Midkine acts as proangiogenic cytokine in hypoxia-induced angiogenesis.
The cytokine midkine (MK) promotes tumor growth mainly by inducing angiogenesis. Here, we identified the source of MK in the vascular system under hypoxic conditions and demonstrated the relevance of MK during ischemia of normal tissue. Hypoxia increased MK protein expression in human polymorphonuclear neutrophils (PMN), monocytes, and human umbilical vein endothelial cells (HUVEC) compared with normoxia. Immunoelectron microscopy showed elevated cell surface expression of MK in PMN and monocytes during hypoxia. However, only HUVEC released significant amounts of soluble MK during hypoxia compared with normoxia (301 ± 81 pg/ml vs. 158 ± 45 pg/ml; P < 0.05). Exogenous MK induced neovascularization in a chorioallantoic membrane (CAM) assay compared with negative control as measured by counting the number of branching points per visual field (1,074 ± 54 vs. 211 ± 70; P < 0.05). In a hind limb ischemia model, the angiogenic response was almost completely absent in MK-deficient mice, whereas control animals showed a profound angiogenic response measured as proliferating endothelial cells per visual field (45 ± 30 vs. 169 ± 34; P < 0.01). These unanticipated results identified endothelial cells as the source of soluble MK in the vascular system during hypoxia and defined MK as a pivotal player of angiogenesis during ischemia in nonmalignant tissue.
Walter Brendel Centre of Experimental Medicine, Ludwig Maximilians University, Munich, Germany.
Ludwig T
LT
Weckbach
Leopold
L
Groesser
Julia
J
Borgolte
Judith-Irina
JI
Pagel
Frank
F
Pogoda
Jürgen
J
Schymeinsky
Josef
J
Müller-Höcker
Mehdi
M
Shakibaei
Takashi
T
Muramatsu
Elisabeth
E
Deindl
Barbara
B
Walzog
D042501:Angiogenic Proteins / Q000008:administration & dosage / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002478:Cells, Cultured; D002642:Chick Embryo; D049033:Chorioallantoic Membrane / Q000098:blood supply*; D016207:Cytokines / Q000008:administration & dosage / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D006614:Hindlimb; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D007511:Ischemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016253:Microscopy, Immunoelectron; D000078792:Midkine; D009000:Monocytes / Q000378:metabolism; D018482:Muscle, Skeletal / Q000098:blood supply*; D018919:Neovascularization, Physiologic; D009414:Nerve Growth Factors / Q000008:administration & dosage / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000008:administration & dosage
D042501:Angiogenic Proteins; D016207:Cytokines; C066254:MDK protein, human; D009414:Nerve Growth Factors; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D000078792:Midkine