Single-Cell Transcriptomics of Human Mesenchymal Stem Cells Reveal Age-Related Cellular Subpopulation Depletion and Impaired Regenerative Function

Vibrational phenomics decoding of the stem cell stepwise aging process at single-cell resolution

We introduce vibrational spectroscopy to quantitatively measure the phenotypic heterogeneity of senescent stem cells in the aging process at the single cell level. Using an aging model of serially passaged human mesenchymal stem cells (MSCs), we characterized the phenotypic changes of MSCs during different aged stages and discovered a stepwise aging process with several distinct subtypes.

Age-related changes in human bone marrow mesenchymal stromal cells: morphology, gene expression profile, immunomodulatory activity and miRNA expression

Introduction

Mesenchymal stromal cells (MSC) are one of the main cellular components of bone marrow (BM) microenvironment. MSC play a key role in tissue regeneration, but they are also capable of immunomodulating activity. With host aging, MSC undergo age-related changes, which alter these functions, contributing to the set-up of "inflammaging", which is known to be the basis for the development of several diseases of the elderly, including cancer. However, there's few data investigating this facet of MSC, mainly obtained using murine models or replicative senescence. The aim of this research was to identify morphological, molecular and functional alterations of human bone marrow-derived MSC from young (yBM-MSC) and old (oBM-MSC) healthy donors.

Methods

MSC were identified by analysis of cell-surface markers according to the ISCT criteria. To evaluate response to inflammatory status, MSC were incubated for 24h in the presence of IL-1β, IFN-α, IFN-ɣ and TNF-α. Macrophages were obtained by differentiation of THP-1 cells through PMA exposure. For M1 polarization experiments, a 24h incubation with LPS and IFN-ɣ was performed. MSC were plated at the bottom of the co-culture transwell system for all the time of cytokine exposure. Gene expression was evaluated by real-time PCR after RNA extraction from BM-MSC or THP-1 culture. Secreted cytokines levels were quantitated through ELISA assays.

Results

Aging MSC display changes in size, morphology and granularity. Higher levels of β-Gal, reactive oxygen species (ROS), IL-6 and IL-8 and impaired colony-forming and cell cycle progression abilities were found in oBM-MSC. Gene expression profile seems to vary according to subjects' age and particularly in oBM-MSC seem to be characterized by an impaired immunomodulating activity, with a reduced inhibition of macrophage M1 status. The comparative analysis of microRNA (miRNA) expression in yBM-MSC and oBM-MSC revealed a significant difference for miRNA known to be involved in macrophage polarization and particularly miR-193b-3p expression is strongly increased after co-culture of macrophages with yBM-MSC.

Conclusion

There are profound differences in terms of morphology, gene and miRNA expression and immunomodulating properties among yBM-MSC and oBM-MSC, supporting the critical role of aging BM microenvironment on senescence, immune-mediated disorders and cancer pathogenesis.

Innovations in Stem Cell Therapy for Diabetic Wound Healing

Significance: The global burden of diabetic wounds, particularly diabetic foot ulcers, continues to have large economic and social impact throughout the world. Current strategies are not sufficient to overcome this burden of disease. Finding newer, more advanced regenerative cell and tissue-based strategies to reduce morbidity remains paramount. Recent Advances: Recent advances in stem cell therapies are discussed. We also highlight the practical issues of translating these advancing technologies into the clinical setting. Critical Issues: We discuss the use of somatic and induced pluripotent stem cells and the stromal vascular fraction, as well as innovations, including the use of 3D bioprinting of skin. We also explore related issues of using regenerative techniques in clinical practice, including the current regulatory landscape and translatability of in vivo research. Future Directions: Advances in stem cell manipulation showcase the best therapeutic resources available to enhance mechanisms of wound healing such as angiogenesis, cell proliferation, and collagen synthesis; potential methods include changing the scaffold microenvironment, including relative oxygen tension, and the use of gene modification and nanotechnology. Secretome engineering, particularly the use of extracellular vesicles, may be another potential cell-derived therapeutic that may enable use of cell-free translational therapy.

Small volume bone marrow aspirates with high progenitor cell concentrations maximize cell therapy dose manufacture and substantially reduce donor hemoglobin loss

BACKGROUND

Bone marrow (BM) transplantation is a life-saving therapy for hematological diseases, and the BM harbors also highly useful (progenitor) cell types for novel cell therapies manufacture. Yet, the BM collection technique is not standardized.

METHODS

Benchmarking our collection efficiency to BM collections worldwide (N = 1248), we noted a great variability of total nucleated cell (TNC) yields in BM products (HPC-M) with superior performance of our center, where we have implemented a small volume aspirate policy. Thus, we next prospectively aimed to assess the impact of BM collection technique on HPC-M quality. For each BM collection (N = 20 donors), small volume (3 mL) and large volume (10 mL) BM aspirates were sampled at 3 time points and analyzed for cell composition.

RESULTS

Compared to large volume aspirates, small volume aspirates concentrated more TNCs, immune cells, platelets, hematopoietic stem/progenitor cells, mesenchymal stromal cells (MSCs), and endothelial progenitors. Inversely, the hemoglobin concentration was higher in large volume aspirates indicating more hemoglobin loss. Manufacturing and dosing scenarios showed that small volume aspirates save up to 42% BM volume and 44% hemoglobin for HPC-M donors. Moreover, MSC production efficiency can be increased by more than 150%.

CONCLUSIONS

We propose to consider small volume BM aspiration as standard technique for BM collection.

