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A Model of Germinal Matrix Hemorrhage in Preterm Rat Pups
Masako Jinnai1,2, Gabriella Koning1, Gagandeep Singh-Mallah1
1Department of Obstetrics and Gynecology, Centre of Perinatal Medicine, Health, Institute of Clinical Sciences, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden.
Insights
Researchers developed a new rat model for germinal matrix hemorrhage (GMH), a preterm infant brain injury. This model shows lasting neurological deficits, offering insights into preterm brain injury and potential treatments.
Area of Science:
- Neuroscience
- Developmental Biology
- Pathology
Background:
- Germinal matrix hemorrhage (GMH) is a severe complication in extremely preterm infants, often leading to neurological deficits and increased mortality.
- Understanding the pathophysiology of GMH is crucial for developing effective interventions for preterm brain injury.
Purpose of the Study:
- To develop and characterize a grade III and IV GMH model in postnatal day 5 (P5) rats, mimicking preterm human brain maturation.
- To assess the neuropathological and functional outcomes of this novel GMH model.
Main Methods:
- Postnatal day 5 Wistar rats received unilateral intracranial collagenase VII injections (0.1, 0.2, or 0.3 U) into the striatum near the germinal matrix.
- Motor functions, body weight, and neuropathology were assessed at various time points (P16, P22-26, P36-40) using behavioral tests and immunohistochemistry.
Main Results:
- A collagenase dose of 0.3 U successfully induced GMH, characterized by ventricular dilation, cellular necrosis, and atrophy in gray and white matter.
- GMH rats exhibited persistent brain infarction, astrogliosis, delayed eye opening, abnormal motor coordination, hyperactivity, and reduced anxiety compared to controls.
Conclusions:
- A reliable P5 rat model of collagenase-induced GMH has been established for studying preterm brain injury.
- This model demonstrates moderate gray and white matter injury with associated long-term neurological and behavioral deficits, providing a valuable tool for research.
Abstract:
Germinal matrix hemorrhage (GMH) is a serious complication in extremely preterm infants associated with neurological deficits and mortality. The purpose of the present study was to develop and characterize a grade III and IV GMH model in postnatal day 5 (P5) rats, the equivalent of preterm human brain maturation. P5 Wistar rats were exposed to unilateral GMH through intracranial injection into the striatum close to the germinal matrix with 0.1, 0.2, or 0.3 U of collagenase VII. During 10 days following GMH induction, motor functions and body weight were assessed and brain tissue collected at P16. Animals were tested for anxiety, motor coordination and motor asymmetry on P22-26 and P36-40. Using immunohistochemical staining and neuropathological scoring we found that a collagenase dose of 0.3 U induced GMH. Neuropathological assessment revealed that the brain injury in the collagenase group was characterized by dilation of the ipsilateral ventricle combined with mild to severe cellular necrosis as well as mild to moderate atrophy at the levels of striatum and subcortical white matter, and to a lesser extent, hippocampus and cortex. Within 0.5 h post-collagenase injection there was clear bleeding at the site of injury, with progressive increase in iron and infiltration of neutrophils in the first 24 h, together with focal microglia activation. By P16, blood was no longer observed, although significant gray and white matter brain infarction persisted. Astrogliosis was also detected at this time-point. Animals exposed to GMH performed worse than controls in the negative geotaxis test and also opened their eyes with latency compared to control animals. At P40, GMH rats spent more time in the center of open field box and moved at higher speed compared to the controls, and continued to show ipsilateral injury in striatum and subcortical white matter. We have established a P5 rat model of collagenase-induced GMH for the study of preterm brain injury. Our results show that P5 rat pups exposed to GMH develop moderate brain injury affecting both gray and white matter associated with delayed eye opening and abnormal motor functions. These animals develop hyperactivity and show reduced anxiety in the juvenile stage.
