Allogeneic Human Mesenchymal Stem Cells in Patients With Idiopathic Pulmonary Fibrosis via Intravenous Delivery (AETHER): A Phase I Safety Clinical Trial

Thy-1 dependent uptake of mesenchymal stem cell-derived extracellular vesicles blocks myofibroblastic differentiation

Bone marrow-derived mesenchymal stem cells (MSC) have been promoted for multiple therapeutic applications. Many beneficial effects of MSCs are paracrine, dependent on extracellular vesicles (EVs). Although MSC-derived EVs (mEVs) are beneficial for acute lung injury and pulmonary fibrosis, mechanisms of mEV uptake by lung fibroblasts and their effects on myofibroblastic differentiation have not been established. We demonstrate that mEVs, but not fibroblast EVs (fEVs), suppress TGFβ1-induced myofibroblastic differentiation of normal and idiopathic pulmonary fibrosis (IPF) lung fibroblasts. MEVs display increased time- and dose-dependent cellular uptake compared to fEVs. Removal or blocking of Thy-1, or blocking Thy-1-beta integrin interactions, decreased mEV uptake and prevented suppression of myofibroblastic differentiation. MicroRNAs (miRs) 199a/b-3p, 21-5p, 630, 22-3p, 196a-5p, 199b-5p, 34a-5p and 148a-3p are selectively packaged in mEVs. In silico analyses indicated that IPF lung fibroblasts have increased expression of genes that are targets of mEV-enriched miRs. MiR-630 mimics blocked TGFβ1 induction of CDH2 in normal and IPF fibroblasts, and antagomiR-630 abrogated the effect of mEV on CDH2 expression. These data suggest that the interaction of Thy-1 with beta integrins mediates mEV uptake by lung fibroblasts, which blocks myofibroblastic differentiation, and that mEVs are enriched for miRs that target profibrotic genes up-regulated in IPF fibroblasts.

Mesenchymal stem cells reduce hypoxia-induced apoptosis in alveolar epithelial cells by modulating HIF and ROS hypoxic signaling

Distal lung diseases, such as pulmonary fibrosis or acute lung injury, are commonly associated with local alveolar hypoxia that may be deleterious through the stimulation of alveolar epithelial cell (AEC) apoptosis. In various murine models of alveolar injury, administration of allogenic human mesenchymal stem cells (hMSCs) exerts an overall protective paracrine effect, limiting lung inflammation and fibrosis. However, the precise mechanisms on lung cells themselves remain poorly understood. Here, we investigated whether hMSC-conditioned medium (hMSC-CM) would protect AECs from hypoxia-induced apoptosis and explored the mechanisms involved in this cytoprotective effect. Exposure of rat primary AECs to hypoxia (1.5% O₂ for 24 h) resulted in hypoxia-inducible factor (HIF)-1α protein stabilization, partly dependent on reactive oxygen species (ROS) accumulation, and in a twofold increase in AEC apoptosis that was prevented by the HIF inhibitor 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl-indazole and the antioxidant drug N-acetyl cysteine. Incubation of AECs with hMSC-CM significantly reduced hypoxia-induced apoptosis. hMSC-CM decreased HIF-1α protein expression, as well as ROS accumulation through an increase in antioxidant enzyme activities. Expression of Bnip3 and CHOP, two proapoptotic targets of HIF-1α and ROS pathways, respectively, was suppressed by hMSC-CM, while Bcl-2 expression was restored. The paracrine protective effect of hMSC was partly dependent on keratinocyte growth factor and hepatocyte growth factor secretion, preventing ROS and HIF-1α accumulation.

Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease characterized by progressive lung scarring and the histological picture of usual interstitial pneumonia (UIP). It is associated with increasing cough and dyspnoea and impaired quality of life. IPF affects ∼3 million people worldwide, with incidence increasing dramatically with age. The diagnostic approach includes the exclusion of other interstitial lung diseases or overlapping conditions and depends on the identification of the UIP pattern, usually with high-resolution CT; lung biopsy might be required in some patients. The UIP pattern is predominantly bilateral, peripheral and with a basal distribution of reticular changes associated with traction bronchiectasis and clusters of subpleural cystic airspaces. The biological processes underlying IPF are thought to reflect an aberrant reparative response to repetitive alveolar epithelial injury in a genetically susceptible ageing individual, although many questions remain on how to define susceptibility. Substantial progress has been made in the understanding of the clinical management of IPF, with the availability of two pharmacotherapeutic agents, pirfenidone and nintedanib, that decrease physiological progression and likely improve progression-free survival. Current efforts are directed at identifying IPF early, potentially relying on combinations of biomarkers that include circulating factors, demographics and imaging data.

