Cell culture density affects the stemness gene expression of adipose tissue-derived mesenchymal stem cells

Optimization of seeding cell density for differentiation of adipose-derived stem cells into epithelial-like cells on bioengineered composite scaffolds

This study investigates the biological factors influencing the epithelial differentiation of adipose-derived stem cells (ASC) to develop an engineered upper airway construct. One fraction of ASC was seeded onto a fibrin sealant (Tisseel) matrix encompassing an additional equal fraction of ASC that has been integrated into a porous polyethylene scaffold (Medpor®). Constructs with ASC seeded at total densities of 5 × 105, 1 × 106, 2.5 × 106, and 5 × 106 cells cm-2 were cultured under submerged conditions for 11 days to achieve partial epithelial differentiation (PD). To simulate post-transplantation exposure to air and interaction with host epithelial cells, PD constructs with ASC at 5 × 106 cells cm-2 were transitioned to air-liquid interface (ALI) conditions for additional 10 days (PD/ALI-21d) or 21 days (PD/ALI-32d). The latter cultures were either maintained alone or co-cultured with bronchial epithelial cells (PD/ALI-32d + BEAS). Gene expressions of mesenchymal and epithelial basal, secretory, and ciliated cell markers were assessed and validated via immunohistochemistry. ASC seeded at 5 × 106 cells cm-2 achieved the highest partial epithelial differentiation, supporting the use of this density for further experiments. In PD/ALI-21d, basal and secretory epithelial marker gene expression significantly increased, while ciliated cell markers remained unchanged. In PD/ALI-32d, expression of basal and goblet cell markers and several mesenchymal stem cell markers decreased, but co-culturing with BEAS maintained the levels of their expression. These results indicate that long-term ALI cultures cannot sustain terminal differentiation of ASC into secretory phenotypes without co-culture with primary epithelial cells. In conclusion, partially differentiated ASC on constructs maintain a stem cell phenotype and may promote differentiation into basal/secretory phenotypes, but not ciliated cells. Enhancing ciliogenesis and ensuring ASC commitment to the epithelial lineage, require modifications to the study design.

Conditioned medium of human umbilical cord-mesenchymal stem cells cultivated with human cord blood serum enhances stem cell stemness and secretome profiles

The proteins secreted by human umbilical cord mesenchymal stem cells (hUC-MSCs) may enhance tissue regeneration and wound healing. Traditional hUC-MSC cultures may not be enough since they undergo recurrent cellular senescence during large-scale production. This decreases the therapeutic ability of hUC-MSCs by altering genes and proteins that control stemness, proliferation, and protein release. Human cord blood serum (CBS) and the middle-density technique were used to evaluate hUC-MSC regeneration ability. To evaluate early-passage hMSCs for secretome-based therapies, they were expanded and secreted in vitro. After 4 days, hUC-MSCs cultivated at 3000 cells/cm2 and supplemented with 1 ng/ml CBS showed increased growth, cell proliferation, and a much lower population doubling time. CBS treatment reduced CD34, CD45, and HLA-DR levels in human umbilical cord mesenchymal stem cells (hUC-MSCs) by less than 2 %. Positive markers such CD73, CD90, and CD105 were found at >97 %, like control hUC-MSCs. Over extended culture, this combination culture can increase survival, proliferation, and stemness and postpone cell death and hUC-MSC senescence. The protein profile and hUC-MSC secretion were improved to make MSC secretion protein therapeutic. This improves cell-free treatment, proliferation, and wound healing in human skin cells. To improve cell-based transplantation or cosmeceutical manufacturing, this technique can boost hUC-MSC regeneration capacity.

Control of spatio-temporal patterning via cell growth in a multicellular synthetic gene circuit

A major goal in synthetic development is to build gene regulatory circuits that control patterning. In natural development, an interplay between mechanical and chemical communication shapes the dynamics of multicellular gene regulatory circuits. For synthetic circuits, how non-genetic properties of the growth environment impact circuit behavior remains poorly explored. Here, we first describe an occurrence of mechano-chemical coupling in synthetic Notch (synNotch) patterning circuits: high cell density decreases synNotch-gated gene expression in different cellular systems in vitro. We then construct, both in vitro and in silico, a synNotch-based signal propagation circuit whose outcome can be regulated by cell density. Spatial and temporal patterning outcomes of this circuit can be predicted and controlled via modulation of cell proliferation, initial cell density, and/or spatial distribution of cell density. Our work demonstrates that synthetic patterning circuit outcome can be controlled via cellular growth, providing a means for programming multicellular circuit patterning outcomes.

Characterization of MSCs expressing islet neogenesis associated protein (INGAP): INGAP secretion and cell survival in vitro and in vivo

Mesenchymal stem/stromal cells (MSCs) are emerging as a new therapy for diabetes. Here we investigate the properties of MSCs engineered to express Islet Neogenesis Associated Protein (INGAP) previously shown to reverse diabetes in animal models and evaluate their potential for anti-diabetic applications in mice. Mouse bone marrow-derived MSCs retrovirally transduced to co-express INGAP, Firefly Luciferase and EGFP (INGAP-MSCs), were characterized in vitro and implanted intraperitoneally (IP) into non-diabetic and diabetic C57BL/6 mice (Streptozotocin model) and tracked by live bioluminescence imaging (BLI). Distribution and survival of IP injected INGAP-MSCs differed between diabetic and non-diabetic mice, with a rapid clearance of cells in the latter, and a stronger retention (up to 4 weeks) in diabetic mice concurring with homing towards the pancreas. Interestingly, INGAP-MSCs inhibited the progression of hyperglycemia starting at day 3 and lasting for the entire 6 weeks of the study. Pursuing greater retention, we investigated the survival of INGAP-MSCs in hydrogel matrices. When mixed with Matrigel™ and injected subcutaneously into non-diabetic mice, INGAP-MSCs remained in the implant up to 16 weeks. In vitro tests in three matrices (Matrigel™, Type I Collagen and VitroGel®-MSC) demonstrated that INGAP-MSCs survive and secrete INGAP, with best results at the density of 1-2 x 106 cells/mL. However, all matrices induced spontaneous adipogenic differentiation of INGAP-MSCs in vitro and in vivo, which requires further investigation of its potential impact on MSC therapeutic properties. In summary, based on their ability to stop the rise in hyperglycemia in STZ-treated mice, INGAP-MSCs are a promising therapeutic tool against diabetes but require further research to improve cell delivery and survival.

Adipogenic differentiation effect of human periodontal ligament stem cell initial cell density on autologous cells and human bone marrow stromal cells

Stem cells demonstrate differentiation and regulatory functions. In this discussion, we will explore the impacts of cell culture density on stem cell proliferation, adipogenesis, and regulatory abilities. This study aimed to investigate the impact of the initial culture density of human periodontal ligament stem cells (hPDLSCs) on the adipogenic differentiation of autologous cells. Our findings indicate that the proliferation rate of hPDLSCs increased with increasing initial cell density (0.5-8 × 104 cells/cm2). After adipogenic differentiation induced by different initial cell densities of hPDLSC, we found that the mean adipose concentration and the expression levels of lipoprotein lipase (LPL), CCAAT/enhancer binding protein α (CEBPα), and peroxisome proliferator-activated receptor γ (PPAR-γ) genes all increased with increasing cell density. To investigate the regulatory role of hPDLSCs in the adipogenic differentiation of other cells, we used secreted exocrine vesicles derived from hPDLSCs cultivated at different initial cell densities of 50 μg/mL to induce the adipogenic differentiation of human bone marrow stromal cells. We also found that the mean adipose concentration and expression of LPL, CEBPα, and PPARγ genes increased with increasing cell density, with an optimal culture density of 8 × 104 cells/cm2. This study provides a foundation for the application of adipogenic differentiation in stem cells.

