Poster Presentation The International Congress of Neuroendocrinology 2014

Increases in cyclin D1 expression and in cell proliferation within omasal epithelium are regulated by systemic EGF in goats fed on a peanut straw diet (#194)

Zanming Shen 1 , Huaibao Zhao 1 , Xiaojuan Zou 1 , Zhiying Wang 1 , Zhinan HUang 1
  1. College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu, China

We have tested the hypothesis that, in goats, dietary alterations of omasal epithelium weight is mediated by serum epidermal growth factor (EGF) via the regulation of the cell cycle and proliferation. The goats were fed with peanut straw only (PS, n = 9) or PS supplemented with 400 g/d concentrate (PSC, n = 9) for 42 d. In the PS group, the relative weight of the omasal epithelium and its RNA:protein ratio were higher (p<0.05), but the protein:DNA ratio was lower (p<0.05) than those in the PSC group. Flow cytometry revealed that, in the PS group compared with the PSC group, the omasal cell proportions were greater (p<0.05) in S- and G2/M-phase but smaller (p<0.05) in the G0/G1-phase and were accompanied by the enhanced expression of cyclin D1 and CDK4 (p<0.05). These data were consistent with our morphological observations that, in the PS compared with the PSC group, cell density increased in the stratum spinosum (SS) plus stratum granulosum (SG) (p<0.05) and stratum basale (p<0.05), and that the strata layer number was higher (p<0.05) in the SS plus SG. In the PS group, the serum concentration of EGF increased 3 h after feeding (p<0.05), and EGF receptor (EGFR) mRNA in the omasal epithelium increased to a greater extent than that in the PSC group (p<0.05). In vitro, EGF (60 ng/mL) stimulated [3H] thymidine incorporation into omasal epithelial cells (p<0.05) and increased cyclin D1 expression (p<0.05). AG1478 (10 μM), an EGFR-specific inhibitor, inhibited EGF-stimulated cyclin D1 expression (p<0.05), but not CDK4. Thus, the omasal epithelial proliferation induced by the PS diet was caused by the over-expression of cyclin D1, which is mediated by a diet-dependent increase of serum EGF binding to EGFR in the omasal epithelium of goats.