The Processes and Mechanisms of Cardiac and Pulmonary Fibrosis

Fibrosis is the formation of fibrous connective tissue in response to injury. It is characterized by the accumulation of extracellular matrix components, particularly collagen, at the site of injury. Fibrosis is an adaptive response that is a vital component of wound healing and tissue repair. However, its continued activation is highly detrimental and a common final pathway of numerous disease states including cardiovascular and respiratory disease. Worldwide, fibrotic diseases cause over 800,000 deaths per year, accounting for ~45% of total deaths. With an aging population, the incidence of fibrotic disease and subsequently the number of fibrosis-related deaths will rise further. Although, fibrosis is a well-recognized cause of morbidity and mortality in a range of disease states, there are currently no viable therapies to reverse the effects of chronic fibrosis. Numerous predisposing factors contribute to the development of fibrosis. Biological aging in particular, interferes with repair of damaged tissue, accelerating the transition to pathological remodeling, rather than a process of resolution and regeneration. When fibrosis progresses in an uncontrolled manner, it results in the irreversible stiffening of the affected tissue, which can lead to organ malfunction and death. Further investigation into the mechanisms of fibrosis is necessary to elucidate novel, much needed, therapeutic targets. Fibrosis of the heart and lung make up a significant proportion of fibrosis-related deaths. It has long been established that the heart and lung are functionally and geographically linked when it comes to health and disease, and thus exploring the processes and mechanisms that contribute to fibrosis of each organ, the focus of this review, may help to highlight potential avenues of therapeutic investigation.

Cell-Based Therapies for Tissue Fibrosis

The development of tissue fibrosis in the context of a wound-healing response to injury is common to many chronic diseases. Unregulated or persistent fibrogenesis may lead to structural and functional changes in organs that increase the risk of significant morbidity and mortality. We will explore the natural history, epidemiology, and pathogenesis of fibrotic disease affecting the lungs, kidneys, and liver as dysfunction of these organs is responsible for a substantial proportion of global mortality. For many patients with end-stage disease, organ transplantation is the only effective therapy to prolong life. However, not all patients are candidates for the major surgical interventions and life-long immunosuppression required for a successful outcome and donor organs may not be available to meet the clinical need. We will provide an overview of the latest treatment strategies for these conditions and will focus on stem or progenitor cell-based therapies for which there is substantial pre-clinical evidence based on animal models as well as early phase clinical trials of cell-based therapy in man.

Stem-cell extracellular vesicles and lung repair

Four out of the ten leading causes of morbidity and mortality worldwide are lung diseases. Despite advances in comprehending the pathophysiological mechanisms involved in these disorders, for several respiratory diseases, there is still no effective treatment able to stop their natural history or reverse the morphological and functional damage they cause. In this context, recent research has supported a potential role of cell therapy for lung diseases and critical illness. The anti-inflammatory, antifibrotic, and microbicidal effects of stem cells are mainly attributed to their secretome, which contains proteins, lipids, microRNAs, and mRNAs. These are secreted in the conditioned medium and are also present in extracellular vesicles (EVs). This review will provide a detailed discussion of the role of EVs produced by mesenchymal stromal cells in preclinical experimental models of pulmonary disorders and critical illness, as well as in ongoing clinical trials.

Multipotent mesenchymal stem cells in lung fibrosis

Rationale

Stem cells have been identified in the human lung; however, their role in lung disease is not clear. We aimed to isolate mesenchymal stem cells (MSC) from human lung tissue and to study their in vitro properties.

Methods

MSC were cultured from lung tissue obtained from patients with fibrotic lung diseases (n = 17), from emphysema (n = 12), and normal lungs (n = 3). Immunofluorescence stainings were used to characterize MSC. The effect of MSC-conditioned media (MSC-CM) on fibroblast proliferation and on lung epithelial wound repair was studied.

Results

Expression of CD44, CD90, and CD105 characterized the cells as MSC. Moreover, the cells stained positive for the pluripotency markers Oct3/4 and Nanog. Positive co-stainings of chemokine receptor type 4 (CXCR4) with CD44, CD90 or CD105 indicated the cells are of bone marrow origin. MSC-CM significantly inhibited the proliferation of lung fibroblasts by 29% (p = 0.0001). Lung epithelial repair was markedly increased in the presence of MSC-CM (+ 32%). Significantly more MSC were obtained from fibrotic lungs than from emphysema or control lungs.

Conclusions

Our study demonstrates enhanced numbers of MSC in fibrotic lung tissue as compared to emphysema and normal lung. The cells inhibit the proliferation of fibroblasts and enhance epithelial repair in vitro. Further in vivo studies are needed to elucidate their potential role in the treatment of lung fibrosis.