Multi-omics analysis of human mesenchymal stem cells shows cell aging that alters immunomodulatory activity through the downregulation of PD-L1

Mesenchymal stem cells (MSCs) possess potent immunomodulatory activity and have been extensively investigated for their therapeutic potential in treating inflammatory disorders. However, the mechanisms underlying the immunosuppressive function of MSCs are not fully understood, hindering the development of standardized MSC-based therapies for clinical use. In this study, we profile the single-cell transcriptomes of MSCs isolated from adipose tissue (AD), bone marrow (BM), placental chorionic membrane (PM), and umbilical cord (UC). Our results demonstrate that MSCs undergo a progressive aging process and that the cellular senescence state influences their immunosuppressive activity by downregulating PD-L1 expression. Through integrated analysis of single-cell transcriptomic and proteomic data, we identify GATA2 as a regulator of MSC senescence and PD-L1 expression. Overall, our findings highlight the roles of cell aging and PD-L1 expression in modulating the immunosuppressive efficacy of MSCs and implicating perinatal MSC therapy for clinical applications in inflammatory disorders.

PPP3R1 Promotes MSCs Senescence by Inducing Plasma Membrane Depolarization and Increasing Ca2+ Influx

Aging of mesenchymal stem cells(MSCs) has been widely reported to be strongly associated with aging-related diseases, including osteoporosis (OP). In particular, the beneficial functions of mesenchymal stem cells decline with age, limiting their therapeutic efficacy in age-related bone loss diseases. Therefore, how to improve mesenchymal stem cell aging to treat age-related bone loss is the current research focus. However, the underlying mechanism remains unclear. In this study, protein phosphatase 3, regulatory subunit B, alpha isoform, calcineurin B, type I (PPP3R1) was found to accelerate the senescence of mesenchymal stem cells, resulting in reduced osteogenic differentiation and enhanced adipogenic differentiation in vitro. Mechanistically, PPP3R1 induces changes in membrane potential to promote cellular senescence by polarizing to depolarizing, increasing Ca²⁺ influx and activating downstream NFAT/ATF3/p53 signaling. In conclusion, the results identify a novel pathway of mesenchymal stem cell aging that may lead to novel therapeutic approaches for age-related bone loss.

Single-Cell RNA Sequencing Reveals Distinct Cardiac-Derived Stromal Cell Subpopulations

Human cardiac-derived c-kit+ stromal cells (CSCs) have demonstrated efficacy in preclinical trials for the treatment of heart failure and myocardial dysfunction. Unfortunately, large variability in patient outcomes and cell populations remains a problem. Previous research has demonstrated that the reparative capacity of CSCs may be linked to the age of the cells: CSCs derived from neonate patients increase cardiac function and reduce fibrosis. However, age-dependent differences between CSC populations have primarily been explored with bulk sequencing methods. In this work, we hypothesized that differences in CSC populations and subsequent cell therapy outcomes may arise from differing cell subtypes within donor CSC samples. We performed single-cell RNA sequencing on four neonatal CSC (nCSC) and five child CSC (cCSC) samples. Subcluster analysis revealed cCSC-enriched clusters upregulated in several fibrosis- and immune response-related genes. Module-based analysis identified upregulation of chemotaxis and ribosomal activity-related genes in nCSCs and upregulation of immune response and fiber synthesis genes in cCSCs. Further, we identified versican and integrin alpha 2 as potential markers for a fibrotic cell subtype. By investigating differences in patient-derived CSC populations at the single-cell level, this research aims to identify and characterize CSC subtypes to better optimize CSC-based therapy and improve patient outcomes.

Potential mechanisms and therapeutic targets of mesenchymal stem cell transplantation for ischemic stroke

Ischemic stroke is one of the major causes of death and disability in the world. Currently, most patients cannot choose intravenous thrombolysis or intravascular mechanical thrombectomy because of narrow therapeutic windows and severe complications. Stem cell transplantation is an emerging treatment and has been studied in various central nervous system diseases. Animal and clinical studies showed that transplantation of mesenchymal stem cells (MSCs) could alleviate neurological deficits and bring hope for ischemic stroke treatment. This article reviewed biological characteristics, safety, feasibility and efficacy of MSCs therapy, potential therapeutic targets of MSCs, and production process of Good Manufacturing Practices-grade MSCs, to explore the potential therapeutic targets of MSCs in the process of production and use and provide new therapeutic directions for ischemic stroke.

Physiological Systems in Promoting Frailty

Frailty is a complex syndrome affecting a growing sector of the global population as medical developments have advanced human mortality rates across the world. Our current understanding of frailty is derived from studies conducted in the laboratory as well as the clinic, which have generated largely phenotypic information. Far fewer studies have uncovered biological underpinnings driving the onset and progression of frailty, but the stage is set to advance the field with preclinical and clinical assessment tools, multiomics approaches together with physiological and biochemical methodologies. In this article, we provide comprehensive coverage of topics regarding frailty assessment, preclinical models, interventions, and challenges as well as clinical frameworks and prevalence. We also identify central biological mechanisms that may be at play including mitochondrial dysfunction, epigenetic alterations, and oxidative stress that in turn, affect metabolism, stress responses, and endocrine and neuromuscular systems. We review the role of metabolic syndrome, insulin resistance and visceral obesity, focusing on glucose homeostasis, adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and nicotinamide adenine dinucleotide (NAD⁺ ) as critical players influencing the age-related loss of health. We further focus on how immunometabolic dysfunction associates with oxidative stress in promoting sarcopenia, a key contributor to slowness, weakness, and fatigue. We explore the biological mechanisms involved in stem cell exhaustion that affect regeneration and may contribute to the frailty-associated decline in resilience and adaptation to stress. Together, an overview of the interplay of aging biology with genetic, lifestyle, and environmental factors that contribute to frailty, as well as potential therapeutic targets to lower risk and slow the progression of ongoing disease is covered. © 2022 American Physiological Society. Compr Physiol 12:1-46, 2022.

