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Centrioles, microtubules and microfilaments in activated mononuclear and multinucleate macrophages from rat
Abstract:
In male Wistar rats of the BD I strain, mononuclear macrophages and multinucleate giant cells obtained from the peritoneum 1 day to 5 weeks after implantation of coverslips coated with dermoid cyst sebum, were examined by light microscopy and immunofluorescence microscopy, using antibodies specific for actin and tubulin and also by scanning and transmission electron microscopy. In activated mononuclear macrophages, microtubules radiate from the centrioles, situated in the perinuclear area, into the cytoplasm and the major cell processes. Microfilaments form a dense meshwork beneath the plasmalemma. When mononuclear macrophages fuse to form multinucleate giant cells, the initially unordered ("Foreign body") syncytia still reveal the original distribution patterns of centrioles, microtubules and microfilaments similar to those seen in the individual cells. In the ordered (Langhans) multinucleate giant cell all centrioles are accumulated in a main pluricorpuscular central group. Centrioles are the initiating and organising centres in the formation of microtubules. From the centrioles microtubules extend into the entire cytoplasm of the syncytium as a uniformly organised, stellate, radial system. The centrosphere, which is characteristic for ordered multinucleate giant cells, seems free from microfilaments, which form a ring-shaped woven network encircling the nuclei. Depolymerisation and inhibition of microtubules upon exposure to colchicine, indicates that both the organisation of the cytoplasm and the cellular movements depend on the undisturbed coordination of centrioles, microtubules and microfilaments. This applies also to the fusion of mononuclear macrophages to form syncytia, the ordering processes within multinucleate giant cells, and the function of ordered giant cells.
Insights
Cellular structures like centrioles, microtubules, and microfilaments are crucial for macrophage function and fusion. Their coordinated organization dictates cytoplasmic structure, cell movement, and giant cell formation.
Area of Science:
- Cell Biology
- Immunology
Background:
- Mononuclear macrophages are key immune cells involved in phagocytosis and inflammatory responses.
- Multinucleate giant cells form through the fusion of macrophages, playing roles in tissue repair and foreign body reactions.
Purpose of the Study:
- To investigate the ultrastructural organization of cytoskeletal components (microtubules and microfilaments) and centrioles in mononuclear macrophages and multinucleate giant cells.
- To elucidate the role of these components in macrophage activation, fusion, and the formation of different types of giant cells.
Main Methods:
- Light microscopy and immunofluorescence microscopy using antibodies for actin and tubulin.
- Scanning and transmission electron microscopy.
- In vivo study using Wistar rats with implanted coverslips coated with dermoid cyst sebum.
Main Results:
- Activated macrophages show microtubules radiating from perinuclear centrioles and subplasmalemmal microfilaments.
- Foreign body giant cells retain initial cytoskeletal organization, while Langhans giant cells exhibit a central accumulation of centrioles.
- Centrioles act as microtubule organizing centers, forming a radial system in giant cells.
- Microfilaments form a network encircling nuclei in ordered giant cells.
Conclusions:
- The coordination of centrioles, microtubules, and microfilaments is essential for cytoplasmic organization, cellular movement, and macrophage fusion.
- These cytoskeletal elements play a critical role in the formation and functional organization of multinucleate giant cells.