Cell therapy for lung disease

Intracavernosal mesenchymal stem cell therapy in ischaemic priapism: an experimental study

INTRODUCTION

The most common form of priapism is ischaemic and its prevalence in men has increased in recent years as a result of intracavernosal drug use. Currently, there is no approved specific treatment for ischaemic priapism other than cavernosal aspiration, which can only provide detumescence. This study aims to evaluate the efficacy of intracavernosal mesenchymal stem cell (MSC) therapy in an ischaemic priapism model.

MATERIAL AND METHODS

Thirty male Wistar albino rats were divided into three groups: sham (n = 6), priapism (n = 12) and priapism + MSC treatment (n = 12). The experimental groups were also divided into 1 and 12 h subgroups of ischaemic priapism. The experimental model was created using a vacuum erection device and constrictive tape technique, and intracavernosal MSC were applied immediately after the tape was removed. After 4 weeks, intracavernosal pressures (ICPs) and systemic mean arterial pressure (MAP) were measured. Penectomy was then performed to assess histopathological and molecular changes in the rats' penile tissues.

RESULTS

In the ischaemic priapism model, MSC therapy showed significant improvements in peak and mean ICPs and mean ICP/MAP ratio. Histopathological analysis showed significant increases in smooth-muscle/collagen ratio and e-NOS and n-NOS expression. Although there was a decrease in fibrosis, it was not significant. At the molecular level, there were significant decreases in TGF-beta and VEGF mRNA expression, whilst NGF and BDNF mRNA-expression levels showed significant increases with MSC therapy. In terms of ICPs, the therapy showed more significant improvements in short-term priapism. However, when looking at histopathological and molecular parameters, the therapy had positive effects on a wider range of parameters in the long-term priapism.

CONCLUSION

MSC treatment improved cavernosal physiology and had positive effects at the histopathological and molecular level in the ischaemic priapism model.

Mesenchymal Stem Cell-Exosomal miR-99a Attenuate Silica-Induced Lung Fibrosis by Inhibiting Pulmonary Fibroblast Transdifferentiation

Silicosis is one of the most prevalent and fatal occupational diseases worldwide, with unsatisfactory clinical outcomes. This study aimed to investigate the therapeutic effect and related molecular mechanisms of how mesenchymal stem cell (MSC)-secreted exosomes alleviate SiO2-induced pulmonary fibrosis. miR-99a-5p was significantly downregulated in silicosis models via high-throughput miRNA screening, and was overlapped with miRNAs in exosomes from MSCs. miR-99a-5p was significantly downregulated in the lung of a mice silicosis model and in TGFβ1-induced NIH-3T3 cells. In contrast, fibroblast growth factor receptor 3 (FGFR3), a direct target gene of miR-99a-5p, was upregulated in vitro and in vivo. Furthermore, we demonstrated that MSC-derived exosomes deliver enriched miR-99a-5p to target cells and inhibit TGF-β1-induced fibroblast transdifferentiation to reduce collagen protein production. Similarly, in a silicosis mouse model, MSC-derived exosome treatment through the tail veins of the mice counteracted the upregulation of fibrosis-related proteins and collagen deposition in the lung of the mice. By constructing exosomal therapeutic cell models with different miR-99a expressions, we further demonstrated that miR-99a-5p might attenuate pulmonary fibrosis by regulating target protein FGFR3 and downstream mitogen-activated protein kinase (MAPK) signalling pathways. Our study demonstrated that MSC-derived exosomes ameliorate SiO2-induced pulmonary fibrosis by inhibiting fibroblast transdifferentiation and represent an attractive method of pulmonary fibrosis treatment.

Mesenchymal stromal cell-based therapy in lung diseases; from research to clinic

Recent studies demonstrated that mesenchymal stem cells (MSCs) are important for the cell-based therapy of diseased or injured lung due to their immunomodulatory and regenerative properties as well as limited side effects in experimental animal models. Preclinical studies have shown that MSCs have also a remarkable effect on the immune cells, which play major roles in the pathogenesis of multiple lung diseases, by modulating their activity, proliferation, and functions. In addition, MSCs can inhibit both the infiltrated immune cells and detrimental immune responses in the lung and can be used in treating lung diseases caused by a virus infection such as Tuberculosis and SARS-COV-2. Moreover, MSCs are a source for alveolar epithelial cells such as type 2 (AT2) cells. These MSC-derived functional AT2-like cells can be used to treat and diminish serious lung disorders, including acute lung injury, asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis in animal models. As an alternative MSC-based therapy, extracellular vesicles that are derived from MSC-derived can be employed in regenerative medicine. Herein, we discussed the key research findings from recent clinical and preclinical studies on the functions of MSCs in treating some common and well-studied lung diseases. We also discussed the mechanisms underlying MSC-based therapy of well-studied lung diseases, and the recent employment of MSCs in both the attenuation of lung injury/inflammation and promotion of the regeneration of lung alveolar cells after injury. Finally, we described the role of MSC-based therapy in treating major pulmonary diseases such as pneumonia, COPD, asthma, and idiopathic pulmonary fibrosis (IPF).

Autologous mesenchymal stromal cells embedded with Tissucol Duo® for prevention of air leak after anatomical lung resection: results of a prospective phase I/II clinical trial with long-term follow-up

BACKGROUND

Prolonged air leak (PAL) is the most frequent complication after pulmonary resection. Several measures have been described to prevent the occurrence of PAL in high-risk patients, however, the potential role of mesenchymal stem cells (MSCs) applied in the parenchymal suture line to prevent postoperative air leak in this setting has not been fully addressed.

OBJECTIVE

To analyse the feasibility, safety and potential clinical efficacy of the implantation of autologous MSCs embedded in Tissucol Duo® as a prophylactic alternative to prevent postoperative prolonged air leak after pulmonary resection in high-risk patients.

STUDY DESIGN

Phase I/II single-arm prospective clinical trial.

METHODS

Six patients with high risk of PAL undergoing elective pulmonary resection were included. Autologous bone marrow-derived MSCs were expanded at our Good Manufacturing Practice (GMP) Facility and implanted (embedded in a Tissucol Duo® carrier) in the parenchymal suture line during pulmonary resection surgery. Patients were monitored in the early postoperative period and evaluated for possible complications or adverse reactions. In addition, all patients were followed-up to 5 years for clinical outcomes.

RESULTS

The median age of patients included was 66 years (range: 55-70 years), and male/female ratio was 5/1. Autologous MSCs were expanded in five cases, in one case MSCs expansion was insufficient. There were no adverse effects related to cell implantation. Regarding efficacy, median air leak duration was 0 days (range: 0-2 days). The incidence of PAL was nil. Radiologically, only one patient presented pneumothorax in the chest X-ray at discharge. No adverse effects related to the procedure were recorded during the follow-up.

CONCLUSIONS

The use of autologous MSCs for prevention of PAL in patients with high risk of PAL is feasible, safe and potentially effective.

TRIAL REGISTRATION NO

EudraCT: 2013-000535-27.

CLINICALTRIALS

gov idenfier: NCT02045745.

Antler stem cell exosomes alleviate pulmonary fibrosis via inhibiting recruitment of monocyte macrophage, rather than polarization of M2 macrophages in mice

Pulmonary fibrosis (PF), a chronic interstitial lung disease, is characterized by over-abundant deposition of extracellular matrix consisting mainly of collagen I. In previous studies, we demonstrated that deer antler stem cells (AnSCs), a novel type of adult stem cell, are capable of significantly down-regulating collagen formation in different organs and tissues and speculated that they could effectively treat PF via reducing collagen deposition in the lung tissue. In the present study, we found that administration of AnSCs improved the survival rate of PF mice and reduced lung fibrosis, collagen deposition and myofibroblast differentiation. The effects of AnSC treatment were significantly better than the positive control (adipose-derived stem cells). Interestingly, AnSC-Exos were almost equally effective as AnSCs in treating PF, suggesting that the effects of AnSCs on reduction of PF may be mainly through a paracrine mechanism. Further, AnSC-Exos reduced the number of M2 macrophages, a type of macrophage that secrets pro-fibrotic factors to accelerate fibrotic progression, in the lung tissues. In vitro experiments showed that the effects of AnSC-Exos on macrophage modulation were likely achieved via inhibition of the recruitment of circulating monocyte-derived macrophages (reducing the number of macrophages), rather than via inhibition of M2 polarization of macrophages. Inhibition of macrophage recruitment by AnSCs may be achieved indirectly via inhibiting CCL7 expression in fibroblasts; both let-7b and let-7a were highly enriched in AnSC-Exos and may play a critical role in the inhibition of CCL7 expression of fibroblasts. Collectively, the use of antler stem cells or their exosomes opens up a novel strategy for PF treatment in the clinical setting.

