Sources, Characteristics, and Therapeutic Applications of Mesenchymal Cells in Tissue Engineering

Analysis of the role of perfusion, mechanical, and electrical stimulation in bioreactors for cardiac tissue engineering

Since cardiovascular diseases (CVDs) are globally one of the leading causes of death, of which myocardial infarction (MI) can cause irreversible damage and decrease survivors' quality of life, novel therapeutics are needed. Current approaches such as organ transplantation do not fully restore cardiac function or are limited. As a valuable strategy, tissue engineering seeks to obtain constructs that resemble myocardial tissue, vessels, and heart valves using cells, biomaterials as scaffolds, biochemical and physical stimuli. The latter can be induced using a bioreactor mimicking the heart's physiological environment. An extensive review of bioreactors providing perfusion, mechanical and electrical stimulation, as well as the combination of them is provided. An analysis of the stimulations' mechanisms and modes that best suit cardiac construct culture is developed. Finally, we provide insights into bioreactor configuration and culture assessment properties that need to be elucidated for its clinical translation.

Mesenchymal stem cells in autoimmune disease: A systematic review and meta-analysis of pre-clinical studies

Mesenchymal Stem Cells (MSCs) are of interest in the clinic because of their immunomodulation capabilities, capacity to act upstream of inflammation, and ability to sense metabolic environments. In standard physiologic conditions, they play a role in maintaining the homeostasis of tissues and organs; however, there is evidence that they can contribute to some autoimmune diseases. Gaining a deeper understanding of the factors that transition MSCs from their physiological function to a pathological role in their native environment, and elucidating mechanisms that reduce their therapeutic relevance in regenerative medicine, is essential. We conducted a Systematic Review and Meta-Analysis of human MSCs in preclinical studies of autoimmune disease, evaluating 60 studies that included 845 patient samples and 571 control samples. MSCs from any tissue source were included, and the study was limited to four autoimmune diseases: multiple sclerosis, rheumatoid arthritis, systemic sclerosis, and lupus. We developed a novel Risk of Bias tool to determine study quality for in vitro studies. Using the International Society for Cell & Gene Therapy's criteria to define an MSC, most studies reported no difference in morphology, adhesion, cell surface markers, or differentiation into bone, fat, or cartilage when comparing control and autoimmune MSCs. However, there were reported differences in proliferation. Additionally, 308 biomolecules were differentially expressed, and the abilities to migrate, invade, and form capillaries were decreased. The findings from this study could help to explain the pathogenic mechanisms of autoimmune disease and potentially lead to improved MSC-based therapeutic applications.

Differential expression of circular RNAs in interleukin 6-promoted osteogenic differentiation of human stem cells from apical papilla

INTRODUCTION

Studies have shown that interleukin 6 (IL-6) can regulate stem cell osteogenic differentiation; however, the exact mechanism is not clear. Circular RNAs (circRNAs) are closed circular non-coding RNAs that are involved in the process of stem cell osteogenic differentiation. Therefore, the purpose of this present study was to investigate the effect of IL-6 treatment on osteogenic differentiation of human apical tooth papillae stem cells (hSCAPs), and to detect the difference in circRNA expression using gene microarray technology.

METHODS

After extraction and identification of hSCAPs, alkaline phosphatase (ALP) activity, alizarin red staining, and calcium ion quantitative assay were used to determine the changes of ALP enzyme, mineralized nodules, and matrix calcium levels before and after IL-6 treatment of hSCAPs gene microarray technology was used to analyze the changes in circRNA expression levels before and after IL-6 induction of mineralization. The four selected circRNAs were validated by qRT-PCR. Moreover, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to predict the potential functions and biological signaling pathways of circRNAs. Finally, these data are integrated and analyzed to construct circRNA-microRNA-mRNA networks.

RESULTS

Alp and Alizarin red staining confirmed that IL-6 promoted the osteogenic differentiation of hSCAPs. The gene microarray results identified 132 differentially expressed circRNAs, of which 117 were upregulated and 15 were downregulated. Bioinformatic analysis predicted that the circRNA-406620/miR-103a-3p/FAT atypical cadherin 4 (FAT4) pathway might be involved in regulating IL-6 to promote osteogenic differentiation of hSCAPs.