OUP accepted manuscript

Bronchopulmonary dysplasia (BPD) is a life-threatening condition in preterm infants with few effective therapies. Mesenchymal stem or stromal cells (MSCs) are a promising therapeutic strategy for BPD. The ideal MSC source for BPD prevention is however unknown. The objective of this study was to compare the regenerative effects of MSC obtained from bone marrow (BM) and umbilical cord tissue (UCT) in an experimental BPD model. In vitro, UCT-MSC demonstrated greater proliferation and expression of anti-inflammatory cytokines as compared to BM-MSC. Lung epithelial cells incubated with UCT-MSC conditioned media (CM) had better-wound healing following scratch injury. UCT-MSC CM and BM-MSC CM had similar pro-angiogenic effects on hyperoxia-exposed pulmonary microvascular endothelial cells. In vivo, newborn rats exposed to normoxia or hyperoxia (85% O₂) from postnatal day (P) 1 to 21 were given intra-tracheal (IT) BM or UCT-MSC (1 × 10⁶ cells/50 μL), or placebo (PL) on P3. Hyperoxia PL-treated rats had marked alveolar simplification, reduced lung vascular density, pulmonary vascular remodeling, and lung inflammation. In contrast, administration of both BM-MSC and UCT-MSC significantly improved alveolar structure, lung angiogenesis, pulmonary vascular remodeling, and lung inflammation. UCT-MSC hyperoxia-exposed rats however had greater improvement in some morphometric measures of alveolarization and less lung macrophage infiltration as compared to the BM-MSC-treated group. Together, these findings suggest that BM-MSC and UCT-MSC have significant lung regenerative effects in experimental BPD but UCT-MSC suppresses lung macrophage infiltration and promotes lung epithelial cell healing to a greater degree.

Single-cell RNA-seq of out-of-thaw mesenchymal stromal cells shows tissue-of-origin differences and inter-donor cell-cycle variations

Background

Human Mesenchymal stromal cells (hMSCs) from various tissue sources are widely investigated in clinical trials. These MSCs are often administered to patients immediately after thawing the cryopreserved product (out-of-thaw), yet little is known about the single-cell transcriptomic landscape and tissue-specific differences of out-of-thaw human MSCs.

Methods

13 hMSC samples derived from 10 “healthy” donors were used to assess donor variability and tissue-of-origin differences in single-cell gene expression profiles. hMSCs derived and expanded from the bone marrow (BM) or cord tissue (CT) underwent controlled-rate freezing for 24 h. Cells were then transferred to the vapor phase of liquid nitrogen for cryopreservation. hMSCs cryopreserved for at least one week, were characterized immediately after thawing using a droplet-based single-cell RNA sequencing method. Data analysis was performed with SC3 and SEURAT pipelines followed by gene ontology analysis.

Results

scRNA-seq analysis of the hMSCs revealed two major clusters of donor profiles, which differ in immune-signaling, cell surface properties, abundance of cell-cycle related transcripts, and metabolic pathways of interest. Within-sample transcriptomic heterogeneity is low. We identified numerous differentially expressed genes (DEGs) that are associated with various cellular functions, such as cytokine signaling, cell proliferation, cell adhesion, cholesterol/steroid biosynthesis, and regulation of apoptosis. Gene-set enrichment analyses indicated different functional pathways in BM vs. CT hMSCs. In addition, MSC-batches showed significant variations in cell cycle status, suggesting different proliferative vs. immunomodulatory potential. Several potential transcript-markers for tissue source differences were identified for further investigation in future studies. In functional assays, both BM and CT MSCs suppressed macrophage TNFα secretion upon interferon stimulation. However, differences between donors, tissue-of-origin, and cell cycle are evident in both TNF suppression and cytokine secretion.

Conclusions

This study shows that donor differences in hMSC transcriptome are minor relative to the intrinsic differences in tissue-of-origin. hMSCs with different transcriptomic profiles showed potential differences in functional characteristics. These findings contribute to our understanding of tissue origin-based differences in out-of-thaw therapeutic hMSC products and assist in the identification of cells with immune-regulatory or survival potential from a heterogeneous MSC population. Our results form the basis of future studies in correlating single-cell transcriptomic markers with immunomodulatory functions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02627-9.

Patient Age and Cell Concentration Influence Prevalence and Concentration of Progenitors in Bone Marrow Aspirates: An Analysis of 436 Patients

BACKGROUND

Connective tissue progenitors (CTPs) resident in native tissues serve as biological building blocks in tissue repair and remodeling processes. Methods for analysis and reporting on CTP quantity and quality are essential for defining optimal cell sources and donor characteristics and the impact of cell processing methods for cell therapy applications. The present study examines the influence of donor characteristics and cell concentration (nucleated cells/mL) on CTP prevalence (CTPs/million nucleated cells) and CTP concentration (CTPs/mL) in bone marrow aspirates (BMAs).

METHODS

Iliac crest bone marrow was aspirated from 436 patients during elective total knee or hip arthroplasty. Bone marrow-derived nucleated cells were plated at a density of 1.19 × 105 cells/cm2. Colony-forming unit analysis was performed on day 6.

RESULTS

Large variation was seen between donors. Age (p < 0.05) and cell concentration (p < 0.001) significantly influenced CTP prevalence and CTP concentration. For every 1-year increase in age, the odds of having at least an average CTP prevalence and CTP concentration decreased by 1.5% and 1.6%, respectively. For every 1 million cells/mL increase in cell concentration, the odds of having at least an average CTP prevalence and CTP concentration increased by 2.2% and 7.9%, respectively. Sex, race, body mass index (BMI), and the presence of osteoporosis did not influence CTP prevalence or CTP concentration.

CONCLUSIONS

BMA-derived CTPs were obtained from all patient groups. CTP prevalence and CTP concentration decreased with age. Cell concentration decreased with age and positively correlated with total CTP prevalence and CTP concentration. The mean CTP concentration in patients >60 years of age was a third of the CTP concentration in patients <30 years of age.

