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Immunochemical localisation of proliferating cells in mussel digestive gland tissue
I Marigómez1, X Lekube, I Cancio
1Biologia Zelularra Atala, Zoologia eta Animali Zelulen Dinamika Saila, Euskal Herriko Unibertsitatea, Bilbo/Basque Country, Spain.
Insights
Proliferating cell nuclear antigen (PCNA) is present in all digestive gland cell types of young mussels, indicating widespread cell proliferation. This challenges the idea of a single stem cell in mussel digestive epithelia.
Area of Science:
- Marine biology
- Cell biology
- Immunohistochemistry
Background:
- The digestive gland of Mytilus galloprovincialis is crucial for nutrient absorption and processing.
- Understanding cell proliferation patterns is key to comprehending tissue regeneration and organismal health.
- Previous hypotheses suggested a single stem cell model for digestive epithelia.
Purpose of the Study:
- To investigate the distribution and characteristics of proliferating cells in the mussel digestive gland.
- To identify the specific cell types exhibiting proliferative activity using immunochemical techniques.
- To compare cell proliferation in young versus old mussel specimens.
Main Methods:
- Immunohistochemistry using PC10 monoclonal antibody against proliferating cell nuclear antigen (PCNA).
- Immunoblot analysis of digestive gland homogenates.
- Paraffin sectioning and electron microscopy for cellular localization.
Main Results:
- PCNA was detected in mussel digestive gland homogenates, with a distinct band size (36-37 kDa).
- Young mussels showed higher PCNA signals, suggesting increased proliferative activity compared to older individuals.
- PCNA immunoreactivity was observed in nuclei of all cell types within the digestive epithelia and circulating hemocytes, with higher intensity in digestive cells.
Conclusions:
- The capacity for proliferation is distributed among all cell types in the digestive diverticula of Mytilus galloprovincialis.
- These findings do not support the existence of a single stem cell in this epithelium.
- Unlike crabs, mussels lack discrete regions of cell proliferation in their digestive glands.
Abstract:
The distribution of proliferating cells in the digestive gland of the common marine mussel, Mytilus galloprovincialis Lmk, was investigated by means of immunochemical techniques employing PC10, a commercial monoclonal antibody to the proliferating cell nuclear antigen (PCNA). Immunoblot analysis of digestive gland whole homogenates revealed a single crossreactive band of 36-37 kDa, identical to the corresponding protein of rat liver and murine melanoma cells. A band of slightly higher electrophoretic mobility (34-35 kDa) was found in fish liver. In mussel digestive gland, the samples obtained from young specimens presented a more intense signal for PCNA than in those obtained from old mussels, suggesting that the digestive gland cells of young mussels exhibit a higher proliferative activity. In paraffin sections, PC10 specifically labelled nuclei of all cell types, but only a smaller number of cells lining the different digestive epithelia. PCNA expression was more intense in digestive cells than in basophilic cells. Hemocytes circulating along the interdiverticular spaces also presented immunoreactive nuclei. Electron microscopy revealed a specific and moderate PC10 labelling in nuclei. Thus, single gold particles appeared disseminated throughout the nuclei with accumulations of particles in the sites of DNA replication. Taken together, these data reveal that the capacity to proliferate resides within all cell types in the digestive diverticula and do not support the hypothesis of the existence of one stem cell in this epithelium. As opposed to the hepatopancreas of the crab, Carcinus maenas, where mitotic figures and PCNA immunoreactivity are only observed in the embryonic cells within the distal portions of the digestive diverticula, apparently there are not discrete regions of cell proliferation in the digestive gland of mussels.