Integrative transcriptomic and proteomic profiling of the effects of cell confluency on gene expression

In this study we examine the impact of cell confluency on gene expression. We focused on Argonaute (AGO) protein dynamics and associated gene and protein expression in HEK293, A375, and SHSY5Y cell lines. As a consequence of cell confluency, AGO2 protein translocates into the nucleus. Therefore, we generated transcriptomic data using RNA sequencing to compare gene expression in subconfluent versus confluent cells, which highlighted significant alterations in gene regulation patterns directly corresponding to changes in cell density. Our study also encompasses miRNA profiling data obtained through small RNA sequencing, revealing miRNA expressional changes dependent on cellular confluency, as well as cellular localization. Finally, we derived proteomic data from mass spectrometry analyses following AGO1-4 immunoprecipitation, providing a comprehensive view of AGO interactome in both nuclear and cytoplasmic compartments under varying confluency. These datasets offer a detailed exploration of the cellular and molecular dynamics, influenced by cell confluency, presenting a valuable resource for further research in cellular biology, particularly in understanding the basic mechanisms of cell density in cancer cells.

Extracellular Vesicles Generated by Mesenchymal Stem Cells in Stirred Suspension Bioreactors Promote Angiogenesis in Human-Brain-Derived Endothelial Cells

Interrupted blood flow in the brain due to ischemic injuries such as ischemic stroke or traumatic brain injury results in irreversible brain damage, leading to cognitive impairment associated with inflammation, disruption of the blood-brain barrier (BBB), and cell death. Since the BBB only allows entry to a small class of drugs, many drugs used to treat ischemia in other tissues have failed in brain-related disorders. The administration of mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) has shown promise in improving the functional recovery of the brain following cerebral ischemia by inducing blood vessel formation. To facilitate such a treatment approach, it is necessary to develop bioprocesses that can produce therapeutically relevant MSC-EVs in a reproducible and scalable manner. This study evaluated the feasibility of using stirred suspension bioreactors (SSBs) to scale-up the serum-free production of pro-angiogenic MSC-EVs under clinically relevant physioxic conditions. It was found that MSCs grown in SSBs generated EVs that stimulated angiogenesis in cerebral microvascular endothelial cells, supporting the use of SSBs to produce MSC-EVs for application in cerebral ischemia. These properties were impaired at higher cell confluency, outlining the importance of considering the time of harvest when developing bioprocesses to manufacture EV populations.

Conditioned medium-enriched umbilical cord mesenchymal stem cells: a potential therapeutic strategy for spinal cord injury, unveiling transcriptomic and secretomic insights

INTRODUCTION

Spinal cord injury (SCI) leads to significant destruction of nerve tissue, causing the degeneration of axons and the formation of cystic cavities. This study aimed to examine the characteristics of human umbilical cord-derived mesenchymal stem cells (HUCMSCs) cultured in a serum-free conditioned medium (CM) and assess their effectiveness in a well-established hemitransection SCI model.

MATERIALS AND METHODS

In this study, HUCMSCs cultured medium was collected and characterized by measuring IL-10 and identifying proteomics using mass spectroscopy. This collected serum-free CM was further used in the experiments to culture and characterize the HUMSCs. Later, neuronal cells derived from CM-enriched HUCMSC were tested sequentially using an injectable caffeic acid-bioconjugated gelatin (CBG), which was further transplanted in a hemitransection SCI model. In vitro, characterization of CM-enriched HUCMSCs and differentiated neuronal cells was performed using flow cytometry, immunofluorescence, electron microscopy, and post-transplant analysis using immunohistology analysis, qPCR, in vivo bioluminescence imaging, and behavioral analysis using an infrared actimeter.

RESULTS

The cells that were cultured in the conditioned media produced a pro-inflammatory cytokine called IL-10. Upon examining the secretome of the conditioned media, the Kruppel-like family of KRAB and zinc-finger proteins (C2H2 and C4) were found to be activated. Transcriptome analysis also revealed an increased expression of ELK-1, HOXD8, OTX2, YY1, STAT1, ETV7, and PATZ1 in the conditioned media. Furthermore, the expression of Human Stem-101 confirmed proliferation during the first 3 weeks after transplantation, along with the migration of CBG-UCNSC cells within the transplanted area. The gene analysis showed increased expression of Nestin, NeuN, Calb-2, Msi1, and Msi2. The group that received CBG-UCNSC therapy showed a smooth recovery by the end of week 2, with most rats regaining their walking abilities similar to those before the spinal cord injury by week 5.

CONCLUSIONS

In conclusion, the CBG-UCNSC method effectively preserved the integrity of the transplanted neuronal-like cells and improved locomotor function. Thus, CM-enriched cells can potentially reduce biosafety risks associated with animal content, making them a promising option for clinical applications in treating spinal cord injuries.

Culture media and format alter cellular composition and barrier integrity of porcine colonoid-derived monolayers

Intestinal organoid technology has revolutionized our approach to in vitro cell culture due in part to their three-dimensional structures being more like the native tissue from which they were derived with respect to cellular composition and architecture. For this reason, organoids are becoming the new gold standard for undertaking intestinal epithelial cell research. Unfortunately, their otherwise advantageous three-dimensional geometry prevents easy access to the apical epithelium, which is a major limitation when studying interactions between dietary or microbial components and host tissues. To overcome this problem, we developed porcine colonoid-derived monolayers cultured on both permeable Transwell inserts and tissue culture treated polystyrene plates. We found that seeding density and culture format altered the expression of genes encoding markers of specific cell types (stem cells, colonocytes, goblets, and enteroendocrine cells), and barrier maturation (tight junctions). Additionally, we found that changes to the formulation of the culture medium altered the cellular composition of colonoids and of monolayers derived from them, resulting in cultures with an increasingly differentiated phenotype that was similar to that of their tissue of origin.

Alveolar mucosal cell spheroids promote extraction socket healing and osseous defect regeneration

BACKGROUND

Alveolar mucosa could be a promising source of mesenchymal stem cells (MSCs) for regeneration therapeutics because it exhibits faster healing potential and can be easily collected with minimal periodontal disturbance. This study aimed to evaluate the potential of alveolar mucosal cell (AMC) spheroids for promoting extraction socket healing and calvarial osseous defect regeneration.

METHODS

AMCs were isolated from Sprague-Dawley rats. Antigenic and MSC surface marker expressions and trilineage differentiation capability were assessed. AMCs were then osteogenically stimulated (OAs) or unstimulated (UAs), self-aggregated to form spheroids, and encapsulated in gelatin hydrogel to fill rat extraction sockets or combined with freeze-dried bone graft (FDBG) to fill rat calvarial osseous defects. The outcome was assessed by gross observation, micro-CT imaging, and immunohistochemistry.

RESULTS

AMCs highly expressed MSC surface markers, showed weak antigenicity, and were capable of trilineage differentiation at Passage 3. In the extraction sockets, wound closure, socket fill, keratinization, and proliferative activities were accelerated in those with AMC spheroids treatment. Socket fill and maturation were further promoted by OA spheroids. In the calvarial osseous defects, the mineralized tissue ratio was promoted with AMC spheroids/FDBG treatment, and bone sialoprotein expression and cell proliferation were more evident with OA spheroids/FDBG treatment.

