Isolation and characterization of lung resident mesenchymal stem cells capable of differentiating into alveolar epithelial type II cells

Mesenchymal Stem Cells in Cancer Therapy

The mesenchymal stem/stromal cells (MSCs) are multipotent cells that were initially discovered in the bone marrow in the late 1960s but have so far been discovered in almost all tissues of the body. The multipotent property of MSCs enables them to differentiate into various cell types and lineages, such as adipocytes, chondrocytes, and osteocytes. The immunomodulation capacity and tumor-targeting features of MSCs made their use crucial for cell-based therapies in cancer treatment, yet limited advancement could be observed in translational medicine prospects due to the need for more information regarding the controversial roles of MSCs in crosstalk tumors. In this review, we discuss the therapeutic potential of MSCs, the controversial roles played by MSCs in cancer progression, and the anticancer therapeutic strategies that are in association with MSCs. Finally, the clinical trials designed for the direct use of MSCs for cancer therapy or for their use in decreasing the side effects of other cancer therapies are also mentioned in this review to evaluate the current status of MSC-based cancer therapies.

Mesenchymal stem cells and their derived exosomes for the treatment of COVID-19

Coronavirus disease 2019 (COVID-19) is an acute respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 infection typically presents with fever and respiratory symptoms, which can progress to severe respiratory distress syndrome and multiple organ failure. In severe cases, these complications may even lead to death. One of the causes of COVID-19 deaths is the cytokine storm caused by an overactive immune response. Therefore, suppressing the overactive immune response may be an effective strategy for treating COVID-19. Mesenchymal stem cells (MSCs) and their derived exosomes (MSCs-Exo) have potent homing abilities, immunomodulatory functions, regenerative repair, and antifibrotic effects, promising an effective tool in treating COVID-19. In this paper, we review the main mechanisms and potential roles of MSCs and MSCs-Exo in treating COVID-19. We also summarize relevant recent clinical trials, including the source of cells, the dosage and the efficacy, and the clinical value and problems in this field, providing more theoretical references for the clinical use of MSCs and MSCs-Exo in the treatment of COVID-19.

The homing of exogenous hair follicle mesenchymal stem cells into hair follicle niches

Hair loss is a debilitating condition associated with the depletion of dermal papilla cells (DPCs), which can be replenished by dermal sheath cells (DSCs). Hence, strategies aimed at increasing the populations of DPCs and DSCs hold promise for the treatment of hair loss. In this study, we demonstrated in mice that introduced exogenous DPCs and DSCs (hair follicle mesenchymal stem cells) could effectively migrate and integrate into the dermal papilla and dermal sheath niches, leading to enhanced hair growth and prolonged anagen phases. However, the homing rates of DPCs and DSCs were influenced by various factors, including recipient mouse depilation, cell passage number, cell dose, and immune rejection. Through in vitro and in vivo experiments, we also discovered that the CXCL13/CXCR5 pathway mediated the homing of DPCs and DSCs into hair follicle niches. This study underscores the potential of cell-based therapies for hair loss by targeted delivery of DPCs and DSCs to their respective niches and sheds light on the intriguing concept that isolated mesenchymal stem cells can home back to their original niche microenvironment.

METTL3-mediated m6A RNA methylation induces the differentiation of lung resident mesenchymal stem cells into myofibroblasts via the miR-21/PTEN pathway

BACKGROUND

The accumulation of myofibroblasts is the key pathological feature of pulmonary fibrosis (PF). Aberrant differentiation of lung-resident mesenchymal stem cells (LR-MSCs) has been identified as a critical source of myofibroblasts, but the molecular mechanisms underlying this process remain largely unknown. In recent years, N6-methyladenosine (m6A) RNA modification has been implicated in fibrosis development across diverse organs; however, its specific role in promoting the differentiation of LR-MSCs into myofibroblasts in PF is not well defined.

METHODS

In this study, we examined the levels of m6A RNA methylation and the expression of its regulatory enzymes in both TGF-β1-treated LR-MSCs and fibrotic mouse lung tissues. The downstream target genes of m6A and their related pathways were identified according to a literature review, bioinformatic analysis and experimental verification. We also assessed the expression levels of myofibroblast markers in treated LR-MSCs and confirmed the involvement of the above-described pathway in the aberrant differentiation direction of LR-MSCs under TGF-β1 stimulation by overexpressing or knocking down key genes within the pathway.

RESULTS

Our results revealed that METTL3-mediated m6A RNA methylation was significantly upregulated in both TGF-β1-treated LR-MSCs and fibrotic mouse lung tissues. This process directly led to the aberrant differentiation of LR-MSCs into myofibroblasts by targeting the miR-21/PTEN pathway. Moreover, inhibition of METTL3 or miR-21 and overexpression of PTEN could rescue this abnormal differentiation.

CONCLUSION

Our study demonstrated that m6A RNA methylation induced aberrant LR-MSC differentiation into myofibroblasts via the METTL3/miR-21/PTEN signaling pathway. We indicated a novel mechanism to promote PF progression. Targeting METTL3-mediated m6A RNA methylation and its downstream targets may present innovative therapeutic approaches for the prevention and treatment of PF.

Immunomodulatory Mechanisms and Therapeutic Potential of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are regarded as highly promising cells for allogeneic cell therapy, owing to their multipotent nature and ability to display potent and varied functions in different diseases. The functions of MSCs, including native immunomodulation, high self-renewal characteristic, and secretory and trophic properties, can be employed to improve the immune-modulatory functions in diseases. MSCs impact most immune cells by directly contacting and/or secreting positive microenvironmental factors to influence them. Previous studies have reported that the immunomodulatory role of MSCs is basically dependent on their secretion ability from MSCs. This review discusses the immunomodulatory capabilities of MSCs and the promising strategies to successfully improve the potential utilization of MSCs in clinical research.

CINC-2 and miR-199a-5p in EVs secreted by transplanted Thy1+ cells activate hepatocytic progenitor cell growth in rat liver regeneration

BACKGROUND

Small hepatocyte-like progenitor cells (SHPCs) are hepatocytic progenitor cells that transiently form clusters in rat livers treated with retrorsine (Ret) that underwent 70% partial hepatectomy (PH). We previously reported that transplantation of Thy1⁺ cells obtained from D-galactosamine-treated livers promotes SHPC expansion, thereby accelerating liver regeneration. Extracellular vesicles (EVs) secreted by Thy1⁺ cells induce sinusoidal endothelial cells (SECs) and Kupffer cells (KCs) to secrete IL17B and IL25, respectively, thereby activating SHPCs through IL17 receptor B (RB) signaling. This study aimed to identify the inducers of IL17RB signaling and growth factors for SHPC proliferation in EVs secreted by Thy1⁺ cells (Thy1-EVs).

