Establishment and characterization of fetal and maternal mesenchymal stem/stromal cell lines from the human term placenta

A study on the production of extracellular vesicles derived from novel immortalized human placental mesenchymal stromal cells

Extracellular vesicles (EVs) are not only involved in cell-to-cell communications but have other functions as "garbage bags", as bringing nutrients to cells, and as inducing mineral during bone formation and ectopic calcification. These minuscule entities significantly contribute to the regulation of bodily functions. However, the clinical application of EVs faces challenges due to limited production yield and targeting efficiency. In our study, we propose a method for efficiently harvesting EVs utilizing simian virus 40 large T antigen (SV40LT) immortalized human placental chorionic mesenchymal stromal cells (CMSCs). We investigated immortalized placental chorionic mesenchymal stromal cells (imCMSCs), a stromal cell line that surpasses the growth limitations of primary passage cells while retaining phenotypic characteristics and differentiation potential. This development offers the prospect of a consistent, uniform source of EVs, which is essential for regenerative medicine. Our findings indicate that the immortalization process preserves the particle size, quantity and surface marker profiles of EVs, providing a possible approach to produce high-yield EVs suitable for disease diagnosis and treatment.

Profiling the extracellular vesicles of two human placenta-derived mesenchymal stromal cell populations

Increasing evidence shows extracellular vesicles (EVs) are primarily responsible for the beneficial effects of cell-based therapies. EVs derived from mesenchymal stromal cells (MSCs) show promise as a source of EVs for cell-free therapies. The human placental fetal-maternal interface is a rich and abundant source of MSCs from which EVs can be isolated. This study focusses on chorionic MSCs (CMSC) located on the fetal aspect of the interface and decidual MSCs (DMSC) on the maternal aspect. This study used Ligand-based Exosome Affinity Purification (LEAP) chromatography to isolate EVs from well-characterized placental hTERT-transduced CMSC29 and DMSC23 cell lines, which retain many important stem cell-like properties of primary CMSC and DMSC, respectively. After initial biophysical characterization of the EVs isolated from each cell line, the biological activities and the protein, lipid and small RNA contents of CMSC29-EVs and DMSC23-EVs were compared and assessed. LEAP-purified EVs from both sources were validated at the biophysical level by Spectradyne, Cryo-Transmission Electron Microscopy (Cryo-TEM), and Western blot analysis. EVs from each type were labelled with the live cell stain PKH26 and their in vitro uptake and internalization by human dermal fibroblast cells was assessed, as well as their phosphorylation of the protein kinase B/AKT (AKT) pathway. The protein and lipid contents were analyzed by mass spectrometry and the nucleic acid content by RNA sequencing (RNA-seq). Lastly, the biological activities of the EVs were evaluated in a BioMAP® Diversity PLUS® screen system across a panel of 12 human primary cell-based systems and in vitro cell proliferation. EVs isolated from both DMSC23 and CMSC29 significantly increased proliferation of fibroblasts and showed phosphorylation of the AKT pathway. Protein mass spectrometry analysis identified a large number of proteins including cell surface receptors, cytokines, chemokines, matrix molecules and enzymes in both EV types. Lipidomic analysis identified species including phosphatidylcholine, triacylglycerides and diacylglycerides in both DMSC23 and CMSC29-derived EVs. There were some significant differences in identified microRNAs (miRNAs) between the two EV types. The top differentially expressed miRNAs between the two EV types show pathways association with matrix interaction, transcriptional regulation, proliferation, cellular protein modification processes, and vasculogenesis. Differences were also detected between DMSC23- and CMSC29-EVs in the biological activity they displayed in the BioMAP® Diversity PLUS® screen.

Immortalized mammosphere-derived epithelial cells retain a bioactive secretome with antimicrobial, regenerative, and immunomodulatory properties

BACKGROUND

The secretome of primary bovine mammosphere-derived epithelial cells (MDECs) has been shown to exert antimicrobial, regenerative, and immunomodulatory properties in vitro, which warrants its study as a potential biologic treatment with the potential to be translated to human medicine. Currently, the use of the MDEC secretome as a therapy is constrained by the limited life span of primary cell cultures and the decrease of secretome potency over cell passages.

METHODS

To address these limitations, early-passage bovine MDECs were immortalized using hTERT, a human telomerase reverse transcriptase. The primary and immortal MDECs were compared morphologically, transcriptomically, and phenotypically. The functional properties and proteomic profiles of the secretome of both cell lines were evaluated and compared. All experiments were performed with both low and high passage cell cultures.

RESULTS

We confirmed through in vitro experiments that the secretome of immortalized MDECs, unlike that of primary cells, maintained antimicrobial and pro-migratory properties over passages, while pro-angiogenic effects of the secretome from both primary and immortalized MDECs were lost when the cells reached high passage. The secretome from primary and immortalized MDECs, at low and high passages exerted immunomodulatory effects on neutrophils in vitro.

CONCLUSIONS

High passage immortalized MDECs retain a bioactive secretome with antimicrobial, regenerative, and immunomodulatory properties, suggesting they may serve as a consistent cell source for therapeutic use.

Metals in nanomotion: probing the role of extracellular vesicles in intercellular metal transfer

Metals in living organisms and environments are essential for key biological functions such as enzymatic activity, and DNA and RNA synthesis. This means that disruption of metal ion homeostasis and exchange between cells can lead to diseases. EVs are believed to play an essential role in transporting metals between cells, but the mechanism of metal packaging and exchange remains to be elucidated. Here, we established the elemental composition of EVs at the nanoscale and single-vesicle level and showed that the metal content depends on the cell type and culture microenvironment. We also demonstrated that EVs participate in the exchange of metal elements between cells. Specifically, we used two classes of EVs derived from papaya fermented fluid (PaEVs), and decidual mesenchymal stem/stromal cells (DEVs). To show that EVs transfer metal elements to cells, we treated human osteoblast-like cells (MG63) and bone marrow mesenchymal stem cells (BMMSCs) with both classes of EVs. We found that both classes of EVs contained various metal elements, such as Ca, P, Mg, Fe, Na, Zn, and K, originating from their parent cells, but their relative concentrations did not mirror the ones found in the parent cells. Single-particle analysis of P, Ca, and Fe in DEVs and PaEVs revealed varying element masses. Assuming spherical geometry, the mean mass of P was converted to a mean size of 62 nm in DEVs and 24 nm in PaEVs, while the mean sizes of Ca and Fe in DEVs were smaller, converting to 20 nm and 30 nm respectively. When EVs interacted with BMMSCs and MG63, DEVs increased Ca, P, and Fe concentrations in BMMSCs and increased Fe concentration in MG63, while PaEVs increased Ca concentrations in BMMSCs and had no effect on MG63. The EV cargo, including proteins, nucleic acids, and lipids, differs from their origin in composition, and this variation extends to the element composition of EVs in our study. This fundamental understanding of EV-mediated metal exchange between cells could offer a new way of assessing EV functionality by measuring their elemental composition. Additionally, it will contribute novel insights into the mechanisms underlying EV production and their biological activity.

