The vascular nature of lung-resident mesenchymal stem cells

Senescence of lung mesenchymal stem cells of preterm infants by cyclic stretch and hyperoxia via p21

Phenotype distortion of lung resident mesenchymal stem cells (MSC) in preterm infants is a hallmark event in the pathogenesis of bronchopulmonary dysplasia (BPD). Here, we evaluated the impact of cyclic mechanical stretch (CMS) and hyperoxia (HOX). The negative action of HOX on proliferation and cell death was more pronounced at 80% than at 40%. Although the impact of CMS alone was modest, CMS plus HOX displayed the strongest effect sizes. Exposure to CMS and/or HOX induced the downregulation of PDGFRα, and cellular senescence preceded by p21 accumulation. p21 interference interfered with cellular senescence and resulted in aggravated cell death, arguing for a prosurvival mechanism. HOX 40% and limited exposure to HOX 80% prevailed in a reversible phenotype with reuptake of proliferation, while prolonged exposure to HOX 80% resulted in definite MSC growth arrest. Our mechanistic data explain how HOX and CMS induce the effects on MSC phenotype disruption. The results are congruent with the clinical observation that preterm infants requiring supplemental oxygen plus mechanical ventilation are at particular risk for BPD. Although inhibiting p21 is not a feasible approach, limiting the duration and magnitude of the exposures is promising.NEW & NOTEWORTHY Rarefication of lung mesenchymal stem cells (MSC) due to exposure to cyclic mechanical stretch (CMS) during mechanical ventilation with oxygen-rich gas is a hallmark of bronchopulmonary dysplasia in preterm infants, but the pathomechanistic understanding is incomplete. Our studies identify a common signaling mechanism mediated by p21 accumulation, leading to cellular senescence and cell death, most pronounced during the combined exposure with in principle reversible phenotype change depending on strength and duration of exposures.

Activated STING-containing R-EVs from iPSC-derived MSCs promote antitumor immunity

We recently revealed that activated STING is secreted into RAB22A-induced extracellular vesicles (R-EVs) and promotes antitumor immunity in cancer cells. Whether mesenchymal stem cell (MSC)-derived R-EVs containing activated STING can be used as a novel antitumor immunotherapy remains unclear, as MSC-derived EVs are promising cell-free therapeutics due to their superior biocompatibility and safety, as well as low immunogenicity. Here, we report that induced pluripotent stem cell (iPSC)-derived MSCs can generate R-EVs with a size and mechanism of formation that are similar to those of R-EVs produced from cancer cells. Furthermore, these MSC-derived R-EVs containing activated STING induced IFNβ expression in recipient THP-1 monocytes and antitumor immunity in mice. Our findings reveal that the use of MSC-derived R-EVs containing activated STING is a promising cell-free strategy for antitumor immunity.

Non-small cell lung cancer cells and concomitant cancer therapy induce a resistance-promoting phenotype of tumor-associated mesenchymal stem cells

Introduction

The tumor microenvironment gained attraction over the last decades as stromal cells significantly impact on tumor development, progression and metastasis, and immune evasion as well as on cancer therapy resistance. We previously reported that lung-resident mesenchymal stem cells (MSCs) were mobilized and activated in non-small cell lung cancer (NSCLC) progression and could even mediate radiation resistance in co-cultured NSCLC cells.

Methods

We investigated how MSCs were affected by NSCLC cells in combination with cancer (radiation) therapy in indirect co-cultures using tumor-conditioned medium and Transwells or direct three-dimensional NSCLC-MSC spheroid co-cultures in order to unravel the resistance-mediating action of tumor-associated MSCs.

Results

Although no obvious phenotypic and functional alterations in MSCs following NSCLC co-culture could be observed, MSC senescence was induced following co-applied radiotherapy (RT). Global gene expression profiling, in combination with gene set enrichment analysis upon treatment, was used to confirm the senescent phenotype of irradiated MSC and to reveal relevant senescence-associated secretory phenotype (SASP) factors that could meditate NSCLC RT resistance. We identified senescent tumor-associated MSC-derived serine proteinase inhibitor (serpin) E1/PAI1 as potential SASP factor mediating NSCLC progression and RT resistance.

