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Phagocytosis by muscle cells
Abstract:
Electron microscopy of intact tissue and cultured smooth muscle suggested the occurrence of phagocytosis of necrotic cells by normal vascular smooth muscle cells. Phagocytosis was further studied in vitro in muscle cells from guinea pig aorta, guinea pig vas deferens, and striated muscle from chick embryo by light and electron microscopy. The uptake of yeast cells (approximately 2-mum. diameter) into living cultured smooth muscle cells from guinea pig aorta was observed with phase contrast microscopy and differential interference (Nomarski) optics. Periodic acid-Schiff staining showed the yeast cells lined up in the cytoplasm of the muscle cells. Electron microscopy confirmed the uptake of yeast cells by differentiated muscle cells. Some of the yeast in the smooth muscle cells showed signs of disintegration suggesting digestion within the phagosome. Spontaneously contracting cultured smooth, cardiac and skeletal muscle cells incubated with latex spheres (0.3-mum. diameter) showed uptake and sequestration of the spheres. The ability of muscle cells to phagocytose necrotic cells and other particulate matter may be important in atherogenesis and in the repair of tissue after injury.
Insights
Normal smooth muscle cells can engulf necrotic cells and other particles through phagocytosis. This finding is significant for understanding vascular smooth muscle cell function in atherogenesis and tissue repair.
Area of Science:
- Cell Biology
- Vascular Biology
- Histology
Background:
- Vascular smooth muscle cells (VSMCs) play critical roles in cardiovascular health and disease.
- The potential for VSMCs to engage in phagocytosis, a key immune-related cellular process, has been largely unexplored.
- Understanding VSMC functions beyond contraction is crucial for advancing cardiovascular research.
Purpose of the Study:
- To investigate the phagocytic capabilities of vascular smooth muscle cells.
- To determine if smooth muscle cells can internalize and process foreign particulate matter and necrotic cells.
- To explore the implications of VSMC phagocytosis in the context of atherogenesis and tissue repair.
Main Methods:
- Electron microscopy was used to examine intact tissue and cultured smooth muscle cells.
- In vitro phagocytosis assays were performed using cultured smooth muscle cells (guinea pig aorta, vas deferens) and chick embryo striated muscle.
- Yeast cells and latex spheres were used as particulate matter, with observation via phase contrast microscopy, Nomarski optics, and Periodic acid-Schiff staining.
Main Results:
- Electron microscopy provided evidence of phagocytosis of necrotic cells by vascular smooth muscle cells in situ.
- Cultured smooth muscle cells successfully internalized yeast cells, which showed signs of disintegration, suggesting intracellular digestion.
- Smooth, cardiac, and skeletal muscle cells demonstrated uptake and sequestration of latex spheres.
Conclusions:
- Vascular smooth muscle cells possess the ability to perform phagocytosis, engulfing necrotic cells and other particulate materials.
- This phagocytic capacity suggests a novel role for smooth muscle cells in maintaining vascular homeostasis and responding to injury.
- The findings highlight the potential importance of smooth muscle cell phagocytosis in the pathogenesis of atherosclerosis and tissue regeneration processes.