Cell-based therapies for the treatment of idiopathic pulmonary fibrosis (IPF) disease

Induced pluripotent stem cell-based therapies for organ fibrosis

Fibrotic diseases result in organ remodelling and dysfunctional failure and account for one-third of all deaths worldwide. There are no ideal treatments that can halt or reverse progressive organ fibrosis, moreover, organ transplantation is complicated by problems with a limited supply of donor organs and graft rejection. The development of new approaches, especially induced pluripotent stem cell (iPSC)-based therapy, is becoming a hot topic due to their ability to self-renew and differentiate into different cell types that may replace the fibrotic organs. In the past decade, studies have differentiated iPSCs into fibrosis-relevant cell types which were demonstrated to have anti-fibrotic effects that may have the potential to inform new effective precision treatments for organ-specific fibrosis. In this review, we summarize the potential of iPSC-based cellular approaches as therapeutic avenues for treating organ fibrosis, the advantages and disadvantages of iPSCs compared with other types of stem cell-based therapies, as well as the challenges and future outlook in this field.

Anti-Inflammatory and Anti-Fibrotic Effect of Immortalized Mesenchymal-Stem-Cell-Derived Conditioned Medium on Human Lung Myofibroblasts and Epithelial Cells

Idiopathic pulmonary fibrosis (IPF) is caused by progressive lung tissue impairment due to extended chronic fibrosis, and it has no known effective treatment. The use of conditioned media (CM) from an immortalized human adipose mesenchymal stem cell line could be a promising therapeutic strategy, as it can reduce both fibrotic and inflammatory responses. We aimed to investigate the anti-inflammatory and anti-fibrotic effect of CM on human pulmonary subepithelial myofibroblasts (hPSM) and on A549 pulmonary epithelial cells, treated with pro-inflammatory or pro-fibrotic mediators. CM inhibited the proinflammatory cytokine-induced mRNA and protein production of various chemokines in both hPSMs and A549 cells. It also downregulated the mRNA expression of IL-1α, but upregulated IL-1β and IL-6 mRNA production in both cell types. CM downregulated the pro-fibrotic-induced mRNA expression of collagen Type III and the migration rate of hPSMs, but upregulated fibronectin mRNA production and the total protein collagen secretion. CM's direct effect on the chemotaxis and cell recruitment of immune-associated cells, and its indirect effect on fibrosis through the significant decrease in the migration capacity of hPSMs, makes it a plausible candidate for further development towards a therapeutic treatment for IPF.

Harnessing organs-on-a-chip to model tissue regeneration

Tissue engineering has markedly matured since its early beginnings in the 1980s. In addition to the original goal to regenerate damaged organs, the field has started to explore modeling of human physiology "in a dish." Induced pluripotent stem cell (iPSC) technologies now enable studies of organ regeneration and disease modeling in a patient-specific context. We discuss the potential of "organ-on-a-chip" systems to study regenerative therapies with focus on three distinct organ systems: cardiac, respiratory, and hematopoietic. We propose that the combinatorial studies of human tissues at these two scales would help realize the translational potential of tissue engineering.

Type 2 Alveolar Epithelial Cells Differentiated from Human Umbilical Cord Mesenchymal Stem Cells Alleviate Mouse Pulmonary Fibrosis Through β-Catenin-Regulated Cell Apoptosis

Pulmonary fibrosis (PF) is a chronic, progressive, and lethal disease with little response to available therapies. One of the major mechanisms of PF is the repeated injury and inadequate regeneration of the alveolar epithelium. In this study, we induced human umbilical cord mesenchymal stem cells (hUC-MSCs) to differentiate into type 2 alveolar epithelial cells (AEC2s), and we provided evidence that intratracheal transplantation of hUC-MSC-derived AEC2s (MSC-AEC2s) could improve mortality and alleviate fibrosis in bleomycin-induced PF mice. Transplantation of MSC-AEC2s could increase the AEC2 cell count in these mice, and the results of the cell tracing experiment exhibited that the increased AEC2s originated from the self-renewal of mouse alveolar epithelium. The AEC2 survival was controlled by the apoptosis of AEC2s via the expression of β-catenin in PF mice. In in vitro experiments, MSC-AEC2s could alleviate the apoptosis of MLE-12 cells induced by transforming growth factor beta (TGF-β1), which could be eliminated by using PRI-724, a β-catenin inhibitor, suggesting β-catenin signaling involved in the protection against apoptosis provided by MSC-AEC2s. Our study demonstrated that MSC-AEC2s could protect PF mice through regulating apoptosis mediated by β-catenin, which provided a viable strategy for the treatment of PF.

