A morphological and functional study on the development and regeneration of lymphatic vessels.

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The development and regeneration of lymphatic vessels have been investigated using morphological and functional approaches. In order to identify lymphatic capillaries and proliferating cells in situ, a mouse monoclonal antibody against rat lymphatics (B27) and a technique for double immunostaining of proliferating cell nuclear antigen (PCNA) with other markers have been employed.(1) Development of rat lymphatics ; During fetal stages, lymphatics have been poorly developed. Within a half day after birth, large molecules such as carbon particles were taken up into central lacteals of the small intestine. After 24 hrs, however, no carbon particle was detected in the lymphatics and the morphological development and proliferation of lymphatics followed after the development of blood capillary networks.(2) Regeneration of rat lymphatics ; The ligation of the thoracic duct or removal of lymph nodes caused severe lymph edema and cell infiltration in the first few days, and then resulted in loc … More al adhesion after several days. The proliferation of lymphatic endothelial cells and the formation of newly formed lymphatics usually occurred after the local changes. However, B27-positive immature mesenchymal cells might play an initial role in the development of so called 'extravaskularen Saftbahnen' (Kihara, 1951) for absorption of tissue fluids during the early pathological stages.(3) Effect of growth factors on lymphatic endothelial cells ; Effects of epidermal cell growth factor (ECGF) and basic fibroblast growth factor (b-FGF) on lymphatic endothelial cells have been examined in vitro. Comparing with blood endothelial cells, the effects of both factors were not so great for the proliferation and morphological changes of lymphatic endothelial cells.These results suggest that lymphatics develop and regenerate supplementarily following the changes in blood vessels, but that the function of the lymphatics in terms of the absorption of tissue fluids, particularly at the early stages, may not reflect their immature appearance. Less