MOLECULAR PHYSIOLOGY AND BIOPHYSICS
The Role of Vascular Endothelial Growth Factor-A (VEGF-A) in Pancreatic Islet Function
in Adults
JEANNELLE A. KANTZ
Thesis under the direction of Professor Dr. Alvin Powers
Pancreatic islets are highly vascularized and this is important in insulin secretion
in response to nutrients like glucose. The purpose of this research was to investigate
the importance of vascular endothelial growth factor-A (VEGF-A) in adult islet function as
well as the function and morphology of intraislet vasculature. To accomplish this I used
a tamoxifen-inducible version of the Cre-loxP system (CreER). Two CreER transgenic
lines, (RIP-CreER or Pdx1PB-CreER) allowed for β-cell or islet-specific inactivation,
respectively, of VEGF-A following tamoxifen administration. RIP-CreER (Rat Insulin
Promoter) is expressed in β-cells of the islet while Pdx1PB-CreER is expressed in all islet
cell types. Cre-expressing mice were bred with Rosa26R (R26R) and Z/AP reporter
mice in order to test (A) the administration method of tamoxifen and (B) the
recombination efficiency. During these characterization studies we observed Cre
recombination in the absence of tamoxifen treatment in islets of RIP-CreER;R26R mice,
but not RIP-CreER;Z/AP mice. We found that Cre expression in RIP-CreER;R26R islets
was ~ 4X higher than Cre expression observed in Pdx1PB-CreER;R26R. These findings
indicate that Cre-mediated recombination of loxP sites depends both on the robustness
of the promoter driving CreER expression and the susceptibility of the targeted allele to
the Cre-mediated recombination.
Based on these findings, we crossed Pdx1PB-CreER transgenic mice with VEGFfl/fl
mice and measured the expression of VEGF-A in islets and the effects of VEGF-A
reduction on islet function and intraislet vasculature. We found that administration of
Tamoxifen effectively reduced VEGF-A levels in Pdx1PB-CreER; VEGFfl/fl mice. This
reduction in islet VEGF-A expression reduced islet vasculature, and transiently impaired
islet function.
These findings are particularly important for experiments utilizing inducible
systems. The results from our VEGF-A inactivation studies suggest that VEGF-A plays
a role in the maintenance of intra-islet vasculature in adults, and that reductions in islet
vascularization impact islet function.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-12042009-090812 |
| Date | 07 December 2009 |
| Creators | Kantz, Jeannelle A. |
| Contributors | Owen P. McGuinness, Maureen Gannon |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-12042009-090812/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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