Neural stem cells and new neurons in the cerebral cortex of stroke-prone spontaneously hypertensive rats after stroke

Non-invasive remote ischemic postconditioning stimulates neurogenesis during the recovery phase after cerebral ischemia

Ischemic postconditioning (IPostC) has been reported to have neuroprotection against ischemic diseases, and one cycle of IPostC induces neurogenesis when treated nearby. To expanding these effects, we explored the effects of repetitively remote IPostC (NRIPostC) on neurogenesis in the subgranular zone (SGZ) and subentricular zone (SVZ) during stroke recovery. Animals underwent transient cerebral ischemia were treated with vehicle or NRIPostC immediately after reperfusion. Neurological severity scores, infarct size, neurogenesis, and protein expression levels of nestin and GFAP were quantified at 3d, 7d, 14d, 21d and 28d post-ischemia. Results showed that NRIPostC significantly reduced acute infarction and improved neurological outcomes during the recovery phase. Meanwhile, NRIPostC significantly increased the number of BrdU⁺/nestin⁺ cells in SGZ on day 14 and in the SVZ on days 3, 7 and 14 respectively, and the number of DCX⁺ cells from days 3 to 14. There were significant increments in the number of BrdU⁺/NeuN⁺ and BrdU⁺/GFAP⁺ cells in the SGZ and SVZ during the stroke recovery. The changing tendency of the protein expression of nestin and GFAP in DG was consistent with the result mentioned above. In conclusion, NRIPostC reduced acute infarction and improved functional outcomes up to 28d, and it induced neurogenesis both in the SGZ and SVZ.

Functional electrical stimulation-facilitated proliferation and regeneration of neural precursor cells in the brains of rats with cerebral infarction

Previous studies have shown that proliferation of endogenous neural precursor cells cannot alone compensate for the damage to neurons and axons. From the perspective of neural plasticity, we observed the effects of functional electrical stimulation treatment on endogenous neural precursor cell proliferation and expression of basic fibroblast growth factor and epidermal growth factor in the rat brain on the infarct side. Functional electrical stimulation was performed in rat models of acute middle cerebral artery occlusion. Simultaneously, we set up a placebo stimulation group and a sham-operated group. Immunohistochemical staining showed that, at 7 and 14 days, compared with the placebo group, the numbers of nestin (a neural precursor cell marker)-positive cells in the subgranular zone and subventricular zone were increased in the functional electrical stimulation treatment group. Western blot assays and reverse-transcription PCR showed that total protein levels and gene expression of epidermal growth factor and basic fibroblast growth factor were also upregulated on the infarct side. Prehensile traction test results showed that, at 14 days, prehension function of rats in the functional electrical stimulation group was significantly better than in the placebo group. These results suggest that functional electrical stimulation can promote endogenous neural precursor cell proliferation in the brains of acute cerebral infarction rats, enhance expression of basic fibroblast growth factor and epidermal growth factor, and improve the motor function of rats.

Vascular and parenchymal lesions along with enhanced neurogenesis characterize the brain of asymptomatic stroke-prone spontaneous hypertensive rats

BACKGROUND AND OBJECTIVES

Spontaneously hypertensive stroke-prone rats (SHRSPs) develop hypertension, cerebrovascular abnormalities and a stroke phenotype in association with higher levels of proteinuria. Here, we focus on cerebral abnormalities preceding lesions detectable by MRI.

METHODS

Longitudinal assessment of brain histology was performed in salt-loaded male SHRSPs (n = 26) and Wistar-Kyoto (WKY) normotensive control animals (n = 27). Groups of rats were sacrificed at different time points: Time 0, before the salt diet administration; Time 1, when proteinuria achieved 40 mg/day; Time 2, when proteinuria exceeded 100 mg/day.

RESULTS

At Time 0, no brain lesions were observed. At Time 1, changes of the cortical penetrating arteries, vasogenic oedema, lacunae and focal cell loss appeared in SHRSPs and worsened at Time 2, although no lesions were yet detected by MRI. Staining for proliferation markers revealed a significant boost of cellular mitosis in the subventricular zone (SVZ) of SHRSPs. Moreover, we observed higher immunopositivity for nestin, glial fibrillary acidic protein and doublecortin (markers for neural stem cells, astrocytes and immature neurons, respectively). At Time 2, apoptotic caspase-3 as well as 4-hydroxynonenal-positive neurons were associated to decreased nestin and doublecortin staining. High expression levels of glial fibrillary acidic protein were maintained in the SVZ. No comparative alterations and SVZ activation were recorded in WKYs.

CONCLUSION

Appearance of vascular changes in SHRSPs, before any MRI-detectable brain lesion, is coupled to active neural proliferation in the SVZ. With disease progression, only newborn astrocytes can survive, likely because of the neurotoxicity triggered by brain oedema and oxidative stress.

Stem cells from human exfoliated deciduous tooth-derived conditioned medium enhance recovery of focal cerebral ischemia in rats

Regenerative therapy using stem cells is a promising approach for the treatment of stroke. Recently, we reported that dental pulp stem cells (DPSC) ameliorated ischemic tissue injury in the rat brain and accelerated functional recovery after middle cerebral artery occlusion (MCAO). In this study, we investigated the effects of stem cells from human exfoliated deciduous tooth (SHED)-derived conditioned medium (SHED-CM) on permanent MCAO (pMCAO). Adult male Sprague-Dawley rats were subjected to pMCAO. SHED-CM were then administered intranasally, and the motor function and infarct volume were evaluated. Neurogenesis and vasculogenesis were determined using immunochemical markers. The SHED-CM group had more positive signals than the Dulbecco's modified Eagle's medium group, with doublecortin (DCX), neurofilament H, neuronal nuclei, and rat endothelial cell antigen observed in the peri-infarct area. Migration of neuronal progenitor cells (NPC) with DCX from the subventricular zone to the peri-infarct area was observed on days 6 and 16, with migration on day 6 being the most prominent. In conclusion, SHED-CM promoted the migration and differentiation of endogenous NPC, induced vasculogenesis, and ameliorated ischemic brain injury after pMCAO as well as transplantation of DPSC.

Exercise increases neural stem cell proliferation surrounding the area of damage following rat traumatic brain injury

Exercise enhances neuronal stem cell (NSC) proliferation and neurogenesis. However, the effect of exercise on NSC proliferation surrounding the area of damage after traumatic brain injury (TBI) is unknown. Here, we investigate the effect of running on NSC proliferation following TBI in the rat. Wistar rats received TBI and were randomly divided into two groups: (1) non-exercise group and (2) exercise group. The exercise group ran on a treadmill for 30 min/day at 22 m/min for 7 consecutive days. Immunohistochemistry was used to monitor NSC proliferation around the damaged area, and ex vivo techniques were used to isolate NSCs from the damaged region in both groups. The number of nestin- and Ki67-positive cells observed at 3 and 7 days after TBI was significantly greater in the exercise group than in the non-exercise group (P < 0.01). Furthermore, most nestin-positive cells in the exercise group co-localized with Ki67-positive cells. In ex vivo studies, spheres could be isolated from injured brain tissue from the exercise group at 3 and 7 days following TBI, but at only 3 days in the non-exercise group. The number of spheres isolated from injured brain tissue was greater in the exercise group than in the non-exercise group. Spheres were immunopositive for nestin and comprised NSCs that could differentiate into neurons and glia. Exercise increases the proliferation of NSCs around the damaged area following TBI. Therefore, exercise therapy (rehabilitation) in the early phase following TBI is important for recuperation from cerebral dysfunction induced by TBI.