METHODS

Thy1⁺ cells isolated from the livers of rats treated with D-galactosamine were cultured. Although some liver stem/progenitor cells (LSPCs) proliferated to form colonies, others remained as mesenchymal cells (MCs). Thy1-MCs or Thy1-LSPCs were transplanted into Ret/PH-treated livers to examine their effects on SHPCs. EVs were isolated from the conditioned medium (CM) of Thy1-MCs and Thy1-LSPCs. Small hepatocytes (SHs) isolated from adult rat livers were used to identify factors regulating cell growth in Thy1-EVs.

RESULTS

The size of SHPC clusters transplanted with Thy1-MCs was significantly larger than that of SHPC clusters transplanted with Thy1-LSPCs (p = 0.02). A comprehensive analysis of Thy1-MC-EVs revealed that miR-199a-5p, cytokine-induced neutrophil chemoattractant-2 (CINC-2), and monocyte chemotactic protein 1 (MCP-1) were candidates for promoting SHPC growth. Additionally, miR-199a-5p mimics promoted the growth of SHs (p = 0.02), whereas CINC-2 and MCP-1 did not. SECs treated with CINC-2 induced Il17b expression. KCs treated with Thy1-EVs induced the expression of CINC-2, Il25, and miR-199a-5p. CM derived from SECs treated with CINC-2 accelerated the growth of SHs (p = 0.03). Similarly, CM derived from KCs treated with Thy1-EVs and miR-199a-5p mimics accelerated the growth of SHs (p = 0.007). In addition, although miR-199a-overexpressing EVs could not enhance SHPC proliferation, transplantation of miR-199a-overexpressing Thy1-MCs could promote the expansion of SHPC clusters.

CONCLUSION

Thy1-MC transplantation may accelerate liver regeneration owing to SHPC expansion, which is induced by CINC-2/IL17RB signaling and miR-199a-5p via SEC and KC activation.

Perinatal origins of bronchopulmonary dysplasia-deciphering normal and impaired lung development cell by cell

Bronchopulmonary dysplasia (BPD) is a multifactorial disease occurring as a consequence of premature birth, as well as antenatal and postnatal injury to the developing lung. BPD morbidity and severity depend on a complex interplay between prenatal and postnatal inflammation, mechanical ventilation, and oxygen therapy as well as associated prematurity-related complications. These initial hits result in ill-explored aberrant immune and reparative response, activation of pro-fibrotic and anti-angiogenic factors, which further perpetuate the injury. Histologically, the disease presents primarily by impaired lung development and an arrest in lung microvascular maturation. Consequently, BPD leads to respiratory complications beyond the neonatal period and may result in premature aging of the lung. While the numerous prenatal and postnatal stimuli contributing to BPD pathogenesis are relatively well known, the specific cell populations driving the injury, as well as underlying mechanisms are still not well understood. Recently, an effort to gain a more detailed insight into the cellular composition of the developing lung and its progenitor populations has unfold. Here, we provide an overview of the current knowledge regarding perinatal origin of BPD and discuss underlying mechanisms, as well as novel approaches to study the perturbed lung development.

Therapeutic potential of mesenchymal stromal/stem cells in critical-care patients with systemic inflammatory response syndrome

BACKGROUND

Despite notable advances in the support and treatment of patients admitted to the intensive care unit (ICU), the management of those who develop a systemic inflammatory response syndrome (SIRS) still constitutes an unmet medical need.

MAIN BODY

Both the initial injury (trauma, pancreatitis, infections) and the derived uncontrolled response promote a hyperinflammatory status that leads to systemic hypotension, tissue hypoperfusion and multiple organ failure. Mesenchymal stromal/stem cells (MSCs) are emerging as a potential therapy for severe ICU patients due to their potent immunomodulatory, anti-inflammatory, regenerative and systemic homeostasis-regulating properties. MSCs have demonstrated clinical benefits in several inflammatory-based diseases, but their role in SIRS needs to be further explored.

CONCLUSION

In the current review, after briefly overviewing SIRS physiopathology, we explore the potential mechanisms why MSC therapy could aid in the recovery of this condition and the pre-clinical and early clinical evidence generated to date.

Stem cell-based therapy for human diseases

Recent advancements in stem cell technology open a new door for patients suffering from diseases and disorders that have yet to be treated. Stem cell-based therapy, including human pluripotent stem cells (hPSCs) and multipotent mesenchymal stem cells (MSCs), has recently emerged as a key player in regenerative medicine. hPSCs are defined as self-renewable cell types conferring the ability to differentiate into various cellular phenotypes of the human body, including three germ layers. MSCs are multipotent progenitor cells possessing self-renewal ability (limited in vitro) and differentiation potential into mesenchymal lineages, according to the International Society for Cell and Gene Therapy (ISCT). This review provides an update on recent clinical applications using either hPSCs or MSCs derived from bone marrow (BM), adipose tissue (AT), or the umbilical cord (UC) for the treatment of human diseases, including neurological disorders, pulmonary dysfunctions, metabolic/endocrine-related diseases, reproductive disorders, skin burns, and cardiovascular conditions. Moreover, we discuss our own clinical trial experiences on targeted therapies using MSCs in a clinical setting, and we propose and discuss the MSC tissue origin concept and how MSC origin may contribute to the role of MSCs in downstream applications, with the ultimate objective of facilitating translational research in regenerative medicine into clinical applications. The mechanisms discussed here support the proposed hypothesis that BM-MSCs are potentially good candidates for brain and spinal cord injury treatment, AT-MSCs are potentially good candidates for reproductive disorder treatment and skin regeneration, and UC-MSCs are potentially good candidates for pulmonary disease and acute respiratory distress syndrome treatment.

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.

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.

MSCs as Tumor-Specific Vectors for the Delivery of Anticancer Agents-A Potential Therapeutic Strategy in Cancer Diseases: Perspectives for Quinazoline Derivatives

Mesenchymal stem cells (MSCs) are considered to be a powerful tool in the treatment of various diseases. Scientists are particularly interested in the possibility of using MSCs in cancer therapy. The research carried out so far has shown that MSCs possess both potential pro-oncogenic and anti-oncogenic properties. It has been confirmed that MSCs can regulate tumor cell growth through a paracrine mechanism, and molecules secreted by MSCs can promote or block a variety of signaling pathways. These findings may be crucial in the development of new MSC-based cell therapeutic strategies. The abilities of MSCs such as tumor tropism, deep migration and immune evasion have evoked considerable interest in their use as tumor-specific vectors for small-molecule anticancer agents. Studies have shown that MSCs can be successfully loaded with chemotherapeutic drugs such as gemcitabine and paclitaxel, and can release them at the site of primary and metastatic neoplasms. The inhibitory effect of MSCs loaded with anti-cancer agents on the proliferation of cancer cells has also been observed. However, not all known chemotherapeutic agents can be used in this approach, mainly due to their cytotoxicity towards MSCs and insufficient loading and release capacity. Quinazoline derivatives appear to be an attractive choice for this therapeutic solution due to their biological and pharmacological properties. There are several quinazolines that have been approved for clinical use as anticancer drugs by the US Food and Drug Administration (FDA). It gives hope that the synthesis of new quinazoline derivatives and the development of methods of their application may contribute to the establishment of highly effective therapies for oncological patients. However, a deeper understanding of interactions between MSCs and tumor cells, and the exploration of the possibilities of using quinazoline derivatives in MSC-based therapy is necessary to achieve this goal. The aim of this review is to discuss the prospects for using MSC-based cell therapy in cancer treatment and the potential use of quinazolines in this procedure.

