IntroductionIntra-arterial cell infusion is an efficient delivery route with which to target organs such as the ischemic brain. However, adverse events including microembolisms and decreased cerebral blood flow were recently reported after intra-arterial cell delivery in rodent models, raising safety concerns. We tested the hypothesis that cell dose, infusion volume, and velocity would be related to the severity of complications after intra-arterial cell delivery.MethodsIn this study, 38 rats were subjected to a sham middle cerebral artery occlusion (sham-MCAO) procedure before being infused with allogeneic bone-marrow mesenchymal stem cells at different cell doses (0 to 1.0 × 106), infusion volumes (0.5 to 1.0 ml), and infusion times (3 to 6 minutes). An additional group (n = 4) was infused with 1.0 × 106 cells labeled with iron oxide for in vivo tracking of cells. Cells were infused through the external carotid artery under laser Doppler flowmetry monitoring 48 hours after sham-MCAO. Magnetic resonance imaging (MRI) was performed 24 hours after cell infusion to reveal cerebral embolisms or hemorrhage. Limb placing, cylinder, and open field tests were conducted to assess sensorimotor functions before the rats were perfused for histology.ResultsA cell dose-related reduction in cerebral blood flow was noted, as well as an increase in embolic events and concomitant lesion size, and sensorimotor impairment. In addition, a low infusion velocity (0.5 ml/6 minutes) was associated with high rate of complications. Lesions on MRI were confirmed with histology and corresponded to necrotic cell loss and blood-brain barrier leakage.ConclusionsParticularly cell dose but also infusion velocity contribute to complications encountered after intra-arterial cell transplantation. This should be considered before planning efficacy studies in rats and, potentially, in patients with stroke.

Stem cell therapy for neurological disorders reached a pivotal point when the efficacy of several cell types was demonstrated in small animal models. Translation of stem cell therapy is contingent upon overcoming the challenge of effective cell delivery to the human brain, which has a volume ∼1000 times larger than that of the mouse. Intra-arterial injection can achieve a broad, global, but also on-demand spatially targeted biodistribution; however, its utility has been limited by unpredictable cell destination and homing as dictated by the vascular territory, as well as by safety concerns. We show here that high-speed MRI can be used to visualize the intravascular distribution of a superparamagnetic iron oxide contrast agent and can thus be used to accurately predict the distribution of intra-arterial administered stem cells. Moreover, high-speed MRI enables the real-time visualization of cell homing, providing the opportunity for immediate intervention in the case of undesired biodistribution.

Mesenchymal stem cells (MSCs) are attractive candidates for cell-based tissue repair approaches. Hundreds of clinical trials using MSCs have been completed and many others are still being investigated. For most therapeutic applications, MSC propagation in vitro is often required. However, ex vivo culture condition is not fully physiological and may affect biological properties of MSCs including their regenerative potential. Moreover, both cell cryopreservation and labelling procedure prior to infusion may have the negative impact on their expected effect in vivo. The incidence of MSC transformation during in vitro culture should be also taken into consideration before using cells in stem cell therapy. In our review, we focused on different aspects of MSC propagation that might influence their regenerative properties of MSC. We also discussed the influence of different factors that might abolish MSC proliferation and differentiation as well as potential impact of stem cell senescence and aging. Despite of many positive therapeutic effects of MSC therapy, one has to be conscious about potential cell changes that could appear during manufacturing of MSCs.

Mesenchymal stem cells (MSCs) are very attractive for regenerative medicine due to their relatively easy derivation and broad range of differentiation capabilities, either naturally or induced through cell engineering. However, efficient methods of delivery to diseased tissues and the long-term survival of grafted cells still need improvement. Here, we review genetic engineering approaches designed to enhance the migratory capacities of MSCs, as well as extend their survival after transplantation by the modulation of prosurvival approaches, including prevention of senescence and apoptosis. We highlight some of the latest examples that explore these pivotal points, which have great relevance in cell-based therapies.

