Vasculature to the germinal matrix in rabbit pups

The Role of Oxidative Stress in the Progression of Secondary Brain Injury Following Germinal Matrix Hemorrhage

Germinal matrix hemorrhage (GMH) can be a fatal condition responsible for the death of 1.7% of all neonates in the USA. The majority of GMH survivors develop long-term sequalae with debilitating comorbidities. Higher grade GMH is associated with higher mortality rates and higher prevalence of comorbidities. The pathophysiology of GMH can be broken down into two main titles: faulty hemodynamic autoregulation and structural weakness at the level of tissues and cells. Prematurity is the most significant risk factor for GMH, and it predisposes to both major pathophysiological mechanisms of the condition. Secondary brain injury is an important determinant of survival and comorbidities following GMH. Mechanisms of brain injury secondary to GMH include apoptosis, necrosis, neuroinflammation, and oxidative stress. This review will have a special focus on the mechanisms of oxidative stress following GMH, including but not limited to inflammation, mitochondrial reactive oxygen species, glutamate toxicity, and hemoglobin metabolic products. In addition, this review will explore treatment options of GMH, especially targeted therapy.

Role of N-formyl peptide receptor 2 in germinal matrix hemorrhage: an intrinsic review of a hematoma resolving pathway

Germinal matrix hemorrhage is one of the leading causes of morbidity, mortality, and acquired infantile hydrocephalus in preterm infants in the United States, with little progress made in its clinical management. Blood clots have been shown to elicit secondary brain injury after germinal matrix hemorrhage, by disrupting normal cerebrospinal fluid circulation and absorption after germinal matrix hemorrhage causing post-hemorrhagic hydrocephalus development. Current evidence suggests that rapid hematoma resolution is necessary to improve neurological outcomes after hemorrhagic stroke. Various articles have demonstrated the beneficial effects of stimulating the polarization of microglia cells into the M2 phenotype, as it has been suggested that they play an essential role in the rapid phagocytosis of the blood clot after hemorrhagic models of stroke. N-formyl peptide receptor 2 (FPR2), a G-protein-coupled receptor, has been shown to be neuroprotective after stroke. FPR2 activation has been associated with the upregulation of phagocytic macrophage clearance, yet its mechanism has not been fully explored. Recent literature suggests that FPR2 may play a role in the stimulation of scavenger receptor CD36. Scavenger receptor CD36 plays a vital role in microglia phagocytic blood clot clearance after germinal matrix hemorrhage. FPR2 has been shown to phosphorylate extracellular-signal-regulated kinase 1/2 (ERK1/2), which then promotes the transcription of the dual-specificity protein phosphatase 1 (DUSP1) gene. In this review, we present an intrinsic outline of the main components involved in FPR2 stimulation and hematoma resolution after germinal matrix hemorrhage.

Germinal Matrix-Intraventricular Hemorrhage of the Preterm Newborn and Preclinical Models: Inflammatory Considerations

The germinal matrix-intraventricular hemorrhage (GM-IVH) is one of the most important complications of the preterm newborn. Since these children are born at a critical time in brain development, they can develop short and long term neurological, sensory, cognitive and motor disabilities depending on the severity of the GM-IVH. In addition, hemorrhage triggers a microglia-mediated inflammatory response that damages the tissue adjacent to the injury. Nevertheless, a neuroprotective and neuroreparative role of the microglia has also been described, suggesting that neonatal microglia may have unique functions. While the implication of the inflammatory process in GM-IVH is well established, the difficulty to access a very delicate population has lead to the development of animal models that resemble the pathological features of GM-IVH. Genetically modified models and lesions induced by local administration of glycerol, collagenase or blood have been used to study associated inflammatory mechanisms as well as therapeutic targets. In the present study we review the GM-IVH complications, with special interest in inflammatory response and the role of microglia, both in patients and animal models, and we analyze specific proteins and cytokines that are currently under study as feasible predictors of GM-IVH evolution and prognosis.

Characterization of acute brain injuries and neurobehavioral profiles in a rabbit model of germinal matrix hemorrhage

BACKGROUND AND PURPOSE

Germinal matrix hemorrhage-intraventricular hemorrhage (GMH-IVH) is the most common neurological problem of premature infants and has enormous financial and social impact. Despite this, there is no standardized animal model of IVH depicting acute brain injuries.

METHODS

We delivered rabbit-pups prematurely at 29-day gestation by C-section, administered intraperitoneal glycerol to the pups at 3-hour postnatal age to induce IVH, and evaluated the brain for evidence of injuries.

RESULTS

About 80% of glycerol-treated pups developed gross IVH. We found greater neutrophil and microglia infiltration around the ventricles (periventricular zone) in pups with IVH than in controls. We noted more apoptosis and neuronal degeneration in the periventricular zone than in the neocortex in pups with IVH, but not in controls. There was evidence of axonal damage revealed by beta-amyloid precursor protein and neurofilament immunolabeling. Neurobehavioral testing showed that pups with IVH were more wobbly with lesser capability to walk on inclination than pups without IVH. There was no evidence of acute systemic toxicity in the glycerol-treated pups. An evaluation of autopsy materials from premature infants revealed similar evidence of apoptosis and cellular infiltration in the periventricular zone in cases with IVH, but not in cases without IVH-suggesting clinical relevance of the model.

CONCLUSIONS

The study provides an instructive animal model of IVH with evidence of acute brain injuries that can be used to evaluate strategies in prevention of IVH and acute posthemorrhagic complications.

Cerebral microvascular architecture following experimental cold injury

The sequential changes in microvascular architecture following local cold injury in rat brains were studied post mortem by scanning electron microscopy and the vascular casting method. The findings were compared with the results of immunohistochemical studies of injured endothelial cells using the bromodeoxyuridine (BUdR) and anti-BUdR monoclonal antibody technique. Repair of the microvascular architecture had begun by the 3rd day after injury, with hematogenous cells and reactive astrocytes present in the edematous brain participating in the regenerative process. The normal microvascular architecture was reconstructed starting from the edge of the lesion nearest to the brain surface. On the other hand, in the most severely injured part of the brain surface, newly formed microvascular architecture appeared, resembling that of the developing fetal and newborn rat cortex. Seven days after injury, the entire microvascular architecture in the region of the lesion had been reconstructed.