Target Cell Migration Research Articles

Mechanisms of glial-guided neuronal migration in vitro and in vivo

Our laboratory has developed an in vitro model system in which glial-guided neuronal migration can be observed in real time. Cerebellar granule neurons migrate on astroglial fibers by apposing their cell soma against the glial arm, forming a specialized migration junction, and extending a motile leading process in the direction of migration. In vitro assays indicate that the neuronal antigen astrotactin functions as a neuron-glia ligand, and is likely to play a role in the movement of neurons along glial fibers. In heterotypic recombinations of neurons and glia from mouse cerebellum and rat hippocampus, neurons migrate on heterotypic glial processes with a cytology, speed and mode of movement identical to that of neuronal migration on homotypic glial fibers, suggesting that glial fibers provide a permissive pathway for neuronal migration in developing brain. In vivo analyses of developing cerebellum demonstrate a close coordination of afferent axon ingrowth relative to target cell migration. These studies indicate that climbing fibers contact immature Purkinje neurons during the migration and settling of Purkinje cells, implicating a role for afferents in the termination of migration.

Quantitation of cytokine-stimulated migration of endothelium and epithelium by a new assay using microcarrier beads

Recent studies have identified a group of cytokines which appear to be cell-specific regulators of mobility in nonleukocytic mammalian cells. One example is scatter factor (SF), a soluble protein(s) produced by cultured fibroblasts and vascular smooth muscle cells which causes spreading and separation ("scattering") of tight, cohesive colonies of epithelial cells. Studies of SF action have been limited because the degree of scattering is difficult to quantitate and because scattering assays cannot be used to study potential target cells that do not form tight, cohesive colonies. We developed a simple, quantitative assay of SF-stimulated mobility based on migration of target cells off microcarrier beads onto plastic culture surfaces in 24-well plates. We showed that crude and partially purified SF derived from ras-transformed 3T3 cells stimulates migration of both epithelial and vascular endothelial cells but not of producer or nonproducer fibroblasts. Scatter and migration-stimulating activities copurified on cation exchange chromatography; and the degree of stimulation was closely correlated with scattering titer regardless of SF purity. Migration of endothelial cells from beads, while extremely sensitive to SF, was not affected by serum concentration (1 to 10%), various purified growth factors, or fibronectin. Both scattering and migration from beads were blocked by cycloheximide (0.1 microgram/ml) during assay incubation, suggesting that these processes require protein synthesis. The microcarrier bead assay may be a useful quantitative tool to study the biochemical mechanisms of SF-stimulated cell migration.

Photosensitization of leukemic cells and normal bone marrow cells by 514 nm laser light and effects of laser light on migration inhibition and lymphokine response

In a model for ex-vivo purging of bone marrow grafts, leukemic cells and normal bone marrow cells were treated with merocyanine 540 and exposed to 514 nm laser light. With this treatment, 99.9999% of leukemic cells were killed while 55% of the normal bone marrow cells survived. The deleterious effects of laser light alone in the absence of photosensitizer were not observed as determined by cell viability, cell migration, and response of target cells to human migration inhibition factor. These results indicate that laser light induced photodynamic therapy can be useful for ex-vivo autologous bone marrow purging without regard to the deleterious effects of laser light alone.

Two-step leukocyte migration in agarose technique.

A two-step modification of Clausen's technique of leukocyte migration under agarose is described. Blood leukocytes from a subject are incubated for approximately 4 days with or without antigen. The cultures, after reconstitution with antigen followed by repeated washing of the cultured cells, are added to fresh, dextran-separated blood leukocytes, and migration tests are performed in the absence of the antigen. Cells preincubated with antigen give a very marked reduction of the migration of the target leukocytes which must not necessarily be autologous. An inhibition of target cell migration can be seen with cells cultured without antigen for up to 3 days; with longer culture time, this effect is reduced or disappears. The effect of cells cultured with antigen, however, is equally strong irrespective of the culture time up to 1 week, and the most clearcut results will, therefore, be obtained after approximately 4 days culture. Also migration enhancement has been seen. Treatment of cells during the incubation with antigen and cycloheximide gives a dose-dependent blocking of the inhibiting effect. 5 patients were studied both before and after sensitization with DNCB: low concentrations of DNCB gave an inhibition and high concentrations an enhancement of the migration when the patients were sensitized. The technique is more sensitive and reproducible than the original Clausen technique. It is also suitable in studies where shortage of cells is a problem.