Mesenchymal stem cells : characteristics and clinical applications

Mesenchymal stem cells (MSCs) are bone marrow populating cells, different from hematopoietic stem cells, which possess an extensive proliferative potential and ability to differentiate into various cell types, including: osteocytes, adipocytes, chondrocytes, myocytes, cardiomyocytes and neurons. MSCs play a key role in the maintenance of bone marrow homeostasis and regulate the maturation of both hematopoietic and non-hematopoietic cells. The cells are characterized by the expression of numerous surface antigens, but none of them appears to be exclusively expressed on MSCs. Apart from bone marrow, MSCs are located in other tissues, like: adipose tissue, peripheral blood, cord blood, liver and fetal tissues. MSCs have been shown to be powerful tools in gene therapies, and can be effectively transduced with viral vectors containing a therapeutic gene, as well as with cDNA for specific proteins, expression of which is desired in a patient. Due to such characteristics, the number of clinical trials based on the use of MSCs increase. These cells have been successfully employed in graft versus host disease (GvHD) treatment, heart regeneration after infarct, cartilage and bone repair, skin wounds healing, neuronal regeneration and many others. Of special importance is their use in the treatment of osteogenesis imperfecta (OI), which appeared to be the only reasonable therapeutic strategy. MSCs seem to represent a future powerful tool in regenerative medicine, therefore they are particularly important in medical research

The dynamics of the electrotactic reaction of mouse 3T3 fibroblasts

The molecular mechanisms behind electrotaxis remain largely unknown, with no identified primary direct current electric field (dcEF) sensor. Two leading hypotheses propose mechanisms involving the redistribution of charged components in the cell membrane (driven by electrotaxis of electroosmosis) and the asymmetric activation of ion channels. To investigate these mechanisms, we studied the dynamics of electrotactic behaviour of mouse 3T3 fibroblasts. We observed that 3T3 fibroblasts exhibit cathodal migration within just 1 min when exposed to physiological dcEF. This rapid response suggests the involvement of ion channels in the cell membrane. Our large-scale screening method identified several ion channel genes as potential key players, including the inwardly rectifying potassium channel Kir4.2. Blocking the Kir channel family with $Ba^{2+}$ or silencing the Kcnj15 gene, encoding Kir4.2, significantly reduced the directional migration of 3T3 cells. Additionally, the levels of the intracellular regulators of Kir channels, spermine (SPM) and spermidine (SPD), had a significant impact on cell directionality. Interestingly, inhibiting Kir4.2 resulted in the temporary cessation of electrotaxis for approximately 1-2 h before its return. This observation suggests a two-phase mechanism for the electrotaxis of mouse 3T3 fibroblasts, where ion channel activation triggers the initial rapid response to dcEF, and the subsequent redistribution of membrane receptors sustains long-term directional movement. In summary, our study unveils the involvement of Kir channels and proposes a biphasic mechanism to explain the electrotactic behaviour of mouse 3T3 fibroblasts, shedding light on the molecular underpinnings of electrotaxis

Non-integrating gamma-retroviral vectors as a versatile tool for transient zinc-finger nuclease delivery

Designer nucleases, like zinc-finger nucleases (ZFNs), represent valuable tools for targeted genome editing. Here, we took advantage of the gamma-retroviral life cycle and produced vectors to transfer ZFNs in the form of protein, mRNA and episomal DNA. Transfer efficacy and ZFN activity were assessed in quantitative proof-of-concept experiments in a human cell line and in mouse embryonic stem cells. We demonstrate that retrovirus-mediated protein transfer (RPT), retrovirus-mediated mRNA transfer (RMT), and retrovirus-mediated episome transfer (RET) represent powerful methodologies for transient protein delivery or protein expression. Furthermore, we describe complementary strategies to augment ZFN activity after gamma-retroviral transduction, including serial transduction, proteasome inhibition, and hypothermia. Depending on vector dose and target cell type, gene disruption frequencies of up to 15% were achieved with RPT and RMT, and >50% gene knockout after RET. In summary, non-integrating gamma-retroviral vectors represent a versatile tool to transiently deliver ZFNs to human and mouse cells

Inhibition of rhabdomyosarcoma's metastatic behavior through downregulation of MET receptor signaling.