CONCLUSION

AMCs exhibited MSC properties with weak antigenicity. AMC spheroids promoted extraction socket healing, AMC spheroids/FDBG promoted calvarial osseous defect regeneration, and the outcomes were further enhanced by osteogenically stimulation of AMCs.

Impact of Anti-Mycotic Drugs on the Osteogenic Response of Bone Marrow Mesenchymal Stem Cells In Vitro

The treatment of fungal bone infections and infected non-unions is a huge challenge in modern trauma and orthopedics, which normally contain the local and systemic administration of anti-fungal drugs. Although frequently used, little is known about the impact of systemic and locally administered fungicides on the osteogenic regenerative capabilities of infected bone tissue, especially upon the osteogenesis of human bone marrow mesenchymal stem cells (BM-hMSCs). This study evaluates the effects of the three most common fungicides for the systemic treatment of bone infections, Voriconazole (VOR), liposomal Amphotericin B (LAMB), and Fluconazole (FLU), as well as the effects of VOR and LAMB-loaded Polymethylmethacrylate (PMMA) cement chips in different concentrations upon the osteogenic response of BM-hMSCs in vitro. Within this study, we compared the ability of BM-hMSC to differentiate into osteoblast-like cells and synthesize hydroxyapatite as assessed by radioactive 99mTechnetium-Hydroxydiphosphonate (99mTc-HDP) labeling, cell proliferation, and analyses of supernatants upon various osteogenic parameters. Our results revealed that VOR added to the cell culture medium affects the osteogenic potential of BM-hMSC negatively, while there were no detectable effects of LAMB and FLU. Moreover, we showed dose-dependent negative effects of high- and extended-dose fungicide-loaded PMMA cement due to cytotoxicity, with a higher cytotoxic potential of VOR than LAMB, while low-dose fungicide-loaded PMMA had no significant effect on the osteogenic potential of BM-hMSC in vitro.

Anti-inflammatory Effects of Umbilical Cord Mesenchymal Stem Cell and Autologous Conditioned Serum on Oligodendrocyte, Astrocyte, and Microglial Specific Gene in Cuprizone Animal Model

BACKGROUND

Inflammation, myelin loss, astrocytosis, and microgliosis are pathological signs of the autoimmune and demyelinating disease known as multiple sclerosis (MS). Axonal and neuronal degenerations have basic molecular pathways. The remyelination process can be influenced by the secretome of mesenchymal stem cells due to their capacity for immunomodulation, differentiation, and neuroprotection. Microglial cells are divided into two subgroups: M1 and M2 phenotypes. A crucial component of the microglial function is the colony stimulating factor 1 receptor (CSF1R). We aimed to evaluate the immunomodulating effects of secretome and conditioned serum on the microglial phenotypes and improvement of demyelination in a cuprizone model of MS.

METHODS

The study used 48 male C57BL/6 mice, which were randomly distributed into 6 subgroups (n = 8), i.e., control, cuprizone, MSC (confluency 40% and 80%) secretome group, and blood derived conditioned serum (autologous and humanized). The animals were fed with 0.2% cuprizone diet for 12 weeks. Supplements were injected into the lateral tail vein using a 27-gauge needle every 3 days 500 μl per injection.

RESULTS

At 14 days after transplantation, animals from each group were sacrificed and analyzed by Real time PCR. The results showed that the administration of MSC secretome can efficiently reduce expression of pro-inflammatory cytokines (IL-1, IL6 and TNF-α) in the corpus callosum; also, conditioned serum downregulated IL-1. Moreover, the oligodendrocyte-specific gene was upregulated by secretome and conditioned serum treatment. Also, the expression of microglial- specific gene was reduced after treatment.

CONCLUSION

These findings demonstrated that the secretome isolated from MSCs used as a therapy decreased and increased the M1 and M2 levels, respectively, to control neuroinflammation in CPZ mice. In conclusion, the current study showed the viability of devising a method to prepare suitable MSCs and secreted factor to cure neurodegenerative diseases, as well as the capability of regulating MSC secretome patterns by manipulating the cell density.

LADON, a Natural Antisense Transcript of NODAL, Promotes Tumour Progression and Metastasis in Melanoma

The TGFβ family member NODAL, repeatedly required during embryonic development, has also been associated with tumour progression. Our aim was to clarify the controversy surrounding its involvement in melanoma tumour progression. We found that the deletion of the NODAL exon 2 in a metastatic melanoma cell line impairs its ability to form tumours and colonize distant tissues. However, we show that this phenotype does not result from the absence of NODAL, but from a defect in the expression of a natural antisense transcript of NODAL, here called LADON. We show that LADON expression is specifically activated in metastatic melanoma cell lines, that its transcript is packaged in exosomes secreted by melanoma cells, and that, via its differential impact on the expression of oncogenes and tumour suppressors, it promotes the mesenchymal to amoeboid transition that is critical for melanoma cell invasiveness. LADON is, therefore, a new player in the regulatory network governing tumour progression in melanoma and possibly in other types of cancer.

Expansion of human bone marrow-derived mesenchymal stromal cells with enhanced immunomodulatory properties

BACKGROUND

Mesenchymal stromal cells (MSCs) have broad potential as a cell therapy including for the treatment of drug-resistant inflammatory conditions with abnormal T cell proliferation such as graft-versus-host disease (GVHD). Clinical success, however, has been complicated by the heterogeneity of culture-expanded MSCs as well as donor variability. Here, we devise culture conditions that promote expansion of MSCs with enhanced immunomodulatory functions both in vitro and in animal models of GVHD.

METHODS

Human bone marrow-derived MSCs were expanded at high-confluency (MSCHC) and low-confluency state (MSCLC). Their immunomodulatory properties were evaluated with in vitro co-culture assays based on suppression of activated T cell proliferation and secretion of pro-inflammatory cytokines from activated T cells. Metabolic state of these cells was determined, while RNA sequencing was performed to explore transcriptome of these MSCs. Ex vivo expanded MSCHC or MSCLC was injected into human peripheral blood mononuclear cells (PBMC)-induced GVHD mouse model to determine their in vivo therapeutic efficacy based on clinical grade scoring, human CD45+ blood count and histopathological examination.

RESULTS

As compared to MSCLC, MSCHC significantly reduced both the proliferation of anti-CD3/CD28-activated T cells and secretion of pro-inflammatory cytokines upon MSCHC co-culture across several donors even in the absence of cytokine priming. Mechanistically, metabolic analysis of MSCHC prior to co-culture with activated T cells showed increased glycolytic metabolism and lactate secretion compared to MSCLC, consistent with their ability to inhibit T cell proliferation. Transcriptome analysis further revealed differential expression of immunomodulatory genes including TRIM29, BPIFB4, MMP3 and SPP1 in MSCHC as well as enriched pathways including cytokine-cytokine receptor interactions, cell adhesion and PI3K-AKT signalling. Lastly, we demonstrate in a human PBMC-induced GVHD mouse model that delivery of MSCHC showed greater suppression of inflammation and improved outcomes compared to MSCLC and saline controls.