Discussion

Specified intra-tumor-stroma interactions and cell type-specific pro-tumorigenic functions could not only improve lung cancer classification but could even be used for a more precise profiling of individual patients, finally paving an additional way for the discovery of potential drug targets for NSCLC patients.

Multidisciplinary Management Strategies for Long COVID: A Narrative Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused millions of infections to date and has led to a worldwide pandemic. Most patients had a complete recovery from the acute infection, however, a large number of the affected individuals experienced symptoms that persisted more than 3 months after diagnosis. These symptoms most commonly include fatigue, memory difficulties, brain fog, dyspnea, cough, and other less common ones such as headache, chest pain, paresthesias, mood changes, muscle pain, and weakness, skin rashes, and cardiac, endocrine, renal and hepatic manifestations. The treatment of this syndrome remains challenging. A multidisciplinary approach to address combinations of symptoms affecting multiple organ systems has been widely adopted. This narrative review aims to bridge the gap surrounding the broad treatment approaches by providing an overview of multidisciplinary management strategies for the most common long COVID conditions.

Mesenchymal stem cells under epigenetic control - the role of epigenetic machinery in fate decision and functional properties

Mesenchymal stem cells (mesenchymal stromal cells, MSC) are multipotent stem cells that can differentiate into cells of at least three mesodermal lineages, namely adipocytes, osteoblasts, and chondrocytes, and have potent immunomodulatory properties. Epigenetic modifications are critical regulators of gene expression and cellular differentiation of mesenchymal stem cells (MSCs). Epigenetic machinery controls MSC differentiation through direct modifications to DNA and histones. Understanding the role of epigenetic machinery in MSC is crucial for the development of effective cell-based therapies for degenerative and inflammatory diseases. In this review, we summarize the current understanding of the role of epigenetic control of MSC differentiation and immunomodulatory properties.

Multiple Dimensions of using Mesenchymal Stem Cells for Treating Liver Diseases: From Bench to Beside

Liver diseases impose a huge burden worldwide. Although hepatocyte transplantation has long been considered as a potential strategy for treating liver diseases, its clinical implementation has created some obvious limitations. As an alternative strategy, cell therapy, particularly mesenchymal stem cell (MSC) transplantation, is widely used in treating different liver diseases, including acute liver disease, acute-on-chronic liver failure, hepatitis B/C virus, autoimmune hepatitis, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, alcoholic liver disease, liver fibrosis, liver cirrhosis, and hepatocellular carcinoma. Here, we summarize the status of MSC transplantation in treating liver diseases, focusing on the therapeutic mechanisms, including differentiation into hepatocyte-like cells, immunomodulating function with a variety of immune cells, paracrine effects via the secretion of various cytokines and extracellular vesicles, and facilitation of homing and engraftment. Some improved perspectives and current challenges are also addressed. In summary, MSCs have great potential in the treatment of liver diseases based on their multi-faceted characteristics, and more accurate mechanisms and novel therapeutic strategies stemming from MSCs will facilitate clinical practice.

Comparative computational analysis to distinguish mesenchymal stem cells from fibroblasts

Introduction

Mesenchymal stem cells (MSCs) are considered to be the most promising stem cell type for cell-based therapies in regenerative medicine. Based on their potential to home to diseased body sites following a therapeutically application, these cells could (i) differentiate then into organ-specific cell types to locally restore injured cells or, most prominently, (ii) foster tissue regeneration including immune modulations more indirectly by secretion of protective growth factors and cytokines. As tissue-resident stem cells of mesenchymal origin, these cells are morphologically and even molecularly- at least concerning the classical marker genes- indistinguishable from similar lineage cells, particularly fibroblasts.

Methods

Here we used microarray-based gene expression and global DNA methylation analyses as well as accompanying computational tools in order to specify differences between MSCs and fibroblasts, to further unravel potential identity genes and to highlight MSC signaling pathways with regard to their trophic and immunosuppressive action.