The other side of the coin: mesenchymal stromal cell immortalization beyond evasion of senescence

Mesenchymal stromal cells (MSC) are promising options to cellular therapy to several clinical disorders, mainly because of its ability to immunomodulate and differentiate into different cell types. Even though MSC can be isolated from different sources, a major challenge to understanding the biological effects is that the primary cells undergo replicative senescence after a limited number of cell divisions in culture, requiring time-consuming and technically challenging approaches to get a sufficient cell number for clinical applications. Therefore, a new isolation, characterization, and expansion is necessary every time, which increases the variability and is time-consuming. Immortalization is a strategy that can overcome these challenges. Therefore, here, we review the different methodologies available to cellular immortalization, and discuss the literature regarding MSC immortalization and the broader biological consequences that extend beyond the mere increase in proliferation potential.

Cell Immortalization: In Vivo Molecular Bases and In Vitro Techniques for Obtention

Somatic human cells can divide a finite number of times, a phenomenon known as the Hayflick limit. It is based on the progressive erosion of the telomeric ends each time the cell completes a replicative cycle. Given this problem, researchers need cell lines that do not enter the senescence phase after a certain number of divisions. In this way, more lasting studies can be carried out over time and avoid the tedious work involved in performing cell passes to fresh media. However, some cells have a high replicative potential, such as embryonic stem cells and cancer cells. To accomplish this, these cells express the enzyme telomerase or activate the mechanisms of alternative telomere elongation, which favors the maintenance of the length of their stable telomeres. Researchers have been able to develop cell immortalization technology by studying the cellular and molecular bases of both mechanisms and the genes involved in the control of the cell cycle. Through it, cells with infinite replicative capacity are obtained. To obtain them, viral oncogenes/oncoproteins, myc genes, ectopic expression of telomerase, and the manipulation of genes that regulate the cell cycle, such as p53 and Rb, have been used.

Decidual mesenchymal stem/stromal cells from preeclamptic patients secrete endoglin, which at high levels inhibits endothelial cell attachment invitro

INTRODUCTION

In preeclampsia (PE), inadequate remodelling of spiral arterioles in the decidua basalis causes oxidative stress and subsequent increased release of antiangiogenic soluble endoglin (sENG) into the maternal circulation. Decidual mesenchymal stem/stromal cells (DMSCs) reside adjacent to endothelial cells in this vascular niche. Surprisingly, DMSCs express membrane-bound ENG (CD105). PE-affected DMSCs (PE-DMSCs) are abnormal and due to reduced extravillous invasion, more of them are present, but the significance of this is not known.

METHODS

DMSCs were isolated and characterised from normotensive control and severe-PE placentae. Extracellular vesicle (EV) types, shed microvesicles (sMV) and exosomes, were isolated from DMSC conditioned media (DMSC_CM), respectively. Secretion of ENG by DMSCs was assessed by ELISA of DMSC_CM, with and without EV depletion. The effects of reducing ENG concentration, by blocking antibody, on human umbilical vein endothelial cell (HUVEC) attachment were assessed by xCELLigence real-time functional assays.

RESULTS

ENG was detected in DMSC_CM and these levels significantly decreased when depleted of exosomes and sMV. There was no significant difference in the amount of ENG secreted by control DMSCs and PE-DMSCs. Blocking ENG in concentrated DMSC_CM, used to treat HUVECs, improved endothelial cell attachment.

DISCUSSION

In normotensive pregnancies, DMSC secretion of ENG likely has a beneficial effect on endothelial cells. However, in PE pregnancies, shallow invasion of the spiral arterioles exposes more PE-DMSC derived sources of ENG (soluble and EV). The presence of these PE-DMSCs in the vascular niche contributes to endothelial cell dysfunction.

Single-cell transcriptional profiling reveals cellular and molecular divergence in human maternal-fetal interface

Placenta plays essential role in successful pregnancy, as the most important organ connecting and interplaying between mother and fetus. However, the cellular characteristics and molecular interaction of cell populations within the fetomaternal interface is still poorly understood. Here, we surveyed the single-cell transcriptomic landscape of human full-term placenta and revealed the heterogeneity of cytotrophoblast cell (CTB) and stromal cell (STR) with the fetal/maternal origin consecutively localized from fetal section (FS), middle section (Mid_S) to maternal section (Mat_S) of maternal–fetal interface. Then, we highlighted a subpopulation of CTB, named trophoblast progenitor-like cells (TPLCs) existed in the full-term placenta and mainly distributed in Mid_S, with high expression of a pool of putative cell surface markers. Further, we revealed the putative key transcription factor PRDM6 that might promote the differentiation of endovascular extravillous trophoblast cells (enEVT) by inhibiting cell proliferation, and down-regulation of PRDM6 might lead to an abnormal enEVT differentiation process in PE. Together, our study offers important resources for better understanding of human placenta and stem cell-based therapy, and provides new insights on the study of tissue heterogeneity, the clinical prevention and control of PE as well as the maternal–fetal interface.

