Aging bone marrow mesenchymal stromal cells have altered membrane glycerophospholipid composition and functionality

Lipid Priming of Adipose Mesenchymal Stromal Cells with Docosahexaenoic Acid: Impact on Cell Differentiation, Senescence and the Secretome Neuroregulatory Profile

BACKGROUND

Priming strategies that improve the functionality of MSCs may be required to address issues limiting successful clinical translation of MSC therapies. For conditions requiring high trophic support such as brain and spinal cord injuries, priming MSCs to produce higher levels of trophic factors may be instrumental to facilitate translation of current MSC therapies. We developed and tested a novel molecular priming paradigm using docosahexaenoic acid (DHA) to prime adipose tissue-derived mesenchymal stromal cells (ASCs) to enhance the secretome neuroregulatory potential.

METHODS

Comprehensive dose-response and time-course assays were carried to determine an optimal priming protocol. Secretome total protein measurements were taken in association with cell viability, density and morphometric assessments. Cell identity and differentiation capacity were studied by flow cytometry and lineage-specific markers. Cell growth was assessed by trypan-blue exclusion and senescence was probed over time using SA-β-gal, morphometry and gene expression. Secretomes were tested for their ability to support differentiation and neurite outgrowth of human neural progenitor cells (hNPCs). Neuroregulatory proteins in the secretome were identified using multiplex membrane arrays.

RESULTS

Priming with 40 µM DHA for 72 h significantly enhanced the biosynthetic capacity of ASCs, producing a secretome with higher protein levels and increased metabolic viability. DHA priming enhanced ASCs adipogenic differentiation and adapted their responses to replicative senescence induction. Furthermore, priming increased concentrations of neurotrophic factors in the secretome promoting neurite outgrowth and modulating the differentiation of hNPCs.

CONCLUSIONS

These results provide proof-of-concept evidence that DHA priming is a viable strategy to improve the neuroregulatory profile of ASCs.

Optimization of transplantation methods using isolated mesenchymal stem/stromal cells: clinical trials of inflammatory bowel diseases as an example

Mesenchymal stem/stromal cells (MSCs) are distributed in various tissues and are used in clinical applications as a source of transplanted cells because of their easy harvestability. Although MSCs express numerous cell-surface antigens, single-cell analyses have revealed a highly heterogeneous cell population depending on the original tissue and donor conditions, including age and interindividual differences. This heterogeneity leads to differences in their functions, such as multipotency and immunomodulatory effects, making it challenging to effectively treat targeted diseases. The therapeutic efficacy of MSCs is controversial and depends on the implantation site. Thus, there is no established recipe for the transplantation of MSCs (including the type of disease, type of origin, method of cell culture, form of transplanted cells, and site of delivery). Our recent preclinical study identified appropriate MSCs and their suitable transplantation routes in a mouse model of inflammatory bowel disease (IBD). Three-dimensional (3D) cultures of MSCs have been demonstrated to enhance their properties and sustain engraftment at the lesion site. In this note, we explore the methods of MSC transplantation for treating IBDs, especially Crohn's disease, from clinical trials published over the past decade. Given the functional changes in MSCs in 3D culture, we also investigate the clinical trials using 3D constructs of MSCs and explore suitable diseases that might benefit from this approach. Furthermore, we discuss the advantages of the prospective isolation of MSCs in terms of interindividual variability. This note highlights the need to define the method of MSC transplantation, including interindividual variability, the culture period, and the transplantation route.

Identification of potential biomarkers for aging diagnosis of mesenchymal stem cells derived from the aged donors

BACKGROUND

The clinical application of human bone-marrow derived mesenchymal stem cells (MSCs) for the treatment of refractory diseases has achieved remarkable results. However, there is a need for a systematic evaluation of the quality and safety of MSCs sourced from donors. In this study, we sought to assess one potential factor that might impact quality, namely the age of the donor.

METHODS

We downloaded two data sets from each of two Gene Expression Omnibus (GEO), GSE39035 and GSE97311 databases, namely samples form young (< 65 years of age) and old (> 65) donor groups. Through, bioinformatics analysis and experimental validation to these retrieved data, we found that MSCs derived from aged donors can lead to differential expression of gene profiles compared with those from young donors, and potentially affect the function of MSCs, and may even induce malignant tumors.

RESULTS

We identified a total of 337 differentially expressed genes (DEGs), including two upregulated and eight downregulated genes from the databases of both GSE39035 and GSE97311. We further identified 13 hub genes. Six of them, TBX15, IGF1, GATA2, PITX2, SNAI1 and VCAN, were highly expressed in many human malignancies in Human Protein Atlas database. In the MSCs in vitro senescent cell model, qPCR analysis validated that all six hub genes were highly expressed in senescent MSCs. Our findings confirm that aged donors of MSCs have a significant effect on gene expression profiles. The MSCs from old donors have the potential to cause a variety of malignancies. These TBX15, IGF1, GATA2, PITX2, SNAI1, VCAN genes could be used as potential biomarkers to diagnosis aging state of donor MSCs, and evaluate whether MSCs derived from an aged donor could be used for therapy in the clinic. Our findings provide a diagnostic basis for the clinical use of MSCs to treat a variety of diseases.

CONCLUSIONS

Therefore, our findings not only provide guidance for the safe and standardized use of MSCs in the clinic for the treatment of various diseases, but also provide insights into the use of cell regeneration approaches to reverse aging and support rejuvenation.

Hypoxia and interleukin-1-primed mesenchymal stem/stromal cells as novel therapy for stroke

Promising preclinical stroke research has not yielded meaningful and significant success in clinical trials. This lack of success has prompted the need for refinement of preclinical studies with the intent to optimize the chances of clinical success. Regenerative medicine, especially using mesenchymal stem/stromal cells (MSCs), has gained popularity in the last decade for treating many disorders, including central nervous system (CNS), such as stroke. In addition to less stringent ethical constraints, the ample availability of MSCs also makes them an attractive alternative to totipotent and other pluripotent stem cells. The ability of MSCs to differentiate into neurons and other brain parenchymal and immune cells makes them a promising therapy for stroke. However, these cells also have some drawbacks that, if not addressed, will render MSCs unfit for treating ischaemic stroke. In this review, we highlighted the molecular and cellular changes that occur following an ischaemic stroke (IS) incidence and discussed the physiological properties of MSCs suitable for tackling these changes. We also went further to discuss the major drawbacks of utilizing MSCs in IS and how adequate priming using both hypoxia and interleukin-1 can optimize the beneficial properties of MSCs while eliminating these drawbacks.

Stem Cells Derived from Human Exfoliated Deciduous Teeth Functional Assessment: Exploring the Changes of Free Fatty Acids Composition during Cultivation

The metabolic regulation of stemness is widely recognized as a crucial factor in determining the fate of stem cells. When transferred to a stimulating and nutrient-rich environment, mesenchymal stem cells (MSCs) undergo rapid proliferation, accompanied by a change in protein expression and a significant reconfiguration of central energy metabolism. This metabolic shift, from quiescence to metabolically active cells, can lead to an increase in the proportion of senescent cells and limit their regenerative potential. In this study, MSCs from human exfoliated deciduous teeth (SHEDs) were isolated and expanded in vitro for up to 10 passages. Immunophenotypic analysis, growth kinetics, in vitro plasticity, fatty acid content, and autophagic capacity were assessed throughout cultivation to evaluate the functional characteristics of SHEDs. Our findings revealed that SHEDs exhibit distinctive patterns of cell surface marker expression, possess high self-renewal capacity, and have a unique potential for neurogenic differentiation. Aged SHEDs exhibited lower proliferation rates, reduced potential for chondrogenic and osteogenic differentiation, an increasing capacity for adipogenic differentiation, and decreased autophagic potential. Prolonged cultivation of SHEDs resulted in changes in fatty acid composition, signaling a transition from anti-inflammatory to proinflammatory pathways. This underscores the intricate connection between metabolic regulation, stemness, and aging, crucial for optimizing therapeutic applications.

Consequences of Aging on Bone

With the aging of the global population, the incidence of musculoskeletal diseases has been increasing, seriously affecting people's health. As people age, the microenvironment within skeleton favors bone resorption and inhibits bone formation, accompanied by bone marrow fat accumulation and multiple cellular senescence. Specifically, skeletal stem/stromal cells (SSCs) during aging tend to undergo adipogenesis rather than osteogenesis. Meanwhile, osteoblasts, as well as osteocytes, showed increased apoptosis, decreased quantity, and multiple functional limitations including impaired mechanical sensing, intercellular modulation, and exosome secretion. Also, the bone resorption function of macrophage-lineage cells (including osteoclasts and preosteoclasts) was significantly enhanced, as well as impaired vascularization and innervation. In this study, we systematically reviewed the effect of aging on bone and the within microenvironment (including skeletal cells as well as their intracellular structure variations, vascular structures, innervation, marrow fat distribution, and lymphatic system) caused by aging, and mechanisms of osteoimmune regulation of the bone environment in the aging state, and the causal relationship with multiple musculoskeletal diseases in addition with their potential therapeutic strategy.