Cell-based gene therapy holds a great promise for the treatment of human malignancy. Among different cells, mesenchymal stem cells (MSCs) are emerging as valuable anti-cancer agents that have the potential to be used to treat a number of different cancer types. They have inherent migratory properties, which allow them to serve as vehicles for delivering effective therapy to isolated tumors and metastases. MSCs have been engineered to express anti-proliferative, pro-apoptotic, and anti-angiogenic agents that specifically target different cancers. Another field of interest is to modify MSCs with the cytokines that activate pro-tumorigenic immunity or to use them as carriers for the traditional chemical compounds that possess the properties of anti-cancer drugs. Although there is still controversy about the exact function of MSCs in the tumor settings, the encouraging results from the preclinical studies of MSC-based gene therapy for a large number of tumors support the initiation of clinical trials.

Mesenchymal stem cells (MSCs) represent promising resource of cells for regenerative medicine in neurological disorders. However, efficient and minimally invasive methods of MSCs delivery to the brain still have to be developed. Intra-arterial route is very promising, but MSCs are missing machinery for diapedesis through blood-brain barrier. Thus, here we have tested a mRNA-based method to induce transient expression of ITGA4, an adhesion molecule actively involved in cell extravasation. We observed that transfection with an ITGA4-mRNA construct bearing a conventional cap analogue (7-methylguanosine) failed to produce ITGA4 protein, but exogenous ITGA4-mRNA was detected in transfected MSCs. This indicates that not transfection, but rather translation being the major roadblock. Stabilization of ITGA4-mRNA with SSB proteins resulted in ITGA4 protein synthesis in HEK293 cells only, whereas in MSCs, satisfactory results were obtained only after using an anti-reverse-cap-analogue (ARCA). The presence of ITGA4 protein in MSCs was transient and lasted for up to 24 h after transfection. Membranous location was confirmed by flow cytometry of viable non-permeabilized cells using anti-ITGA4 antibody. The mRNA-based expression of itga4 transgene is potentially sufficient for diapedesis after intra-arterial delivery. To conclude, mRNA-based engineering of stem cells is a rapid integration-free method and attractive from the perspective of potential future clinical application.

Mesenchymal stem cells (MSCs), which can be obtained from various organs and easily propagated in vitro, are one of the most extensively used types of stem cells and have been shown to be efficacious in a broad set of diseases. The unique and highly desirable properties of MSCs include high migratory capacities toward injured areas, immunomodulatory features, and the natural ability to differentiate into connective tissue phenotypes. These phenotypes include bone and cartilage, and these properties predispose MSCs to be therapeutically useful. In addition, MSCs elicit their therapeutic effects by paracrine actions, in which the metabolism of target tissues is modulated. Genetic engineering methods can greatly amplify these properties and broaden the therapeutic capabilities of MSCs, including transdifferentiation toward diverse cell lineages. However, cell engineering can also affect safety and increase the cost of therapy based on MSCs; thus, the advantages and disadvantages of these procedures should be discussed. In this review, the latest applications of genetic engineering methods for MSCs with regenerative medicine purposes are presented.

Podocalyxin (PODXL) is a type I membrane mucoprotein abundantly presented in the epithelial cells (podocytes) of kidney glomeruli where it plays an important role in maintaining the plasma filtration. PODXL is also expressed in other types of cells but its function is ignored. A recombinant soluble fragment of the PODXL ectodomain modifies the signaling of the membrane bound PODXL. Based on this antecedent, we aimed at investigating whether PODXL could be cleaved and released into the extracellular space as a soluble peptide. In this study, we used a fusion protein of human PODXL and green fluorescent protein expressed in CHO cells (CHO-PODXL-GFP) and a human tumor cell (Tera-1) inherently expressing PODXL. PODXL was detected by wide-field microscopy in the Golgi, the plasma membrane and in a vesicular form preferentially located at the leading edges of the cell and also progressing along the filopodium. We detected PODXL in the insoluble and soluble fractions of the extracellular medium of CHO-PODXL-GFP cells. Stimulation of protein kinase C (PKC) by Phorbol-12-myristate-13-acetate (PMA) enhanced the release of PODXL to the extracellular space whereas this effect was prevented either by inhibitors of PKC or specific inhibitors of matrix metalloproteinases. It is concluded that intact PODXL is released to the extracellular space as a cargo of microvesicles and also as a soluble cleaved fragment of ectodomain.