of stem cells in the adult lung is based on mouse models while information in the human lung remains poorly defined. A major advance would be the ability to reproducibly grow human lung stem or progenitor cells to allow their systematic study and genetic manipulation. Toward this goal, we have worked out conditions to routinely immortalized (NB = 9) human small airway epithelial cells (HSAECs) from peripheral lung using Cdk4 and hTERT expression vectors in these cells. As an example strain HSAEC1 grows in serum free SAGM medium (Clonetics), forms colonies in liquid media efficiently, but does not form colonies in soft agar or tumors in SCID/NOD mice. HSAEC1 expresses lung basal/stem cell markers (aldehyde dehydrogenase, p63, Cytokeratin14 and 17, and is resistant to 1 mM naphthalene) but very low or undetectable Clara cell, Type1 and Type2 cell markers in SAGM, which are then expressed when grown in Matrigel culture or in serum. Finally, the cells can be genetically manipulated toward oncogenesis (with KRASV12, and or missense p53). We conclude, that we have prepared multiple, immortalized strains of human peripheral lung epithelial cells with many characteristics of lung stem or progenitor cells that are experimentally tractable for studying lung differentiation and tumorigenesis.This work is supported by NCI SPORE P50CA70907, and NASA/DOE NSCOR NNJ05HD36G, DE‐AI02‐05ER64068