Autocrine Communication; Endothelial Growth Factors/metabolism; Hematopoietic Stem Cells/cytology; Hematopoietic Stem Cells/metabolism; Lymphokines/metabolism; Animals; Autocrine Communication/drug effects; Cell Division/drug effects; Cell Membrane Permeability; Cell Survival/drug effects; Cells, Cultured; Clone Cells/cytology; Clone Cells/drug effects; Clone Cells/metabolism; Endothelial Growth Factors/antagonists & inhibitors; Endothelial Growth Factors/genetics; Endothelium, Vascular/cytology; Endothelium, Vascular/drug effects; Endothelium, Vascular/metabolism; Flow Cytometry; Gene Deletion; Hematopoiesis/drug effects; Hematopoietic Stem Cells/drug effects; Humans; Lymphokines/antagonists & inhibitors; Lymphokines/genetics; Mice; Mice, Knockout; Paracrine Communication; Proto-Oncogene Proteins/agonists; Proto-Oncogene Proteins/antagonists & inhibitors; Proto-Oncogene Proteins/metabolism; Proto-Oncogene Proteins/pharmacology; RNA, Messenger/genetics; RNA, Messenger/metabolism; Receptor Protein-Tyrosine Kinases/antagonists & inhibitors; Receptor Protein-Tyrosine Kinases/metabolism; Receptor Protein-Tyrosine Kinases/pharmacology; Receptors, Growth Factor/agonists; Receptors, Growth Factor/antagonists & inhibitors; Receptors, Growth Factor/metabolism; Receptors, Vascular Endothelial Growth Factor; Reverse Transcriptase Polymerase Chain Reaction; Solubility; Transduction, Genetic; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-1; Vascular Endothelial Growth Factors