Integrin α4 Overexpression on Rat Mesenchymal Stem Cells Enhances Transmigration and Reduces Cerebral Embolism After Intracarotid Injection.

BACKGROUND AND PURPOSE: Very late antigen-4 (integrin α4ß1)/vascular cell adhesion molecule-1 mediates leukocyte trafficking and transendothelial migration after stroke. Mesenchymal stem cells (MSCs) typically express integrin ß1 but insufficient ITGA4 (integrin α4), which limits their homing after intravascular transplantation. We tested whether ITGA4 overexpression on MSCs increases cerebral homing after intracarotid transplantation and reduces MSC-borne cerebral embolism. METHODS: Rat MSCs were lentivirally transduced to overexpress ITGA4. In vitro transendothelial migration was assessed using a Boyden chamber assay. Male Wistar rats intracarotidly received 0.5×106 control or modified MSCs 24 hours after sham or stroke surgery. In vivo behavior of MSCs in the cerebral vasculature was observed by intravital microscopy and single-photon emission computed tomography for up to 72 hours. RESULTS: Transendothelial migration of ITGA4-overexpressing MSCs was increased in vitro. MSCs were passively entrapped in microvessels in vivo and occasionally formed large cell aggregates causing local blood flow interruptions. MSCs were rarely found in perivascular niches or parenchyma at 72 hours post-transplantation, but ITGA4 overexpression significantly decreased cell aggregation and ameliorated the evoked cerebral embolism in stroke rats. CONCLUSIONS: ITGA4 overexpression on MSCs enhances transendothelial migration in vitro, but not in vivo, although it improves safety after intracarotid transplantation into stroke rats.

Increased protein expression levels of pCREB, BDNF and SDF-1/CXCR4 in the hippocampus may be associated with enhanced neurogenesis induced by environmental enrichment.

Brain plasticity is very sensitive to the environment. Certain neurotrophic factors and neurotransmitter receptors, including brain-derived neurotrophic factor (BDNF), cyclic adenosine monophosphate response element­binding protein (CREB), stromal cell­derived factor­1 (SDF­1) and its specific receptor, C-X-C motif chemokine receptor 4 (CXCR4), are important in neurogenesis in adult animals. In the present study, the effects of environmental enrichment (EE) on neurogenesis in the dentate gyrus (DG) and subventricular zone (SVZ), and the protein expression levels of BDNF, CREB, SDF­1 and CXCR4 were investigated. Adult rats were randomly assigned as controls or underwent EE for 30 days. Subsequently, immunofluorescence staining was used to analyze cell proliferation in the DG and SVZ, and the differentiation and survival of newly­formed cells in the hippocampus. The protein expression levels of BDNF, phosphorylated CREB (pCREB), protein kinase A catalytic subunit α, SDF­1 and CXCR4 in the hippocampus were assayed by western blotting. Cognitive function was assessed in a Morris water maze. EE improved cognitive function, and increased the proliferation, differentiation and survival of newly­formed neurons in the DG of adult rats; however, EE did not activate neurogenesis in the SVZ. Furthermore, EE enhanced the protein expression levels of BDNF, pCREB, SDF-1 and CXCR4 in the hippocampus. These results provide a theoretical basis to explain the beneficial effects of EE on healthy, adult rats.

Contrasting effects of tetraethylammonium and 4-aminopyridine on the gastrointestinal function of mice.

Many different K+ channels have been identified in the gastrointestinal tract, and the two classical K+ channel blockers, tetraethylammonium and 4-aminopyridine, show different sensitivity for these channels. The aim of the present study was to compare the effects of tetraethylammonium and 4-aminopyridine on the gastrointestinal function of mice. 4-Aminopyridine (5 mg/kg, p.o.) inhibited, but tetraethylammonium (40 mg/kg, p.o.) enhanced, the intestinal propulsion of a charcoal suspension in conscious mice. Studies in vitro showed that perfusion of 5 mM 4-aminopyridine increased the maximal contractile force and minimal relaxation force, and decreased the amplitude and frequency of the peristaltic contraction of the isolated duodenum. However, perfusion of 5 mM tetraethylammonium increased the maximal contractile force, the minimal relaxation force and the amplitude of the contraction. The effects of tetraethylammonium and 4-aminopyridine on the duodenal contraction could be abolished completely by application of 5 microM verapamil. Our results in vivo and in vitro showed that tetraethylammonium and 4-aminopyridine had contrasting effects on the gastrointestinal function of mice.