CONCLUSION

Differentially expressed circRNAs might be closely involved in regulating IL-6 to promote osteogenic differentiation of hSCAPs.

Mesenchymal Stem Cell-Derived Exosomes and Their MicroRNAs in Heart Repair and Regeneration

Mesenchymal stem cells (MSCs) can be differentiated into cardiac, endothelial, and smooth muscle cells. Therefore, MSC-based therapeutic approaches have the potential to deal with the aftermaths of cardiac diseases. However, transplanted stem cells rarely survive in damaged myocardium, proposing that paracrine factors other than trans-differentiation may involve in heart regeneration. Apart from cytokines/growth factors, MSCs secret small, single-membrane organelles named exosomes. The MSC-secreted exosomes are enriched in lipids, proteins, nucleic acids, and microRNA (miRNA). There has been an increasing amount of data that confirmed that MSC-derived exosomes and their active molecule microRNA (miRNAs) regulate signaling pathways involved in heart repair/regeneration. In this review, we systematically present an overview of MSCs, their cardiac differentiation, and the role of MSC-derived exosomes and exosomal miRNAs in heart regeneration. In addition, biological functions regulated by MSC-derived exosomes and exosomal-derived miRNAs in the process of heart regeneration are reviewed.

Nitrosylation of β2-Tubulin Promotes Microtubule Disassembly and Differentiated Cardiomyocyte Beating in Ischemic Mice

BACKGROUND

Beating cardiomyocyte regeneration therapies have revealed as alternative therapeutics for heart transplantation. Nonetheless, the importance of nitric oxide (NO) in cardiomyocyte regeneration has been widely suggested, little has been reported concerning endogenous NO during cardiomyocyte differentiation.

METHODS

Here, we used P19CL6 cells and a Myocardiac infarction (MI) model to confirm NO-induced protein modification and its role in cardiac beating. Two tyrosine (Tyr) residues of β2-tubulin (Y106 and Y340) underwent nitrosylation (Tyr-NO) by endogenously generated NO during cardiomyocyte differentiation from pre-cardiomyocyte-like P19CL6 cells.

RESULTS

Tyr-NO-β2-tubulin mediated the interaction with Stathmin, which promotes microtubule disassembly, and was prominently observed in spontaneously beating cell clusters and mouse embryonic heart (E11.5d). In myocardial infarction mice, Tyr-NO-β2-tubulin in transplanted cells was closely related with cardiac troponin-T expression with their functional recovery, reduced infarct size and thickened left ventricular wall.

CONCLUSION

This is the first discovery of a new target molecule of NO, β2-tubulin, that can promote normal cardiac beating and cardiomyocyte regeneration. Taken together, we suggest therapeutic potential of Tyr-NO-β2-tubulin, for ischemic cardiomyocyte, which can reduce unexpected side effect of stem cell transplantation, arrhythmogenesis.

MMP13-Overexpressing Mesenchymal Stem Cells Enhance Bone Tissue Formation in the Presence of Collagen Hydrogel

BACKGROUND

Matrix metalloproteinases (MMPs) are proteins involved in the repair and remodeling the extracellular matrix (ECM). MMP13 is essential for bone development and healing through the remodeling of type I collagen (COL1), the main component of the ECM in bone tissue. Mesenchymal stem cells (MSCs)-based cell therapy has been considered a promising approach for bone regeneration because of their osteogenic properties. However, the approaches using MSC to completely regenerate bone tissue have been limited. To overcome the limitation, genetic engineering of MSC could be a strategy for promoting regeneration efficacy.

METHODS

We performed in vitro and in vivo experiments using MMP13-overexpressing MSCs in the presence of COL1. To examine MMP13-overexpressing MSCs in vivo, we prepared a fibrin/COL1-based hydrogel to encapsulate MSCs and subcutaneously implanted gel-encapsulated MSCs in nude mice. We found that the osteogenic marker genes, ALP and RUNX2, were upregulated in MMP13-overexpressing MSCs through p38 phosphorylation. In addition, MMP13 overexpression in MSCs stimulated the expression of integrin α3, which is up-stream receptor of p38, and substantially increased osteogenic differentiation potential of MSCs. Bone tissue formation in MMP13-overexpressing MSCs was significantly higher than that in control MSCs. Taken together, our findings demonstrate that MMP13 is not only an essential factor for bone development and bone healing but also has a pivotal role in promoting osteogenic differentiation of MSCs to induce bone formation.