CLINICAL RELEVANCE

Proper BMA techniques are necessary to obtain a high-quality yield and composition of cells and CTPs. The reduced CTP concentration and CTP prevalence in the elderly may be mitigated by the use of cell processing methods that increase CTP concentration and CTP prevalence (e.g., by removing red blood cells, serum, and non-CTPs or by increasing aspirate volumes). Cell concentration in the BMA can be measured at the point of care and is an appropriate initial assessment of the quality of BMA.

Senolytics improve bone forming potential of bone marrow mesenchymal stem cells from aged mice

The osteogenic potential of bone marrow mesenchymal stem cells (BMSCs) declines dramatically with aging. By using a calvarial defect model, we showed that a senolytic cocktail (dasatinib+quercetin; D + Q) improved osteogenic capacity of aged BMSC both in vitro and in vivo. The study presented a model to assess strategies to improve bone-forming potential on aged BMSCs. D + Q might hold promise for improving BMSC function in aged populations.

Strategies to Identify Mesenchymal Stromal Cells in Minimally Manipulated Human Bone Marrow Aspirate Concentrate Lack Consensus

BACKGROUND

There is a need to identify and quantify mesenchymal stromal cells (MSCs) in human bone marrow aspirate concentrate (BMAC) source tissues, but current methods to do so were established in cultured cell populations. Given that surface marker and gene expression change in cultured cells, it is doubtful that these strategies are valid to quantify MSCs in fresh BMAC.

PURPOSE

To establish the presence, quantity, and heterogeneity of BMAC-derived MSCs in minimally manipulated BMAC using currently available strategies.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Five published strategies to identify MSCs were compared for suitability and efficiency to quantify clinical-grade BMAC-MSCs and cultured MSCs at the single cell transcriptome level on BMAC samples being used clinically from 15 orthopaedic patients and on 1 cultured MSC sample. Strategies included (1) the guidelines by the International Society for Cellular Therapy (ISCT), (2) CD271 expression, (3) the Ghazanfari et al transcriptional profile, (4) the Jia et al transcriptional profile, and (5) the Silva et al transcriptional profile.

RESULTS

ISCT guidelines did not identify any MSCs in BMAC at the transcriptional level and only 1 in 9 million cells at the protein level. Of 12,850 BMAC cells, 9 expressed the CD271 gene. Only 116 of 396 Ghazanfari genes were detected in BMAC, whereas no cells expressed all of them. No cells expressed all Jia genes, but 25 cells expressed at least 13 of 22. No cells expressed all Silva genes, but 19 cells expressed at least 8 of 23. Most importantly, the liberalized strategies tended to identify different cells and most of them clustered with immune cells.

CONCLUSION

Currently available methods need to be liberalized to identify any MSCs in fresh human BMAC and lack consensus at the single cell transcriptome and protein expression levels. These different cells should be isolated and challenged to establish phenotypic differences.

CLINICAL RELEVANCE

This study demonstrated that improved strategies to quantify MSC concentrations in BMAC for clinical applications are urgently needed. Until then, injected minimally manipulated MSC doses should be reported as rough estimates or as unknown.

More Human BM-MSC With Similar Subpopulation Composition and Functional Characteristics Can Be Produced With a GMP-Compatible Fabric Filter System Compared to Density Gradient Technique

Background

Mesenchymal stromal cells (MSCs), multipotent progenitors that can be isolated from a variety of different tissues, are becoming increasingly important as cell therapeutics targeting immunopathologies and tissue regeneration. Current protocols for MSC isolation from bone marrow (BM) rely on density gradient centrifugation (DGC), and the production of sufficient MSC doses is a critical factor for conducting clinical MSC trials. Previously, a Good Manufacturing Practice (GMP)–compatible non-woven fabric filter device system to isolate MSCs was developed to increase the MSC yield from the BM. The aim of our study was to compare high-resolution phenotypic and functional characteristics of BM-MSCs isolated with this device and with standard DGC technology.

Methods

Human BM samples from 5 donors were analyzed. Each sample was divided equally, processing by DGC, and with the filter device. Stem cell content was assessed by quantification of colony-forming units fibroblasts (CFU-F). Immunophenotype was analyzed by multicolor flow cytometry. In vitro trilineage differentiation potential, trophic factors, and IDO-1 production were assessed. Functionally, immunomodulatory potential, wound healing, and angiogenesis were assayed in vitro.

Results

The CFU-F yield was 15-fold higher in the MSC preparations isolated with the device compared to those isolated by DGC. Consequently, the MSC yield that could be manufactured at passage 3 per mL collected BM was more than 10 times higher in the device group compared to DGC (1.65 × 10⁹ vs. 1.45 × 10⁸). The immunomodulatory potential and IDO-1 production showed donor-to-donor variabilities without differences between fabric filter-isolated and DGC-isolated MSCs. The results from the wound closure assays, the tube formation assays, and the trilineage differentiation assays were similar between the groups with respect to the isolation method. Sixty-four MSC subpopulations could be quantified with CD140a⁺CD119⁺CD146⁺ as most common phenotype group, and CD140a⁺CD119⁺CD146⁺MSCA-1^–CD106^–CD271^– and CD140a⁺CD119⁺CD146^–MSCA-1^–CD106^–CD271^– as most frequent MSC subpopulations. As trophic factors hepatocyte growth factor, epidermal growth factor, brain-derived neurotrophic factor, angiopoietin-1, and vascular endothelial growth factor A could be detected in both groups with considerable variability between donors, but independent of the respective MSC isolation technique.