The Role of Zinc in Bone Mesenchymal Stem Cell Differentiation

Zinc is an essential trace element for bone growth and bone homeostasis in the human body. Bone mesenchymal stem cells (BMSCs) are multipotent progenitors existing in the bone marrow stroma with the capability of differentiating along multiple lineage pathways. Zinc plays a paramount role in BMSCs, which can be spurred differentiating into osteoblasts, chondrocytes, or adipocytes, and modulates the formation and activity of osteoclasts. The expression of related genes also changed during the differentiation of various cell phenotypes. Based on the important role of zinc in BMSC differentiation, using zinc as a therapeutic approach for bone remodeling will be a promising method. This review explores the role of zinc ion in the differentiation of BMSCs into various cell phenotypes and outlines the existing research on their molecular mechanism.

Non-viral siRNA transfection of primary mesenchymal stromal cells (MSCs): Assessment of tyrosine-modified PEI and PPI efficacy and biocompatibility

Mesenchymal stromal cells (MSCs) are multipotent cells derived from different sources and able to differentiate into distinct cell lineages. For their possible biomedical application, the "tuning" of MSCs also involves the specific knockdown of defined target genes. A major limitation, however, is the notoriously low transfection efficacy especially of primary MSCs. In this paper, we systemically analyze a large set of tyrosine-modified linear or branched low molecular weight polyethylenimines (PEIs) of different sizes, as well as the tyrosine-modified polypropylenimine dendrimer PPI-G4, for their capacity of non-viral siRNA transfection into umbilical cord-derived MSCs from two different donors. Knockdown efficacies are determined on the molecular level and confirmed in functional assays. Beyond the determination of cell viabilities, acute cytotoxicity, induction of apoptosis/necrosis and mitochondrial membrane alterations are also studied. On the molecular level, caspase activation, ROS induction and genotoxic effects are analyzed. Major differences are observed between the various tyrosine-modified PEIs, with some candidates showing high knockdown efficacy and biocompatibility. PPI-G4-Y dendrimers, however, are identified as most efficient for siRNA transfection into MSCs. PPI-G4-Y/siRNA nanoparticles lead to particularly high gene knockdown, without cytotoxic and genotoxic effects on the cellular and molecular level, and are thus particularly well-suited for the tuning of MSCs.

Single-Cell RNA Sequencing-Based Characterization of Resident Lung Mesenchymal Stromal Cells in Bronchopulmonary Dysplasia

Late lung development is a period of alveolar and microvascular formation, which is pivotal in ensuring sufficient and effective gas exchange. Defects in late lung development manifest in premature infants as a chronic lung disease named bronchopulmonary dysplasia (BPD). Numerous studies demonstrated the therapeutic properties of exogenous bone marrow and umbilical cord-derived mesenchymal stromal cells (MSCs) in experimental BPD. However, very little is known regarding the regenerative capacity of resident lung MSCs (L-MSCs) during normal development and in BPD. In this study we aimed to characterize the L-MSC population in homeostasis and upon injury. We used single-cell RNA sequencing (scRNA-seq) to profile in situ Ly6a+ L-MSCs in the lungs of normal and O2-exposed neonatal mice (a well-established model to mimic BPD) at 3 developmental timepoints (postnatal days 3, 7, and 14). Hyperoxia exposure increased the number and altered the expression profile of L-MSCs, particularly by increasing the expression of multiple pro-inflammatory, pro-fibrotic, and anti-angiogenic genes. In order to identify potential changes induced in the L-MSCs transcriptome by storage and culture, we profiled 15 000 Ly6a+ L-MSCs after in vitro culture. We observed great differences in expression profiles of in situ and cultured L-MSCs, particularly those derived from healthy lungs. Additionally, we have identified the location of Ly6a+/Col14a1+ L-MSCs in the developing lung and propose Serpinf1 as a novel, culture-stable marker of L-MSCs. Finally, cell communication analysis suggests inflammatory signals from immune and endothelial cells as main drivers of hyperoxia-induced changes in L-MSCs transcriptome.

Identification and characterization of pulmonary mesenchymal stem cells derived from rat fetal lung tissue

Pulmonary mesenchymal stem cells (PMSCs) have great potential in lung tissue repair and regeneration, which have been isolated from some mammalian species, including mice, bovine and pig. However, the isolation, characteristics and differentiation potential of rat PMSCs have not been reported. In this study, we successfully isolated PMSCs from Sprague-Dawley rat fetal lung tissue in vitro for the first time and attempted to evaluate its multilineage differentiation potentials. The cultured PMSCs showed typical spindle-shaped morphology and high proliferative potential, and could be passaged for at least 13 passages and maintained high hereditary stability with more than 93.6 % of cells were diploid (2n = 42) by G-banding analysis. Furthermore, the PMSCs could express mesenchymal markers Sca-1, CD29, CD44, CD73 and CD90, but not hematopoietic markers CD34 and CD45. Besides, the expression of cell markers of AT2 (SFTPC), AT1 (PDPN) and macrophage (CD11b) were also negative. Cell cycle examination revealed majority of the PMSCs were in G0/G1 phase, which are similar with previously reported pig PMSCs. In addition, the PMSCs were multipotent and could differentiated into osteocytes, adipocytes, hepatocytes and neurons in vitro. Together, the present study demonstrated the stemness and multi-differentiation potentials of rat PMSCs, which conferred a potential regenerative cell resource for cell regenerative therapy of lung injury.

Bioprintable Lung Extracellular Matrix Hydrogel Scaffolds for 3D Culture of Mesenchymal Stromal Cells

Mesenchymal stromal cell (MSC)-based cell therapy in acute respiratory diseases is based on MSC secretion of paracrine factors. Several strategies have proposed to improve this are being explored including pre-conditioning the MSCs prior to administration. We here propose a strategy for improving the therapeutic efficacy of MSCs based on cell preconditioning by growing them in native extracellular matrix (ECM) derived from the lung. To this end, a bioink with tunable stiffness based on decellularized porcine lung ECM hydrogels was developed and characterized. The bioink was suitable for 3D culturing of lung-resident MSCs without the need for additional chemical or physical crosslinking. MSCs showed good viability, and contraction assays showed the existence of cell–matrix interactions in the bioprinted scaffolds. Adhesion capacity and length of the focal adhesions formed were increased for the cells cultured within the lung hydrogel scaffolds. Also, there was more than a 20-fold increase of the expression of the CXCR4 receptor in the 3D-cultured cells compared to the cells cultured in plastic. Secretion of cytokines when cultured in an in vitro model of lung injury showed a decreased secretion of pro-inflammatory mediators for the cells cultured in the 3D scaffolds. Moreover, the morphology of the harvested cells was markedly different with respect to conventionally (2D) cultured MSCs. In conclusion, the developed bioink can be used to bioprint structures aimed to improve preconditioning MSCs for therapeutic purposes.