MiR-148a-3p within HucMSC-Derived Extracellular Vesicles Suppresses Hsp90b1 to Prevent Fibroblast Collagen Synthesis and Secretion in Silica-Induced Pulmonary Fibrosis

Silicosis is a fatal occupational respiratory disease caused by the prolonged inhalation of respirable silica. The core event of silicosis is the heightened activity of fibroblasts, which excessively synthesize extracellular matrix (ECM) proteins. Our previous studies have highlighted that human umbilical cord mesenchymal stem cell-derived extracellular vesicles (hucMSC-EVs) hold promise in mitigating silicosis and the significant role played by microRNAs (miRNAs) in this process. Delving deeper into this mechanism, we found that miR-148a-3p was the most abundant miRNA of the differential miRNAs in hucMSC-EVs, with the gene heat shock protein 90 beta family member 1 (Hsp90b1) as a potential target. Notably, miR-148a-3p's expression was downregulated during the progression of silica-induced pulmonary fibrosis both in vitro and in vivo, but was restored after hucMSC-EVs treatment (p < 0.05). Introducing miR-148a-3p mimics effectively hindered the collagen synthesis and secretion of fibroblasts induced by transforming growth factor-β1 (TGF-β1) (p < 0.05). Confirming our hypothesis, Hsp90b1 was indeed targeted by miR-148a-3p, with significantly reduced collagen activity in TGF-β1-treated fibroblasts upon Hsp90b1 inhibition (p < 0.05). Collectively, our findings provide compelling evidence that links miR-148a-3p present in hucMSC-EVs with the amelioration of silicosis, suggesting its therapeutic potential by specifically targeting Hsp90b1, thereby inhibiting fibroblast collagen activities. This study sheds light on the role of miR-148a-3p in hucMSC-EVs, opening avenues for innovative therapeutic interventions targeting molecular pathways in pulmonary fibrosis.

Mesenchymal stem cells in lung diseases and their potential use in COVID-19 ARDS: A systematized review

COVID-19 can converge with the pro-inflammatory immunoregulatory mechanisms of chronic lung diseases. Given the disorders inherent to lung transplantation and the inexistence of other definitive therapeutic alternatives, Adipose tissue-derived Stem Cells (ASCs) presented themselves as a therapeutic hope. The purpose of this review is to assess the basis for the potential use of ASCs in lung diseases unresponsive to conventional therapy, relating to their possible use in COVID-19 ARDS. 35 studies comprised this review, 14 being narrative reviews, 19 preclinical trials and two proofs of concept. COVID-19 can converge with the pro-inflammatory immunoregulatory mechanisms of chronic lung diseases. In view of the disorders inherent to lung transplantation and the inexistence of definitive therapeutic alternatives, Adipose tissue-derived Stem Cells (ASCs) presented themselves as a therapeutic hope. Its detailed reading indicated the absence of serious adverse effects and toxicity to the administration of ASCs and suggested possible effectiveness in reducing lung damage, in addition to promoting the recovery of leukocytes and lymphocytes with its immunomodulatory and anti-apoptotic effects. The revised clinical data suggests optimism in the applicability of ASCs in other immunoinflammatory diseases and in severe COVID-19 ARDS. However, further studies are needed to develop a consensus on the methods of collection of ASCs, the ideal dosage schedule, the most effective time and route of administration, as well as on the definition of indications for the administration of ASCs in cases of COVID-19 for conducting clinical trials in near future.

Dual Labeling of Primary Cells with Fluorescent Gadolinium Oxide Nanoparticles

The interest in mesenchymal stromal cells as a therapy option is increasing rapidly. To improve their implementation, location, and distribution, the properties of these must be investigated. Therefore, cells can be labeled with nanoparticles as a dual contrast agent for fluorescence and magnetic resonance imaging (MRI). In this study, a more efficient protocol for an easy synthesis of rose bengal-dextran-coated gadolinium oxide (Gd₂O₃-dex-RB) nanoparticles within only 4 h was established. Nanoparticles were characterized by zeta potential measurements, photometric measurements, fluorescence and transmission electron microscopy, and MRI. In vitro cell experiments with SK-MEL-28 and primary adipose-derived mesenchymal stromal cells (ASC), nanoparticle internalization, fluorescence and MRI properties, and cell proliferation were performed. The synthesis of Gd₂O₃-dex-RB nanoparticles was successful, and they were proven to show adequate signaling in fluorescence microscopy and MRI. Nanoparticles were internalized into SK-MEL-28 and ASC via endocytosis. Labeled cells showed sufficient fluorescence and MRI signal. Labeling concentrations of up to 4 mM and 8 mM for ASC and SK-MEL-28, respectively, did not interfere with cell viability and proliferation. Gd₂O₃-dex-RB nanoparticles are a feasible contrast agent to track cells via fluorescence microscopy and MRI. Fluorescence microscopy is a suitable method to track cells in in vitro experiments with smaller samples.

In Vivo Fate of CXCR2-Overexpressing Mesenchymal Stromal/Stem Cells in Pulmonary Diseases Monitored by Near-Infrared Region 2 Imaging

Lung-associated diseases pose a huge threat to human society. Mesenchymal stromal/stem cells (MSCs) hold great promise in the treatment of pulmonary diseases through cell transdifferentiation, paracrine factors, immune regulation, EV secretion, and drug loading. However, intravenous injection of MSCs often resulted in limited lesion tropism and apparent off-target accumulation. The IL-8-CXCR1/2 chemokine axis has been shown to be involved in progression of diseases including lung cancer and acute lung injury (ALI). Herein, we took advantage of this chemokine axis to enhance the homing of MSCs to cancerous and inflammation lesions. The in vivo distribution of MSCs was further monitored real-time by near-infrared region 2 (NIR-II) imaging owing to its outstanding performance in deep tissue imaging. Specifically, a new high-brightness D-A-D NIR-II dye, LJ-858, was synthesized and coprecipitated with a poly(d,l-lactic acid) polymer to form LJ-858 nanoparticles (NPs) with a relative quantum yield of 14.978%. LJ-858 NPs can efficiently label MSCs, and the NIR-II signal can be stable for 14 days without compromising the cell viability. Subcutaneous tracking of labeled MSCs showed no significant decline of NIR-II intensity within 24 h. The enhanced tropism of CXCR2-overexpressing MSCs to A549 tumor cells and the inflamed lung tissue was demonstrated through transwell models. The in vivo and ex vivo NIR-II imaging results further validated the significantly enhanced lesion retention of MSC^CXCR2 in the lung cancer and ALI models. Taken together, this work reported a robust strategy to enhance the pulmonary disease tropism by the IL-8-CXCR1/2 chemokine axis. In addition, in vivo distribution of MSCs was successfully visualized by NIR-II imaging, which provides more insights into optimizing protocols for MSC-based therapies in the future.

