Mesoderm-derived cells proliferate in the embryonic central nervous system: confocal microscopy and three-dimensional visualization.
In the chick and quail embryo, two cell populations migrate into the neural tube from the surrounding mesodermal tissues during the fourth day of incubation: individual cells which represent macrophages, and endothelial cells which remain continuous with the extraneural vessels. We report here on the proliferative capacity of these mesoderm-derived cells. A double-immunofluorescence protocol for two monoclonal antibodies of subtype IgG1, the endothelial cell/macrophage marker QH1, and the S-phase marker bromodeoxyuridine, was developed. With confocal laser scanning microscopy of thick microtome sections, labeling indices of intraneural individual QH1-positive cells (12%) and of endothelial cells (10%) were determined. In contrast, the labeling index of extraneural endothelial cells was 25%. With three-dimensional visualization of confocal data, the variable morphology of macrophages was shown. Our results indicate that: (1) proliferative activity of intraneural capillary endothelial cells is less than expected and that it is absent from sprouts; (2) both spheroidal and ramified macrophages proliferate inside the neural tissues; and (3) ramified macrophages frequently make contact with capillary endothelial cells. We conclude that most embryonic microglia may be derived from the early invasive QH1+ macrophages.
Cossmann
P H
PH
Anatomisches Institut, Lehrstuhl II, Albert-Ludwigs-Universität Freiburg, Germany.
Eggli
P S
PS
Christ
B
B
Kurz
H
H
D000818:Animals; D002455:Cell Division; D002469:Cell Separation; D002490:Central Nervous System / Q000166:cytology / Q000196:embryology*; D002642:Chick Embryo; D003370:Coturnix; D004261:DNA Replication; D004727:Endothelium / Q000166:cytology; D007091:Image Processing, Computer-Assisted; D008648:Mesoderm / Q000166:cytology*; D017628:Microglia / Q000166:cytology*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D013499:Surface Properties