CONCLUSION

Our study provides evidence that ex vivo expansion of MSCs at high confluency alters the metabolic and transcriptomic states of these cells. Importantly, this approach maximizes the production of MSCs with enhanced immunomodulatory functions without priming, thus providing a non-invasive and generalizable strategy for improving the use of MSCs for the treatment of inflammatory diseases.

Towards the Standardization of Mesenchymal Stem Cell Secretome-Derived Product Manufacturing for Tissue Regeneration

Mesenchymal stem cell secretome or conditioned medium (MSC-CM) is a combination of biomolecules and growth factors in cell culture growth medium, secreted by mesenchymal stem cells (MSCs), and the starting point of several derived products. MSC-CM and its derivatives could be applied after injuries and could mediate most of the beneficial regenerative effects of MSCs without the possible side effects of using MSCs themselves. However, before the clinical application of these promising biopharmaceuticals, several issues such as manufacturing protocols and quality control must be addressed. This review aims to underline the influence of the procedure for conditioned medium production on the quality of the secretome and its derivatives and highlights the questions considering cell sources and donors, cell expansion, cell passage number and confluency, conditioning period, cell culture medium, microenvironment cues, and secretome-derived product purification. A high degree of variability in MSC secretomes is revealed based on these parameters, confirming the need to standardize and optimize protocols. Understanding how bioprocessing and manufacturing conditions interact to determine the quantity, quality, and profile of MSC-CM is essential to the development of good manufacturing practice (GMP)-compliant procedures suitable for replacing mesenchymal stem cells in regenerative medicine.

Osteogenic Differentiation Effect of Human Periodontal Ligament Stem-Cell Initial Cell Density on Autologous Cells and Human Bone Marrow Stromal Cells

Stem cells have differentiation and regulation functions. Here, we discussed the impact of cell culture density on stem cell proliferation, osteoblastogenesis, and regulation. To discuss the effect of the initial culture density of human periodontal ligament stem cells (hPDLSCs) on the osteogenic differentiation of autologous cells, we found that the hPDLSC proliferation rate decreased with an increase in the initial plating density (0.5-8 × 10⁴ cells/cm²) for the 48 h culture cycle. After hPDLSCs induced osteogenic differentiation for 14 days with different initial cell culture densities, the expression of osteoprotegerin (OPG) and runt-related transcription factor 2(RUNX2) and the OPG/ Receptor Activator of Nuclear Factor-κ B Ligand (RANKL) ratio were the highest in the hPDLSCs initially plated at a density of 2 × 10⁴ cells/cm², and the average cell calcium concentration was also the highest. To study hPDLSCs regulating the osteoblastic differentiation of other cells, we used 50 μg/mL of secreted exosomes derived from hPDLSCs cultured using different initial cell densities to induce human bone marrow stromal cell (hBMSC) osteogenesis. After 14 days, the results indicated that the gene expression of OPG, Osteocalcin(OCN,)RUNX2, and osterix and the OPG/RANKL ratio were the highest in the 2 × 10⁴ cells/cm² initial cell density group, and the average calcium concentration was also the highest. This provides a new idea for the clinical application of stem cell osteogenesis.

RNF213 Loss-of-Function Promotes Angiogenesis of Cerebral Microvascular Endothelial Cells in a Cellular State Dependent Manner

Enhanced and aberrant angiogenesis is one of the main features of Moyamoya disease (MMD) pathogenesis. The ring finger protein 213 (RNF213) and the variant p.R4810K have been linked with higher risks of MMD and intracranial arterial occlusion development in east Asian populations. The role of RNF213 in diverse aspects of the angiogenic process, such as proliferation, migration and capillary-like formation, is well-known but has been difficult to model in vitro. To evaluate the effect of the RNF213 MMD-associated gene on the angiogenic activity, we have generated RNF213 knockout in human cerebral microvascular endothelial cells (hCMEC/D3-RNF213^-/-) using the CRISPR-Cas9 system. Matrigel-based assay and a tri-dimensional (3D) vascularized model using the self-assembly approach of tissue engineering were used to assess the formation of capillary-like structures. Quite interestingly, this innovative in vitro model of MMD recapitulated, for the first time, disease-associated pathophysiological features such as significant increase in angiogenesis in confluent endothelial cells devoid of RNF213 expression. These cells, grown to confluence, also showed a pro-angiogenic signature, i.e., increased secretion of soluble pro-angiogenic factors, that could be eventually used as biomarkers. Interestingly, we demonstrated that that these MMD-associated phenotypes are dependent of the cellular state, as only noted in confluent cells and not in proliferative RNF213-deficient cells.

Comparative study of differentiating human pluripotent stem cells into vascular smooth muscle cells in hydrogel-based culture methods

Vascular smooth muscle cells (VSMCs), which provides structural integrity and regulates the diameter of vasculature, are of great potential for modeling vascular-associated diseases and tissue engineering. Here, we presented a detailed comparison of differentiating human pluripotent stem cells (hPSCs) into VSMCs (hPSCs-VSMCs) in four different culture methods, including 2-dimensional (2D) culture, 3-dimensional (3D) PNIPAAm-PEG hydrogel culture, 3-dimensional (3D) alginate hydrogel culture, and transferring 3-dimensional alginate hydrogel culture to 2-dimensional (2D) culture. Both hydrogel-based culture methods could mimic in vivo microenvironment to protect cells from shear force, and avoid cells agglomeration, resulting in the extremely high culture efficiency (e.g., high viability, high purity and high yield) compared with 2D culture. We demonstrated hPSC-VSMCs produced from hydrogel-based culture methods had better contractile phenotypes and the potential of vasculature formation. The transcriptome analysis showed the hPSC-VSMCs derived from hydrogel-based culture methods displayed more upregulated genes in vasculature development, angiogenesis and blood vessel development, extracellular matrix compared with 2D culture. Taken together, hPSC-VSMCs produced from hydrogel-based culture system could be applied in various biomedical fields, and further indicated the suitable development of alginate hydrogel for industrial production by taking all aspects into consideration.

Optimization of Mesenchymal Stromal Cell (MSC) Manufacturing Processes for a Better Therapeutic Outcome

MSCs products as well as their derived extracellular vesicles, are currently being explored as advanced biologics in cell-based therapies with high expectations for their clinical use in the next few years. In recent years, various strategies designed for improving the therapeutic potential of mesenchymal stromal cells (MSCs), including pre-conditioning for enhanced cytokine production, improved cell homing and strengthening of immunomodulatory properties, have been developed but the manufacture and handling of these cells for their use as advanced therapy medicinal products (ATMPs) remains insufficiently studied, and available data are mainly related to non-industrial processes. In the present article, we will review this topic, analyzing current information on the specific regulations, the selection of living donors as well as MSCs from different sources (bone marrow, adipose tissue, umbilical cord, etc.), in-process quality controls for ensuring cell efficiency and safety during all stages of the manual and automatic (bioreactors) manufacturing process, including cryopreservation, the use of cell banks, handling medicines, transport systems of ATMPs, among other related aspects, according to European and US legislation. Our aim is to provide a guide for a better, homogeneous manufacturing of therapeutic cellular products with special reference to MSCs.