Results

We identified 1352 differentially expressed genes, of which in the MSCs there is a strong signature for e.g., KRAS signaling, known to play essential role in stemness maintenance, regulation of coagulation and complement being decisive for resolving inflammatory processes, as well as of wound healing particularly important for their regenerative capacity. Genes upregulated in fibroblasts addressed predominately transcription and biosynthetic processes and mapped morphological features of the tissue. Concerning the cellular identity, we specified the already known HOX code for MSCs, established a potential HOX code for fibroblasts, and linked certain HOX genes to functional cell-type-specific properties. Accompanied methylation profiles revealed numerous regions, especially in HOX genes, being differentially methylated, which might provide additional biomarker potential.

Discussion

Conclusively, transcriptomic together with epigenetic signatures can be successfully be used for the definition (cellular identity) of MSCs versus fibroblasts as well as for the determination of the superior functional properties of MSCs, such as their immunomodulatory potential.

Pulmonary endogenous progenitor stem cell subpopulation: Physiology, pathogenesis, and progress

Lungs are structurally and functionally complex organs consisting of diverse cell types from the proximal to distal axis. They have direct contact with the external environment and are constantly at risk of various injuries. Capable to proliferate and differentiate, pulmonary endogenous progenitor stem cells contribute to the maintenance of lung structure and function both under homeostasis and following injuries. Discovering candidate pulmonary endogenous progenitor stem cell types and underlying regenerative mechanisms provide insights into therapeutic strategy development for lung diseases. In this review, we reveal their compositions, roles in lung disease pathogenesis and injury repair, and the underlying mechanisms. We further underline the advanced progress in research approach and potential therapy for lung regeneration. We also demonstrate the feasibility and prospects of pulmonary endogenous stem cell transplantation for lung disease treatment.

HOX genes in stem cells: Maintaining cellular identity and regulation of differentiation

Stem cells display a unique cell type within the body that has the capacity to self-renew and differentiate into specialized cell types. Compared to pluripotent stem cells, adult stem cells (ASC) such as mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) exhibit restricted differentiation capabilities that are limited to cell types typically found in the tissue of origin, which implicates that there must be a certain code or priming determined by the tissue of origin. HOX genes, a subset of homeobox genes encoding transcription factors that are generally repressed in undifferentiated pluripotent stem cells, emerged here as master regulators of cell identity and cell fate during embryogenesis, and in maintaining this positional identity throughout life as well as specifying various regional properties of respective tissues. Concurrently, intricate molecular circuits regulated by diverse stem cell-typical signaling pathways, balance stem cell maintenance, proliferation and differentiation. However, it still needs to be unraveled how stem cell-related signaling pathways establish and regulate ASC-specific HOX expression pattern with different temporal-spatial topography, known as the HOX code. This comprehensive review therefore summarizes the current knowledge of specific ASC-related HOX expression patterns and how these were integrated into stem cell-related signaling pathways. Understanding the mechanism of HOX gene regulation in stem cells may provide new ways to manipulate stem cell fate and function leading to improved and new approaches in the field of regenerative medicine.

SENP1 regulates the transformation of lung resident mesenchymal stem cells and is associated with idiopathic pulmonary fibrosis progression

BACKGROUND

Lung resident mesenchymal stem cells (LR-MSCs) play an important role in idiopathic pulmonary fibrosis (IPF) by transforming into myofibroblasts, thereby losing their repair ability. Evidence suggests that key proteins of multiple signaling pathways are involved in myofibroblast differentiation of LR-MSCs, such as β-Catenin and GLI family zinc finger 1 (GLI1). These proteins are regulated by SUMO (small ubiquitin-like modifier) modification, which is a post-translational modification that promotes protein degradation, while Sumo specific protein 1 (SENP1)-mediated deSUMOylation produces the opposite biological effects. Therefore, we speculated that SENP1 might be a potential target for treating pulmonary fibrosis by preventing the myofibroblast differentiation of LR-MSCs.

