From Here to There, Progenitor Cells and Stem Cells Are Everywhere in Lung Vascular Remodeling

CT/NIRF dual-modal imaging tracking and therapeutic efficacy of transplanted mesenchymal stem cells labeled with Au nanoparticles in silica-induced pulmonary fibrosis

Mesenchymal stem cells (MSCs) have shown promising therapeutic effects in cell-based therapies and regenerative medicine. Efficient tracking of MSCs is an urgent clinical need that will help us to understand their behavior after transplantation and allow adjustment of therapeutic strategies. However, no clinically approved tracers are currently available, which limits the clinical translation of stem cell therapy. In this study, a nanoparticle (NP) for computed tomography (CT)/fluorescence dual-modal imaging, Au@Albumin@ICG@PLL (AA@ICG@PLL), was developed to track bone marrow-derived mesenchymal stem cells (BMSCs) that were administered intratracheally into mice with silica-induced pulmonary fibrosis, which facilitated understanding of the therapeutic effect and the possible molecular mechanism of stem cell therapy. The AuNPs were first formed in bovine serum albumin (BSA) solution and modified with indocyanine green (ICG), and subsequently coated with a poly-l-lysine (PLL) layer to enhance intracellular uptake and biocompatibility. BMSCs were labeled with AA@ICG@PLL NPs with high efficiency without an effect on biological function or therapeutic capacity. The injected AA@ICG@PLL-labeled BMSCs could be tracked via CT and near-infrared fluorescence (NIRF) imaging for up to 21 days after transplantation. Using these NPs, the molecular anti-inflammatory mechanism of transplanted BMSCs was revealed, which included the downregulation of proinflammatory cytokines, suppression of macrophage activation, and delay of the fibrosis process. This study suggests a promising role for imaging-guided MSC-based therapy for pulmonary fibrosis, such as idiopathic pulmonary fibrosis (IPF) and pneumoconiosis.

Bone marrow stem cells therapy alleviates vascular injury in a chronic obstructive pulmonary disease‑obstructive sleep apnea overlap syndrome rat model

Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) are highly prevalent potential risk factors for systemic disease. Previous studies have reported that COPD and OSA are major independent risk factors for cardio- or cerebrovascular diseases. The present study aimed to investigate the role of bone marrow mesenchymal stem cells (BMSCs) on vascular injury in a COPD-OSA overlap syndrome (OS) rat model. Rats were randomly divided into three groups: Sham, OS model and BMSC. BMSC localization in major organs was detected via confocal laser fluorescence microscopy, and the aortic tissue pathological changes and related genes were measured using hematoxylin & eosin and Masson staining. Genes associated with vascular endothelial cell injury, including endothelin 1, vascular cell adhesion molecule 1 and endothelial nitric oxide synthase, were detected via reverse transcription-quantitative PCR and western blotting. Apoptosis of vascular endothelial cells was detected using TUNEL and immunofluorescence assays. The endothelial cell marker CD31 in injured vessels was analyzed via immunohistochemistry. BMSCs migrated into the heart, liver, spleen, lung, kidney, brain and aorta in the OS model. The green fluorescence expression of BMSCs demonstrated the highest level in the lung, followed by the aorta. Aortic tissue had a more severe vascular injury and increased apoptosis in the model group compared with the BMSC group. Vascular endothelial cell apoptosis was decreased in the BMSC group compared with the model group. The findings suggested that BMSCs could repair vascular injury by inhibiting endothelial cell damage and apoptosis. These data provide a theoretical basis for the treatment of cardiovascular diseases caused by OS with BMSCs.

Translating Basic Research into Safe and Effective Cell-based Treatments for Respiratory Diseases

Respiratory diseases, such as chronic obstructive pulmonary disease and pulmonary fibrosis, result in severely impaired quality of life and impose significant burdens on healthcare systems worldwide. Current disease management involves pharmacologic interventions, oxygen administration, reduction of infections, and lung transplantation in advanced disease stages. An increasing understanding of mechanisms of respiratory epithelial and pulmonary vascular endothelial maintenance and repair and the underlying stem/progenitor cell populations, including but not limited to airway basal cells and type II alveolar epithelial cells, has opened the possibility of cell replacement-based regenerative approaches for treatment of lung diseases. Further potential for personalized therapies, including in vitro drug screening, has been underscored by the recent derivation of various lung epithelial, endothelial, and immune cell types from human induced pluripotent stem cells. In parallel, immunomodulatory treatments using allogeneic or autologous mesenchymal stromal cells have shown a good safety profile in clinical investigations for acute inflammatory conditions, such as acute respiratory distress syndrome and septic shock. However, as yet, no cell-based therapy has been shown to be both safe and effective for any lung disease. Despite the investigational status of cell-based interventions for lung diseases, businesses that market unproven, unlicensed and potentially harmful cell-based interventions for respiratory diseases have proliferated in the United States and worldwide. The current status of various cell-based regenerative approaches for lung disease as well as the effect of the regulatory environment on clinical translation of such approaches are presented and critically discussed in this review.

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.

Recent advances in our understanding of the mechanisms of late lung development and bronchopulmonary dysplasia

The objective of lung development is to generate an organ of gas exchange that provides both a thin gas diffusion barrier and a large gas diffusion surface area, which concomitantly generates a steep gas diffusion concentration gradient. As such, the lung is perfectly structured to undertake the function of gas exchange: a large number of small alveoli provide extensive surface area within the limited volume of the lung, and a delicate alveolo-capillary barrier brings circulating blood into close proximity to the inspired air. Efficient movement of inspired air and circulating blood through the conducting airways and conducting vessels, respectively, generates steep oxygen and carbon dioxide concentration gradients across the alveolo-capillary barrier, providing ideal conditions for effective diffusion of both gases during breathing. The development of the gas exchange apparatus of the lung occurs during the second phase of lung development-namely, late lung development-which includes the canalicular, saccular, and alveolar stages of lung development. It is during these stages of lung development that preterm-born infants are delivered, when the lung is not yet competent for effective gas exchange. These infants may develop bronchopulmonary dysplasia (BPD), a syndrome complicated by disturbances to the development of the alveoli and the pulmonary vasculature. It is the objective of this review to update the reader about recent developments that further our understanding of the mechanisms of lung alveolarization and vascularization and the pathogenesis of BPD and other neonatal lung diseases that feature lung hypoplasia.