Emperipolesis--a peculiar feature of megakaryocytes as evaluated in chronic myeloproliferative diseases by morphometry and ultrastructure
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Abstract:
A combined morphometric and ultrastructural study was performed on so called emperipolesis or internal wandering of myeloid cells in the cytoplasm of large mature megakaryocytes. Measurements were made on material from a total of 115 patients comprising a normal control group and 5 groups with subtypes of chronic myeloproliferative diseases, including primary (essential, idiopathic) thrombocythemia (PTH). A significant increase in this peculiar phenomenon was noted in myeloproliferative disorders and especially in PTH where the frequency of emperipolesis showed a positive correlation with the number of anuclear cytoplasmic fragments sectioned, with the circular deviation of the shapes of megakaryocytes and with the extent to which the peripheral thrombocyte count was elevated. Electron microscopy in selected cases displayed the integrity of the plasma membranes of engulfed hematopoietic cells within the dilated cavities of the megakaryocytic demarcation membrane system (DMS) and no evidence of phagocytosis. Moreover there was a close relationship between engulfed myeloid cells and the presumptive sites of platelet shedding which had their openings from the cisternal lumina of the DMS. Our results demonstrate that emperipolesis of hematopoietic cells within megakaryocytes should not be regarded as a special nosological feature, but as an indication of enforced thrombocytogenetic activity which is expressed particularly in PTH.
Insights
Emperipolesis, myeloid cells within megakaryocytes, is increased in myeloproliferative disorders, especially primary thrombocythemia (PTH). This phenomenon indicates heightened platelet production activity, not a distinct disease feature.
Area of Science:
- Hematology
- Cell Biology
- Pathology
Background:
- Emperipolesis, the internal wandering of myeloid cells within megakaryocytes, is a poorly understood phenomenon.
- Its role in megakaryocyte function and platelet production requires further investigation.
Purpose of the Study:
- To investigate the occurrence and significance of emperipolesis in megakaryocytes.
- To correlate emperipolesis with specific myeloproliferative diseases, particularly primary thrombocythemia (PTH).
Main Methods:
- Combined morphometric and ultrastructural analysis of megakaryocytes from 115 patients.
- Inclusion of a normal control group and five groups with chronic myeloproliferative diseases, including PTH.
- Electron microscopy to examine cellular interactions and membrane integrity.
Main Results:
- Emperipolesis was significantly increased in myeloproliferative disorders, most notably in PTH.
- In PTH, emperipolesis frequency correlated positively with anuclear cytoplasmic fragments, megakaryocyte shape deviation, and elevated platelet counts.
- Ultrastructural analysis revealed intact myeloid cell membranes within the megakaryocytic demarcation membrane system (DMS), suggesting no phagocytosis.
Conclusions:
- Emperipolesis in megakaryocytes is not a distinct pathological entity.
- It serves as an indicator of increased, enforced platelet production activity, particularly prominent in primary thrombocythemia.