Lung Diseases of the Elderly: Cellular Mechanisms

Natural lung aging is characterized by molecular and cellular changes in multiple lung cell populations. These changes include shorter telomeres, increased expression of cellular senescence markers, increased DNA damage, oxidative stress, apoptosis, and stem cell exhaustion. Aging, combined with the loss of protective repair processes, correlates with the development and incidence of chronic respiratory diseases, including idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease. Ultimately, it is the interplay of age-related changes in biology and the subsequent responses to environmental exposures that largely define the physiology and clinical course of the aging lung.

Investigational drugs for idiopathic pulmonary fibrosis

INTRODUCTION

IPF is a specific form of chronic fibrosing interstitial pneumonia of unknown cause, characterized by progressive worsening in lung function and an unfavorable prognosis. Current concepts on IPF pathogenesis are based on a dysregulated wound healing response, leading to an over production of extracellular matrix. Based on recent research however, several other mechanisms are now proposed as potential targets for novel therapeutic strategies. Areas covered: This review analyzes the current investigational strategies targeting extracellular matrix deposition, tyrosine-kinase antagonism, immune and autoimmune response, and cell-based therapy. A description of the pathogenic rationale implied in each novel therapeutic approach is summarized. Expert opinion: New IPF drugs are being evaluated in the context of phase 1 and 2 clinical trials. Nevertheless, many drugs that have shown efficacy in preclinical studies, failed to exhibit the same positive effect when translated to humans. A possible explanation for these failures might be related to the known limitations of animal models of the disease. The recent development of 3D systems composed of cells from individual patients that recreate an ex-vivo model of IPF, could lead to significant improvements in disease pathogenesis and treatment. New drugs could be tested on more genuine models and clinicians could tailor therapy based on patient's response.

Proceedings: Regenerative Medicine for Lung Diseases: A CIRM Workshop Report

The mission of the California Institute of Regenerative Medicine (CIRM) is to accelerate treatments to patients with unmet medical needs. In September 2016, CIRM sponsored a workshop held at the University of California, Los Angeles, to discuss regenerative medicine approaches for treatment of lung diseases and to identify the challenges remaining for advancing such treatments to the clinic and market approval. Workshop participants discussed current preclinical and clinical approaches to regenerative medicine in the lung, as well as the biology of lung stem cells and the role of stem cells in the etiology of various lung diseases. The outcome of this effort was the recognition that whereas transient cell delivery approaches are leading the way in the clinic, recent advances in the understanding of lung stem cell biology, in vitro and in vivo disease modeling, gene editing and replacement methods, and cell engraftment approaches raise the prospect of developing cures for some lung diseases in the foreseeable future. In addition, advances in in vitro modeling using lung organoids and “lung on a chip” technology are setting the stage for high quality small molecule drug screening to develop treatments for lung diseases with complex biology. Stem Cells Translational Medicine2017;6:1823–1828

Mesenchymal stem cells in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a major cause of respiratory failure in critically ill patients and common outcome of various lung interstitial diseases. Its mortality remains high, and no effective pharmacotherapy, in addition to artificial ventilation and transplantation, exists. As such, the administration of mesenchymal stem or stromal cells (MSCs) is currently investigated as a new therapeutic method for pulmonary fibrosis. Clinical trials on MSC-based therapy as a potential treatment for lung injury and fibrosis are also performed. MSCs can migrate to injured sites and secrete multiple paracrine factors and then regulate endothelial and epithelial permeability, decrease inflammation, enhance tissue repair, and inhibit bacterial growth. In this review, recent studies on stem cells, particularly MSCs, involved in alleviating lung inflammation and fibrosis and their potential MSC-induced mechanisms, including migration and differentiation, soluble factor and extracellular vesicle secretion, and endogenous regulatory functions, were summarized.

Pulmonary fibrosis, part II: state-of-the-art patient management

INTRODUCTION

While many pharmacologic therapies for the treatment of idiopathic pulmonary fibrosis (IPF) have been evaluated via randomized, placebo-controlled clinical trials (RCTs) conducted over the past two decades, most therapies have been shown to be ineffective or even potentially harmful. However, a number of recently completed RCTs have shown significant efficacy for pirfenidone and nintedanib for the treatment of IPF. Areas covered: This manuscript reviews recent advances in the management of IPF and other forms of fibrosing interstitial lung disease (ILD) with an emphasis on IPF. The material upon which this discussion is based was obtained from various published texts and manuscripts identified via literature searching (e.g. PubMed). Expert commentary: Anti-fibrotic drugs are now available for clinical use and perceived as standard-of-care therapies that have the potential to blunt disease progression for many patients with IPF. However, these agents do not necessarily stop disease progression or have a significant impact on mortality, and more effective pharmacologic therapies are needed for patients with IPF. Additionally, whether anti-fibrotic agents can be effective therapies for other forms of pulmonary fibrosis, which often have radiologic and histopathologic manifestations that mimic IPF, is being evaluated in a number of RCTs.