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Characterization and neural differentiation of fetal lung mesenchymal stem cells.

Mesenchymal stem cells (MSCs) have been successfully isolated from a broad range of adult, fetal, and other nonembryonic tissues. Fetal lung has been identified as a rich source of MSCs. However, the biological characteristics and differentiation potential of fetal lung MSCs remain to be explored. In this study, we established a series of methods for isolation and expansion of fetal lung MSCs. These MSCs could withstand more than 40 passages without obvious decline in proliferation ability, significant changes in morphology, and expression of cell markers. Flow cytometric analysis showed that fetal lung MSCs expressed CD13, CD29, CD44, CD90, CD105, CD166, and HLA-ABC, but not CD14, CD31, CD34, CD38, CD41a, CD42b, CD45, CD49d, CD61, CD106, CD133, and HLA-DR. Cell cycle analysis revealed that when the MSCs reached their log phase of growth, more than 90% of the cells were in G0/G1 phase while the proportion of cells in S phase and G2/M phase were about 5.56% and 2.08% cells, respectively. These MSCs could differentiate into neural cells in addition to their mesenchymal differentiation potential. Our data suggest that the fetal lung MSC population is an alternative source of stem cells for cell-based therapy of neurological defects or mesenchymal-originating diseases.

Adipocytes↗

Acute lung injury after allogeneic stem cell transplantation: is the lung a target of acute graft-versus-host disease?

Allogeneic hematopoietic stem cell transplantation (SCT) is an important therapeutic option for a number of malignant and nonmalignant conditions but the broader application of this treatment strategy is limited by several side effects. In particular, diffuse lung injury is a major complication of SCT that responds poorly to standard therapeutic approaches and significantly contributes to transplant-related morbidity and mortality. Historically, approximately 50% of all pneumonias seen after SCT have been secondary to infection, but the judicious use of broad-spectrum antimicrobial prophylaxis in recent years has tipped the balance of pulmonary complications from infectious to noninfectious causes. This mini review will discuss the definition, risk factors and pathogeneses of noninfectious lung injury that occurs early after allogeneic SCT.

Anti-Bacterial Agents↗

Wnt signaling in stem cells and non-small-cell lung cancer.

Evidence suggests that stem cells may be the source of mutant cells that cause cancers to develop and proliferate. Wnt signaling has been shown to promote self-renewal in gut epithelial and hematopoietic stem cells and to trigger critical pathways in carcinogenesis. In this review, we highlight the progress in understanding how the Wnt pathway contributes to stem cell maintenance and its role in lung carcinogenesis. Although the function of stem cells in solid tumor development is unclear, the Wnt pathway's role in determining the fate and self-renewal potential of cancer stem cells suggests a critical role in carcinogenesis and that developing drugs to inhibit this pathway may be of therapeutic interest.

Carcinoma, Non-Small-Cell Lung↗

Investigating stem cells in the lung.

Disruption of the lung architecture by genetic events, environmental insults, or transformation can lead to respiratory diseases such as acute respiratory distress syndrome and lung cancer. Identification of the stem cells of the lung and the processes by which they regulate homeostasis may lead to better targets for treatment of these diseases. There are a number of approaches to study stem cell biology. Development of the lung and the major pulmonary cells of the bronchioles and alveolar regions of the lung is discussed in this review. Likewise, identifying the proteins that are critical for cell-specific expression and differentiation may identify approaches for manipulation of gene expression for use as therapy or treatment of lung diseases. Furthermore, strategies for studying stem cells in the lung are addressed by using the mouse as a model system. Gaining a more detailed understanding of the stem cells of the lung may provide new insight into the processes that govern lung biology and may lead to better treatments for lung diseases. Enthusiasm for the use of exogenous stem cells to replace tissue, organs, or other defective or deficient cells is boundless. Before stem cells can be used indiscriminately for these purposes, understanding tissue genetics and immunology is essential. Progress has been made in these areas for pulmonary disease. Attention to these models will be applicable to other organs and diseases.

Animals↗

Stem cells in the lung parenchyma and prospects for lung injury therapy.

Until recently, it was thought that only embryonic stem cells were pluripotent and that adult stem cells were restricted in their differentiative and regenerative potential to become the tissues in which they reside. However, the discovery that adult stem cells in one tissue can contribute to the formation of other tissues, especially after injury or cell damage, implies that stem cells have developmental plasticity. For example, haematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) from bone marrow can be used to regenerate diverse tissues at distant sites, including the lung. This article reviews the character of stem cells in the lung parenchyma and focuses on the potential uses of adult stem cells in research of lung injury and lung disease therapies.