Lipid rafts mediate multilineage differentiation of human dental pulp-derived stem cells (DPSCs)

Cell outer membranes contain glycosphingolipids and protein receptors, which are integrated into glycoprotein domains, known as lipid rafts, which are involved in a variety of cellular processes, including receptor-mediated signal transduction and cellular differentiation process. In this study, we analyzed the lipidic composition of human Dental Pulp-Derived Stem Cells (DPSCs), and the role of lipid rafts during the multilineage differentiation process. The relative quantification of lipid metabolites in the organic fraction of DPSCs, performed by Nuclear Magnetic Resonance (NMR) spectroscopy, showed that mono-unsaturated fatty acids (MUFAs) were the most representative species in the total pool of acyl chains, compared to polyunsatured fatty acids (PUFAs). In addition, the stimulation of DPSCs with different culture media induces a multilineage differentiation process, determining changes in the gangliosides pattern. To understand the functional role of lipid rafts during multilineage differentiation, DPSCs were pretreated with a typical lipid raft affecting agent (MβCD). Subsequently, DPSCs were inducted to differentiate into osteoblast, chondroblast and adipoblast cells with specific media. We observed that raft-affecting agent MβCD prevented AKT activation and the expression of lineage-specific mRNA such as OSX, PPARγ2, and SOX9 during multilineage differentiation. Moreover, this compound significantly prevented the tri-lineage differentiation induced by specific stimuli, indicating that lipid raft integrity is essential for DPSCs differentiation. These results suggest that lipid rafts alteration may affect the signaling pathway activated, preventing multilineage differentiation.

Evaluation of Current Studies to Elucidate Processes in Dental Follicle Cells Driving Osteogenic Differentiation

When research on osteogenic differentiation in dental follicle cells (DFCs) began, projects focused on bone morphogenetic protein (BMP) signaling. The BMP pathway induces the transcription factor DLX3, whichh in turn induces the BMP signaling pathway via a positive feedback mechanism. However, this BMP2/DLX3 signaling pathway only seems to support the early phase of osteogenic differentiation, since simultaneous induction of BMP2 or DLX3 does not further promote differentiation. Recent data showed that inhibition of classical protein kinase C (PKCs) supports the mineralization of DFCs and that osteogenic differentiation is sensitive to changes in signaling pathways, such as protein kinase B (PKB), also known as AKT. Small changes in the lipidome seem to confirm the participation of AKT and PKC in osteogenic differentiation. In addition, metabolic processes, such as fatty acid biosynthesis, oxidative phosphorylation, or glycolysis, are essential for the osteogenic differentiation of DFCs. This review article attempts not only to bring the various factors into a coherent picture of osteogenic differentiation in DFCs, but also to relate them to recent developments in other types of osteogenic progenitor cells.

Lipids and the hallmarks of ageing: From pathology to interventions

Lipids are critical structural and functional architects of cellular homeostasis. Change in systemic lipid profile is a clinical indicator of underlying metabolic pathologies, and emerging evidence is now defining novel roles of lipids in modulating organismal ageing. Characteristic alterations in lipid metabolism correlate with age, and impaired systemic lipid profile can also accelerate the development of ageing phenotype. The present work provides a comprehensive review of the extent of lipids as regulators of the modern hallmarks of ageing viz., cellular senescence, chronic inflammation, gut dysbiosis, telomere attrition, genome instability, proteostasis and autophagy, epigenetic alterations, and stem cells dysfunctions. Current evidence on the modulation of each of these hallmarks has been discussed with emphasis on inherent age-dependent deficiencies in lipid metabolism as well as exogenous lipid changes. There appears to be sufficient evidence to consider impaired lipid metabolism as key driver of the ageing process although much of knowledge is yet fragmented. Considering dietary lipids, the type and quantity of lipids in the diet is a significant, but often overlooked determinant that governs the effects of lipids on ageing. Further research using integrative approaches amidst the known aging hallmarks is highly desirable for understanding the therapeutics of lipids associated with ageing.

Development of a Robust Consensus Modeling Approach for Identifying Cellular and Media Metabolites Predictive of Mesenchymal Stromal Cell Potency

Mesenchymal stromal cells (MSCs) have shown promise in regenerative medicine applications due in part to their ability to modulate immune cells. However, MSCs demonstrate significant functional heterogeneity in terms of their immunomodulatory function because of differences in MSC donor/tissue source, as well as non-standardized manufacturing approaches. As MSC metabolism plays a critical role in their ability to expand to therapeutic numbers ex vivo, we comprehensively profiled intracellular and extracellular metabolites throughout the expansion process to identify predictors of immunomodulatory function (T-cell modulation and indoleamine-2,3-dehydrogenase (IDO) activity). Here, we profiled media metabolites in a non-destructive manner through daily sampling and nuclear magnetic resonance (NMR), as well as MSC intracellular metabolites at the end of expansion using mass spectrometry (MS). Using a robust consensus machine learning approach, we were able to identify panels of metabolites predictive of MSC immunomodulatory function for 10 independent MSC lines. This approach consisted of identifying metabolites in 2 or more machine learning models and then building consensus models based on these consensus metabolite panels. Consensus intracellular metabolites with high predictive value included multiple lipid classes (such as phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins) while consensus media metabolites included proline, phenylalanine, and pyruvate. Pathway enrichment identified metabolic pathways significantly associated with MSC function such as sphingolipid signaling and metabolism, arginine and proline metabolism, and autophagy. Overall, this work establishes a generalizable framework for identifying consensus predictive metabolites that predict MSC function, as well as guiding future MSC manufacturing efforts through identification of high-potency MSC lines and metabolic engineering.

Metabolomic analysis of bone-derived exosomes in osteonecrosis of the femoral head based on UPLC-MS/MS

INTRODUCTION

Osteonecrosis of the femoral head (ONFH) is a disorder that causes a collapse of the femoral head, requiring subsequent total hip replacement. However, the pathogenesis of ONFH remains largely unclear. Herein, exosome metabolomics analyses were conducted to explore the pathophysiology of ONFH.

OBJECTIVES

This study aimed to conduct metabolic profiling of bone-derived exosomes of ONFH.

METHODS

30 ONFH patients and 30 femoral neck fracture (FNF) patients were included in this study. Exosomes were harvested from the femoral head by using ultracentrifugation. Ultraperformance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) was performed in combination with multivariate statistical analysis to reveal and provided new insight into identify the global metabolic profile of ONFH.

RESULTS

The results of transmission electron microscope (TEM), nanoparticle tracking analysis (NTA), and Western blots indicated that the microvesicles isolated from the femoral head were exosomes. Several compounds were identified, including lipids and lipid-like molecules, amino acids, peptides, organooxygen compounds. 44 differential metabolites were screened between ONFH and FNF patients. The up-and down-regulation of Riboflavin metabolism, Pantothenate and CoA biosynthesis, Glycerophospholipid metabolism, and Sphingolipid metabolism were associated with ONFH pathophysiology.

CONCLUSION

Our results suggest that metabolomics has huge prospects for elucidating pathophysiology of ONFH.

Characterization of mesenchymal stem cells in human fetal bone marrow by single-cell transcriptomic and functional analysis

Bone marrow mesenchymal stromal/stem cells (MSCs) are a heterogeneous population that can self-renew and generate stroma, cartilage, fat, and bone. Although a significant progress has been made toward recognizing about the phenotypic characteristics of MSCs, the true identity and properties of MSCs in bone marrow remain unclear. Here, we report the expression landscape of human fetal BM nucleated cells (BMNCs) based on the single-cell transcriptomic analysis. Unexpectedly, while the common cell surface markers such as CD146, CD271, and PDGFRa used for isolating MSCs were not detected, LIFR+PDGFRB+ were identified to be specific markers of MSCs as the early progenitors. In vivo transplantation demonstrated that LIFR+PDGFRB+CD45-CD31-CD235a- MSCs could form bone tissues and reconstitute the hematopoietic microenvironment (HME) effectively in vivo. Interestingly, we also identified a subpopulation of bone unipotent progenitor expressing TM4SF1+CD44+CD73+CD45-CD31-CD235a-, which had osteogenic potentials, but could not reconstitute HME. MSCs expressed a set of different transcription factors at the different stages of human fetal bone marrow, indicating that the stemness properties of MSCs might change during development. Moreover, transcriptional characteristics of cultured MSCs were significantly changed compared with freshly isolated primary MSCs. Our cellular profiling provides a general landscape of heterogeneity, development, hierarchy, microenvironment of the human fetal BM-derived stem cells at single-cell resolution.