Rhabdomyosarcoma (RMS) is a soft tissue sarcoma usually diagnosed in children. In advanced and metastatic stages the prognosis is often poor. RMS cell lines were used for evaluation of the role of MET receptor inhibition on chemotaxis and invasion. In vivo studies were performed using NOD-SCID xenograft model. This study shows that blocking of MET expression has strong influence on metastatic behavior of RMS. MET negative cells possess a reduced potential to migrate and to invade. Downregulation of MET suppressed the ability of RMS cells to populate bone marrow. Inhibition of MET negative tumor cells engraftment into bone marrow was observed. MET negative tumors were also two to four times smaller than their wild type counterparts. Since MET receptor plays a very important role in facilitating metastasis of RMS cells, blocking of HGF-MET axis might be considered as a therapeutic option for RMS patients, at more advanced and metastatic stages

Anti-inflammatory, Anti-fibrotic and pro-cardiomyogenic effects of genetically engineered extracellular vesicles enriched in miR-1 and miR-199a on human cardiac fibroblasts

Rationale Emerging evidence indicates that stem cell (SC)- derived extracellular vesicles (EVs) carrying bioactive miRNAs are able to repair damaged or infarcted myocardium and ameliorate adverse remodeling. Fibroblasts represent a major cell population responsible for scar formation in the damaged heart. However, the effects of EVs on cardiac fibroblast (CFs) biology and function has not been investigated. Objective To analyze the biological impact of stem cell-derived EVs (SC-EVs) enriched in miR-1 and miR-199a on CFs and to elucidate the underlying molecular mechanisms. Methods and Results Genetically engineered human induced pluripotent stem cells (hiPS) and umbilical cord-derived mesenchymal stem cells (UC-MSCs) expressing miR-1 or miR-199a were used to produce miR-EVs. Cells and EVs were thoughtfully analyzed for miRNA expression using RT-qPCR method. Both hiPS-miRs-EVs and UC-MSC-miRs-EVs effectively transferred miRNAs to recipient CFs, however, hiPS-miRs-EVs triggered cardiomyogenic gene expression in CFs more efficiently than UC-MSC-miRs-EVs. Importantly, hiPS-miR-1-EVs exhibited cytoprotective effects on CFs by reducing apoptosis, decreasing levels of pro-inflammatory cytokines (CCL2, IL-$1\beta$, IL-8) and downregulating the expression of a pro-fibrotic gene – $\alpha$-smooth muscle actin ($\alpha$-SMA). Notably, we identified a novel role of miR-199a-3p delivered by hiPS-EVs to CFs, in triggering the expression of cardiomyogenic genes (NKX2.5, TNTC, MEF2C) and ion channels involved in cardiomyocyte contractility (HCN2, SCN5A, KCNJ2, KCND3). By targeting SERPINE2, miR-199a-3p may reduce pro-fibrotic properties of CFs, whereas miR-199a-5p targeted BCAM and TSPAN6, which may be implicated in downregulation of inflammation. Conclusions hiPS-EVs carrying miR-1 and miR-199a attenuate apoptosis and pro-fibrotic and pro-inflammatory activities of CFs, and increase cardiomyogenic gene expression. These finding serve as rationale for targeting fibroblasts with novel EV-based miRNA therapies to improve heart repair after myocardial injury

Minimal Information for Studies of Extracellular Vesicles 2018 (MISEV2018): A Position Statement of the International Society for Extracellular Vesicles and Update of the MISEV2014 Guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points

Minimal information for studies of extracellular vesicles 2018 (MISEV2018):a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points