Mesenchymal stem/stromal cell-based therapy: mechanism, systemic safety and biodistribution for precision clinical applications

Mesenchymal stem/stromal cells (MSCs) are a promising resource for cell-based therapy because of their high immunomodulation ability, tropism towards inflamed and injured tissues, and their easy access and isolation. Currently, there are more than 1200 registered MSC clinical trials globally. However, a lack of standardized methods to characterize cell safety, efficacy, and biodistribution dramatically hinders the progress of MSC utility in clinical practice. In this review, we summarize the current state of MSC-based cell therapy, focusing on the systemic safety and biodistribution of MSCs. MSC-associated risks of tumor initiation and promotion and the underlying mechanisms of these risks are discussed. In addition, MSC biodistribution methodology and the pharmacokinetics and pharmacodynamics of cell therapies are addressed. Better understanding of the systemic safety and biodistribution of MSCs will facilitate future clinical applications of precision medicine using stem cells.

Long Non-coding RNAs and MicroRNAs Interplay in Osteogenic Differentiation of Mesenchymal Stem Cells

Long non-coding RNAs (lncRNAs) have gained great attention as epigenetic regulators of gene expression in many tissues. Increasing evidence indicates that lncRNAs, together with microRNAs (miRNAs), play a pivotal role in osteogenesis. While miRNA action mechanism relies mainly on miRNA-mRNA interaction, resulting in suppressed expression, lncRNAs affect mRNA functionality through different activities, including interaction with miRNAs. Recent advances in RNA sequencing technology have improved knowledge into the molecular pathways regulated by the interaction of lncRNAs and miRNAs. This review reports on the recent knowledge of lncRNAs and miRNAs roles as key regulators of osteogenic differentiation. Specifically, we described herein the recent discoveries on lncRNA-miRNA crosstalk during the osteogenic differentiation of mesenchymal stem cells (MSCs) derived from bone marrow (BM), as well as from different other anatomical regions. The deep understanding of the connection between miRNAs and lncRNAs during the osteogenic differentiation will strongly improve knowledge into the molecular mechanisms of bone growth and development, ultimately leading to discover innovative diagnostic and therapeutic tools for osteogenic disorders and bone diseases.

Targeted Dual Small Interfering Ribonucleic Acid Delivery via Non-Viral Polymeric Vectors for Pulmonary Fibrosis Therapy

Inhibiting the myofibroblast differentiation of lung-resident mesenchymal stem cells (LR-MSCs) is a promising yet challenging approach for pulmonary fibrosis (PF) therapy. Here, micelles formed by a graft copolymer of multiple PEGs modified branched polyethylenimine are used for delivering runt-related transcription factor-1 (RUNX1) small interfering RNA (siRNA) (siRUNX1) to the lung, aiming to inhibit the myofibroblast differentiation of LR-MSCs. LR-MSC targeting is achieved by functionalizing the micelle surface with an anti-stem-cell antigen-1 antibody fragment (Fab'). Consequently, therapeutic benefits are obtained by successful suppression of myofibroblast differentiation of LR-MSCs in bleomycin-induced PF model mice treated with siRUNX1-loaded micelles. Furthermore, an excellent synergistic effect of PF therapy is achieved for this micelle system loaded siRUNX1 and glioma-associated oncogene homolog-1 (Gli1) small interfering RNA (siGli1), a traditional anti-PF siRNA of glioma-associated oncogene homolog-1. Hence, this work not only provides RUNX1 as a novel PF therapeutic target, but also as a promising dual siRNA-loaded nanocarrier system for the therapy of PF.

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

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

The Shh/Gli signaling cascade regulates myofibroblastic activation of lung-resident mesenchymal stem cells via the modulation of Wnt10a expression during pulmonary fibrogenesis

Lung-resident mesenchymal stem cells (LR-MSCs) are important regulators of lung repair and regeneration, and evidence suggests that this cell population also plays a vital role in fibrosis. Crosstalk between sonic hedgehog (Shh) signaling and wingless/integrated (Wnt) has been demonstrated in idiopathic pulmonary fibrosis (IPF). However, the underlying correlation between LR-MSCs and the Shh-Wnt signaling cascade remains poorly understood. Here, we identified Wnt10a as a key factor in pulmonary fibrosis. Using a bleomycin mouse model, we found that highly expressed Wnt10a was secreted by LR-MSCs undergoing myofibroblastic differentiation. LR-MSCs with myofibroblast characteristics isolated from fibrotic lungs exhibited increased Shh pathway activity, suggesting their role as Shh targets. In vitro, LR-MSCs responded to stimulation by recombinant Shh, acquiring a myofibroblast phenotype. We further demonstrated that the Shh/glioblastoma (Gli) system machinery regulated LR-MSC-to-myofibroblast transition and pulmonary fibrosis via manipulation of Wnt/β-catenin signaling. Accordingly, inhibition of the Shh-Wnt signaling cascade prevented LR-MSC transformation into myofibroblasts and ameliorated pulmonary fibrotic lesions. Moreover, induction of Wnt10a expression and activation of Shh/Gli signaling were confirmed in human pulmonary fibrosis. In summary, this study linking the Shh-Wnt signaling cascade with LR-MSC fibrogenic activity furthered the current understanding of pulmonary fibrosis pathogenesis and might provide a new perspective in the development of treatment strategies for IPF.

