Phenotypic, Morphological and Adhesive Differences of Human Hematopoietic Progenitor Cells Cultured on Murine versus Human Mesenchymal Stromal Cells

Bone marrow vasculature advanced in vitro models for cancer and cardiovascular research

Cardiometabolic diseases and cancer are among the most common diseases worldwide and are a serious concern to the healthcare system. These conditions, apparently distant, share common molecular and cellular determinants, that can represent targets for preventive and therapeutic approaches. The bone marrow plays an important role in this context as it is the main source of cells involved in cardiovascular regeneration, and one of the main sites of liquid and solid tumor metastasis, both characterized by the cellular trafficking across the bone marrow vasculature. The bone marrow vasculature has been widely studied in animal models, however, it is clear the need for human-specific in vitro models, that resemble the bone vasculature lined by endothelial cells to study the molecular mechanisms governing cell trafficking. In this review, we summarized the current knowledge on in vitro models of bone marrow vasculature developed for cardiovascular and cancer research.

Human Mesenchymal Stem Cells Modified with the NS5A Gene of Hepatitis C Virus Induce a Cellular Immune Response Exceeding the Response to DNA Immunization with This Gene

Hepatitis C virus (HCV) is one of the basic culprits behind chronic liver disease, which may result in cirrhosis and hepatocarcinoma. In spite of the extensive research conducted, a vaccine against HCV has not been yet created. We have obtained human mesenchymal stem cells (hMSCs) and used them for expressing the HCV NS5A protein as a model vaccination platform. Sixteen hMSC lines of a different origin were transfected with the pcNS5A-GFP plasmid to obtain genetically modified MSCs (mMSCs). The highest efficiency was obtained by the transfection of dental pulp MSCs. C57BL/6 mice were immunized intravenously with mMSCs, and the immune response was compared with the response to the pcNS5A-GFP plasmid, which was injected intramuscularly. It was shown that the antigen-specific lymphocyte proliferation and the number of IFN-γ-synthesizing cells were two to three times higher after the mMSC immunization compared to the DNA immunization. In addition, mMSCs induced more CD4+ memory T cells and an increase in the CD4+/CD8+ ratio. The results suggest that the immunostimulatory effect of mMSCs is associated with the switch of MSCs to the pro-inflammatory phenotype and a decrease in the proportion of myeloid derived suppressor cells. Thus, the possibility of using human mMSCs for the creation of a vaccine against HCV has been shown for the first time.

Mesenchymal stromal cell-associated migrasomes: a new source of chemoattractant for cells of hematopoietic origin

BACKGROUND

Multipotent mesenchymal stromal cells (MSCs) are precursors of various cell types. Through soluble factors, direct cell-cell interactions and other intercellular communication mechanisms such as extracellular vesicles and tunneling nanotubes, MSCs support tissue homeostasis. In the bone marrow microenvironment, they promote hematopoiesis. The interaction between MSCs and cancer cells enhances the cancer and metastatic potential. Here, we have demonstrated that plastic-adherent MSCs isolated from human bone marrow generate migrasomes, a newly discovered organelle playing a role in intercellular communication.

RESULTS

Migrasomes are forming a network with retraction fibers behind the migrating MSCs or surrounding them after membrane retraction. The MSC markers, CD44, CD73, CD90, CD105 and CD166 are present on the migrasome network, the latter being specific to migrasomes. Some migrasomes harbor the late endosomal GTPase Rab7 and exosomal marker CD63 indicating the presence of multivesicular bodies. Stromal cell-derived factor 1 (SDF-1) was detected in migrasomes, suggesting that they play a chemoattractant role. Co-cultures with KG-1a leukemic cells or primary CD34⁺ hematopoietic progenitors revealed that MSC-associated migrasomes attracted them, a process intercepted by the addition of AMD3100, a specific CXCR4 receptor inhibitor, or recombinant SDF-1. An antibody directed against CD166 reduced the association of hematopoietic cells and MSC-associated migrasomes. In contrast to primary CD34⁺ progenitors, leukemic cells can take up migrasomes.

CONCLUSION

Overall, we described a novel mechanism used by MSCs to communicate with cells of hematopoietic origin and further studies are needed to decipher all biological aspects of migrasomes in the healthy and transformed bone marrow microenvironment. Video Abstract.