METHODS

LR-MSCs were isolated from mice by using immunomagnetic beads. The extracted LR-MSCs were identified by flow cytometric analysis and multilineage differentiation assays. Lentivirus packaged shRNA silenced the expression of SENP1 in vitro and vivo. The silencing efficacy of SENP1 was verified by real-time quantitative PCR. The effect of down-regulated SENP1 on the myofibroblast differentiation of LR-MSCs was assessed by Immunofluorescence and Western blot. Immunoprecipitation was used to clarify that SENP1 was a key target for regulating the activity of multiple signaling pathways in the direction of LR-MSCs differentiation. LR-MSCs resident in the lung was analyzed with in vivo imaging system. HE and Masson staining was used to evaluate the therapeutic effect of LR-MSCs with SENP1 down-regulation on the lung of BLM mice.

RESULTS

In this study, we found that the myofibroblast differentiation of LR-MSCs in IPF lung tissue was accompanied by enhanced SENP1-mediated deSUMOylation. The expression of SENP1 increased in LR-MSCs transition of bleomycin (BLM)-induced lung fibrosis. Interfering with expression of SENP1 inhibited the transformation of LR-MSCs into myofibroblasts in vitro and in vivo and restored their therapeutic effect in BLM lung fibrosis. In addition, activation of the WNT/β-Catenin and Hedgehog/GLI signaling pathways depends on SENP1-mediated deSUMOylation.

CONCLUSIONS

SENP1 might be a potential target to restore the repair function of LR-MSCs and treat pulmonary fibrosis. Video Abstract.

Exploring the Immunomodulatory Aspect of Mesenchymal Stem Cells for Treatment of Severe Coronavirus Disease 19

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is an enveloped, positive sense, single stranded RNA (+ssRNA) virus, belonging to the genus Betacoronavirus and family Coronaviridae. It is primarily transmitted from infected persons to healthy ones through inhalation of virus-laden respiratory droplets. After an average incubation period of 2–14 days, the majority of infected individuals remain asymptomatic and/or mildly symptomatic, whereas the remaining individuals manifest a myriad of clinical symptoms, including fever, sore throat, dry cough, fatigue, chest pain, and breathlessness. SARS-CoV-2 exploits the angiotensin converting enzyme 2 (ACE-2) receptor for cellular invasion, and lungs are amongst the most adversely affected organs in the body. Thereupon, immune responses are elicited, which may devolve into a cytokine storm characterized by enhanced secretion of multitude of inflammatory cytokines/chemokines and growth factors, such as interleukin (IL)-2, IL-6, IL-7, IL-8, IL-9, tumor necrosis factor alpha (TNF-α), granulocyte colony-stimulating factor (GCSF), basic fibroblast growth factor 2 (bFGF2), monocyte chemotactic protein-1 (MCP1), interferon-inducible protein 10 (IP10), macrophage inflammatory protein 1A (MIP1A), platelet-derived growth factor subunit B (PDGFB), and vascular endothelial factor (VEGF)-A. The systemic persistence of inflammatory molecules causes widespread histological injury, leading to functional deterioration of the infected organ(s). Although multiple treatment modalities with varying effectiveness are being employed, nevertheless, there is no curative COVID-19 therapy available to date. In this regard, one plausible supportive therapeutic modality may involve administration of mesenchymal stem cells (MSCs) and/or MSC-derived bioactive factors-based secretome to critically ill COVID-19 patients with the intention of accomplishing better clinical outcome owing to their empirically established beneficial effects. MSCs are well established adult stem cells (ASCs) with respect to their immunomodulatory, anti-inflammatory, anti-oxidative, anti-apoptotic, pro-angiogenic, and pro-regenerative properties. The immunomodulatory capabilities of MSCs are not constitutive but rather are highly dependent on a holistic niche. Following intravenous infusion, MSCs are known to undergo considerable histological trapping in the lungs and, therefore, become well positioned to directly engage with lung infiltrating immune cells, and thereby mitigate excessive inflammation and reverse/regenerate damaged alveolar epithelial cells and associated tissue post SARS-CoV-2 infection. Considering the myriad of abovementioned biologically beneficial properties and emerging translational insights, MSCs may be used as potential supportive therapy to counteract cytokine storms and reduce disease severity, thereby facilitating speedy recovery and health restoration.

