CD34+ cells home, proliferate, and participate in capillary formation, and in combination with CD34- cells enhance tube formation in a 3-dimensional matrix.
OBJECTIVE
Emerging evidence suggests that human blood contains bone marrow (BM)-derived endothelial progenitor cells that contribute to postnatal neovascularization. Clinical trials demonstrated that administration of BM-cells can enhance neovascularization. Most studies, however, used crude cell populations. Identifying the role of different cell populations is important for developing improved cellular therapies.


RESULTS
Effects of the hematopoietic stem cell-containing CD34+ cell population on migration, proliferation, differentiation, stimulation of, and participation in capillary-like tubule formation were assessed in an in vitro 3-dimensional matrix model using human microvascular endothelial cells. During movement over the endothelial monolayer, CD34+ cells remained stuck at sites of capillary tube formation and time- and dose-dependently formed cell clusters. Immunohistochemistry confirmed homing and proliferation of CD34+ cells in and around capillary sprouts. CD34+ cells were transduced with the LNGFR marker gene to allow tracing. LNGFR gene-transduced CD34+ cells integrated in the tubular structures and stained positive for CD31 and UEA-1. CD34+ cells alone stimulated neovascularization by 17%. Coculture with CD34- cells led to 68% enhancement of neovascularization, whereas CD34- cells displayed a variable response by themselves. Cell-cell contact between CD34+ and CD34- cells facilitated endothelial differentiation of CD34+ cells.


CONCLUSIONS
Our data suggest that administration of CD34+-enriched cell populations may significantly improve neovascularization and point at an important supportive role for (endogenous or exogenous) CD34- cells.
Rookmaaker
Maarten B
MB
Department of Vascular Medicine, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
Verhaar
Marianne C
MC
Loomans
Cindy J M
CJ
Verloop
Robert
R
Peters
Erna
E
Westerweel
Peter E
PE
Murohara
Toyoaki
T
Staal
Frank J T
FJ
van Zonneveld
Anton Jan
AJ
Koolwijk
Pieter
P
Rabelink
Ton J
TJ
van Hinsbergh
Victor W M
VW
D018952:Antigens, CD34 / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002196:Capillaries / Q000166:cytology*; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D002469:Cell Separation; D002478:Cells, Cultured; D018920:Coculture Techniques; D004730:Endothelium, Vascular / Q000166:cytology*; D005312:Fetal Blood / Q000166:cytology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D018919:Neovascularization, Physiologic / Q000502:physiology*
D018952:Antigens, CD34; D015415:Biomarkers