Therapeutic Potential of “Exosomes Derived Multiple Allogeneic Proteins Paracrine Signaling: Exosomes d-MAPPS” is Based on the Effects of Exosomes, Immunosuppressive and Trophic Factors

Due to their differentiation capacity and potent immunosuppressive and pro-angiogenic properties, mesenchymal stem cells (MSCs) have been considered as new therapeutic agents in regenerative medicine. Since most of MSC-mediated beneficent effects are a consequence of their paracrine action, we designed MSC-based product “Exosomes Derived Multiple Allogeneic Proteins Paracrine Signaling (Exosomes d-MAPPS), which activity is based on MSCs-derived growth factors and immunomodulatory cytokines capable to attenuate inflammation and to promote regeneration of injured tissues. Interleukin 1 receptor antagonist (IL-1Ra) and IL-27 were found in high concentrations in Exosomes d-MAPPS samples indicating strong anti-inflammatory and immunosuppressive potential of Exosomes d-MAPPS. Additionally, high concentrations of vascular endothelial growth factor receptor (VEGFR1) and chemokines (CXCL16, CCL21, CXCL14) were noticed at Exosomes d-MAPPS samples suggesting their potential to promote generation of new blood vessels and migration of CXCR6, CCR7 and CXCR4 expressing cells. Since all proteins which were found in high concentration in Exosomes d-MAPPS samples (IL-1Ra, CXCL16, CXCL14, CCL21, IL-27 and VEGFR1) are involved in modulation of lung, eye, and synovial inflammation, Exosomes d-MAPPS samples were prepared as inhalation and ophthalmic solutions in addition to injection formulations; their application in several patients suffering from chronic obstructive pulmonary disease, osteoarthritis, and dry eye syndrome resulted with significant improvement of biochemical and functional parameters. In conclusion, Exosomes d-MAPPS, due to the presence of important anti-inflammatory, immunomodulatory, and pro-angiogenic factors, represents potentially new therapeutic agent in regenerative medicine that should be further tested in large clinical studies.

A Comparison of Phenotypic and Functional Properties of Mesenchymal Stromal Cells and Multipotent Adult Progenitor Cells

Both Multipotent Adult Progenitor Cells and Mesenchymal Stromal Cells are bone-marrow derived, non-haematopoietic adherent cells, that are well-known for having immunomodulatory and pro-angiogenic properties, whilst being relatively non-immunogenic. However, they are phenotypically and functionally distinct cell types, which has implications for their efficacy in different settings. In this review we compare the phenotypic and functional properties of these two cell types, to help in determining which would be the superior cell type for different applications.

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.

The multifaceted role of mesenchymal stem cells in cancer

Mesenchymal stem cells (MSCs) are multipotent stem cells derived from the mesoderm that give rise to several mesenchymal lineages, including osteoblasts, adipocytes, chondrocytes and myocytes. Their potent ability to home to tumors coupled with their differentiation potential and immunosuppressive function positions MSCs as key regulators of tumor fate. Here we review the existing knowledge on the involvement of MSCs in multiple tumor-promoting processes, including angiogenesis, epithelial-mesenchymal transition, metastasis, immunosuppression and therapy resistance. We also discuss the clinical potential of MSC-based therapy for cancer.

Insights into the Signal Transduction Pathways of Mouse Lung Type II Cells Revealed by Transcription Factor Profiling in the Transcriptome

Alveolar type II cells constitute a small fraction of the total lung cell mass. However, they play an important role in many cellular processes including trans-differentiation into type I cells as well as repair of lung injury in response to toxic chemicals and respiratory pathogens. Transcription factors are the regulatory proteins dynamically modulating DNA structure and gene expression. Transcription factor profiling in microarray datasets revealed that several members of AP1, ATF, NF-kB, and C/EBP families involved in diverse responses were expressed in mouse lung type II cells. A transcriptional factor signature consisting of Cebpa, Srebf1, Stat3, Klf5, and Elf3 was identified in lung type II cells, Sox9+ pluripotent lung stem cells as well as in mouse lung development. Identification of the transcription factor profile in mouse lung type II cells will serve as a useful resource and facilitate the integrated analysis of signal transduction pathways and specific gene targets in a variety of physiological conditions.

MiR-124 regulates transforming growth factor-β1 induced differentiation of lung resident mesenchymal stem cells to myofibroblast by repressing Wnt/β-catenin signaling

Lung resident mesenchymal stem cells (LR-MSCs) contribute to the progression of idiopathic pulmonary fibrosis (IPF). We aimed to investigate the molecular mechanism underlying LR-MSCs regulation upon transforming growth factor (TGF)-β1 stimulation. We induced fibrogenic differentiation of LR-MSCs isolated from mice by TGF-β1. Several stem cell markers were detected by flow cytometric analysis. Protein expression level was tested by Western blotting and mRNA level was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability, proliferation and apoptosis were measured. TGF-β1 promoted fibrogenic differentiation of LR-MSCs and upregulated β-catenin and p-glycogen synthase kinase-3β, suggesting the activation of Wnt signaling. MicroRNA (MiR)-124-3p was significantly upregulated in TGF-β1 treated LR-MSCs compared to untreated cells. Intriguingly, silence of miR-124 reversed the TGF-β1-induced changes in cell viability and proliferation, and also led to a decrease of cell apoptosis. Additionally, in miR-124 silenced cells, α-smooth muscle actin, collagen I and fibronectin were downregulated compared to control cells. We ultimately identified a new target of miR-124, AXIN1, which was repressed by miR-124. In conclusion, miR-124 regulates AXIN1 to activate Wnt signaling and therefore plays a crucial role in the TGF-β1-induced fibrogenic differentiation.

Role of bone marrow mesenchymal stem cells in the development of PQ‑induced pulmonary fibrosis

Paraquat (PQ) poisoning‑induced pulmonary fibrosis is one of the primary causes of mortality in patients with PQ poisoning. The potential mechanism of PQ‑induced pulmonary fibrosis was thought to be mediated by inflammation. Recently, bone marrow‑derived mesenchymal stem cells (BMSCs) have been considered as a potential strategy for the treatment of fibrotic disease due to their anti‑inflammatory and immunosuppressive effects. In the present study, an increased accumulation of BMSCs in a mouse model of PQ‑induced pulmonary fibrosis following their transplantation, markedly improving the survival rate of mice with PQ poisoning. In addition, the results indicated that BMSC transplantation may inhibit the production of pro‑inflammatory cytokines, including tumor necrosis factor‑α interleukin (IL)‑1β, IL‑6 and IL‑10 in the lung tissues of PQ‑poisoned mice, and ultimately attenuate the pulmonary fibrosis. In vitro, BMSCs may suppress PQ‑induced epithelial‑to‑mesenchymal transition and protect pulmonary epithelial cells from PQ‑induced apoptosis. These findings suggest that BMSC transplantation may be a promising treatment for pulmonary fibrosis induced by PQ poisoning.

M2 macrophages promote myofibroblast differentiation of LR-MSCs and are associated with pulmonary fibrogenesis

Background

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by the histopathological pattern of usual interstitial pneumonia and is associated with a high mortality rate. Recently, lung resident mesenchymal stem cells (LR-MSCs) have been identified as an important contributor to myofibroblast activation in pulmonary fibrosis. Macrophages are also believed to play a critical role in pulmonary fibrosis. However, the underlying connections between LR-MSCs and macrophages in the pathogenesis of pulmonary fibrosis are still elusive.

Methods

In this study, we investigated the interaction between LR-MSCs and macrophages using a bleomycin-induced mouse pulmonary fibrosis model and a coculture system.