Membrane particles from mesenchymal stromal cells reduce the expression of fibrotic markers on pulmonary cells

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with limited treatment options in which the telomere shortening is a strong predictive factor of poor prognosis. Mesenchymal stromal cells (MSC) administration is probed in several experimental induced lung pathologies; however, MSC might stimulate fibrotic processes. A therapy that avoids MSC side effects of transformation would be an alternative to the use of living cells. Membranes particles (MP) are nanovesicles artificially generated from the membranes of MSC containing active enzymes involved in ECM regeneration. We aimed to investigate the anti-fibrotic role of MP derived from MSC in an in vitro model of pulmonary fibrosis.

METHODS

Epithelial cells (A549) and lung fibroblasts, from IPF patients with different telomere length, were co-cultured with MP and TGF-β for 48h and gene expression of major pro-fibrotic markers were analyzed.

RESULTS

About 90% of both types of cells effectively took up MP without cytotoxic effects. MP decreased the expression of profibrotic proteins such as Col1A1, Fibronectin and PAI-1, in A549 cells. In fibroblasts culture, there was a different response in the inhibitory effect of MP on some pro-fibrotic markers when comparing fibroblast from normal telomere length patients (FN) versus short telomere length (FS), but both types showed an inhibition of Col1A1, Tenascin-c, PAI-1 and MMP-1 gene expression after MP treatment.

CONCLUSIONS

MP conserve some of the properties attributed to the living MSC. This study shows that MP target lung cells, via which they may have a broad anti-fibrotic effect.

The Therapy of Pulmonary Fibrosis in Paracoccidioidomycosis: What Are the New Experimental Approaches?

Pulmonary fibrosis (PF) is considered the most important sequela developed in patients suffering from the chronic form of paracoccidioidomycosis (PCM), which leads to the loss of respiratory function in 50% of cases; this residual pulmonary abnormality is present even after antifungal treatment. To date, there is no effective treatment for PF. However, the use of antifungal drugs in combination with other antibiotics or immunomodulatory compounds, as well as biological therapies that include a monoclonal antibody specific to neutrophils, or prophylactic vaccination employing a recombinant antigen of Paracoccidioides brasiliensis that successfully attenuated PF, has been reported. Additionally, mesenchymal stem cell transplantation in combination with antifungal therapy slightly reduced the inflammatory response and profibrotic molecules induced by P. brasiliensis infection. In this review, I report experimental findings from several studies aiming to identify promising therapeutic strategies for treating PF developed in PCM.

[Human umbilical cord mesenchymal stem cell-derived exosomes alleviate pulmonary fibrosis in mice by inhibiting epithelial-mesenchymal transition]

OBJECTIVE

To study the anti- fibrotic effect of human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-EXOs) and explore the mechanism.

METHODS

Twenty-four C57 BL/6 mice were divided into 4 groups (n=6), including the control group treated with intratracheal injection of saline (3 mg/kg); lung fibrosis model group with intratracheal injection of 1.5 mg/mL bleomycin solution (prepared with saline, 3 mg/kg); EXOs1 group with intratracheal injection of 1.5 mg/mL bleomycin solution (3 mg/kg) and hUCMSC-EXOs (100 μg/250 μL, given by tail vein injection on the next day after modeling); and EXOs2 group with intratracheal injection of 1.5 mg/mL bleomycin solution (3 mg/kg) and hUCMSC-EXOs (100 μg/250 μL, given by tail vein injection on the 10th day after modeling). At 21 days after modeling, pulmonary index, lung tissue pathology and collagen deposition in the mice were assessed using HE staining and Masson staining. The expression level of TGF-β1 was detected using ELISA, and vimentin, E-cadherin and phosphorylated Smad2/3 (p-Smad2/3) were detected using immunohistochemical staining. CCK8 assay was used to evaluate the effect of hUCMSCEXOs on the viability of A549 cells, and Western blotting was used to detect the expression levels of p-Smad2/3, vimentin, and E-cadherin in the cells.

RESULTS

Compared with those in the model group, the mice treated with hUCMSC-EXOs showed significantly reduced the pulmonary index (P < 0.05), collagen deposition, lung tissue pathologies, lowered expressions of TGF-β1 (P < 0.05), vimentin, and p-Smad2/3 and increased expression of E-cadherin. hUCMSC-EXOs given on the second day produced more pronounced effect than that given on the 11th day (P < 0.05). CCK8 assay results showed that hUCMSC-EXOs had no toxic effects on A549 cells (P > 0.05). Western blotting results showed that hUCMSC-EXOs treatment significantly increased the expression of E-cadherin and decreased the expressions of p-Smad2/3 and vimentin in the cells.

