Site- and stage-dependent differences in vascular density of the human fetal brain

Less information is available about site-dependent differences in fetal intrabrain angiogenesis. Quantitative evaluation is especially limited, with the measured area limited to the cerebral gray and white matters and the periventricular germinal matrix.

We measured vascular density (number of vessels per square millimeter) and percent vascular area (percentage of areas occupied by vessels) of CD34-positive microvessels in 14 human fetal brains, including 4 fetuses at 14-16 weeks of gestation, 5 at 25-28 weeks, and 5 at 35-37 weeks. Site-dependent differences were examined among the cerebral cortex, thalamus, internal capsule, corpus callosum, ganglionic eminence, midbrain, and cerebellar cortex and nuclei.

The parameters examined tended to be high in the cerebral germinal matrix, thalamus, midbrain, and cerebellum. Significant site-dependent differences were observed: lower vascular densities were observed in the internal capsule and corpus callosum than in other parts of the brain (p < 0.05) and a larger percent area was observed in the cerebellar nuclei than in other areas. Vascular density was higher during the early than late stage because of the larger numbers of CD34-positive islands of cells in the early stage, although there were several exceptions. Percent area was not stage dependent but was almost constant at many sites.

Consequently, except for developing nuclei, the prenatal development of intrabrain vessels after 15 weeks may proceed without any significant changes in density.