Related Experiment Video
Updated: Jul 19, 2026
Megakaryocyte Differentiation and Platelet Formation from Human Cord Blood-derived CD34+ Cells
Published on: December 27, 2017
Transendothelial migration of megakaryocytes in response to stromal cell-derived factor 1 (SDF-1) enhances platelet
T Hamada1, R Möhle, J Hesselgesser
1Division of Hematology-Oncology, Cornell University Medical College, New York 10021, USA.
Abstract:
Although thrombopoietin has been shown to promote megakaryocyte (MK) proliferation and maturation, the exact mechanism and site of platelet formation are not well defined. Studies have shown that MKs may transmigrate through bone marrow endothelial cells (BMEC), and release platelets within the sinusoidal space or lung capillaries. In search for chemotactic factor(s) that may mediate transmigration of MKs, we have discovered that mature polyploid MKs express the G protein-coupled chemokine receptor CXCR4 (Fusin, LESTR). Therefore, we explored the possibility that stromal cell-derived factor 1 (SDF-1), the ligand for CXCR4, may also induce transendothelial migration of mature MKs. SDF-1, but not other CXC or CC chemokines, was able to mediate MK migration (ED50 = 125 pmol/liter). The MK chemotaxis induced by SDF-1 was inhibited by the CXCR4-specific mAb (12G5) and by pertussis toxin, demonstrating that signaling via the G protein-coupled receptor CXCR4 was necessary for migration. SDF-1 also induced MKs to migrate through confluent monolayers of BMEC by increasing the affinity of MKs for BMEC. Activation of BMEC with interleukin 1beta resulted in a threefold increase in the migration of MKs in response to SDF-1. Neutralizing mAb to the endothelial-specific adhesion molecule E-selectin blocked the migration of MKs by 50%, suggesting that cellular interaction of MKs with BMEC is critical for the migration of MKs. Light microscopy and ploidy determination of transmigrated MKs demonstrated predominance of polyploid MKs. Virtually all platelets generated in the lower chamber also expressed CXCR4. Platelets formed in the lower chamber were functional and expressed P-selectin (CD62P) in response to thrombin stimulation. Electron microscopy of the cells that transmigrated through the BMEC monolayers in response to SDF-1 demonstrated the presence of intact polyploid MKs as well as MKs in the process of platelet formation. These results suggest that SDF-1 is a potent chemotactic factor for mature MKs. Expression of CXCR4 may be the critical cellular signal for transmigration of MKs and platelet formation.
Insights
Stromal cell-derived factor 1 (SDF-1) induces megakaryocyte (MK) migration and platelet formation by activating the CXCR4 receptor. This process involves MKs transmigrating through bone marrow endothelial cells (BMEC), suggesting a key mechanism for platelet release.
Area of Science:
- Hematology
- Cell Biology
- Molecular Biology
Background:
- Thrombopoietin promotes megakaryocyte (MK) proliferation and maturation, but platelet formation mechanisms and sites remain unclear.
- Megakaryocytes (MKs) may transmigrate through bone marrow endothelial cells (BMEC) to release platelets in vascular spaces.
- Mature polyploid MKs express the chemokine receptor CXCR4, suggesting a role in migration.
Purpose of the Study:
- To investigate stromal cell-derived factor 1 (SDF-1) as a chemotactic factor for mature MKs.
- To determine if SDF-1 induces transendothelial migration of MKs and platelet formation.
- To elucidate the role of CXCR4 and interactions with bone marrow endothelial cells (BMEC) in this process.
Main Methods:
- Assessed MK migration in response to SDF-1 and other chemokines.
- Utilized CXCR4-specific monoclonal antibody (mAb) and pertussis toxin to study signaling pathways.
- Examined MK transmigration through BMEC monolayers, with and without interleukin-1beta activation.
- Investigated the role of E-selectin in MK-BMEC interactions using neutralizing mAbs.
- Analyzed transmigrated MKs and generated platelets using light and electron microscopy, and functional assays.
Main Results:
- SDF-1 potently mediated MK migration via CXCR4 signaling, independent of other chemokines.
- SDF-1 induced MK transmigration through BMEC monolayers, enhanced by interleukin-1beta and involving E-selectin.
- Transmigrated cells included polyploid MKs and MKs undergoing platelet formation.
- Generated platelets were functional, expressed P-selectin upon stimulation, and expressed CXCR4.
Conclusions:
- SDF-1 is a potent chemotactic factor for mature MKs, driving their transendothelial migration.
- CXCR4 expression on MKs is critical for SDF-1-mediated transmigration and subsequent platelet formation.
- This pathway highlights a significant mechanism for platelet release within vascular compartments.
Related Concept Videos
01:01Regulation of Hematopoietic Stem Cells
01:17Intracellular Signaling Affects Focal Adhesions
Some...
01:18Structure and Function of Platelets
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
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...