Conclusion

The isolation of MSCs using a GMP-compatible fabric filter system device resulted in higher yield of CFU-F, producing substantially more MSCs with similar subpopulation composition and functional characteristics as MSCs isolated by DGC.

Targeting Stem Cells in Chronic Inflammatory Diseases

Mesenchymal stem cell (MSC) dysfunction is a serious complication in ageing and age-related inflammatory diseases such as type 2 diabetes mellitus. Inflammation and oxidative stress-induced cellular senescence alter the immunomodulatory ability of MSCs and hamper their pro-regenerative function, which in turn leads to an increase in disease severity, maladaptive tissue damage and the development of comorbidities. Targeting stem/progenitor cells to restore their function and/or protect them against impairment could thus improve healing outcomes and significantly enhance the quality of life for diabetic patients. This review discusses the dysregulation of MSCs' immunomodulatory capacity in the context of diabetes mellitus and focuses on intervention strategies aimed at MSC rejuvenation. Research pertaining to the potential therapeutic use of either pharmacological agents (NFкB antagonists), natural products (phytomedicine) or biological agents (exosomes, probiotics) to improve MSC function is discussed and an overview of the most pertinent methodological considerations given. Based on in vitro studies, numerous anti-inflammatory agents, antioxidants and biological agents show tremendous potential to revitalise MSCs. An integrated systems approach and a thorough understanding of complete disease pathology are however required to identify feasible candidates for in vivo targeting of MSCs.

A Subpopulation of Schwann Cell-Like Cells With Nerve Regeneration Signatures Is Identified Through Single-Cell RNA Sequencing

Schwann cell-like cells (SCLCs) derived from human amniotic mesenchymal stem cells (hAMSCs) have been shown to promote peripheral nerve regeneration, but the underlying molecular mechanism was still poorly understood. In order to investigate the heterogeneity and potential molecular mechanism of SCLCs in the treatment of peripheral nerve regeneration at a single cell level, single-cell RNA sequencing was applied to profile single cell populations of hAMSCs and SCLCs. We profiled 6,008 and 5,140 single cells from hAMSCs and SCLCs, respectively. Based on bioinformatics analysis, pathways associated with proliferation, ECM organization, and tissue repair were enriched within both populations. Cell cycle analysis indicated that single cells within these two populations remained mostly in the G0/G1 phase. The transformation of single cells from hAMSCs to SCLCs was characterized by pseudotime analysis. Furthermore, we identified a subpopulation of SCLCs that highly expressed genes associated with Schwann cell proliferation, migration, and survival, such as JUN, JUND, and NRG1., Genes such as PTGS2, PITX1, VEGFA, and FGF2 that promote nerve regeneration were also highly expressed in single cells within this subpopulation, and terms associated with inflammatory and tissue repair were enriched in this subpopulation by pathway enrichment analysis. Our results indicate that a subpopulation of SCLCs with nerve regeneration signatures may be the key populations that promote nerve regeneration.

Aging of Bone Marrow Mesenchymal Stromal Cells: Hematopoiesis Disturbances and Potential Role in the Development of Hematologic Cancers

Simple Summary

As for many other cancers, the risk of developing hematologic malignancies increases considerably as people age. In recent years, a growing number of studies have highlighted the influence of the aging microenvironment on hematopoiesis and tumor progression. Mesenchymal stromal cells are a major player in intercellular communication inside the bone marrow microenvironment involved in hematopoiesis support. With aging, their functions may be altered, leading to hematopoiesis disturbances which can lead to hematologic cancers. A good understanding of the mechanisms involved in mesenchymal stem cell aging and the consequences on hematopoiesis and tumor progression is therefore necessary for a better comprehension of hematologic malignancies and for the development of therapeutic approaches.

Abstract

Aging of bone marrow is a complex process that is involved in the development of many diseases, including hematologic cancers. The results obtained in this field of research, year after year, underline the important role of cross-talk between hematopoietic stem cells and their close environment. In bone marrow, mesenchymal stromal cells (MSCs) are a major player in cell-to-cell communication, presenting a wide range of functionalities, sometimes opposite, depending on the environmental conditions. Although these cells are actively studied for their therapeutic properties, their role in tumor progression remains unclear. One of the reasons for this is that the aging of MSCs has a direct impact on their behavior and on hematopoiesis. In addition, tumor progression is accompanied by dynamic remodeling of the bone marrow niche that may interfere with MSC functions. The present review presents the main features of MSC senescence in bone marrow and their implications in hematologic cancer progression.

FZD5 regulates cellular senescence in human mesenchymal stem/stromal cells

Human mesenchymal stem/stromal cells (hMSCs) have garnered enormous interest as a potential resource for cell‐based therapies. However, the molecular mechanisms regulating senescence in hMSCs remain unclear. To elucidate these mechanisms, we performed gene expression profiling to compare clonal immature MSCs exhibiting multipotency with less potent MSCs. We found that the transcription factor Frizzled 5 (FZD5) is expressed specifically in immature hMSCs. The FZD5 cell surface antigen was also highly expressed in the primary MSC fraction (LNGFR⁺THY‐1⁺) and cultured MSCs. Treatment of cells with the FZD5 ligand WNT5A promoted their proliferation. Upon FZD5 knockdown, hMSCs exhibited markedly attenuated proliferation and differentiation ability. The observed increase in the levels of senescence markers suggested that FZD5 knockdown promotes cellular senescence by regulating the noncanonical Wnt pathway. Conversely, FZD5 overexpression delayed cell cycle arrest during the continued culture of hMSCs. These results indicated that the intrinsic activation of FZD5 plays an essential role in negatively regulating senescence in hMSCs and suggested that controlling FZD5 signaling offers the potential to regulate hMSC quality and improve the efficacy of cell‐replacement therapies using hMSCs.

