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Characterization of testudine melanomacrophage linear, membrane extension processes--cablepodia--by phase and atomic
James C Johnson1, Saju R Nettikadan, Srikanth G Vengasandra
1Department of Microbiology, Des Moines University, Des Moines, Iowa 50312, BioForce Nanosciences Inc., 1615 Golden Aspen Drive, Suite 101, Ames, Iowa 50010, USA. james.johnson@dmu.edu
Abstract:
Melanomacrophages (MMs) are a component of an internal, pigmented cell system in liver and splenic tissues of some fishes, anurans, and reptiles. The cells have been found in centers or aggregates in sinusoids and are associated with cells capable of producing a peptide cytokine and immunoglobulins. A unique cell extension process has been observed in turtle MMs placed into cell culture, and this process has been studied by light and atomic force microscopy. These structures, referred to as cablepodia, are uniquely straight, narrow, and unbranching and appear to originate from growth cones opposite lamellipodia. Cablepodia were found to connect with other turtle MMs and fibroblasts forming cell networks. Dividing fibroblasts to which a cablepodium attached ceased cell division. The observations collectively suggest that a principal reason for aggregations of MMs in internal organs of lower vertebrates is their ability to form interconnected networks of cell processes for trapping and processing of particulate matter, cells, and infectious organisms and, possibly, for the communication of cell signals and transfer of intracellular materials.
Insights
Melanomacrophages (MMs) form networks using unique cable-like structures called cablepodia. These networks may trap particles and cells, suggesting a key role in immune function for lower vertebrates.
Area of Science:
- Cell Biology
- Immunology
- Comparative Vertebrate Anatomy
Background:
- Melanomacrophages (MMs) are pigmented cells found in the liver and spleen of various vertebrates.
- These cells are often aggregated and associated with immune functions, including cytokine and immunoglobulin production.
Purpose of the Study:
- To investigate the unique cellular structures and network-forming capabilities of turtle melanomacrophages in vitro.
- To elucidate the potential functional significance of melanomacrophage aggregations in lower vertebrates.
Main Methods:
- Observation of turtle melanomacrophages in cell culture using light and atomic force microscopy.
- Analysis of cell extension processes, termed cablepodia, and their interactions with other cells.
Main Results:
- Turtle melanomacrophages exhibit unique, straight, unbranching cell extensions called cablepodia originating from growth cones.
- Cablepodia form interconnected networks between melanomacrophages and fibroblasts.
- Attachment of cablepodia to dividing fibroblasts resulted in the cessation of fibroblast cell division.
Conclusions:
- Melanomacrophage aggregations may serve to form functional networks via cablepodia for trapping and processing of particulate matter and pathogens.
- These networks could play a role in intercellular communication and material transfer within the immune system of lower vertebrates.
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