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Updated: Jul 8, 2026
Modeling Encephalopathy of Prematurity Using Prenatal Hypoxia-ischemia with Intra-amniotic Lipopolysaccharide in Rats
Published on: November 20, 2015
[Expression of F-actin and RhoA in experimental hypoxic-ischemic white matter damage in premature SD rats]
Jin-Hui Li1, Yu-Jia Yao, Jing Shi
1Department of Neonatology, West China Second Hospital, Sichuan University, Chengdu 610041, China.
Insights
Hypoxia-ischemia in preterm infants causes white matter damage (WMD) by altering F-actin distribution and increasing RhoA mRNA expression. These changes in cell structure and signaling contribute to long-term neurological deficits in premature infants.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Context:
- White matter damage (WMD) is a significant complication in preterm infants.
- Hypoxia-ischemia (HI) is a primary cause of WMD, leading to long-term neurological deficits.
- The role of F-actin and RhoA in the neuropathology of WMD is not well understood.
Purpose:
- To investigate the changes in F-actin distribution and RhoA mRNA expression following hypoxia-ischemia (HI) in a rat model of preterm white matter damage.
- To elucidate the potential mechanisms by which F-actin and RhoA contribute to the pathogenesis of WMD.
Summary:
- HI in 2-day-old rats induced significant pathological and ultrastructural changes in white matter, establishing a valid WMD model.
- F-actin showed redistribution from the cell membrane to the cytoplasm post-HI, correlating with increased non-integrity of cells.
- RhoA mRNA expression significantly increased after HI, peaking at 48 hours, suggesting its involvement in F-actin redistribution.
Impact:
- This study reveals that F-actin redistribution and RhoA upregulation are key events in the development of white matter damage following HI.
- Understanding these molecular mechanisms provides potential targets for therapeutic interventions to mitigate WMD in preterm infants.
- The findings highlight the complex cellular responses to ischemic injury and their long-term consequences on brain development.
Objective:
White matter damage (WMD) in preterm infants is a well-recognized serious complication of prematurity. The collapse of cell skeleton of growth cone after hypoxia-ischemia (HI) is considered as the basic neuropathologic change of the long-term residuals of premature white matter damage. F-actin is the major component of cell skeleton and maintains the normal form of cells, its function and potential mechanism of WMD have not been reported. In this study, changes of F-actin and its influencing factor RhoA were investigated.
Methods:
Totally 184 Sprague-Dawley (SD) rats (age 2 days, body weight 6 to 8 grams) were randomly divided into 14 groups: 7 different time WMD groups (HI 12 h, 24 h, 48 h, 72 h, 7 d, 14 d, 28 d) and 7 corresponding control groups. The 2 day-old SD rats were subjected to ligation of right carotid artery (ischemia), and then they were put into a box full with 6% oxygen and 94% nitrogen for 4 hours (hypoxia). The light microscopy was used to observe the brain pathological changes and the electron microscopy was used to detect the brain ultrastructural changes after hypoxia and ischemia. Eighty SD rats were used for flurescent-immunohistochemical method to detect the distribution of F-actin in cell membrane and cytoplasm of both WMD groups and the control groups at 12 h, 24 h, 48 h, 72 h, 7 d after HI respectively. The distribution of F-actin was reflected by the percentage of non-integrity cells. Another 80 SD rats were used for real time RT-PCR to detect the expression of RhoAmRNA in the white matter tissue of both WMD groups (HI 12 h, 24 h, 48 h, 72 h, 7 d) and the control groups.
Results:
(1) Necrosis of lateral ventricle tissue was observed by 72 h after HI. Dilatation of ventricle and formation of capsular space beneath white matter had been observed by 14 d after HI. (2) Disregulation, pyknosis, mitochondrion swelling and chromatin agglutination were observed in WMD groups. The maldevelopment of myelins in WMD groups was detected at 1 h after HI. (3) The fluorescent stains decreased on cellular membrane, but increased in cytoplasm with time. The percentage of non-integrity cells was significantly higher (P < 0.05) in HI groups (0.32 +/- 0.04, 0.43 +/- 0.04, 0.56 +/- 0.03, 0.65 +/- 0.04, 0.87 +/- 0.03) than the controls (0.02 +/- 0.01, 0.02 +/- 0.01, 0.01 +/- 0.01, 0.02 +/- 0.01, 0.02 +/- 0.01). (4) The expression of RhoA mRNA was significantly increased (P < 0.05) in HI groups (1.205, 2.415, 4.830, 1.500) in the white matter tissue compared with the controls (0.300, 0.375, 0.375, 0.530) at 12 h, 24 h, 48 h, 72 h after HI. The expression of RhoA mRNA reached the peak value at HI 48 h, and then gradually decreased. The expression of RhoA mRNA at HI 7 d in WMD group (0.500) was not significantly different from the control (P > 0.05).
Conclusion:
(1) The pathological and ultrastructural changes of white matter in WMD groups after HI suggest that the WMD model was successfully set up in premature 2 days SD rats. (2) F-actin is redistributed within cells after HI: expression in membrane is decreased and expression in plasma was increased. The redistribution possibly results in the collapse and retraction of cells. (3) The expression of RhoA mRNA is increased significantly after HI, which may lead to the redistribution of F-actin. (4) The increase of the expression of RhoA mRNA is not persistent, but the redistribution of F-actin is continued, which suggests that RhoA may not be the only factor affecting the redistribution of F-actin.
