Ultrastructural study of phagocytic activities of young astrocytes in injured neonatal rat brain following intracerebral injection of colloidal carbon

Abstract

The cellular reaction to injury in the mature central nervous system (CNS) has been extensively studied in both man and animals, while a detailed study of the reaction of the immature CNS to injury is lacking in the literature. This study was undertaken to elucidate the response of young astrocytes following injection injury to developing brain. Colloidal carbon was applied because it is a suitable marker for phagocytosis, it is nontoxic, and it is readily identifiable by light and electron microscopy. The cerebral cortex of the neonatal rat was injected with 0.1 microliter of colloidal carbon solution. The animals were allowed to survive from 1 hour to 30 days postoperation. The brains were fixed by vascular perfusion and processed for light and electron microscopy. Carbon particles were ingested in membrane-bound vacuoles and sequestered in lysosomes of young astrocytes. Astrocytes, loaded with carbon particles, were identified after 4 days, and were seen in abundance between 10 to 21 days postoperation. Carbon-laden astrocytes were seen in the immediate vicinity of the site of the injection; in the surrounding, apparently normal, neuropil; and in the perivascular regions. This study demonstrates the ability of young astrocytes to engulf foreign particles injected into the developing brain. The presence of carbon particles in astrocytes located further away from the site of injection is discussed.

Reactive astrocytes function as phagocytes after brain ischemia via ABCA1-mediated pathway

“…However, here is growing evidence that non-professional phagocytes can also participate in that process 8, 13 . Previous studies have shown the presence of degenerated axons and apoptotic neurons in astrocytes in injured brains 14–16 . Additionally, recent studies have shown that optic nerve head astrocytes constitutively engulf axonal materials, even under normal physiological conditions 17, 18 .…”

In vivo labeling of adult neural progenitors for MRI with micron sized particles of iron oxide: Quantification of labeled cell phenotype

“…Indeed the labeling of microglia with many particles and the fact that some astrocytes have many MPIOs indicate that this is potentially occurring throughout the migration pathway. Astrocytes have been shown to have phagocytotic properties in both culture and rodent experiments (Al-Ali et al, 1988; Watabe et al, 1989). Experiments co-labeling progenitors with BrdU and MPIOs or using a recently developed fluorescence technique that labels the cells that first take up MPIOs (Sumner et al, 2007) will enable distinguishing labeled progenitors that have differentiated from cells that have taken up MPIOs from dying cells.…”

Regulators of phagocytosis as pharmacologic targets for stroke treatment

“…Mechanistically, it has been shown that genes involved in engulfment, such as phagocytic receptors and opsonins, are enriched in astrocytes in the developing forebrain ( Cahoy et al, 2008 ). Moreover, degenerated axons and apoptotic neurons have been detected in astrocytes in injured brains ( Al-Ali et al, 1988 ; Loov et al, 2012 ). Astrocytes are highly responsive and change their phenotype into “reactive astrocytes” in response to brain damage ( Anderson et al, 2016 ).…”