β-catenin links cell seeding density to global gene expression during mouse embryonic stem cell differentiation

Although cell density is known to affect numerous biological processes including gene expression and cell fate specification, mechanistic understanding of what factors link cell density to global gene regulation is lacking. Here, we reveal that the expression of thousands of genes in mouse embryonic stem cells (mESCs) is affected by cell seeding density and that low cell density enhances the efficiency of differentiation. Mechanistically, β-catenin is localized primarily to adherens junctions during both self-renewal and differentiation at high density. However, when mESCs differentiate at low density, β-catenin translocates to the nucleus and associates with Tcf7l1, inducing co-occupied lineage markers. Meanwhile, Esrrb sustains the expression of pluripotency-associated genes while repressing lineage markers at high density, and its association with DNA decreases at low density. Our results provide new insights into the previously neglected but pervasive phenomenon of density-dependent gene regulation.

Comparison of the Confluence-Initiated Neurogenic Differentiation Tendency of Adipose-Derived and Bone Marrow-Derived Mesenchymal Stem Cells

Adipose-derived mesenchymal stem cells (ADSCs), which tended to neurogenically differentiate spontaneously after achieving high confluence, were observed. Human ADSCs reaching 80% confluence were cultured in DMEM without an inducing factor for 24 h and then maintained in DMEM plus 1% FBS medium for 7 days. The neurogenic, adipogenic, and osteogenic genes of the factor-induced and confluence-initiated differentiation of the ADSCs and bone marrow-derived mesenchymal stem cells (BMSCs) at passages 3 to 5 were determined and compared using RT-qPCR, and the neurogenic differentiation was confirmed using immunofluorescent staining. In vitro tests revealed that the RNA and protein expression of neuronal markers, including class III β-tubulin (TUBB3), microtubule-associated protein 2 (MAP2), neurofilament medium polypeptide (NEFM), neurofilament heavy polypeptide (NEFH), and neurofilament light polypeptide (NEFL), had been enhanced in the confluence-initiated differentiation of the ADSCs. In addition, the expressions of neurotrophins, such as the nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and glial cell-derived neurotrophic factor (GDNF), were also elevated in the confluence-initiated differentiation of the ADSCs. However, the confluent ADSCs did not show a tendency toward spontaneous adipogenic and osteogenic differentiation. Moreover, compared with the confluent ADSCs, the tendency of spontaneous neurogenic, adipogenic, and osteogenic differentiation of the confluent human bone marrow mesenchymal stem cells (BMSCs) was not observed. The results indicated that ADSCs had the potential to spontaneously differentiate into neuron-like cells during the confluent culture period; however, this tendency was not observed in BMSCs.

When Origin Matters: Properties of Mesenchymal Stromal Cells From Different Sources for Clinical Translation in Kidney Disease

Advanced therapy medicinal products (ATMPs) offer new prospects to improve the treatment of conditions with unmet medical needs. Kidney diseases are a current major health concern with an increasing global prevalence. Chronic renal failure appears after many years of impairment, which opens a temporary window to apply novel therapeutic approaches to delay or halt disease progression. The immunomodulatory, anti-inflammatory, and pro-regenerative properties of mesenchymal stromal cells (MSCs) have sparked interest for their use in cell-based regenerative therapies. Currently, several early-phase clinical trials have been completed and many are ongoing to explore MSC safety and efficacy in a wide range of nephropathies. However, one of the current roadblocks to the clinical translation of MSC therapies relates to the lack of standardization and harmonization of MSC manufacturing protocols, which currently hinders inter-study comparability. Studies have shown that cell culture processing variables can have significant effects on MSC phenotype and functionality, and these are highly variable across laboratories. In addition, heterogeneity within MSC populations is another obstacle. Furthermore, MSCs may be isolated from several sources which adds another variable to the comparative assessment of outcomes. There is now a growing body of literature highlighting unique and distinctive properties of MSCs according to the tissue origin, and that characteristics such as donor, age, sex and underlying medical conditions may alter the therapeutic effect of MSCs. These variables must be taken into consideration when developing a cell therapy product. Having an optimal scale-up strategy for MSC manufacturing is critical for ensuring product quality while minimizing costs and time of production, as well as avoiding potential risks. Ideally, optimal scale-up strategies must be carefully considered and identified during the early stages of development, as making changes later in the bioprocess workflow will require re-optimization and validation, which may have a significant long-term impact on the cost of the therapy. This article provides a summary of important cell culture processing variables to consider in the scale-up of MSC manufacturing as well as giving a comprehensive review of tissue of origin-specific biological characteristics of MSCs and their use in current clinical trials in a range of renal pathologies.

Preparation of Cell-Seeded Heart Patch In Vitro; Co-Culture of Adipose-Derived Mesenchymal Stem Cell and Cardiomyocytes in Amnion Bilayer Patch

INTRODUCTION

Cardiovascular disease is the second killer across the globe, while coronary disease is the major cause. Cell therapy is one alternative to regenerate the infarcted heart wall.

MATERIALS AND METHODS

In this study, the cardiomyogenesis capacity of human adipose stem cells (hAdSC) and human cardiomyocytes (hCardio) cultured in a 3-D biological scaffold (decellularised amnion bilayer) for nine days in a static condition was investigated. The cardiomyogenesis capacity of hAdSC were identified using immunohistochemistry and RT-PCR. The population of the cells isolated from the heart tissue expressed cTnT-1 (13.38 ± 11.38%), cKit (7.85 ± 4.2%), ICAM (85.53 ± 8.69%), PECAM (61.63 ± 7.18%) and VCAM (35.9 ± 9.11%), while from the fat tissue expressed the mesenchymal phenotypes (CD73, CD90, CD105, but not CD45, CD34, CD11b, CD19 and HLA-DR). Two age groups of hAdSC donors were compared, the youngsters (30-40yo) and the elderly (60-70 yo).

RESULTS

The co-culture showed that after 5-day incubation, the seeded graft in the hAdSC-30 group had a tube-like appearance while the hAdSC-60 group demonstrated a disorganised pattern, despite of the MSC expressions of the hAdSC-60 were significantly higher. Initial co-culture showed no difference of ATP counts among all groups, however the hAdSC-30 group had the highest ATP count after 9 days culture (p = 0.004). After normalising to the normal myocardium, only the hAdSC-60 group expressed cTnT and MHC, very low, seen during the initial cultivation, but then disappeared. Meanwhile, the hAdSC-30 group expressed α-actinin, MHC and cTnT in the Day-5. The PPAR also was higher in the Day-5 compared to the Day-9 (p < 0.005).

CONCLUSION

Cardiomyogenesis capacity of hAdSC co-cultured with hCardio in a 3-D scaffold taken from the 30-40yo donor showed better morphology and viability than the 60-70yo group, but maintained less than 5 days in this system.

Evening the playing field: microenvironmental control over stem cell competition during fate programming

Recent advancements in cellular engineering, including reprogramming of somatic cells into pluripotent stem cells, have opened the door to a new era of regenerative medicine. Given that cellular decisions are guided by microenvironmental cues, such as secreted factors and interactions with neighbouring cells, reproducible cell manufacturing requires robust control over cell-cell interactions. Cell competition has recently emerged as a previously unknown interaction that plays a significant role in shaping the growth and death dynamics of multicellular stem cell populations, both in vivo and in vitro. Although recent studies have largely focused on exploring how the differential expression of key genes mediate the competitive elimination of some cells, little is known about the impact of the microenvironment on cell competition, despite its critical role in shaping cell fate outcomes. Here, we explore recent findings that have brought cell competition into the spotlight, while dissecting the role of microenvironmental factors for controlling competition in cell fate programming applications.

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.