Imaging drug delivery to the lungs: Methods and applications in oncology

Direct delivery to the lung via inhalation is arguably one of the most logical approaches to treat lung cancer using drugs. However, despite significant efforts and investment in this area, this strategy has not progressed in clinical trials. Imaging drug delivery is a powerful tool to understand and develop novel drug delivery strategies. In this review we focus on imaging studies of drug delivery by the inhalation route, to provide a broad overview of the field to date and attempt to better understand the complexities of this route of administration and the significant barriers that it faces, as well as its advantages. We start with a discussion of the specific challenges for drug delivery to the lung via inhalation. We focus on the barriers that have prevented progress of this approach in oncology, as well as the most recent developments in this area. This is followed by a comprehensive overview of the different imaging modalities that are relevant to lung drug delivery, including nuclear imaging, X-ray imaging, magnetic resonance imaging, optical imaging and mass spectrometry imaging. For each of these modalities, examples from the literature where these techniques have been explored are provided. Finally the different applications of these technologies in oncology are discussed, focusing separately on small molecules and nanomedicines. We hope that this comprehensive review will be informative to the field and will guide the future preclinical and clinical development of this promising drug delivery strategy to maximise its therapeutic potential.

Lung organoids: current strategies for generation and transplantation

Lung diseases occupy a leading position in human morbidity and are the third leading cause of death. Often the chronic forms of these diseases do not respond to therapy, so that lung transplantation is the only treatment option. The development of cellular and biotechnologies offers a new solution-the use of lung organoids for transplantation in such patients. Here, we review types of lung organoids, methods of their production and characterization, and experimental works on transplantation in vivo. These results show the promise of work in this direction. Despite the current problems associated with a low degree of cell engraftment, immune response, and insufficient differentiation, we are confident that organoid transplantation will find it is clinical application.

Exploiting the potential of lung stem cells to develop pro-regenerative therapies

Acute and chronic lung diseases are a leading cause of morbidity and mortality globally. Unfortunately, these diseases are increasing in frequency and we have limited treatment options for severe lung diseases. New therapies are needed that not only treat symptoms or slow disease progression, but also enable the regeneration of functional lung tissue. Both airways and alveoli contain populations of epithelial stem cells with the potential to self-renew and produce differentiated progeny. Understanding the mechanisms that determine the behaviour of these cells, and their interactions with their niches, will allow future generations of respiratory therapies that protect the lungs from disease onset, promote regeneration from endogenous stem cells or enable regeneration through the delivery of exogenous cells. This review summarises progress towards each of these goals, highlighting the challenges and opportunities of developing pro-regenerative (bio)pharmaceutical, gene and cell therapies for respiratory diseases.

Examination of the role of necroptotic damage-associated molecular patterns in tissue fibrosis

Fibrosis is defined as the abnormal and excessive deposition of extracellular matrix (ECM) components, which leads to tissue or organ dysfunction and failure. However, the pathological mechanisms underlying fibrosis remain unclear. The inflammatory response induced by tissue injury is closely associated with tissue fibrosis. Recently, an increasing number of studies have linked necroptosis to inflammation and fibrosis. Necroptosis is a type of preprogrammed death caused by death receptors, interferons, Toll-like receptors, intracellular RNA and DNA sensors, and other mediators. These activate receptor-interacting protein kinase (RIPK) 1, which recruits and phosphorylates RIPK3. RIPK3 then phosphorylates a mixed lineage kinase domain-like protein and causes its oligomerization, leading to rapid plasma membrane permeabilization, the release of cellular contents, and exposure of damage-associated molecular patterns (DAMPs). DAMPs, as inflammatory mediators, are involved in the loss of balance between extensive inflammation and tissue regeneration, leading to remodeling, the hallmark of fibrosis. In this review, we discuss the role of necroptotic DAMPs in tissue fibrosis and highlight the inflammatory responses induced by DAMPs in tissue ECM remodeling. By summarizing the existing literature on this topic, we underscore the gaps in the current research, providing a framework for future investigations into the relationship among necroptosis, DAMPs, and fibrosis, as well as a reference for later transformation into clinical treatment.

Molecular Insight into the Therapeutic Effects of Stem Cell-Derived Exosomes in Respiratory Diseases and the Potential for Pulmonary Delivery

Respiratory diseases are the cause of millions of deaths annually around the world. Despite the recent growth of our understanding of underlying mechanisms contributing to the pathogenesis of lung diseases, most therapeutic approaches are still limited to symptomatic treatments and therapies that only delay disease progression. Several clinical and preclinical studies have suggested stem cell (SC) therapy as a promising approach for treating various lung diseases. However, challenges such as the potential tumorigenicity, the low survival rate of the SCs in the recipient body, and difficulties in cell culturing and storage have limited the applicability of SC therapy. SC-derived extracellular vesicles (SC-EVs), particularly SC-derived exosomes (SC-Exos), exhibit most therapeutic properties of stem cells without their potential drawbacks. Similar to SCs, SC-Exos exhibit immunomodulatory, anti-inflammatory, and antifibrotic properties with the potential to be employed in the treatment of various inflammatory and chronic respiratory diseases. Furthermore, recent studies have demonstrated that the microRNA (miRNA) content of SC-Exos may play a crucial role in the therapeutic potential of these exosomes. Several studies have investigated the administration of SC-Exos via the pulmonary route, and techniques for SCs and SC-Exos delivery to the lungs by intratracheal instillation or inhalation have been developed. Here, we review the literature discussing the therapeutic effects of SC-Exos against respiratory diseases and advances in the pulmonary route of delivery of these exosomes to the damaged tissues.

Pulmonary Mesenchymal Stem Cells in Mild Cases of COVID-19 Are Dedicated to Proliferation; In Severe Cases, They Control Inflammation, Make Cell Dispersion, and Tissue Regeneration

Mesenchymal stem cells (MSCs) are multipotent adult stem cells present in virtually all tissues; they have potent self-renewal capacity and differentiate into multiple cell types. For many reasons, these cells are a promising therapeutic alternative to treat patients with severe COVID-19 and pulmonary post-COVID sequelae. These cells are not only essential for tissue regeneration; they can also alter the pulmonary environment through the paracrine secretion of several mediators. They can control or promote inflammation, induce other stem cells differentiation, restrain the virus load, and much more. In this work, we performed single-cell RNA-seq data analysis of MSCs in bronchoalveolar lavage samples from control individuals and COVID-19 patients with mild and severe clinical conditions. When we compared samples from mild cases with control individuals, most genes transcriptionally upregulated in COVID-19 were involved in cell proliferation. However, a new set of genes with distinct biological functions was upregulated when we compared severely affected with mild COVID-19 patients. In this analysis, the cells upregulated genes related to cell dispersion/migration and induced the γ-activated sequence (GAS) genes, probably triggered by IFNGR1 and IFNGR2. Then, IRF-1 was upregulated, one of the GAS target genes, leading to the interferon-stimulated response (ISR) and the overexpression of many signature target genes. The MSCs also upregulated genes involved in the mesenchymal-epithelial transition, virus control, cell chemotaxis, and used the cytoplasmic RNA danger sensors RIG-1, MDA5, and PKR. In a non-comparative analysis, we observed that MSCs from severe cases do not express many NF-κB upstream receptors, such as Toll-like (TLRs) TLR-3, -7, and -8; tumor necrosis factor (TNFR1 or TNFR2), RANK, CD40, and IL-1R1. Indeed, many NF-κB inhibitors were upregulated, including PPP2CB, OPTN, NFKBIA, and FHL2, suggesting that MSCs do not play a role in the "cytokine storm" observed. Therefore, lung MSCs in COVID-19 sense immune danger and act protectively in concert with the pulmonary environment, confirming their therapeutic potential in cell-based therapy for COVID-19. The transcription of MSCs senescence markers is discussed.