In vitro recellularization of decellularized bovine carotid arteries using human endothelial colony forming cells

BACKGROUND

Many patients suffering from peripheral arterial disease (PAD) are dependent on bypass surgery. However, in some patients no suitable replacements (i.e. autologous or prosthetic bypass grafts) are available. Advances have been made to develop autologous tissue engineered vascular grafts (TEVG) using endothelial colony forming cells (ECFC) obtained by peripheral blood draw in large animal trials. Clinical translation of this technique, however, still requires additional data for usability of isolated ECFC from high cardiovascular risk patients. Bovine carotid arteries (BCA) were decellularized using a combined SDS (sodium dodecyl sulfate) -free mechanical-osmotic-enzymatic-detergent approach to show the feasibility of xenogenous vessel decellularization. Decellularized BCA chips were seeded with human ECFC, isolated from a high cardiovascular risk patient group, suffering from diabetes, hypertension and/or chronic renal failure. ECFC were cultured alone or in coculture with rat or human mesenchymal stromal cells (rMSC/hMSC). Decellularized BCA chips were evaluated for biochemical, histological and mechanical properties. Successful isolation of ECFC and recellularization capabilities were analyzed by histology.

RESULTS

Decellularized BCA showed retained extracellular matrix (ECM) composition and mechanical properties upon cell removal. Isolation of ECFC from the intended target group was successfully performed (80% isolation efficiency). Isolated cells showed a typical ECFC-phenotype. Upon recellularization, co-seeding of patient-isolated ECFC with rMSC/hMSC and further incubation was successful for 14 (n = 9) and 23 (n = 5) days. Reendothelialization (rMSC) and partial reendothelialization (hMSC) was achieved. Seeded cells were CD31 and vWF positive, however, human cells were detectable for up to 14 days in xenogenic cell-culture only. Seeding of ECFC without rMSC was not successful.

CONCLUSION

Using our refined decellularization process we generated easily obtainable TEVG with retained ECM- and mechanical quality, serving as a platform to develop small-diameter (< 6 mm) TEVG. ECFC isolation from the cardiovascular risk target group is possible and sufficient. Survival of diabetic ECFC appears to be highly dependent on perivascular support by rMSC/hMSC under static conditions. ECFC survival was limited to 14 days post seeding.

RNA-seq reveals tight junction-relevant erythropoietic fate induced by OCT4 in human hair follicle mesenchymal stem cells

BACKGROUND

Human hair follicle mesenchymal stem cells (hHFMSCs) isolated from hair follicles possess multilineage differentiation potential. OCT4 is a gene critically associated with pluripotency properties. The cell morphology and adhesion of hHFMSCs significantly changed after transduction of OCT4 and two subpopulations emerged, including adherent cells and floating cell. Floating cells cultured in hematopoietic induction medium and stimulated with erythropoetic growth factors could transdifferentiate into mature erythrocytes, whereas adherent cells formed negligible hematopoietic colonies. The aim of this study was to reveal the role of cell morphology and adhesion on erythropoiesis induced by OCT4 in hHFMSCs and to characterize the molecular mechanisms involved.

METHODS

Floating cell was separated from adherent cell by centrifugation of the upper medium during cell culture. Cell size was observed through flow cytometry and cell adhesion was tested by disassociation and adhesion assays. RNA sequencing was performed to detect genome-wide transcriptomes and identify differentially expressed genes. GO enrichment analysis and KEGG pathway analysis were performed to analysis the functions and pathways enriched by differentially expressed genes. The expression of tight junction core members was verified by qPCR and Western blot. A regulatory network was constructed to figure out the relationship between cell adhesin, cytoskeleton, pluripotency, and hematopoiesis.

RESULTS

The overexpression of OCT4 influenced the morphology and adhesion of hHFMSCs. Transcripts in floating cells and adherent cells are quite different. Data analysis showed that upregulated genes in floating cells were mainly related to pluripotency, germ layer development (including hematopoiesis lineage development), and downregulated genes were mainly related to cell adhesion, cell junctions, and the cytoskeleton. Most molecules of the tight junction (TJ) pathway were downregulated and molecular homeostasis of the TJ was disturbed, as CLDNs were disrupted, and JAMs and TJPs were upregulated. The dynamic expression of cell adhesion-related gene E-cadherin and cytoskeleton-related gene ACTN2 might cause different morphology and adhesion. Finally, a regulatory network centered to OCT4 was constructed, which elucidated that he TJ pathway critically bridges pluripotency and hematopoiesis in a TJP1-dependent way.

CONCLUSIONS

Regulations of cell morphology and adhesion via the TJ pathway conducted by OCT4 might modulate hematopoiesis in hHFMSCs, thus developing potential mechanism of erythropoiesis in vitro.