Functional Activity of Non-Proliferating Mesenchymal Stromal Cells Cultured at Different Densities

We analyzed the state of intracellular compartments and production of cytokines in MSC depending on the culture density. MSC were growth-arrested with mitomycin C and seeded at a density of 300-7000 cell/cm2. MSC in low-density cultures had 2-fold higher levels of transmembrane mitochondrial potential (MitoTracker Red) and endogenous ROS (CMH₂DCFDA), lysosomal compartments were less acidified (LysoTracker Green DND26), the production of immunoregulatory and angiogenic mediators VEGF, IL-6, IL-8, MCP-1, TGF-β was more intensive. It was assumed that culture density can be an effective tool for phenotypic polarization of MSC providing directional changes in their properties.

Culturing at Low Cell Density Delays Cellular Senescence of Human Bone Marrow-Derived Mesenchymal Stem Cells in Long-Term Cultures

Background and Objectives

Mesenchymal stem cells (MSCs) have immense therapeutic potential for treating intractable and immune diseases. They also have applications in regenerative medicine in which distinct treatments do not exist. Thus, MSCs are gaining attention as important raw materials in the field of cell therapy. Importantly, the number of MSCs in the bone marrow is limited and they are present only in small quantities. Therefore, mass production of MSCs through long-term culture is necessary to use them in cell therapy. However, MSCs undergo cellular senescence through repeated passages during mass production. In this study, we explored methods to prolong the limited lifetime of MSCs by culturing them with different seeding densities.

Methods and Results

We observed that in long-term cultures, low-density (LD, 50 cells/cm²) MSCs showed higher population doubling level, leading to greater fold increase, than high-density (HD, 4,000 cells/cm²) MSCs. LD-MSCs suppressed the expression of aging-related genes. We also showed that reactive oxygen species (ROS) were decreased in LD-MSCs compared to that in HD-MSCs. Further, proliferation potential increased when ROS were inhibited in HD-MSCs.

Conclusions

The results in this study suggest that MSC senescence can be delayed and that life span can be extended by controlling cell density in vitro. These results can be used as important data for the mass production of stem cell therapeutic products.

Mesenchymal Stem Cells Current Clinical Applications: A Systematic Review

INTRODUCTION

Human Mesenchymal Stem Cells (hMSCs) are multipotent stem cells capable of renewing themselves and differentiation in vitro into different kinds of tissues. In vivo hMSCs are sources of trophic factors modulating the immune system and inducing intrinsic stem cells to repair damaged tissues. Currently, there are multiple clinical trials (CT) using hMSCs for therapeutic purposes in a large number of clinical settings.

MATERIAL AND METHODS

The search strategy on clinicaltrials.gov has focused on the key term "Mesenchymal Stem Cells", and the inclusion and exclusion criteria were separated into two stages. Stage 1, CT on phases 1-4: location, the field of application, phase, and status. For stage 2, CT that have published outcome results: field of application, treatment, intervention model, source, preparation methods, and results.

RESULTS

By July 2020, there were a total of 1,138 registered CT. Most studies belong to either phase 2 (61.0%) or phase 1 (30.8%); most of them focused in the fields of traumatology, neurology, cardiology, and immunology. Only 18 clinical trials had published results: the most common source of isolation was bone marrow; the treatment varied from 1-200 M hMSCs; all of them have similar preparation methods; all of them have positive results with no serious adverse effects.

CONCLUSIONS

There appears to be a broad potential for the clinical use of hMSCs with no reported serious adverse events. There are many trials in progress, their future results will help to explore the therapeutic potential of these promising cellular sources of medicinal signals.

Remarkable migration propensity of dental pulp stem cells towards neurodegenerative milieu: An in vitro analysis

Stem cell therapy provides a ray of hope for treating neurodegenerative diseases (ND). Bone marrow mesenchymal stem cells (BM-MSC) were extensively investigated for their role in neuroregeneration. However, drawbacks like painful bone marrow extraction, less proliferation and poor CNS engraftment following systemic injections of BM-MSC prompt us to search for alternate/appropriate source of MSC for treating ND. In this context, dental pulp stem cells (DPSC) could be an alternative to BM-MSC as it possess both mesenchymal and neural characteristic features due to its origin from ectoderm, ease of isolation, higher proliferation index and better neuroprotection. A study on the migration potential of DPSC compared to BM-MSC in a neurodegenerative condition is warranted. Given the neural crest origin, we hypothesize that DPSC possess better migration towards neurodegenerative milieu as compared to BM-MSC. In this prospect, we investigated the migration potential of DPSC in an in vitro neurodegenerative condition. Towards this, transwell, Matrigel and chorioallantoic membrane (CAM) migration assays were carried-out by seeding hippocampal neurons in the lower chamber and treated with 300 μM kainic acid (KA) for 6 h to induce neurodegeneration. Subsequently, the upper chamber of transwell was loaded with DPSC/BM-MSC and their migration potential was assessed following 24 h of incubation. Our results revealed that the migration potential of DPSC/BM-MSC was comparable in non-degenerative condition. However, following injury the migration potential of DPSC towards the degenerating site was significantly higher as compared to BM-MSC. Furthermore, upon exposure of naïve DPSC/BM-MSCs to culture medium derived from neurodegenerative milieu resulted in significant upregulation of homing factors like SDF-1alpha, CXCR-4, VCAM-1, VLA-4, CD44, MMP-2 suggesting that the superior migration potential of DPSC might be due to prompt expression of homing factors in DPSC compared to BM-MSCs.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

An Approach towards a GMP Compliant In-Vitro Expansion of Human Adipose Stem Cells for Autologous Therapies

Human Adipose Tissue Stem Cells (hASCs) are a valuable source of cells for clinical applications (e.g., treatment of acute myocardial infarction and inflammatory diseases), especially in the field of regenerative medicine. However, for autologous (patient-specific) and allogeneic (off-the-shelf) hASC-based therapies, in-vitro expansion is necessary prior to the clinical application in order to achieve the required cell numbers. Safe, reproducible and economic in-vitro expansion of hASCs for autologous therapies is more problematic because the cell material changes for each treatment. Moreover, cell material is normally isolated from non-healthy or older patients, which further complicates successful in-vitro expansion. Hence, the goal of this study was to perform cell expansion studies with hASCs isolated from two different patients/donors (i.e., different ages and health statuses) under xeno- and serum-free conditions in static, planar (2D) and dynamically mixed (3D) cultivation systems. Our primary aim was I) to compare donor variability under in-vitro conditions and II) to develop and establish an unstructured, segregated growth model as a proof-of-concept study. Maximum cell densities of between 0.49 and 0.65 × 10⁵ hASCs/cm² were achieved for both donors in 2D and 3D cultivation systems. Cell growth under static and dynamically mixed conditions was comparable, which demonstrated that hydrodynamic stresses (P/V = 0.63 W/m³, τ_nt = 4.96 × 10⁻³ Pa) acting at N_s1u (49 rpm for 10 g/L) did not negatively affect cell growth, even under serum-free conditions. However, donor-dependent differences in the cell size were found, which resulted in significantly different maximum cell densities for each of the two donors. In both cases, stemness was well maintained under static 2D and dynamic 3D conditions, as long as the cells were not hyperconfluent. The optimal point for cell harvesting was identified as between cell densities of 0.41 and 0.56 × 10⁵ hASCs/cm² (end of exponential growth phase). The growth model delivered reliable predictions for cell growth, substrate consumption and metabolite production in both types of cultivation systems. Therefore, the model can be used as a basis for future investigations in order to develop a robust MC-based hASC production process for autologous therapies.