Mesenchymal Stem/Stromal Cells and Their Role in Oxidative Stress Associated with Preeclampsia

Preeclampsia (PE) is a serious medically important disorder of human pregnancy, which features de novo pregnancy-induced hypertension and proteinuria. The severe form of PE can progress to eclampsia, a convulsive, life-threatening condition. When placental growth and perfusion are abnormal, the placenta experiences oxidative stress and subsequently secretes abnormal amounts of certain pro-angiogenic factors (eg, PlGF) as well as anti-angiogenic factors (eg, sFlt-1) that enter the maternal circulation. The net effect is damage to the maternal vascular endothelium, which subsequently manifests as the clinical features of PE. Other than delivery of the fetus and placenta, curative treatments for PE have not yet been forthcoming, which reflects the complexity of the clinical syndrome. A major source of reactive oxygen species that contributes to the widespread maternal vascular endothelium damage is the PE-affected decidua. The role of decidua-derived mesenchymal stem/stromal cells (MSC) in normotensive and pathological placenta development is poorly understood. The ability to respond to an environment of oxidative damage is a "universal property" of MSC but the biological mechanisms that MSC employ in response to oxidative stress are compromised in PE. In this review, we discuss how MSC respond to oxidative stress in normotensive and pathological conditions. We also consider the possibility of manipulating the oxidative stress response of abnormal MSC as a therapeutic strategy to treat preeclampsia.

Improvement of Mesenchymal Stromal Cell Proliferation and Differentiation via Decellularized Extracellular Matrix on Substrates With a Range of Surface Chemistries

Decellularized extracellular matrix (dECM) deposited by mesenchymal stromal cells (MSCs) has emerged as a promising substrate for improved expansion of MSCs. To date, essentially all studies that have produced dECM for MSC expansion have done so on tissue culture plastic or glass. However, substrate surface chemistry has a profound impact on the adsorption of proteins that mediate cell-material interactions, and different surface chemistries can cause changes in cell behavior, ECM deposition, and the in vivo response to a material. This study tested the hypothesis that substrate surface chemistry impacts the deposition of ECM and its subsequent bioactivity. This hypothesis was tested by producing glass surfaces with various surface chemistries (amine, carboxylic acid, propyl, and octyl groups) using silane chemistry. ECM was deposited by an immortalized MSC line, decellularized, and characterized through SDS-PAGE and immunofluorescence microscopy. No significant difference was observed in dECM composition or microarchitecture on the different surfaces. The decellularized surfaces were seeded with primary MSCs and their proliferation and differentiation were assessed. The presence of dECM improved the proliferation of primary MSCs by ~100% in comparison to surface chemistry controls. Additionally, the adipogenesis increased by 50–90% on all dECM surfaces in comparison to surface chemistry controls, and the osteogenesis increased by ~50% on the octyl-modified surfaces when dECM was present. However, no statistically significant differences were observed within the set of dECM surfaces or control surfaces. These results support the null hypothesis, meaning surface chemistry (over the range tested in this work) is not a key regulator of the composition or bioactivity of MSC-derived dECM. These results are significant because they provide an important insight into regenerative engineering technologies. Specifically, the utilization of dECM in stem cell manufacturing and tissue engineering applications would require the dECM to be produced on a wide variety of substrates. This work indicates that it can be produced on materials with a range of surface chemistries without undesired changes in the bioactivity of the dECM.

Generation of Mesenchymal Cell Lines Derived from Aged Donors

Background: Mesenchymal stromal cells (MSCs) have the capacity for self-renewal and multi-differentiation, and for this reason they are considered a potential cellular source in regenerative medicine of cartilage and bone. However, research on this field is impaired by the predisposition of primary MSCs to senescence during culture expansion. Therefore, the aim of this study was to generate and characterize immortalized MSC (iMSC) lines from aged donors. Methods: Primary MSCs were immortalized by transduction of simian virus 40 large T antigen (SV40LT) and human telomerase reverse transcriptase (hTERT). Proliferation, senescence, phenotype and multi-differentiation potential of the resulting iMSC lines were analyzed. Results: MSCs proliferate faster than primary MSCs, overcome senescence and are phenotypically similar to primary MSCs. Nevertheless, their multi-differentiation potential is unbalanced towards the osteogenic lineage. There are no clear differences between osteoarthritis (OA) and non-OA iMSCs in terms of proliferation, senescence, phenotype or differentiation potential. Conclusions: Primary MSCs obtained from elderly patients can be immortalized by transduction of SV40LT and hTERT. The high osteogenic potential of iMSCs converts them into an excellent cellular source to take part in in vitro models to study bone tissue engineering.

New Multiscale Characterization Methodology for Effective Determination of Isolation-Structure-Function Relationship of Extracellular Vesicles

Extracellular vesicles (EVs) have been lauded as next-generation medicines, but very few EV-based therapeutics have progressed to clinical use. Limited clinical translation is largely due to technical barriers that hamper our ability to mass produce EVs, i.e., to isolate, purify, and characterize them effectively. Technical limitations in comprehensive characterization of EVs lead to unpredicted biological effects of EVs. Here, using a range of optical and non-optical techniques, we showed that the differences in molecular composition of EVs isolated using two isolation methods correlated with the differences in their biological function. Our results demonstrated that the isolation method determines the composition of isolated EVs at single and sub-population levels. Besides the composition, we measured for the first time the dry mass and predicted sedimentation of EVs. These parameters were likely to contribute to the biological and functional effects of EVs on single cell and cell cultures. We anticipate that our new multiscale characterization approach, which goes beyond traditional experimental methodology, will support fundamental understanding of EVs as well as elucidate the functional effects of EVs in in vitro and in vivo studies. Our findings and methodology will be pivotal for developing optimal isolation methods and establishing EVs as mainstream therapeutics and diagnostics. This innovative approach is applicable to a wide range of sectors including biopharma and biotechnology as well as to regulatory agencies.