CONCLUSIONS

hUCMSC-EXOs can alleviate pulmonary fibrosis in mice by inhibiting epithelialmesenchymal transition activated by the TGF-β1/Smad2/3 signaling pathway, and the inhibitory effect is more obvious when it is administered on the second day after modeling.

Induced pluripotent stem cell-derived lung alveolar epithelial type II cells reduce damage in bleomycin-induced lung fibrosis

Background

Idiopathic pulmonary fibrosis is a chronic, progressive, and severe disease with a limited response to currently available therapies. Epithelial cell injury and failure of appropriate healing or regeneration are central to the pathogenesis of idiopathic pulmonary fibrosis. The purpose of this study is to investigate whether intratracheal transplantation of alveolar type II-like cells differentiated from induced pluripotent stem cells can stop and reverse the fibrotic process in an experimental model of bleomycin-induced lung fibrosis in rats.

Methods

Human induced pluripotent stem cells were differentiated to alveolar type II-like cells and characterized. Lung fibrosis was induced in rats by a single intratracheal instillation of bleomycin. Animals were transplanted with human induced pluripotent stem cells differentiated to alveolar type II-like cells at a dose of 3 × 10⁶ cells/animal 15 days after endotracheal bleomycin instillation when the animal lungs were already fibrotic. Animals were sacrificed 21 days after the induction of lung fibrosis. Lung fibrosis was assessed by hydroxiprolin content, histologic studies, and the expression of transforming growth factor-β and α-smooth muscle actin.

Results

Cell transplantation of alveolar type II-like cells differentiated from induced pluripotent stem cells can significantly reduce pulmonary fibrosis and improve lung alveolar structure, once fibrosis has already formed. This is associated with the inhibition of transforming growth factor-β and α-smooth muscle actin in the damaged rat lung tissue.

Conclusion

To our knowledge, this is the first data to demonstrate that at the fibrotic stage of the disease, intratracheal transplantation of human induced pluripotent differentiated to alveolar type II-like cells halts and reverses fibrosis.

Lung-resident mesenchymal stromal cells are tissue-specific regulators of lung homeostasis

Until recently, data supporting the tissue-resident status of mesenchymal stromal cells (MSC) has been ambiguous since their discovery in the 1950-60s. These progenitor cells were first discovered as bone marrow-derived adult multipotent cells and believed to migrate to sites of injury, opposing the notion that they are residents of all tissue types. In recent years, however, it has been demonstrated that MSC can be found in all tissues and MSC from different tissues represent distinct populations with differential protein expression unique to each tissue type. Importantly, these cells are efficient mediators of tissue repair, regeneration, and prove to be targets for therapeutics, demonstrated by clinical trials (phase 1-4) for MSC-derived therapies for diseases like graft-versus-host-disease, multiple sclerosis, rheumatoid arthritis, and Crohn's disease. The tissue-resident status of MSC found in the lung is a key feature of their importance in the context of disease and injuries of the respiratory system, since these cells could be instrumental to providing more specific and targeted therapies. Currently, bone marrow-derived MSC have been established in the treatment of disease, including diseases of the lung. However, with lung-resident MSC representing a unique population with a different phenotypic and gene expression pattern than MSC derived from other tissues, their role in remediating lung inflammation and injury could provide enhanced efficacy over bone marrow-derived MSC methods. Through this review, lung-resident MSC will be characterized, using previously published data, by surface markers, gene expression patterns, and compared with bone-marrow MSC to highlight similarities and, importantly, differences in these cell types.

Mesenchymal stromal cell exosomes prevent and revert experimental pulmonary fibrosis through modulation of monocyte phenotypes

Mesenchymal stromal/stem cell (MSC) therapy has shown promise in experimental models of idiopathic pulmonary fibrosis (IPF). The aim of this study was to test the therapeutic effects of extracellular vesicles produced by human BM MSCs (MEx) in a bleomycin-induced pulmonary fibrosis model and investigate mechanisms of action. Adult C57BL/6 mice were challenged with endotracheal instillation of bleomycin and treated with MEx concurrently, or for reversal models, at day 7 or 21. Experimental groups were assessed at day 7, 14, or 28. Bleomycin-challenged mice presented with severe septal thickening and prominent fibrosis, and this was effectively prevented or reversed by MEx treatment. MEx modulated lung macrophage phenotypes, shifting the proportions of lung proinflammatory/classical and nonclassical monocytes and alveolar macrophages toward the monocyte/macrophage profiles of control mice. A parallel immunomodulatory effect was demonstrated in the BM. Notably, transplantation of MEx-preconditioned BM-derived monocytes alleviated core features of pulmonary fibrosis and lung inflammation. Proteomic analysis revealed that MEx therapy promotes an immunoregulatory, antiinflammatory monocyte phenotype. We conclude that MEx prevent and revert core features of bleomycin-induced pulmonary fibrosis and that the beneficial actions of MEx may be mediated via systemic modulation of monocyte phenotypes.