Physiological Cues Involved in the Regulation of Adhesion Mechanisms in Hematopoietic Stem Cell Fate Decision

Hematopoietic stem cells (HSC) could have several fates in the body; viz. self-renewal, differentiation, migration, quiescence, and apoptosis. These fate decisions play a crucial role in maintaining homeostasis and critically depend on the interaction of the HSCs with their micro-environmental constituents. However, the physiological cues promoting these interactions in vivo have not been identified to a great extent. Intense research using various in vitro and in vivo models is going on in various laboratories to understand the mechanisms involved in these interactions, as understanding of these mechanistic would greatly help in improving clinical transplantations. However, though these elegant studies have identified the molecular interactions involved in the process, harnessing these interactions to the recipients' benefit would ultimately depend on manipulation of environmental cues initiating them in vivo: hence, these need to be identified at the earliest. HSCs reside in the bone marrow, which is a very complex tissue comprising of various types of stromal cells along with their secreted cytokines, extra-cellular matrix (ECM) molecules and extra-cellular vesicles (EVs). These components control the HSC fate decision through direct cell-cell interactions - mediated via various types of adhesion molecules -, cell-ECM interactions - mediated mostly via integrins -, or through soluble mediators like cytokines and EVs. This could be a very dynamic process involving multiple transient interactions acting concurrently or sequentially, and the adhesion molecules involved in various fate determining situations could be different. If the switch mechanisms governing these dynamic states in vivo are identified, they could be harnessed for the development of novel therapeutics. Here, in addition to reviewing the adhesion molecules involved in the regulation of HSCs, we also touch upon recent advances in our understanding of the physiological cues known to initiate specific adhesive interactions of HSCs with the marrow stromal cells or ECM molecules and EVs secreted by them.

Generation of Organotypic Multicellular Spheres by Magnetic Levitation: Model for the Study of Human Hematopoietic Stem Cells Microenvironment

Background and Objective

The characteristics of human hematopoietic stem cells are conditioned by the microenvironment of the bone marrow, where they interact with other cell populations, such as mesenchymal stem cells and endothelial cells; however, the study of this microenvironment is complex. The objective of this work was to develop a 3D culture system by magnetic levitation that imitates the microenvironment of human HSC.

Methods and Results

Human bone marrow-mesenchymal stem cells, umbilical cord blood-hematopoietic stem cells and a non-tumoral endothelial cell line (CC2811, Lonza^Ⓡ) were used to develop organotypic multicellular spheres by the magnetic levitation method. We obtained viable structures with an average sphericity index greater than 0.6, an average volume of 0.5 mm³ and a percentage of aggregation greater than 70%. Histological studies of the organotypic multicellular spheres used hematoxylin and eosin stains, and an evaluation of vimentin expression by means of immunohistochemistry demonstrated an organized internal structure without picnotic cells and a high expression of vimentin. The functional capacity of human hematopoietic stem cells after organotypic multicellular spheres culture was evaluated by multipotency tests, and it was demonstrated that 3D structures without exogenous Flt3L are autonomous in the maintenance of multipotency of human hematopoietic stem cells.

Conclusions

We developed organotypic multicellular spheres from normal human cells that mimic the microenvironment of the human hematopoietic stem cells. These structures are the prototype for the development of complex organoids that allow the further study of the biology of normal human stem cells and their potential in regenerative medicine.

Mesenchymal stromal cells prevent progression of liver fibrosis in a novel zebrafish embryo model

Chronic liver damage leads to the onset of fibrogenesis. Rodent models for liver fibrosis have been widely used, but are less suitable for screening purposes. Therefore the aim of our study was to design a novel model for liver fibrosis in zebrafish embryos, suitable for high throughput screening. Furthermore, we evaluated the efficacy of mesenchymal stromal cells (MSCs) to inhibit the fibrotic process and thereby the applicability of this model to evaluate therapeutic responses. Zebrafish embryos were exposed to TAA or CCL4 and mRNA levels of fibrosis-related genes (Collagen-1α1, Hand-2, and Acta-2) and tissue damage-related genes (TGF-β and SDF-1a, SDF-1b) were determined, while Sirius-red staining was used to estimate collagen deposition. Three days after start of TAA exposure, MSCs were injected after which the fibrotic response was determined. In contrast to CCL4, TAA resulted in an upregulation of the fibrosis-related genes, increased extracellular matrix deposition and decreased liver sizes suggesting the onset of fibrosis. The applicability of this model to evaluate therapeutic responses was shown by local treatment with MSCs which resulted in decreased expression of the fibrosis-related RNA markers. In conclusion, TAA induces liver fibrosis in zebrafish embryos, thereby providing a promising model for future mechanistic and therapeutic studies.