Mesenchymal Stromal Cells as Critical Contributors to Tissue Regeneration

Adult stem cells that are tightly regulated by the specific microenvironment, or the stem cell niche, function to maintain tissue homeostasis and regeneration after damage. This demands the existence of specific niche components that can preserve the stem cell pool in injured tissues and restore the microenvironment for their subsequent appropriate functioning. This role may belong to mesenchymal stromal cells (MSCs) due to their resistance to damage signals and potency to be specifically activated in response to tissue injury and promote regeneration by different mechanisms. Increased amount of data indicate that activated MSCs are able to produce factors such as extracellular matrix components, growth factors, extracellular vesicles and organelles, which transiently substitute the regulatory signals from missing niche cells and restrict the injury-induced responses of them. MSCs may recruit functional cells into a niche or differentiate into missing cell components to endow a niche with ability to regulate stem cell fates. They may also promote the dedifferentiation of committed cells to re-establish a pool of functional stem cells after injury. Accumulated evidence indicates the therapeutic promise of MSCs for stimulating tissue regeneration, but the benefits of administered MSCs demonstrated in many injury models are less than expected in clinical studies. This emphasizes the importance of considering the mechanisms of endogenous MSC functioning for the development of effective approaches to their pharmacological activation or mimicking their effects. To achieve this goal, we integrate the current ideas on the contribution of MSCs in restoring the stem cell niches after damage and thereby tissue regeneration.

Adipogenesis, Osteogenesis, and Chondrogenesis of Human Mesenchymal Stem/Stromal Cells: A Comparative Transcriptome Approach

Adipogenesis, osteogenesis and chondrogenesis of human mesenchymal stem/stromal cells (MSC) are complex and highly regulated processes. Over the years, several studies have focused on understanding the mechanisms involved in the MSC commitment to the osteogenic, adipogenic and/or chondrogenic phenotypes. High-throughput methodologies have been used to investigate the gene expression profile during differentiation. Association of data analysis of mRNAs, microRNAs, circular RNAs and long non-coding RNAs, obtained at different time points over these processes, are important to depict the complexity of differentiation. This review will discuss the results that were highlighted in transcriptome analyses of MSC undergoing adipogenic, osteogenic and chondrogenic differentiation. The focus is to shed light on key molecules, main signaling pathways and biological processes related to different time points of adipogenesis, osteogenesis and chondrogenesis.

Human Mesenchymal Stromal Cell (MSC) Characteristics Vary Among Laboratories When Manufactured From the Same Source Material: A Report by the Cellular Therapy Team of the Biomedical Excellence for Safer Transfusion (BEST) Collaborative

Background

Culture-derived mesenchymal stromal cells (MSCs) exhibit variable characteristics when manufactured using different methods and different source materials. The purpose of this study was to assess the impact on MSC characteristics when different laboratories propagated MSCs from cultures initiated with BM aliquots derived from the same donor source material.

Methods and Methods

Five aliquots from each of three different BM donors were distributed to five independent laboratories. Three laboratories plated whole BM and two laboratories a mononuclear BM cell fraction. Four laboratories cultured in media supplemented with fetal bovine serum (FBS) and one laboratory used human platelet lysate (hPL). Initial cell seeding densities (i.e., P0) ranged from 19.7 × 10³/cm²–282 × 10³/cm² and for second seeding (i.e., P1) 0.05 × 10³–5.1 × 10³ cells/cm². Post-thawed MSCs from each laboratory were analyzed for cell viability, immunophenotype, tri-lineage differentiation, fibroblast colony-forming units (CFU-F), gene expression, and immunosuppressive activity.

Results

Transit times from BM collection to receipt by laboratories located in the United States ranged from 16.0–30.0 h and from 41.5–71.5 h for a laboratory in Asia. Post-thaw culture derived MSCs rom BM #1, #2, and #3 exhibited viabilities that ranged from 74–92%, 61–96%, and 23–90%, respectively. CFU activity from BM #1, #2, and #3 per 200 MSCs plated averaged 45.1 ± 21.4, 49.3 ± 26.8 and 14.9 ± 13.3, respectively. No substantial differences were observed in immunophenotype, and immunosuppressive activities. Global gene expression profiles of MSCs revealed transcriptome differences due to different inter-laboratory methods and to donor source material with the center effects showing greater molecular differences than source material.

Conclusion

Functional and molecular differences exist among MSCs produced by different centers even when the same BM starting material is used to initiate cultures. These results indicated that manufacturing of MSCs by five independent centers contributed more to MSC variability than did the source material of the BM used in this study. Thus, emphasizing the importance of establishing worldwide standards to propagate MSCs for clinical use.

Stammzellen in der Regenerativen Medizin – Translationale Hürden und Möglichkeiten zur Überwindung

Der Einsatz von mesenchymalen Stammzellen in der regenerativen Medizin wird immer populärer. Nichtsdestotrotz ist ihre Anwendung im klinischen Alltag noch immer limitiert. Zahlreiche ethische, rechtliche und translationale Probleme sowie Ungewissheit bzgl. der Sicherheit hemmen noch immer die Entstehung von entsprechenden Therapien aus vielversprechenden wissenschaftlichen Ansätzen.

Diese Arbeit soll die Hauptprobleme bei der Translation von stammzellbasierten Therapien aus der Grundlagenforschung und Präklinik in den klinischen Alltag darstellen, sowie Ansätze aufzeigen, diese zu überwinden.

Single-cell RNA-seq highlights heterogeneity in human primary Wharton's jelly mesenchymal stem/stromal cells cultured in vitro

BACKGROUND

Mesenchymal stem/stromal cells (MSCs) are multipotent cells with a promising application potential in regenerative medicine and immunomodulation. However, MSCs cultured in vitro exhibit functional heterogeneity. The underlying molecular mechanisms that define MSC heterogeneity remain unclear.