Rejuvenation of Mesenchymal Stem Cells to Ameliorate Skeletal Aging

Advanced age is a shared risk factor for many chronic and debilitating skeletal diseases including osteoporosis and periodontitis. Mesenchymal stem cells develop various aging phenotypes including the onset of senescence, intrinsic loss of regenerative potential and exacerbation of inflammatory microenvironment via secretory factors. This review elaborates on the emerging concepts on the molecular and epigenetic mechanisms of MSC senescence, such as the accumulation of oxidative stress, DNA damage and mitochondrial dysfunction. Senescent MSCs aggravate local inflammation, disrupt bone remodeling and bone-fat balance, thereby contributing to the progression of age-related bone diseases. Various rejuvenation strategies to target senescent MSCs could present a promising paradigm to restore skeletal aging.

A passage-dependent network for estimating the in vitro senescence of mesenchymal stromal/stem cells using microarray, bulk and single cell RNA sequencing

Long-term in vitro culture of human mesenchymal stem cells (MSCs) leads to cell lifespan shortening and growth stagnation due to cell senescence. Here, using sequencing data generated in the public domain, we have established a specific regulatory network of "transcription factor (TF)-microRNA (miRNA)-Target" to provide key molecules for evaluating the passage-dependent replicative senescence of mesenchymal stem cells for the quality control and status evaluation of mesenchymal stem cells prepared by different procedures. Short time-series expression miner (STEM) analysis was performed on the RNA-seq and miRNA-seq databases of mesenchymal stem cells from various passages to reveal the dynamic passage-related changes of miRNAs and mRNAs. Potential miRNA targets were predicted using seven miRNA target prediction databases, including TargetScan, miRTarBase, miRDB, miRWalk, RNA22, RNAinter, and TargetMiner. Then use the TransmiR v2.0 database to obtain experimental-supported transcription factor for regulating the selected miRNA. More than ten sequencing data related to mesenchymal stem cells or mesenchymal stem cells reprogramming were used to validate key miRNAs and mRNAs. And gene set variation analysis (GSVA) was performed to calculate the passage-dependent signature. The results showed that during the passage of mesenchymal stem cells, a total of 29 miRNAs were gradually downregulated and 210 mRNA were gradually upregulated. Enrichment analysis showed that the 29 miRNAs acted as multipotent regulatory factors of stem cells and participated in a variety of signaling pathways, including TGF-beta, HIPPO and oxygen related pathways. 210 mRNAs were involved in cell senescence. According to the target prediction results, the targets of these key miRNAs and mRNAs intersect to form a regulatory network of "TF-miRNA-Target" related to replicative senescence of cultured mesenchymal stem cells, across 35 transcription factor, 7 miRNAs (has-mir-454-3p, has-mir-196b-5p, has-mir-130b-5p, has-mir-1271-5p, has-let-7i-5p, has-let-7a-5p, and has-let-7b-5p) and 7 predicted targets (PRUNE2, DIO2, CPA4, PRKAA2, DMD, DDAH1, and GATA6). This network was further validated by analyzing datasets from a variety of mesenchymal stem cells subculture and lineage reprogramming studies, as well as qPCR analysis of early passages mesenchymal stem cells versus mesenchymal stem cells with senescence morphologies (SA-β-Gal⁺). The "TF-miRNA-Target" regulatory network constructed in this study reveals the functional mechanism of miRNAs in promoting the senescence of MSCs during in vitro expansion and provides indicators for monitoring the quality of functional mesenchymal stem cells during the preparation and clinical application.

Improving Lentiviral Transduction of Human Adipose-Derived Mesenchymal Stem Cells

Lentiviral transduction of human mesenchymal stem cells (MSCs) induces long-term transgene expression and holds great promise for multiple gene therapy applications. Polybrene is the most commonly used reagent to improve viral gene transfer efficiency in laboratory research; however, it is not approved for human use and has also been shown to impair MSC proliferation and differentiation. Therefore, there is a need for optimized transduction protocols that can also be adapted to clinical settings. LentiBOOST (LB) and protamine sulfate are alternative transduction enhancers (TEs) that can be manufactured to current Good Manufacturing Practice standards, are easily applied to existing protocols, and have been previously studied for the transduction of human CD34+ hematopoietic stem cells. In this study, we investigated these reagents for the enhancement of lentiviral transduction of adipose-derived MSCs. We found that the combination of LB and protamine sulfate could yield comparable or even superior transduction efficiency to polybrene, with no dose-dependent adverse effects on cell viability or stem cell characteristics. This combination of TEs represents a valuable clinically compatible alternative to polybrene with the potential to significantly improve the efficiency of lentiviral transduction of MSCs for gene therapy applications.

An Intracellular Metabolic Signature as a Potential Donor-Independent Marker of the Osteogenic Differentiation of Adipose Tissue Mesenchymal Stem Cells

This paper describes an untargeted NMR metabolomics study to identify potential intracellular donor-dependent and donor-independent metabolic markers of proliferation and osteogenic differentiation of human adipose mesenchymal stem cells (hAMSCs). The hAMSCs of two donors with distinct proliferating/osteogenic characteristics were fully characterized regarding their polar endometabolome during proliferation and osteogenesis. An 18-metabolites signature (including changes in alanine, aspartate, proline, tyrosine, ATP, and ADP, among others) was suggested to be potentially descriptive of cell proliferation, independently of the donor. In addition, a set of 11 metabolites was proposed to compose a possible donor-independent signature of osteogenesis, mostly involving changes in taurine, glutathione, methylguanidine, adenosine, inosine, uridine, and creatine/phosphocreatine, choline/phosphocholine and ethanolamine/phosphocholine ratios. The proposed signatures were validated for a third donor, although they require further validation in a larger donor cohort. We believe that this proof of concept paves the way to exploit metabolic markers to monitor (and potentially predict) cell proliferation and the osteogenic ability of different donors.

Fatty Acid Fingerprints and Hyaluronic Acid in Extracellular Vesicles from Proliferating Human Fibroblast-like Synoviocytes

Extracellular vesicles (EVs) function as conveyors of fatty acids (FAs) and other bioactive lipids and can modulate the gene expression and behavior of target cells. EV lipid composition influences the fluidity and stability of EV membranes and reflects the availability of lipid mediator precursors. Fibroblast-like synoviocytes (FLSs) secrete EVs that transport hyaluronic acid (HA). FLSs play a central role in inflammation, pannus formation, and cartilage degradation in joint diseases, and EVs have recently emerged as potential mediators of these effects. The aim of the present study was to follow temporal changes in HA and EV secretion by normal FLSs, and to characterize the FA profiles of FLSs and EVs during proliferation. The methods used included nanoparticle tracking analysis, confocal laser scanning microscopy, sandwich-type enzyme-linked sorbent assay, quantitative PCR, and gas chromatography. The expression of hyaluronan synthases 1-3 in FLSs and HA concentrations in conditioned media decreased during cell proliferation. This was associated with elevated proportions of 20:4n-6 and total n-6 polyunsaturated FAs (PUFAs) in high-density cells, reductions in n-3/n-6 PUFA ratios, and up-regulation of cluster of differentiation 44, tumor necrosis factor α, peroxisome proliferator-activated receptor (PPAR)-α, and PPAR-γ. Compared to the parent FLSs, 16:0, 18:0, and 18:1n-9 were enriched in the EV fraction. EV counts decreased during cell growth, and 18:2n-6 in EVs correlated with the cell count. To conclude, FLS proliferation was featured by increased 20:4n-6 proportions and reduced n-3/n-6 PUFA ratios, and FAs with a low degree of unsaturation were selectively transferred from FLSs into EVs. These FA modifications have the potential to affect membrane fluidity, biosynthesis of lipid mediators, and inflammatory processes in joints, and could eventually provide tools for translational studies to counteract cartilage degradation in inflammatory joint diseases.

Endo- and Exometabolome Crosstalk in Mesenchymal Stem Cells Undergoing Osteogenic Differentiation

This paper describes, for the first time to our knowledge, a lipidome and exometabolome characterization of osteogenic differentiation for human adipose tissue stem cells (hAMSCs) using nuclear magnetic resonance (NMR) spectroscopy. The holistic nature of NMR enabled the time-course evolution of cholesterol, mono- and polyunsaturated fatty acids (including ω-6 and ω-3 fatty acids), several phospholipids (phosphatidylcholine, phosphatidylethanolamine, sphingomyelins, and plasmalogens), and mono- and triglycerides to be followed. Lipid changes occurred almost exclusively between days 1 and 7, followed by a tendency for lipidome stabilization after day 7. On average, phospholipids and longer and more unsaturated fatty acids increased up to day 7, probably related to plasma membrane fluidity. Articulation of lipidome changes with previously reported polar endometabolome profiling and with exometabolome changes reported here in the same cells, enabled important correlations to be established during hAMSC osteogenic differentiation. Our results supported hypotheses related to the dynamics of membrane remodelling, anti-oxidative mechanisms, protein synthesis, and energy metabolism. Importantly, the observation of specific up-taken or excreted metabolites paves the way for the identification of potential osteoinductive metabolites useful for optimized osteogenic protocols.