Results

Here, we show that blocking pulmonary macrophage infiltration attenuated bleomycin-induced pulmonary fibrosis. In addition, as determined by flow cytometry, we discovered that the recruited macrophages in fibrotic lungs of bleomycin-treated mice were mainly M2 macrophages. In particular, we found that M2, rather than M1 macrophages, promoted myofibroblast differentiation of LR-MSCs. Moreover, we demonstrated that suppression of the Wnt/β-catenin signaling pathway could attenuate myofibroblast differentiation of LR-MSCs induced by M2 macrophages and bleomycin-induced pulmonary fibrosis. Tissue samples from IPF patients confirmed the infiltration of M2 macrophages and activation of Wnt/β-catenin signaling pathway.

Conclusion

In summary, this study furthered our understanding of the pulmonary fibrosis pathogenesis and highlighted M2 macrophages as a critical target for treating pulmonary fibrosis.

Electronic supplementary material

The online version of this article (10.1186/s12964-018-0300-8) contains supplementary material, which is available to authorized users.

Treatment of Hyperoxia-Induced Lung Injury with Lung Mesenchymal Stem Cells in Mice

Objective

Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in preterm neonates and has no effective treatment. This study aimed to investigate the therapeutic effects of neonatal mouse lung resident mesenchymal stem cells (L-MSCs) on the hyperoxia-induced lung injury.

Methods

L-MSCs were separated and identified according to the MSC criterions. Hyperoxia-Induced Lung Injury (HILI) of neonatal KM mice was induced with hyperoxia (FiO₂ = 60%) and investigated with pathological methods. Neonatal KM mice were divided into 3 groups (hyperoxia + L-MSC group, hyperoxia + PBS group, and air control group). Mice in the hyperoxia + L-MSC group were treated with L-MSCs at 3, 7, and 14 days after birth. After hyperoxia exposure for 21 days, the lung pathology, Radial Alveolar Count (RAC), CD31 expression, and vascular endothelial growth factor (VEGF) expression were investigated.

Results

After hyperoxia exposure, the body weight, RAC, CD31 expression, and VEGF expression in the hyperoxia + L-MSC group were significantly better than those in the hyperoxia + PBS group but inferior to those in the air control group significantly. These indicate L-MSCs are partially protective on the lung injury of mice with hyperoxia-induced BPD.

Conclusion

L-MSCs are helpful for the prevention and treatment of BPD, and endogenous L-MSCs may play a role in the postinjury repair of the lung.

Mesenchymal Stromal Cells to Regenerate Emphysema: On the Horizon?

Mesenchymal stem or stromal cells (MSCs) are multipotent cells that play a pivotal role in various phases of lung development and lung homeostasis, and potentially also lung regeneration. MSCs do not only self-renew and differentiate into renew tissues, but also have anti-inflammatory and paracrine properties to reduce damage and to support tissue regeneration, constituting a promising cell-based treatment strategy for the repair of damaged alveolar tissue in emphysema. This review discusses the current state of the art regarding the potential of MSCs for the treatment of emphysema. The optimism regarding this treatment strategy is supported by promising results from animal models. Still, there are considerable challenges before effective stem cell treatment can be realized in emphysema patients. It is difficult to draw definitive conclusions from the available animal studies, as different models, dosage protocols, administration routes, and sources of MSCs have been used with different measures of effectiveness. Moreover, the regrowth potential of differentiated tissues and organs differs between species. Essential questions about MSC engraftment, retention, and survival have not been sufficiently addressed in a systematic manner. Few human studies have investigated MSC treatment for chronic obstructive pulmonary disease, demonstrating short-term safety but no convincing benefits on clinical outcomes. Possible explanations for the lack of beneficial effects on clinical outcomes could be the source (bone marrow), route, dosage, frequency of administration, and delivery (lack of a bioactive scaffold). This review will provide a comprehensive overview of the (pre)clinical studies on MSC effects in emphysema and discuss the current challenges regarding the optimal use of MSCs for cell-based therapies.

Epigenetic changes in mesenchymal stem cells differentiation

Epigenetic factors are known to play a major role in determining stem cell fate and differentiation. Mesenchymal stem cells are the most studied population of stem cells due to their important applications in experimental biology and regenerative medicine. After a brief overview on mesenchymal stem cells, this review aims to highlight the role of epigenetic changes on mesenchymal stem cells biology and differentiation protocols with a focus on osteocytic, chondrocytic and adipocytic differentiation. Chromatin remodeling, DNA methylation, histone modifications and miRNA expression will be investigated. The impact of epigenetics on transdifferentiation of mesenchymal stem cells will also be discussed. Indeed, epigenetic modulation appears to constitute a promising experimental target in stem cell basic and translational research.

Lung regeneration after toxic injury is improved in absence of dioxin receptor

Recent experimental evidences from cellular systems and from mammalian and non-mammalian animal models highlight novel functions for the aryl hydrocarbon/dioxin receptor (AhR) in maintaining cell differentiation and tissue homeostasis. Notably, AhR depletion stimulates an undifferentiated and pluripotent phenotype likely associated to a mesenchymal transition in epithelial cells and to increased primary tumorigenesis and metastasis in melanoma. In this work, we have used a lung model of epithelial regeneration to investigate whether AhR regulates proper tissue repair by adjusting the expansion of undifferentiated stem-like cells. AhR-null mice developed a faster and more efficient repair of the lung bronchiolar epithelium upon naphthalene injury that required increased cell proliferation and the earlier activation of stem-like Clara, Basal and neuroepithelial cells precursors. Increased basal content in multipotent Sca1⁺/CD31^-/CD4^- cells and in cells expressing pluripotency factors NANOG and OCT4 could also improve re-epithelialization in AhR-null lungs. The reduced response of AhR-deficient lungs to Sonic Hedgehog (Shh) repression shortly after injury may also help their improved bronchiolar epithelium repair. These results support a role for AhR in the regenerative response against toxins, and open the possibility of modulating its activation level to favor recovery from lesions caused by environmental contaminants.

TNF-α-induced NF-κB activation promotes myofibroblast differentiation of LR-MSCs and exacerbates bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and irreversible lung disease of unknown cause. It has been reported that both lung resident mesenchymal stem cells (LR-MSCs) and tumor necrosis factor-α (TNF-α) play important roles in the development of pulmonary fibrosis. However, the underlying connections between LR-MSCs and TNF-α in the pathogenesis of pulmonary fibrosis are still elusive. In this study, we found that the pro-inflammatory cytokine TNF-α and the transcription factor nuclear factor kappa B (NF-κB) p65 subunit were both upregulated in bleomycin-induced fibrotic lung tissue. In addition, we discovered that TNF-α promotes myofibroblast differentiation of LR-MSCs through activating NF-κB signaling. Interestingly, we also found that TNF-α promotes the expression of β-catenin. Moreover, we demonstrated that suppression of the NF-κB signaling could attenuate myofibroblast differentiation of LR-MSCs and bleomycin-induced pulmonary fibrosis which were accompanied with decreased expression of β-catenin. Our data implicates that inhibition of the NF-κB signaling pathway may provide a therapeutic strategy for pulmonary fibrosis, a disease that warrants more effective treatment approaches.