METHODS

We investigated the gene expression profile via single-cell RNA sequencing (scRNA-seq) of human primary Wharton's jelly-derived MSCs (WJMSCs) cultured in vitro from three donors. We also isolated CD142+ and CD142- WJMSCs based on scRNA-seq data and compared their proliferation capacity and "wound healing" potential in vitro. Meanwhile, we analyzed publicly available adipose-derived MSC (ADMSCs) scRNA-seq data and performed transcriptome comparison between WJMSCs and ADMSCs at the single-cell level.

RESULTS

GO enrichment analysis of highly variable genes (HVGs) obtained from WJMSCs revealed that these genes are significantly enriched in extracellular region with binding function, involved in developmental process, signal transduction, cell proliferation, etc. Pathway analysis showed that these HVGs are associated with functional characteristics of classic MSCs, such as inflammation mediated by chemokine and cytokine signaling, integrin signaling, and angiogenesis. After regressing out the batch and cell cycle effects, these HVGs were used for dimension reduction and clustering analysis to identify candidate subpopulations. Differentially expressed gene analysis revealed the existence of several distinct subpopulations of MSCs that exhibit diverse functional characteristics related to proliferation, development, and inflammation response. In line with our data, sorted CD142+ and CD142- WJMSCs showed distinct proliferation capacity as well as "wound healing" potential. Although WJMSCs and ADMSCs were derived from different tissues and were displaying different differentiation potencies, their HVGs were largely overlapped and had similar functional enrichment.

CONCLUSION

HVGs identified in MSCs are associated with classic MSC function. Regarding therapeutic potential, these genes are associated with functional characteristics, on which the MSC clinical application were theoretically based, such as development and inflammation response. Altogether, these HVGs hold the potential to be used as candidate markers for further potency association studies.

Transplanting cells from old but not young donors causes physical dysfunction in older recipients

Adipose-derived mesenchymal stem cell (ADSC)-based regenerative therapies have shown potential for use in many chronic diseases. Aging diminishes stem cell regenerative potential, yet it is unknown whether stem cells from aged donors cause adverse effects in recipients. ADSCs can be obtained using minimally invasive approaches and possess low immunogenicity. Nevertheless, we found that transplanting ADSCs from old donors, but not those from young donors, induces physical dysfunction in older recipient mice. Using single-cell transcriptomic analysis, we identified a naturally occurring senescent cell-like population in ADSCs primarily from old donors that resembles in vitro-generated senescent cells with regard to a number of key pathways. Our study reveals a previously unrecognized health concern due to ADSCs from old donors and lays the foundation for a new avenue of research to devise interventions to reduce harmful effects of ADSCs from old donors.

Reprogramming of human fibroblasts into osteoblasts by insulin-like growth factor-binding protein 7

The induced pluripotent stem cell (iPSC) is a promising cell source for tissue regeneration. However, the therapeutic value of iPSC technology is limited due to the complexity of induction protocols and potential risks of teratoma formation. A trans-differentiation approach employing natural factors may allow better control over reprogramming and improved safety. We report here a novel approach to drive trans-differentiation of human fibroblasts into functional osteoblasts using insulin-like growth factor binding protein 7 (IGFBP7). We initially determined that media conditioned by human osteoblasts can induce reprogramming of human fibroblasts to functional osteoblasts. Proteomic analysis identified IGFBP7 as being significantly elevated in media conditioned with osteoblasts compared with those with fibroblasts. Recombinant IGFBP7 induced a phenotypic switch from fibroblasts to osteoblasts. The switch was associated with senescence and dependent on autocrine IL-6 signaling. Our study supports a novel strategy for regenerating bone by using IGFBP7 to trans-differentiate fibroblasts to osteoblasts.

Trajectories of Aging: How Systems Biology in Yeast Can Illuminate Mechanisms of Personalized Aging

All organisms age, but the extent to which all organisms age the same way remains a fundamental unanswered question in biology. Across species, it is now clear that at least some aspects of aging are highly conserved and are perhaps universal, but other mechanisms of aging are private to individual species or sets of closely related species. Within the same species, however, it has generally been assumed that the molecular mechanisms of aging are largely invariant from one individual to the next. With the development of new tools for studying aging at the individual cell level in budding yeast, recent data has called this assumption into question. There is emerging evidence that individual yeast mother cells may undergo fundamentally different trajectories of aging. Individual trajectories of aging are difficult to study by traditional population level assays, but through the application of systems biology approaches combined with novel microfluidic technologies, it is now possible to observe and study these phenomena in real time. Understanding the spectrum of mechanisms that determine how different individuals age is a necessary step toward the goal of personalized geroscience, where healthy longevity is optimized for each individual.

Recent advances in understanding mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are among of the most studied cell type for cellular therapy thanks to the ease of isolation, cultivation, and the high ex vivo expansion potential. In 2018, the European Medicines Agency finally granted the first marketing authorization for an MSC product. Despite the numerous promising results in preclinical studies, translation into routine practice still lags behind: therapeutic benefits of MSCs are not as satisfactory in clinical trial settings as they appear to be in preclinical models. The bench-to-bedside-and-back approach and careful evaluation of discrepancies between preclinical and clinical results have provided valuable insights into critical components of MSC manufacturing, their mechanisms of action, and how to evaluate and quality-control them. We sum up these past developments in the introductory section (“Mesenchymal stromal cells: name follows function”). From the huge amount of information, we then selected a few examples to illustrate challenges and opportunities to improve MSCs for clinical purposes. These include tissue origin of MSCs, MSC culture conditions, immune compatibility, and route of application and dosing. Finally, we add some information on MSC mechanisms of action and translation into potency assays and give an outlook on future perspectives raising the question of whether the future clinical product may be cell-based or cell-derived.

