Hyperbaric oxygen treatment promotes neural stem cell proliferation in the subventricular zone of neonatal rats with hypoxic-ischemic brain damage

Abstract

Hyperbaric oxygen therapy for the treatment of neonatal hypoxic-ischemic brain damage has been used clinically for many years, but its effectiveness remains controversial. In addition, the mechanism of this potential neuroprotective effect remains unclear. This study aimed to investigate the influence of hyperbaric oxygen on the proliferation of neural stem cells in the subventricular zone of neonatal Sprague-Dawley rats (7 days old) subjected to hypoxic-ischemic brain damage. Six hours after modeling, rats were treated with hyperbaric oxygen once daily for 7 days. Immunohistochemistry revealed that the number of 5-bromo-2'-deoxyuridine positive and nestin positive cells in the subventricular zone of neonatal rats increased at day 3 after hypoxic-ischemic brain damage and peaked at day 5. After hyperbaric oxygen treatment, the number of 5-bromo-2'-deoxyuridine positive and nestin positive cells began to increase at day 1, and was significantly higher than that in normal rats and model rats until day 21. Hematoxylin-eosin staining showed that hyperbaric oxygen treatment could attenuate pathological changes to brain tissue in neonatal rats, and reduce the number of degenerating and necrotic nerve cells. Our experimental findings indicate that hyperbaric oxygen treatment enhances the proliferation of neural stem cells in the subventricular zone of neonatal rats with hypoxic-ischemic brain damage, and has therapeutic potential for promoting neurological recovery following brain injury.

Keywords: brain injury; grants-supported paper; hyperbaric oxygen; hypoxic-ischemic brain damage; neonatal hypoxic-ischemic encephalopathy; neonatal rats; nestin; neural regeneration; neural stem cells; neurons; neuroregeneration; proliferation; subventricular zone.

Figure 1

Effect of hyperbaric oxygen (HBO) on pathological changes of brain tissue in neonatal rats with hypoxic-ischemic (HI) brain damage (hematoxylin-eosin staining, light microscope). (A) Control group showed normal brain structures and regularly arranged brain cells (× 40). (B) HI group showed disrupted tissue architecture at day 1 after modeling (× 40). (C) Large areas of cell necrosis and neuronal cell loss could be seen in the HI group at day 3 after modeling (× 400). (D) These pathological changes were improved in the HBO group at day 3 after modeling (× 400).

Figure 2

Effect of hyperbaric oxygen (HBO) on 5-bromo-2’-deoxyuridine expression in the subventricular zone of neonatal rats with hypoxic-ischemic (HI) brain damage (SABC immunohistochemistry staining, optical microscope, × 400). 5-Bromo-2’-deoxyuridine positive cell counts were higher in the HBO group than in the HI and control groups at each time point.

Figure 3

Effect of hyperbaric oxygen (HBO) on nestin expression in the subventricular zone of neonatal rats with hypoxic-ischemic (HI) brain damage (SABC immunohistochemistry staining, optical microscope, × 400). Hyperbaric oxygen treatment significantly increased the number of nestin positive cells. The number of nestin positive cells increased gradually at day 3 and peaked at day 5, and than began to decrease at day 14 and reached the lowest level at day 21.

Figure 4

Effect of hyperbaric oxygen (HBO) on the proliferation of neural stem cells in brain tissues of neonatal rats with hypoxic-ischemic (HI) brain damage. Data are expressed as the mean. HBO treatment significantly increased the number of 5-bromo-2’-deoxyuridine and nestin dual positive cells in brain tissue at day 1 after injury (P < 0.05) and peaked at day 5 (P < 0.05). The number of 5-bromo-2’-deoxyuridine and nestin dual positive cells began to increase from day 14, but more dual positive cells were seen in the HBO group than the HI and control groups.