Related Experiment Video
Updated: Jun 2, 2026
05:58
Proplatelet Formation Dynamics of Mouse Fresh Bone Marrow Explants
Published on: May 20, 2021
Thrombocytogenesis by megakaryocyte; Interpretation by protoplatelet hypothesis
Goro Kosaki1, Junichi Kambayashi
1Department of Gastroenterological Surgery and Clinical Oncology, Osaka University Medical School, Suita, Osaka, Japan.
Summary
Human megakaryocytes (MKs) undergo polyploidization and maturation, organizing cytoplasmic compartments via microtubules. These compartments mature into protoplatelets, ultimately releasing platelets through MK rupture.
Area of Science:
- Cell Biology
- Hematology
- Microscopy
Background:
- Megakaryocytes (MKs) are large bone marrow cells responsible for platelet production.
- MK polyploidization is a key feature of their maturation process.
- The precise mechanisms of platelet formation within MKs are complex and not fully elucidated.
Purpose of the Study:
- To visualize and describe the dynamic process of human megakaryocyte maturation and polyploidization.
- To elucidate the role of cellular structures, such as microtubules and centrosomes, in platelet formation.
- To detail the sequential events leading to platelet demarcation and release.
Main Methods:
- Serial transmission electron microscopy (STEM) was employed to observe human megakaryocytes at high resolution.
- Dynamic changes in organelle characteristics and cellular organization were tracked during differentiation.
- Microtubule organization and centrosome behavior were analyzed in relation to cytoplasmic compartmentalization.
Main Results:
- Human megakaryocytes exhibit polyploidization, with high ploidy levels (e.g., 32N) associated with numerous centrosomes.
- Microtubule bundles originating from centrosomes organize distinct cytoplasmic compartments (PCCs).
- Platelet demarcation membrane (DM) formation occurs between PCCs, leading to protoplatelet development and subsequent platelet release.
Conclusions:
- The study provides a detailed ultrastructural view of human megakaryocyte maturation and polyploidization.
- Microtubules and centrosomes play critical roles in organizing the cytoplasm for platelet production.
- The findings clarify the sequential steps from cytoplasmic compartmentalization to the final release of platelets from megakaryocytes.
Related Concept Videos
01:18Structure and Function of Platelets
The cell fragments known as platelets are disc-shaped, with an average diameter of about 3 μm and a thickness of roughly 1 μm. They play a crucial role in the body's vascular clotting system, which also involves plasma proteins, blood cells, and blood vessel tissues.
Platelets are continually replenished, circulating in the bloodstream for 9-12 days before being removed by phagocytes, primarily in the spleen. A microliter of circulating blood contains between 150,000 and 450,000 platelets, with...
Platelets are continually replenished, circulating in the bloodstream for 9-12 days before being removed by phagocytes, primarily in the spleen. A microliter of circulating blood contains between 150,000 and 450,000 platelets, with...
01:22Formation of the Platelet Plug
The platelet phase, the second stage of hemostasis, commences around 15-20 seconds after an injury. It follows and overlaps with the vascular phase, during which blood vessels constrict to minimize blood loss.
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...
01:16Clot Retraction and Fibrinolysis
After a fibrin clot is formed, the next step is clot retraction, a vital process facilitated by platelet contractile proteins, such as actin and myosin. These proteins pull the fibrin strands closer together and condense the clot. This action reduces the size of the clot, creating a smaller, denser structure that effectively seals off the damaged vessel. Clot retraction consolidates the clot and helps with wound healing by bringing the edges of the damaged blood vessel closer together.
01:34Production of Formed Elements
Hemangioblasts are multipotent stem cells originating from the mesoderm. They give rise to hematopoietic stem cells (HSCs), which undergo hematopoiesis to produce all the formed elements of blood. This process is regulated by a complex network of hematopoietic growth factors, including transcription factors, growth factors, and cytokines. These factors stimulate the HSCs to divide and differentiate, though some HSCs remain undifferentiated to maintain a self-renewing pool.
Most HSCs commit to...
Most HSCs commit to...
01:05Introduction to Hemostasis
Hemostasis is a complex physiological process that prevents excessive bleeding when a blood vessel is injured. It's crucial for maintaining the integrity of the circulatory system, as it ensures that our blood remains fluid while still within the vascular network and yet clots to prevent blood loss upon vessel injury.
The three phases of hemostasis involve many clotting factors present in plasma and several substances released by platelets and injured tissue cells. It is a fast, localized, and...
The three phases of hemostasis involve many clotting factors present in plasma and several substances released by platelets and injured tissue cells. It is a fast, localized, and...
01:20Extrinsic and Intrinsic Pathways of Hemostasis
Blood clotting or coagulation involves extrinsic and intrinsic pathways, which ultimately merge into the common pathway, forming a fibrin clot.
The Extrinsic Pathway
The extrinsic pathway of coagulation is typically initiated by tissue damage that exposes blood to tissue factor (TF), a protein released by the damaged tissue cells outside the blood vessels—this interaction with TF triggers biochemical reactions involving specific clotting factors. The key player here is Factor VII, which forms a...
The Extrinsic Pathway
The extrinsic pathway of coagulation is typically initiated by tissue damage that exposes blood to tissue factor (TF), a protein released by the damaged tissue cells outside the blood vessels—this interaction with TF triggers biochemical reactions involving specific clotting factors. The key player here is Factor VII, which forms a...