Study of Megakaryocytes From Patients With Abnormal Platelet Vesicles
Condition: Blood Coagulation Disorders
MeSH terms: Hemostatic Disorders; Blood Coagulation Disorders
Study type: Observational

Summary: 
      Congenital bleeding disorders characterized by abnormal platelet granules include Gray
      Platelet syndrome (GPS; defective alpha-granules), Hermansky-Pudlak syndrome (HPS; defective
      delta-granules), and combined alpha delta-storage pool deficiency (alpha delta-SPD). Other
      diseases associated with variable defects in platelet gamma-granules include Chediak-Higashi,
      Griscelli, Wiskott-Aldrich, and Thrombocytopenia Absent Radius syndromes. These disorders are
      models for the study of organelle formation in megakaryocytes and platelets. Characteristics
      of megakaryocytopoiesis in these disorders have not been investigated because megakaryocytes
      could not be cultured from patients in sufficient quantities for experimental purposes.
      Recent advances have made it possible to culture megakaryocytes using serum-free media
      supplemented with recombinant human thrombopoietin (TPO). Such cultured human megakaryocytes,
      amplified from bone marrow-derived CD34+ stem cells, synthesize and store organellar proteins
      and produce functional platelets. In this protocol, we plan to obtain bone marrow aspirates
      from 40 children and adults (ages 2 to 80 years) with GPS, HPS, and related disorders.
      Patients admitted to the NIH Clinical Center on specific disease-related protocols will be
      enrolled in this protocol during their routine 3-5 day visits. We will culture megakaryocytes
      from CD34+ stem cells isolated from bone marrow aspirates. Studies of cultured megakaryocytes
      will include evaluation of granule membrane and soluble proteins using fluorescent antibodies
      and immunoelectron microscopy and comparison of RNA and protein expression patterns between
      normal and patient cells. Precautions will be taken to prevent the primary risk of the bone
      marrow aspiration, i.e., prolonged bleeding at the aspiration site. Standard diagnostic
      studies on the bone marrow sample may reveal information that may directly benefit patients.
      However, the broader benefit of this study is the acquisition of a better understanding of
      the characteristics of functional platelet disorders and the process of intracellular vesicle
      formation.
    

Detailed description: 
      Congenital bleeding disorders characterized by abnormal platelet granules include Gray
      Platelet syndrome (GPS; defective alpha-granules), Hermansky-Pudlak syndrome (HPS; defective
      delta-granules), and combined alpha delta-storage pool deficiency (alpha delta-SPD). Other
      diseases associated with variable defects in platelet gamma-granules include Chediak-Higashi,
      Griscelli, Wiskott-Aldrich, and Thrombocytopenia Absent Radius syndromes. These disorders are
      models for the study of organelle formation in megakaryocytes and platelets. Characteristics
      of megakaryocytopoiesis in these disorders have not been investigated because megakaryocytes
      could not be cultured from patients in sufficient quantities for experimental purposes.
      Recent advances have made it possible to culture megakaryocytes using serum-free media
      supplemented with recombinant human thrombopoietin (TPO). Such cultured human megakaryocytes,
      amplified from bone marrow-derived CD34+ stem cells, synthesize and store organellar proteins
      and produce functional platelets. In this protocol, we plan to obtain bone marrow aspirates
      from 40 children and adults (ages 2 to 80 years) with GPS, HPS, and related disorders.
      Patients admitted to the NIH Clinical Center on specific disease-related protocols will be
      enrolled in this protocol during their routine 3-5 day visits. We will culture megakaryocytes
      from CD34+ stem cells isolated from bone marrow aspirates. Studies of cultured megakaryocytes
      will include evaluation of granule membrane and soluble proteins using fluorescent antibodies
      and immunoelectron microscopy and comparison of RNA and protein expression patterns between
      normal and patient cells. Precautions will be taken to prevent the primary risk of the bone
      marrow aspiration, i.e., prolonged bleeding at the aspiration site. Standard diagnostic
      studies on the bone marrow sample may reveal information that may directly benefit patients.
      However, the broader benefit of this study is the acquisition of a better understanding of
      the characteristics of functional platelet disorders and the process of intracellular vesicle
      formation.
    

Keywords: Gray Platelet Syndrome; Hermansky-Pudlak Syndrome; Storage Pool Deficiency; Organelle Formation; Megakaryocyte Development; Megakaryocytes; Platelets; Dense Granules; Alpha Granules; Lysosome-related Organelles; GPS; HPS; Griscelli Disease; Chediak Higashi Syndrome; Wiskott Aldrich Syndrome; Platelet; Congenital Bleeding Disorders; SAC; Vesicle