Isolation of circulating megakaryocytes in man

Area of Science:

• Hematology
• Cell Biology
• Physiology

Background:

• Megakaryocytes (MKs) are crucial for platelet production but are present in low numbers in normal blood, making their isolation challenging.
• Understanding the distribution and characteristics of circulating MKs is important for comprehending platelet biogenesis and related physiological processes.

Purpose of the Study:

• To develop and validate a filtration method for the efficient isolation of circulating megakaryocytes (MKs) from blood.
• To characterize the different types of MKs found in peripheral, central, and umbilical blood vessels.

Main Methods:

• A modified filtration system using 5-micron polycarbonate membranes was employed to isolate MKs from whole blood.
• Blood samples from peripheral veins, central veins, and umbilical arteries/veins were processed through the filtration system.
• Isolated MKs were identified and classified into four types based on the presence and amount of visible cytoplasm using May Grünwald-Giemsa staining.

Main Results:

• The filtration technique successfully retained MKs while allowing most other blood cells to pass through.
• Four distinct types of MKs were identified, categorized by increasing cytoplasmic volume (Type 1 to Type 4).
• Type 4 MKs, with abundant cytoplasm, were more frequently found in central venous and umbilical cord blood compared to peripheral venous blood.

Conclusions:

• Filtration through polycarbonate membranes is an effective method for isolating circulating megakaryocytes (MKs).
• The presence and types of MKs observed support the hypothesis of platelet production occurring in the placenta during fetal development and subsequently in the pulmonary circulation.
• This technique provides a valuable tool for studying circulating MKs as a normal physiological component of blood.