Cell Differentiation↗

Up- and down-regulation by glucocorticoids of the constitutive expression of the mast cell growth factor stem cell factor by human lung fibroblasts in culture.

Stem cell factor (SCF) is a major mast cell growth factor that promotes differentiation and chemotaxis of mast cells and inhibits their apoptosis. SCF therefore may be involved in diseases associated with an increased number of tissue mast cells such as asthma, for which the major treatment is glucocorticoids. In this study, we evaluated the effect of the glucocorticoid budesonide on the constitutive expression of SCF by human lung fibroblasts in primary culture. Budesonide (0.1 microM) induced a time-dependent biphasic effect on SCF mRNA and protein production. A short treatment (2.5-10 hr) induced an inhibition of SCF protein accumulation (-58% at 2.5 hr) and mRNA expression (-69% at 2.5 hr), associated with an accelerated decay of SCF mRNA and with a decrease in SCF gene transcription observed by nuclear run-on assay. Longer treatment (24-72 hr) led to increases in SCF protein accumulation (+64% at 48 hr) and mRNA expression (+125% at 24 hr) as a consequence of transcriptional activation. Similar effects of a decrease followed by an increase in SCF production were observed using another glucocorticoid, dexamethasone. Overall, our results show that glucocorticoids potently regulate SCF expression in human lung fibroblasts, successively decreasing and increasing SCF mRNA levels according to treatment duration. Such time-dependent modulation of SCF levels may explain some current discrepant findings about the effects of glucocorticoids on SCF production and may have functional consequences during glucocorticoid treatment, such as asthma therapy.

Budesonide↗

Identification of bronchioalveolar stem cells in normal lung and lung cancer.

Injury models have suggested that the lung contains anatomically and functionally distinct epithelial stem cell populations. We have isolated such a regional pulmonary stem cell population, termed bronchioalveolar stem cells (BASCs). Identified at the bronchioalveolar duct junction, BASCs were resistant to bronchiolar and alveolar damage and proliferated during epithelial cell renewal in vivo. BASCs exhibited self-renewal and were multipotent in clonal assays, highlighting their stem cell properties. Furthermore, BASCs expanded in response to oncogenic K-ras in culture and in precursors of lung tumors in vivo. These data support the hypothesis that BASCs are a stem cell population that maintains the bronchiolar Clara cells and alveolar cells of the distal lung and that their transformed counterparts give rise to adenocarcinoma. Although bronchiolar cells and alveolar cells are proposed to be the precursor cells of adenocarcinoma, this work points to BASCs as the putative cells of origin for this subtype of lung cancer.

Adenocarcinoma, Bronchiolo-Alveolar↗

Stem cells and repair of lung injuries.

Fueled by the promise of regenerative medicine, currently there is unprecedented interest in stem cells. Furthermore, there have been revolutionary, but somewhat controversial, advances in our understanding of stem cell biology. Stem cells likely play key roles in the repair of diverse lung injuries. However, due to very low rates of cellular proliferation in vivo in the normal steady state, cellular and architectural complexity of the respiratory tract, and the lack of an intensive research effort, lung stem cells remain poorly understood compared to those in other major organ systems. In the present review, we concisely explore the conceptual framework of stem cell biology and recent advances pertinent to the lungs. We illustrate lung diseases in which manipulation of stem cells may be physiologically significant and highlight the challenges facing stem cell-related therapy in the lung.

Animals↗

Stem cells in the lung.

The lung is composed of two major anatomically distinct regions-the conducting airways and gas-exchanging airspaces. From a cell biology standpoint, the conducting airways can be further divided into two major compartments, the tracheobronchial and bronchiolar airways, while the alveolar regions of the lung make up the gas-exchanging airspaces. Each of these regions consists of distinct epithelial cell types with unique cellular physiologies and stem cell compartments. This chapter focuses on model systems with which to study stem cells in the adult tracheobronchial airways, also referred to as the proximal airway of the lung. Important in such models is an appreciation for the diversity of stem cell niches in the conducting airways that provide localized environmental signals to both maintain and mobilize stem cells in the setting of airway injury and normal cellular turnover. Because cellular turnover in airways is relatively slow, methods for analysis of stem cells in vivo have required prior injury to the lung. In contrast, ex vivo and in vitro models for analysis of airway stem cells have used genetic markers to track lineage relationships together with reconstitution systems that mimic airway biology. Over the past decades, several widely acceptable methods have been developed and used in the characterization of adult airway stem/progenitor cells. These include localization of label-retaining cells (LRCs), retroviral tagging of epithelial cells seeded into xenografts, air-liquid interface cultures to track clonal proliferative potential, and multiple transgenic mouse models. This chapter reviews the biologic context and use of these models while providing detailed methods for several of the more broadly useful models for studying adult airway stem/progenitor cell types.