Discovery of Potential Biomarkers for Postmenopausal Osteoporosis Based on Untargeted GC/LC-MS

PURPOSE

As an important public health problem, osteoporosis (OP) in China is also in an upward trend year by year. As a standard method for diagnosing OP, dual-energy X-ray absorptiometry (DXA) cannot analyze the pathological process but only see the results. It is difficult to evaluate the early diagnosis of OP. Our study was carried out through a serum metabolomic study of OP in Chinese postmenopausal women on untargeted gas chromatography (GC)/liquid chromatography (LC)-mass spectrometry (MS) to find possible diagnostic markers.

MATERIALS AND METHODS

50 Chinese postmenopausal women with osteoporosis and 50 age-matched women were selected as normal controls. We first used untargeted GC/LC-MS to analyze the serum of these participants and then combined it with a large number of multivariate statistical analyses to analyze the data. Finally, based on a multidimensional analysis of the metabolites, the most critical metabolites were considered to be biomarkers of OP in postmenopausal women. Further, biomarkers identified relevant metabolic pathways, followed by a map of metabolic pathways found in the database.

RESULTS

We found that there may be metabolic pathway disorders like glucose metabolism, lipid metabolism, and amino acid metabolism in postmenopausal women with OP. 18 differential metabolites are considered to be potential biomarkers of OP in postmenopausal women which are a major factor in metabolism and bone physiological function.

CONCLUSION

These findings can be applied to clinical work through further validation studies. It also shows that metabonomic analysis has great potential in the application of early diagnosis and recurrence monitoring in postmenopausal OP women.

Application of metabolomics in osteoporosis research

Osteoporosis (OP) is a systemic disease characterized by bone metabolism imbalance and bone microstructure destruction, which causes serious social and economic burden. At present, the diagnosis and treatment of OP mainly rely on imaging combined with drugs. However, the existing pathogenic mechanisms, diagnosis and treatment strategies for OP are not clear and effective enough, and the disease progression that cannot reflect OP further restricts its effective treatment. The application of metabolomics has facilitated the study of OP, further exploring the mechanism and behavior of bone cells, prevention, and treatment of the disease from various metabolic perspectives, finally realizing the possibility of a holistic approach. In this review, we focus on the application of metabolomics in OP research, especially the newer systematic application of metabolomics and treatment with herbal medicine and their extracts. In addition, the prospects of clinical transformation in related fields are also discussed. The aim of this study is to highlight the use of metabolomics in OP research, especially in exploring the pathogenesis of OP and the therapeutic mechanisms of natural herbal medicine, for the benefit of interdisciplinary researchers including clinicians, biologists, and materials engineers.

Phospholipid Profiles for Phenotypic Characterization of Adipose-Derived Multipotent Mesenchymal Stromal Cells

Multipotent mesenchymal stromal cells (MSC) have emerged as therapeutic tools for a wide range of pathological conditions. Yet, the still existing deficits regarding MSC phenotype characterization and the resulting heterogeneity of MSC used in different preclinical and clinical studies hamper the translational success. In search for novel MSC characterization approaches to complement the traditional trilineage differentiation and immunophenotyping assays reliably across species and culture conditions, this study explored the applicability of lipid phenotyping for MSC characterization and discrimination. Human peripheral blood mononuclear cells (PBMC), human fibroblasts, and human and equine adipose-derived MSC were used to compare different mesodermal cell types and MSC from different species. For MSC, cells cultured in different conditions, including medium supplementation with either fetal bovine serum or platelet lysate as well as culture on collagen-coated dishes, were additionally investigated. After cell harvest, lipids were extracted by chloroform/methanol according to Bligh and Dyer. The lipid profiles were analysed by an untargeted approach using liquid chromatography coupled to mass spectrometry (LC-MS) with a reversed phase column and an ion trap mass spectrometer. In all samples, phospholipids and sphingomyelins were found, while other lipids were not detected with the current approach. The phospholipids included different species of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylserine (PS) in all cell types, whereas phosphatidylglycerol (PG) species were only present in MSC. MSC from both species showed a higher phospholipid species diversity than PBMC and fibroblasts. Few differences were found between MSC from different culture conditions, except that human MSC cultured with platelet lysate exhibited a unique phenotype in that they exclusively featured PE O-40:4, PG 38:6 and PG 40:6. In search for specific and inclusive candidate MSC lipid markers, we identified PE O-36:3 and PG 40:7 as potentially suitable markers across culture conditions, at which PE O-36:3 might even be used across species. On that basis, phospholipid phenotyping is a highly promising approach for MSC characterization, which might condone some heterogeneity within the MSC while still achieving a clear discrimination even from fibroblasts. Particularly the presence or absence of PG might emerge as a decisive criterion for future MSC characterization.

Functional changes in decidual mesenchymal stem/stromal cells are associated with spontaneous onset of labour

Ageing and parturition share common pathways, but their relationship remains poorly understood. Decidual cells undergo ageing as parturition approaches term, and these age-related changes may trigger labour. Mesenchymal stem/stromal cells (MSCs) are the predominant stem cell type in the decidua. Stem cell exhaustion is a hallmark of ageing, and thus ageing of decidual MSCs (DMSCs) may contribute to the functional changes in decidual tissue required for term spontaneous labour. Here, we determine whether DMSCs from patients undergoing spontaneous onset of labour (SOL-DMSCs) show evidence of ageing-related functional changes compared with those from patients not in labour (NIL-DMSCs), undergoing Caesarean section. Placentae were collected from term (37-40 weeks of gestation), SOL (n = 18) and NIL (n = 17) healthy patients. DMSCs were isolated from the decidua basalis that remained attached to the placenta after delivery. DMSCs displayed stem cell-like properties and were of maternal origin. Important cell properties and lipid profiles were assessed and compared between SOL- and NIL-DMSCs. SOL-DMSCs showed reduced proliferation and increased lipid peroxidation, migration, necrosis, mitochondrial apoptosis, IL-6 production and p38 MAPK levels compared with NIL-DMSCs (P < 0.05). SOL- and NIL-DMSCs also showed significant differences in lipid profiles in various phospholipids (phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylserine), sphingolipids (ceramide, sphingomyelin), triglycerides and acyl carnitine (P < 0.05). Overall, SOL-DMSCs had altered lipid profiles compared with NIL-DMSCs. In conclusion, SOL-DMSCs showed evidence of ageing-related reduced functionality, accumulation of cellular damage and changes in lipid profiles compared with NIL-DMSCs. These changes may be associated with term spontaneous labour.

Icariin protects against cage layer osteoporosis by intervening in steroid biosynthesis and glycerophospholipid metabolism

Cage layer osteoporosis (CLO) is a common bone metabolism disease in the breeding industry of China. However, effective prevention for CLO has not been developed. Icariin (ICA), the main bioactive component of the Chinese herb Epimedium, has been shown to have good therapeutic effects on bone-related diseases. In this study, the effects of ICA were further evaluated in a low-calcium diet-induced CLO, and a serum metabolomics assay was performed to understand the underlying mechanisms. A total of 144 31-wk-old Lohmann pink-shell laying hens were randomly allocated to 4 groups with 6 replicates of 6 hens per replicate. The 4 dietary treatment groups consisted of a basal diet (3.5% calcium), a low-calcium diet (2.0% calcium), and a low-calcium diet supplemented with 0.5 or 2.0 g/kg ICA. The results showed that ICA exerted good osteoprotective effects on low-calcium diet-induced CLO. ICA significantly increased femur bone mineral density, improved bone microstructure, decreased bone metabolic level, and upregulated mRNA expression of bone formation genes in femoral bone tissue. Serum untargeted metabolomics analysis showed that 8 metabolite levels were significantly changed after ICA treatment, including increased contents of 7-dehydrocholesterol, 7-oxocholesterol, desmosterol, PC (18:1(9Z)/18:1(9Z)), PS (18:0/18:1(9Z)), N,N-dimethylaniline and 2-hydroxy-butanoic acid and decreased N2,N2-dimethylguanosine. Metabolic pathway analysis based on the above 8 metabolites indicated that ICA mainly perturbed steroid biosynthesis and glycerophospholipid metabolism. These findings suggest that ICA can effectively prevent bone loss in low-calcium diet-induced CLO by mediating steroid biosynthesis and glycerophospholipid metabolism and provide new information for the regulation of bone metabolic diseases.

Towards Physiologic Culture Approaches to Improve Standard Cultivation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are of great interest for their use in cell-based therapies due to their multipotent differentiation and immunomodulatory capacities. In consequence of limited numbers following their isolation from the donor tissue, MSCs require extensive expansion performed in traditional 2D cell culture setups to reach adequate amounts for therapeutic use. However, prolonged culture of MSCs in vitro has been shown to decrease their differentiation potential and alter their immunomodulatory properties. For that reason, preservation of these physiological characteristics of MSCs throughout their in vitro culture is essential for improving the efficiency of therapeutic and in vitro modeling applications. With this objective in mind, many studies already investigated certain parameters for enhancing current standard MSC culture protocols with regard to the effects of specific culture media components or culture conditions. Although there is a lot of diversity in the final therapeutic uses of the cells, the primary stage of standard isolation and expansion is imperative. Therefore, we want to review on approaches for optimizing standard MSC culture protocols during this essential primary step of in vitro expansion. The reviewed studies investigate and suggest improvements focused on culture media components (amino acids, ascorbic acid, glucose level, growth factors, lipids, platelet lysate, trace elements, serum, and xenogeneic components) as well as culture conditions and processes (hypoxia, cell seeding, and dissociation during passaging), in order to preserve the MSC phenotype and functionality during the primary phase of in vitro culture.

