Capillary regeneration following thermal lesions in the mouse cerebral cortex

Summary Cold lesions were induced in the parietal cortex of 20 mice and capillary revascularisation of the necrotic zone in the subsequent four weeks was observed by light and electron microscopy. During the second week after injury, capillaries grew into the lesion from the thickened pia. Each vessel was covered by several thin lamellae of pial cell and was accompanied by bands of collagen.Capillaries which grew into the necrotic zone from the surrounding brain during the 2nd–3rd weeks after injury were all surrounded by astrocyte processes; there was also a pericapillary space which contained pericyte processes and a few collagen fibres. Lacunae lined by basement membrane and surrounded by processes of one or more astrocytes were observed during the early stages of revascularisation. Each lacuna contained a few collagen fibrils together with cell processes which were similar to the pericyte processes around regenerated capillaries. Cells resembling immature endothelial cells were occasionally seen within the lacunae.The hypotheses proposed here are, that the regenerating capillaries grow through or along the astrocyte lacunae and that the course of capillary regeneration is in this way influenced and guided by the astrocytes.