Bone tissue engineering using adipose-derived stem cells and endothelial cells: Effects of the cell ratio

The microvascular endothelial network is essential for bone formation and regeneration. In this context, endothelial cells not only support vascularization but also influence bone physiology via cell contact-dependent mechanisms. In order to improve vascularization and osteogenesis in tissue engineering applications, several strategies have been developed. One promising approach is the coapplication of endothelial and adipose derived stem cells (ADSCs). In this study, we aimed at investigating the best ratio of human umbilical vein endothelial cells (HUVECs) and osteogenic differentiated ADSCs with regard to proliferation, apoptosis, osteogenesis and angiogenesis. For this purpose, cocultures of ADSCs and HUVECs with ratios of 25%:75%, 50%:50% and 75%:25% were performed. We were able to prove that cocultivation supports proliferation whereas apoptosis was unidirectional decreased in cocultured HUVECs mediated by a p-BAD-dependent mechanism. Moreover, coculturing ADSCs and HUVECs stimulated matrix mineralization and the activity of alkaline phosphatase (ALP). Increased gene expression of the proangiogenic markers eNOS, Flt, Ang2 and MMP3 as well as sprouting phenomena in matrigel assays proved the angiogenic potential of the coculture. In summary, coculturing ADSCs and HUVECs stimulates proliferation, cell survival, osteogenesis and angiogenesis particularly in the 50%:50% coculture.

Cloning of human cord blood-mesenchymal stem cells for isolation of enriched cell population of higher proliferation and differentiation potential

Heterogeneity of Mesenchymal stem cells (MSCs) imposes limitations for their in vitro expansion and accounts for the lack of reproducibility in some clinical studies. So, this study was designed to isolate and enrich clones of multipotent and self-renewing MSCs from cord blood (CB). Enriched clones with higher proliferation and differentiation potential provide regenerative cells suitable for various clinical demands. MSCA and MSCB original (progenitor) cells were isolated from CB samples, and single cells were cloned by limiting dilution method, in mouse embryonic fibroblast conditioned media. Original MSCs and their single-cell derived clones were characterized by identifying their proliferation rate, immunophenotyping of surface antigens, expression of pluripotency and proliferation genes (Oct4, Sox2, Nanog, KLF4, c-Myc, and PDGFRA), and differentiation potential into multiple lineages (osteogenic, adipogenic, and chondrogenic). Some single-cell clones of MSCA showed a higher proliferation rate and greater differentiation potential than their original cells. However, original MSCB cells were of greater proliferation and differentiation potential than their derived single-cell clones, except for one clone which had comparable results. Cloning of MSCs was attainable when cultured in mouse embryonic fibroblast conditioned media. Single clones with higher proliferation and differentiation potential than their original progenitor cells were obtained by cloning of poorly functioning MSCs progenitor cells, enabling the selection of more therapeutically efficacious MSCs with better performance in clinical applications. Moreover, this study draws attention to the importance of CD105 as a possible MSCs biomarker associated with the multilineage commitment of MSCs.

Comprehensive Evaluation of a Quantitative Shotgun Lipidomics Platform for Mammalian Sample Analysis on a High-Resolution Mass Spectrometer

Shotgun lipidomics is a powerful tool that enables simultaneous and fast quantification of diverse lipid classes through mass spectrometry based analyses of directly infused crude lipid extracts. We present here a shotgun lipidomics platform established to quantify 38 lipid classes belonging to four lipid categories present in mammalian samples and show the fine-tuning and comprehensive evaluation of its experimental parameters and performance. We first determined for all the targeted lipid classes the collision energy levels optimal for the recording of their lipid class- and species-specific fragment ions and fine-tuned the energy levels applied in the platform. We then performed a series of titrations to define the boundaries of linear signal response for the targeted lipid classes, and demonstrated that the dynamic quantification range spanned more than 3 orders of magnitude and reached sub picomole levels for 35 lipid classes. The platform identified 273, 261, and 287 lipid species in brain, plasma, and cultured fibroblast samples, respectively, at the respective optimal working sample amounts. The platform properly quantified the majority of these identified lipid species, while lipid species measured to be below the limit of quantification were efficiently removed from the data sets by the use of statistical analyses of data reproducibility or a cutoff threshold. Finally, we demonstrated that a series of parameters of cell culture conditions influence lipidomics outcomes, including confluency, medium supplements, and use of transfection reagents. The present study provides a guideline for setting up and using a simple and efficient platform for quantitatively exploring the mammalian lipidome.

The Influence of Cell Culture Density on the Cytotoxicity of Adipose-Derived Stem Cells Induced by L-Ascorbic Acid-2-Phosphate

Ascorbic acid-2-phosphate (A2-P) is an oxidation-resistant derivative of ascorbic acid that has been widely employed in culturing adipose-derived stem cells (ASCs) for faster expansion and cell sheet formation. While high dose ascorbic acid is known to induce cellular apoptosis via metabolic stress and genotoxic effects, potential cytotoxic effects of A2-P at high concentrations has not been explored. In this study, the relationship between ASC seeding density and A2-P-induced cytotoxicity was investigated. Spheroid-derived ASCs with smaller cellular dimensions were generated to investigate the effect of cell-cell contact on the resistance to A2-P-induced cytotoxicity. Decreased viability of ASC, fibroblast, and spheroid-derived ASC was noted at higher A2-P concentration, and it could be reverted with high seeding density. Compared to control ASCs, spheroid-derived ASCs seeded at the same density exhibited decreased viability in the A2-P-supplemented medium. The expression of antioxidant enzymes (catalase, SOD1, and SOD2) was enhanced in ASCs at higher seeding densities. However, their enhanced expression in spheroid-derived ASCs was less evident. Furthermore, we found that co-administration of catalase or N-acetylcysteine nullified the observed cytotoxicity. Collectively, A2-P can induce ASC cytotoxicity at higher concentrations, which can be prevented by seeding ASCs at high density or co-administration of another antioxidant.

Applications of single cell RNA sequencing to research of stem cells

Stem cells (SCs) with their self-renewal and pluripotent differentiation potential, show great promise for therapeutic applications to some refractory diseases such as stroke, Parkinsonism, myocardial infarction, and diabetes. Furthermore, as seed cells in tissue engineering, SCs have been applied widely to tissue and organ regeneration. However, previous studies have shown that SCs are heterogeneous and consist of many cell subpopulations. Owing to this heterogeneity of cell states, gene expression is highly diverse between cells even within a single tissue, making precise identification and analysis of biological properties difficult, which hinders their further research and applications. Therefore, a defined understanding of the heterogeneity is a key to research of SCs. Traditional ensemble-based sequencing approaches, such as microarrays, reflect an average of expression levels across a large population, which overlook unique biological behaviors of individual cells, conceal cell-to-cell variations, and cannot understand the heterogeneity of SCs radically. The development of high throughput single cell RNA sequencing (scRNA-seq) has provided a new research tool in biology, ranging from identification of novel cell types and exploration of cell markers to the analysis of gene expression and predicating developmental trajectories. scRNA-seq has profoundly changed our understanding of a series of biological phenomena. Currently, it has been used in research of SCs in many fields, particularly for the research of heterogeneity and cell subpopulations in early embryonic development. In this review, we focus on the scRNA-seq technique and its applications to research of SCs.