CONCLUSION

MSCs Genetically engineered to overexpress MMP13, which have a powerful potential to differentiate into the osteogenic cells, might be beneficial in bone disease therapy.

Regeneration of periodontal bone defects with mesenchymal stem cells in animal models. Systematic review and meta-analysis

The aim of this study was to evaluate the efficacy of mesenchymal stem cells (MSCs) in the regeneration of periodontal bone defects in animal models. A systematic review and meta-analysis were conducted following the PRISMA guidelines, and the study was recorded in PROSPERO under reference number CDR42021247462. The PICO question was: is periodontal regeneration (cementum, periodontal ligament and alveolar bone) with MSCs more effective than other techniques? Three groups were considered: Group 1: MSCs alone or mixed with regenerative materials. Group 2: only regenerative materials. Group 3: no regenerative material nor MSCs. The search was conducted using MeSH with a total of 18 articles for qualitative analysis and 5 for quantitative analysis. For the meta-analysis, a modification of the effect size algorithm was developed, which considered a comparison of means between treatments using the Student's t sample distribution. When comparing the effect size between Group 1 and Group 2, the effect size for the new cementum was 2.83 mm with an estimated confidence interval of 95% (CI 95%) between 0.48 and 5.17 mm. When considering the fit to a random-effects model, the combined variance (τ²) was 6.1573 mm, with a standard deviation (SD) of 5.6008 mm and a percentage of total heterogeneity I² of 92.33% (p < 0.0001). For new bone, the effect size was 0.88 mm, CI 95% - 0.25 to 2.01 mm, τ² = 1.3108 mm (SD = 1.2021 mm) and I² = 80.46%, p = 0.0004). With regard to the new periodontal ligament, it was not possible for the meta-analysis to be performed. MSCs have a greater capacity for tissue regeneration in root cementum than in alveolar bone compared to other regenerative materials.

The Art of Stem Cell-Based Therapy

Potency assays represent crucial experiments at the hub of the comprehensive complexity surrounding cell therapy. Moreover, numerous factors beyond biological and scientific considerations are involved in achieving successful potency assays that fulfil regulatory authority approval for a new advanced therapy medicinal product. Though this can mean a frustratingly long period of discovery and development, progress in cell therapy is nowadays proceeding remarkably quickly, assisted by the potency assay rigorously placing emphasis on the need to critically analyse the key factor/s responsible for the therapeutic mechanism of action. History has shown that it can take many decades for there to be an improved understanding of a mechanism of action. Yet the chasing of precise targets has revolutionised medicine, with no clearer example than approaches to viral pandemics. The centuries involved in the eradication of smallpox have paved the way for an unprecedented pace of vaccine development for the Covid-19 pandemic. Such extraordinary accomplishments foster encouragement that similarly for stem cell-based therapy, our scientific knowledge will continue to improve apace. This chapter focuses on the art of experimentation and discovery, introducing potency assay requisites and numerous factors that can influence potency assay outcomes. A comprehensive understanding of potency assays and their development can hasten the provision of new cell therapies to help resolve burdensome diseases of unmet medical need.

Global scientific trends on the immunomodulation of mesenchymal stem cells in the 21st century: A bibliometric and visualized analysis

Background

Since the discovery of the immunomodulatory functions of mesenchymal stem cells (MSCs), their application in immunomodulation has attracted considerable attention, and an increasing number of studies have been conducted worldwide. Our research aimed to investigate the global status and trends in this field.

Methods

Publications on the immunomodulatory functions of MSCs from 1 January 2000 to 7 March 2022 were retrieved from the Web of Science Core Collection. The data were studied and indexed using the bibliometric methodology. Visualization analysis, co-authorship, co-occurrence analysis, and publication trends in MSC immunomodulation were conducted using the VOSviewer software.

