Radiation Research · 1977 · 20 citations · 0 references
MedicineAnatomyPathologyHistologyMicroscopic AnatomyRadiobiologyCellular UltrastructureConnective TissueMicroscopic Cell MorphologyRabbit AnatomyRadiation BiologyVascular TissueBlood Vessel MorphologyCellular Radiation DamageRadiation Damage In Vascular TissueTissue Radiation InjuryVascular Injuries
Previous studies show vascular endothelium is highly radiosensitive, limiting endothelial proliferation as a primary repair mechanism at high doses. The study proposes that the cell aggregates formed after irradiation aid in repairing the microvasculature. Electron microscopy of rabbit ear chambers 7 days post‑irradiation (400–700 rad, 250 kVp) was used to characterize the cell types in the aggregates and their relationship to vascular repair. Aggregates of undifferentiated mesenchymal cells, often located beneath the endothelium, appear along vessel walls within days after irradiation, likely deriving from pericytes or interstitial mesenchymal cells rather than dedifferentiated smooth muscle.
Cell aggregates in increased numbers appear along blood vessel walls within a few days after local x irradiation of the tissue within rabbit ear chambers. At 7 days after irradiation with 400 or 700 rad of 250 kVp of x rays, electron microscopic studies of the microvasculature were carried out to determine the morphological characteristics of the cell types involved in the aggregates and the relation of these cells to vascular repair. The cell aggregates usually occur in the interstitial region subjacent to the endothelium. The cells that make up the aggregates show morphological characteristics of relatively undifferentiated mesenchymal cells; they have an irregularly rounded shape and contain large amounts of rough endoplasmic reticulum, Golgi vesicles, and mitochondria. In a few instances, cells of similar morphology also occur as part of the lining of the blood vessels. The perivascular cell aggregates may originate from the pericyte population or from undifferentiated mesenchymal cells that occur in the interstitial region surrounding blood vessels; it is improbable that they are dedifferentiated smooth muscle cells. It is suggested that the cells that make up these aggregates contribute to the repair of the microvasculation after radiation injury. The radiosensitivity of vascular endothelium reported by previousmore » investigators seems to preclude endothelial proliferation as the principal repair mechanism at higher radiation doses.« less