The fate and fine structure of fragments of blood vessels in CNS tissue cultures.

Abstract

Explants from spinal cord, brain stem, cerebellum and cerebral cortex of 5–18 weeks old human embryos and newborn rats were cultivated for 2–30 days. Most of the blood vessel fragments in the explant showed a rather normal structure of their wall even after 30 days in vitro. However, the number of small vessels was reduced. The lumen of most vessels was not collapsed and in some cases filled with cell debris. The endothelial cells remained connected by terminal bars, contained many vesicles and vacuoles of varying size and osmiophilic inclusions of cell debris. While in large vessels the endothelium was always present, in some small vessels near the edge of the explant it was absent. Here, glial endfeet made contact with a basal lamina, which enclosed varying amounts of cell debris. Pericytes were rarely observed after more than 10 days in vitro. Although the perivascular astroglial sheath disintegrated during the first few days in vitro, it was reconstructed and, after about 10 days in vitro, became more complete and differentiated than it was at the time of explantation. Many glial endfeet contained aggregated osmiophilic inclusions. At these sites the perivascular glial sheath and the adhering basal lamina often were discontinuous. The basal laminae were well developed, but disintegrated where the glial sheath was discontinuous. It is concluded that in vitro vessel fragments may be preserved without normal function and basal laminae survive without endothelium.