Non-thermal atmospheric pressure plasma is an excellent tool to activate proliferation in various mesoderm-derived human adult stem cells

Adult stem cells are capable of self-renewal and differentiation into specific cell types in tissues and have high potential for stem cell therapy. Mesenchymal and hematopoietic stem cells are easily attainable from the human body and have become applicable tools for adult stem cell therapy. However, there are still technical barriers for the application of mesenchymal and hematopoietic stem cells for therapy, such as the small number of cell populations, high risk of contamination, and loss of their stemness properties in vitro. In our previous study, we showed that non-thermal atmospheric pressure plasma (NTAPP) promoted the proliferation of adipose tissue-derived stem cells (ASCs) by 1.6-fold on average, while maintaining their stemness. Here, we examined the feasibility of NTAPP as a tool to activate the proliferation of mesenchymal and hematopoietic stem cells in vitro without affecting their stem cell characteristics. NTAPP increased the proliferation of bone marrow-derived stem cells (BM-MSCs) and hematopoietic stem cells (HSCs) by 1.8- and 2-fold, respectively, when compared to that of untreated cells. As observed in ASCs, NTAPP exposure also activated the expression of stem cell-specific surface markers, CD44 and CD105, by 5-fold in BM-MSCs, when compared to that in unexposed control cells in a low glucose medium with a low concentration of basic fibroblast growth factor (b-FGF). In addition, NTAPP exposure highly augmented the mRNA expression of well-known pluripotent genes for stemness, such as Oct4, Sox2, and Nanog in ASCs and BM-MSCs when compared to that in unexposed control cells. When cell cycle progression was examined, the G1-S shift was accelerated, and expression of PCNA was increased in NTAPP-exposed ASCs when compared to that in untreated control cells, suggesting that NTAPP activated G1-S transition. Taken together, these results demonstrated that NTAPP activated the proliferation of various mesodermal-derived human adult stem cells by accelerating the G1-S transition while maintaining their pluripotency and stemness, strongly suggesting that NTAPP can be an efficient tool for expanding the population of various adult stem cells in vitro for medical applications.

Study of diffusive- and convective-transport mediated microtumor growth in a controlled microchamber

In this paper, we report on using mass transport to control nutrition supply of colorectal cancer cells for developing a microtumor in a confined microchamber. To mimic the spatial heterogeneity of a tumor, two microfluidic configurations based on resistive circuits are designed. One has a convection-dominated microchamber to simulate the tumor region proximal to leaky blood vessels. The other has a diffusion-dominated microchamber to mimic the tumor core that lacks blood vessels and nutrient supply. Thus, the time for nutrition to fill the microchamber can vary from tens of minutes to several hours. Results show that cells cultured under a diffusive supply of nutrition have a high glycolytic rate and a nearly constant oxygen consumption rate. In contrast, cells cultured under convective supply of nutrition have a gradual increase of oxygen consumption rate with a low glycolytic rate. This suggests that cancer cells have distinct reactions under different mass transport and nutrition supply. Using these two microfluidic platforms to create different rate of nutrition supply, it is found that a continuous microtumor that almost fills the mm-size microchamber can be developed under a low-nutrient supply environment, but not for the convective condition. It also is demonstrated that microchannels can simulate the delivery of anti-cancer drugs to the microtumor under controlled mass-transport. This method provides a means to develop a larger scale microtumor in a lab-on-a-Chip system for post development and stimulations, and microchannels can be applied to control the physical and chemical environment for anti-cancer drug screening.

Aldehyde Dehydrogenase Activity in Adipose Tissue: Isolation and Gene Expression Profile of Distinct Sub-population of Mesenchymal Stromal Cells

Thanks to their relative abundance and easier collection, adipose tissue (AT) is considered an alternative source for the isolation of mesenchymal stromal cells (MSCs). MSCs have great therapeutic values and are thus under investigations for several clinical indications such as regenerative medicine and immunomodulation. In this work, we aimed to identify, isolate and characterize AT-MSCs based on their aldehyde dehydrogenase (ALDH) activity known to be a classical feature of stem cells. FACS technology allowed to isolate two different populations of AT-MSCs according to their ALDH activity (referred as ALDH⁺ and ALDH^-). Depending on their ALDH activity, the transcriptome analysis of both cell populations demonstrated a differential pattern of genes related to the main properties of MSCs (proliferation, response to hypoxia, angiogenesis, phenotype, stemness, multilineage, hematopoiesis, immunomodulation). Based on these profiling, both AT-MSC populations could differ in terms of biological responses and functionalities. Collectively, the use of ALDH for isolating and identifying sub-populations of MSCs with specific gene profile may represent an alternative method to provide solutions for targeted therapeutic applications.

The Impact of Epigenetic Signatures on Amniotic Fluid Stem Cell Fate

Epigenetic modifications play a significant role in determining the fate of stem cells and in directing the differentiation into multiple lineages. Current evidence indicates that mechanisms involved in chromatin regulation are essential for maintaining stable cell identities. There is a tight correlation among DNA methylation, histone modifications, and small noncoding RNAs during the epigenetic control of stem cells' differentiation; however, to date, the precise mechanism is still not clear. In this context, amniotic fluid stem cells (AFSCs) represent an interesting model due to their unique features and the possible advantages of their use in regenerative medicine. Recent studies have elucidated epigenetic profiles involved in AFSCs' lineage commitment and differentiation. In order to use these cells effectively for therapeutic purposes, it is necessary to understand the basis of multiple-lineage potential and elaborate in detail how cell fate decisions are made and memorized. The present review summarizes the most recent findings on epigenetic mechanisms of AFSCs with a focus on DNA methylation, histone modifications, and microRNAs (miRNAs) and addresses how their unique signatures contribute to lineage-specific differentiation.

MicroRNA-532-5p Regulates Pericyte Function by Targeting the Transcription Regulator BACH1 and Angiopoietin-1

MicroRNAs regulate endothelial function and angiogenesis, but their implication in pericyte biology remains undetermined. A PCR array, covering a panel of 379 human microRNAs, showed microRNA-532-5p to be one of the most differentially modulated by hypoxia, which was confirmed by qPCR in both skeletal muscle and adventitial pericytes. Furthermore, microRNA-532-5p was upregulated in murine muscular pericytes early after experimentally induced ischemia, decreasing below baseline after reperfusion. Transfection of human pericytes with anti-microRNA, microRNA-mimic, or controls indicates microRNA-532-5p modulates pro-angiogenic activity via transcriptional regulation of angiopoietin-1. Tie-2 blockade abrogated the ability of microRNA-532-5p-overexpressing pericytes to promote endothelial network formation in vitro. However, angiopoietin-1 is not a direct target of microRNA-532-5p. In silico analysis of microRNA-532-5p inhibitory targets associated with angiopoietin-1 transcription indicated three potential candidates, BACH1, HIF1AN, and EGLN1. Binding of microRNA-532-5p to the BACH1 3' UTR was confirmed by luciferase assay. MicroRNA-532-5p silencing increased BACH1, while a microRNA-532-5p mimic decreased expression. Silencing of BACH1 modulated angiopoietin-1 gene and protein expression. ChIP confirmed BACH1 transcriptional regulation of angiopoietin-1 promoter. Finally, microRNA-532-5p overexpression increased pericyte coverage in an in vivo Matrigel assay, suggesting its role in vascular maturation. This study provides a new mechanistic understanding of the transcriptional program orchestrating angiopoietin-1/Tie-2 signaling in human pericytes.