Extracellular-Vesicle-Based Coatings Enhance Bioactivity of Titanium Implants-SurfEV

Extracellular vesicles (EVs) are nanoparticles released by cells that contain a multitude of biomolecules, which act synergistically to signal multiple cell types. EVs are ideal candidates for promoting tissue growth and regeneration. The tissue regenerative potential of EVs raises the tantalizing possibility that immobilizing EVs on implant surfaces could potentially generate highly bioactive and cell-instructive surfaces that would enhance implant integration into the body. Such surfaces could address a critical limitation of current implants, which do not promote bone tissue formation or bond bone. Here, we developed bioactive titanium surface coatings (SurfEV) using two types of EVs: secreted by decidual mesenchymal stem cells (DEVs) and isolated from fermented papaya fluid (PEVs). For each EV type, we determined the size, morphology, and molecular composition. High concentrations of DEVs enhanced cell proliferation, wound closure, and migration distance of osteoblasts. In contrast, the cell proliferation and wound closure decreased with increasing concentration of PEVs. DEVs enhanced Ca/P deposition on the titanium surface, which suggests improvement in bone bonding ability of the implant (i.e., osteointegration). EVs also increased production of Ca and P by osteoblasts and promoted the deposition of mineral phase, which suggests EVs play key roles in cell mineralization. We also found that DEVs stimulated the secretion of secondary EVs observed by the presence of protruding structures on the cell membrane. We concluded that, by functionalizing implant surfaces with specialized EVs, we will be able to enhance implant osteointegration by improving hydroxyapatite formation directly at the surface and potentially circumvent aseptic loosening of implants.

Identification and characterisation of maternal perivascular SUSD2+ placental mesenchymal stem/stromal cells

Mesenchymal stem cells (MSCs) that meet the International Society for Cellular Therapy (ISCT) criteria are obtained from placental tissue by plastic adherence. Historically, no known single marker was available for isolating placental MSCs (pMSCs) from the decidua basalis. As the decidua basalis is derived from the regenerative endometrium, we hypothesised that SUSD2, an endometrial perivascular MSC marker, would purify maternal perivascular pMSC. Perivascular pMSCs were isolated from the maternal placenta using SUSD2 magnetic bead sorting and assessed for the colony-forming unit-fibroblasts (CFU-F), surface markers, and in vitro differentiation into mesodermal lineages. Multi-colour immunofluorescence was used to colocalise SUSD2 and α-SMA, a perivascular marker in the decidua basalis. Placental stromal cell suspensions comprised 5.1%SUSD2⁺ cells. SUSD2 magnetic bead sorting of the placental stromal cells increased their purity approximately two-fold. SUSD2⁺ pMSCs displayed greater CFU-F activity than SUSD2^- stromal fibroblasts (pSFs). However, both SUSD2⁺ pMSC and SUSD2^- pSF underwent mesodermal differentiation in vitro, and both expressed the ISCT surface markers. Higher percentages of cultured SUSD2⁺ pMSCs expressed the perivascular markers CD146, CD140b, and SUSD2 than SUSD2^- pSFs. These findings suggest that SUSD2 is a single marker that enriches maternal pMSCs, suggesting they may originate from eMSC. Placental decidua basalis can be used as an alternative source of MSC for clinical translation in situations where there is no access to endometrial tissue.

First trimester placental mesenchymal stem cells improve cardiac function of rat after myocardial infarction via enhanced neovascularization

Acute myocardial infarction (AMI) is the most critical heart disease. Mesenchymal stem cells (MSCs) have been widely used as a therapy for AMI for several years. The human placenta has emerged as a valuable source of transplantable cells of mesenchymal origin that can be used for multiple cytotherapeutic purposes. However, the different abilities of first trimester placental chorion mesenchymal stem cells (FCMSCs) and third trimester placental chorion mesenchymal stem cells (TCMSCs) have not yet been explored. In this study, we aimed to compare the effectiveness of FCMSCs and TCMSCs on the treatment of AMI. FCMSCs and TCMSCs were isolated and characterized, and then they were subjected to in vitro endothelial cell (EC) differentiation induction and tube formation to evaluate angiogenic ability. Moreover, the in vivo effects of FCMSCs and TCMSCs on cardiac improvement were also evaluated in a rat MI model. Both FCSMCs and TCMSCs expressed a series of MSCs surface markers. After differentiation induction, FCMSCs-derived EC (FCMSCs-EC) exhibited morphology that was more similar to that of ECs and had higher CD31 and vWF levels than TCMSCs-EC. Furthermore, tube formation could be achieved by FCMSCs-EC that was significantly better than that of TCMSCs-EC. Especially, FCMSCs-EC expressed higher levels of pro-angiogenesis genes, PDGFD, VEGFA, and TNC, and lower levels of anti-angiogenesis genes, SPRY1 and ANGPTL1. In addition, cardiac improvement, indicated by left ventricular end-diastolic diameter (LVEDd), left ventricular end-systolic diameter (LVEDs), left ventricular ejection fraction (LVEF) and left ventricular shortening fraction (LVSF), could be observed following treatment with FCMSCs, and it was superior to that of TCMSCs and Bone marrow MSCs (BMSCs). FCMSCs exhibited a superior ability to generate EC differentiation, as evidenced by in vitro morphology, angiogenic potential and in vivo cardiac function improvement; further, increased levels of expression of pro-angiogenesis genes may be the mechanism by which this effect occurred.

Influence of culture media on the derivation and phenotype of fetal-derived placental mesenchymal stem/stromal cells across gestation

INTRODUCTION

Derivation of pure fetal placental mesenchymal stem/stromal cells (pMSCs) is key to understand their role in placental development. However, isolated pMSCs are often contaminated by maternal-derived decidual MSCs (dMSCs). EGM-2 medium promotes the derivation of term fetal pMSCs, but the extent of first-trimester maternal pMSC contamination remains unclear. Culture media can also affect MSC phenotype. Here, we examined the effects of culture media on maternal pMSC contamination and fetal pMSC phenotype across gestation.

METHODS

pMSCs were derived from first-trimester or term placentae in advanced-DMEM/F12 medium or EGM-2 medium. Proportions of maternal (XX) and fetal (XY) cells in male pMSC cultures were determined by fluorescence in-situ hybridization. pMSC phenotype was analysed by flow cytometry, immunohistochemistry and Alamar blue proliferation assays.

