Hypoxia induces vascular endothelial growth factor gene and protein expression in cultured rat islet cells.

The formation of new microvasculature by capillary sprouting at the site of islet transplantation is crucial for the long-term survival and function of the graft. Vascular endothelial growth factor (VEGF), an endothelial cell-specific mitogen with potent angiogenic and vascular permeability-inducing properties, may be a key factor in modulating the revascularization of islets after transplantation. In this study, we examined the gene expression of VEGF mRNA in three tumor cell lines and in isolated whole and dispersed rat islets in vitro by Northern blot hybridization in normoxic (5% CO2, 95% humidified air) and hypoxic (1% O2, 5% CO2, 94% N2) culture conditions. Increased expression of VEGF mRNA was observed in beta-TC3, RAW 264.7, and IC-21 tumor cell lines when subjected to hypoxia. With isolated whole islets in normoxic culture, a threefold increase in VEGF mRNA (P < 0.001) was seen at 48 h as compared with freshly isolated islets. This response was similar to the 3.8-fold increase observed with islets subjected to hypoxia. Dispersed rat islet cell clusters cultured on Matrigel for 24 h under hypoxic conditions showed a 3.4-fold increase (P < 0.01) in VEGF mRNA compared with those cultured in normoxia. This correlated with increased VEGF secretion as determined by enzyme-linked immunosorbent assay. Immunohistochemical studies revealed the presence of increased expression of VEGF protein near the center of islets after 24 h of normoxic culture. Islet cell clusters on Matrigel showed intense cellular localization of VEGF in both beta-cells and non-beta-cells. These findings suggest that rat islet cells, when subjected to hypoxia during the first few days after transplantation, may act as a major source of VEGF, thereby initiating revascularization and maintaining the vascular permeability of the grafted islets.

[1]  Hidehiro Ishii,et al.  Vascular Endothelial Growth Factor–Induced Retinal Permeability Is Mediated by Protein Kinase C In Vivo and Suppressed by an Orally Effective β-Isoform–Selective Inhibitor , 1997, Diabetes.

[2]  S. Bonner-Weir,et al.  Vulnerability of Islets in the Immediate Posttransplantation Period: Dynamic Changes in Structure and Function , 1996, Diabetes.

[3]  E. Samols,et al.  Hormone secretion from transplanted islets is dependent upon changes in islet revascularization and islet architecture. , 1995, Transplantation proceedings.

[4]  D. Mukhopadhyay,et al.  Hypoxic induction of human vascular endothelial growth factor expression through c-Src activation , 1995, Nature.

[5]  Bruce A. Yankner,et al.  Pancreatic islet cell toxicity of amylin associated with type-2 diabetes mellitus , 1994, Nature.

[6]  A. Ullrich,et al.  High affinity VEGF binding and developmental expression suggest Flk-1 as a major regulator of vasculogenesis and angiogenesis , 1993, Cell.

[7]  C. Colton,et al.  Effect of Hypoxia on Insulin Secretion by Isolated Rat and Canine Islets of Langerhans , 1993, Diabetes.

[8]  N. Ferrara,et al.  Molecular and biological properties of the vascular endothelial growth factor family of proteins. , 1992, Endocrine reviews.

[9]  Harold E. Dvorak,et al.  Distribution of vascular permeability factor (vascular endothelial growth factor) in tumors: concentration in tumor blood vessels , 1991, The Journal of experimental medicine.

[10]  E. Samols,et al.  The induction of capillary bed development by endothelial cell growth factor before islet transplantation may prevent islet ischemia. , 1990, Transplantation proceedings.

[11]  S. Bonner-Weir,et al.  Islets of Langerhans: the puzzle of intraislet interactions and their relevance to diabetes. , 1990, The Journal of clinical investigation.

[12]  G. Conn,et al.  Purification of a glycoprotein vascular endothelial cell mitogen from a rat glioma-derived cell line. , 1990, Proceedings of the National Academy of Sciences of the United States of America.

[13]  D. Connolly,et al.  Tumor vascular permeability factor stimulates endothelial cell growth and angiogenesis. , 1989, The Journal of clinical investigation.

[14]  N. Ferrara,et al.  Pituitary follicular cells secrete a novel heparin-binding growth factor specific for vascular endothelial cells. , 1989, Biochemical and biophysical research communications.

[15]  H. Dvorak,et al.  A highly conserved vascular permeability factor secreted by a variety of human and rodent tumor cell lines. , 1986, Cancer research.

[16]  N. Lifson,et al.  Relation between blood flow and morphology in islet organ of rat pancreas. , 1985, The American journal of physiology.

[17]  P. Ralph,et al.  Antibody-dependent killing of erythrocyte and tumor targets by macrophage-related cell lines: enhancement by PPD and LPS. , 1977, Journal of immunology.

[18]  V. Defendi,et al.  INFECTION AND TRANSFORMATION OF MOUSE PERITONEAL MACROPHAGES BY SIMIAN VIRUS 40 , 1971, Journal of Experimental Medicine.