Cooperative signaling for angiogenesis and neovascularization by VEGF and HGF following islet transplantation.
BACKGROUND
Delayed angiogenesis remains a significant challenge to the survival of transplanted islets. In this study, using a murine model of subcutaneous islet transplantation with matrigel basement membrane matrix, we determined the role of the proangiogenic growth factors in enhancing the islet engraftment.


METHODS
BALB/c islets were transplanted subcutaneously in growth factor reduced (GFR) or growth factor supplemented (GFS) matrigel into diabetic severe combined immunodeficient mice. GFS matrigel was prepared by supplementing GFR with proangiogenic factors, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). The functioning grafts were harvested at 15 days and vessel formation was analyzed histopathologically.


RESULTS
Our results demonstrate that suboptimal (250) islet equivalents in GFS-VEGF+HGF were able to restore normoglycemia, whereas those transplanted in GFR failed to reverse diabetes. Histopathology of the GFS-VEGF+HGF graft revealed 12±3 blood vessels per field, whereas GFR, GFS-VEGF, and GFS-HGF grafts had only 3±1, 6±2, and 4±1 blood vessels, respectively. Insulin staining demonstrated increased number of islets in matrigel supplemented with VEGF and HGF. Protein and mRNA analysis demonstrated enhanced intercellular adhesion molecule and vascular cell adhesion molecule within the islets when supplemented with both VEGF+HGF suggesting stable blood vessel formation. Transcription factors focal adhesion kinase phosphorylation and extracellular signal-regulated kinase1/2 phosphorylation were also increased (8-fold and 4.6-fold, respectively) when both the growth factors were present. There was weak expression of transcription factors when VEGF or HGF were supplemented alone.


CONCLUSIONS
We conclude that proangiogenic growth factors, VEGF and HGF, synergistically enhance angiogenesis after islet transplantation leading to stable engraftment.
Golocheikine
Anjali
A
Department of Surgery, Washington University School of Medicine, St. Louis, MO 63110, USA.
Tiriveedhi
Venkataswarup
V
Angaswamy
Nataraju
N
Benshoff
Nicholas
N
Sabarinathan
Ramachandran
R
Mohanakumar
Thalachallour
T
D000818:Animals; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D003094:Collagen; D004338:Drug Combinations; D017228:Hepatocyte Growth Factor / Q000494:pharmacology* / Q000627:therapeutic use; D007003:Hypoglycemia / Q000517:prevention & control; D007328:Insulin / Q000378:metabolism; D016381:Islets of Langerhans Transplantation / Q000379:methods* / Q000502:physiology*; D007797:Laminin; D051379:Mice; D008807:Mice, Inbred BALB C; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology*; D011509:Proteoglycans; D016511:Severe Combined Immunodeficiency / Q000601:surgery*; D015398:Signal Transduction / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology* / Q000627:therapeutic use
D001786:Blood Glucose; D004338:Drug Combinations; D007328:Insulin; D007797:Laminin; D011509:Proteoglycans; D042461:Vascular Endothelial Growth Factor A; C059485:matrigel; D017228:Hepatocyte Growth Factor; D003094:Collagen