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An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization
Published on: June 12, 2013
Modifications of sialidase activity during the monocyte-macrophage differentiation in vitro
C R Lambré1, A Greffard, L Gattegno
1INSERM, U 139, Hôpital H. Mondor, Créteil, France.
Abstract:
Human mononuclear cells were isolated from peripheral blood by centrifugation over Ficoll Hypaque, followed by adherence to plastic dishes. Monocyte-derived macrophages were obtained after culture for 3 or 5 days of the adherent cells in RPMI medium containing 20% heat-inactivated foetal calf serum. The sialidase activities were assayed in the whole homogenate using sodium 4-methyl-umbelliferyl-alpha-D-neuraminate as substrate, at various pHs, ranging from 3.6 to 6. The in vitro differentiation of monocytes into macrophages from day 0 up to day 5 was accompanied by a significant (P less than or equal to 0.01) increase in the sialidase activity on both a per-cell (+360%) and a per-mg protein in the homogenate (+125%) basis.
Insights
Human monocytes differentiate into macrophages, significantly increasing sialidase enzyme activity. This finding highlights changes in sialidase during monocyte to macrophage differentiation, crucial for cellular function.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Mononuclear cells from peripheral blood are precursors to various immune cells.
- Monocyte-derived macrophages play critical roles in immune responses and tissue homeostasis.
- Sialidase enzymes are involved in modifying cell surface glycans, impacting cellular functions.
Purpose of the Study:
- To investigate the changes in sialidase activity during the in vitro differentiation of human monocytes into macrophages.
- To quantify the increase in sialidase activity on a per-cell and per-mg protein basis during macrophage differentiation.
Main Methods:
- Isolation of human peripheral blood mononuclear cells using Ficoll-Hypaque density gradient centrifugation.
- Culture of adherent cells to induce differentiation into monocyte-derived macrophages over 3-5 days.
- Assay of sialidase activity in cell homogenates using a fluorogenic substrate (sodium 4-methyl-umbelliferyl-alpha-D-neuraminate) across a pH range of 3.6-6.
Main Results:
- A significant increase in sialidase activity was observed during monocyte to macrophage differentiation (P ≤ 0.01).
- Sialidase activity per cell increased by approximately 360% from day 0 to day 5.
- Sialidase activity per mg of protein in the homogenate increased by approximately 125% during the differentiation process.
Conclusions:
- In vitro differentiation of human monocytes into macrophages is associated with a substantial upregulation of sialidase activity.
- The observed increase in sialidase activity suggests a critical role for these enzymes in macrophage maturation and function.
- These findings provide insights into the biochemical changes accompanying monocyte-macrophage differentiation.
