Light- and electron-microscopic study on the maturation of the primary portal plexus during the perinatal period in rats
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Capillary development in rat brains during the perinatal period was examined. Researchers found that endothelial cell division drives vascular growth, leading to increased capillary function and patency.
Area of Science:
- Neuroscience
- Developmental Biology
- Vascular Biology
Background:
- The primary portal plexus in rats is crucial for brain development.
- Understanding capillary maturation during the perinatal period is vital for comprehending neurodevelopmental processes.
Purpose of the Study:
- To investigate the microstructural changes in rat primary portal plexus capillaries during the perinatal period.
- To elucidate the cellular mechanisms underlying capillary development and maturation in the developing rat brain.
Main Methods:
- Light and electron microscopy were employed to examine capillary morphology.
- Quantitative analysis of capillary number and structural features was performed.
Main Results:
- Capillary number, including those invading nervous tissue (capillary loops), significantly increased with age.
- Capillary loops were identified as early as the 18th fetal day.
- Endothelial cell mitosis was identified as the primary driver of vascular growth, with immature capillaries maturing into patent vessels with increased organelle concentration and microvilli.
Conclusions:
- Capillary maturation involves endothelial cell proliferation and differentiation, leading to increased metabolic activity and patency.
- These changes are critical for establishing functional vascularization in the rat brain during the perinatal period.
Abstract:
The maturation of the capillaries of the primary portal plexus in rats during the perinatal period has been studied light- and electron-microscopically. The number of capillaries covering the median eminence and of those invading the nervous tissue (capillary loops) increases significantly with age. Capillary loops were observed as early as the 18th fetal day. The mitotic divisions of the endothelial cells within the preexisting capillaries seem to be the main reason for the vascular growth. Immature capillaries with a characteristic narrow lumen are surrounded by a fuzzy basal lamina; their wall is formed by a generally expanded endothelium with rather sparse organelles and inclusions, and by minute flattened areas. The maturation of the capillary results in a progressive spread of flattened endothelium followed by an enlargment of the capillary lumen. Moreover, a rising concentration of organelles and inclusions, relatively numerous luminal microvilli, and a dense and uniform basal lamina become noticeable as capillary differentiation proceeds. These data are thought to reflect the progressive increase in the metabolic activity of the endothelium as well as the establishment of capillary patency during the perinatal period of rats.