Impact of Mesenchymal Stromal Cell Delivery Through Cardiopulmonary Bypass on Postnatal Neurogenesis

Abstract

Background: Neurodevelopmental impairment is an important challenge for survivors after neonatal surgery with cardiopulmonary bypass (CPB). The subventricular zone, where most neural stem/progenitors originate, plays a critical role in cortical maturation of the frontal lobe. Promoting neurogenesis in the subventricular zone is therefore a potential therapeutic target for preserving cortical growth. Mesenchymal stromal cells (MSCs) promote endogenous regeneration in the rodent brain. We investigated the impact of MSC delivery through CPB on neural stem/progenitor cells and neuroblasts (ie, young neurons) in the piglet subventricular zone.

Methods: Two-week-old piglets (n = 12) were randomly assigned to one of three groups: (1) control, (2) deep hypothermic circulatory arrest, and (3) circulatory arrest, followed by MSC administration. MSCs (10 × 10⁶ per kg) were delivered through CPB during the rewarming period. Neural stem/progenitors, proliferating cells, and neuroblasts were identified with immunohistochemistry at 3 hours after CPB.

Results: CPB-induced insults caused an increased proliferation of neural stem/progenitors (P < .05). MSC delivery reduced the acute proliferation. MSC treatment increased the number of neuroblasts in the outer region of the subventricular zone (P < .05) where they form migrating chains toward the frontal lobe. Conversely, the thickness of the neuroblast-dense band along the lateral ventricle was reduced after treatment (P < .05). These findings suggest that MSC treatment changes neuroblast distribution within the subventricular zone.

Conclusions: MSC delivery through CPB has the potential to mitigate effects of CPB on neural stem/progenitor cells and to promote migration of neuroblasts. Further investigation is necessary to determine the long-term effect of MSC treatment during CPB on postnatal neurogenesis.

Figure 1.

Magnified image of coronal section of the SVZ. Doublecortin stain. Scale bar, 200μm. SVZ, subventricular zone; DL-SVZ, dorsolateral-SVZ; V-SVZ, ventral-SVZ.

Figure 2.. CPB-induced insults result in an increased proliferation of SVZ NSPCs. MSC delivery mitigates acute proliferation. A-D

, SOX2⁺Ki67⁺ cells in dorsolateral-SVZ (A-C) and the entire SVZ (D). P value was determined by two-way ANOVA with Bonferroni comparisons.*p<0.05 vs. Control by unpaired Student’s t test. Data are shown as mean ± standard error of mean (n=4 each). Scale bar, 50μm. DHCA, deep hypothermic circulatory arrest; MSC, mesenchymal stromal cell; SVZ, subventricular zone.

Figure 3.. MSC treatment increases the number of neuroblasts within the outer SVZ (Tiers 2 and 3). A-D

, Dcx⁺ neuroblasts in Tier 2 and 3 within DL-SVZ (A-C) and both of DL and V-SVZ (D). P value was determined by two-way ANOVA with Bonferroni comparisons. *p<0.05 vs Control and DHCA; ^†p<0.05 vs Control by unpaired Student’s t test. Data are shown as mean ± standard error of mean (n=4 each). Scale bar, 50μm. DHCA, deep hypothermic circulatory arrest; MSC, mesenchymal stromal cell; Dcx, doublecortin; DL-SVZ, dorsolateral-subventricular zone; V-SVZ, ventral-subventricular zone.

Figure 4.. MSC treatment reduces the thickness of the dense neuroblasts band within the DL-SVZ. A-D

, Cell-dense band of Dcx⁺ neuroblasts along the walls of the lateral ventricle (dotty line) in DL-SVZ (A-C) and both of DL and V-SVZ (D). P value was determined by two-way ANOVA with Bonferroni comparisons. *p<0.05 vs Control by unpaired Student’s t test. Data are shown as mean ± standard error of mean (n=4 each). Scale bar, 50μm. DHCA, deep hypothermic circulatory arrest; MSC, mesenchymal stromal cell; Dcx, doublecortin; GFAP, glial fibrillary acidic protein; DL-SVZ, dorsolateral-subventricular zone; V-SVZ, ventral-subventricular zone.

Figure 5.. The number of neuroblast clusters are not altered at 3 hours after surgery. A-C

, Dcx⁺ neuroblast clusters in SVZ. D, Cluster number. P value was determined by one-way ANOVA with Bonferroni comparisons. Data are shown as mean ± standard error of mean (n=4 each). Scale bar, 200μm. DHCA, deep hypothermic circulatory arrest; MSC, mesenchymal stromal cell; Dcx, doublecortin; SVZ, subventricular zone; F, F ratio in the ANOVA.