RESULTS

When derived in advanced-DMEM/F12, all first trimester pMSC isolates exhibited maternal contamination (>72% XX cells, n = 5), whilst 7/9 term pMSC isolates were >98% fetal. When derived in EGM-2, all first trimester (n = 4) and term (n = 9) pMSC isolates contained 95-100% fetal cells. Fetal pMSCs in EGM-2 proliferated 2-fold (first-trimester) or 4-fold (term) faster than those in advanced-DMEM/F12 (p < 0.05, n = 3). Fetal pMSCs in both media expressed the generic MSC marker profile (CD90⁺, CD105+, CD73⁺, CD31-, CD34-, CD144-). However, pMSCs transferred from EGM-2 to advanced-DMEM/F12 increased expression of smooth muscle cell markers calponin and α-smooth muscle actin, and decreased expression of the vascular cell marker VEGFR2 (n = 3).

CONCLUSIONS

Deriving first-trimester pMSC in EGM-2 dramatically reduces maternal dMSC contamination. Media affects fetal pMSC phenotype, and careful consideration should be given to application specific culture conditions.

Placenta Stem/Stromal Cell-Derived Extracellular Vesicles for Potential Use in Lung Repair

Many acute and chronic lung injuries are incurable and rank as the fourth leading cause of death globally. While stem cell treatment for lung injuries is a promising approach, there is growing evidence that the therapeutic efficacy of stem cells originates from secreted extracellular vesicles (EVs). Consequently, EVs are emerging as next-generation therapeutics. While EVs are extensively researched for diagnostic applications, their therapeutic potential to promote tissue repair is not fully elucidated. By housing and delivering tissue-repairing cargo, EVs refine the cellular microenvironment, modulate inflammation, and ultimately repair injury. Here, the potential use of EVs derived from two placental mesenchymal stem/stromal cell (MSC) lines is presented; a chorionic MSC line (CMSC29) and a decidual MSC cell line (DMSC23) for applications in lung diseases. Functional analyses using in vitro models of injury demonstrate that these EVs have a role in ameliorating injuries caused to lung cells. It is also shown that EVs promote repair of lung epithelial cells. This study is fundamental to advancing the field of EVs and to unlock the full potential of EVs in regenerative medicine.

Immortalizing Mesenchymal Stromal Cells from Aged Donors While Keeping Their Essential Features

Human bone marrow-derived mesenchymal stromal cells (MSCs) obtained from aged patients are prone to senesce and diminish their differentiation potential, therefore limiting their usefulness for osteochondral regenerative medicine approaches or to study age-related diseases, such as osteoarthiritis (OA). MSCs can be transduced with immortalizing genes to overcome this limitation, but transduction of primary slow-dividing cells has proven to be challenging. Methods for enhancing transduction efficiency (such as spinoculation, chemical adjuvants, or transgene expression inductors) can be used, but several parameters must be adapted for each transduction system. In order to develop a transduction method suitable for the immortalization of MSCs from aged donors, we used a spinoculation method. Incubation parameters of packaging cells, speed and time of centrifugation, and valproic acid concentration to induce transgene expression have been adjusted. In this way, four immortalized MSC lines (iMSC#6, iMSC#8, iMSC#9, and iMSC#10) were generated. These immortalized MSCs (iMSCs) were capable of bypassing senescence and proliferating at a higher rate than primary MSCs. Characterization of iMSCs showed that these cells kept the expression of mesenchymal surface markers and were able to differentiate towards osteoblasts, adipocytes, and chondrocytes. Nevertheless, alterations in the CD105 expression and a switch of cell fate-commitment towards the osteogenic lineage have been noticed. In conclusion, the developed transduction method is suitable for the immortalization of MSCs derived from aged donors. The generated iMSC lines maintain essential mesenchymal features and are expected to be useful tools for the bone and cartilage regenerative medicine research.

Usefulness of Mesenchymal Cell Lines for Bone and Cartilage Regeneration Research

The unavailability of sufficient numbers of human primary cells is a major roadblock for in vitro repair of bone and/or cartilage, and for performing disease modelling experiments. Immortalized mesenchymal stromal cells (iMSCs) may be employed as a research tool for avoiding these problems. The purpose of this review was to revise the available literature on the characteristics of the iMSC lines, paying special attention to the maintenance of the phenotype of the primary cells from which they were derived, and whether they are effectively useful for in vitro disease modeling and cell therapy purposes. This review was performed by searching on Web of Science, Scopus, and PubMed databases from 1 January 2015 to 30 September 2019. The keywords used were ALL = (mesenchymal AND ("cell line" OR immortal*) AND (cartilage OR chondrogenesis OR bone OR osteogenesis) AND human). Only original research studies in which a human iMSC line was employed for osteogenesis or chondrogenesis experiments were included. After describing the success of the immortalization protocol, we focused on the iMSCs maintenance of the parental phenotype and multipotency. According to the literature revised, it seems that the maintenance of these characteristics is not guaranteed by immortalization, and that careful selection and validation of clones with particular characteristics is necessary for taking advantage of the full potential of iMSC to be employed in bone and cartilage-related research.

High-fidelity probing of the structure and heterogeneity of extracellular vesicles by resonance-enhanced atomic force microscopy infrared spectroscopy

Extracellular vesicles (EVs) are highly specialized nanoscale assemblies that deliver complex biological cargos to mediate intercellular communication. EVs are heterogeneous, and characterization of this heterogeneity is paramount to understanding EV biogenesis and activity, as well as to associating them with biological responses and pathologies. Traditional approaches to studying EV composition generally lack the resolution and/or sensitivity to characterize individual EVs, and therefore the assessment of EV heterogeneity has remained challenging. We have recently developed an atomic force microscope IR spectroscopy (AFM-IR) approach to probe the structural composition of single EVs with nanoscale resolution. Here, we provide a step-by-step procedure for our approach and show its power to reveal heterogeneity across individual EVs, within the same population of EVs and between different EV populations. Our approach is label free and able to detect lipids, proteins and nucleic acids within individual EVs. After isolation of EVs from cell culture medium, the protocol involves incubation of the EV sample on a suitable substrate, setup of the AFM-IR instrument and collection of nano-IR spectra and nano-IR images. Data acquisition and analyses can be completed within 24 h, and require only a basic knowledge of spectroscopy and chemistry. We anticipate that new understanding of EV composition and structure through AFM-IR will contribute to our biological understanding of EV biology and could find application in disease diagnosis and the development of EV therapies.