Hypoxia promotes the skewed differentiation of umbilical cord mesenchymal stem cells toward type II alveolar epithelial cells by regulating microRNA-145

Mesenchymal stem cells (MSCs) are well recognized for their ability to differentiate into type II alveolar epithelial (ATII) cells in damaged lungs, which is critical for reepithelization and recovery in acute lung injury (ALI). However, the high level of transforming growth factor-β (TGF-β) commonly seen in injured lung tissues is also able to induce MSCs to differentiate into fibroblast-like cells. In this study, we found that hypoxia could promote umbilical cord mesenchymal stem cells (UCMSCs) differentiation into ATII cells rather than into fibroblast-like cells, and this effect was mainly mediated by microRNA-145 (miR-145), which could induce the inhibition of TGF-β signaling by targeting TGF-β receptor II (TGFβRII). Clarifying the function of hypoxia in the fate determination of MSCs is important for improving stem cell-based therapies for ALI.

The Impact of Epigenetics on Mesenchymal Stem Cell Biology

Changes in epigenetic marks are known to be important regulatory factors in stem cell fate determination and differentiation. In the past years, the investigation of the epigenetic regulation of stem cell biology has largely focused on embryonic stem cells (ESCs). Contrarily, less is known about the epigenetic control of gene expression during differentiation of adult stem cells (AdSCs). Among AdSCs, mesenchymal stem cells (MSCs) are the most investigated stem cell population because of their enormous potential for therapeutic applications in regenerative medicine and tissue engineering. In this review, we analyze the main studies addressing the epigenetic changes in MSC landscape during in vitro cultivation and replicative senescence, as well as follow osteocyte, chondrocyte, and adipocyte differentiation. In these studies, histone acetylation, DNA methylation, and miRNA expression are among the most investigated phenomena. We describe also epigenetic changes that are associated with in vitro MSC trans-differentiation. Although at the at initial stage, the epigenetics of MSCs promise to have profound implications for stem cell basic and applied research. J. Cell. Physiol. 231: 2393-2401, 2016. © 2016 Wiley Periodicals, Inc.

miR-877-3p targets Smad7 and is associated with myofibroblast differentiation and bleomycin-induced lung fibrosis

Myofibroblast differentiation of lung resident mesenchymal stem cells (LR-MSC) plays an important role in idiopathic pulmonary fibrosis. By comparing the expression profiles of miRNAs before and after myofibroblast differentiation of LR-MSC, we identified miR-877-3p as a fibrosis-related miRNA. We found that miR-877-3p sequestration inhibited the myofibroblast differentiation of LR-MSC and attenuates bleomycin-induced lung fibrosis by targeting Smad7. Smad7, as an inhibitory smad in the TGF-β1 signaling pathway, was decreased in the myofibroblast differentiation of LR-MSC and up-regulation of Smad7 could inhibit the differentiation process. Our data implicates a potential application of miR-877-3p as a fibrosis suppressor for pulmonary fibrosis therapy and also as a fibrosis marker for predicting prognosis.

Inhibition of Wnt/β-catenin signaling suppresses bleomycin-induced pulmonary fibrosis by attenuating the expression of TGF-β1 and FGF-2

Pulmonary fibrosis is a progressive lung disorder of unknown etiology, which is characterized by alterations in alveolar epithelium function, fibroblast activation, and increased extracellular matrix deposition. Recent studies have demonstrated that PF is associated with uncontrolled production of cytokines after lung injury. In the present study, we found that transforming growth factor-β1 (TGF-β1) and fibroblast growth factor 2 (FGF-2) were both upregulated in bleomycin-induced fibrotic lung tissue and primary murine alveolar epithelial Type II (ATII) cells treated with bleomycin. Furthermore, we discovered that TGF-β1 could induce the differentiation of lung resident mesenchymal stem cells (LR-MSCs) into fibroblasts, which may play an essential role in PF. LR-MSCs incubated with FGF-2 showed modest alterations in the expression of α-SMA and Vimentin. Moreover, in our study, we found that Wnt/β-catenin signaling was activated both in vitro and in vivo as a result of bleomycin treatment. Interestingly, we also found that suppression of the Wnt/β-catenin signaling could significantly attenuate bleomycin-induced PF accompanied with decreased expression of TGF-β1 and FGF-2 in vitro and in vivo. These results support that controlling the aberrant expression of TGF-β1 and FGF-2 via inhibition of Wnt/β-catenin signaling could serve as a potential therapeutic strategy for PF.

Regeneration of the lung: Lung stem cells and the development of lung mimicking devices

Inspired by the increasing burden of lung associated diseases in society and an growing demand to accommodate patients, great efforts by the scientific community produce an increasing stream of data that are focused on delineating the basic principles of lung development and growth, as well as understanding the biomechanical properties to build artificial lung devices. In addition, the continuing efforts to better define the disease origin, progression and pathology by basic scientists and clinicians contributes to insights in the basic principles of lung biology. However, the use of different model systems, experimental approaches and readout systems may generate somewhat conflicting or contradictory results. In an effort to summarize the latest developments in the lung epithelial stem cell biology, we provide an overview of the current status of the field. We first describe the different stem cells, or progenitor cells, residing in the homeostatic lung. Next, we focus on the plasticity of the different cell types upon several injury-induced activation or repair models, and highlight the regenerative capacity of lung cells. Lastly, we summarize the generation of lung mimics, such as air-liquid interface cultures, organoids and lung on a chip, that are required to test emerging hypotheses. Moreover, the increasing collaboration between distinct specializations will contribute to the eventual development of an artificial lung device capable of assisting reduced lung function and capacity in human patients.

Role of Wnt/β-Catenin Signaling in Epithelial Differentiation of Lung Resident Mesenchymal Stem Cells

Accumulating evidence has demonstrated that stem cells have the ability to repair the lung tissue injuries following either injection of cultured cells or bone marrow transplantation. As a result, increasing attention has focused on the lung resident mesenchymal stem cells (LR-MSCs) for repairing damaged lung tissues. Meanwhile, some studies have revealed that Wnt/β-catenin signaling plays an important role in the epithelial differentiation of mesenchymal stem cells (MSCs). In the current study, our aim was to explore the roles of Wnt/β-catenin signaling on cell proliferation and epithelial differentiation of LR-MSCs. We have successfully isolated the stem cell antigen (Sca)-1(+) CD45(-) CD31(-) cells which were proposed to be LR-MSCs by magnetic-activated cell sorting (MACS). Furthermore, we demonstrated the expression of epithelial markers on LR-MSCs following indirect co-culture of these cells with alveolar epithelial type II (ATII) cells, confirming the epithelial phenotype of LR-MSCs following co-culture. In order to clarify the regulatory mechanisms of Wnt/β-catenin signaling in epithelial differentiation of LR-MSCs, we measured the protein levels of several important members involved in Wnt/β-catenin signaling in the presence or absence of some canonical activators and inhibitors of the β-catenin pathways. In conclusion, our study demonstrated that Wnt/β-catenin signaling may be an essential mechanism underlying the regulation of epithelial differentiation of LR-MSCs.

