Vascularization of fetal cell suspension grafts in the excitotoxically lesioned adult rat thalamus.
Several studies have considered the establishment of vascularization in intracerebral solid transplants of neural tissue. The widely supported interpretation of the results is that the vascular network of the solid grafts is already present before implantation into the host brain. The situation is different when dissociated fetal tissue is transplanted as a cell suspension because in these conditions the fetal vascular network is disrupted. The present study has, therefore, been undertaken to follow the angiogenesis in a transplant of dissociated fetal cells implanted into the excitotoxically neuron-depleted thalamus. The vascular network is compared to that observed in the intact and in the lesioned thalamus both in terms of morphology of the capillaries and of the function of the blood-brain barrier (BBB). In the transplant, capillaries, stained by Indian ink, are very few in number and have very fine calibers during the first 20 days after grafting. Some structures can be identified as immature blood vessels at the electron microscopic level. The blood vessels are progressively more numerous in the graft and they demonstrate mature ultrastructural features 2 months after grafting. Last, there is no leakage of the BBB for peroxidase. The vascularization seems to follow a pattern of maturation comparable to that described during development in the literature. In contrast, in the lesioned area, there is a reactive angiogenesis: 10 days after the excitotoxic injection (shortest time studied), there are many wide caliber vessels with expanded perivascular spaces engorged with mesodermal cells. A microvascularization also develops transiently during the first two months. Capillaries are abnormal from the functional point of view, since there is a leakage of the BBB to macromolecules. The use of an experimental model in which transplant had to grow in a lesioned area permits to determine two types of vascularization: an apparently normal developmental timetable, normal morphological and functional characteristics, in the transplant; a reactive angiogenesis, in the lesioned area.
Dusart
I
I
Unité de Recherches de Neurophysiologie Pharmacologique, Paris, France.
Nothias
F
F
Roudier
F
F
Besson
J M
JM
Peschanski
M
M
D000818:Animals; D002469:Cell Separation; D002560:Cerebrovascular Circulation; D005260:Female; D005333:Fetus; D006085:Graft Survival; D009389:Neovascularization, Pathologic; D051381:Rats; D011919:Rats, Inbred Strains; D013788:Thalamus / Q000098:blood supply / Q000166:cytology / Q000637:transplantation*; D013997:Time Factors