The events which occur during differentiation along the megakaryocyte-platelet axis will be studied, with emphasis on isolation and characterization of factors which enhance megakaryocyte proliferation and maturation. To facilitate screening of preparations of megakaryocyte colony stimulating factors (meg-CSAs), a rapid quantitative assay for in vitro megakaryocyte growth will be developed using megakaryocyte-platelet membrane specific radiolabeled monoclonal antibodies in a liquid marrow culture technique. Semi-solid medium marrow culture assays will be used to standardize the liquid assay, and to allow evaluation of individual colonies. Rich sources of meg-CSA(s) will be sought among various cell supernatants, cell extracts and patient samples, and individual factors then will be isolated by conventional biochemical separation techniques. Polyclonal and monolonal antibodies will be raised against isolated factors. These antibodies will be used to facilitate further isolations, and to develop radioimmunoassays to be used in patient studies. Isolated meg-CSA(s) will be characterized as to structure, specific cells of origin, and target cells. Coagulation proteins and mature platelets will be tested for a role in feedback regulation of megakaryopoiesis. Rigorous characterization of one discrete regulatory factor in megakaryopoiesis, and the ability to quantitate it in patients, will expand our understanding of clinical disorders in which specific controls of megakaryopoiesis are either inadequate or ineffective and lead to thrombocytopenia or thrombocytosis despite normal numbers of red blood cells and white blood cells.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08HL001607-03
Application #
3081998
Study Section
Research Manpower Review Committee (MR)
Project Start
1985-07-01
Project End
1990-06-30
Budget Start
1987-07-01
Budget End
1988-06-30
Support Year
3
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of Vermont & St Agric College
Department
Type
Schools of Medicine
DUNS #
066811191
City
Burlington
State
VT
Country
United States
Zip Code
05405
Kelm Jr, R J; Hair, G A; Mann, K G et al. (1992) Characterization of human osteoblast and megakaryocyte-derived osteonectin (SPARC). Blood 80:3112-9
Villarreal, X C; Grant, B W; Long, G L (1991) Demonstration of osteonectin mRNA in megakaryocytes: the use of the polymerase chain reaction. Blood 78:1216-22
Griffin, C G; Grant, B W (1990) Effects of recombinant interferons on human megakaryocyte growth. Exp Hematol 18:1013-8
Grant, B W; Nichols, W L; Solberg, L A et al. (1987) Quantitation of human in vitro megakaryocytopoiesis by radioimmunoassay. Blood 69:1334-9