Tailoring the properties of a hypoxia-responsive 1,8-naphthalimide for imaging applications

Sensing hypoxia in tissues and cell models can provide insights into its role in disease states and cell development. Fluorescence imaging is a minimally-invasive method of visualising hypoxia in many biological systems. Here we present a series of improved bioreductive fluorescent sensors based on a nitro-naphthalimide structure, in which selectivity, photophysical properties, toxicity and cellular uptake are tuned through structural modifications. This new range of compounds provides improved probes for imaging and monitoring hypoxia, customised for a range of different applications. Studies in monolayers show the different reducing capabilities of hypoxia-resistant and non-resistant cell lines, and studies in tumour models show successful staining of the hypoxic region.

Valproic acid stimulates in vitro migration of the placenta-derived mesenchymal stem/stromal cell line CMSC29

Background

The placenta is an abundant source of mesenchymal stem/stromal cells (MSC), but our understanding of their functional properties remains limited. We previously created a placental-derived chorionic MSC (CMSC) cell line to overcome the difficulties associated with conducting extensive ex vivo optimization and experimental work on primary cells. The aim of this study was to characterize the migratory behavior of the CMSC29 cell line in vitro.

Methods

Stimulators of MSC migration, including two cytokines, stromal cell-derived factor-1α (SDF-1α) and hepatocyte growth factor (HGF), and a pharmacological agent, valproic acid (VPA), were tested for their ability to stimulate CMSC29 cell migration. Assessment of cell migration was performed using the xCELLigence Real-Time Cell Analyzer (RTCA).

Results

There was no significant increase in CMSC29 cell migration towards serum free medium with increasing concentration gradients of SDF-1α or HGF. In contrast, treating CMSC29 cells with VPA alone significantly increased their migration towards serum free medium.

Conclusions

Immortalized CMSC29 cells retain important properties of primary CMSC, but their migratory properties are altered. CMSC29 cells do not migrate in response to factors that reportedly stimulate primary MSC/CMSC migration. However, CMSC29 increase their migration in response to VPA treatment alone. Further studies are needed to determine the mechanism by which VPA acts alone to stimulate CMSC29 migration. Still, this study provides evidence that VPA pre-treatment may improve the benefits of cell-based therapies that employ certain MSC sub-types.

An ex vivo human placental vessel perfusion method to study mesenchymal stem/stromal cell migration

Background

To initiate tissue repair, mesenchymal stem/stromal cells (MSCs) must enter the blood stream, migrate to the targeted area, cross the endothelial barrier and home to the damaged tissue. This process is not yet fully understood in humans and thus, the aim of this study was to develop an ex vivo placental vessel perfusion method to examine human MSC movement from a blood vessel into human tissue. This will provide a better understanding of MSC migration, movement through the endothelial barrier and engraftment into target tissue, in a setting that more closely represents the in vivo state, compared with conventional in vitro human cell culture models. Moreover, important similarities and differences to animal experimental model systems may be revealed by this method.

Methods

Human placental hTERT transformed MSC lines were labelled with live-cell fluorescence dyes, and then perfused into term human placental blood vessel. After labelled MSCs were perfused into the vessel, the vessel was dissected from the placenta and incubated at cell growth conditions. Following incubation, the vessel was washed thoroughly to remove unattached, labelled MSCs and then snap frozen for sectioning. After sectioning, immunofluorescence staining of the endothelium was carried out to detect if labelled MSCs crossed the endothelial barrier.

Results

Twelve placental vessel perfusions were successfully completed. In eight of the twelve perfused vessels, qualitative assessment of immunofluorescence in sections (n=20, 5 µm sections/vessel) revealed labelled MSCs had crossed the endothelial barrier.

Conclusions

The human placental ex vivo vessel perfusion method could be used to assess human MSC migration into human tissue. Cells of the MSC lines were able to adhere and transmigrate through the endothelial barrier in a manner similar to that of leukocytes. Notably, cells that transmigrated remained in close proximity to the endothelium, which is consistent with the reported MSC vascular niche in placental blood vessels.

None of us is the same as all of us: resolving the heterogeneity of extracellular vesicles using single-vesicle, nanoscale characterization with resonance enhanced atomic force microscope infrared spectroscopy (AFM-IR)

Extracellular vesicles (EVs) are highly specialized, nanoscale messengers that deliver biological signals and in doing so mediate intercellular communication. Increasing evidence shows that within populations of EVs, important properties including morphology, membrane composition, and content vary substantially. This heterogeneity arises in response to the nature, state, and environmental conditions of the cell source. However, currently there are no effective approaches, which unequivocally discriminate differences between individual EVs, which critically hampers progress in this emerging scientific area. Measuring EV heterogeneity is paramount to our understanding of how EVs influence the physiological and pathological functions of their target cells. Moreover, understanding EV heterogeneity is essential for their application as diagnostics and therapeutics. We propose an innovative approach using resonance enhanced atomic force microscope infrared spectroscopy (AFM-IR) to identify the nanoscale structural composition of EVs, as demonstrated and validated using EVs derived from two types of placenta stem cells. The particular strength of this approach is that it is a label-free and ultra-high sensitivity technique that has the power to measure individual EV heterogeneity. New insights gained by this method into EV heterogeneity will have a profound impact not only on our basic understanding of EV biology but also on disease diagnostics and the emerging area of EV-therapies.