Bioactive Lipids in MSCs Biology: State of the Art and Role in Inflammation

Lipidomics is a lipid-targeted metabolomics approach that aims to the comprehensive analysis of lipids in biological systems in order to highlight the specific functions of lipid species in health and disease. Lipids play pivotal roles as they are major structural components of the cellular membranes and energy storage molecules but also, as most recently shown, they act as functional and regulatory components of intra- and intercellular signaling. Herein, emphasis is given to the recently highlighted roles of specific bioactive lipids species, as polyunsaturated fatty acids (PUFA)-derived mediators (generally known as eicosanoids), endocannabinoids (eCBs), and lysophospholipids (LPLs), and their involvement in the mesenchymal stem cells (MSCs)-related inflammatory scenario. Indeed, MSCs are a heterogenous population of multipotent cells that have attracted much attention for their potential in regulating inflammation, immunomodulatory capabilities, and reparative roles. The lipidomics of the inflammatory disease osteoarthritis (OA) and the influence of MSCs-derived lipids have also been addressed.

Aging-Affected MSC Functions and Severity of Periodontal Tissue Destruction in a Ligature-Induced Mouse Periodontitis Model

Mesenchymal stem cells (MSCs) are known to play important roles in the repair of lost or damaged tissues and immunotolerance. On the other hand, aging is known to impair MSC function. However, little is currently known about how aged MSCs affect the host response to the local inflammatory condition and tissue deterioration in periodontitis, which is a progressive destructive disease of the periodontal tissue potentially leading to multiple tooth loss. In this study, we examined the relationship between aging-induced impairment of MSC function and the severity of periodontal tissue destruction associated with the decrease in host immunomodulatory response using a ligature-induced periodontitis model in young and aged mice. The results of micro computerized tomography (micro-CT) and histological analysis revealed a more severe bone loss associated with increased osteoclast activity in aged (50-week-old) mice compared to young (5-week-old) mice. Immunostaining analysis revealed that, in aged mice, the accumulation of inflammatory T and B cells was higher, whereas the percentage of platelet-derived growth factor receptor α (PDGFRα)⁺ MSCs, which are known to modulate the apoptosis of T cells, was significantly lower than in young mice. In vitro analysis of MSC function showed that the expression of surface antigen markers for MSCs (Sca-1, CD90, CD146), colony formation, migration, and osteogenic differentiation of aged MSCs were significantly declined compared to those of young MSCs. Moreover, a significantly higher proportion of aged MSCs were positive for the senescence-associated β galactosidase activity. Importantly, aged MSCs presented a decreased expression of FAS-L, which was associated with a lower immunomodulatory property of aged MSCs to induce T cell apoptosis in co-cultures compared with young MSCs. In summary, this is the first study showing that aging-induced impairment of MSC function, including immunomodulatory response, is potentially correlated with progressive periodontal tissue deterioration.

Lipidomics of mesenchymal stem cell differentiation

Mesenchymal stem cells (MSCs), such as adipose-derived stem cells (ADSCs) and skeletal muscle-derived stem cells (MDSCs), are potential sources for cell-based therapeutic strategies. However, there is little knowledge about the lipid composition of these stem cells and the mechanisms of their differentiation. Lipids have important biological and physiological functions that are critical for understanding the regulation and control of stem cell fate. This study sought to analyze the lipidome of rabbit ADSCs and MDSCs and their adipogenic and osteogenic differentiation. The MSCs were isolated and were characterized by flow cytometry. Lipids were extracted from both MSCs and differentiated cells, and the lipids were subsequently analyzed with a hybrid triple quadrupole time-of-flight mass spectrometer. The results showed a total of 1687 lipid species. MSCs exhibited different lipid profiles as well as changes in lipid composition after differentiation. Furthermore, the expression levels of N-acyl-phosphatidylethanolamine (NAPE) 54:7+NH4 (-FA 17:0(NH4)) and phosphatidylcholine (PC) 42:6+Na were higher in the adipogenic lineages in of both MSC types, and NAPE 58:2+NH4 (-FA 17:0 (NH4)) and NAPE 56:2+NH4 (-FA 17:0 (NH4)) had higher levels in the osteogenic lineages, suggesting lipid similarities in cells differentiated from different stem cell sources.

Effects of Lipids and Lipoproteins on Mesenchymal Stem Cells Used in Cardiac Tissue Regeneration

Mesenchymal stem cells (MSCs) have two characteristics of interest for this paper: the ability to self-renew, and the potential for multiple-lineage differentiation into various cells. MSCs have been used in cardiac tissue regeneration for over a decade. Adult cardiac tissue regeneration ability is quite low; it cannot repair itself after injury, as the heart cells are replaced by fibroblasts and lose function. It is therefore important to search for a feasible way to repair and restore heart function through stem cell therapy. Stem cells can differentiate and provide a source of progenitor cells for cardiomyocytes, endothelial cells, and supporting cells. Studies have shown that the concentrations of blood lipids and lipoproteins affect cardiovascular diseases, such as atherosclerosis, hypertension, and obesity. Furthermore, the MSC lipid profiles, such as the triglyceride and cholesterol content, have been revealed by lipidomics, as well as their correlation with MSC differentiation. Abnormal blood lipids can cause serious damage to internal organs, especially heart tissue. In the past decade, the accumulated literature has indicated that lipids/lipoproteins affect stem cell behavior and biological functions, including their multiple lineage capability, and in turn affect the outcome of regenerative medicine. This review will focus on the effect of lipids/lipoproteins on MSC cardiac regenerative medicine, as well as the effect of lipid-lowering drugs in promoting cardiomyogenesis-associated MSC differentiation.

Orotic acid-treated hepatocellular carcinoma cells resist steatosis by modification of fatty acid metabolism

BACKGROUND

Orotic acid (OA) has been intensively utilized to induce fatty liver in rats. Although the capacity of OA to cause steatosis is species-specific, previous in vitro studies indicate that humans could also be susceptible to OA-induced fatty liver. The aim of the present study was to re-elucidate the potential of OA exposure to modulate the cellular mechanisms involved in both non-alcoholic fatty liver disease pathogenesis and cellular protection from lipid accumulation. In addition, alterations in detailed fatty acid (FA) profiles of cells and culture media were analyzed to assess the significance of lipid metabolism in these phenomena.

METHODS

In our experiments, human hepatocellular carcinoma HepG2 cells were exposed to OA. Bacterial endotoxin, lipopolysaccharide (LPS), was used to mimic hepatic inflammation. The lipogenic and inflammatory effects of OA and/or LPS on cells were assessed by labeling cellular lipids with Nile red stain and by performing image quantifications. The expression levels of key enzymes involved in de novo lipogenesis (DNL) and of inflammatory markers related to the disease development were studied by qRT-PCR. FA profiles of cells and culture media were determined from total lipids with gas chromatography-mass spectrometry.

RESULTS

Our data indicate that although OA possibly promotes the first stage of DNL, it does not cause a definite lipogenic transformation in HepG2 cells. Reduced proportions of 16:0, increased stearoyl-Coenzyme A desaturase 1 mRNA expression and relatively high proportions of 16:1n-7 suggest that active delta9-desaturation may limit lipogenesis and the accumulation of toxic 16:0. Inflammatory signaling could be reduced by the increased production of long-chain n-3 polyunsaturated FA (PUFA) and the active incorporation of certain FA, including 18:1n-9, into cells. In addition, increased proportions of 20:4n-6 and 22:6n-3, total PUFA and dimethyl acetal 18:0 suggest that OA exposure may cause increased secretion of lipoproteins and extracellular vesicles.

CONCLUSIONS

The present data suggest that, apart from the transcription-level events reported by previous studies, modifications of FA metabolism may also be involved in the prevention of OA-mediated steatosis. Increased delta9-desaturation and secretion of lipoproteins and extracellular vesicles could offer potential mechanisms for further studies to unravel how OA-treated cells alleviate lipidosis.