Cell-based therapy for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is an example of interstitial lung diseases that is characterized by chronic, progressive, and fibrotic lung injuries. During lung fibrosis, normal healthy lung tissues are replaced by remarkably destroyed alveolar architecture and altered extracellular cell matrix. These changes eventually cause severe disruption of the tightly-controlled gas exchange process and reduction of lung compliance that ultimately lead to both respiratory failure and death. In the last decade, progress has been made toward understanding the pathogenesis of pulmonary fibrosis, and two novel disease-modifying therapies were approved. However, finding more effective treatments for pulmonary fibrosis is still a challenge, with its incidence continues to increase globally, which is associated with significantly high mortality, morbidity and economical healthcare burden. Different stem cell types have recently emerged as a promising therapy for human diseases, including lung fibrosis, with numerous studies on the identification, characterization, proliferation and differentiation of stem cells. A large body of both basic and pre-clinical research on stem cells has been recently translated to patient care worldwide. Herein, we review recent advances in our understanding of the pathophysiology of IPF, and types of cells used in IPF cell-based therapies, including alveolar and mixed lung epithelial cells, different stem cell types (MSCs, ADSCs, IPSCs…etc.), endogenous lung tissue-specific stem cells, and circulating endothelial progenitors (EPCs). We also discuss recent studies on the applications of these cells in IPF therapy and their delivery routes, effective doses for cell therapy, and timing of delivery. Finally, we discuss attractive recent and current clinical trials conducted on cell-based therapy for IPF.

NMDA receptor activation inhibits the protective effect of BM‑MSCs on bleomycin‑induced lung epithelial cell damage by inhibiting ERK signaling and the paracrine factor HGF

Endoplasmic reticulum (ER) stress in alveolar epithelial cells (AECs) is associated with the pathogenesis of pulmonary fibrosis. Bone marrow‑derived mesenchymal stromal cells (BM‑MSCs) can exert protective effects on ER‑stressed AECs via paracrine signaling. In the present study, mouse lung epithelial (MLE)‑12 cells were directly stimulated with various concentrations of bleomycin (BLM). MLE‑12 cell apoptosis was detected by flow cytometry, and Ki67 expression was detected by immunofluorescence to reflect cell proliferation. The results revealed that BLM increased the protein expression levels of X‑box binding protein 1 and immunoglobulin heavy chain‑binding protein, thus inducing ER stress, and caused cell dysfunction by inhibiting proliferation and promoting apoptosis. In addition, MSC‑derived conditioned medium (MSC‑CM) protected MLE‑12 cells from BLM‑induced injury, by reducing ER stress, promoting cell proliferation and inhibiting cell apoptosis. Our previous studies reported that N‑methyl‑D‑aspartate (NMDA) receptor activation partially inhibits the antifibrotic effect of BM‑MSCs on BLM‑induced pulmonary fibrosis through downregulating the paracrine factor hepatocyte growth factor (HGF). In the present study, the synthesis and secretion of HGF were detected by western blotting and ELISA, respectively. Results further demonstrated that NMDA inhibited the synthesis and secretion of HGF in BM‑MSCs, and NMDA‑preconditioned MSC‑CM had no protective effects on BLM‑induced injury in MLE‑12 cells. In addition, activation of the NMDA receptor decreased the phosphorylation levels of extracellular signal‑regulated kinase (ERK)1/2 in BM‑MSCs. Using Honokiol and FR180204, the activator and inhibitor of ERK1/2, respectively, it was then revealed that Honokiol partially eliminated the decrease in HGF expression, whereas FR180204 further promoted the reduction in HGF caused by NMDA. Collectively, these findings suggested that NMDA receptor activation may downregulate HGF by inhibiting ERK signaling in BM‑MSCs, thus weakening their protective effects on BLM‑induced lung epithelial cell damage.