Transferable Matrixes Produced from Decellularized Extracellular Matrix Promote Proliferation and Osteogenic Differentiation of Mesenchymal Stem Cells and Facilitate Scale-Up

Decellularized extracellular matrixes (dECM) derived from mesenchymal stem cell (MSC) cultures have recently emerged as cell culture substrates that improve the proliferation, differentiation, and maintenance of MSC phenotype during ex vivo expansion. These biomaterials have considerable potential in the fields of stem cell biology, tissue engineering, and regenerative medicine. Processing the dECMs into concentrated solutions of biomolecules that enable the useful properties of the native dECM to be transferred to a new surface via a simple adsorption step would greatly increase the usefulness and impact of this technology. The development of such solutions, hereafter referred to as transferable matrixes, is the focus of this article. In this work, we produced transferable matrixes from dECM derived from two human placental MSC cell lines (DMSC23 and CMSC29) using pepsin digestion (P-ECM), urea extraction (U-ECM), and mechanical homogenization in acetic acid (AA-ECM). Native dECMs improved primary DMSC proliferation as well as osteogenic and adipogenic differentiation, compared with traditional expansion procedures. Interestingly, tissue culture plastic coated with P-ECM was able to replicate the proliferative effects of native dECM, while U-ECM was able to replicate osteogenic differentiation. These data illustrate the feasibility of producing dECM-derived transferable matrixes that replicate key features of the native matrixes and show that different processing techniques produce transferable matrixes with varying bioactivities. Additionally, these transferable matrixes are able to coat 1.3-5.2 times the surface area covered by the native dECM, facilitating scale-up of this technology.

Comparison of the Biological Characteristics of Mesenchymal Stem Cells Derived from the Human Placenta and Umbilical Cord

Mesenchymal stem/stromal cells (MSCs) derived from placental tissue show great therapeutic potential and have been used in medical treatment, but the similarity and differences between the MSCs derived from various parts of the placenta remain unclear. In this study, we compared MSCs derived from different perinatal tissues, including the umbilical cord (UC), amniotic membrane (AM), chorionic plate (CP) and decidua parietalis (DP). Using human leukocyte antigen (HLA) typing and karyotype analysis, we found that the first three cell types were derived from the foetus, while the MSCs from the decidua parietalis were derived from the maternal portion of the placental tissue. Our results indicate that both foetal and maternal MSCs share a similar phenotype and multi-lineage differentiation potential, but foetal MSCs show a significantly higher expansion capacity than do maternal MSCs. Furthermore, MSCs from all sources showed significant differences in the levels of several paracrine factors.

Comprehensive characterization of chorionic villi-derived mesenchymal stromal cells from human placenta

BACKGROUND

Studies in which mesenchymal stromal cells (MSC) from the placenta are compared with multiple MSC types from other sources are rare. The chorionic plate of the human placenta is mainly composed of fetal blood vessels embedded in fetal stroma tissue, lined by trophoblastic cells and organized into chorionic villi (CV) structures.

METHODS

We comprehensively characterized human MSC collected from postnatal human chorionic villi of placenta (CV-MSC) by analyzing their growth and proliferation potential, differentiation, immunophenotype, extracellular matrix production, telomere length, aging phenotype, and plasticity.

RESULTS

Immunophenotypic characterization of CV-MSC confirmed the typical MSC marker expression as defined by the International Society for Cellular Therapy. The surface marker profile was consistent with increased potential for proliferation, vascular localization, and early myogenic marker expression. CV-MSC retained multilineage differentiation potential and extracellular matrix remodeling properties. They have undergone reduced telomere loss and delayed onset of cellular senescence as they aged in vitro compared to three other MSC sources. We present evidence that increased human telomerase reverse transcriptase gene expression could not explain the exceptional telomere maintenance and senescence onset delay in cultured CV-MSC. Our in-vitro tumorigenesis detection assay suggests that CV-MSC are not prone to undergo malignant transformation during long-term in-vitro culture. Besides SOX2 expression, no other pluripotency features were observed in early and late passages of CV-MSC.

CONCLUSIONS

Our work brings forward two remarkable characteristics of CV-MSC, the first being their extended life span as a result of delayed replicative senescence and the second being a delayed aged phenotype characterized by improved telomere length maintenance. MSC from human placenta are very attractive candidates for stem cell-based therapy applications.

Isolation and Characterization of Mesenchymal Stem/Stromal Cells Derived from Human Third Trimester Placental Chorionic Villi and Decidua Basalis

The decidua basalis and placental chorionic villi are critical components of maternal-fetal interface, which plays a critical role in normal placental development. Failure to form a proper maternal-fetal interface is associated with clinically important placental pathologies including preeclampsia and fetal growth restriction. Placental trophoblast cells are well known for their critical roles in establishing the maternal-fetal interface; however accumulating evidence also implicates mesenchymal stem/stromal cells that envelop the maternal and fetal blood vessels as playing an important role in the formation and efficient functioning of the interface. Moreover, recent studies associate abnormal mesenchymal stem/stromal cell function in the development of preeclampsia. Further research is needed to fully understand the role that these cells play in this clinically important placental pathology.The intimate relationship between maternal and fetal tissues at the interface poses significant problems in the enrichment of decidua basalis and chorionic villous mesenchymal stem/stromal cells without significant cross-contamination. The protocols described below for the enrichment and characterization of mesenchymal stem/stromal cells from the maternal-fetal interface produce highly enriched cells that conform to international standards and show minimal cross-contamination.

The application of decellularized human term fetal membranes in tissue engineering and regenerative medicine (TERM)

Tissue engineering and regenerative medicine (TERM) is a field that applies biology and engineering principles to "restore, maintain or repair a tissue after injury". Besides the potential to treat various diseases, these endeavours increase our understanding of fundamental cell biology. Although TERM has progressed rapidly, engineering a whole organ is still beyond our skills, primarily due to the complexity of tissues. Material science and current manufacturing methods are not capable of mimicking this complexity. Therefore, many researchers explore the use of naturally derived materials that maintain important biochemical, structural and mechanical properties of tissues. Consequently, employing non-cellular components of tissues, particularly the extracellular matrix, has emerged as an alternative to synthetic materials. Because of their complexity, decellularized tissues are not as well defined as synthetic materials but they provide cells with a microenvironment that resembles their natural niche. Decellularized tissues are produced from a variety of sources, among which the fetal membranes are excellent candidates since their supply is virtually unlimited, they are readily accessible with minimum ethical concerns and are often discarded as a biological waste. In this review, we will discuss various applications of decellularized fetal membranes as substrates for the expansion of stem cells, their use as two and three-dimensional scaffolds for tissue regeneration, and their use as cell delivery systems. We conclude that fetal membranes have great potential for use in TERM.

