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An immunohistochemical study of the clearance of apoptotic cellular fragments
M P G Leers1, V Björklund, B Björklund
1Department of Pathology, Atrium Medical Center Heerlen, The Netherlands. m.leers@gozl.nl
Abstract:
We investigated the distribution and fate of apoptotic bodies during human development and in the adult, using an antibody (M30) that recognizes a neo-epitope formed early in the apoptotic cascade by caspase cleavage of cytokeratin 18. In the fetus, we found extensive accumulation of M30-positive, non-phagocytosed fragments in the red pulp of the spleen, subcutaneous and submucosal vessels, the interstitium of the lung, and the glomerular mesangium of the kidneys. In the liver, M30-immunoreactive fragments were found inside macrophages in the sinusoids. The number of these fragments and the intensity of the immunostaining increased with the gestational age of the fetus. In the adult, M30-positive fragments were barely detectable in normal tissues. However, many pathological situations, including both chronic degenerative processes and metastatic cancer, were associated with accumulation of M30-positive fragments in the red pulp of the spleen. In the liver and kidney, no fragments could be detected. Remarkably, 13 of the 16 patients with metastasized cancer showed pronounced accumulation of M30-positive fragments containing hematoxylin-reactive material in the red pulp of the spleen. In the non-cancerous cases, such DNA-containing fragments were only seen in 9 of 94 cases. The results show that when apoptotic activity is high, as during development in the fetus or during metastasis and other pathological processes in the adult, the phagocytic clearance of apoptotic bodies can be overloaded. These apoptotic fragments then accumulate in the spleen. The visual detection of apoptotic fragments is concluded to reflect increased cell turnover.
Insights
During human development and in pathological adult conditions, overloaded phagocytic clearance leads to the accumulation of apoptotic bodies in the spleen. This indicates increased cell turnover and provides a marker for disease states.
Area of Science:
- Cell Biology
- Developmental Biology
- Pathology
Background:
- Apoptosis is a crucial process for development and tissue homeostasis.
- Apoptotic bodies are cleared by phagocytes, but this process can be overwhelmed.
Purpose of the Study:
- To investigate the distribution and fate of apoptotic bodies during human development and in adults.
- To determine if apoptotic body accumulation serves as a marker for increased cell turnover and pathological conditions.
Main Methods:
- Utilized an antibody (M30) targeting caspase-cleaved cytokeratin 18 to detect early apoptotic fragments.
- Examined tissue samples from human fetuses and adults, including normal and pathological conditions (metastatic cancer).
- Assessed fragment distribution in spleen, liver, lung, kidney, and vessels using immunohistochemistry.
Main Results:
- Extensive accumulation of M30-positive fragments observed in fetal tissues (spleen, lung, kidney), increasing with gestational age.
- Fragments were largely absent in normal adult tissues but accumulated in the spleen red pulp in pathological states, notably metastatic cancer.
- 13/16 cancer patients showed significant splenic fragment accumulation, compared to 9/94 non-cancerous cases, with DNA-containing fragments observed.
Conclusions:
- High apoptotic activity, seen in fetal development and adult pathologies like cancer, can overload phagocytic clearance mechanisms.
- Accumulation of apoptotic bodies, particularly in the spleen, serves as a visual indicator of increased cell turnover.
- The M30 antibody is a valuable tool for detecting and quantifying apoptotic fragments in various physiological and pathological contexts.