No abstract

Mesenchymal stem cells isolated from human placenta and in vitro labeled with fluorescent magnetic microparticles were intravenously injected to rats 2 days after induction of focal cerebral ischemia (endovascular model). According to MRT findings, transplantation of mesenchymal stem cells led to an appreciable reduction of the volume of ischemic focus in the brain. Two or three weeks after transplantation, labeled cells accumulated near and inside the ischemic focus, in the hippocampus, and in the subventricular zone of both hemispheres. Only few human mesenchymal stem cells populating the zone adjacent to the ischemic focus started expressing astroglial and neuronal markers. On the other hand, transplantation of mesenchymal stem cells stimulated proliferation of stem and progenitor cells in the subventricular zone and migration of these cells into the ischemic zone. Positive effects of transplantation of these cells to rats with experimental ischemic stroke are presumably explained by stimulation of proliferation of resident stem and progenitor cells of animal brain and their migration into the ischemic tissue and adjacent areas. Replacement of damaged rat neurons and glial cells by transplanted human cells, if it does take place, is quite negligible.

Mesenchymal stem cells from human placenta obtained after term natural delivery were cultured and labeled with vital dye Dil of magnetic fluorescing microparticles. The labeled cells were transplanted intravenously to rats with occlusion of the median cerebral artery. Penetration of cells through the brain-blood barrier and their distribution in the brain of experimental animals were studied on serial cryostat sections. Two models of cerebral artery occlusion associated with different traumatic consequences were used. The efficiency of crossing the blood-brain barrier by transplanted cells, the number of mesenchymal cells attaining the ischemic focus and neurogenic zones, and the time of death of transplanted cells largely depended on the degree and nature of injury to the central nervous system, which should be taken into account when planning the experiments for evaluation of the effects of cell therapy on the models of neurological diseases and in clinical studies in the field of regenerative neurology.

Mesenchymal stem cells enzymatically isolated from human placenta were labeled with magnetic fluorescent microparticles (d=0.96 μ). We showed that microparticles in high doses (>10 μl stock suspension per 1 ml culture medium) significantly inhibited cell proliferation in culture. In our work we determined the optimal concentration of particles not affecting physiological properties of mesenchymal stem cells: it does not change cell proliferation, does not induce apoptosis, and does not modulate their transdifferentiation into neuronal cells. In vivo experiments showed that the chosen particles allow easy visualization of transplanted cells ex vivo on sections of different tissues.