Endoplasmic reticulum stress modulates the fate of lung resident mesenchymal stem cell to myofibroblast via C/EBP homologous protein during pulmonary fibrosis

Background

As a fatal interstitial lung disease, idiopathic pulmonary fibrosis (IPF) was characterized by the insidious proliferation of extracellular matrix (ECM)-producing mesenchymal cells. Recent studies have demonstrated that lung resident mesenchymal/stromal cells (LR-MSC) are the source of myofibroblasts. Endoplasmic reticulum (ER) stress is prominent in IPF lung. This study sought to investigate the effects of ER stress on the behavior of LR-MSC during pulmonary fibrosis.

Methods

ER stress and myofibroblast differentiation of LR-MSC in patients with IPF were evaluated. Primary mouse LR-MSC was harvested and used in vitro for testing the effects of ER stress and C/EBP homologous protein (CHOP) on LR-MSC. Adoptive transplantation of LR-MSC to bleomycin-induced pulmonary fibrosis was done to test the in vivo behavior of LR-MSC and its influence on pulmonary fibrosis.

Results

We found that myofibroblast differentiation of LR-MSC is associated with ER stress in IPF and bleomycin-induced mouse fibrotic lung. Tunicamycin-induced ER stress impairs the paracrine, migration, and reparative function of mouse LR-MSC to injured type 2 alveolar epithelial cells MLE-12. Overexpression of the ER stress responder C/EBP homologous protein (CHOP) facilitates the TGFβ1-induced myofibroblast transformation of LR-MSC via boosting the TGFβ/SMAD signaling pathway. CHOP knockdown facilitates engraftment and inhibits the myofibroblast transformation of LR-MSC during bleomycin-induced pulmonary fibrosis, thus promoting the efficacy of adopted LR-MSC in alleviating pulmonary fibrosis.

Conclusion

Our work revealed a novel role that ER stress involved in pulmonary fibrosis by influencing the fate of LR-MSC and transformed to “crime factor” myofibroblast, during which CHOP acts as the key modulator. These results indicate that pharmacies targeting CHOP or therapies based on CHOP knockdown LR-MSC may be promising ways to treat pulmonary fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02966-1.

Mesenchymal Stem/Stromal Cells in Progressive Fibrogenic Involvement and Anti-Fibrosis Therapeutic Properties

Fibrosis refers to the connective tissue deposition and stiffness usually as a result of injury. Fibrosis tissue-resident mesenchymal cells, including fibroblasts, myofibroblast, smooth muscle cells, and mesenchymal stem/stromal cells (MSCs), are major players in fibrogenic processes under certain contexts. Acknowledging differentiation potential of MSCs to the aforementioned other types of mesenchymal cell lineages is essential for better understanding of MSCs’ substantial contributions to progressive fibrogenesis. MSCs may represent a potential therapeutic option for fibrosis resolution owing to their unique pleiotropic functions and therapeutic properties. Currently, clinical trial efforts using MSCs and MSC-based products are underway but clinical data collected by the early phase trials are insufficient to offer better support for the MSC-based anti-fibrotic therapies. Given that MSCs are involved in the coagulation through releasing tissue factor, MSCs can retain procoagulant activity to be associated with fibrogenic disease development. Therefore, MSCs’ functional benefits in translational applications need to be carefully balanced with their potential risks.

Lung-Resident Mesenchymal Stem Cell Fates within Lung Cancer

Simple Summary

Lung cancer remains the leading cause of cancer-related deaths worldwide. Herein, the heterogeneous tumor stroma decisively impacts on tumor progression, therapy resistance, and, thus, poor clinical outcome. Among the numerous non-epithelial cells constructing the complex environment of lung carcinomas, mesenchymal stem cells (MSC) gained attraction being stromal precursor cells that could be recruited and ‘educated’ by lung cancer cells to adopt a tumor-associated MSC phenotype, serve as source for activated fibroblasts and presumably for vascular mural cells finally reinforcing tumor progression. Lung-resident MSCs should be considered as ‘local MSCs in stand by’ ready to be arranged within the cancer stroma.