Lipid Mediated Regulation of Adult Stem Cell Behavior

Adult stem cells constitute an important reservoir of self-renewing progenitor cells and are crucial for maintaining tissue and organ homeostasis. The capacity of stem cells to self-renew or differentiate can be attributed to distinct metabolic states, and it is now becoming apparent that metabolism plays instructive roles in stem cell fate decisions. Lipids are an extremely vast class of biomolecules, with essential roles in energy homeostasis, membrane structure and signaling. Imbalances in lipid homeostasis can result in lipotoxicity, cell death and diseases, such as cardiovascular disease, insulin resistance and diabetes, autoimmune disorders and cancer. Therefore, understanding how lipid metabolism affects stem cell behavior offers promising perspectives for the development of novel approaches to control stem cell behavior either in vitro or in patients, by modulating lipid metabolic pathways pharmacologically or through diet. In this review, we will first address how recent progress in lipidomics has created new opportunities to uncover stem-cell specific lipidomes. In addition, genetic and/or pharmacological modulation of lipid metabolism have shown the involvement of specific pathways, such as fatty acid oxidation (FAO), in regulating adult stem cell behavior. We will describe and compare findings obtained in multiple stem cell models in order to provide an assessment on whether unique lipid metabolic pathways may commonly regulate stem cell behavior. We will then review characterized and potential molecular mechanisms through which lipids can affect stem cell-specific properties, including self-renewal, differentiation potential or interaction with the niche. Finally, we aim to summarize the current knowledge of how alterations in lipid homeostasis that occur as a consequence of changes in diet, aging or disease can impact stem cells and, consequently, tissue homeostasis and repair.

Molecular Mechanisms Contributing to Mesenchymal Stromal Cell Aging

Mesenchymal stem/stromal cells (MSCs) are a reservoir for tissue homeostasis and repair that age during organismal aging. Beside the fundamental in vivo role of MSCs, they have also emerged in the last years as extremely promising therapeutic agents for a wide variety of clinical conditions. MSC use frequently requires in vitro expansion, thus exposing cells to replicative senescence. Aging of MSCs (both in vivo and in vitro) can affect not only their replicative potential, but also their properties, like immunomodulation and secretory profile, thus possibly compromising their therapeutic effect. It is therefore of critical importance to unveil the underlying mechanisms of MSC senescence and to define shared methods to assess MSC aging status. The present review will focus on current scientific knowledge about MSC aging mechanisms, control and effects, including possible anti-aging treatments.

The Analysis of In Vivo Aging in Human Bone Marrow Mesenchymal Stromal Cells Using Colony-Forming Unit-Fibroblast Assay and the CD45lowCD271+ Phenotype

Uncultured mesenchymal stromal cells (MSCs) are increasingly used in therapies; however, the effects of donor age on their biological characteristics and gene expression remain unclear. The aim of this study was to investigate age-related changes in bone marrow (BM) MSCs following minimal or no culture manipulation. Iliac crest BM was aspirated from 67 healthy donors (19-89 years old) and directly used for the colony-forming unit-fibroblast (CFU-F) assay or CD45^lowCD271⁺ cell enumeration. The colonies were analysed for colony area and integrated density (ID) when grown in standard MSC media or media supplemented with human serum from young (YS) or old (OS) donors. There was a notable age-related decline in the number of MSCs per millilitre of BM aspirate revealed by the CFU-F assay (r = −0.527, p < 0.0001) or flow cytometry (r = −0.307, p = 0.0116). Compared to young donors (19-40 years old), colony IDs were significantly lower in older donors (61-89 years old), particularly for smaller-sized colonies (42% lower, p < 0.01). When cultured in media supplemented with OS, young and old donor MSCs formed colonies with lower IDs, by 21%, p < 0.0001, and 27%, p < 0.05, respectively, indicating the formation of smaller sparser colonies. No significant differences in the expression of selected adipogenic, osteogenic, stromal, and bone remodelling genes as well as CD295, CD146, CD106, and connexin 43 surface molecules were found in sorted CD45^lowCD271⁺ MSCs from young and old donors (n = 8 donors each). Altogether, these results show similar trends for age-related decline in BM MSC numbers measured by the CFU-F assay and flow cytometry and reveal age-related effects of human serum on MSC colony formation. No significant differences in selected gene expression in uncultured CD45^lowCD271⁺ MSCs suggest that old donor MSCs may not be inferior in regard to their multipotential functions. Due to large donor-to-donor variation in all donor groups, our data indicate that an individual's chronological age is not a reliable predictor of their MSC number or potency.

Lipidomics characterization of the alterations of Trichoderma brevicompactum membrane glycerophospholipids during the fermentation phase

The biological membrane lipid composition has been demonstrated to greatly influence the secretion of secondary metabolites. This study was conducted to investigate the periodical alterations of whole cellular lipids and their associations with secondary products in Trichoderma brevicompactum. An electrospray ionization–mass spectrometry-based lipidomics strategy was used to acquire the metabolic profiles of membrane lipids during fermentation. Univariate analyses showed that most fungi glycerophospholipids were significantly altered at the early phase compared with the late phase. In addition, correlation analyses showed high correlations between phosphatidylcholine alterations and fermentation duration. In addition, the fermentation-associated alterations of phosphatidylcholines were found to be in accordance with the degrees of unsaturation of acyl-chains. Harzianum A reached a maximum on the 12th day, while trichodermin and 6-pentyl-2H-pyran-2-one showed the highest abundances on the 9th day, both of which were inclined to correlate with the alterations of phosphatidylcholines and phosphatidylethanolamines, respectively. These findings demonstrated that the alterations of the membrane lipid species in Trichoderma spp. were associated with the fermentation phases and might influence the secretion of specific secondary products, which may be useful in studying the optimization of secondary products in Trichoderma spp.

The Pros and Cons of Mesenchymal Stem Cell-Based Therapies

The need to search for new, alternative treatments for various diseases has prompted scientists and physicians to focus their attention on regenerative medicine and broadly understood cell therapies. Currently, stem cells are being investigated for their potentially widespread use in therapies for many untreatable diseases. Nowadays modern treatment strategies willingly use mesenchymal stem cells (MSCs) derived from different sources. Researchers are increasingly aware of the nature of MSCs and new possibilities for their use. Due to their properties, especially their ability to self-regenerate, differentiate into several cell lineages and participate in immunomodulation, MSCs have become a promising tool in developing modern and efficient future treatment strategies. The great potential and availability of MSCs allow for their various clinical applications in the treatment of many incurable diseases. In addition to their many advantages and benefits, there are still questions about the use of MSCs. What are the mechanisms of action of MSCs? How do they reach their destination? Is the clinical use of MSCs safe? These are the main questions that arise regarding MSCs when they are considered as therapeutic tools. The diversity of MSCs, their different clinical applications, and their many traits that have not yet been thoroughly investigated are sources of discussions and controversial opinions about these cells. Here, we reviewed the current knowledge about MSCs in terms of their therapeutic potential, clinical effects and safety in clinical applications.

Integrated Lipidomics and Transcriptomics Characterization upon Aging-Related Changes of Lipid Species and Pathways in Human Bone Marrow Mesenchymal Stem Cells

Aberrant differentiations of bone mesenchymal stem cells (BMSCs) have proved to be associated with the occurrence of senile osteoporosis. However, mechanisms of this phenomenon relative to abnormal lipid metabolism remain unclear. This study was conducted to characterize the lipidomics alterations during BMSC passaging, aiming at uncovering the aging-related lipid metabolism that may play an important role in aberrant differentiations of BMSCs. Principal component analysis presented the sequential lipidomics alterations during BMSC passaging. The majority of glycerophospholipids, including phosphatidylcholines, phosphatidylethanolamines, phosphatidylglycerols, as well as sphingolipids, revealed significant elevations, whereas the others, including phosphatidic acids, phosphatidylinositols, and phosphatidylserines, presented decreases in aged cells. Double-bond equivalent versus carbon number plots demonstrated that the changing trends and significances of lipids during passaging were associated with the chain length and the degree of unsaturation. In the correlation networks, the scattering patterns of lipid categories suggested the category-related metabolic independence and potential conversion among phosphatidic acids, phosphatidylinositols, and phosphatidylserines. The lipid-enzyme integrated pathway analysis indicated the activated metabolic conversion from phosphatidic acids to CDP-diacylglycerol to phosphatidylinositols and from sphingosine to ceramides to sphingomyelins with BMSC passaging. The conversions among lipid species described the lipidomics responses that potentially induced the aberrant differentiations during BMSC aging.

Global urinary metabolic profiling of the osteonecrosis of the femoral head based on UPLC-QTOF/MS

INTRODUCTION

Osteonecrosis of the femoral head (ONFH), one of the widespread orthopedic diseases with a decrease in bloodstream to the femoral head, is frequently accompanied by cellular death, trabecula fracture, and collapse of the articular surface. The exactly pathological mechanism of ONFH remains to explore and further identify.

OBJECTIVES

The aim was to identify the global urinary metabolic profiling of ONFH and to detect biomarkers of ONFH.

METHODS

Urine samples were collected from 26 ONFH patients and 26 healthy people. Ultra-performance liquid chromatography-quadrupole time of flight tandem mass spectrometry (UPLC-QTOF/MS) in combination with multivariate statistical analysis was developed and performed to identify the global urinary metabolic profiling of ONFH.

RESULTS

The urinary metabolic profiling of ONFH group was significantly separated from the control group by multivariate statistical analysis. 33 distinctly differential metabolites were detected between the ONFH patients and healthy people. Sulfate, urea, Deoxycholic acid and PE(14:0/14:1(9Z)) were screened as the potential biomarkers of ONFH. In addition, the up/down-regulation of sulfur metabolism, cysteine and methionine metabolism, glycerophospholipid metabolism, and histidine metabolism were clearly be associated with the ONFH pathogenic progress.