Mesenchymal Stromal Cells for the Treatment of Interstitial Lung Disease in Children: A Look from Pediatric and Pediatric Surgeon Viewpoints

Mesenchymal stromal cells (MSCs) have been proposed as a potential therapy to treat congenital and acquired lung diseases. Due to their tissue-regenerative, anti-fibrotic, and immunomodulatory properties, MSCs combined with other therapy or alone could be considered as a new approach for repair and regeneration of the lung during disease progression and/or after post- surgical injury. Children interstitial lung disease (chILD) represent highly heterogeneous rare respiratory diseases, with a wild range of age of onset and disease expression. The chILD is characterized by inflammatory and fibrotic changes of the pulmonary parenchyma, leading to gas exchange impairment and chronic respiratory failure associated with high morbidity and mortality. The therapeutic strategy is mainly based on the use of corticosteroids, hydroxychloroquine, azithromycin, and supportive care; however, the efficacy is variable, and their long-term use is associated with severe toxicity. The role of MSCs as treatment has been proposed in clinical and pre-clinical studies. In this narrative review, we report on the currently available on MSCs treatment as therapeutical strategy in chILD. The progress into the therapy of respiratory disease in children is mandatory to ameliorate the prognosis and to prevent the progression in adult age. Cell therapy may be a future therapy from both a pediatric and pediatric surgeon's point of view.

Inhaled nano-based therapeutics for inflammatory lung diseases: Recent advances and future prospects

Inflammatory lung diseases related morbidity and mortality impose a significant financial burden. Inflammation is a hallmark of many diseases of the respiratory system which is directly or indirectly linked to adverse health conditions, air pollution, rapid lifestyle changes, and regular outbreaks of microbial infections. The unique anatomical and physiological features of the lungs make them an ideal target organ in the treatment of inflammatory respiratory disease and with the help of inhaled therapy lungs can be targeted directly. The principal objective of this review is to present the comprehensive role of inhaled nano-based therapeutics such as liposomes, niosomes, nanoparticles, nanoemulsion, nanosuspension, and exosomes in the treatment and management of inflammatory respiratory diseases. Inhaled nanomedicines provide targeted diagnosis and treatment, improved drug solubility and distribution, prevent first-pass hepatic metabolism, improved patient compliance, and reduced drug side effects. They overcome several biological barriers in the human body and provide immediate, and quick-onset of action. Future research should be focused on improving the therapeutic efficiency of inhaled nanocarriers and to carry out in-depth mechanistic studies to translate current scientific knowledge for the efficient management of inflammatory lung diseases with minimal or no toxicity.

Stem cell-based therapy for COVID-19 and ARDS: a systematic review

Despite global efforts to establish effective interventions for coronavirus disease 2019 (COVID-19) and its major complications, such as acute respiratory distress syndrome (ARDS), the treatment remains mainly supportive. Hence, identifying an effective and safe therapy for severe COVID-19 is critical for saving lives. A significant number of cell-based therapies have been through clinical investigation. In this study, we performed a systematic review of clinical studies investigating different types of stem cells as treatments for COVID-19 and ARDS to evaluate the safety and potential efficacy of cell therapy. The literature search was performed using PubMed, Embase, and Scopus. Among the 29 studies, there were eight case reports, five Phase I clinical trials, four pilot studies, two Phase II clinical trials, one cohort, and one case series. Among the clinical studies, 21 studies used cell therapy to treat COVID-19, while eight studies investigated cell therapy as a treatment for ARDS. Most of these (75%) used mesenchymal stem cells (MSCs) to treat COVID-19 and ARDS. Findings from the analyzed articles indicate a positive impact of stem cell therapy on crucial immunological and inflammatory processes that lead to lung injury in COVID-19 and ARDS patients. Additionally, among the studies, there were no reported deaths causally linked to cell therapy. In addition to standard care treatments concerning COVID-19 management, there has been supportive evidence towards adjuvant therapies to reduce mortality rates and improve recovery of care treatment. Therefore, MSCs treatment could be considered a potential candidate for adjuvant therapy in moderate-to-severe COVID-19 cases and compassionate use.

Mesenchymal Stem Cells in the Treatment of COVID-19, a Promising Future

Mesenchymal stem cells (MSCs) are multipotent adult stem cells present in virtually all tissues; they have a potent self-renewal capacity and can differentiate into multiple cell types. They also affect the ambient tissue by the paracrine secretion of numerous factors in vivo, including the induction of other stem cells’ differentiation. In vitro, the culture media supernatant is named secretome and contains soluble molecules and extracellular vesicles that retain potent biological function in tissue regeneration. MSCs are considered safe for human treatment; their use does not involve ethical issues, as embryonic stem cells do not require genetic manipulation as induced pluripotent stem cells, and after intravenous injection, they are mainly found in the lugs. Therefore, these cells are currently being tested in various preclinical and clinical trials for several diseases, including COVID-19. Several affected COVID-19 patients develop induced acute respiratory distress syndrome (ARDS) associated with an uncontrolled inflammatory response. This condition causes extensive damage to the lungs and may leave serious post-COVID-19 sequelae. As the disease may cause systemic alterations, such as thromboembolism and compromised renal and cardiac function, the intravenous injection of MSCs may be a therapeutic alternative against multiple pathological manifestations. In this work, we reviewed the literature about MSCs biology, focusing on their function in pulmonary regeneration and their use in COVID-19 treatment.

Effect of Hyaluronic Acid on the Differentiation of Mesenchymal Stem Cells into Mature Type II Pneumocytes

Hyaluronic acid (HA) is an essential component of the extracellular matrix (ECM) of the healthy lung, playing an important role in the structure of the alveolar surface stabilizing the surfactant proteins. Alveolar type II (ATII) cells are the fundamental element of the alveolus, specializing in surfactant production. ATII cells represent the main target of lung external lesion and a cornerstone in the repair process of pulmonary damage. In this context, knowledge of the factors influencing mesenchymal stem cell (MSC) differentiation in ATII cells is pivotal in fulfilling therapeutic strategies based on MSCs in lung regenerative medicine. To achieve this goal, the role of HA in promoting the differentiation of MSCs in mature Type II pneumocytes capable of secreting pulmonary surfactant was evaluated. Results demonstrated that HA, at a specific molecular weight can greatly increase the expression of lung surfactant protein, indicating the ability of HA to influence MSC differentiation in ATII cells.

Cellular Therapy for the Treatment of Paediatric Respiratory Disease

Respiratory disease is the leading cause of death in children under the age of 5 years old. Currently available treatments for paediatric respiratory diseases including bronchopulmonary dysplasia, asthma, cystic fibrosis and interstitial lung disease may ameliorate symptoms but do not offer a cure. Cellular therapy may offer a potential cure for these diseases, preventing disease progression into adulthood. Induced pluripotent stem cells, mesenchymal stromal cells and their secretome have shown great potential in preclinical models of lung disease, targeting the major pathological features of the disease. Current research and clinical trials are focused on the adult population. For cellular therapies to progress from preclinical studies to use in the clinic, optimal cell type dosage and delivery methods need to be established and confirmed. Direct delivery of these therapies to the lung as aerosols would allow for lower doses with a higher target efficiency whilst avoiding potential effect of systemic delivery. There is a clear need for research to progress into the clinic for the treatment of paediatric respiratory disease. Whilst research in the adult population forms a basis for the paediatric population, varying disease pathology and anatomical differences in paediatric patients means a paediatric-centric approach must be taken.

Soluble factors of mesenchimal stem cells (FS-MSC) as a potential tool to reduce inflammation in donor's lungs after hypovolemic shock

OBJECTIVE

The shortage of viable lungs is still a major obstacle for transplantation. Trauma victims who represent potential lung donors commonly present hypovolemic shock leading to pulmonary inflammation and deterioration and rejection after transplantation. Seeking to improve lung graft, new approaches to donor treatment have been tested. This study focuses on treatment with mesenchymal stem cells (MSCs) or soluble factors produced by MSCs (FS-MSC) using a rat model for lung donors after hemorrhagic shock.

METHODS

Forty-eight rats were divided into four groups: Sham (n=12), animals without induction of hypovolemic shock; Shock (n=12), animals submitted to hypovolemic shock (mean arterial pressure 40 mmHg); MSC (n=12), animals submitted to hypovolemic shock and treated with MSCs, and FS (n=12), animals submitted to hypovolemic shock and treated with FS-MSC. The animals were subjected to a 50-minute hypovolemic shock (40 mmHg) procedure. The treated animals were monitored for 115 minutes. We performed histopathology of lung tissue and quantification of inflammatory markers (TNF-α, IL-1β, IL-6, IL-10, iCAM and vCAM) in lung tissue and peripheral blood leukocytes (PBLs).