Mesenchymal stem cells for treatment of musculoskeletal disease in horses: Relative merits of allogeneic versus autologous stem cells

Mesenchymal stem cells (MSCs) are widely used for treatment of musculoskeletal diseases in horses, but there is ongoing debate regarding the relative safety and efficacy of allogeneic MSCs, compared with autologous equine MSCs. This review summarises the currently available published data regarding the therapeutic use of autologous and allogeneic MSCs in horses. Arguments that have been advanced against the use of allogeneic MSCs include higher risk of immunological reactions and shorter cell survival times following injection. Arguments favouring the use of allogeneic MSCs include the ability to bank cells and reduce the time to treatment, to collect MSCs from younger donor animals and the ability to manipulate banked cells prior to administration. In vitro studies and a limited set of experimental in vivo studies have indicated that adverse immunological reactions may occur when allogeneic MSCs are administered to horses. However, newer studies lack evidence of inflammatory reactions or adverse clinical responses when allogeneic MSCs are administered and compared with autologous MSCs. Thus, while the relative merits of allogeneic vs autologous MSCs for treatment of musculoskeletal injuries in horses have not been fully established, accumulating evidence from studies in horses suggests that allogeneic MSCs maybe a safe alternative to autologous MSCs. Large, properly designed, randomised trials in addition to careful immunological evaluation of short-term and long-term, local and systemic immune responses are needed to more fully resolve the issue.

Multi-Parameter Analysis of Biobanked Human Bone Marrow Stromal Cells Shows Little Influence for Donor Age and Mild Comorbidities on Phenotypic and Functional Properties

Heterogeneous populations of human bone marrow-derived stromal cells (BMSC) are among the most frequently tested cellular therapeutics for treating degenerative and immune disorders, which occur predominantly in the aging population. Currently, it is unclear whether advanced donor age and commonly associated comorbidities affect the properties of ex vivo-expanded BMSCs. Thus, we stratified cells from adult and elderly donors from our biobank (n = 10 and n = 13, mean age 38 and 72 years, respectively) and compared their phenotypic and functional performance, using multiple assays typically employed as minimal criteria for defining multipotent mesenchymal stromal cells (MSCs). We found that BMSCs from both cohorts meet the standard criteria for MSC, exhibiting similar morphology, growth kinetics, gene expression profiles, and pro-angiogenic and immunosuppressive potential and the capacity to differentiate toward adipogenic, chondrogenic, and osteogenic lineages. We found no substantial differences between cells from the adult and elderly cohorts. As positive controls, we studied the impact of in vitro aging and inflammatory cytokine stimulation. Both conditions clearly affected the cellular properties, independent of donor age. We conclude that in vitro aging rather than in vivo donor aging influences BMSC characteristics.

The Immunomodulatory Potential of Wharton's Jelly Mesenchymal Stem/Stromal Cells

The benefits attributed to mesenchymal stem/stromal cells (MSC) in cell therapy applications are mainly attributed to the secretion of factors, which exhibit immunomodulatory and anti-inflammatory effects and stimulate angiogenesis. Despite the desirable features such as high proliferation levels, multipotency, and immune response regulation, there are important variables that must be considered. Although presenting similar morphological aspects, MSC collected from different tissues can form heterogeneous cellular populations and, therefore, manifest functional differences. Thus, the source of MSC should be a factor to be considered in the development of novel therapies. The following text presents an updated review of recent research outcomes related to Wharton's jelly mesenchymal stem/stromal cells (WJ-MSC), harvested from umbilical cords and considered novel and potential candidates for the development of cell-based approaches. This text highlights information on how WJ-MSC affect immune responses in comparison with other sources of MSC.

Stem cell therapies for wound healing

INTRODUCTION

Aberrant wound healing is a significant healthcare problem, posing a substantial burden on patients, their families, and the healthcare system. Existing treatment options remain only moderately effective and often fail to promote the closure of non-healing wounds in susceptible populations, such as aging and diabetic patients. Stem cell therapy has emerged as a promising treatment modality, with the potential to restore tissue to its pre-injured state. Of particular interest are mesenchymal stromal cells, which have been shown to accelerate wound healing by modulating the immune response and promoting angiogenesis.

AREAS COVERED

This review provides an overview of wound healing and current methods for the management of chronic wounds, as well as the current state and considerations for optimizing stem cell therapy. Considerations include stem cell types, tissue source, donor selection, cell heterogeneity, delivery methods, and genetic engineering.

EXPERT OPINION

A growing body of evidence has shown that delivery of stem cells, particularly mesenchymal stromal cells, has the potential to effectively improve the rate and quality of wound healing. However, significant additional basic and clinical research must be performed to optimize cell therapy, such as further elucidation of the therapeutic mechanisms of stem cells and standardization of clinical trial guidelines.

Advanced cell therapeutics are changing the clinical landscape: will mesenchymal stromal cells be a part of it?

During the past 15 years there have been dramatic changes in the medical landscape, particularly in oncology and regenerative medicine. Cell therapies have played a substantial part in this progress. Cellular immunotherapies can use immune cells, such as T cells or natural killer cells that, after functional modification ex vivo, exert powerful anti-cancer effects when given to the patient. Innovative technologies, such as re-programming terminally differentiated cells into pluripotent stem cells or into other cell types and applying specific enzymes to more precisely edit the human genome, are paving the way towards more potent cell and gene therapies.Mesenchymal stromal cells are promising cellular immunotherapeutics, which also have potential for use in tissue engineering strategies and other regenerative medicine applications. However, substantial gaps in our knowledge of their biology and therapeutic efficacy present major challenges to their sustainable implementation in the clinical routine.In this article, progress in the field of cell therapeutics during the past 15 years will be briefly discussed, with a focus on mesenchymal stromal cells, highlighting the impact of this field on patient care.