Therapeutic targeting of the stem cell niche in experimental hindlimb ischemia.
BACKGROUND
The custom microenvironment 'vascular niche' is a potential therapeutic target for several pathophysiological conditions. Osteoblasts regulate the hematopoietic stem cell niche, and activation of the parathyroid hormone (PTH) receptor can increase the number of cells mobilized into the bloodstream.


METHODS
C57Bl/6 mice were randomly assigned treatment with granulocyte-colony stimulating factor (G-CSF), PTH, G-CSF plus PTH or saline. All mice underwent hindlimb ischemia. Blood flow was measured by laser Doppler imaging. Indices of capillary activity were determined by electron microscopy in muscle tissue. CD34(+) and Ki67(+) cells were detected and evaluated by immunofluorescence, apoptosis by TUNEL, surface antigen and endothelial progenitor cells by fluorescence-activated cell sorting analysis, and vascular endothelial growth factor-164 and angiopoietin-1 expression by reverse-transcriptase polymerase chain reaction. Frozen bone marrow sections were stained for antigen-specific B cells and fibronectin and analyzed by confocal laser scanning microscopy.


RESULTS
Following mobilization induced by G-CSF treatment, mice also treated with PTH showed increases in blood flow, capillary density, nitrite/nitrate release, angiogenic factors and circulating progenitor cells, as well as reduced apoptosis, fibrosis, oxidative stress and inflammation in ischemic muscles. Furthermore, hematopoietic antigen-specific B cells in the bone marrow were also increased by G-CSF alone and in combination with PTH.


CONCLUSIONS
PTH might increase the efficiency of hematopoietic stem-cell-based therapy in a recognized model of peripheral ischemia. Our translational experimental therapeutic targeting of the vascular niche points to novel clinical targets for the hematopoietic stem-cell treatment of ischemic vascular diseases.
Napoli
Claudio
C
Department of General Pathology, 1st School of Medicine, II University of Naples, Naples, Italy. claudio.napoli@unina2.it
William-Ignarro
Sharon
S
Byrns
Russell
R
Balestrieri
Maria Luisa
ML
Crimi
Ettore
E
Farzati
Bartolomeo
B
Mancini
Francesco P
FP
de Nigris
Filomena
F
Matarazzo
Angelo
A
D'Amora
Maurizio
M
Abbondanza
Ciro
C
Fiorito
Carmela
C
Giovane
Alfonso
A
Florio
Anna
A
Varricchio
Ettore
E
Palagiano
Antonio
A
Minucci
Pellegrino Biagio
PB
Tecce
Mario Felice
MF
Giordano
Antonio
A
Pavan
Antonio
A
Ignarro
Louis J
LJ
D042683:Angiopoietin-1 / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001783:Blood Flow Velocity / Q000187:drug effects; D002196:Capillaries / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects*; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination; D005355:Fibrosis; D000069585:Filgrastim; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D019650:Hematopoietic Stem Cell Mobilization / Q000379:methods*; D006412:Hematopoietic Stem Cells / Q000187:drug effects* / Q000473:pathology; D006614:Hindlimb; D006801:Humans; D007249:Inflammation / Q000473:pathology / Q000517:prevention & control; D007511:Ischemia / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000098:blood supply / Q000187:drug effects* / Q000473:pathology; D018919:Neovascularization, Physiologic / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins; D012039:Regional Blood Flow / Q000187:drug effects; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
D042683:Angiopoietin-1; C467628:Angpt1 protein, mouse; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D012333:RNA, Messenger; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D016179:Granulocyte Colony-Stimulating Factor; D000069585:Filgrastim