RESULTS

Hemorrhagic shock resulted in higher PBLs and neutrophil infiltrate in the lungs. FS animals had lower neutrophil density comparing with Shock and MSC animals (p<0.001). No differences in the cytokine levels in lung tissue were observed between the groups.

CONCLUSIONS

The lungs of rats submitted to hemorrhagic shock and treated with FS-MSC showed reduced inflammation indicated in a decrease in lung neutrophil infiltrate.

Core-shell hydrogel microfiber-expanded pluripotent stem cell-derived lung progenitors applicable to lung reconstruction in vivo

Lung transplantation is the only treatment available for end-stage lung diseases; however, donor shortage is a global issue. The use of human pluripotent stem cells (hPSCs) for organ regeneration is a promising approach. Nevertheless, methods for the expansion of isolated hPSC-derived lung progenitors (hLPs) for transplantation purposes have not yet been reported. Herein, we established an expansion system of hLPs based on their three-dimensional culture in core-shell hydrogel microfibers, that ensures the maintenance of their bipotency for differentiation into alveolar and airway epithelial cells including alveolar type II (AT2) cells. Further, we developed an efficient in vivo transplantation method using an endoscope-assisted transtracheal administration system; the successful engraftment and in vivo differentiation of hLPs into alveolar epithelial cells (incorporated into the alveoli) was observed. Importantly, expanded hLPs in the context of microfibers were successfully transplanted into the murine lungs, opening avenues for cell-based therapies of lung diseases. Therefore, our novel method has potential regenerative medicine applications; additionally, the high-quality hLPs and AT2 cells generated via the microfiber-based technology are valuable for drug discovery purposes.

Extracellular vesicles derived from umbilical cord mesenchymal stromal cells alleviate pulmonary fibrosis by means of transforming growth factor-β signaling inhibition

BACKGROUND

Pulmonary fibrosis (PF), the end point of interstitial lung diseases, is characterized by myofibroblast over differentiation and excessive extracellular matrix accumulation, leading to progressive organ dysfunction and usually a terminal outcome. Studies have shown that umbilical cord-derived mesenchymal stromal cells (uMSCs) could alleviate PF; however, the underlying mechanism remains to be elucidated.

METHODS

The therapeutic effects of uMSC-derived extracellular vesicles (uMSC-EVs) on PF were evaluated using bleomycin (BLM)-induced mouse models. Then, the role and mechanism of uMSC-EVs in inhibiting myofibroblast differentiation were investigated in vivo and in vitro.

RESULTS

Treatment with uMSC-EVs alleviated the PF and enhanced the proliferation of alveolar epithelial cells in BLM-induced mice, thus improved the life quality, including the survival rate, body weight, fibrosis degree, and myofibroblast over differentiation of lung tissue. Moreover, these effects of uMSC-EVs on PF are likely achieved by inhibiting the transforming growth factor-β (TGF-β) signaling pathway, evidenced by decreased expression levels of TGF-β2 and TGF-βR2. Using mimics of uMSC-EV-specific miRNAs, we found that miR-21 and miR-23, which are highly enriched in uMSC-EVs, played a critical role in inhibiting TGF-β2 and TGF-βR2, respectively.

CONCLUSION

The effects of uMSCs on PF alleviation are likely achieved via EVs, which reveals a new role of uMSC-EV-derived miRNAs, opening a novel strategy for PF treatment in the clinical setting.

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.

Stem cells and COVID-19: are the human amniotic cells a new hope for therapies against the SARS-CoV-2 virus?

A new coronavirus respiratory disease (COVID-19) caused by the SARS-CoV-2 virus, surprised the entire world, producing social, economic, and health problems. The COVID-19 triggers a lung infection with a multiple proinflammatory cytokine storm in severe patients. Without effective and safe treatments, COVID-19 has killed thousands of people, becoming a pandemic. Stem cells have been suggested as a therapy for lung-related diseases. In particular, mesenchymal stem cells (MSCs) have been successfully tested in some clinical trials in patients with COVID-19. The encouraging results positioned MSCs as a possible cell therapy for COVID-19. The amniotic membrane from the human placenta at term is a valuable stem cell source, including human amniotic epithelial cells (hAECs) and human mesenchymal stromal cells (hAMSCs). Interestingly, amnion cells have immunoregulatory, regenerative, and anti-inflammatory properties. Moreover, hAECs and hAMSCs have been used both in preclinical studies and in clinical trials against respiratory diseases. They have reduced the inflammatory response and restored the pulmonary tissue architecture in lung injury in vivo models. Here, we review the existing data about the stem cells use for COVID-19 treatment, including the ongoing clinical trials. We also consider the non-cellular therapies that are being applied. Finally, we discuss the human amniotic membrane cells use in patients who suffer from immune/inflammatory lung diseases and hypothesize their possible use as a successful treatment against COVID-19.

Targeting mesenchymal stem cell therapy for severe pneumonia patients

Pneumonia is the inflammation of the lungs and it is the world's leading cause of death for children under 5 years of age. The latest coronavirus disease 2019 (COVID-19) virus is a prominent culprit to severe pneumonia. With the pandemic running rampant for the past year, more than 1590000 deaths has occurred worldwide up to December 2020 and are substantially attributable to severe pneumonia and induced cytokine storm. Effective therapeutic approaches in addition to the vaccines and drugs under development are hence greatly sought after. Therapies harnessing stem cells and their derivatives have been established by basic research for their versatile capacity to specifically inhibit inflammation due to pneumonia and prevent alveolar/pulmonary fibrosis while enhancing antibacterial/antiviral immunity, thus significantly alleviating the severe clinical conditions of pneumonia. In recent clinical trials, mesenchymal stem cells have shown effectiveness in reducing COVID-19-associated pneumonia morbidity and mortality; positioning these cells as worthy candidates for combating one of the greatest challenges of our time and shedding light on their prospects as a next-generation therapy to counter future challenges.

Therapeutic Potential of Mesenchymal Stem Cells and Their Products in Lung Diseases-Intravenous Administration versus Inhalation

The number of publications studying the therapeutic use of stem cells has steadily increased since 2000. Compared to other applications, there has been little interest in the evaluation of mesenchymal stem cells (MSCs) and MSC-derived products (mostly extracellular vesicles) for the treatment of respiratory diseases. Due to the lack of efficient treatments for acute respiratory distress syndrome caused by infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the action of MSCs has also been studied. This review describes mode of action and use of MSCs and MSC-derived products in the treatment of lung diseases including the respective advantages and limitations of the products. Further, issues related to standardized production are addressed. Administration by inhalation of MSCs, compared to intravenous injection, could decrease cell damage by shear stress, eliminate the barrier to reach target cells in the alveoli, prevent thrombus formation in the pulmonary vasculature and retention in filter for extracorporeal membrane oxygenation. There is more feasible to deliver extracellular vesicles than MSCs with inhalers, offering the advantage of non-invasive and repeated administration by the patient. Major obstacles for comparison of results are heterogeneity of the products, differences in the treatment protocols and small study cohorts.

