FP39-2 Pituitary vascular remodeling: role of vascular endothelial growth factor (VEGF) in the pituitary control of seasonal breeding

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: FP39-Pituitary
Basic
Monday, June 17, 2013: 10:45 AM-11:15 AM
Presentation Start Time: 10:50 AM
Room 133 (Moscone Center)

Poster Board MON-115
Jennifer Castle-Miller*1, David Bates2 and Domingo Tortonese2
1University of Bristol, Bristol, United Kingdom, 2University of Bristol
Three functionally distinct regions of the ovine pituitary gland, the pars tuberalis (PT), pars distalis (PD) and infundibulum, intercommunicate with one another via an elegant vascular arrangement, hypothesized to be regulated by the local production of vascular endothelial growth factor (VEGF), a potent modulator of angiogenesis and vascular permeability. Vascular loops arising from the PT, where cells expressing melatonin receptors (MT1-R) are located, traverse to the infundibulum, an area encompassing glial cells and endothelium in close proximity, before descending towards the PD as long portal vessels. We hypothesized that the functional remodeling of this microvasculature is under seasonal regulation and may underlie the control of temporal changes in fertility. Pituitary glands from adult ewes were collected during the breeding season (BS; n=5) and non-breeding season (NBS; n=5).  The expression of pro- (VEGFxxx) and anti- (VEGFxxxb) angiogenic isoforms was revealed in PT cells co-expressing MT1-R, endothelial cells of the vascular loops, and both glial and endothelial cells of the infundibulum. Seasonal variation in VEGF isoform expression was observed in the PD, with significantly higher content of VEGFxxxb during the BS (p<0.01) and an increase in the expression of VEGFxxx (p<0.01) during the NBS. In support of these findings, total cell proliferation and endothelial cell proliferation were both significantly increased in the PD during the NBS (p<0.01), conjectured to result from the increased expression of pro-angiogenic isoforms at this time. In contrast, no such seasonal changes of VEGF expression or cell proliferation were detected in the PT (p>0.05). The expression of S-100, a marker of folliculo-stellate cells known to produce VEGF, was significantly increased during the NBS in the PD (p<0.01), and the expression of VEGF-receptors was identified in clustered endocrine cells in the same region. Seasonal alterations to the intrinsic morphology of the vascular loops of the infundibulum were also identified. The number and area of the these loops were significantly increased during the NBS (p<0.05). However, no seasonal changes to length or endothelial cell proliferation were established (p<0.05). These findings support a role of VEGF-mediated pituitary vascular remodelling in the mechanisms underlying the control of seasonal breeding.

 

Nothing to Disclose: JC, DB, DT

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