Microgrooved-surface topography enhances cellular division and proliferation of mouse bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells’ (MSCs) fate is largely determined by the various topographical features and a range of extracellular matrix (ECM) components present in their niches. Apart from maintaining structural stability, they regulate cell morphology, division, proliferation, migration and differentiation among others. Traditional MSC cultures, which are mainly based on two-dimensional smooth surfaces of culture dishes and plates, do not provide topographical cues similar to in vivo three-dimensional niches, impacting various cellular processes. Therefore, we culture the mouse bone marrow-derived MSCs on microgrooved bearing surface, partially mimicking in vivo reticulated niche, to study its effect on morphology, pluripotency factor-associated stemness, cell division and rate of proliferation. Following culture, morphological features, and MSC-specific marker gene expression, such as CD29, CD44, Sca-1 along with HSC (Haematopoietic stem cell)-specific markers like CD34, CD45, CD11b were evaluated by microscopy and immunophenotyping, respectively. HSC is another type of bone marrow stem cell population, which concertedly interacts with MSC during various functions, including haematopoiesis. In addition, mesenchymal stem cells were further analyzed for gene expression of pluripotency-associated transcription factors such as Oct3/4, Sox-2, Nanog and Myc, as well as differentiated into adipocytes, osteocytes and chondrocytes. Our results show that microgrooved surface-cultured mesenchymal stem cells (MMSCs) expressed higher levels of expected cell surface and pluripotency-associated markers and proliferated more rapidly (2–3×fold) with higher percentage of cells in S/G2-M-phase, consequently giving rise to higher cell yield compared to standard culture flask-grown cells (MSCs), taken as control. Furthermore, both MSCs and MMSCs showed considerable accumulation of intracellular lipid-droplets, higher alkaline phosphatase activity and secretion of extracellular matrix that are characteristics of adipogenesis, osteogenesis and chondrogenesis, respectively.

Bone marrow niche-mimetics modulate HSPC function via integrin signaling

The bone marrow (BM) microenvironment provides critical physical cues for hematopoietic stem and progenitor cell (HSPC) maintenance and fate decision mediated by cell-matrix interactions. However, the mechanisms underlying matrix communication and signal transduction are less well understood. Contrary, stem cell culture is mainly facilitated in suspension cultures. Here, we used bone marrow-mimetic decellularized extracellular matrix (ECM) scaffolds derived from mesenchymal stromal cells (MSCs) to study HSPC-ECM interaction. Seeding freshly isolated HSPCs adherent (AT) and non-adherent (SN) cells were found. We detected enhanced expansion and active migration of AT-cells mediated by ECM incorporated stromal derived factor one. Probing cell mechanics, AT-cells displayed naïve cell deformation compared to SN-cells indicating physical recognition of ECM material properties by focal adhesion. Integrin αIIb (CD41), αV (CD51) and β3 (CD61) were found to be induced. Signaling focal contacts via ITGβ3 were identified to facilitate cell adhesion, migration and mediate ECM-physical cues to modulate HSPC function.

Comparison of fluorescence-based methods to determine nanoparticle uptake by phagocytes and non-phagocytic cells in vitro

At many portals of entry the relative uptake by phagocytes and non-phagocytic cells has a prominent effect on availability and biological action of nanoparticles (NPs). Cellular uptake can be determined for fluorescence-labeled NPs. The present study compares three methods (plate reader, flow cytometry and image analysis) in order to investigate the influence of particle size and functionalization and medium content on cellular uptake of fluorescence–labeled polystyrene particles and to study the respective method’s suitability for uptake studies. For comparison between the techniques, ratios of macrophage to alveolar epithelial cell uptakes were used. Presence of serum protein in the exposure solution decreased uptake of carboxyl-functionalized and non-functionalized particles; there was no clear effect for the amine-functionalized particles. The 200 nm non- or carboxyl-functionalized NPs were taken up preferentially by phagocytes while for amine-functionalized particles preference was lowest. The presence of the serum slightly increased the preference for these particles.

In conclusion, due to the possibility of calibration, plate reader measurements might present a better option than the other techniques to (semi)quantify differences between phagocytes and non-phagocytic cells for particles with different fluorescence. In order to obtain unbiased data the fluorescent labeling has to fulfill certain requirements.