Interrupted reprogramming of alveolar type II cells induces progenitor-like cells that ameliorate pulmonary fibrosis

We describe here an interrupted reprogramming strategy to generate “induced progenitor-like (iPL) cells” from alveolar epithelial type II (AEC-II) cells. A carefully defined period of transient expression of reprogramming factors (Oct4, Sox2, Klf4, and c-Myc (OSKM)) is able to rescue the limited in vitro clonogenic capacity of AEC-II cells, potentially by activation of a bipotential progenitor-like state. Importantly, our results demonstrate that interrupted reprogramming results in controlled expansion of cell numbers yet preservation of the differentiation pathway to the alveolar epithelial lineage. When transplanted to the injured lungs, AEC-II-iPL cells are retained in the lung and ameliorate bleomycin-induced pulmonary fibrosis. Interrupted reprogramming can be used as an alternative approach to produce highly specified functional therapeutic cell populations and may lead to significant advances in regenerative medicine.

A modified reprogramming strategy helps expand populations of surfactant-producing lung cells in a dish without altering their cellular function. A team led by Thomas Waddell and Andras Nagy from the University of Toronto, Canada isolated alveolar type II cells from the lungs of mice. They transiently induced expression of four reprogramming factors in these cells for a defined period of time. Before this “interrupted” reprogramming, the lung cells had limited ability to continue replicating themselves. Afterwards, the cells could expand their numbers dramatically without entering a pluripotent state. Rather, the cells maintained their original function while also expressing genes associated with lung precursor cells, which could explain their proliferative ability. The cells, when transplanted into the injured lungs, helped ameliorate pulmonary fibrosis in a mouse model, suggesting that a similar cell-based therapy may be useful in people.

Mesenchymal Stem Cell Therapy of Pulmonary Fibrosis: Improvement with Target Combination

Although the clinical application of new drugs has been shown to be effective in slowing disease progression and improving the quality of life in patients with pulmonary fibrosis, the damaged lung tissue does not recover with these drugs. Thus, there is an urgent need to establish regenerative therapy, such as stem cell therapy or tissue engineering. Moreover, the clinical application of mesenchymal stem cell (MSC) therapy has been shown to be safe in humans with idiopathic pulmonary fibrosis (IPF). It seems that a combination of MSC transplantation and pharmaceutical therapy might have additional benefits; however, the experimental design for its efficacy is still lacking. In this review, we provide an overview of the mechanisms that were identified when IPF was treated with MSC transplantation or new drugs. To maximize the therapeutic effect, we suggest that MSC transplantation is combined with drug application for synergistic effects. This review provides clinicians and scientists with the most efficient medical options, in the hope that this will spur on future research and lead to an eventual cure for this disease.

Airway transplantation of adipose stem cells protects against bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease with poor prognosis. Adipose-derived stem cells (ADSC) have demonstrated regenerative properties in several tissues. The hypothesis of this study was that airway transplantation of ADSC could protect against bleomycin (BLM)-induced pulmonary fibrosis (PF). Fifty-eight lungs from 29 male Sprague-Dawley rats were analyzed. Animals were randomly divided into five groups: a) control (n=3); b) sham (n=6); c) BLM (n=6); d) BLM+ADSC-2d (n=6); and e) BLM+ADSC-14d (n=8). Animals received 500 µL saline (sham), 2.5 UI/kg BLM in 500 µL saline (BLM), and 2×10⁶ ADSC in 100 µL saline intratracheally at 2 (BLM+ADSC-2d) and 14 days (BLM+ADSC-14d) after BLM. Animals were sacrificed at 28 days. Blinded Ashcroft score was used to determine pulmonary fibrosis extent on histology. Hsp27, Vegf, Nfkβ, IL-1, IL-6, Col4, and Tgfβ1 mRNA gene expression were determined using real-time quantitative-PCR. Ashcroft index was: control=0; sham=0.37±0.07; BLM=6.55±0.34 vs sham (P=0.006). BLM vs BLM+ADSC-2d=4.63±0.38 (P=0.005) and BLM+ADSC-14d=3.77±0.46 (P=0.005). BLM vs sham significantly increased Hsp27 (P=0.018), Nfkβ (P=0.009), Col4 (P=0.004), Tgfβ1 (P=0.006) and decreased IL-1 (P=0.006). BLM+ADSC-2d vs BLM significantly decreased Hsp27 (P=0.009) and increased Vegf (P=0.006), Nfkβ (P=0.009). BLM+ADSC-14d vs BLM significantly decreased Hsp27 (P=0.028), IL-6 (P=0.013), Col4 (P=0.002), and increased Nfkβ (P=0.040) and Tgfβ1 (P=0.002). Airway transplantation of ADSC significantly decreased the fibrosis rate in both early and established pulmonary fibrosis, modulating the expression of Hsp27, Vegfa, Nfkβ, IL-6, Col4, and Tgfβ1. From a translational perspective, this technique could become a new adjuvant treatment for patients with IPF.

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.