Abstract

Lung-resident mesenchymal stem cells (LR-MSCs) are non-hematopoietic multipotent stromal cells that predominately reside adventitial within lung blood vessels. Based on their self-renewal and differentiation properties, LR-MSCs turned out to be important regulators of normal lung homeostasis. LR-MSCs exert beneficial effects mainly by local secretion of various growth factors and cytokines that in turn foster pulmonary regeneration including suppression of inflammation. At the same time, MSCs derived from various tissues of origins represent the first choice of cells for cell-based therapeutic applications in clinical medicine. Particularly for various acute as well as chronic lung diseases, the therapeutic applications of exogenous MSCs were shown to mediate beneficial effects, hereby improving lung function and survival. In contrast, endogenous MSCs of normal lungs seem not to be sufficient for lung tissue protection or repair following a pathological trigger; LR-MSCs could even contribute to initiation and/or progression of lung diseases, particularly lung cancer because of their inherent tropism to migrate towards primary tumors and metastatic sites. However, the role of endogenous LR-MSCs to be multipotent tumor-associated (stromal) precursors remains to be unraveled. Here, we summarize the recent knowledge how ‘cancer-educated’ LR-MSCs impact on lung cancer with a focus on mesenchymal stem cell fates.

Dissecting the Role of Mesenchymal Stem Cells in Idiopathic Pulmonary Fibrosis: Cause or Solution

Idiopathic pulmonary fibrosis (IPF) is one of the most aggressive forms of idiopathic interstitial pneumonias, characterized by chronic and progressive fibrosis subverting the lung's architecture, pulmonary functional decline, progressive respiratory failure, and high mortality (median survival 3 years after diagnosis). Among the mechanisms associated with disease onset and progression, it has been hypothesized that IPF lungs might be affected either by a regenerative deficit of the alveolar epithelium or by a dysregulation of repair mechanisms in response to alveolar and vascular damage. This latter might be related to the progressive dysfunction and exhaustion of the resident stem cells together with a process of cellular and tissue senescence. The role of endogenous mesenchymal stromal/stem cells (MSCs) resident in the lung in the homeostasis of these mechanisms is still a matter of debate. Although endogenous MSCs may play a critical role in lung repair, they are also involved in cellular senescence and tissue ageing processes with loss of lung regenerative potential. In addition, MSCs have immunomodulatory properties and can secrete anti-fibrotic factors. Thus, MSCs obtained from other sources administered systemically or directly into the lung have been investigated for lung epithelial repair and have been explored as a potential therapy for the treatment of lung diseases including IPF. Given these multiple potential roles of MSCs, this review aims both at elucidating the role of resident lung MSCs in IPF pathogenesis and the role of administered MSCs from other sources for potential IPF therapies.

The vascular nature of lung-resident mesenchymal stem cells

Human lungs bear their own reservoir of endogenous mesenchymal stem cells (MSCs). Although described as located perivascular, the cellular identity of primary lung MSCs remains elusive. Here we investigated the vascular nature of lung‐resident MSCs (LR‐MSCs) using healthy human lung tissue. LR‐MSCs predominately reside within the vascular stem cell niche, the so‐called vasculogenic zone of adult lung arteries. Primary LR‐MSCs isolated from normal human lung tissue showed typical MSC characteristics in vitro and were phenotypically and functionally indistinguishable from MSCs derived from the vascular wall of adult human blood vessels (VW‐MSCs). Moreover, LR‐MSCs expressed the VW‐MSC‐specific HOX code a characteristic to discriminate VW‐MSCs from phenotypical similar cells. Thus, LR‐MSC should be considered as VW‐MSCs. Immunofluorescent analyses of non‐small lung cancer (NSCLC) specimen further confirmed the vascular adventitia as stem cell niche for LR‐MSCs, and revealed their mobilization and activation in NSCLC progression. These findings have implications for understanding the role of MSC in normal lung physiology and pulmonary diseases, as well as for the rational design of additional therapeutic approaches.