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

INTRODUCTION

During the last few decades, cell-based therapies have shown great potential to treat patients with lung diseases. It has been proposed that the administration of cells into an injured lung could be considered as a therapeutic method to repair and replace lost lung tissue. Using this method, transplanted cells with the ability to proliferate and differentiate into alveolar cells, have been suggested as a therapeutic strategy for IPF treatment.

AREAS COVERED

In this review, the latest investigations using various types of cells for IPF therapy have been presented. The cells studied for cell-based therapies in IPF are lung alveolar epithelial cells, lung resident stem cells and exogenous adult stem cells such as MSCs.

EXPERT OPINION

After many years of investigation, the use of cell-based therapies to treat IPF is still at the experimental phase. Problems include bioethical issues, safety of cell transplantation, routes of delivery and the dose and timing of administration. Further investigations are necessary to establish the best strategy for using cell-based therapies effectively for the treatment of IPF.

Clinical Trials With Mesenchymal Stem Cells: An Update

In the last year, the promising features of mesenchymal stem cells (MSCs), including their regenerative properties and ability to differentiate into diverse cell lineages, have generated great interest among researchers whose work has offered intriguing perspectives on cell-based therapies for various diseases. Currently the most commonly used adult stem cells in regenerative medicine, MSCs, can be isolated from several tissues, exhibit a strong capacity for replication in vitro, and can differentiate into osteoblasts, chondrocytes, and adipocytes. However, heterogeneous procedures for isolating and cultivating MSCs among laboratories have prompted the International Society for Cellular Therapy (ISCT) to issue criteria for identifying unique populations of these cells. Consequently, the isolation of MSCs according to ISCT criteria has produced heterogeneous, nonclonal cultures of stromal cells containing stem cells with different multipotent properties, committed progenitors, and differentiated cells. Though the nature and functions of MSCs remain unclear, nonclonal stromal cultures obtained from bone marrow and other tissues currently serve as sources of putative MSCs for therapeutic purposes, and several findings underscore their effectiveness in treating different diseases. To date, 493 MSC-based clinical trials, either complete or ongoing, appear in the database of the US National Institutes of Health. In the present article, we provide a comprehensive review of MSC-based clinical trials conducted worldwide that scrutinizes biological properties of MSCs, elucidates recent clinical findings and clinical trial phases of investigation, highlights therapeutic effects of MSCs, and identifies principal criticisms of the use of these cells. In particular, we analyze clinical trials using MSCs for representative diseases, including hematological disease, graft-versus-host disease, organ transplantation, diabetes, inflammatory diseases, and diseases in the liver, kidney, and lung, as well as cardiovascular, bone and cartilage, neurological, and autoimmune diseases.

Stem Cells and Regenerative Medicine: Myth or Reality of the 21th Century

Since the 1960s and the therapeutic use of hematopoietic stem cells of bone marrow origin, there has been an increasing interest in the study of undifferentiated progenitors that have the ability to proliferate and differentiate into various tissues. Stem cells (SC) with different potency can be isolated and characterised. Despite the promise of embryonic stem cells, in many cases, adult or even fetal stem cells provide a more interesting approach for clinical applications. It is undeniable that mesenchymal stem cells (MSC) from bone marrow, adipose tissue, or Wharton's Jelly are of potential interest for clinical applications in regenerative medicine because they are easily available without ethical problems for their uses. During the last 10 years, these multipotent cells have generated considerable interest and have particularly been shown to escape to allogeneic immune response and be capable of immunomodulatory activity. These properties may be of a great interest for regenerative medicine. Different clinical applications are under study (cardiac insufficiency, atherosclerosis, stroke, bone and cartilage deterioration, diabetes, urology, liver, ophthalmology, and organ's reconstruction). This review focuses mainly on tissue and organ regeneration using SC and in particular MSC.

Nonadherent culture method downregulates stem cell antigen-1 expression in mouse bone marrow mesenchymal stem cells

Mesenchymal stem cells (MSCs) are primarily isolated by their adherence to plastic and their in vitro growth characteristics. Expansion of these cells from an adherent culture is the only method to obtain a sufficient number of cells for use in clinical practice and research. However, little is known with regard to the effect of adherence to plastic on the phenotype of the cells. In the present study, bone marrow CD45^-CD31^-CD44^- stem cell antigen (Sca)-1⁺ MSCs were sorted by flow cytometry and expanded in adherent cultures. The expression levels of the adhesion molecule, Sca-1, in the adherent cultures were compared with those from nonadherent cultures at different time points. The flow cytometry results indicated that the expression levels of Sca-1 decreased in the MSCs in the nonadherent cultures grown in ultra-low-adherent plates. Furthermore, the result was confirmed by quantitative polymerase chain reaction at the same time points. Therefore, the results demonstrated that the loss of plastic adherence downregulated the expression of Sca-1. The observations may provide novel insights into the molecular mechanisms underlying plastic adherent culture.

Intracellular surface-enhanced Raman scattering probes based on TAT peptide-conjugated Au nanostars for distinguishing the differentiation of lung resident mesenchymal stem cells

Lung resident mesenchymal stem cells (LR-MSCs) are important regulators of pathophysiological processes including tissue repair and fibrosis, inflammation, angiogenesis and tumor formation. Therefore, increasing attention has focused on the functional differentiation of LR-MSCs. However, the distinction between the undifferentiated and differentiated LR-MSCs, which are closely related and morphologically similar, is difficult to achieve by conventional methods. In this study, by employing the TAT Peptide-conjugated Au nanostars (AuNSs) as an intracellular probe, we developed a method for the identification of LR-MSC differentiation by surface-enhanced Raman scattering (SERS) spectroscopy. SERS spectra were analyzed using principal component analysis (PCA) that allowed unambiguous distinction of subtypes and monitoring of component changes during cellular differentiation. Furthermore, to ascertain whether co-culture with alveolar epithelial type II (ATII) cells and incubation with transform growth factor (TGF)-β were involved in regulating the differentiation of LR-MSCs, we investigated the protein expression levels of epithelial markers and fibroblastic markers on LR-MSCs. Our results demonstrated that co-culture with ATII cells or incubation with TGF-β could induce the differentiation of LR-MSCs as confirmed by SERS analysis, a method that is capable of noninvasive characterization of and distinction between subtypes of LR-MSCs during differentiation. We have provided a new tool that may facilitate stem cell research.