Adult Stem Cells↗

Comparison of lung function after myeloablative and 2 Gy of total body irradiation-based regimens for hematopoietic stem cell transplantation.

Lung function decline is a well-recognized occurrence after myeloablative hematopoietic stem cell transplantation (HCT) that has not been studied after nonmyeloablative conditioning regimens. We examined the lung function of patients before and after 2-Gy total body irradiation-based nonmyeloablative and myeloablative preparative regimens. Before HCT, at day 100, and 1 year after HCT, nonmyeloablative patients had lower 1-second forced expiratory volume (FEV1), forced vital capacity, total lung capacity, residual volume, and carbon monoxide diffusion capacity. However, after transplantation, the risk for experiencing a >20% per year decrease of FEV 1 was significantly lower for nonmyeloablative than myeloablative patients >50 years of age (odds ratio, 0.3; 95% confidence interval, 0.1-0.8; P = .01). Lower pretransplantation FEV 1 was associated with a higher mortality rate for both groups, with the highest mortality risk among patients with a pretransplantation FEV 1 <60% (nonmyeloablative: hazard ratio, 3.9; 95% confidence interval, 1.9-8.0; myeloablative: hazard ratio, 7.2; 95% confidence interval, 2.5-21.2). These results suggest that despite having worse lung function, patients who receive the 2-Gy total body irradiation-based nonmyeloablative regimen will likely experience less pulmonary toxicity than patients who receive a myeloablative regimen, and this may have important clinical implications when deciding on a conditioning regimen for patients >50 years of age with compromised pretransplantation lung function.

Adult↗

Functional facets of the pulmonary neuroendocrine system.

Pulmonary neuroendocrine cells (PNECs) have been around for 60 years in the scientific literature, although phylogenetically they are ancient. Their traditionally ascribed functions include chemoreception and regulation of lung maturation and growth. There is recent evidence that neuroendocrine (NE) differentiation in the lung is regulated by genes and pathways that are conserved in the development of the nervous system from Drosophila to humans (such as achaete-scute homolog-1), or implicated in the carcinogenesis of the nervous or NE system (such as the retinoblastoma tumor suppressor gene). In addition, complex neural networks are in place to regulate chemosensory and other functions. Even solitary PNECs appear to be innervated. For the first time ever, we have mouse models for lung NE carcinomas, including the most common and virulent small cell lung carcinoma. Moreover, PNECs may be important for inflammatory responses, and pivotal for lung stem cell niches. These discoveries signify an exciting new era for PNECs and are likely to have therapeutic and diagnostic applications.

Animals↗

Posttransplant lymphoproliferative disorder of the lung in a renal transplant recipient treated successfully with surgery.

Posttransplant lymphoproliferative disorders (PTLDs) are a heterogeneous group of lymphoid diseases that occur after solid organ and bone marrow transplantation. Lung-located PTLD has been reported in recipients of the heart, cord blood stem cells, lungs, and bone marrow transplants, but only four cases were reported previously after kidney transplantation. Thoracic location of PTLD must be regarded as an especially dangerous complication. The pathogenesis, and clinical and histological features of PTLD remain poorly defined but predisposing risk factors are becoming better understood. Namely, Epstein-Barr virus (EBV) and immunosuppressive agents appear to be such risk factors. There has been marginal success in treating PTLD using a number of treatment modalities, including combination chemotherapy with anti-CD20 or high-dose chemotherapy with stem cell rescue. We report a renal allograft recipient transplanted in March 2000, diagnosed with EBV-associated and lung-located PTLD. His initial immunosuppression consisted of tacrolimus, azathioprine, and steroids. Azathioprine was withdrawn in September 2001. In November 2001 a high-resolution computed tomography scan revealed two round masses in the right lung. The patient underwent right thoracotomy and resection of the lower and middle lobe. The diagnosis of PTLD was settled by intraoperative histopathological evaluation. The postoperative histological assessment confirmed the diagnosis and revealed positive staining for EBV. The patient remained in complete remission for 3 years with a well-functioning renal allograft, with current serum creatinine of 1.2 mg%. This case illustrates that the treatment of lung-located PTLD may be successful, but it depends on a combination of prompt diagnosis, reduction of immunosuppression, and of course surgery.

