Identification of the hemangioblast in postnatal life.
Postnatal CD34(+) cells expressing vascular endothelial growth factor receptor 2 (KDR) generate hematopoietic or endothelial progeny in different in vitro and in vivo assays. Hypothetically, CD34(+)KDR(+) cells may comprise hemangioblasts bipotent for both lineages. This hypothesis is consistent with 2 series of experiments. In the first series, in clonogenic culture permissive for hematopoietic and endothelial cell growth, CD34(+)KDR(+) cells generate large hemato-endothelial (Hem-End) colonies (5% of seeded cells), whereas CD34(+)KDR(-) cells do not. Limiting-dilution analysis indicates that Hem-End colonies are clonally generated by single hemangioblasts. Sibling cells generated by a hemangioblast, replated in unicellular culture, produce either hematopoietic or Hem-End colonies, depending on the specific culture conditions. Identification of endothelial cells was based on the expression of VE-cadherin and endothelial markers and with lack of CD45 and hematopoietic molecules, as evaluated by immunofluorescence, immunocytochemistry, and reverse transcription-polymerase chain reaction. Furthermore, endothelial cells were functionally identified using low-density lipoprotein (LDL) uptake and tube-formation assays. In the second series, to evaluate the self-renewal capacity of hemangioblasts, single CD34(+)KDR(+) cells were grown in 3-month extended long-term culture (ELTC) through 3 serial culture rounds-that is, blast cells generated in unicellular ELTC were reseeded for a subsequent round of unicellular ELTC. After 9 months, 10% blasts from tertiary ELTC functioned as hemangioblasts and generated macroscopic Hem-End colonies in clonogenic culture. These studies identified postnatal hemangioblasts in a CD34(+)KDR(+) cell subset, endowed with long-term proliferative potential and bilineage differentiation capacity. Although exceedingly rare, hemangioblasts may represent the lifetime source/reservoir for primitive hematopoietic and endothelial progenitors.
Pelosi
Elvira
E
Kimmel Cancer Center, Room 609, Thomas Jefferson University, 233 S. 10th Street, Philadelphia, PA 19107-5541, USA.
Valtieri
Mauro
M
Coppola
Simona
S
Botta
Rosanna
R
Gabbianelli
Marco
M
Lulli
Valentina
V
Marziali
Giovanna
G
Masella
Barbara
B
Müller
Robert
R
Sgadari
Cecilia
C
Testa
Ugo
U
Bonanno
Giuseppina
G
Peschle
Cesare
C
D000328:Adult; D000367:Age Factors; D015703:Antigens, CD; D018952:Antigens, CD34 / Q000032:analysis*; D000943:Antigens, Differentiation / Q000032:analysis; D001854:Bone Marrow Cells / Q000145:classification; D015820:Cadherins / Q000032:analysis*; D018929:Cell Culture Techniques / Q000379:methods; D002455:Cell Division; D019070:Cell Lineage; D002478:Cells, Cultured / Q000166:cytology; D003114:Colony-Forming Units Assay; D016895:Culture Media, Serum-Free; D004730:Endothelium, Vascular / Q000166:cytology*; D005312:Fetal Blood / Q000166:cytology; D006801:Humans; D007231:Infant, Newborn; D017493:Leukocyte Common Antigens / Q000032:analysis; D008077:Lipoproteins, LDL / Q000378:metabolism; D013234:Stem Cells / Q000737:chemistry / Q000145:classification*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000032:analysis*; D000099152:Cadherin 5
D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D015820:Cadherins; D016895:Culture Media, Serum-Free; D017493:Leukocyte Common Antigens; D008077:Lipoproteins, LDL; D040301:Vascular Endothelial Growth Factor Receptor-2; D000099152:Cadherin 5