Results

In total, 4,227 papers were included in the study. The number of publications and research interests has significantly increased globally. China published the highest number of related articles, while the US published articles with the highest number of citations. Stem Cell Research & Therapy had the highest number of publications. Sun Yat-sen University, Shanghai Jiao Tong University, Harvard University, and Seoul National University were the most contributive institutions. Furthermore, the studies were divided into four research hotspots for MSC immunomodulation: MSC immunomodulation in regenerative medicine, the effects and mechanisms of MSC immunomodulation, MSC therapy for immune diseases, and the cell source of MSCs.

Conclusion

This study indicates that the number of publications on MSC immunomodulation will increase in the future, and MSC immunomodulation mechanisms and clinical applications of MSC immunotherapy should be the next hotspots in this research field.

Advances in mesenchymal stromal cell therapy for acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) develops rapidly and has high mortality. ALI/ARDS is mainly manifested as acute or progressive hypoxic respiratory failure. At present, there is no effective clinical intervention for the treatment of ALI/ARDS. Mesenchymal stromal cells (MSCs) show promise for ALI/ARDS treatment due to their biological characteristics, easy cultivation, low immunogenicity, and abundant sources. The therapeutic mechanisms of MSCs in diseases are related to their homing capability, multidirectional differentiation, anti-inflammatory effect, paracrine signaling, macrophage polarization, the polarization of the MSCs themselves, and MSCs-derived exosomes. In this review, we discuss the pathogenesis of ALI/ARDS along with the biological characteristics and mechanisms of MSCs in the treatment of ALI/ARDS.

Cyclin-Dependent Kinase 1 Inhibition Potentiates the Proliferation of Tonsil-Derived Mesenchymal Stem Cells by Delaying Cellular Senescence

Mesenchymal stem cells (MSCs) have been widely used in tissue regeneration and stem cell therapy and are currently being tested in numerous clinical trials. Senescence-related changes in MSC properties have attracted considerable attention. Senescent MSCs exhibit a compromised potential for proliferation; senescence acts as a stress response that prevents the proliferation of dysfunctional cells by inducing an irreversible cell cycle arrest. Here, we established a senescent MSC model using senescence-associated β-galactosidase, proliferation, and cell cycle assays. We further identified novel biomarker candidates for old, senescent tonsil-derived MSCs (TMSCs) using transcriptomics. A plot of the cellular senescence pathway showed cyclin-dependent kinase 1 (CDK1; +8-fold) and CDK2 (+2-fold), and transforming growth factor beta 2 (TGFB2; +2-fold) showed significantly higher expression in old TMSCs than in young TMSCs. The CDK family was shown to be related to cell cycle and proliferation, as confirmed by quantitative RT-PCR. As replicative senescence of TMSCs, the gene and protein expression of CDK1 was significantly increased, which was further validated by inhibiting CDK1 using an inhibitor and siRNA. Taken together, we suggest that the CDK1 can be used as a selective senescence biomarker of MSCs and broaden the research criteria for senescent mechanisms.

The Progress of Stem Cell Therapy in Myocardial-Infarcted Heart Regeneration: Cell Sheet Technology

Various tissues, including the heart, cornea, bone, esophagus, bladder and liver, have been vascularized using the cell sheet technique. It overcomes the limitations of existing techniques by allowing small layers of the cell sheet to generate capillaries on their own, and it can also be used to vascularize tissue-engineered transplants. Cell sheets eliminate the need for traditional tissue engineering procedures such as isolated cell injections and scaffold-based technologies, which have limited applicability. While cell sheet engineering can eliminate many of the drawbacks, there are still a few challenges that need to be addressed. The number of cell sheets that can be layered without triggering core ischemia or hypoxia is limited. Even when scaffold-based technologies are disregarded, strategies to tackle this problem remain a substantial impediment to the efficient regeneration of thick, living three-dimensional cell sheets. In this review, we summarize the cell sheet technology in myocardial infarcted tissue regeneration.