CONCLUSION

Our results suggested that metabolomics could serve as a promising approach for identifying the diagnostic biomarkers and elucidating the pathological mechanism of ONFH.

Mesenchymal stromal cells from infants with simple polydactyly modulate immune responses more efficiently than adult mesenchymal stromal cells

Bone marrow-derived stromal cells or mesenchymal stromal cells (BMSCs or MSCs, as we will call them in this work) are multipotent progenitor cells that can differentiate into osteoblasts, adipocytes and chondrocytes. In addition, MSCs have been shown to modulate the function of a variety of immune cells. Donor age has been shown to affect the regenerative potential, differentiation, proliferation and anti-inflammatory potency of MSCs; however, the impact of donor age on their immunosuppressive activity is unknown. In this study, we evaluated the ability of MSCs derived from very young children and adults on T-cell suppression and cytokine secretion by monocytes/macrophages. MSCs were obtained from extra digits of children between 10 and 21 months and adults between 28 and 64 years of age. We studied cell surface marker expression, doubling time, lineage differentiation potential and immunosuppressive function of the MSCs. Young MSCs double more quickly and differentiate into bone and fat cells more efficiently than those from older donors. They also form more and dense colonies of fibroblasts (colony forming unit-fibroblast [CFU-F]). MSCs from both young and adult subjects suppressed T-cell proliferation in a mitogen-induced assay at 1:3 and 1:30 ratios. At a 1:30 ratio, however, MSCs from adults did not, but MSCs from infants did suppress T-cell proliferation. In the mixed lymphocyte reaction assay, MSCs from infants produced similar levels of suppression at all three MSC/T-cell ratios, but adult MSCs only inhibited T-cell proliferation at a 1:3 ratio. Cytokine analyses of co-cultures of MSCs and macrophages showed that both adult and young MSCs suppress tumor necrosis factor alpha (TNF-α) and induce interleukin-10 (IL-10) production in macrophage co-culture assay in a similar manner. Overall, this work shows that developing MSCs display a higher level of immunosuppression than mature MSCs.

Association of Plasma Lipids and Polar Metabolites with Low Bone Mineral Density in Singaporean-Chinese Menopausal Women: A Pilot Study

The diagnosis of osteoporosis is mainly based on clinical examination and bone mineral density assessments. The present pilot study compares the plasma lipid and polar metabolite profiles in blood plasma of 95 Singaporean-Chinese (SC) menopausal women with normal and low bone mineral density (BMD) using an untargeted metabolomic approach. The primary finding of this study was the association between lipids and femoral neck BMD in SC menopausal women. Twelve lipids were identified to be associated with low BMD by the orthogonal partial least squares (OPLS) model. Plasma concentrations of eight glycerophospholipid, glycerolipid, and sphingolipid species were significantly lower in menopausal women with low BMD but higher in two glycerophospholipid species (phosphatidylinositol and phosphatidic acid). Further, this study found no significant differences in plasma amino acid metabolites. However, trends for lower 4-aminobutyric acid, turanose, proline, aminopropionitrile, threonine, and methionine were found in women with low BMD. This pilot study identified associations between lipid metabolism and femoral neck BMD in SC women. Further studies are required on larger populations for evaluating the bone health effect of these compounds and their usefulness as clinical biomarkers for osteoporosis prediction in women.

Immunomodulatory plasticity of mesenchymal stem cells: a potential key to successful solid organ transplantation

Organ transplantation remains to be a treatment of choice for patients suffering from irreversible organ failure. Immunosuppressive (IS) drugs employed to maintain the allograft have shown excellent short-term graft survival, but, their long-term use could contribute to immunological and non-immunological risk factors, resulting in graft dysfunctionalities. Upcoming IS regimes have highlighted the use of cell-based therapies, which can eliminate the risk of drug-borne toxicities while maintaining efficacy of the treatment. Mesenchymal stem cells (MSCs) have been considered as an invaluable cell type, owing to their unique immunomodulatory properties, which makes them desirable for application in transplant settings, where hyper-activation of the immune system is evident. The immunoregulatory potential of MSCs holds true for preclinical studies while achieving it in clinical studies continues to be a challenge. Understanding the biological factors responsible for subdued responses of MSCs in vivo would allow uninhibited use of this therapy for countless conditions. In this review, we summarize the variations in the preclinical and clinical studies utilizing MSCs, discuss the factors which might be responsible for variability in outcome and propose the advancements likely to occur in future for using this as a "boutique/personalised therapy" for patient care.

N-acetyl-L-cysteine protects dental tissue stem cells against oxidative stress in vitro

OBJECTIVES

The aim of our study was to investigate whether N-acetyl-L-cysteine (NAC) could protect stem cells from exfoliated deciduous teeth (SHED) against oxidative damage, during in vitro cultivation, to preserve regenerative potential of these cells. Accordingly, we examined the potential of cell culture supplementation with NAC in prevention of lipid peroxidation, unfavorable changes of total lipids fatty acid composition, and the effects on the activity of antioxidant enzymes.

MATERIAL AND METHODS

We analyzed the extent of oxidative damage in SHED after 48 h treatment with different NAC concentrations. Cellular lipid peroxidation was determined upon reaction with thiobarbituric acid. All enzyme activities were measured spectrophotometrically, based on published methods. Fatty acid methyl esters were analyzed by gas-liquid chromatography.

RESULTS

Concentration of 0.1 mM NAC showed the most profound effects on SHED, significantly decreasing levels of lipid peroxidation in comparison to control. This dose also diminished the activities of antioxidant enzymes. Furthermore, NAC treatment significantly changed fatty acid composition of cells, reducing levels of oleic acid and monounsaturated fatty acids and increasing linoleic acid, n-6, and total polyunsaturated fatty acid (PUFA) proportions.

CONCLUSION

Low dose of NAC significantly decreased lipid peroxidation and altered fatty acid composition towards increasing PUFA. The reduced oxidative damage of cellular lipids could be strongly related to improved SHED survival in vitro.

CLINICAL RELEVANCE

Low doses of antioxidants, applied during stem cells culturing and maintenance, could improve cellular characteristics in vitro. This is prerequisite for successful use of stem cells in various clinical applications.

Automated image analysis detects aging in clinical-grade mesenchymal stromal cell cultures

BACKGROUND

Senescent cells are undesirable in cell therapy products due to reduced therapeutic activity and risk of aberrant cellular effects, and methods for assessing senescence are needed. Early-passage mesenchymal stromal cells (MSCs) are known to be small and spindle-shaped but become enlarged upon cell aging. Indeed, cell morphology is routinely evaluated during MSC production using subjective methods. We have therefore explored the possibility of utilizing automated imaging-based analysis of cell morphology in clinical cell manufacturing.

METHODS

An imaging system was adopted for analyzing changes in cell morphology of bone marrow-derived MSCs during long-term culture. Cells taken from the cultures at the desired passages were plated at low density for imaging, representing morphological changes observed in the clinical-grade cultures. The manifestations of aging and onset of senescence were monitored by population doubling numbers, expression of p16INK4a and p21Cip1/Waf1, β-galactosidase activity, and telomeric terminal restriction fragment analysis.

RESULTS

Cell area was the most statistically significant and practical parameter for describing morphological changes, correlating with biochemical senescence markers. MSCs from passages 1 (p1) and 3 (p3) were remarkably uniform in size, with cell areas between 1800 and 2500 μm2. At p5 the cells began to enlarge resulting in a 4.8-fold increase at p6-9 as compared to p1. The expression of p16INK4a and activity of β-galactosidase had a strong correlation with the increase in cell area, whereas the expression of p21Cip1/Waf1 reached its maximum at the onset of growth arrest and subsequently decreased. Mean telomere length shortened at an apparently constant rate during culture, from 8.2 ± 0.3 kbp at p1, reaching 6.08 ± 0.6 kbp at senescence.

CONCLUSIONS

Imaging analysis of cell morphology is a useful tool for evaluating aging in cell cultures throughout the lifespan of MSCs. Our findings suggest that imaging analysis can reproducibly detect aging-related changes in cell morphology in MSC cultures. These findings suggest that cell morphology is still a supreme measure of cell quality and may be utilized to develop new noninvasive imaging-based methods to screen and quantitate aging in clinical-grade cell cultures.

Expansion induced microRNA changes in bone marrow mesenchymal stromal cells reveals interplay between immune regulation and cell cycle

Mesenchymal stromal cells (MSC) are currently used in many cell based therapies. Prior to use in therapy, extensive expansion is required. We used microarray profiling to investigate expansion induced miRNA and mRNA expression changes of bone marrow MSCs (BM-MSCs) derived from old and young donors. The expression levels of 36 miRNAs were altered in cells derived from the old and respectively 39 miRNAs were altered in cells derived from young donors. Of these, only 12 were differentially expressed in both young and old donor BM-MSCs, and their predicted target mRNAs, were mainly linked to cell proliferation and senescence. Further qPCR verification showed that the expression of miR-1915-3p, miR-1207, miR-3665, and miR-762 correlated with the expansion time at passage 8. Previously described BM-MSC-specific miRNA fingerprints were also detected but these remained unchanged during expansion. Interestingly, members of well-studied miR-17/92 cluster, involved in cell cycle regulation, aging and also development of immune system, were down-regulated specifically in cells from old donors. The role of this cluster in MSC functionality is worth future studies since it links expansion, aging and immune system together.

