Wnt signaling enhances neurogenesis and improves neurological function after focal ischemic injury - PubMed (original) (raw)

Wnt signaling enhances neurogenesis and improves neurological function after focal ischemic injury

Adi Shruster et al. PLoS One. 2012.

Abstract

Stroke potently stimulates cell proliferation in the subventricular zone of the lateral ventricles with subsequent neuroblast migration to the injured striatum and cortex. However, most of the cells do not survive and mature. Extracellular Wnt proteins promote adult neurogenesis in the neurogenic niches. The aim of the study was to examine the efficacy of Wnt signaling on neurogenesis and functional outcome after focal ischemic injury. Lentivirus expressing Wnt3a-HA (LV-Wnt3a-HA) or GFP (LV-GFP) was injected into the striatum or subventricular zone of mice. Five days later, focal ischemic injury was induced by injection of the vasoconstrictor endothelin-1 into the striatum of the same hemisphere. Treatment with LV-Wnt3a-HA into the striatum significantly enhanced functional recovery after ischemic injury and increased the number of BrdU-positive cells that differentiated into mature neurons in the ischemic striatum by day 28. Treatment with LV-Wnt3a-HA into the subventricular zone significantly enhanced functional recovery from the second day after injury and increased the number of immature neurons in the striatum and subventricular zone. This was accompanied by reduced dissemination of the neuronal injury. Our data indicate that Wnt signaling appears to contribute to functional recovery after ischemic injury by increasing neurogenesis or neuronal survival in the striatum.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. Schematic representation of the experimental design.

A. Experimental protocol. B. Diagram of the brain section. Lentiviral vector was injected into either the striatum (blue syringe) or SVZ (red syringe). The ischemic area in the striatum is circled in black.

Figure 2

Figure 2. In vitro and in vivo validation of LV-Wnt3a-HA over-expression.

A–C. HeLa cells were infected with LV-Wnt3a-HA and confirmation of over-expression was performed using Western blot analysis (A) and immunocytochemistry (C). The ability of Wnt3a-HA to functionally activate Wnt signaling was confirmed by assessing active β-catenin (A) followed by densitometry measurements (B). Cells infected with non-related virus (NRV) were used as control. D. In vivo expression of exogenous Wnt3a-HA was detected one month after injection in the striatum.

Figure 3

Figure 3. Effect of LV-Wnt3a-HA treatment on functional recovery.

A–B. LV-Wnt3a-HA injection into the striatum significantly improved functional performance at 28 days after injury on the cylinder test (A; p<0.05) but not on the corner test (B). C–D. LV-Wnt3a-HA treatment into the SVZ significantly improved functional recovery from day 2 after injury on the cylinder test (C; p<0.05) and on day 21 after injury on the corner test (D; p<0.05). Data are given as mean ± SEM.

Figure 4

Figure 4. Effect of Wnt3a-HA treatment on neurogenesis 28 days after injury.

A. A co-localized BrdU/NeuN cell is shown in the striatum. B–D. Wnt3a-HA injection into the striatum led to a significant increase in the number of newborn neurons in the striatum (p<0.01). Treatment with Wnt3a-HA into the SVZ did not change the number of newborn neurons in the striatum. Number of newborn neurons (B), proliferating progenitors (C) and NeuN+/BrdU+ (D) cells in the striatum and SVZ.

Figure 5

Figure 5. Effect of LV-Wnt3a-HA injection into the SVZ on the proliferation and differentiation of progenitor cells to neuroblasts 2 days after injury.

A. EdU+ and DCX+ cells were detected in the ischemic striatum. B-D. Wnt3a-HA significantly increased the number of DCX+ cells in the striatum (p<0.01). EdU+DCX+ cells were hardly detected in the striatum. Number of newborn DCX+ (B), proliferating progenitors (C) and DCX+/EdU+ (D) cells in the striatum. E. EdU+ and DCX+ cells were found in the SVZ. D-H. Wnt3a-HA significantly increased the number of DCX+ and EdU+DCX+ cells in the SVZ (p<0.01). Number of newborn DCX+ (F), proliferating progenitors (G) and DCX+/EdU+ (H) cells in the SVZ.

Figure 6

Figure 6. Neuroprotection in the ischemic striatum following LV-Wnt3a-HA injection into the SVZ 2 days after injury.

A. DNA strand breaks are labeled by TUNEL staining and NeuN immunohistochemistry in the ischemic striatum. B. Wnt3a-HA significantly reduced the number of DNA fragmented cells in the striatum (p<0.05). C. DCX+ cells manifest extensive expression of BDNF in the ischemic striatum. D. Quantification of BDNF levels in the striatum using ELISA (p<0.05).

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