Early Osteogenic Marker Expression in hMSCs Cultured onto Acid Etching-Derived Micro- and Nanotopography 3D-Printed Titanium Surfaces

Polyetheretherketone (PEEK) titanium composite (PTC) is a novel interbody fusion device that combines a PEEK core with titanium alloy (Ti6Al4V) endplates. The present study aimed to investigate the in vitro biological reactivity of human bone-marrow-derived mesenchymal stem cells (hBM-MSCs) to micro- and nanotopographies produced by an acid-etching process on the surface of 3D-printed PTC endplates. Optical profilometer and scanning electron microscopy were used to assess the surface roughness and identify the nano-features of etched or unetched PTC endplates, respectively. The viability, morphology and the expression of specific osteogenic markers were examined after 7 days of culture in the seeded cells. Haralick texture analysis was carried out on the unseeded endplates to correlate surface texture features to the biological data. The acid-etching process modified the surface roughness of the 3D-printed PTC endplates, creating micro- and nano-scale structures that significantly contributed to sustaining the viability of hBM-MSCs and triggering the expression of early osteogenic markers, such as alkaline phosphatase activity and bone-ECM protein production. Finally, the topography of 3D-printed PTC endplates influenced Haralick’s features, which in turn correlated with the expression of two osteogenic markers, osteopontin and osteocalcin. Overall, these data demonstrate that the acid-etching process of PTC endplates created a favourable environment for osteogenic differentiation of hBM-MSCs and may potentially have clinical benefit.

A Comparative In Vitro and In Vivo Study of Osteogenicity by Using Two Biomaterials and Two Human Mesenchymal Stem Cell Subtypes

Background: Bone repair induced by stem cells and biomaterials may represent an alternative to autologous bone grafting. Mesenchymal stromal/stem cells (MSCs), easily accessible in every human, are prototypical cells that can be tested, alone or with a biomaterial, for creating new osteoblasts. The aim of this study was to compare the efficiency of two biomaterials—biphasic calcium phosphate (BCP) and bioactive glass (BG)—when loaded with either adult bone marrow mesenchymal stem cells (BMMSCs) or newborn nasal ecto-mesenchymal stem cells (NE-MSCs), the latter being collected for further repair of lip cleft-associated bone loss.

Materials and Methods: BMMSCs were collected from two adults and NE-MSCs from two newborn infants. An in vitro study was performed in order to determine the best experimental conditions for adhesion, viability, proliferation and osteoblastic differentiation on BCP or BG granules. Bone-associated morphological changes and gene expression modifications were quantified using histological and molecular techniques. The in vivo study was based on the subcutaneous implantation in nude mice of the biomaterials, loaded or not with one of the two cell types. Eight weeks after, bone formation was assessed using histological and electron microscopy techniques.

Results: Both cell types—BMMSC and NE-MSC—display the typical stem cell surface markers—CD73+, CD90+, CD105+, nestin - and exhibit the MSC-associated osteogenic, chondrogenic and adipogenic multipotency. NE-MSCs produce less collagen and alkaline phosphatase than BMMSCs. At the transcript level, NE-MSCs express more abundantly three genes coding for bone sialoprotein, osteocalcin and osteopontin while BMMSCs produce extra copies of RunX2. BMMSCs and NE-MSCs adhere and survive on BCP and BG. In vivo experiments reveal that bone formation is only observed with BMMSCs transplanted on BCP biomaterial.

Conclusion: Although belonging to the same superfamily of mesenchymal stem cells, BMMSCs and NE-MSCs exhibit striking differences, in vitro and in vivo. For future clinical applications, the association of BMMSCs with BCP biomaterial seems to be the most promising.

Therapeutic Strategy of Mesenchymal-Stem-Cell-Derived Extracellular Vesicles as Regenerative Medicine

Extracellular vesicles (EVs) are lipid bilayer membrane particles that play critical roles in intracellular communication through EV-encapsulated informative content, including proteins, lipids, and nucleic acids. Mesenchymal stem cells (MSCs) are pluripotent stem cells with self-renewal ability derived from bone marrow, fat, umbilical cord, menstruation blood, pulp, etc., which they use to induce tissue regeneration by their direct recruitment into injured tissues, including the heart, liver, lung, kidney, etc., or secreting factors, such as vascular endothelial growth factor or insulin-like growth factor. Recently, MSC-derived EVs have been shown to have regenerative effects against various diseases, partially due to the post-transcriptional regulation of target genes by miRNAs. Furthermore, EVs have garnered attention as novel drug delivery systems, because they can specially encapsulate various target molecules. In this review, we summarize the regenerative effects and molecular mechanisms of MSC-derived EVs.