Methylome Analysis of Human Bone Marrow MSCs Reveals Extensive Age- and Culture-Induced Changes at Distal Regulatory Elements

Human bone marrow stromal cells, or mesenchymal stem cells (BM-MSCs), need expansion prior to use as cell-based therapies in immunological and tissue repair applications. Aging and expansion of BM-MSCs induce epigenetic changes that can impact therapeutic outcomes. By applying sequencing-based methods, we reveal that the breadth of DNA methylation dynamics associated with aging and expansion is greater than previously reported. Methylation changes are enriched at known distal transcription factor binding sites such as enhancer elements, instead of CpG-rich regions, and are associated with changes in gene expression. From this, we constructed hypo- and hypermethylation-specific regulatory networks, including a sub-network of BM-MSC master regulators and their predicted target genes, and identified putatively disrupted signaling pathways. Our genome-wide analyses provide a broader overview of age- and expansion-induced DNA methylation changes and a better understanding of the extent to which these changes alter gene expression and functionality of human BM-MSCs.

Niche matters: The comparison between bone marrow stem cells and endometrial stem cells and stromal fibroblasts reveal distinct migration and cytokine profiles in response to inflammatory stimulus

Objective

Intrinsic inflammatory characteristics play a pivotal role in stem cell recruitment and homing through migration where the subsequent change in niche has been shown to alter these characteristics. The bone marrow mesenchymal stem cells (bmMSCs) have been demonstrated to migrate to the endometrium contributing to the stem cell reservoir and regeneration of endometrial tissue. Thus, the aim of the present study was to compare the inflammation-driven migration and cytokine secretion profile of human bmMSCs to endometrial mesenchymal stem cells (eMSCs) and endometrial fibroblasts (eSFs).

Materials and methods

The bmMSCs were isolated from bone marrow aspirates through culturing, whereas eMSCs and eSFs were FACS-isolated. All cell types were tested for their surface marker, proliferation profiles and migration properties towards serum and inflammatory attractants. The cytokine/chemokine secretion profile of 35 targets was analysed in each cell type at basal level along with lipopolysaccharide (LPS)-induced state.

Results

Both stem cell types, bmMSCs and eMSCs, presented with similar stem cell surface marker profiles as well as possessed high proliferation and migration potential compared to eSFs. In multiplex assays, the secretion of 16 cytokine targets was detected and LPS stimulation expanded the cytokine secretion pattern by triggering the secretion of several targets. The bmMSCs exhibited higher cytokine secretion of vascular endothelial growth factor (VEGF)-A, stromal cell-derived factor-1 alpha (SDF)-1α, interleukin-1 receptor antagonist (IL-1RA), IL-6, interferon-gamma inducible protein (IP)-10, monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)1α and RANTES compared to eMSCs and/or eSFs after stimulation with LPS. The basal IL-8 secretion was higher in both endometrial cell types compared to bmMSCs.

Conclusion

Our results highlight that similar to bmMSCs, the eMSCs possess high migration activity while the differentiation process towards stromal fibroblasts seemed to result in loss of stem cell surface markers, minimal migration activity and a subtler cytokine profile likely contributing to normal endometrial function.

Restored in vivo-like membrane lipidomics positively influence in vitro features of cultured mesenchymal stromal/stem cells derived from human placenta

Background

The study of lipid metabolism in stem cell physiology has recently raised great interest. The role of lipids goes beyond the mere structural involvement in assembling extra- and intra-cellular compartments. Nevertheless, we are still far from understanding the impact of membrane lipidomics in stemness maintenance and differentiation patterns. In the last years, it has been reported how in vitro cell culturing can modify membrane lipidomics. The aim of the present work was to study the membrane fatty acid profile of mesenchymal stromal cells (MSCs) derived from human fetal membranes (hFM-MSCs) and to correlate this to specific biological properties by using chemically defined tailored lipid supplements (Refeed®).

Methods

Freshly isolated hFM-MSCs were characterized for their membrane fatty acid composition. hFM-MSCs were cultivated in vitro following a classical protocol and their membrane fatty acid profile at different passages was compared to the profile in vivo. A tailored Refeed® lipid supplement was developed with the aim of reducing the differences created by the in vitro cultivation and was tested on cultured hFM-MSCs. Cell morphology, viability, proliferation, angiogenic differentiation, and immunomodulatory properties after in vitro exposure to the tailored Refeed® lipid supplement were investigated.

Results

A significant modification of hFM-MSC membrane fatty acid composition occurred during in vitro culture. Using a tailored lipid supplement, the fatty acid composition of cultured cells remained more similar to their in vivo counterparts, being characterized by a higher polyunsaturated and omega-6 fatty acid content. These changes in membrane composition had no effect on cell morphology and viability, but were linked with increased cell proliferation rate, angiogenic differentiation, and immunomodulatory properties. In particular, Refeed®-supplemented hFM-MSCs showed greater ability to express fully functional cell membrane molecules.

Conclusions

Culturing hFM-MSCs alters their fatty acid composition. A tailored lipid supplement is able to improve in vitro hFM-MSC functional properties by recreating a membrane environment more similar to the physiological counterpart. This approach should be considered in cell therapy applications in order to maintain a higher cell quality during in vitro passaging and to influence the outcome of cell-based therapeutic approaches when cells are administered to patients.

Metabolism and phospholipid assembly of polyunsaturated fatty acids in human bone marrow mesenchymal stromal cells

High arachidonic acid (20:4n-6) and low n-3 PUFA levels impair the capacity of cultured human bone marrow mesenchymal stromal cells (hBMSCs) to modulate immune functions. The capacity of the hBMSCs to modify PUFA structures was found to be limited. Therefore, different PUFA supplements given to the cells resulted in very different glycerophospholipid (GPL) species profiles and substrate availability for phospholipases, which have preferences for polar head group and acyl chains when liberating PUFA precursors for production of lipid mediators. When supplemented with 20:4n-6, the cells increased prostaglandin E2 secretion. However, they elongated 20:4n-6 to the less active precursor, 22:4n-6, and also incorporated it into triacylglycerols, which may have limited the proinflammatory signaling. The n-3 PUFA precursor, 18:3n-3, had little potency to reduce the GPL 20:4n-6 content, while the eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acid supplements efficiently displaced the 20:4n-6 acyls, and created diverse GPL species substrate pools allowing attenuation of inflammatory signaling. The results emphasize the importance of choosing appropriate PUFA supplements for in vitro hBMSC expansion and suggests that for optimal function they require an exogenous fatty acid source providing 20:5n-3 and 22:6n-3 sufficiently, but 20:4n-6 moderately, which calls for specifically designed optimal PUFA supplements for the cultures.

A2B5+/GFAP+ Cells of Rat Spinal Cord Share a Similar Lipid Profile with Progenitor Cells: A Comparative Lipidomic Study

The central nervous system (CNS) harbors multiple glial fibrillary acidic protein (GFAP) expressing cell types. In addition to the most abundant cell type of the CNS, the astrocytes, various stem cells and progenitor cells also contain GFAP+ populations. Here, in order to distinguish between two types of GFAP expressing cells with or without the expression of the A2B5 antigens, we performed lipidomic analyses on A2B5+/GFAP+ and A2B5-/GFAP+ cells from rat spinal cord. First, A2B5+/GFAP- progenitors were exposed to the leukemia inhibitory factor (LIF) or bone morphogenetic protein (BMP) to induce their differentiation to A2B5+/GFAP+ cells or A2B5-/GFAP+ astrocytes, respectively. The cells were then analyzed for changes in their phospholipid, sphingolipid or acyl chain profiles by mass spectrometry and gas chromatography. Compared to A2B5+/GFAP- progenitors, A2B5-/GFAP+ astrocytes contained higher amounts of ether phospholipids (especially the species containing arachidonic acid) and sphingomyelin, which may indicate characteristics of cellular differentiation and inability for multipotency. In comparison, principal component analyses revealed that the lipid composition of A2B5+/GFAP+ cells retained many of the characteristics of A2B5+/GFAP- progenitors, but their lipid profile was different from that of A2B5-/GFAP+ astrocytes. Thus, our study demonstrated that two GFAP+ cell populations have distinct lipid profiles with the A2B5+/GFAP+ cells sharing a phospholipid profile with progenitors rather than astrocytes. The progenitor cells may require regulated low levels of lipids known to mediate signaling functions in differentiated cells, and the precursor lipid profiles may serve as one measure of the differentiation capacity of a cell population.