Aged↗

Adult bone marrow-derived stem cells for the lung: implications for pediatric lung diseases.

Bronchopulmonary dysplasia (BPD) and cystic fibrosis (CF) are two common serious chronic respiratory disorders without specific treatments affecting children. BPD is characterized by an arrest in alveolar growth in premature infants requiring respiratory support. CF is the most common fatal inherited genetic disorder characterized by abnormally thick mucus secretions, recurrent infection and ultimately lung destruction. One commonality between these two diseases is the promise of utilizing stem cells therapeutically. Indeed, the use of exogenous cells to supplement the natural repair mechanisms or the possibility of genetic manipulation in vitro before administration are appealing therapeutic options for these diseases. Increasing attention has been focused on the use of adult bone marrow-derived stem cells (BMSC) to regenerate damaged organs such as the heart, the brain, and the liver. However, due to the lung's complexity as well as the low rate of cellular turnover within the lung, progress has been slower in this area compared with the skin or liver. Initial work suggests that BMSC can engraft and differentiate into a variety of lung cells, but these findings have been challenged recently. This article critically reviews the current advances on the therapeutic use of stem cells for lung regeneration.

Adult↗

Detection of small cell lung cancer bone marrow metastases by tumor stem cell assay.

Detection of small cell lung cancer (SCLC) bone marrow (BM) metastases has a prognostic implication in itself and a therapeutic interest in the setting of autologous bone marrow transplantation. In a prospective study involving 68 bone marrow samples, we compared SCLC detection results obtained using a tumor stem cell assay and those obtained using conventional morphology by light microscopy. In agar, tumoral cells were stimulated either by Salmon's conditioned medium or by epidermal growth factor (EGF). Tumoral clonogeneic cells were detected in 11 cases, although 7 of these were considered negative when investigated by light microscopy. On the contrary, metastases were detected by morphology in 8 instances where no growing colonies were revealed by tumor stem cell assay. The choice of stimulating factor did not seem critical since the number of colonies was similar in all the cases. We conclude that the tumor stem cell assay is useful in the detection of small cell lung cancer bone marrow metastases, particularly in cases where these metastases have failed to be recognized through light microscopy investigation. However, the sensitivity of this assay is low and should be complemented by other techniques such as immunodetection.

Bone Marrow Cells↗

Modulation of immunological histamine release from human lung fragments by stem cell factor, IL-3, IL-5 and GM-CSF: comparison with human leukocytes.

Because of the importance of cytokines in the regulation of allergic inflammation, we investigated the effects of SCF, IL-3, IL-5 and GM-CSF on immunological histamine release from sensitized human lung fragments as well as human leukocytes. SCF (0.2-20 ng/ml) caused a concentration-related enhancement of anti-IgE (1/100) induced histamine release from lung fragments reaching maximally 64% at 20 ng/ml. In contrast, enhancement produced by IL-5, IL-3 and GM-CSF (0.2-20 ng/ml) was quite marginal and reached at best around 20% at the higher concentration, IL-5 being slightly more effective than IL-3 and GM-CSF. Further, SCF potentiated histamine release whatever the level of immunological control whereas potentiation by IL-5 primarily occurred when the amount of histamine release induced by the immunological control ranged between 5 and 10%. SCF acted synergistically with IL-5, producing a greater enhancement of histamine release than the sum of each cytokine used alone. Both SCF and, to a lesser extent, IL-5 potentiated anti-IgE-mediated histamine release regardless of passive sensitization of lung fragments. Unlike what was observed with lung fragments, IL-3, GM-CSF and to a lesser extent IL-5, were potent enhancing agents of anti-IgE (1/2,000)-induced histamine release from leukocytes. Maximal enhancement produced by IL-3 (20 ng/ml), GM-CSF (2 ng/ml) and IL-5 (20 ng/ml) reached 92%, 78% and 61%, respectively. By contrast, SCF (0.2-20 ng/ml) was ineffective on human leukocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