Regenerative Medicine in COVID-19 Treatment: Real Opportunities and Range of Promises

Novel coronavirus disease (COVID-19) has attracted much attention around the world due to its rapid transmission among humans and relatively high mortality rate. Studies are increasing to find the best therapeutic approach for the disease and its management. Regenerative medicine offers various cell-tissue therapeutics and related products, such as stem cell therapy, natural killer (NK) cell therapy, Chimeric antigen receptor (CAR) T cell therapy, exosomes, and tissue products. Interestingly, mesenchymal stem cells (MSCs) can reduce inflammatory symptoms and protect against cytokine storm, which critically contributes to the COVID-19 progression. Notably, having the potentials to exert cytotoxic effects on infected cells and induce interferon production probably make NK cells a candidate for COVID-19 cell therapy. Besides, exosomes are one of the crucial products of cells that can exert therapeutic effects through the induction of immune responses and neutralizing antibody titers. The paper aims to briefly consider current options for COVID-19 therapy to show that there is no specific cure for COVID-19, and then assess the real opportunities and range of promises regenerative medicine can provide for specific treatment of COVID-19. Graphical Abstract Therapeutic Potential of Regenerative Medicine against COVID19.

Endoscopic atomization of mesenchymal stromal cells: in vitro study for local cell therapy of the lungs

BACKGROUND AIMS

Cell-based therapies of pulmonary diseases with mesenchymal stromal cells (MSCs) are increasingly under experimental investigation. In most of these, MSCs are administered intravenously or by direct intratracheal instillation. A parallel approach is to administer the cells into the lung by endoscopic atomization (spraying). In a previous study, the authors developed a flexible endoscopic atomization device that allows administration of respiratory epithelial cells in the lungs with high survival.

METHODS

In this study, the authors evaluated the feasibility of spraying MSCs with two different endoscopic atomization devices (air and pressure atomization). Following atomization, cell viability was evaluated with live/dead staining. Subsequent effects on cytotoxicity, trilineage differentiation and expression of MSC-specific markers as well as on MSC metabolic activity and morphology were analyzed for up to 7 days.

RESULTS

MSC viability immediately after spraying and subsequent metabolic activity for 7 days was not influenced by either of the devices. Slightly higher cytotoxicity rates could be observed for pressure-atomized compared with control and air-atomized MSCs over 7 days. Flow cytometry revealed no changes in characteristic MSC cell surface marker expression, and morphology remained unchanged. Standard differentiation into osteocytes, chondrocytes and adipocytes was inducible after atomization.

CONCLUSIONS

In the literature, a minimal survival of 50% was previously defined as the cutoff value for successful cell atomization. This is easily met with both of the authors' devices, with more than 90% survival. Thus, there is a potential role for atomization in intrapulmonary MSC-based cell therapies, as it is a feasible and easily utilizable approach based on clinically available equipment.

MSC Based Therapies to Prevent or Treat BPD-A Narrative Review on Advances and Ongoing Challenges

Bronchopulmonary dysplasia (BPD) remains one of the most devastating consequences of preterm birth resulting in life-long restrictions in lung function. Distorted lung development is caused by its inflammatory response which is mainly provoked by mechanical ventilation, oxygen toxicity and bacterial infections. Dysfunction of resident lung mesenchymal stem cells (MSC) represents one key hallmark that drives BPD pathology. Despite all progress in the understanding of pathomechanisms, therapeutics to prevent or treat BPD are to date restricted to a few drugs. The limited therapeutic efficacy of established drugs can be explained by the fact that they fail to concurrently tackle the broad spectrum of disease driving mechanisms and by the huge overlap between distorted signal pathways of lung development and inflammation. The great enthusiasm about MSC based therapies as novel therapeutic for BPD arises from the capacity to inhibit inflammation while simultaneously promoting lung development and repair. Preclinical studies, mainly performed in rodents, raise hopes that there will be finally a broadly acting, efficient therapy at hand to prevent or treat BPD. Our narrative review gives a comprehensive overview on preclinical achievements, results from first early phase clinical studies and challenges to a successful translation into the clinical setting.

Mesenchymal Stromal Cell‐Mediated Treatment of Local and Systemic Inflammation through the Triggering of an Anti‐Inflammatory Response

The emergence of cell‐based therapeutics, specifically the use of mesenchymal stromal/stem cells (MSCs), stands to significantly affect the future of targeted drug delivery technologies. MSCs represent a unique cell type, offering more than only regenerative potential but also site‐specific inflammatory targeting and tissue infiltration. In this study, a versatile multicomponent delivery platform, combining MSC tropism with multistage nanovector (MSV)‐mediated payload delivery, is debuted. It is demonstrated that the incorporation of drug‐loaded MSVs bestows MSCs with the ability to transport anti‐inflammatory payloads, achieving a fivefold increase in payload release without negatively impacting cellular functions, viability, extravasation, and inflammatory homing. When incorporated within MSCs, MSVs avoid rapid sequestration by filtering organs and conserve a 15‐fold increase in local inflammatory targeting compared to healthy ears. Furthermore, this MSC‐mediated MSV platform (M&Ms) rapidly triggers a 4.5‐fold reduction of local inflammation compared to free drug and extends survival to 100% of treated mice in a lethal model of systemic inflammation.

Transplantation of Mesenchymal Stem Cells: A Potential Adjuvant Therapy for COVID-19

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative pathogen for coronavirus disease-2019 (COVID-19), which has posed an increasing serious public health threat. However, still there are no approved antiviral agents or vaccines available yet. Mesenchymal stem cells (MSCs) are emerging as a novel promising adjuvant therapy for the attenuation of COVID-19 based on its putative pathogenesis. MSCs may exert anti-inflammatory, immunomodulatory, anti-apoptotic, as well as regenerative effects through a series of mechanisms. Remarkably, MSCs may be resistant to virus infection, which is fundamental for the treatment of COVID-19. The beneficial therapeutic effects of MSCs have been preliminarily proved to be safe and efficacious for the treatment of COVID-19 in current clinical trials. This work aims to review the beneficial effects of MSCs in treating ALI/ARDS, which provides novel insight into the potential therapeutic strategies against COVID-19. However, further research is warranted regarding both safety and efficacy of MSCs.

The Coronavirus Pandemic (SARS-CoV-2): New Problems Demand New Solutions, the Alternative of Mesenchymal (Stem) Stromal Cells

Mesenchymal (stem) stromal cells (MSC) can be a therapeutic alternative for COVID-19 considering their anti-inflammatory, regenerative, angiogenic, and even antimicrobial capacity. Preliminary data point to therapeutic interest of MSC for patients with COVID-19, and their effect seems based on the MSC's ability to curb the cytokine storm caused by COVID-19. In fact, promising clinical studies using MSC to treat COVID-19, are currently underway. For this reason, now is the time to firmly consider new approaches to MSC research that addresses key issues, like selecting the most optimal type of MSC for each indication, assuming the heterogeneity of the donor-dependent MSC and the biological niche where MSC are located.

G-CSF Inhibits Pulmonary Fibrosis by Promoting BMSC Homing to the Lungs via SDF-1/CXCR4 Chemotaxis

Bone marrow mesenchymal stem cells (BMSCs) have multi-lineage differentiation potential and play an important role in tissue repair. Studies have shown that BMSCs gather at the injured tissue site after granulocyte-colony stimulating factor (G-CSF) administration. In this study, we first investigated whether G-CSF could promote BMSC homing to damaged lung tissue induced by bleomycin (BLM) and then investigated whether SDF-1/CXCR4 chemotaxis might be involved in this process. Next, we further studied the potential inhibitory effect of G-CSF administration in mice with lung fibrosis induced by bleomycin. We examined both the antifibrotic effects of G-CSF in mice with bleomycin-induced pulmonary fibrosis in vivo and its effects on the proliferation, differentiation and chemotactic movement of cells in vitro. Flow cytometry, real-time PCR, transwell and Cell Counting Kit-8 (CCK-8) assays were used in this study. The results showed that both preventative and therapeutic G-CSF administration could significantly inhibit bleomycin-induced pulmonary fibrosis. G-CSF enhanced BMSC migration to lung tissues, but this effect could be alleviated by AMD3100, which blocked the SDF-1/CXCR4 axis. We also found that BMSCs could inhibit fibroblast proliferation and transdifferentiation into myofibroblasts through paracrine actions. In conclusion, G-CSF exerted antifibrotic effects in bleomycin-induced lung fibrosis, in part by promoting BMSC homing to injured lung tissues via SDF-1/CXCR4 chemotaxis.