The effect of endothelial cell activation and hypoxia on placental chorionic mesenchymal stem/stromal cell migration

INTRODUCTION

Chorionic mesenchymal stem/stromal cells (CMSC) can be isolated from the placenta in large numbers. Although their functions are yet to be fully elucidated, they have a role in tissue development and repair. To fulfil such a role, CMSC must be able to migrate to the microenvironment of the injury site. This process is not fully understood and the aim of this study therefore, was to examine in vitro CMSC migration in response to tissue inflammation and hypoxic conditioning.

METHODS

CMSC were derived from the chorionic villi. A trans-endothelium migration (TEM) assay was used to study CMSC migration through an activated endothelial cell monolayer using the HMEC-1 cell line. A cytokine array was used to identify and compare the cytokine production profile of activated versus non-activated HMEC-1.

RESULTS

There were significant changes in cytokine production by HMEC-1 cells following lipopolysaccharide (LPS) treatment and hypoxic conditioning. Despite this, results from the TEM assay showed no significant change in the average number of CMSC that migrated through the LPS activated HMEC-1 layer compared to the untreated control. Furthermore, there was no significant change in the average number of CMSC that migrated through the HMEC-1 monolayer when exposed to hypoxic (1% O₂), normoxic (8% O₂) or hyperoxic (21% O₂) conditions.

CONCLUSION

These data suggest that cell functions such as transendothelial migration can vary between MSC derived from different tissues in response to the same biological cues.

Native and solubilized decellularized extracellular matrix: A critical assessment of their potential for improving the expansion of mesenchymal stem cells

Capturing the promise of mesenchymal stem cell (MSC)-based treatments is currently limited by inefficient production of cells needed for clinical therapies. During conventional ex vivo expansion, a large portion of MSCs lose the properties that make them attractive for use in cell therapies. Decellularized extracellular matrix (dECM) has recently emerged as a promising substrate for the improved expansion of MSCs. MSCs cultured on these surfaces exhibit improved proliferation capacity, maintenance of phenotype, and increased differentiation potential. Additionally, these dECMs can be solubilized and used to coat new cell culture surfaces, imparting key biological properties of the native matrices to other surfaces such as tissue engineering scaffolds. Although this technology is still developing, there is potential for an impact in the fields of MSC biology, biomaterials, tissue engineering, and therapeutics. In this article, we review the role of dECM in MSC expansion by first detailing the decellularization methods that have been used to produce the dECM substrates; discussing the shortcomings of current decellularization methods; describing the improved MSC characteristics obtained when the cells are cultured on these surfaces; and considering the effect of the passage number, age of donor, and dECM preparation method on the quality of the dECM. Finally we describe the critical roadblocks that must be addressed before this technology can fulfil its potential, including elucidating the mechanism by which the dECMs improve the expansion of primary MSCs and the identification of a readily available source of dECM.

STATEMENT OF SIGNIFICANCE

Current mesenchymal stem cell (MSC) culture methods result in premature cellular senescence or loss of differentiation potential. This creates a major bottleneck in their clinical application, as prolonged expansion is necessary to achieve clinically relevant numbers of cells. Recently, decellularized extracellular matrix (dECM) produced by primary MSC has emerged as an attractive substrate for the improved expansion of MSC; cells cultured on these surfaces retain their desired stem cell characteristics for prolonged times during culture. This review article describes the inception and development of this dECM-based technology, points out existing challenges that must be addressed, and suggests future directions of research. To our knowledge, this is the first review written on the use of dECM for improved mesenchymal stem cell expansion.

Reduced aldehyde dehydrogenase expression in preeclamptic decidual mesenchymal stem/stromal cells is restored by aldehyde dehydrogenase agonists

High resistance to oxidative stress is a common feature of mesenchymal stem/stromal cells (MSC) and is associated with higher cell survival and ability to respond to oxidative damage. Aldehyde dehydrogenase (ALDH) activity is a candidate “universal” marker for stem cells. ALDH expression was significantly lower in decidual MSC (DMSC) isolated from preeclamptic (PE) patients. ALDH gene knockdown by siRNA transfection was performed to create a cell culture model of the reduced ALDH expression detected in PE-DMSC. We showed that ALDH activity in DMSC is associated with resistance to hydrogen peroxide (H₂O₂)-induced toxicity. Our data provide evidence that ALDH expression in DMSC is required for cellular resistance to oxidative stress. Furthermore, candidate ALDH activators were screened and two of the compounds were effective in upregulating ALDH expression. This study provides a proof-of-principle that the restoration of ALDH activity in diseased MSC is a rational basis for a therapeutic strategy to improve MSC resistance to cytotoxic damage.

Decellularized extracellular matrices produced from immortal cell lines derived from different parts of the placenta support primary mesenchymal stem cell expansion

Mesenchymal stem/stromal cells (MSCs) exhibit undesired phenotypic changes during ex vivo expansion, limiting production of the large quantities of high quality primary MSCs needed for both basic research and cell therapies. Primary MSCs retain many desired MSC properties including proliferative capacity and differentiation potential when expanded on decellularized extracellular matrix (dECM) prepared from primary MSCs. However, the need to use low passage number primary MSCs (passage 3 or lower) to produce the dECM drastically limits the utility and impact of this technology. Here, we report that primary MSCs expanded on dECM prepared from high passage number (passage 25) human telomerase reverse transcriptase (hTERT) transduced immortal MSC cell lines also exhibit increased proliferation and osteogenic differentiation. Two hTERT-transduced placenta-derived MSC cell lines, CMSC29 and DMSC23 [derived from placental chorionic villi (CMSCs) and decidua basalis (DMSCs), respectively], were used to prepare dECM-coated substrates. These dECM substrates showed structural and biochemical differences. Primary DMSCs cultured on dECM-DMSC23 showed a three-fold increase in cell number after 14 days expansion in culture and increased osteogenic differentiation compared with controls. Primary CMSCs cultured on the dECM-DMSC23 exhibited a two-fold increase in cell number and increased osteogenic differentiation. We conclude that immortal MSC cell lines derived from different parts of the placenta produce dECM with varying abilities for supporting increased primary MSC expansion while maintaining important primary MSC properties. Additionally, this is the first demonstration of using high passage number cells to produce dECM that can promote primary MSC expansion, and this advancement greatly increases the feasibility and applicability of dECM-based technologies.