Placenta Stem/Stromal Cell-Derived Extracellular Vesicles for Potential Use in Lung Repair

Many acute and chronic lung injuries are incurable and rank as the fourth leading cause of death globally. While stem cell treatment for lung injuries is a promising approach, there is growing evidence that the therapeutic efficacy of stem cells originates from secreted extracellular vesicles (EVs). Consequently, EVs are emerging as next-generation therapeutics. While EVs are extensively researched for diagnostic applications, their therapeutic potential to promote tissue repair is not fully elucidated. By housing and delivering tissue-repairing cargo, EVs refine the cellular microenvironment, modulate inflammation, and ultimately repair injury. Here, the potential use of EVs derived from two placental mesenchymal stem/stromal cell (MSC) lines is presented; a chorionic MSC line (CMSC29) and a decidual MSC cell line (DMSC23) for applications in lung diseases. Functional analyses using in vitro models of injury demonstrate that these EVs have a role in ameliorating injuries caused to lung cells. It is also shown that EVs promote repair of lung epithelial cells. This study is fundamental to advancing the field of EVs and to unlock the full potential of EVs in regenerative medicine.

Bioengineering of Pulmonary Epithelium With Preservation of the Vascular Niche

The shortage of transplantable donor organs directly affects patients with end-stage lung disease, for which transplantation remains the only definitive treatment. With the current acceptance rate of donor lungs of only 20%, rescuing even one half of the rejected donor lungs would increase the number of transplantable lungs threefold, to 60%. We review recent advances in lung bioengineering that have potential to repair the epithelial and vascular compartments of the lung. Our focus is on the long-term support and recovery of the lung ex vivo, and the replacement of defective epithelium with healthy therapeutic cells. To this end, we first review the roles of the lung epithelium and vasculature, with focus on the alveolar-capillary membrane, and then discuss the available and emerging technologies for ex vivo bioengineering of the lung by decellularization and recellularization. While there have been many meritorious advances in these technologies for recovering marginal quality lungs to the levels needed to meet the standards for transplantation – many challenges remain, motivating further studies of the extended ex vivo support and interventions in the lung. We propose that the repair of injured epithelium with preservation of quiescent vasculature will be critical for the immediate blood supply to the lung and the lung survival and function following transplantation.

Mesenchymal Stromal Cell Secretome for Severe COVID-19 Infections: Premises for the Therapeutic Use

From the end of 2019, the world population has been faced the spread of the novel coronavirus SARS-CoV-2 responsible for COVID-19 infection. In approximately 14% of the patients affected by the novel coronavirus, the infection progresses with the development of pneumonia that requires mechanical ventilation. At the moment, there is no specific antiviral treatment recommended for the COVID-19 pandemic and the therapeutic strategies to deal with the infection are only supportive. In our opinion, mesenchymal stem cell secretome could offer a new therapeutic approach in treating COVID-19 pneumonia, due to the broad pharmacological effects it shows, including anti-inflammatory, immunomodulatory, regenerative, pro-angiogenic and anti-fibrotic properties.

MSC Based Therapies-New Perspectives for the Injured Lung

Chronic lung diseases pose a tremendous global burden. At least one in four people suffer from severe pulmonary sequelae over the course of a lifetime. Despite substantial improvements in therapeutic interventions, persistent alleviation of clinical symptoms cannot be offered to most patients affected to date. Despite broad discrepancies in origins and pathomechanisms, the important disease entities all have in common the pulmonary inflammatory response which is central to lung injury and structural abnormalities. Mesenchymal stem cells (MSC) attract particular attention due to their broadly acting anti-inflammatory and regenerative properties. Plenty of preclinical studies provided congruent and convincing evidence that MSC have the therapeutic potential to alleviate lung injuries across ages. These include the disease entities bronchopulmonary dysplasia, asthma and the different forms of acute lung injury and chronic pulmonary diseases in adulthood. While clinical trials are so far restricted to pioneering trials on safety and feasibility, preclinical results point out possibilities to boost the therapeutic efficacy of MSC application and to take advantage of the MSC secretome. The presented review summarizes the most recent advances and highlights joint mechanisms of MSC action across disease entities which provide the basis to timely tackle this global disease burden.

CD90+CD146+ identifies a pulmonary mesenchymal cell subtype with both immune modulatory and perivascular-like function in postnatal human lung

Our understanding of mesenchymal cell subsets and their function in human lung affected by aging and in certain disease settings remains poorly described. We use a combination of flow cytometry, prospective cell-sorting strategies, confocal imaging, and modeling of microvessel formation using advanced microfluidic chip technology to characterize mesenchymal cell subtypes in human postnatal and adult lung. Tissue was obtained from patients undergoing elective surgery for congenital pulmonary airway malformations (CPAM) and other airway abnormalities including chronic obstructive pulmonary disease (COPD). In microscopically normal postnatal human lung, there was a fivefold higher mesenchymal compared with epithelial (EpCAM⁺) fraction, which diminished with age. The mesenchymal fraction composed of CD90⁺ and CD90⁺CD73⁺ cells was enriched in CXCL12 and platelet-derived growth factor receptor-α (PDGFRα) and located in close proximity to EpCAM⁺ cells in the alveolar region. Surprisingly, alveolar organoids generated from EpCAM⁺ cells supported by CD90⁺ subset were immature and displayed dysplastic features. In congenital lung lesions, cystic air spaces and dysplastic alveolar regions were marked with an underlying thick interstitium composed of CD90⁺ and CD90⁺PDGFRα⁺ cells. In postnatal lung, a subset of CD90⁺ cells coexpresses the pericyte marker CD146 and supports self-assembly of perfusable microvessels. CD90⁺CD146⁺ cells from COPD patients fail to support microvessel formation due to fibrinolysis. Targeting the plasmin-plasminogen system during microvessel self-assembly prevented fibrin gel degradation, but microvessels were narrower and excessive contraction blocked perfusion. These data provide important new information regarding the immunophenotypic identity of key mesenchymal lineages and their change in a diverse setting of congenital lung lesions and COPD.

Adipose Tissue-Derived Mesenchymal Stem Cells Protect Against Amiodarone-Induced Lung Injury in Rats

Pulmonary fibrosis (PF) is a progressive and irreversible lung disease, characterized by poor prognosis with limited treatment options. Mesenchymal stem cells (MSCs) are multi-potent cells having the ability to self-renew and differentiate into multiple tissues, thus considered a novel treatment option. The present study aimed to investigate the possible antifibrotic effect of undifferentiated adipose tissue-derived mesenchymal stem cell (AD-MSC) therapy on PF experimentally induced in rats using amiodarone (AMD). AMD (30 mg/kg) was given orally, once daily for 12 consecutive weeks to induce lung fibrosis. Following the confirmation of lung damage with histopathological examination, AD-MSCs (2 × 10⁶ and 4 × 10⁶ undifferentiated MSCs) were injected once intravenously, followed by 2 months for treatment. AMD induced focal fibroblastic cells proliferation in the peribronchiolar tissue, as well as in between the collapsed emphysematous alveoli. Also, AMD significantly increased serum and lung homogenate fibroblast growth factor-7 (FGF7), Clara cell protein-16 (CC16), and cytokeratin -19 (CK19) levels, as well as the expression of both iNOS and NFкB in the lung alveoli. Moreover, AMD caused excessive collagen deposition and increased alpha smooth muscle actin (α-SMA) expression. All findings significantly regressed on stem cell therapy in both doses, with superior effect of the high dose, providing evidence that adipose tissue-derived MSCs could be a promising approach for the treatment of PF. Graphical Abstract.

Allogeneic mesenchymal stromal cells: Novel therapeutic option for mutated FLNA-associated respiratory failure in the pediatric setting

BACKGROUND

Mesenchymal stromal cell (MSC)-mediated therapeutic effects have been observed in the treatment of lung diseases. For the first time, this treatment was used as rescue therapy in a pediatric patient with a life-threatening respiratory syndrome associated with the filamin A (FLNA) gene mutation.

METHODS

A child with a new pathogenic variant of the FLNA gene c.7391_7403del (p.Val2464AlafsTer5), at the age of 18 months, due to serious and irreversible chronic respiratory failure, was treated with repeated intravenous infusions of allogeneic bone marrow (BM)-MSCs. The child's respiratory condition was monitored. Immunologic studies before each MSC treatment were performed.

RESULTS

No acute adverse events related to the MSC infusions were observed. After the second infusion, the child's respiratory condition progressively improved, with reduced necessity for mechanical ventilation support. A thorax computed tomography (CT) scan showed bilateral recovery of the basal parenchyma, anatomical-functional alignment and aerial penetration improvement. After the first MSC administration, an increase in Th17 and FoxP3⁺ T percentages in the peripheral blood was observed. After the second MSC infusion, a significant rise in the Treg/Th17 ratio was noted, as well as an increased percentage of CD20⁺ /CD19⁺ B lymphocytes and augmented PHA-induced proliferation.

DISCUSSION

MSC infusions are a promising therapeutic modality for patients in respiratory failure, as observed in this pediatric patient with an FLNA mutation. MSCs may have an immunomodulatory effect and thus mitigate lung injury; although in this case, MSC antimicrobial effects may have synergistically impacted the clinical improvements. Further investigations are planned to establish the safety and efficacy of this treatment option for interstitial lung diseases in children.

Mesenchymal Regulation of the Microvascular Niche in Chronic Lung Diseases

The adult lung is comprised of diverse vascular, epithelial, and mesenchymal progenitor cell populations that reside in distinct niches. Mesenchymal progenitor cells (MPCs) are intimately associated with both the epithelium and the vasculature, and new evidence is emerging to describe their functional roles in these niches. Also emerging, following lineage analysis and single cell sequencing, is a new understanding of the diversity of mesenchymal cell subpopulations in the lung. However, several gaps in knowledge remain, including how newly defined MPC lineages interact with cells in the vascular niche and the role of adult lung MPCs during lung repair and regeneration following injury, especially in chronic lung diseases. Here we summarize how the current evidence on MPC regulation of the microvasculature during tissue homeostasis and injury may inform studies on understanding their role in chronic lung disease pathogenesis or repair. © 2019 American Physiological Society. Compr Physiol 9:1431-1441, 2019.

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.

Mesenchymal stem/stromal cell secretome for lung regeneration: The long way through "pharmaceuticalization" for the best formulation

Pulmonary acute and chronic diseases, such as chronic obstructive pulmonary disease, pulmonary fibrosis and pulmonary hypertension, are considered to be major health issues worldwide. Cellular therapies with Mesenchymal Stem Cells (MSCs) offer a new therapeutic approach for chronic and acute lung diseases related to their anti-inflammatory, immunomodulatory, regenerative, pro-angiogenic and anti-fibrotic properties. Such therapeutic effects can be attributed to MSC-secretome, made of free soluble proteins and extracellular vesicles (EVs). This review summarizes the recent findings related to the efficacy and safety of MSC-derived products in pre-clinical models of lung diseases, pointing out the biologically active substances contained into MSC-secretome and their mechanisms involved in tissue regeneration. A perspective view is then provided about the missing steps required for the secretome "pharmaceuticalization" into a high quality, safe and effective medicinal product, as well as the formulation strategies required for EV non-invasive route of administration, such as inhalation.

Predifferentiated amniotic fluid mesenchymal stem cells enhance lung alveolar epithelium regeneration and reverse elastase-induced pulmonary emphysema

INTRODUCTION

Pulmonary emphysema is a major component of chronic obstructive pulmonary disease (COPD). Emphysema progression attributed not only to alveolar structure loss and pulmonary regeneration impairment, but also to excessive inflammatory response, proteolytic and anti-proteolytic activity imbalance, lung epithelial cells apoptosis, and abnormal lung remodeling. To ameliorate lung damage with higher efficiency in lung tissue engineering and cell therapy, pre-differentiating graft cells into more restricted cell types before transplantation could enhance their ability to anatomically and functionally integrate into damaged lung. In this study, we aimed to evaluate the regenerative and repair ability of lung alveolar epithelium in emphysema model by using lung epithelial progenitors which pre-differentiated from amniotic fluid mesenchymal stem cells (AFMSCs).

METHODS

Pre-differentiation of eGFP-expressing AFMSCs to lung epithelial progenitor-like cells (LEPLCs) was established under a modified small airway growth media (mSAGM) for 7-day induction. Pre-differentiated AFMSCs were intratracheally injected into porcine pancreatic elastase (PPE)-induced emphysema mice at day 14, and then inflammatory-, fibrotic-, and emphysema-related indices and pathological changes were assessed at 6 weeks after PPE administration.

RESULTS

An optimal LEPLCs pre-differentiation condition has been achieved, which resulted in a yield of approximately 20% lung epithelial progenitors-like cells from AFMSCs in a 7-day period. In PPE-induced emphysema mice, transplantation of LEPLCs significantly improved regeneration of lung tissues through integrating into the lung alveolar structure, relieved airway inflammation, increased expression of growth factors such as vascular endothelial growth factor (VEGF), and reduced matrix metalloproteinases and lung remodeling factors when compared with mice injected with AFMSCs. Histopathologic examination observed a significant amelioration in DNA damage in alveolar cells, detected by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL), the mean linear intercept, and the collagen deposition in the LEPLC-transplanted groups.

CONCLUSION

Transplantation of predifferentiated AFMSCs through intratracheal injection showed better alveolar regeneration and reverse elastase-induced pulmonary emphysema in PPE-induced pulmonary emphysema mice.

Dissecting the Pharmacodynamics and Pharmacokinetics of MSCs to Overcome Limitations in Their Clinical Translation

Recently, mesenchymal stromal stem cells (MSCs) have been proposed as therapeutic agents because of their promising preclinical features and good safety profile. However, their introduction into clinical practice has been associated with a suboptimal therapeutic profile. In this review, we address the biodistribution of MSCs in preclinical studies with a focus on the current understanding of the pharmacodynamics (PD) and pharmacokinetics (PK) of MSCs as key aspects to overcome unsatisfactory clinical benefits of MSC application. Beginning with evidence of MSC biodistribution and highlighting PK and PD factors, a new PK-PD model is also proposed. According to this theory, MSCs and their released factors are key players in PK, and the efficacy biomarkers are considered relevant for PD in more predictive preclinical investigations. Accounting for the PK-PD relationship in MSC translational research and proposing new models combined with better biodistribution studies could allow realization of the promise of more robust MSC clinical translation.

Mesenchymal Stem Cell-Based Therapy of Inflammatory Lung Diseases: Current Understanding and Future Perspectives

During acute or chronic lung injury, inappropriate immune response and/or aberrant repair process causes irreversible damage in lung tissue and most usually results in the development of fibrosis followed by decline in lung function. Inhaled corticosteroids and other anti-inflammatory drugs are very effective in patients with inflammatory lung disorders, but their long-term use is associated with severe side effects. Accordingly, new therapeutic agents that will attenuate ongoing inflammation and, at the same time, promote regeneration of injured alveolar epithelial cells are urgently needed. Mesenchymal stem cells (MSCs) are able to modulate proliferation, activation, and effector function of all immune cells that play an important role in the pathogenesis of acute and chronic inflammatory lung diseases. In addition to the suppression of lung-infiltrated immune cells, MSCs have potential to differentiate into alveolar epithelial cells in vitro and, accordingly, represent new players in cell-based therapy of inflammatory lung disorders. In this review article, we described molecular mechanisms involved in MSC-based therapy of acute and chronic pulmonary diseases and emphasized current knowledge and future perspectives related to the therapeutic application of MSCs in patients suffering from acute respiratory distress syndrome, pneumonia, asthma, chronic obstructive pulmonary diseases, and idiopathic pulmonary fibrosis.